US2122573A - Apparatus for evolving water vapor - Google Patents

Description

'July 5, 1938. F. E. P. KLAGES APPARATUS FOR EVOLVING WATER `VAPOR Filed Aug. 14, 1935 Patented July 5, 1938 PATENT OFFICE APPARATUS FOR EVOLVING WATER VAPOR Frank E. P. Klages, Park Ridge, Ill., assignor to The VPowers Regulator Company, Chicago,

Application August 14, 1935, Serial No. 36,062

2 Claims.

f This application is a continuation-in-part of my application Serial No. 736,823, filed July 25,-1934.

My invention relates to apparatus for evolving 5 water vapor, and particularly to a simplified form of apparatus by means of which a relatively large body of water vapor may be developed in apparatusof small dimensions and moderate cost.

An object of my invention is to provide for '10 adequate production of water vapor at a greatly reduced cost of apparatus and reduction in space required for installation.

In air conditioning, in cases where water is to be added to the air, some means must be provided for breaking up the Water in order to facilitate its mixture with air. The simplest form of humidication is to supply the water in the form of vapor and this is commonly accomplished by heating a body of Water to a temperature at which it gives off vapor. However, in order to produce an adequate volume of vapor, a relatively large volume of water must be-heated with its surface open for the escape of Vapor. Furthermore, such a body of water is sluggish in action and considerable time is required to raise it to a Steam producing temperature, and an equal time to lower its temperature to a point at which it does not give off vapor.

I have found that a highly desirable result can be secured with a relatively very small body of water and a compact heat exchange element. I providea small pan and mount a steam pipe horizontally therein, the pipe having a large number of closely adjacent, vertical fins thereg5 on; .By means of a at controlled valve I maintain a Water level in the pan at such point that about one half of the pipey and fins are exposed above the Water. This provides a highly efficient vapor evolving apparatus, but still greater eiliciency is secured where the ends of the spaces between adjacent ns are closed, thus providing very narrow, confined spaces open at top and bottom. Furthermore, I have found that if the said confined space is extended upwardly a substantial distance, the result is more satisfactory and a, substantial increase in the quantity of water vapor evolved results therefrom, because the rate of heat transfer at these points Where vaporization is actually taking place is higher than at points Where no vaporization is taking place. This is accomplished by surrounding the iin structure with a continuous wall extending a substantial distance thereabove. --.fIhis has the effect of isolating the body of bubbles from the water in the tank and permits the ebullient material to rise to a height a substantial distance, not only above the Water level, but above the tops of the ns.

In Heat Transmission by McAdams it is stated:

The vapor bubbles that form in a boiling liquid do not spontaneously originate at all points in the liquid but at favored points on asolid surface. At a given temperature, the vapor pressure from a concave liquid surface, such as the 10 surface formed by a steam bubble in water, is less than the vapor pressure from a iiat liquid surface. Hence, for a given pressure, a liquid must be hotter to evaporate into a small bubble of vapor than to evaporate into the vapor space 15 above the liquid. The vapor pressure at a given temperature decreases with increase in curvature of the concave liquid surface, i. e., with the decrease in size of the vapor bubble. The difficulty in forming vapor bubbles then becomes apparent, since the curvature of the liquid surface of a newly formed bubble is very great and the Vapor pressure is reduced, requiring a higher temperature than the saturation temperature corresponding to the pressure. Therefore it is not surpris- -25 ing that vaporization occurs only from favored spots on the heating surface where temperature and nature of the surface are favorable.

In the operation of devices for evolving Water vapor, there is a tendency toward the formation of scale or salt deposits on the heat transfer structure, particularly where the water that is used is not treated or softened and my invention contemplates the provision of automatically operating means for supplying measured quantities of a chemical that will act to precipitate the lnsoluble salts and prevent the deposits on the heat transfer elements such as the pipes and fins. Also provision for draining off thel mud or sludge formed by this treatment.

The apparatus will be more readily understood by reference to the accompanying drawing in which;

Fig. l is a plan view of such apparatus;

Fig. 2 is a longitudinal sectional View showing 45 controlling apparatus, and

Fig. 3 is a sectional view on the line 3 3 of Fig. l.

In the drawing I have shown a shallow pan l0 having a drain Illa and an adjacent float cham- 50 ber Il containing a valve controlling float I2 by means of which a constant level of Water, indicated at I3, may be maintained in the pan. Preferably the level will be maintained about midway of the height of the pipes, four of which 55 are indicated at I4. These pipes are mounted in suitable headers and have a steam inlet connection I5 and an outlet connection I6 provided with a steam trap II. A hygrostat is indicated generally at I8, this instrument controlling, by means of air under pressure, a diaphragm valve I9 in the steam' supply pipe.

In order to automatically supply a scale-preventing chemical, I provide a container 20 connected by a pipe so as to deliver the liquid to the pan, the pipe containing a diaphragm valve 2 I. This valve is operated by air released by the hygrostat through the pipes 22--23, the pipe 22 leading to the diaphragm steam valve, the pipe 23 being a branch thereof. 'I'he arrangement'is such that as the hygrostat is actuated-.by a reduction in moisture content of the surrounding medium, air will be released to actuate valve I9 and supply steam to the apparatus, and to open the diaphragm valve 2| to supply chemical, by drops, to the pan; thus the chemical is supplied only when water vapor is being evolved.

Preferably the pipes I4 are provided with eX- tended surfaces or ns 24 shown as square in this instance. However, the form of the extended surfaces is unimportant except that they should be of such dimensions as to provide for immersion of a portion beneath the level of the water and the projection of the remaining portion above the level of the water.

In order to increase the eiliciency of the apparatus I provide side walls 25 that serve to close the otherwise open ends of the narrow spaces between adjacent iins 24 and I extend the side walls a substantial distance above the top-edges `of the fins. This provides a conned space closed at the sides by the walls 25 and at the ends by extending the end fins vertically as at 26 to correspond to the height of the side walls. Within this conned space the bubbles pile upto a substantial height, due to the greater heat within the coniined space and as the bubbles arerprevented from spilling over the sides and as the water level is at a point substantially below the confined space the evolution is very rapid. Furthermore, by maintaining the water level at a point only midway 'of the height of the ns, the violent agitation of the water within the narrow space between the ns has the eiect of constantly wetting the eX- posed surface of the fins with a thin lm of water that is almost instantaneously changed into vapor. The anti-scale liquid chemical employed may be any one of several that are used for the purpose. Such chemicals act as a colloid and are sometimes called thermal colloids.

The form and arrangement ofthe parts is relatively unimportant, the only essentialA being a heat supplying conduit and means for maintaining a constant level of water, the conduit being partly immersed and partly exposed. The depth of the body of water is unimportant.

It should be noted that the heat that is supplied for changing the liquid into vapor is applied only to the top surface of the body of water and there is no necessity for equally heating the entire body of water in order to produce water vapor. Consequently, the action of supplying and discontinuing the supplyrof vapor is almost instantaneous, following the turning on and off of the steam.

While I have referred to a hygrostat for use in controlling the emission of water vapor, it will be understood that other forms of regulating instruments may be used, such as a dew-point thermostat, a wet bulb thermostat, etc.

I have described the apparatus in connection with its use for evolving water vapor. It should be understood, however, that the apparatusrwith slight modifications can be used as an evaporator in many commercial processes.

Many forms of the apparatus other than that shown in the drawing will suggest themselves to those skilled in the art, and I do not wish to be limited except as indicated in the appended claims.

I claim:

l. In combination, a pan, a pipe having closely adjacent, vertically projecting fins thereon mounted horizontally within said pan, means for automatically maintaining a fixed level of water in said pan at such height that a substantial portion of said pipe and fins project above the water when heat is not being supplied to the pipe, side walls for closing otherwise open ends of the spaces between adjacent fins, and means for providing a controlled supply of heat to said pipe.

2. In combination, a container, a steam pipe located horizontally therein, a plurality of vertical, closely adjacent heat exchange elements mounted on and encircling said pipe, means clos,- ing the otherwise open ends of the spaces between adjacent heat exchange elements, automatic means for maintaining a substantially constant level of water in said spaces at such'height that a substantial portion of said pipe and heat exchange elements project above the water, and walls extending above said elements, thereby providing a coniined space above said elements and above the level of water in said spaces.

FRANK E. P. KLAGES.

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