US1993129A - Autodefrosting refrigeration apparatus - Google Patents

Description

March 5, 1935. BAlRD I AUIODEFROSTING REFRIGERATING APPARATUS Filed July 19, 1932 [nuenimj U/illz'am f Baird his (liiorney 9 Patented Mar. 5, 1935 I PATENT oFFicE AUTODEFBOSTIN G REFRIGEBATDTG APPARATUS William F. Baird, Lexington, Mass. Application July 19, 1932, Serial No. 623,309

24 Claims.

The present invention relates to the art of refrigerating, more particularly to refrigerating apparatus of the absorption type, and still more particularly to refrigerating apparatus of the absorption type wherein fluids inert with respect to the refrigerants used are employed to maintain pressures uniformthroughout the refrigerating apparatus.

A phenomenon observed in all refrigerating apparatus. during use is the formation in progressive accumulation of frost by the desublimation of water vapor from the air surrounding the refrigerating apparatus, and its deposition upon those portions of the refrigerating apparatus which contain refrigerants at temperatures below the freezing point of water. Such frost formation in progressive accumulation upon those portions of refrigerating apparatus located in spaces to be refrigerated is always objectionable, inasmuch as the heat insulating properties of such coatings of frost seriously reduce the refrigerating efiiciency of the refrigerating apparatus by diminishing the rate of transfer of heat from the spaces to be refrigerated to the refrigerants, but is nowhere -more objectionable than in the types of domestic refrigerating apparatus wherein the rate of frost formation in progressive accumulation is particularly rapid duev to the content of water vapor in the air surrounding the heat absorbing portions of the refrigerating'apparatus maintained at high'values by the continuous evaporation of moisture from foodstuffs within the spaces being refrigerated. So thick may and do become the coatings of frost upon the evaporators of such refrigerating apparatus, and so diminished may and do become the rates of transfer of heat to the evaporators from their surroundings, that the temperatures of the spaces being refrigerated rise, while the temperatures of the refrigerants within the evaporators fall; so that from time to time the operation of the refrigerating apparatus must be discontinued temporarily to permit the evaporators and their surroundings, the spaces being refrigerated, to warm up to extents sufficient to effect the meltings of the coatings of frost; or the removal of the coatings of frost must be effected either by some means of local heating of the surfaces of the evaporators, as for exam ple by the passage of suitable amounts of electricity through resistance coils in good thermal contact with the surfaces of the evaporators, or by some mechanical means of detaching the coatings of frost. All of these methods of dealing with the problem of the formation of coatings of frost possess serious disadvantages: the first method whereby the spaces wherein refrigeration is effected are permitted to become heated to temperatures well above the freezing point of water and are subsequently recooled causes spoilage of foodstuffs; the second method whereby the surfaces of the evaporators are subjected to localized heating requires expenditures of energy for purposes other than that of refrigerating; and the third method whereby the coatings of frost are detached from the surfaces of the evaporators by mechanical means cannot readily be utilized in the types of refrigerating apparatus used for domestic purposes.

The principal object of my invention is to effeet the defrosting of the evaporators of refrigcrating apparatus in the regular course of their operation. Another object of my invention is to effect the defrosting of the evaporators of re frigerating apparatus without seriously interfering with the refrigerating of the spaces being refrigerated, i. e., without causing wide temperature variations within the spaces being refrigerated. A third object of my invention is to effect the defrosting of the evaporators of refrigerating apparatus before the coatings of frost become so thick that they constitute real hindrances to the transference of heat from the spaces being refrigerated to the evaporators, and hence to the refrigerants within the evaporators. A fourth object of my invention is'to effect the defrosting of the evaporators of refrigerating apparatus without any expenditure of energy additional to that required for the purposes of refrigerating the spaces wherein the evaporators are located.

The attainment of these and other objects of my invention, and the advantages attendant upon the use of my invention will become apparent when consideration is given to the following description together with the accompanying drawing which forms a part of the specification wherein Fig. 1 is a diagrammatic cross-section of one form of refrigerating apparatus, a constant-pressure absorption refrigerating apparatus, embodying my invention in its preferred form, and Figs. 2, 3, and 4 are diagrammatic cross-sections of my invention considered apart from the refrigerating apparatus as a whole, and at various stages of its operation.

In Fig. 1, reference character 1 designates a generator shell divided into the principal generator chamber 2 and the auxiliary generator chamber 3 by means of the partition 4. A chimney or flue extends axially and concentrically through the generator shell 1, and is arranged to 56 x be heated by any suitable means such as, for instance inthis drawing, the burner 6. ,A thermosyphon or vapor lift 7 communicates with-the upper portion of the main generator chamber 2, extends downwardly, parallel with and external to the generator shell 1 passes through the generator shell 1 into the auxiliary generator chamber 3, and extends downwardly therein, being provided with one or more lateral apertures 8 and with an open lower end.

By means of the vapor conduit 9, communication is established between the upper portion of the main generator chamber 2 and the lower portion of the rectifier chamber 10. The rectifier chamber 10 encloses a leg of the U-shaped liquid reservoir 14 with the open end of which it is in communication. Arranged upon the leg of the U-shaped liquid reservoir 14 enclosed within the rectifier chamber 10 is a series of radiating fianges or fins which serve as bafiles to impedethe fiow of the vapor phase within the rectifier chamber 10 and to effect the condensation of the more readily condensable portion of the distillate from the main generator chamber 2. Communicating with the upper portion of the rectifier chamber 10 is a condenser tube 12 whose other end opens into the second or right leg of the U- shaped liquid reservoir 14. This condenser tube is formed into a V and is provided with a condenser jacket 13 through which cooling water cirwhites to effect the condensation to liquid of the vapor of the refrigerant.

Communicating with the lower part of the U- shaped liquid reservoir 14 is a conduit 16 which passes into and extends within the larger conduit 17, passes therefrom into a gas-and-vapor heatexchanger 18, lying-therein substantially parallel to the tubes 20, passes therefrom into the conduit 21; and terminatesin an open end withinthe upper part of the evaporator 22. The evaporator capillary ports 46 while a gas vent conduit 15 establishes communication between the upper portion of the closed right leg of the U-shaped liquid reservoir 14 and the space 19 of the gas- .and-vapor heat-exchanger 18 The right header chamber of the gas-andvapor heat-exchanger 18 communicates with the upper portion of the chamber of the evaporator 22 by means of the conduit 21 while the space 19 of the gas-and-vapor heat-exchanger 18 communicates with the lower portion of .the chamber of the evaporator 22 by means of the conduit 25.

-The left header chamber of the gas-and-vapor heat-exchanger 18 communicates with the upper portion of the chamber of the absorber 27 while the space 19 of the gas-and-vapor heat-exchanger communicates with the lower portion of the chamber of the absorber 2'? by means of the conduit 2e.

The absorber 27, a closed cylindrical shell wherein are posited a series of disks 33 provided with apertures 34, which may be similar to the disks 23 in the evaporator 22, is in communication with the gas-and-vapor heat-exchanger by means of the conduits 17 and 26 as heretofore described. The absorber is likewise in communication with the main generator 2 and with the auxiliary generator chamber 3 by means presently to be described.

The absorber 27 is provided with external encircling cooling coils 35 in good thermal contact therewith wherein water, entering at 37, passes therethrough and out by conduit 36. Conduit 36 communicates with the Water jacket 13, through which the water flows to leave by conduit 38, so that the supply of water which serves to remove from the absorber the heat of absorption of the refrigerant by the absorbing liquid also serves to remove from the vaporized refrigerant passing through the rectifying chamber 10 its heat of vaporization.

From the bottom of the absorber 27, a conduit 31 establishes communication with the auxiliary generator chamber 3. A conduit 30 connects the lower portion of the main generator chamber 2 with one end of a liquid heat-exchanger jacket 29 through which extends the conduit 31. A conduit 28 connects the other end of the jacket 29 with the upper portion of the chamber of the absorber 27.

These elements and their modes of connection and of communication comprise the refrigerating apparatus proper. In order that this apparatus shall effect refrigerating action with the minimum of frosting of the evaporator 22, means for effecting a certain relative intermittency of refrigerating action must be introduced therein; and one embodiment of my invention for effecting suchrelative intermittency of refrigerating action will now be described.

Within the upper portion of the chamber of the evaporator 22 and attached to the evaporator shelleby some highly effective thermal insulator inert to the refrigerant employed and of minimum cross-section is posited a receptacle or reservoir 39 provided with a conduit 43 forming with conduit 42 and their common header 40 a syphon with an outlet at 41. The conduit 42 may be, and preferably'will be, given a lateral horizontal extension before being turned up, as at 41, in order that there may always be maintained in the conduit 42 a quantity of liquid sufllcient to' fill its vertical portion. The conduits 42 and 43 must be of bores sufliciently great to realize'the elimination of all effects of capillarity and surface tension, and conduit 42 will preferably have a diameter considerably greater than that of conduit 43. The top of the syphon gas lock 40 may or may not exceed in height the top of the reservoir 39, but the floor of its cham ber must be located at a level lower than that of the top of the reservoir 39. Both of the conduits 42 and 43 and the syphon gas lock 40 may production of the desired relative intermittency of refrigerating action as will be hereinafter explained.

The. operation of the refrigerating system equipped with my invention is initially substantially as follows: a refrigerant such as ammonia dissolved in an absorptive liquid such as water is contained in the main generator chamber 2 and in the auxiliary generator chamber 3. -Ammonia vapor is evolved from the liquids in both of the generator'chambers by the application of heat thereto. The ammonia vapor formed in the auxiliary generator chamber 3 passes into the conduit 7 through the ports 8 and transports to the main generator chamber 2 at the higher level quantities of the liquid in the auxiliary generator chamber 3.

The vapor from the two generator chambers 2 and 3 consisting of ammonia and water vapor passes through the conduit 9 to the rectifying chamber 14 wherein the water vapor is precipitated by condensation and runs back into the main generator chamber 2. The ammonia gas, substantially free from water vapor, passes into the conduit 12 wherein it is condensed to liquid ammonia by the removal of its heat of vaporization by the cooling water in the water jacket 13, and the so-formed liquid ammonia runs into the right leg of the U-shaped liquid reservoir 14 which becomes filled up to the level of the end of the conduit 16 overhanging the reservoir 39 posited in the upper portion of the'chamber of the evaporator 22. While the liquid ammonia in the left leg of the U-shaped liquid reservoir 14 is of a temperature sufliciently low to be effective in cooling the vapors passing through the rectifying chamber 10 and in condensing substantially all of the water vapor to liquid water, because it was originally condensed and cooled in the conduit 12 to a temperature substantially that of the cooling water in the water jacket 13, yet its temperature is insufficiently low to effect the condensation within the rectifying chamber 10 to liquid ammonia of any appreciable amount of ammonia vapor; and during certain phases of the operation of the refrigerating apparatus equipped with my invention, a certain amount of ammonia vapor may pass uncondensed through the conduit 12 into the right leg of the U-shaped liquid reservoir 14, thence by way of conduit 15 to the space 19 of the gas-and-vapor heat-exchanger 18, finally to be reabsorbed in the absorber 2''! after passing through the conduit 26. The liquid ammonia passes from the U-shaped liquid reservoir 14 through the conduit 16 to the reservoir 39 posited within the upper portion of the chamber of the evaporator 22.

' When the levels of the liquid ammonia in the legs of the U-shaped liquid reservoir 14 become sufliciently high, liquid ammonia becomes discharged from the end of the conduit 16 and drips into the reservoir 39. From the reservoir 39, some of the liquid ammonia evaporates into a gas inert with respect to the ammonia, such as hydrogen gas, which is introduced into the chamber of the evaporator 22 through the conduit 21. This evaporation, serves to cool the liquid ammonia remaining within the reservoir 39 to a 1 temperature below those of its surroundings, and

serves also to effect some refrigerating action within the chamber of the evaporator 22, and hence within the space being refrigerated, desighated diagrammatically in the drawing by the broken lines 45.

When the reservoir 39 and its contents have become sufliciently chilled, the further discharge of liquid ammonia thereinto accumulates until be level of the liquid ammonia becomes as high is the highest portion of the floor of the syphon to but not greater than the pressure of the hydrogen gas within the chamber of the evaporator 22. Such hydrogen gas will, of course, be saturated with ammonia vapor at a pressure equal to the vapor pressure of the liquid ammonia within the reservoir 39 at whatever temperature it may be, so that the total pressure of hydrogen gas and ammonia vapor within the gas lock 40 will be substantially equal 'tobut not greater than the total pressure of hydrogen gas and ammonia vapor withinthe chamber of the evaporator 22. Additional amounts of liquid ammonia discharged into the reservoir 39 will now cause the discharge of liquid ammonia in corresponding amounts from the outlet 41 onto the plates 23 whose temperatures are higher than is that of the reservoir 39 and its liquid contents. At the first discharge of liquid ammonia onto the plates 23, the pressure of the ammonia vapor within the chamber of the evaporator 22 and the spaces communicating therewith becomes greater than the vapor pressure of the liquid ammonia in the reservoir 39, and the total pressure of hydrogen gas and ammonia vapor within the chamber of the evaporator becomes proportionately greater. This suddenly created pressure is transmitted to and exerted upon the surfaces of the liquid ammonia in the reservoir 39 and in the conduit 42 at the outlet 41 too quickly for the attainment of equilibrium between the partial pressure of the ammonia vapor in the hydrogen gas and the vapor pressure of the liquid ammonia in the reservoir 39 by condensation to the liquid state of the requisite quantity of ammonia vapor from the mixture of hydrogen gas and ammonia vapor. Consequently, the total pressure of the mixture of hydrogen gas and ammonia vaporexerted upon the surfaces of the liquid ammonia in the reservoir 39 and in the conduit 42 at the outlet 41 is greater than the pressure of the hydrogen gas and the vapor pressure of liquid ammonia in the siphon gas lock 40, liquid ammonia is forced up into the siphon gas lock 40, the siphoning stream is formed as is shown in Fig. 3, and the liquid ammonia is siphoned out of the reservoir 39 onto the plates 23 producing considerable refrigerating action within the space designated diagrammatically by the broken lines 45. It is obvious that so long as the differential pressure between total pressure exerted upon the surfaces of the liquid ammonia in the reservoir 39 and in the conduit 42 at the outlet 41 and the total pressure exerted upon the surfaces or surface of liquid ammonia within the conduits 42 and 43 and within the siphon gas lock 40 is equal to or greater than the hydrostatic pressure of the column of liquid ammonia in the conduit 42, the siphoning stream will continue to flow uninterruptedly until the reservoir 39 has been-emptied. In order that all of the liquid ammonia siphoned out of the reservoir 39 onto the plates 23 shall evaporate within the chamber of the evaporator 22, it is highly desirable that the plates 23 shall have a liquid carrying capacity somewhat in excess of the capacity of the reservoir 39.

In the chamber of the evaporator 22, the so formed mixture of hydrogen gas and ammonia vapor has a density greater than that of the relatively pure hydrogen gas which enters the chamber of the evaporator 22 through the conduit 21 at a pressure equal to the total pressure of the mixture of hydrogen gas and ammonia vapor, and hence this mixture flows downwardly through the chamber of the evaporator 22, through the conduit 25 into the space 19 of the gas-and-vapor heat-exchanger 18, and thence through conduit 26 into the lower part of the chamber of the absorber 27.

In the chamber of the absorber 2'7, the mixture of hydrogen gas and ammonia vapor comes into contact with the weak absorption liquid which enters the chamber of the absorber 27 through the conduit 28 and is distributed over the disks 33. The absorption liquid absorbs the ammonia gas, and in this process of absorption heat is generated, which is removed by the cooling'water passing through the coils 35 encircling the absorber 27 in good thermal contact therewith. -The hydrogen gas is not absorbed, and it passes from the chamber of the absorber 2'7 through the conduit 17 into the left header chamber of the gas-and-vapor heat-exchanger 18. From this header chamber, the hydrogen gas passes through the tubes 20 to the right header chamber, becoming cooled during its passage therethrough; and thence through conduit- 21 into the upper portion of the chamber of the evaporator 22. In the gas-and-vapor heat-exchanger 18, the liquid ammonia in conduit 16 and the hydrogen gas passing through the tubes 20 are precooled before entering the chamber of the evaporator- 22 by the cold mixture of hydrogen gasand ammonia vapor which has just left the chamber of the evaporator 22 and has just occupied the space 19 of the gas-and-vapor heat-exchanger 18.

The strong solution of ammonia in water formed in the chamber of the absorber'27 passes therefrom throughconduit 31 to the auxiliary generator chamber 3, wherefrom it is conveyed through the vapor lift conduit '7 to the main generator chamber 2, as previously described. Here a large percentage of the ammonia is driven out of solution by means of heat, and the thus formed weak solution passes from the lower portion of the main generator chamber 2 through the conduit 30 into the liquid-and-liquid heatexchanger jacket 29, wherein the hot weak liquid is cooled by the strong cool solution passing in the conduit 31 which it serves to heat up. From the liquid-and-liquid heat-exchanger jacket 29, the weak solution passes through the conduit 28 losing in its passage therethrough additional quantities of heat by radiation to the coils 35 containing flowing cooling water, and by other-forms of heat dissipation, and is finally discharged into the upper portion of the chamber of the absorber 27 Thus far has been described the operation of the refrigerating apparatus under ideal conditions, i. e., in the absence of a coating of frost upon the evaporator. Now it has already been pointed out that so long as the sum of the pressure of the hydrogen gas and the vapor pressure of liquid ammonia within the syphon gas lock in less than the sum of the partial pressures of the hydrogen gas and the ammonia vapor within the chamber of the evaporator 22 by the amount of the hydrostatic pressure of the column of liquid ammonia filling the conduit 42, the syphoning stream will be maintained, and liquid ammonia will continue to be discharged from the outlet 41 as fast as it is fed into the reservoir 39, the levels of the liquid ammonia then being as shown in Fig. 3. But the discharge of liquid ammonia 'onto the plates 23 from the outlet 41 results in refrigerating action which eventually lowers the temperature of the evaporator 22 to a value less than that of the temperature of the liquid ammonia remaining in the reservoir 39 thermally insulated from the evaporator 22; and any liquid ammonia which might remain upon the plates 23 due to local undercooling would then have a vapor pressure far less in amount than the vapor pressure of the liquid ammonia at a higher temperature within the reservoir 39. Consequently, the sum of the pressures of the hydrogen gas and the vapor pressure of the liquid ammonia in the syphon gas lock 40 isthen greater'than the sum of the partial pressures of the hydrogen gas and the ammonia vapor within the chamber of the evaporator 22, and the syphoning stream becomes broken by'the expansion of the mixture of hydrogen gas and ammonia vapor within the syphon gas lock 40, as shown by Fig. 4.

If now the transfer of heat from the space within the lines being refrigerated to the interior of the evaporator 22. has not been seriously lessened by the formation during the refrigerating action of a coating of frost on the outside wall of the evaporator 22, there may occur one or more repetitions of the syphoning cycle consisting of the accumulation of a substantial portion of the refrigerant within the reservoir 39, the formation of the syphoning stream, the'discharge of the liquid refrigerant onto the plates 23, the continuation of flow of the syphoning stream, and the subsequent eventual disruption of the syphoning stream. But, dependent upon the relative sizes and interrelations of the various parts of the refrigerating apparatus, upon the quantity of refrigerant used, upon the frequency of occurrence of the refrigerating cycle, upon the density of water vapor in the space being refrigerated, and upon various other factors, the evaporator 22 will eventually become coated with a layer of frost the progressive thickening of which decreases directly the rate of transfer of heat from thespace being refrigerated to the refrigerant Within the evaporator '22. Under these conditions, the evaporator 22 and the plates 23 will eventually become cooled to very low temperatures, lower than the temperature of the liquid ammonia in the reservoir 39 thermally insulated from the evaporator 22, while the temperature of the space being refrigerated will increase as heat is transferred into the space being refrigerated from its surroundings, and is unable to pass sufficiently rapidly to the evaporator 22 through its heat insulating coating of frost. When the evaporator 22 and the plates 23 have been cooled to such low temperatures, the syphoning stream will not be formed upon the initial drip of liquid ammonia onto the plates 23 from the outlet 41 by the sudden generation of a pressure of ammonia vapor, but the refrigerant will continue to drip upon the plates as rapidly as it is fed into the reservoir 39 as is shown in Fig. 2. The total amount of refrigerant in the refrigerating apparatus and the rate of its distillation will be so determined that the rate of flow of the liquid refrigerant from the outlet 41 when the reservoir 39 is filled will be insufficient to maintain a rate no inert gas entrapped within the syphon gas look, but the chamber of the syphon gas lockof refrigerating equal to the rate of transfer of heat from the space being refrigerated to the evaporator 22. HenceIthe temperature of the evaporator will slowlyrise, and the increasing temperature of the space being refrigerated will 'cause the coating of frost upon the'outside wall of the evaporator 22 to become melted, thus per-- mitting heat to become more readily transferred to the evaporator 22, eventually the syphoning stream will be formed anew and the refrigerating cycle will be repeated.

The relative sizes and interrelations of the parts of the syphon and reservoir and of the refrigerating apparatus and the amount of the refrigerant to be used will have to be determined with considerable nicety, but it is obvious that such co-adjustment of the sizes of the parts and of the amount of refrigerent is a matter of detail 27. Such arecirculation of ammonia vapor will,

however, favor the removal of the coating of frost from the outside of the evaporator. Similarly, the condenser conduit 12 and water jacket 13 must have condensing capacity and efliciency adequate for the rapid condensing to the liquid state within a short duration of time of a large quantity of ammonia vapor, rapidly evolved from the generator chambers 2 and 3, for otherwise a certain quantity of ammonia vapor may escape condensation to be bypassed through the conduit 15, the space '19, and the conduit 26 back to the absorber 27. Likewise, it is obvious that the precise type of syphon herein illustrated in the drawing may be replaced by a syphon whose gas lock and conduits are posited within the reservoir 39, while thedischarge conduit passes through the wall of the reservoir 39 into an overflow trough attached to the exterior of the reser-,

voir 39. Indeed, it is also obvious that such a reservoir-syphon arrangement is only one'means for efiecting a relative intermittency of refrigerating action, and that such a reservoir-syphon arrangement may be replaced by a reservoir provided with an outflow valve whose operation and regulation are effected by means sensitive to differences of temperature between that of the space being refrigerated and that of the interio of the evaporator. n The principle of which this invention is a concrete embodiment, expressed in broad terms as the regulation in a refrigerating apparatus of the rate of refrigerating by the rate of transfer of heat from the space being refrigerated to the heat absorbing portion of the refrigerating apparatus, and less broadly as the temporary isolating of a substantial portion of the refrigerant from the refrigerating cycle whenever the rate of transfer of heat from the space being refrigerated to the.

heat absorbing portion of the refrigerating apparatus becomes appreciably diminished, can be applied equally well in the operation of direct compression refrigerating apparatus employing refrigerants which are liquefied in the refrigerating cycle. In such cases, there would be of course would serve to facilitate the recurring formations and disruptions of the syphoning stream.

Having thus described my invention, I claim: 1. That improvement in the art of refrigeration by the aid of refrigerating apparatus containing a refrigerant fluid which consists in isolating from the refrigerating cycle in the liquid state. a substantial portion of the refrigerant fluid whenever the rate of transfer of heat from the space being refrigerated to the heat absorbing portion of the refrigerating apparatus becomes appreciably diminished,'and in returning to the refrigerating cycle'the isolated portion of the refrigerant fluid whenever the rate of transfer of heat from the space being refrigerated to the heat absorbing portion of the refrigerating apparatus has thereafter appreciably increased.

2. That improvement in the art of refrigeration by the aid of absorption refrigerating apparatus containing arefrigerant fluid which'con sists. in isolating from the refrigerating cycle in the liquid state a substantial 'portion of the refrigerant fluid whenever the rate of transfer of heat from the space being refrigeratedto the heat absorbing portion of the absorption refrigerating apparatus becomes diminished, and in automatically returning to the refrigerating cycle the isolated portion of the refrigerant fluid whenever the rate of transfer of heat from the space being refrigerated to the heat absorbing portion of the absorption refrigerating apparatus has thereafter appreciably increased.

'3. lifhat improvement in the art of refrigeration by the aid of refrigerating apparatus coritaining a refrigerant fluid and an additional fluid for equalizing pressures throughout the refrigerating apparatus which consists in isolating from the refrigerating cycle in the liquid state" a substantial portion of the refrigerant fluid whenevert the rate of transfer of heat from the space -.being refrigerated to the heat absorbing portion of the refrigerating apparatus becomes appreciably diminished, and in returning to the refrigparatus of the refrigerant fluid becomes abnor-' mally low, and in returning to the refrigerating cycle the isolated portion of. the refrigerant fluid whenever the partial pressure within the heat absorbing portion of the refrigerating apparatus of the refrigerant fluid has thereafter appreciably increased.

5. That improvement in the art of refrigeration by the aid of refrigerating apparatus con-' taining a refrigerant fluid and having a liquid evaporator forming a heat absorbing portion which consists in collecting in the liquid state within the regionbeing refrigerated but-insulated therefrom a substantial portion of the re frigerant fluid whenever therate of transfer of appreciably heat from the space being refrigerated to the liquid evaporator becomes appreciably diminished, and in discharging into the liquid evaporator the collected portion of the refrigerant fluid whenever the rate of transfer of heat from the space being refrigerated to the liquid evaporator has thereafter appreciably increased.

6. That improvement in the art of refrigeration by the aid of absorption refrigerating apparatus containing a refrigerant fluid and having a liquid evaporator forming a heat absorbing portion which consists in collecting in the liquid state within the region being refrigerated but insulated therefrom a substantial portion of the refrigerant fluid whenever the rate of transfer of heat from the space being refrigerated to the liquid evaporator becomes appreciably diminished, and in automatically discharging into the liquid evaporator the collected portion of the refrigerant fluid whenever the rate of transfer of heat from the space beingrefrigerated to the liquid evaporator has thereafter appreciably increased.

7. That improvement in the art of refrigeration by the aid of refrigerating apparatus containing a refrigerant fluid and having a liquid evaporator forming a heat absorbing portion which consists in collecting in the liquid state within the region being refrigerated but insulated therefrom a substantial portion of the refrigerant fluid whenever the pressure of the refrigerant fluid within the liquid evaporator becomes appreciably diminished, and in discharging into the liquid evaporator the collected portion of the refrigerant fluid whenever the pressure of the refrigerant fluid within the liquid evaporator has thereafter appreciably increased.

8. That improvement inthe art of refrigeration by the aid of absorption refrigerating apparatus containing a refrigerant fluid and having a liquid evaporator forming a heat absorbing portion which consists in collecting in the liquid state within the region being refrigerated but insulated therefroma substantial portion of the refrigerant fluid whenever the pressure of the refrigerant fluid within the liquid evaporator becomes appreciably diminished, and in automatically discharging into the liquid evaporator the collected portion of the refrigerant fluid whenever the pressure of the refrigerant fluid within the liquid evaporator has thereafter appreciably increased.

9. That improvement in the art of refrigeration by the aid of refrigerating apparatus containing a refrigerant fluid and an additional.

fluid for equalizing pressures throughout the refrigerating apparatus and having a liquid evaporator forming a heat absorbing portion which consists in collecting in the liquid state within the region being refrigerated but insulated therefrom a substantial portion of they refrigerant fluid whenever the partial pressure of the refrigerant fluid within the liquid evaporator becomes appreciably diminished, and in discharging into the liquid evaporator the collectedportion of the refrigerant fluid whenever the partial pressure of the refrigerant fluid within the liquid evaporator has thereafter appreciably increased.

10. That improvement in the art of refrigeration by the aid of refrigerating apparatus containing a refrigerant fluid and an additional fluid for equalizing pressures throughout the refrigerating apparatus and having a liquid evaporator forming a heat absorbing portion which consists in collecting in the liquid state within the liquid evaporator but insulated therefrom a substantial portion of the refrigerant fluid whenever the rate of transfer of heat from the space being refrigerated to the liquid evaporator becomes appreciably diminished, and in automatically discharging into the liquid evaporator the collected portion of the refrigerant fluid whenever the rate of transfer of heat from the space being refrigerated to the liquid evaporator has thereafter appreciably increased.

11. That improvement in the art of refrigeration by the aid of refrigerating apparatus containing a refrigerant fluid and an additional fluid for equalizing pressures throughout the refrigerating apparatus and having a liquid evaporator forming a heat absorbing portion which consists in collecting in the liquid state within the liquidevaporator but insulated therefrom a substantial portion of the refrigerant fluid whenever the partial pressure of the refrigerant fluid within the liquid evaporator becomes substantially equal to the vapor pressure of the refrigerant fluid being collected, and in automatically discharging into the liquid evaporator the collected portion of the refrigerant fluid whenever the diflerential of pressure between the partial pressure of the refrigerant fluid in the liquid evaporator and the vapor pressure of the col- I lected portion of the refrigerant fluid has there-' after appreciably increased.

12. That improvement in the art of refrigeration by the aid of refrigerating apparatus containing a refrigerant fluid and an additional fluid for equalizing pressures throughout the refrigerating apparatus and having a liquid evaporator forming a heat absorbing portion which consists in collecting in the liquid state within the liquid evaporator but insulated therefrom a substantial portion of the refrigerant fluid whenever the temperature of the liquid evaporator becomes substantially equal to the temperature of the refrigerant fluid being collected, and in automatically discharging into the liquid evaporator the collected portion of the refrigerant fluid whenever the differential of temperature between the temperature of the liquid evaporator and the temperature of the collected portion of the refrigerant fluid has. thereafter appreciably increased.

13. A refrigerating apparatus comprising a.

generator, a condenser, an evaporator, an absorber, conduits connecting the aforesaid elements to form a cycle for the circulation of the refrige'rant through the said generator, condenser,

evaporator and absorber, and means contained transfer of heat from the space being refrigerated to the evaporator has thereafter appreciably increased.

14. A refrigerating apparatus comprising a generator, a condenser, an evaporator, an absorber, conduits connecting the aforesaid elements to form a cycle for the circulation of the refrigerant through the said generator, condenser evaporator and absorber, a reservoir contained within the evaporator and thermally insulated therefrom for receiving liquid refrigerant, and means for effecting the discharge from the reservoir of its contents when the rate of transfer of heat from the space being refrigerated to the evaporator is large and for arresting the discharge from the reservoir of its contents when the rate of transfer of form a cycle for the circulation of the refrigerantthrough the said generator, condenser, evaporator and absorber, a reservoir contained within the evaporator and. thermally insulated therefrom for receiving liquid refrigerant, and means responsive to changes in pressure upon the liquid refrigerant for efiecting and for arresting the discharge from the reservoir of its contents.

16. A refrigerating apparatus of the equalizedpressure absorption type comprising a generator, a condenser, an evaporator, an absorber, conduits connecting the aforesaid elementsto form a cycle for the circulation of the refrigerant through the said generator, condenser, evaporator and absorber, and means contained within the evaporator to eifect the isolation from the cycle of a sub-- stantial portion of the refrigerant whenever and.

while the rate of transfer of heat from the space being refrigerated to the evaporator becomes appreciably diminished and to efi'ectthe' return to the cycle of the isolated portion of the refrigerant whenever the rate of transfer of heat from the space being refrigerated to the evaporator has thereafter appreciably increased.

17. A refrigerating apparatus of the equalizedpressure absorption type comprising a generator, a condenser, an evaporator, an absorber, conduits connecting the aforesaid elements to form a cycle for the circulation of the refrigerant through the said generator, condenser, evaporator, and absorber, a reservoir contained within the evaporator and thermally insulated therefrom for receiving liquid refrigerant, and communication with the reservoir at ;a point near its bottom a syphon adapted to retain during use a quantity of a noncondensing gas and provided with a horizontal extension of its outlet leg of capacity greater than the capacity of the outlet 'leg and having an upward discharge outlet.

.4 18. A refrigerating apparatus of the equalizedpressure absorption-type comprising a generator, a condenser, an evaporator, an absorber, conduits connecting the aforesaid elements to form a cycle for the circulation of the refrigerant through the said generator, condenser, evaporator, and absorber, a reservoir contained within the evaporator and thermally insulated therefrom for receiving liquid refrigerant, and an inverted syphon posited within and attached to the reservoir through the wall of which the discharge leg of the syphon passes downwardly into a spill-trough afllxed to the outside of the reservoir.

19. An autodefrosting evaporator for refrigerating systems comprising a shell provided with a plurality of ports and with plates, means containedwithin the evaporator and thermally insulated therefrom for receiving a quantity of liquid refrigerant, and means responsive to variations of pressurewithin the evaporator for effecting and for arresting the delivery to the evaporator plates of the said quantity of liquid refrigerant.

20. An autodefrosting evaporator for refrigerating systems comprising a shell provided with a I plurality of ports and with plates, a reservoir contained within the evaporator and thermally insulated therefrom for receiving a quantity of liquid refrigerant less than the capacity of the plates, and means responsive to variations of pressure within the evaporator for effecting and for arresting the delivery to the evaporator plates of the said quantity of liquid refrigerant. r

21. An autodefrosting evaporator for refrigerating systems comprising a shell provided with a plurality of ports and with plates, a. reservoir contained within the evaporator and thermally insulated therefrom for receiving liquid refrigerant, and an inverted syphon comprising an inlet leg communicating with the reservoir at a point near tion type comprising a shell provided with a plu-' rality of ports and with plates, a reservoir contained within the evaporator and thermally insulated therefrom for receiving liquid refrigerant, and in communication with the reservoir at'a point near its bottom a syphon adapted to retain during use aquantity of a non-condensing gas and provided with means for maintaining its" outlet sealed with liquid under all conditions of operation of the evaporator.

23. An autodefrosting evaporator for refrigerating systems of the equalized-pressure absorp tion type comprising a shell provided with a plurality of ports and with plates, a reservoir contained within the evaporator and thermally insulated therefrom for receiving liquid refrigerant, and in communication with the reservoir at a point near its bottom an inverted syphon whose legs communicate at their upper ends with a gasretaining chamber and whose outlet leg discharges upwardly into a second reservoir .of capacity greater than the outlet leg and forming an "tension of the outlet leg.

24. An autodefrostingevaporator for refrigerating systems of the equalized-pressure absorption type comprising a shell provided with a plurality of ports and with plates, a reservoir contained within the evaporator-and thermally insuevaporator. v

' WILLIAM F.- BAIRD.

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