US2366332A - Heat exchange system - Google Patents

Description

Jan. 2, 1945. E, P HARRISON ETAL H 2,366,332 HEAT EXCHANGE SYSTEM Filed June 12. 1939 ORV/LLE A HUNT INVENTORS ATTORNEY Patented Jan. 2, 1945 HEAT EXCHANGE SYSTEM Elmer Paul .Harrison and Orville A. Hunt, Oklahoma City, Okla; said Hunt assignor tosaid Harrison Application June 12, 1939, Serial No. 278,668

53 Claims.

This invention relates to a system employing steam substantially above atmospheric pressure as distinguished from a vacuum system, and using steam of a quality such that the major portion of the heat to be used for heat processing must be derived from the latent heat of steam rather than its sensible heat. More particularly, the invention relates to a heat exchange system in which the heat from live steam is transferred through the walls of steam chests, and the heated wall surfaces are used for drying wet clothing, wet paper rolls, and the like, in laundries, factories, mills and like places, as well as to a particular method of handling and utilizing the steam in such systems. For purposes of clarity the invention has been illustrated for use in connection with a laundry plant, although it may be used in paper plants and the like.

Such a system generally includes a boiler or steam generator, a boiler feed water heater tank, a pump for transferring the water from the feed water heater tank into the boiler, a make-up or reserve water supply of preheated water, various pieces of steam using heat exchangers or heat exchange apparatus each of which includes one or more steam chests, and, in the case of a laundry, a water softener or distiller, and a reserve tank of cold soft or distilled water.

All such systems in general use today in laundries, in paper mills, and in various other plants of this type prevent the circulation of steam through the various drying apparatus by means of steam traps or other flow-blocking obstacles connected to the outlets of said apparatus or in the return line on the low pressure side of the system, which traps collect condensate from the various steam chests and deliver it at periodic intervals into a pipe which carries the condensate back to the boiler feed water tank, to the makeup water tank or which carries it to some other point for heat utilization. The use of steam traps is the only known and used method of utilizing the otherwise wasted heat from the condensate at the present time. Those familiar with the art are aware that condensate which forms on the inside wall surfaces of steam chests has always very materially affected the efficiency of the heat transference through the walls of the chests. Also, air and non-condensable gases collect in pockets inside the steam chests of such systems and very materially obstruct this heat transference. The steam traps which are in general use in such systems over the United States today are not so constructed, and cannot be, so constructed, as to rid the chests of air and noncondensable gases, or to efficiently clear the interior wall surfaces of the chests of condensate. The condensate forms in a thin layer over the interior wall surfaces of the chests, (in thicker layers on those surfaces which are more nearly horizontal) and slowly drips or runs from these surfaces (mainly from the lowest or from the more nearly vertical portion of the walls) leaving a comparatively thick film of condensate over the more nearly horizontal portions of the interior wall surfaces of the chests, the adjacent exterior surfaces of which are the surfaces mainly used for drying purposes. The traps can take care of only that portion of the condensate which actually gravitates to the bottom of the chest and drains out through the drain pipe to the trap. Air and non-condensable gases enter the chests with the 'steam because of failure to remove both from the make-up water before this water actually enters the boiler. They also enter the chests through the steam traps. These gases collect in pockets in the upper portions of the chests and act as insulation to prevent the heat from the steam from passing through the walls of the chests. Since the traps and other flowblocking obstacles in the return line limit the flow of steam to that of replacement, flow due to condensation in the heat exchangers and up to the point of obstruction, there is insufficient steam velocity in the ordinary steam system to adequately scavenge the exchangers of the condensate which forms and collects on the heat exchange surfaces.

One important object of our invention is to achieve continual flow of steam with back pressure through the heat exchangers of such character as to continually blow the heat exchangers to rid them of air and non-condensible gases as well as condensate. In our preferred practice, restrictions are provided at the return sides of the heat exchangers of such size as to pass the condensate, gases and the entraining steam but small enough to create steep local pressure gradients to accentuate the fblowing action.

Another object is to provide an improved steam system comprising a method of maintaining a substantially continual flow of steam from a steam generator through apparatus while maintaining a back pressure within the apparatus and regulating the volume flow of steam through the system by controlling the exhaust of steam therefrom in accordance with the amount of water used by the system. As will hereinafter be apparent, the control of steam release in accordance with the amount of water used by the system may be regarded in five different aspects; namely, the total amount of water in use in the system at a given time, the steam release control acting in accord with changes in such total amount; the amount of new water added for use in the system, the control of steam release being functionally related to such addition; the rate at which condensate reaches the return end of the system relative to the rate at which water is fed to the steam generator, the rate of steam release varying with this differential; the rate at which water is fed to the steam generator as a reference or factor in controlling steam release; and, finally, the rate of condensate return, i. e., the rate at which condensate reaches the return end of the system as a reference or factor in such control.

A further object is to provide a substantially continual flow of steam through a system by regulating the flow of steam in accordance with the water used by the system to attain balanced operation, improved efficiency, and simplified operation.

A still further object is to provide a heat exchange system and method which affords a substantially continual flow of steam under pressure through the steam chests to continually remove the air, non-condensible gases, and condensate therefrom Still a further object is to provide a heat exchange system and method wherein the major portion of all oxygen, air, and other non-condensible gases are removed from the make-up water before its introduction into the boiler.

An additional object is to provide a heat exchange system and method wherein the major portion of such resisting films as the non-condensible gases and water are effectively removed from the condensing surface of the heat transfer apparatus by the moving force of the steam.

Additional objects are to provide a system of this class which will maintain the inside wall surfaces of the steam chests free from condensate which ordinarily collects thereon by utilizing the sweeping action of a substantially continual flow of steam therethrough, as opposed to the prevention of steam flow greater than replacement flow in the systems which are presently in use; which raises the potential rate of latent heat utilization, that is to say exposes the interior wall surfaces of the chests to a much greater number of latent heat units in a given period of time due to the removal of condensate and to the movement of the steam therealong at greater than the usual replacement flow; a system in which at least a portion of the heat from the steam which flows through the various chests, as well as a portion of the heat from the condensate which forms in the various chests, are both used to preheat the feed water before it is introduced into the boiler, thus reducing both waste of heat and of water; a system in; which the life of the boiler and of the various steam carrying headers and conduits is greatly lengthened due to the fact that the major portion of the air and non-condensable gases are removed from the feed Water befOIe it is introduced into the boiler, thus greatly reducing the formation of scale and encrustation on the inside of the boiler and the adjacent conduits; and a system which has proven, in actual use over an extended period of time, that it will increase heat transference through the walls of the various steam chests to such an extent that the output in heat processed material is raised greatly above the commonly accepted rated capacity of the heat exchange apparatus, with special reference to laundries and paper plants. In a laundry, for example, if an ordinary clothes mangle hooked into one of the presently used steam trap systems will efficiently dry clothing which passes through it at a speed of feet per minute, the same mangle will efficiently dry the same type clothing when run at a speed up to 70 feet per minute or higher provided the mangle is hooked into a system embodying the present invention. This means that a laundry using the present steam trap system can actually increase its production up to 75% or more simply by conversion to the new mode of steam utilization employed in this new system, which includes as an essential step the removal of the traps or other obstacles which block steam flow.

The present inventio then, not only improves the efliciency and economy of operation in plants in which it is installed either initially or for the purpose of conversion, but also utilizes the maximum percentage of the heat produced by the steam, a great percentage of which heat is lost in systems of present design. Preferably, the steam flow through the heat exchangers to achieve this end is made to vary in accordance with the heat load or heat demand applied to the exchangers, or more specifically, the amount of water used by the system; that is to say, an increase in heat load results in increased flow of steam through the exchangers.

The details in the installatio of a preferred form of our invention for use in connection with a laundry plant, together with other objects, will be better understood from the following description when read in connection with the accompanying drawing, which is chosen for illustrative 40 purposes only and in which,

Figure l is a diagrammatic side elevation of a laundry plant embodying a preferred form of the invention;

Figure 2 is a diagrammatic sectional view through the tanks which are illustrated in the upper portion of Figure 1;

Figure 3 is a detailed View with parts in section showing a means for removing air and noncondensable gases from the feed water before it reaches the boiler, which means is also included in Figure 1; and,

Figure 4 is a horizontal section Figure 3 on the line d l.

Like characters of reference designate like parts in all the figures.

Referring particularly to Figure 1, the numeral 5 designates as a whole a boiler from which steam is supplied to the various steam using devices of the plant. The plant illustrated includes a dry tumbler designated as a whole by the numeral 6, a fiat work ironer designated as a whole by the numeral 1, a press designated as a whole by the numeral 8, a drying form designated as a whole by the numeral 9, and a washer designated as a whole by the numeral it, the latter, however, using hot water rather than steam. The plant also includes' a water softener designated as a whole by the numeral ll, which receives its supply of water through a pipe I2 which is connected to a well, to the city water system, or other source of water. A malce-up water tank It receives its supply of soft water from a soft water storage tank it, which in turn receives its supply of water from the water softtaken through ener The make-up water tank is directly connected to the washer H] by means of a conduit I controlled by a valve IS. The make-up water tank is also connected by means of a conduit I! to a boiler feed water heater tank, designated as a whole by the numeral I8, the water being pumped from the bottom of this tank I 8 by a pump |9 into the boiler 5. For convenience, the water in the make-up water tank l3, the soft water tank M, and the feed water heater tank l8 will be considered conjointly as constituting a feed or make-up water supply. A steam header 20 carries steam from the boiler through conduits 2|, 22, 23 and 24 to the various steam using devices or heat exchanger apparatus 6, 8 and 9 respectively. Each of these steam using devices includes one or more steam chests, and the various steam chests are connected by means of conduits 25, 26, 21 and 28 to a drain pipe or exhaust conduit 29, on the return side of the system which slopes toward the feed water tank. The conduits 25 to 28 are connected to the lowest points in the varioussteam using devices to assure proper drainage and facilitate discharge of condensate. They are provided respectively with individual means of throttling the steam flow through the chests and into the conduit 29, thereby to produce the previously mentioned steep local pressure gradients to accentuate such discharge of condensate. In this particular instance, I have shown these individual throttling means as valves 30, 3|, 32 and 33, though any other suitable means of controlling or restricting the flow of steam through the various devices may be used. The steam and condensate conduit 29 is in open communication with a conduit 34 i which, as will be seen in Figure 2, passes into the hot water tank l3 preferably from the top, and extends well downward into the tank where its end is branched, and each branch carries an ordinary Penberthy water heater, or steam irijector 35. Any other type heater or steam jet may, of course, be used if preferable. As will be seen in both Figures 1 and 2, the flow of steam through the conduit 34 and out through the steam jets 35 is preferably controlled by an electrically actuated thermostatically controlled valve 36. Valves controlled and actuated in this manner are usual and it is not believed necessary to go into the details of the construction of the valve itself or of the mechanism for actuating it. The thermal means or thermostat for controlling the actuation of the valve is designated by the numeral 31 andis located inside the hot water tank |3 where it is cooled below its lower setting by new water added to the tank l2 and by the cooling effect of the atmosphere, and where it is subjected to the heat of the released steam and condensate to carry its temperature above its upper setting. Sufilce it to say that thermostats of the type we contemplate using are so sensitive that a temperature change of one degree in the water in the tank |3 will serve to partially open the valve and will hold it in this position until such time as the proper temperature is restored. This close setting of upper and lower limits renders the control of steam release inherently unstable and causes repeated actuation of the valve 36 at frequent intervals regardless of the load on'the system thereby setting up velocity responses in the heat exchangers above steam replacement flow and which tend to overlap in the exchangers due to the throttling effect of the valves 30 to 33, inclusive. A greater temperature change opens the valve wider. In other words the valve acts as a stage opening valve, and for use in this system is preferably set so that it is never completely closed, thus affording substantially continual flow of steam through the conduits 29 and 34.

The conduit 29 is also connected at 38 with a steam trap 39 which collects any condensate which gravitates or is blown into the conduit 29, and delivers this condensate through pipe 40 into the feed water heater tank I8. In addition, the heater tank, as stated before, receives its major source of water supply from the make-up water tank I3 through the conduit IT. The valve 4| in this conduit controls the flow of hot water to the feed water heater tank, while the valve 42 disposed in asteam conduit 43, controls the flow of steam from the conduit 34 through a jet or injector 44 into a short pipe 45 which conducts both steam and water into the feed water heater tank I8. The exhaust conduit 29 from which steam is released from the system by the valve 36 in the conduit 34 and the valve 42 in the conduit 43 constitutes part of a substantially clear channel of free or open communication that extends back from the valves through the heat exchangers to the steam source. Both the water valve 4| and the steam valve 42 are snap acting valves and are preferably controlled by a link 48, the slotted end 41 of which is connected by means of a pi 48 to the outer end of a float valve arm 49, the inner end of which carries a float 50. Both these valves, however, may be electrically actuated valves controlled by an automatic boiler Water level switch 86 (the details in the construction of which are not disclosed because such switches are old and well known) which as illustrated in Figure 1 closes an electric circuit and operates the pump when the water level in the boiler falls below a certain predetermined level.

With these valves 4| and 42 operated mechanically, as shown, when water is taken out of the feed water heater tank l8 and is forced into the boiler, the float 50 operates the arm 49 when the water reaches a predetermined level in the feed water heater tank, which arm in turn snaps open the two valves 4| and 42. Steam thus jets into the already heated water as it passes from the conduit i! into the conduit 45, and since the mixed steam and water passes out of the inner end of the conduit 45 through a plurality of chokes or spray jets 5|, a considerable pressure is created between the jets 5| and the injector 44. Since the heater tank I8 is open at its upper end, as shown in Figure 3, the pressure inside this tank is atmospheric pressure. The higher pressure and heat which is created within the conduit 45 causes the major portion of the hot water to either flash into steam or to be atomized as it issues from the chokes 5|. The flashe ing and atomization of this water within the interior of the heater tank rids the water of air, oxygen, and other non-condensable gases, and these gases, together with a certain amount of steam must pass through a condensor 52 before reaching the atmosphere. The water in the boiler feed water heater tank, then, contains neither air nor non-condensable gases to be passed through the pump, boiler, header 20, and into the chests of the various steam devices 6, 1, 8 and 9.

As stated before, the use of such deaerated water greatly reduced the cost of plant operation and maintenance. In order to thoroughly dearate any condensate which may form in the provided with an annular skirt 55, which serves to force overflow water to drip from its outer edge instead of running down the sides of the pan. The pan 53 is also provided with an upstanding concentric collar 56 which directly catches all condensate which drips from the condensor 52. The lower end of this collar 56 is serrated as indicated by the numeral 51 so as to permit the water which drips into the collar 56 to pass into the main body of the pan 53 from which 3 it drips into the tank l8 from the extreme outer rim of the annular skirt 55. The condensor 52 includes a coil 58, one end of which is in open communication with a soft water conduit 59 which directly connects the water softener with the soft water reserve tank H. The other end of the coil 58 is connected to a conduit 60 which is adapted to empty soft water directly into thetank 13. The flow through the coil 58 is controlled by a float valve 6| which is of usual construction and which is located in the upper end of the tank l3 at a higher level than the float valve 62 which controls theflow of cold soft water into the tank l3 from the reserve tank I. It will thus be seen that as the water level in the tank l3 drops, the valve 6| will open before the valve 62 opens. If only a small amount of water is used out of the tank I3 then this water will be replaced by soft water which first passes through the condensor 52, where it is preheated. If the volume of water used from the tank I 3 is large, then the valve 6! will open first and the valve 62 will open later, thus utilizing as much pre-warmed soft water as possible, and utilizing the heat from the steam and gases which pass through the condensor 52, which heat would otherwise be wasted. The pre-warmed water is, of course, below the normal temperature of the water in the tank I3. The flow of water from the water softener H into the tank I4 is controlled likewise by a float valve 53 which normally maintains the water in this tank at a predetermined level. A valve 64 is provided to determine the maximum volume of flow of water from the tank l4 into the tank l3. This valve 64 may be used as a means of regulating the volume flow of steam through the entire system. For instance, if a considerable amount of hot water is used periodically from the tank I 3, as is the case in a laundry plant, the valve 64 is regulated so that it allows water to flow from the tank M at such a rate as to approximately refill the tank l3 by about the time water is next drawn from the tank. This substantially continual flow of water into the tank l3 it causes the temperature of the water therein to remain at a point at.v which the thermostat 31 causes the steam valve 36 to be held at least partially open continually. Thus continual steam circulation through the various steam using devices is assured. It will be seen that with the valve 64 regulated as just described, it is not essential that the valve 36 be set mechanically so that it will never be allowed to completely close. Even if the valve 64 is not regulated so carefully as to cause a continual flow of steam through the conduits 29 and 34, the intermittent or continually pulsating flow therethrough is so nearly continuous as to produce the results sought and previously mentioned.

Continuing the example of a laundry plant in connection with our system, the washer, the hot water demand of which is to be considered as outside demand extraneous to the system per se, is usually shut down toward the latter part of the work day and this makes a very material change in the amount of hot water drawn from the tank l3. When this change i operation occurs, the valve 64 is regulated so as to allow a greatly reduced flow of water from the tank l4 into the tank l3, thus still maintaining a substantially continuous fiowof steam through the various steam using devices to obtain comparably effective results. It will be understood, then, that the quantity and the frequency of withdrawal of water from the tank I3 for general plant use as well as to feed the boiler is utilized to govern the substantially continuous flow of steam through the system. In addition, of course, the valves 30 to 33 inclusive may be used to limit the maximum permitted flow through the system.

The feed water heater tank I8 is provided with an overflow pipe 65 which openly communicates with the interior of the tank at a point just above the level of the points of entrance of the conduits and 45, and just below the bottom of the pan 53. This serves to keep the water level in the feed water heater tank below the lower edge of the skirt 55.

The described apparatus is quite flexible in that it may be constructed and adjusted for (iiiferent modes of operation within the scope of ourinvention. In all of the contemplated practices the basic concept is to achieve such velocity of steam flow as to remove condensate from the system and especially from the inner sur- 40 faces of heat exchange walls at such rate as to achieve substantially higher efiiciency and rate of heat transfer than has heretofore been achieved in conventional steam systems in laundries, and driers in general. To obtain the new level of heat transfer in a steam heating system it is our purpose to operate in a range of steam flow velocities that is not possible in a conventional system having traps to prevent free flow to and through the return side of the system. Heretofore traps have been regarded as necessary in steam plants of the type under consideration wherein a number of different heating devices are supplied from a, common boiler and the use of traps has prevented the attainment of the range of velocities employed in our apentraining condensate substantially as fast asthe condensate is formed, and preventing the accumulation of condensate on the heat transfer walls in any film of such thickness as to materially reduce the rate of heat transfer from the flowing steam to the outer surfaces of the heat transfer walls.

The high velocity of steam flow need not be strictly continuous since the results we seek may beattained with the velocity of steam flow varying either between different positive values for pulsatin continuous flow or between positive values and zero for pulsating intermittent fiow with periodic complete cessation of steam flow through the system as a whole. In any mode of operation, however, the average steam velocity over a period of time or the number of occurrences of flow at effective velocity over the period of time is such as to prevent such accumulation of condensate and such building up .of condensate films as will reduce the availability of the heat units carried by the steam.

In the light of the above, it should be understood that in the claims the use of the expression continual flow or the expression substantially continual flow should not be literally interpreted to mean that the flow of steam may not be temporarily halted through the closing of automatic valves or controls. Within the sense of the expressions there may be interruption in the fiow of steam. In other words, the term continual is to be construed as having either of two meanings given by Webster's New International Dictionary, the first meaning being occurrence without interruption and, the second meaning being occurrence at frequent intervals.

Thus, under either meaning of the term a steam condition prevails that provides sufficiently continuous pressure and movement to effectively remove non-condensable gases andwater from the condensing surfaces of the steam apparatus and to maintain the surfaces substantially free from noncondensable gases and any water film of material thickness whereby additional heat units reach such surfaces to increase the rate of heat transfer. Any steam condition, pressure, or flow that accomplishes this end should be construed to be within the terms and meaning of continual flow of steam.

A further feature of our invention is the fact that the attainment of the relatively high velocity of steam flow for'the above purposes also serves to entrain non-condensible gases in the system and thereby prevent not only the formation of gas pockets but also prevent the formation of layers or films of non-condensible gases or such gases mixed with steam vapor. gaseous films commonly form between the stream of steam and the moist heat transfer walls to act as a barrier or insulating layer to reduce the rate of heat fiow from the stream of steam through the heat transfer walls.

It is important to note that steam may flow in an unobstructed manner from the boiler to the steam valves 36 and 42 since the return pipe 29 and the branch pipes 34 and 43 afford what may be termed trapless channels. The steam trap 39 is not in the path of such flow but merely serves to take care of such condensate as may accumulate by drainage from the pipe 34. In effect, the trap 39 functions as a receiver to one side of the main return channel.

As pointed out above, one reason that high Such flow would at first thought seem to be so wasteful of steam as to more than offset advantages incidental to the increased velocity. A feature of our invention is that we obtain the'benefits of effective flow velocity by bleeding or releasing steam from the system on the return side thereof without prohibitive cost in lost heat units.

With respect to the conservation of steam in the attainment of our' purpose the present disclosure presents a number of concepts which may be employed singly or in combination in various practices of the invention. In general, our object is to provide some means or method for automatically controlling the release of steam. One of our concepts is to release steam substantially continuously but to vary the rate of con tinuous release in accord with the demand for heat imposed upon the system, i. e., in accord velocity of steam flow has not been attained in steam heating plants for processing as heretofore designed is the belief that flow-obstructing traps are indispensable for taking care of condensate on' the return side of a system having a plurality of heat exchangers in parallel. A further and equally effective reason is the fact that simply releasing steam from the return side of a system for the benefit of increased velocity with the rate at which condensate tends to form in the system. Another concept is to release the steam intermittently by employing a steam valve '36 that will reduce or completely out off steam flow when the thermostat bulb 31 is heated to a predetermined temperature. It is to be noted that regardless of the construction and adjustment of the valve 36 the second steam valve 42 permits steam flow therethrough only periodically. A third concept is that intermittent or pulsating flow may be tied in with demand so that the amount of steam released in an intermittent or pulsating manner will vary with changes in the heat demand imposed on the system.

In addition to achieving economy by controlling the rate of steam release, we have, in the preferred practice of our invention, the further concept of avoiding waste in heat units by employing the released steam for a useful purpose. In some practices the employment of the released steam is restricted to the feed water required by the heating system alone while in other practices,

of water required by the steam generator will' vary with the amount of heat drawn from the system and therefore steam released in accord with the amount of water consumed by the boiler will likewise vary with the system demand. A further concept is that the required responsive relationship between a steam release valve and the feed water supply may be achieved by employing a thermostatic valve responsive to temperature changes of the feed water. A third concept is that in this latter arrangement the feed water may be regarded as merely thermal responsive means that is heated whenever new water is required by the steam generator. A fourth concept is that of employing a thermostat for controlling steam release and setting the thermostat at a high temperature relative to the environment of the thermostat, a temperature that can be maintained only by releasing steam from the system, the reason for such an arrangement being that steam is continually released from the system regardless of demand. In practices of the invention under this last conp steam is released from the system or is released at an increased rate periodically in response to periodic feeding of water to the steam generator and in the intervals between feed water operation steam release is maintained independently of the heat load on the system by the tendency of the thermostat to cool below its relatively high setting.

For a complete understanding of our invention as adjusted for intermittent action at relatively high frequency, it is necessary to give some consideration to the aspect of inherent instability, the tendency of the system to behave as if it were inherently oscillatory.

When the system is adjusted for high frequency operation, it acts as if it were continually hunting or overshooting in restoring some state of balance or equilibrium. Thus a feature of our invention is the concept of designing a system to "hunt at some desired tempo as a method of attaining intermittent action at that tempo. The high temperature setting of the thermostat is per se a cause of inherent instability since the setting is higher than the temperature of the environment around the feed water supply and can be sustained only by periodic release of steam. Another cause 01 inherent instability appears to arise from effects appearing alternately at the opposite ends of the system. Thus, condensation of steam or the release of steam towards one end of the system causes flow of steam thereto which flow in turn creates a corresponding demand for new water by the boiler at the other end of the system. The feedin of new water to the boiler, however, involves the release of steam to again create demand at said one end of the system.

Upon closer analysis, it is found that the intermittent operation 01' the system, especially at hi h frequency, involves a chain of causes as follows: condensation in the system causes a drop in boiler pressure with a consequent tendency for the boiler to form more steam for replacement; the drop in liquid level in the boiler causes approximately a corresponding amount of water to be delivered from the tank l8 to the ing flow into the tank l3 causes responsive opening of the steam valve 38; the increased flow of .steam through the system resulting from the bleeding of steam from the system by the valves 36 and 42 causes a drop in pressure on the return side of the system to tend to bring about repetition of the chain of causes. In other words, there exists whatmay be called a closed chain of causes which, once set in operation, has a certain tendency to repeat itself regardless of the effect of loss of heat from the environment of the thermostat bulb.

In this approach to the invention, then, we find inherent intermittency of operation arising both from the thermostat setting and the closed chain of causes and upon such inherent intermittent action is imposed the demand of heat from the system, the demand or load desirably modifying the intermittent action for automatic regulation of the system.

There is reason to believe that lag factors in the chain of causes are important in causing repetition of the chain and in contributing to the character of the intermittent action. One lag factonior example, is the time required for the release of a quantity of steam from pipe 34 at lit the end of the system to become effective in corresponding drop of water level in the boiler 5 at the other end of the system. Another lag factor is the time required for the drop in water level to cause operation of the valve 36, that is to say the time required for the thermostat bulb 31 to b affected by the addition of new water to the tank 13 consequent to the drop in liquid level in the tank l8 which drop in liquid level is in turn consequent to drop in level in the boiler 5. After one cycle of causes is closed, lagging forces set in motion during the cycle are effective to tend to repeat the cycle. Thus, if the operation of the feed pump H) be considered the last step in the chain of causes, it. is apparent that after the feed pump stops, the lagging release of steam by the thermostatic valve is at least contributing to a growing demand for subsequent operation of the pump.

An important advantage of intermittent action is that the abrupt rises in velocity or the spurts of steam caused by opening of steam valves are highly effective in jarring droplets of condensate loose from heat exchanger surfaces and in sweepin away condensate films on heat exchanger surfaces. Another important advantage is the economy in periodically reducing or cutting off steam release.

The first consideration in economical use of steam is the amount of exhaust steam required to effectively preheat the feed water. A maximum of about fourteen per cent of exhaust steam is all that is required for heating the feed water of any system to 212 F. and since in the above described system condensate as well as steam is returned to the boiler, only about ten per cent of the generated steam may be required for feed water heating. Often a great deal more than ten per cent of the generated steam must be bled off to attain sufficient steam velocity in the system for the desired efficiency in heat transfer.

In some installations intermittent operation may be a desirable compromise between, on the one hand, conserving steam at too great cost in lowering of temperature of the heat exchange surfaces and, on the other hand, bleeding steam continuously to maintain effective velocity in the system at too great fuel cost. In explanation, let it be assumed that the efficiency of the heat exchangers in the system are considered as one hundred per cent in the absence of films of condensate on the heat exchange walls but dropping to only fifty per cent in the presence of films of given thickness. Let it be assumed further that a given high velocity of steam fiow will substantially remove such condensate film in a: seconds and that after cessation of flow the film will be restored progressively over a like period of a: seconds.

If steam is released for :1: seconds and is then cut off for 2:: seconds with efficiency at fifty per cent at the beginning of each cycle, the average efliciency of the system will be 66 (an average of for :1: seconds, an average of 75% for the next period of a: seconds, and 50% efficiency for the third period of x seconds). If x seconds of steam release alternates with :0 seconds of no steam release, the average efficiency will rise to 75%. If the intermittent action consists of 23: seconds of steam release alternating with .1". seconds of no steam release efilciency will climb to 83 Each of these successive levels of efiiciency involves stepping up the volume of steam bled from the system and an optimum aseassa ratio or at cast a compromise ratio between the periods of steam release and no release may be found somewhere in such a progressive series. In practice, a desirable mode of intermittent operation may be found in tabulating the fuel costs, labor costs and production for the diflerent modes of operation in the progressive series, the increased production and resulting drop in labor cost per unit of production being weighed against the increase in fuel cost with increase in the proportion of steam bled from the system.

It should be understood that throughout the specification and the appended claims, the expressions "intermittent release of steam and operation with intermittent release of steam and the like are intended to denote the release of steam at a varying rate, which may vary from some positive value to zero, or from some positive value to a lower value, such as the case when the valve does not completely close or because a by-pass is provided. This is not to be confused with the definition heretofore given for pulsating intermittent flow of steam in which it is contemplated that there will be a complete cessation of steam flow between pulsations, in contra-distinction to pulsating continuous flow of steam in which the rate of steam flow varies between different positive values.

While we have described and illustrated only one preferred form of the invention, it will be apparent to those skilled in the art that various modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims. For example, the simultaneous control of the valves 4| and 42 by the boiler water evel switch instead of by the float 50. as'illustrated.

We claim:

1. A heat exchange system comprising: steam using devices; a boiler connected for supplying steam thereto; a boiler feed water tank for supplying water to said boiler; a make-up water tank for supplying water to said feed water tank;

' a pipe system connected to said devices and to both of said tanks for carrying exhaust steam to each tank; thermostatic means responsive to temperature changes in one of said tanks for controlling the volume flow of exhaust steam from said pipe system into that tank; and means responsive to changes in the water level in the system is governed automatically both by the amount of water used during operation of the system and by the loss of heat units from the system, which results in a substantially continuous but varying volume flow of steam through the devices.

2. In operating steam using heat exchange apparatus in connection with a steam system including a steam generator for supplying steam heat thereto, the method which consists in maintaining a substantially continual flow of steam from the steam generator through the apparatus while maintainin a back pressure within the apparatus, and regulating the volume flow of steam through the apparatus by thermostatically controlling the exhaust of steam from the system after the steam has passed through the apparatus in accordance with the amount of water used by said system.

3. In operating drying apparatus in connection with a steam system includinga steam generator for supplying steam heat thereto, the method which consists in maintaining a substantially continual flow of steam from the steam generator through the drying apparatus while maintaining the pressure within the apparatus at a pressure higher than atmospheric pressure, utilizing a portion of the heat from the steam which passes through said apparatus to preheat feed water for the system, utilizing a portion of the heat from the steam which passes through the apparatus to deaerate the heated feed water before it reaches the boiler, and increasing the flow of steam through the apparatus with increase in the amount of water added to the system.

4. A heat exchange system comprising in combination, a steam using heat exchanger, a boiler or steam generator for supplying steam thereto. a boiler feed water tank, means for transferring water from the feed water tank to the boiler, an exhaust conduit for conducting exhaust steam and condensate from said heat exchanger into' said feed water tank, and means including a valve responsive to a predetermined drop in the water level in said feed water tank for at least partially opening said exhaust conduit to release steam and condensate therefrom within said tank.

5. A heat exchange system comprising in combination, a steam using heat exchanger, a boiler or steam generator for supplying steam thereto, a boiler feed water tank maintained at substantially atmospheric pressure, means for transferring water from the feed water tank to the boiler, an exhaust conduit for conducting exhaust steam and condensate from said heat exchanger to said feed water tank, means including a valve responsive to a predetermined drop in the water level in said feed water tank for at least partially opening said exhaust conduit to release steam and condensate from within said tank, and means for condensing and depositing in said tank at least a portion of the steam released therein.

6. In a steam circulating system, the combination comprising a boiler or steam generator, a plurality of steam using devices fed thereby, a boiler feed water tank, a pipe system for carrying exhaust steam and condensate from said steam using devices to said tank, a source of water for supplying additional water to said tank, jet means connected to said pipe system and said source of water supply for utilizing exhaust steam and condensate to heat additional water as it enters said tank from said source of supply; and means responsive to a drop in the Water level in said tank for controlling the passage of wa ter, steam, and condensate through said jet.

7. Boiler feed apparatus comprising a feed water heater tank vented to the atmosphere, a conduit for supplying water to said tank, a steam injector interposed in said conduit for heating and injecting water into space above the liquid level in said tank, means for controlling the flow of both water and steam through said conduit in accordance with changes in the liquid level in said tank, means for atomizing the heated water as it issues from said conduit into the upper interior of said tank, means for condensing steam in the upper end of said tank to prevent the escape of a major portion thereof to the atmosphere. and means for delivering water from said tank to a point of use.

8. In operating steam using heat exchange apparatus in connection with a steam system for supplying steam heat thereto, the method which consists in maintaining a substantially continual flow of steam from the steam generator through the apparatus while maintaining a back pressure within the apparatus, and regulating the volume flow of steam through the system by controlling the exhaust of steam therefrom in accordance with the amount of water used by the system.

9. In operating steam using heat exchange apparatus in connection with a steam system for supplying steam thereto, the method of continually furnishing the apparatus with'steam which comprises the steps of continually exhausting steam from the system, after it has passed through the apparatus, into an area having a pressure considerably lower than that maintained in the apparatus, and controlling the volume of steam thus exhausted at least in part by the rate at which condensate is being conveyed to said area from the apparatus.

10. A heat exchange system comprising, a

steam using device, a boiler or steam generator connected for supplying steam thereto at relatively high pressure, an exhaust steam pipe system in completely open communication with said steam generator through said steam using device, a valve controlling the release of steam from said exhaust steam pipe system into a pressure much lower than that maintained within the system by the generator, and means governing the operation oi said valve to produce a substantially continuous flow of steam from said generator through said device in accordance with the amount of water used by said system.

11. A heating apparatus utilizing primarily the latent heat of steam and having at least one heat exchanger, a steam generator connected with the supply side of said heat exchanger, means providing a supply of water to feed said generator, means providing a substantially clear channel from the low pressure side of said heat exchanger to said supply means to release the steam from the heat exchanger into said supply means at a rate which maintains a back pressure in the channel and produces a substantially continual flow of steam through the exchanger at a velocity substantially above the velocity of replacement fiow caused by steam condensation in the exchanger, and means to increase the velocity flow in said channel in response to increase in the heat load on the heat exchanger.

12. A heating apparatus having a steam generator, means to supply ,feed Water to said generator, heat exchange means providing heat transfer walls, means to deliver steam from said generator to said heat exchange means, means to continually release steam on the lowpressure I side of said heat exchange means in a pulsating manner, and means to modify the pulsating character of the steam flow through the apparatusj in accord with the amount of water used by the system thereby varying the velocity of steam flow through said heat exchange means in accord with demand for heat.

13. A heating apparatus having a steam generator, heat exchange means providing heat ,65 transfer walls, means for delivering steam from supply of water to satisfy the demands of a hot water consuming device, means for replenishing said supply of water as required, and means responsive to the temperature of said supply of water to control the rate of the steam release inversely as the temperature of the supply of water changes whereby both the heat demand'on the heat exchange means and the water demand of said consuming devices are factors in causing a substantially continuous flow of steam through the heat exchange means at a rate greater than steam replacement flow due to condensation in the heat exchange means and beyond.

14. A method of operating a steam system including means providing feed water for a steam generator in the system, said method comprising establishing a closed chain of causes in the system to promote velocity of flow therethrough for a high rate of heat transfer from the system, said chain of causes including evaporation of water in said steam generator causing replenishing flow of feed water to the steam generator, such flow of feed Water causing an increasing flow of steam through the system, and such increased flow of steam through the system causing evaporation of water in said steam generator to tend to repeat the chain.

15. A heating apparatus having at least one heat exchanger, a steam generator connected with the supply side of said heat exchanger, means providing a supply of water to feed said generator, means providing a substantially clear channel from the low pressure side of said heat exchanger to said supply means to release steam from said channel into the supply means, valve means to control the rate of steam release, and means to effect intermittent operation of said valve means to produce a substantially continual pulsating flow of steam through the apparatus, at a rate substantially above steam replacement flow due to condensation in the exchanger and beyond.

16. A heating system having a steam generator, at least one heat exchange means connected thereto, means to feed water to said steam generator as required by evaporation therein, and means to cause steam flow through the system in response to operation of said water feed means, and additional means for promoting steam fiow through the heat exchange means by continually releasing steam from the exhaust side thereof.

17. A combination for addition to an installed steam heat-exchange system for improving the efiiciency thereof comprising means to maintain asupply of feed water to be drawn upon as required for replenishing boiler water in the system, means including a return line to release steam and condensate from the low pressure side of said system to heat said feed Water and to promote flow through the system, means efiective to cause increased return flow in said return line in response to delivery of water from said feed water supp y, and thermostat means aifected by released steam to cause operation of said release means Whenever the thermostat means cools to a predetermined temperature.

18. A heating apparatus having a steam generator, means providing a supply of water to feed said generator, means to replenish said supply of water as required, heat exchange means providing heat transfer walls, means for delivering steam from said generator to said heat exchange means, means to release steam from the low pressure side of said heat exchange means ascaaea into said supply oi water in a manner to remove a substantial proportion of non-condensable gases from the supply water and at a rate to cause steam flow at a velocity to prevent any substantial accumulation in the heat exchange means of residua1 non-condensable gases, and means .to control the rate of steam release in response to variation in the demand for heat by said heat exchange means whereby the rate of steam flow varies in accord with the varying tendency of condensate to form on said walls with varying heat demand on the heat exchange means.

19. In a method for controlling the flow of steam through a steam system which includes a boiler, a steam using device having a heat exchange surface through which heat units are transferred from the steam to a material to be heated and/ or dried, and an exhaust conduit, the improvement which consists in exhausting steam through the exhaust conduit to move steam through the system at a velocity to entrain condensate at a sufficient rate to maintain a high level of heat transfer, and to prevent the formation of air pockets adjacent to the heatexchang surface, using the exhaust steam and entrained condensate for preheatin make-up water for the boiler and for flash boiling water being delivered to the boiler to remove non-condensible gases therefrom, and controlling the volume flow of steam per unit of time through the heat exchange device in accordance with the rate at which heat units are being absorbed from the steam through the heat exchange surface.

20. In operating steam heat exchange apparatus in connection with a steam system including a steam generator for supplying steam heat thereto, the method which consists in maintaining a substantially continual flow of steam from the steam generatorv through the apparatus while maintaining a back pressure within the apparatus, providing an exhaust conduit from the apparatus to convey steam and condensate therefrom, and regulating the volume flow of steam through the apparatus by exhausting steam from said conduit in accordance with the total amount of water contained within the system at a given time.

21. In operating steam heat exchange apparatus in connection with a steam system including a steam generator for supplying steam heat thereto, the method which consists in maintaining a substantially continual flow of steam from the steam generator through the apparatus while maintaining a back pressure within the apparatus, providing an exhaust conduit from the'apparatus to convey steam and condensate therefrom, adding water to the system in response to increases in heat load on the system, and increasing the volume flow of steam through the apparatus by exhausting steam from the conduit in response to increases in the rate at which new ator as another factor.

water is added to the system to accelerate the return of condensate from the apparatus.

22. In operating steam heat exchange apparatus in connection with a steam system including a steam generator for supplying steam heat thereto, the method which consists in maintaining a substantially continual flow of steam from the steam generator through the apparatus while maintaining a, back pressure within the apparatus, providing an exhaust conduit from the apparatus to convey steam or condensate therefrom, regulating the volume flow of steam through the apparatus by exhausting steam from said 23. In operating steam heat exchange apparatus in connection with a steam system including a steam generator for supplying steam heat thereto, the method which consists in maintaining a substantially continual flow of steam from the steam generator through the apparatus while maintaining a back pressure within the apparatus, providing an exhaust conduit from the apparatus to convey steam and condensate therefrom, and regulating the volume flow of steam through the apparatus by exhausting steam from said conduit in accordance with the rate at which water is being fed to the steam generator.

24. A method of operating a steam using system including a boiler and a heat exchanger consisting in providing a channel of open communication for continual steam passage from the boiler through the heat exchanger, releasing steam and condensate from said channel on the return side of the system to substantially atmospheric pressure to cause relatively high velocity through said channel with consequent relatively high rate of heat transfer in said exchanger, delivering feed water to'said boiler at a rate to meet whatever requirement for water vaporization the system may have, adding new water to said feed water, utilizing at least part of the released steam and condensate to feed said boiler,

and functionally relating both said release of l the generator and an exhaust conduit connected to the low pressure side of the exchanger, the combination therewith of a tank, valve means controlling steam release from the exhaust condurit, means for introducing condensate returned from the system into the tank, means for withdrawing water from the tank to feed the steam generator, and means responsive to the level of the water in the tank for introducing additional water into the tank, said last-named means also operating to actuate said valve means to release steam from the exhaust conduit, thereby increasing the flow of steam through the heat exchanger and speeding up the return of condensate from the system.

26. In operating a steam using apparatus in connection with a steam system including a steam generator for supplying heat thereto and a source of make-up water, the method which consists in providing an exhaust conduit from the apparatus to convey steam and condensate therefrom, feeding water to the steam generator as required, increasing the volume flow of steam through the apparatus by exhausting steam from said conduit in response to a predetermined decrease in the rate at which condensate is being conveyed through said conduit in relation to the rate at which water is being fed to the generator, continually exhausting steam from the conduit to maintain the volume flow of steam at said increased rate until the rate of condensate return relative to the rate of water being fed to the generator reaches a predetermined value, and concurrently with said exhausting of steam adding increments of water from said make-up water source to compensate for the condensate loss due to loss of steam from the system.

27. In a steam system, the combination of a heat exchanger, a steam generator for supplying steam to .the heat exchanger, a feed water tank having a pipe connection with the-steam generator for supplying water to the generator as required, an exhaust conduit leading from the exchanger to the feed water tank and providing a substantially clear channel from the heat exchanger to said tank, steam and condensate releasing means for controlling the release of steam and condensate from the exhaust conduit into said tank thereby tending to raise the water level in said tank, means responsive to a predetermined drop of the water level in the tank for operating the steam and condensate releasing means in the exhaust conduit to cause steam and condensate to enter the tank, and means for continually exhausting the steam and condensate from said exhaust conduit until the water level in the feed water tank reaches a predetermined level.

28. In a steam system, the combination of a heat exchanger, a steam generator for supplying steam to the heat exchanger, a feed-water tank having a pipe connection with the steam generator for supplying water to the generator as required, an exhaust conduit leading from the exchanger to the feed water tank and providing a substantially clear channel from the heat exchanger to said tank, steam and condensate releasing means for controlling the release of steam and condensate from the exhaust conduit into said tank thereby tending to raise the water level in said tank, means responsive to a predetermined drop of the water level in the tank for operating the steam and condensate releasing means in the exhaust conduit to cause steam and condensate to enter the tank, means for continually exhausting the steam and condensate from said exhaust conduit until the water level in the feed water tank reaches a predetermined level, and means operative during the period steam and condensate are being released from the exhaust conduit into the tank for adding new water to the tank thereby assisting the exhausted steam and condensate in raising the water level to said predetermined level.

29. In operating a steam using apparatus in connection with a steam system including a steam generator for supplying steam heat thereto, the method which consists in providing an exhaust conduit in the apparatus to convey steam and condensate therefrom, feeding water to the generator as required, increasing the volume flow of steam through the apparatus by exhausting steam from said conduit in response to a decrease in the rate at which condensate is being conveyed through said conduit relative to the demand of the generator for water, and continually exhausting steam from the conduit to maintain the volume flow of steam through said apparatus at said increased rate until the rate of crease the rate at which steam is released in response to decrease in the rate at which condensate is being returned from the system relative to the rate at which steam isbeing generated.

31. A heating system having apparatus providing heat transfer walls for drying traveling sheet material, a steam generator for delivering steam to said apparatus, means providing a supply of water, means to release steam from the low pressure side of said heat exchange means to heat said supply of water, means for drawing upon said supply of water to satisfy the feed water demand of said generator, means for drawing upon said supply of water to satisfy a demand outside of the system, means for replenishing said supply of water as required, and thermostat means responsive to the temperature of said supply of water to vary the rate of steam release from the system inversely as the temperature of the supply of water changes whereby both the heat demand on the heat exchange means and said outside demand are factors in determining the rate of steam flow through the heat exchange means, the releasing capacity of said thermostat means, the temperature setting of the thermostat means, the volume of said supply of water, and the position of the thermostat means being such that the responsiveness of said thermostat means to changes of the temperature of said supply of water incidental to steam release and incidental to replenishing flow to said supply water are of such high order that said factor of feed water demand is sufiicient in the absence of said factor of outside demand to maintain said steam release at a sufiiciently high rate to maintain the heat output of the apparatus at least twenty percent above the commonly accepted limit of heat output for the apparatus.

32. In a steam system in which a steam generator supplies steam to a heat exchanger at substantially above atmospheric pressure for the purposeof processing sheet material which is placed in heat exchange relationship with the exchanger, the improvement which consists in providing a substantially clear channel for steam to circulate from the geenrator through the heat exchanger to a point on the low pressure side of the exchanger, circulating steam through the exchanger of such quality that the major portion of the heat required by the material must be provided by release of latent heat with corresponding formation of condensate in the exchanger, removing steam from the system by releasing steam from the channel on the low pressure side of the exchanger to incur a velocity response in the exchanger over and above the replacement fiow of steam caused by condensation in the exchanger thereby increasing the potential rate of latent heat utilization in the exchanger, and varying the rate of steam release in accordance with the heat load on the excondensate return reaches a predetermined value. e

atively connected with said release means to inchanger.

33. In a steam system in which a steam generator supplies steam to a heat exchanger for the purpose of processing sheetmaterial which is placed in heat exchange relationship with the exchanger, the improved method which consists in providing a substantially clear channel for steam to circulate from the generator through the heat exchanger to a point on the low pressure side of the exchanger, circulating steam through the exchanger of such quality that the major portion of the heat required by the material must be provided by the release of latent heat with corresponding formation of condensate in the exchanger, intermittently releasing steam and condensate from said channel on the low pressure side of the heat exchanger to incur repeated velocity responses in the exchanger over and above the replacement fiow of steam caused by condensation in the exchanger and. beyond, and setting the frequency and magnitude of the intermittent steam release to cause the velocity responses in the exchanger to produce a substantially continuous pulsating flow of steam through the exchanger at said higher velocity.

34. In a steam system in which a steam generator supplies steam to a heat exchanger for the purpose of processing sheet material which is placed in heat exchanger relationship with the exchanger, the improved method which consists in providing a substantially clear channel for steam to circulate from the generator through H the heat exchanger to a point on the low pressure side of the exchanger, circulating steam through the exchanger of such quality that the major portion of the heat required by the material must be provided by the release of latent heat with corresponding formation of condensate in the exchanger, intermittently releasing steam and condensate from said channel on the low pressure side of the heat exchanger to incur repeated velocity responses in the exchanger over and above the replacement flow of steam caused by condensation in the exchanger and beyond, setting the frequency and magnitude of the intermittent steam release to cause the velocity responses in the exchanger to produce a substantially continuous pulsating flow of steam through the exchanger at said higher velocity,

densate, the method of improving the efficiency of said system which consists in removing the trap and providing a substantially clear channel for the circulation of steam through the exchanger, promoting the flow of steam through the channel and exchanger by releasing the steam from the system on the low pressure side of the exchanger, varying the amount of said steam release and hence the flow of steam through the exchanger in accordance with the heat load on the exchanger, and substantially increasing the speed at which the processed material is presented to the exchanger to take advantage of the increased rate of heat transfer through the exchanger resulting therefrom.

36. In a steam system in which a steam generator supplies steam to a heat exchanger for the purpose of processing sheet material which is passed progressively in heat exchange relationship with the exchanger and in which a substantially clear channel extends from the steam generator through the heat exchanger to the return side of the heat exchanger, the improved method which consists in promoting the flow of steam through said channel by releasing steam from the system on the low pressure side of the exchanger,

varying the amount of steam release and hence the flow of steam through theexchanger in accordance with the heat load on the exchanger, and substantially increasing the speed at which the processed material is presented to the exchanger to take advantage of the increased rate of heat transfer through the heat exchanger resulting therefrom.

37. In a steam system in which a steam generator supplies steam to a heat exchanger at substantially above atmospheric pressure for processing traveling sheet material, the improved method which consists in substantially increasing the rate at which said sheet material is presented to said exchanger with corresponding increase in heat demand on the exchanger, providing for release of steam and condensate from the system at a point on the return side of said exexchanger to incur a substantially continuous velocity response in the exchanger over and above the replacement flow of steam caused by condensation in the exchanger and beyond, thereby increasing the potential rate of latent heat utilization in the exchanger, removing any traps or other obstacles necessary to provide a channel of substantially free communication from the steam generator to said point for said velocity response, setting the rate .of steam release at a level to effectively meet the increased tendency for condensate to accumulate in the exchanger at said increased heat demand, and varying said rate of steam release with variation in said demand.

38. In a steam system in which a steam generator suppliessteam to a heat exchanger for processing traveling sheet material, the improved method which consists in substantially increasing the rate at which said sheet material is presented to said exchanger with corresponding increase in heat demand on the exchanger, providing for pulsating release of steam and condensate from the system at a point on the return side of said exchanger to incur a substantially continuous pulsating velocity response in the exchanger over and above the replacement flow of steam caused by condensation in the exchanger and beyond, thereby increasing the potential rate of latent heat utilization in the exchanger, removing any traps or other obstacles necessary to provide a channel of substantially free communication from the steam generator to said point for said velocity response, and setting the rate of steam release at a level to effectively meet the increased tendency for condensate to accumulate in the exchanger at said increased heat demand.

39. In a laundry system including a steam generator, an ironer receiving steam from said gen.-

erator at substantially above atmospheric pressure having a given heretofpre accepted output rating in terms of feet per minute of travel of given fabric under given conditions, the improved method which consists in substantially increasing the speed of travel of said ironer above said output with corresponding increase in heat demand on the ironer, providing for continual release of steam and condensate from the system on the return side of the ironer to cause a substantially continuous flow of steam through the ironer at a rate substantially above the replacement flow of steam caused by condensation in the ironer and beyond, providing a channel of substantially free communication from said generator through said ironer to said point by removing any traps or other obstacles, and setting the rate of said steam release to eflectively meet the tendency for condensate to accumulate in the ironer at said higher demand.

40. In a laundry steam system including an ironer for progressively ironing sheet material and a steam generator for supplying steam to said ironer, the method of substantially increasing and maintaining the output capacity of said ironer above its heretofore rated capacity under given conditions of use which consists in releasing steam from the system on the low pressure side of the ironer and providing a substantially clear channel from the generator through the ironer and up to the point of steam release, and setting the rate of steam release in accordance with the heatload on the system to provide asubstantially continuous flow of steam through the ironer at a velocity that is, both, substantially above that of steam replacement flow due to condensation in the ironer and beyond, and also adequate to efiectively remove by entrainment the condensate formed in the ironer under varying conditions of -load.

41. In a laundry steam system including a steam generator and an ironer having a given heretofore accepted output rating in terms of feet per minute of travel of given fabric under given conditions, the improved method which consists in increasing the speed of travel of said fabric to at least twenty percent above said accepted rating with corresponding increase in heat demand on the ironer, providing for intermittent release of steam and condensate from the system at a point on the return side of the system both for the ,purpose of incurring repeated velocity responses in the system and for the purpose of raising the flow of steam above the rate of replacement flow caused by condensation in the exchanger, removing any traps or other obstacles necessary to provide a channel of substantially free communication from the generator through the ironer to the point of such steam release, and tuning the system by setting the frequency and magnitude of the intermittent steam release to cause the increased steam flow and the jarring action of the periodic accelerations of steam flow to efiectively meet the tendency of condensate to accumulate in the ironer at said increased demand.

42. In a steam system in which the latent heat of steam is primarily relied upon for the heat processing of material, the combination of a steam generator, a plurality of heat exchangers having their inlet sides connected to the generator for receiving steam therefrom at substantially greater than atmospheric pressure, an exhaust conduit connected to the outlet sides of the heat exchangers and maintained above atmospheric pressure by discharge from said heat exchangers, means for continually releasing steam substantially to atmospheric pressure from said exhaust conduit during operation of the exchangers to increase the pressure differential between the exhaust conduit and the heat exchangers thereby to produce velocity responses within the heat exchangers substantially greater than the replacement flow of steam due to condensation within the exchangers and beyond and to cause steam and condensate to be continually exhausted into said exhaust conduit during the operation of the exchangers, and collecting condensate from said exhaust conduit at a point remote from the exchangers.

43. In a modern steam system for processing traveling material including a source of steam substantially above atmospheric pressure and a plurality of heat exchangers for processing material receiving steam from said source at said pressure, the method of operation comprising providing a clear channel arrangement for a continuous steam flow with branches in parallel through the respective heat exchangers and with a common return portion, restricting each of said branches on the output side of the corresponding heat exchanger relative to the cross-sectional area of the branch on the input side of said exchanger, and releasing steam and condensate from said system to substantially atmospheric pressure from said common return portion for maintaining high velocity flow through said exchangers at a rate substantially greater than normal replacement flow with steep local pressure gradients at said points of restriction.

44. In a steam heating system utilizing primarily the latent heat of steam for heat processing material, a steam generator, a heat exchanger, means for connecting the generator to the exchanger to provide a substantially clear channel therebetween which extends to a point on the low pressure side of the exchanger, means for normally and continually releasing steam from the channel on the low pressure side of the exchanger to continually augment the replacement flow of steam through the exchanger due to condensation therein, and means for automatically increasing the rate of steam release in response to increases in the heat load on the exchanger.

45. In a steam system in which a steam generator supplies steam to a heat exchanger at substantially above atmospheric pressure for processing traveling sheet material, the improved method which consists in substantially increasing the rate at which said sheet material is presented to said exchanger with corresponding increase in heat demand on the exchanger, providing for release of steam and condensate from the system at a point on the return side of said exchanger to incur a substantially continuous velocity response in the exchanger over and above the replacement flow of steam caused by condensation in the exchanger and beyond thereby increasing the potential rate of latent heat utilization in the exchanger, removing any traps or other obstacles necessary to provide a channel of substantially free communication from the steam generator to said point for said velocity response, and setting the rate of steam release at a level to effectively meet the increased tendency for condensate to accumulat in the exchanger at said increased heat demand.

46. The method of operating a steam system to obtain relatively high heat transfer efficiency in a heat exchanger which is included in the system, and in which the latent heat of the steam is relied upon primarily for the transfer of heat through the heat exchanger wall characterized by the steps of providing a substantially clear channel from a steam source through the exchanger to a point on the low pressure side of the exchanger, and releasing steam at a varying rate from the channel on the low pressure side of said heat exchanger to cause continual pulsating flow of steam in the heat exchanger at a velocity substantially above replacement flow of steam caused by condensation in the exchanger and beyond, and to attain repeated velocity peaks of steam flow to minimize condensate accumulation on the heat exchanger walls, and increasing the release of steam with increases in the heat load on the exchanger to further augment the flow of steam through the exchanger and increase the rate of heat transfer through the exchanger to effectively meet the increased tendency for condensate to accumulate within the exchanger.

47. In a steam system, a generator, 8, heat exchanger, means for connectin the generator to the exchanger to provide a substantially clear channel therebetween which extends to a point on the low pressure side of the exchanger, means for releasing steam from the channel on the low pressure side of the exchanger, regardless of heat load on the exchanger, to continually augment the replacement flow of steam due to condensation in the exchanger and beyond, said means including an externally exposed thermostatresponsive on the one hand to the heating effect of the released steam for cutting down the flow of steam and responsive on the other hand to the cooling effect of its environment for increasing the flow of steam.

48. In a steam system used particularly in laundry plants, the combination of a steam boiler, a heat exchanger receiving steam from the boiler, a supply of feed water adapted to be drawn upon as required for replenishing boiler water in the system and for supplying hot water demand outside of the system, means including a return line from the heat exchanger to release steam from the low pressure side of the system to heat said feed water and to promote steam flow through the system, steam releasing means associated with the return line for releasing steam from the system to incur a velocity response in the exchanger substantially above replacement fiow due to condensation in the exchanger and beyond, said steam releasing means including an externally exposed thermostat responsive on the one hand to the heating effect of the released steam and on the other hand to the cooling effect of its environment including that of the feed water supply, and means for rendering the steam releasing means comparably effective in producing such velocity response both for periods of outside demand and periods of substantially reduced outside demand.

49. In a steam system in which a steam generator supplies steam to a heat exchanger for processing traveling sheet material, the method of obtaining a high rate of heat transfer between the material being processed in th exchanger which consists in providing a substantially clear channel for th circulation of steam from the steam generator through the exchanger to a point on the low pressure side of the exchanger, intermittently releasing steam from said channel on the low pressure side of the exchanger to incur velocity responses in the exchanger over and above the steam replacement fiowcaused by condensation in the exchanger, providing a restriction in the channel between the exchanger and the point of steam release, setting the quantity and frequency of steam release so that the retarded flow caused at least in part b the restriction will cause the responses .to lag and tend to overlap in the exchanger to produce a substantiaily continuous flow of steam through the exchanger at the elevated rate, said intermittent release of steam imparting a pulsating character to the steam flow in the exchanger which, in combination with the increased velocity, minimizes condensate and non-condensible gas films on the inner walls of the exchanger and materially increases the rate of heat transfer therethrough.

50. In a steam system primarily utilizing latent heat, a steam generator, a heat exchanger for processing material, a pipe for delivering steam from said generator to said exchanger, a return pipe from said exchanger, said steam pipe, heat exchanger and return pipe forming a channel of open communication, and means to release steam from said channel onthe low pressure side of the exchanger in a pulsating manner, said channel in the region of the return side of said exchanger being restricted to smaller diameter than said return pipe whereby the puplsating release of steam repeatedly creates local pressure gradients at the return side of the exchanger of substantially greater magnitude than can be attained by uniform release of the same amount of steam, said local restrictions maintaining back pressure in the heat exchanger and causing said local gradients to endure for substantially longer periods than the steam pulsations.

51. A method of operating a steam system including a steam generator and a heat exchanger receiving steam therefrom to process material consisting in normally releasing fluid from the return side of the system at a continually varying rate to normally cause pulsating flow through the heat exchanger at suflicient frequency and sufllcient flow velocity to remove condensate from the exchanger and to keep condensate on the heat exchanger walls sufllciently low in quantity to meet the demand for heat by said material, and increasing the average rate of said pulsating flow to meet increasing heat demand by th material.

52. A method of operating a steam heating system which comprises adding water on the boiler side of the system and releasing steam and condensate on the return side of the system with a causal relationship wherein the addition'of water to the system results automatically in the release of steam, independently releasing steam to maintain the temperature of a thermal means, and utilizing said causal relationship and the heat demand of said thermal means to substantially continually release steam from the return side of the system thereby to maintain substantially continual fiow of steam through the system.

53. A method of operating a steam heating system which comprises adding water on the boiler side of the system and releasing steam and condensate on the return side of the system with a causal relationship wherein the addition of new water results automatically in the release of steam, independently releasing steam to maintain the temperature of a thermal means, utilizing said causal relationship and the heat demand of said thermal means to substantially continually release steam from the return side of 'the system thereby to maintain substantially continual flow of steam through the system, and utilizing at least a part of the released steam to heat and deaerate the added water.

' E. PAUL HARRISON.

ORVILLE A. HUNT.

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