US2311711A - Refrigeration - Google Patents

Description

. Feb. 23, 1943. THOMAS 2,311,711

' REFRIGERATION Filed,'.Aug. 3, 1940 MAT'IORNEY' v Patented Feb. 23, 1943 REFRIGERATION v Albert R. Thomas, Evansville, Ind., assignor to Scrvel, Inc., New York, N. Y., a corporation of Delaware Application August 3, 1940, Serial No. 350,239

Claims.

This invention relates to refrigeration, and more particularly to refrigeration systems of the type operated by heat and with which may be associated a heating'system.

In application Serial No. 239,762 of A. R. Thomas and P. P. Anderson, Jr., filed November 10, 1938, it has already been proposed to providean absorption refrigeration system having a generator or vapor expeller provided with a steam chamber to which steam is supplied to cause expulsion of refrigerant vapor from absorption liq-' uid and also effect lifting of liquid'to a higher level by vapor-lift action. The steam for effectwhich air passes to an enclosure, and suitable valves may be provided so that the steam from the boiler either effects heating of the generator to cause a cooling effect to be produced by the cooling element, or heating of the radiator to cause a-heating effect to be produced by the heating element.

It is an object of this invention to provide an improvement for controlling the heat supply to the steam boiler, so that the supply of steam to the generator of the refrigeration system or to the heating element of the heating system is reduced when steam passes into the atmosphere through the vents provided in the generator steam chamber and heating element. This is preferably accomplished by joining the vents of the generator steam chamber and heating element to provide a single common vent, and controlling the flow of fuel to a burner associated with the steam boiler responsive to the temperature condition in the common vent. When provision is made for returning steam condensate to the boiler, the control provided prevents excessive loss of water from the boiler, so that the necessity of a float valve for make-up boiler water is avoided. Further, the single control providedtakes the place of many controls that would otherwise be necessary to insure safe operation of the refrigeration system and also of the heating system. The provision of a single control to take the place of many controls is possible because numerous adverse operating conditions that may occur are felt at the vent through which steam can pass into the atmosphere. For example, the cessation of cooling water to the absorber and condenser of the refrigeration'system causes rise in temperature of these parts and also rise in temperature of the generator, so that steam will pass through the vent into the atmosphere. In the refrigeration system a high concentration of lithium chloride or similar salt solution is employed which is close to the solidifying point, and under adverse conditions such a quantity of salt may precipitate that the passages in the absorption liquid circuit are closed and blocked. Blocking or plugging of the absorption liquid circuit causes the temperature of the generator to rise, so that steam will pass through the vent into the atmosphere. Also, when the blower in the duct system stops and there is loss of air circulation during a period when steam is being supplied to the heating element or radiator, the lossv of load on the element causes steam to flow through the vent into the atmosphere. It will be evident, therefore, that safe operation of the refrigeration system and heating system can be insured by controlling the heat supply to the steam boiler responsive to flow of steam through the common vent to the. atmosphere.

- The invention, together with the above and other objects and advantages thereof, will be better understood from the following description taken in conjunction with the accompanying drawing forming a part of this specification, and of which:

Fig. 1 is a view more or less diagrammatically illustrating a refrigeration system and heating system provided with a control embodying the invention; and

Fig. 2 is a fragmentary view diagrammatically illustrating another embodiment of the invention.

The disclosure in the aforementioned Thomas and Anderson application may be considered as being incorporated in this application, and, if desired, reference may be made thereto for a detailed description of the refrigeration system. The generator l includes an outer shell l5 within which are disposed a plurality of riser tubes l6 having the lower ends thereof communicating with a. space H and the upper ends thereof extending into a vessel IS. The space l9 within shell l5 and about the tubes l5 forms a steam chamber to which steam is supplied through a conduit 20 forming boiler 2|.

The boiler 2| is provided with a fire or heating tube 22 into the lower end of which is adapted to project the flame produced by a burner 23. A combustible gas is delivered from a source of supply through a conduit 24, a control device 25 to be described presently, and conduit 26 to the burner 23. While only a single heating tube and burner are illustrated, a number of heating tubes and burners may be employed with the upper end of each tube connected to a flue or riser 2?. The water in boiler 2| is heated by the hot gases passing through the heating tubes 22, thereby producing steam which flows through conduit 26 to generator ID. A suitable hand controlled valve 28 is provided in conduit 20 to obtain manual control of the steam flow to the generator.

The space l9 provides for full length heating of riser tubes it by the steam, and a vent 2 is provided at the upper end of shell l5 through which steam can flow into the atmosphere, as will be described presently. Condensate formed in steam chamber l9 flows back to boiler 2i through conduit 3!], jacket 3| and conduits 32 and 33,'the jacket 3| having a vent Sta to atmosphere.

The system operates at a partial vacuum and contains a solution of refrigerant in absorption liquid, such as, for example, a water solution of 40% lithium chloride by weight. When steam is supplied through conduit 20 to space 59, heat is supplied to tubes !6 whereby water vapor is expelled from solution. The absorption solution is raised by vapor-lift action with the expelled water vapor forming a central core within an upwardly rising annulus of the solution. The expelled water vapor rises more rapidly than the solution and the latter follows the inside walls of tubes IS. The water vapor flows upward through the tubes l6, vessel 18, conduit 34, vapor separating chamber 35 and conduit 36 into condenser ii in which it is liquefied. The condensate formed in condenser flows therefrom through a U-tube 31, flash chamber 38, and conduit 39 into evaporator i2.

The water supplied to evaporator l2 vaporizes therein to produce a refrigerating or cooling effect. The vapor formed in evaporator i2 passes through pipes 40 ano 4| which are connected to absorber It. To prevent disturbances in evaporator l2, the flash chamber 38 is provided to take care of any vapor flashing of liquid being fed to the evaporator through U-tube 31. The flashed vapor formed in the initial cooling of liquid flowing from the condenser passes through a conduit 42 to pipe 4| and mixes with the vapor formed in evaporator l2.

In absorber l4 refrigerant vapor is absorbed into concentrated absorption solution which enters through a conduit 43. The water vapor absorbed into solution dilutes the latter, and the diluted absorption solution flows through a conduit M, a first passage in liquid heat exchanger 55, a conduit 66, vessel 51, and conduit 48 into the lower space H of generator l0. Water vanor is expelled out of solution in generator ID by heating; and the solution is raised by vaporlift action in the vertical tubes 5, as explained above.

The absorption solution in vessel I8 is concentrated since water vapor has been expelled therefrom in generator In. This concentrated solution flows through a conduit 5|], 2. second passage in liquid heat exchanger 45, and conduit 63 into absorber M. This circulation of absorption solution results from the raising of liquid by vapor-lift action in vertical riser tubes i8, whereby the solution can flow to the absorber i i and return from the absorber to the generator 00 by force of gravity.

The upper part of vessel 41 is connected by a conduit 5| to vessel l8, whereby the pressure in vessel Al is equalized with the pressure in the upper part of generator i0 and condenser ll. Any liquid separated from vapor in separating chamber 35 flows through a U-trap li) and conduit 5| back to vessel 41.

The lower part of evaporator i2 is connected by a conduit 52 and a jacket 53 to vertical tubes or riser 4%, whereby unevaporated liquid flows from the evaporator and is preheated in jacket by condensate flowing to boiler 2| through conduit 33. After being preheated in jacket 53, the unevaporated liquid passing from evaporator 52 is raised byvapor-lift action in risers 54 by the heating effect of the condensate in jacket 3|, as described more fully in application Serial No. 350,882 of P. P. Anderson, Jr., filed August 3, 1940. The liquid is raised in risers 5G to a vessel 55 from which the liquid flows through a conduit 56 into absorber M.

The heat liberated with absorption of water vapor in absorber M is transferred to a cooling medium which flows upward through a plurality of pipe coils 51. The cooling medium, such as water, for example, is supplied through a conduit {58 to a manifold 59 to which the lower ends of the pipe coils 51 are connected. The

.upper ends of the pipe coils are connected to a manifold 60 from which the cooling water flows through a conduit 6| to the condenser The cooling water leaves condenser through a conduit 32.

The system operates at a low pressure with the generator 50 and condenser i l operating at one pressure and the evaporator l2 and absorber i l operating at a lower pressure, the pressure differential being maintained by liquid columns. Thus, the liquid column formed in the tube 31 maintains the pressure differential between condenser ii and evaporator i 2. The liquid column in conduit M maintains the pressure difierential between the outlet of absorber i l and generator ill. The liquid column formed in conduit 33 and parts connected thereto including conduit 50 maintains the pressure differential between the inlet to absdrber M and the upper part of generator II]. In operation, the liquid columns may form in conduits 33 and 50 and down-leg of tube 31 to the levels :r, y and z, for example. The conduits are of such size that restriction to gas flow is eifected without appreciably restricting flow of liquid. The liquid column formed in vessel 41 and conduit 58 provides the liquid reaction head for raising liquid in the vertical tubes l6 by vapor-lift action.

The vessel i! is of suflicient volume to hold the liquid differential in the system and is of such cross-sectional area that the liquid level therein does not appreciably vary, so that a substantially constant reaction head is provided for lifting liquid in generator I0. The vessel 31 is located below absorber I4 such a distance that. for the greatest pressure difierential occurring between absorber I4 and the upper part of generator I during operation of the system, the liquid column formed in conduit 44 is below the lower end of absorber I4.

The evaporator I2 constitutes a cooling element of the refrigeration system and includes a plurality of tubes 63 to which cooling fins 64 are secured. The cooling element I2 may be arranged in a duct 65, indicated in dotted lines,'

are normal to the duct 65,'but it should be understood that in practice the cooling fins 65 extend inthe direction of the air flow and are parallel or lengthwise of the duct.

In the duct 65 is also disposed a heating element or radiator 66 comprising spaced headers 61 connected by a plurality of tubes 68 to which are secured heat dissipating fins 69. As in the cooling'element I2 described above. the fins 69 in practice extend lengthwise of and are par- I allel to the duct 65, although in the drawing they through conduit 20 to space |9 of generator I 0. I

With heating of generator I0 a cooling efiect is produced by cooling element I2, in the manner described above, and the cooling eifect is transmitted to air flowing in duct 65. Conversely, when it is desired to heat air flowing through conduit 65, valve 28 is closed and valve II is opened, whereby steam flows from boiler 2| through conduit I0 toheating element 66. The heating efiect produced by heating element 66 is transmitted to air flowing through the duct 65. The condensate formed in heating element or radiator 66 flows through a conduit I2 back to the boiler 2|. A vent I3 is connected to conduit 12 at the region where the latter is connected to one of the headers 61, so that steam can flow from the heating element into the atmosphere.

In accordance with this invention, the vents 29 and 13 associated with the generator steam chamber I9 and heating element 66 are joined to provide a common vent, and when flow of steam takes place through the common vent the supply of fuel to burner 23 is reduced responsive to increase in temperature in the, vent. As shown, the ventsor vent conduits 29 and I3 are joined to a conduit I4 forming a common unobstructed vent which always permits steam to pass into the atmosphere either from heating element 66 or the generator steam chamber I9.

In the common vent is located a thermal bulb I5 which is connected by a capillary tube I6 to an expansible and contractible bellows 'I'I fixed at one end to a suitable support 18. The bellows 11, tube 16, and bulb I5 constitute an expansible fluid thermostat containing a suitable volatile fluid which increases and decreases in volume with corresponding changes in temperature. bellows I1 expands and contracts with increase and decrease in volume of the volatile fluid, and these movements of the bellows I1 are utilized to control a switch 19 in an electrical circuit in which is connected the control device 25 in the fuel line to the burner 23.

As shown, the switch I9 is of the snap-acting type and includes upper and lower toggle arms and 8| pivotally connected at their inner ends at 82 to a suitable support. A coil spring 83 is connected to the outer ends of toggle arms 80 and 8|. The outer end of toggle arm 8| is connected by a link 84 to the free or movable end of bellows 11. The outer end of toggle arm 80 is provided with a contact 85 which moves between and is adapted toengage either one of two fixed contacts 86 and 81. The contact 86 is connected to a conductor 88 in which is provided an energizing coil 89 of an electrical relay 90. i

The relay 90 includes a pivoted arm 9| to which is secured a contact 92 which cooperates with a fixed contact 93. The energizing coil 89 is adapted to attract arm 9| against the action of a spring 94 to close contacts 92 and 93. -Arm 9| is connected to a dash pot 95 so that, when coil 89 is energized, the latter is effective to close contacts 92 and- 93 after a definite time delay.

When arm 9| is raised to close contacts 92 and 93, a member 96 connected to the outer end of the arm is also raised to close the contacts of a relay 9! provided in a conductor 98 which is also secured to the pivotedarm 9|. The conductor 99 is connected to conductor 89 at a region between the contact 86 and a manual switch 99 which is at one side of coil 89 of relay 90.

The contact 93 is connected through a coil |0I of a relay I02 to conductor 88. The contacts of relay I02 are connected in a conductor I03 which is connected at one end to contact 81 of switch I9, and at the opposite end to a terminal of a solenoid coil I04 in control device 25. 'The other terminal of coil I04 is connected by a conductor I05 to conductor 88, and to conductor I05 is secured a conductor I06. The inner end of toggle arm 80 is connected by a conductor I01 to conductor 98, the inner end of toggle arm 80 being insulated in any suitable manner from the pivotal connection at 82. The conductors 98 and I06 are connected to a suitable source of electrical supply.

The solenoid coil I04 of control device 25 is formed to receive a plunger I08 to which is fixed a valve I09. When solenoid coil I04 is energized, the plunger I08 is raised and valve I09 is in its open position to permit flow of fuel to burner 23. Conversely, when solenoid coil I04 is de-energized, the plunger I08 moves downward by gravity and valve I 091s moved to its closed position to shut ofi flowofiuel to burner 23., A small tube H0 is connected to conduit 24 and terminates in the vicinity of burner 23' to system or the refrigeration system, and when .an and at no steam flows through the common vent conduit i l, the volume of the volatile fluid in the expansible fluid thermostat is reduced and the bellows TI is inthe contracted position shown in the drawing. In the contracted position of bellows ill, the contacts 85 and 81 are closed and the contacts of relay I02 are also closed. Under these conditions, solenoid coil IN! is energized and valve W9 is in its open position so that fuel flows to burner 23. From the source of electrical supply the completed circuit includes conductors 9B and Hill, toggle arm 80, contacts 85 and 37, and conductor M3 to one terminal of solenoid coil Iil i. From the other terminal of solenoid coil Hid the circuit includes conductors 585 and 106 back to the source of electrical supply.

Let us now assume that the refrigeration system is being heated by steam from boiler 2i and flow of cooling water through conduit 58 stops, so that there is cessation of cooling water to absorber i l and condenser ii. In such case the temperature of absorber it and condenser M will rise, and, as a result of the rise in temperature of these parts, the pressure and temperature of generator ill and condenser i I will also rise to an abnormally high value. Under these conditions heating vapor or steam supplied to chamher it flows through vent conduit 2E5 into the common vent l6 and thence passes into the atmosphere which constitutes an environment containing a gaseous fluid at a substantially constant pressure. When the temperature in vent conduit l rises, due to flow of steam therethrough, the Volatile fluid of the expansible fluid thermostat increases in volume and causes the bellows T1 to expand. With expansion of bellows Til clock-wise movement is imparted to lower toggle arm 3i, and, when the coil spring 83 is moved past the straight line position of the toggle arms 89 and SI, the upper toggle arm till moves with a snap-action toward the left to separate contacts 95 and 81 and close contacts 85 and 89. When contacts 95 and ill are separated to circuit described above for solenoid coil BM is opened, whereby the latter is de-energized and valve 899 moves by gravity to its closed position to shut off flow of fuel to burner 29.

The closing of contacts 85 and 36 completes a circuit for energizing coil 89 of relay 99. From the source of supply this circuit includes conductors 99 and till, toggle arm 89, contacts 65% and S6 to one terminal of coil 89. From the other terminal of coil 89 the circuit includes conductors 88, W5 and 806 back to the source of electrical supply. The dash pot 95 is provided so that a definite time delay must occur before arm BI is raised sufiiciently high to close contacts 92 and 93. In the event flow of cooling water is resumed through conduit 58 to pipe coils Ell of absorber it and to condenser H within the period of the time delay, the temperature of the absorber and condenser are reduced and the generator pressure and temperature will fall, whereby steam will no longer flow through vent conduits 29 and "i i and normal operation of the refrigeration system is resumed. With steam no longer flowing through vent conduit it, the volatile fluid of the expansible fluid thermostat decreases in volume and causes the bellows fill to contract. With contraction of bellows ll, counter-clockwise movement is imparted to lower toggie arm BI, and, when the coil spring 93 is moved past the straight line position of the toggle arms in the opposite direction, the upper toggle arm 88 moves toward the right with a snap-action to separate contacts and BB'and close contacts 85 and 81. Since it has been assumed above that the switch 19 has been operated by the expansible fluid thermostat within the period of the time delay, the contacts 92 and 93 of relay are still open and the contacts of relay H12 are closed, so that the circuit for solenoid coil Hi4 described above is again completed. With solenoid coil lfl l energized again, valve N19 is moved to its open position whereby flow of fuel to burner 23 is resumed.

However, if the cooling water supply to absorber M and condenser H is not resumed within the period of the time delay efiected by dashpot 95, and assuming that steam is still flowing through vent conduit i l so that contacts 85 and 86 are closed and contacts 85 and 8'! are open, the arm 9| of relay 9!! is raised sufliciently high within the period of the time delay to close contacts 92 and 93. At the time the contacts 92 and 93 close, the contacts of relay 9l.are also closed by member 96 which is raised by arm 9|. This completes a holding circuit for energizing coil 39 of relay 9D in the event that toggle arm 80 of switch i9 is moved after the period of the time delay to open contacts 35 and 86. Thus, even though flow of steam through vent conduit 74 should stop after the period of the time delay and contacts 85 and 86 are separated in the manner described above due to cessation of steam flow, still a holding circuit is completed for energizing coil 89. This holding circuit from the source of electrical supply includes conductor 98 in which the contacts of relay 9'! are closed by member 96, and switch 89 to one terminal of a coil 89. From the other terminal of coil 99 the holding circuit includes conductors 88, M5 and M36 back to the source of electrical supply. When the holding circuit for energizing coil 89 of relay 9%] is completed, as just described, contacts 92 and 93 close to complete a circuit for coil iii! of relay I02, so that the contacts of this relay are open. This circuit from the source of supply includes the conductor 98 in which the contacts of relay 91 are closed by member 96, arm 9|, contacts 92 and 93 of relay 9i), and conductor 599 to one terminal of coil illl. From the other terminal of coil Mil the circuit includes conductors i105 and E95 back to the source of electrical pply.

When the contacts of relay ")2 are closed after the definite time delay, the circuit for solenoid coil Hill cannot be completed even when the flow of steam stops through vent conduit 16 and the bellows ll causes toggle arm 80 of switch 19 to move to the right in the manner described above to close contacts 35 and 81. After the definite time delay and with steam no longer flowing through vent conduit M, so that contacts 85 and 8'! are closed, the circuit for solenoid coil I04 can be completed by opening switch 99 to break the holding circuit for energizing coil 89 of relay 99. When the holding circuit for coil 89 is broken, contacts 92 and 93 separate and the com tacts of relay 91 are opened. Separation of contacts 92 and 93 de-energizes coil I Ill, so that the contacts of relay I02 are closed and the circuit for solenoid coil I04 is again completed, assuming that there is no flow of steam through conduit M and contacts 85 and 87 are closed.

The single control just described takes the place of many controls that would otherwise be necessary to insure safe operation of the refrigeration system and also of the heating system.

The lithium chloride solution employed in the refrigeration system is of such concentration that it is near its solidifying point, and, in the event that blocking or plugging of the absorption liquid occurs in the absorption liquid circuit due to excessive salt precipitation, the temperature of the generator I will rise so that steam will pass through vent conduits 29 and I4 into the atmosphere. Also, during the periods when heating is being effected by heating element 06 there may be loss of air circulation in duct due to operating failure of the blower or fan in' the duct system. In such case, loss of load on the heating element 66 causes flow of steam through vent conduits I3 and I4. Thus, when any adverse operating condition causes steam to flow through vent conduit I4, the control illustrated will operate and function in the manner described above to reduce flow of fuel to burner 23.

In addition to the control described, a normal control is usually provided for controlling the fuel supply to the burner 23 or a plurality of such burners, whereby regulation of the steam supply to the heating element 66 or. generator steam chamber I9 can be controlled. When the rate at which steam is supplied to chamber I9 is such that the latter is not completely filled with steam, air can enter the chamber with the result that self-regulation of the heating of generator I0 is effected which is proportional to the heat input to the boiler H by the burner 23. The normal control is generally operative responsive to a temperature condition affected by the heating or cooling elements, and may be of the character described in my application Serial No. 350,237,-filed August 3, 1940, in which sequential control of a plurality of burners is effected.

The normal control may include switches which are also connected in thecircuit or circuits of the solenoid coil or coils I04, and, when an adverse operating condition occurs which causes flow of steam through vent conduit I4, the control described above will open the circuits of the solenoid coil or coils to shut off flow of fuel to the burner or burners. When the adverse operating condition is corrected and steam no longer flows through vent conduit 14, the switch I9 closes the circuit for the solenoid coil or coils and the switch or switches associated with the normal control will exercise influence over the solenoid coil or coils I04 of the control devices 25, to regulate flow of fuel to one or a plurality of burners.

In Fig. 2 another embodiment of the invention is illustrated in which parts similar to those shown in Fig. 1 are designated by the same reference numerals. In Fig. 2 the control includes an expansible fluid thermostat like that in Fig. 1 having a bellows 'II flxed to a suitable support I8, a capillary tube 16, and a thermal bulb. The thermal bulb is not shown in Fig. 2, but it is to be understood that such a bulb is provided for the expansible fluid thermostat in Fig. 2 and is adapted to be located in the vent conduit I4. The bellows I1 is provided with a raised knob H2 opposite to which is a reset button H3. To

outer ends of the togglearms, and a pivotal connection at 82' to the bracket H5. The lower toggle arm 8I' is not connected to knob H2 and is located in the path of movement thereof.

The upper toggle arm 8 I ismovable between a contact 81' and an insulated stop member II8, the contact 81 being adapted to cooperate with a contact 85' at the end of toggle arm 8|. Conductors H9 and I20 are connected to a source of electrical supply, the conductor II9 being connected to one terminal-of solenoid coil I04 and the conductor I20 being connected to the inner end of toggle arm 80 which is insulated in any suitable manner from the pivotal connection at 82'. The contact 81 is connected bya conductor I2I to the opposite terminal of solenoid coil I04. 7

During normal operation of either the refrigeration system or the heating system, and when there is no flow of steam through vent conduit 34, the volume of the volatile fluid in the expansible fluid thermostat is reduced and the bellows TI is in its contracted position. In such contracted position of bellows 'II the lower toggle arm Si is bearing against the knob H2 and contacts 85' and 81 are closed to complete the circuit for the solenoid coil I04. This circuit from the source of electrical supply includes conductor I 20, toggle arm 80', contacts 85' and 01', and conductor I2I to one'terminal of solenoid coil I04. From the otherterminal of coil I04 the circuit is completed through conductor I I9 back to the source of electrical supply.

When an adverse operating condition occurs which causes flow of, steam through vent conduit I4, the volume of the volatile fluid in the expansible fluid thermostat increases and causes expanthe button H3 is secured a sleeve II4 which passes through an opening in a bracket H5 and is provided with an enlarged head II6 to receive a coil spring Ill.

The switch 10' in Fig. 2 is like the switch 13 in Fig. 1 and includes upper and lower toggle arms and 8|, a coil spring 83 connected to the sion of bellows 11. With expansion of bellows 'I'I clockwise movement is imparted to lower toggle arm 8|, and, when the coil spring 83' is moved past the straight line position of the toggle arms, both of the toggle arms move with a'snap-action toward the left. With such snap-action the lower toggle arm 8| moves against the button H3, and the upper toggle arm 80' moves against the stop H8. When switch I9 is operated in the manner just described, contacts 85 and 81' are separated whereby the circuit for solenoid coil I04 is broken and the latter is deenergized. With de-energization of solenoid coil I04, the plunger I08 moves downward by gravity, so that valve I09 is moved to its closed position to shut oif flow of fuel to the burner.

In order to start flow of fuel to burner 23, it is necessary to push the enlarged head I I6 against for solenoid coil I04, whereby the latter is energized to cause valve I09 to move to its open position. The embodiment in Fig. 2 difiers from that illustrated in Fig. 1 and described above in that,

after the solenoid coil I04 is de-energized due to I flow of steam through vent conduit 14, it becomesnecessary to manually reset switch 19" by moving reset button H3.

The normal control switch for solenoid coil I04 may be connected in either of conductors H9 or I so that, when the switch 19' is closed, the normal control switch will exercise influence over the solenoid coil I04. As pointed out above, such normal control switch is usually operative responsive to a temperature condition affected either by the heating element 66 or the cooling element I2.

While several embodiments of the invention have been shown and described, it will be apparent that modifications and changes may be made without departing from the spirit and scope of the invention, as pointed out in the following claims.

What is claimed is:

1. In a refrigeration system operated by heat and having a heat receiving part provided with a chamber, a conduit connected to supply steam to said chamber from a source of supply, said chamber having a vent to atmosphere, and a de vice responsive to a condition affected by flow of steam through said vent from the chamber into the atmosphere for controlling flow of steam through said conduit.

2. In refrigeration apparatus operated by heat and having a heat receiving part provided with a chamber, a boiler, a heater for heating said boiler to produce steam in the latter, said chamber being connected to receive steam from said boiler and having a vent to atmosphere, and means responsive to flow of steam through said vent from said chamber into the atmosphere for rendering said heater ineffective to heat said boiler.

3. In a refrigeration system having a heat receiving part provided with a chamber, a conduit connected to said chamber for supplying steam thereto from a source of supply, said chamber having a vent to atmosphere, and a control device operative responsive to flow of steam through said vent from the said chamber into the atmosphere to reduce the flow of steam through said conduit to the chamber, said device being so constructed and arranged that, after cessation of flow of steam through said vent, the device must be manually operated to cause an increase in the flow of steam through said conduit to said chamber.

4. In a refrigeration system having a heat receiving part provided with a chamber, a boiler, a heater for heating said boiler to produce steam in the latter, said chamber being connected to receive steam from said boiler and having a vent to atmosphere, whereby air can enter said chamber and self-regulation of said heat receiving part is effected which is proportional to the heat input to said boiler by said heater, and a thermostat having a part arranged tobe heated by steam flowing through said vent from the chamber into the atmosphere for reducing the heat input to said boiler by said heater.

5. In a refrigeration system having a heat receiving part provided with a chamber, a boiler, a heater for heating said boiler to produce steam in the latter, said chamber being connected to receive steam from said boiler and having a vent er by said heater, said last-mentioned means be- I ing so constructed and-arranged that, when flow of steam through said vent stops within a definite period of time, the heat input to said boiler by said heater is automatically increased.

6. In a refrigeration system as set'forth in claim 5 in which said last-mentioned means is ineffective to cause an increase in the heat input to the boiler by said heater after an interval of time longer than said definite period, even when flow of steam stops through said vent from said chamber into the atmosphere.

7. In a refrigeration system having a heat receiving part, a heating element associated with said part for heating the latter, said heating element being connected to receive steam from a source of supply, a vent to atmosphere connected to said heating element, and thermostatic means responsive to the flow of steam through said vent from within said heating element into the atmosphere for reducing the supply of steam to said heating lement.

8. In a refrigeration system having a heat receiving part, a heating element associated with said part for heating the latter, said heating element being connected to receive steam from a source of supply, a vent to atmosphere connected to said heating element, and structure responsive to the flow of steam through said vent from within said heating element into the atmosphere for reducing the supply of steam to said heating element, such structure being so constructed and arranged that, when fiow of steam through said vent stops within a definite period of time, the supply of steam to said heating element is automatically increased.

9. In a refrigeration system having a-heat receiving part, a heating element associated with said part for heating the latter, said heating element being connected to receive steam from a source of supply, said heating element being unobstructedly vented to atmosphere so that steam can pass through the vent from the interior of said heating element to the atmospher and air can enterthe interior of said heating element when the supply of steam is insufiicient to fill completely the interior of the heating element, and a control influenced by steam flowing through said vent from the interior of said heating element into the atmosphere for reducing the supply of steam to said heating element.

10. In a refrigeration system having a heat receiving part, a heating element associated with said part for heating the latter, said heating element being disposed in an environment containing gaseous fluid substantially at a constant pressure, means for supplying heating vapor to said heating element, said heating element being vented so that heating vapor may pass through said vent from the interior of said heating element into the surrounding environment and gaseous fluid may pass through said vent from the surrounding environment into the interior of said element when the rate at which heating vapor is supplied to said element is insufiicient to fill completely the interior of the latter, and a control responsive to flow of heating vapor through said vent from the interior or said heating element to the surrounding environment for reducing the supply of heating vapor to said heating element.

ALBERT R. THOMAS.

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