US2153020A

US2153020A - Diffusion refrigerating machine

Info

Publication number: US2153020A
Application number: US151777A
Authority: US
Inventors: Maiuri Guido
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-04-30
Filing date: 1937-07-03
Publication date: 1939-04-04
Anticipated expiration: 1956-04-04

Description

April 4, 1939. G MA|UR| 2,153,020

DIFFUS ION REFRIGERATING MACHINE Filed July 3, 1937 4 Sheets-sheet l fwwwfor UIDD MHIURI FITTORNEY April 4, 1939. G MA|UR| 2,153,020

I DIFFUSION REFRIGERATING MACHIVNE Filed July 3, 1957 4 Sheets-Sheet 2 I L i II I I I 1 GUIDO MFHURI FTTTORNEY April 4, G. 'MA|UR| 2,153,020

DIFFUSION REFRIGERATIiIG MACHINE Filed Jul 3, 1937 4 Sheets-Sheet s I I? m I f 1 x"; El Z, 'l f I I Fang V 6- I 7 a ,fiwenfor Guuoo MHIURI FITTORNEY April 4,- 1939. G, MAIUR] 2,153,020

DIFFUSION REFRIGERATING MACHINE Filed July 3, 1937 4 Sheets-Sheet 4 fvweniar GUI 00 MPH URI HTTORNE Patented Apr, 4, 1939 Application July 3, 1937, Serial No. 151,777 In Great Britain April 30, 1937 18 Claims.

This invention relates to diffusion refrigerating machines wherein cold is produced over a wide range of temperatures, preferably-extending from a very low temperature, by the evaporation of a refrigerant under increasing partial pressure.

By diffusion refrigerating machine is meant an absorption or resorption refrigerating machine wherein the refrigerant evaporates into and is absorbed from an atmosphere of inert gas.

Now to obtain a wide range of partial pressures of the evaporating refrigerant, extending from a low minimum partial pressure, and thus to obtain a wide range of refrigerating temperatures, the quantity of inert gas present in the evaporator of the diffusion refrigerating machine must be so limited that the maximum partial pressure of the refrigerant at least closely approaches the total pressure in the evaporator. A low minimum partial pressure of the refrigerant can be obtained by the inert gasbeing suppliedto theevaporator substantially freed from refrigerant vapour in the absorber. A low minimum temperature of evaporation can be ensured by precooling to the minimum temperature, the'inert gas, freed from refrigerant vapour, and also the liquidrefrigerant prior to admiss'ion of the gasto the liquid refrigerant in the evaporator, so that the initialevaporation under the minimum partial pressure with the accompanying low temperature can be preserved against being increased by the large quantity of refrigerant which would have to evaporated, merely to cool the arriving inert gas and liquid refrigerant.

Now the chief purpose of a refrigerating machine producing cold. along a range of "temperatures, as distinguished from at approximately a single temperature, is to cool fluids by contra- 4( flow heat-exchange with the evaporating refrigerant. The production of cold should therefore be as uniform in quantity as possible along the range of temperatures, as the quantity of contra-flowing fluid to be cooled must obviously remain uniform throughout'the range of heat-exchange.

Now with the same quantity of inert gas flowing from one end to the other of the evaporator and the mixture cigars ,and refrigerant vapour increasing in volume by evaporation of refrigerant, the quantity'of refrigerant which must be evaporated to increase the temperature of evapo ration by 1 C. by a corresponding increase of the partial pressure, is very small at low temperatures but increases rapidly with the temperature.

This increase of quantity of refrigerant evaporated to produce a variation of temperature of 1 C. depends also on the total pressure of inert gas plus refrigerant vapour in the evaporator.

A numerical example using ammonia as the 5 refrigerant shows that to increase the temperature from C. to 74 C. if one cubic metre of inert gas mixture is circulating per unit of time 5.66 grammes of ammonia have to be evaporated when the total pressure is 5 atmospheres o absolute. At the same total pressure, 63 grammes must be evaporated per cubic metre of gas mixture circulating, to increase the temperature of evaporation from --30 C. to -29 C.

. With a total pressure of 2 atmospheres abso- 15 late, to increase the temperature from -.-75 C.

to --74 C., 5.88 grammes of ammonia must evaporate per cubic metre'of gas mixture circulating, and to increase the temperature from -30 C. to .-29 0., 127 grammes of ammonia must evap- 20 orate.

As it is necessary to evaporate the. same amount .of ammonia in order to cool a. given amount of fluid one degree centigrade independently of the temperature, it is evident that a volume of gas 25 mixture in inverse proportion to the above given weights of ammonia evaporated should be circulated to keep theamount of cold produced substantially uniform throughout the range of temperatures. 30

' For instance to evaporate grammes of ammonia per hour per each degree 0. of variation of temperature (which would allow the cooling by one degree C. of 10 cubic metres of fluid such as nitrogen or'air per hour) the volume of gas mix- 35 ture to be circulated at various parts of the evaporator should be, with a total pressure of 5 atmospheres absolute, 1.59 cubic metres from 30 C. to --29 C. and 17.6 cubic metres from 75"- C. to 74 C. The volume of gas mixture 40 to be circulated should be with a total pressure of -2 atmospheres absolute, 0.79 cubic metre from -30 C. to -29 C. and 17.0 cubic metres from -75 C. to -'74 C.

The object of the present invention is to render 45 substantially uniform the production of cold along a wide range of temperatures in a diffusion refrigerating machine. This is efl'e'cted, according to the invention, by progressively divertin'g inert gas out of the evaporator of a dif- 50 fusion refrigerating machine, at a ratepermitting a uniform rate of evaporation per degree of increase of temperature throughout the flow of the inert gas within the evaporator. In otherwords, sufficient inert gas is progressively ex- 55 tracted from the evaporator to reduce the amount of inert gas remaining therein at all parts of r the evaporator traversed by inert gas, so that whereby the correctly proportioned progressive-' a uniform rate of evaporation of refrigerant along the evaporator will produce a uniform rate increase of the partial pressure and temperature.

The inert gas is progressively extracted from the evaporator by leaking through a series of holes into a space connected to the absorber and at a slightly lower pressure than the evaporator.

These-holes are preferably arranged in a helical row in the wall of a cylindrical evaporator,

ly decreasing leakage of inert gas can be predetermined by the steepness of pitch of the row and size andcloseness of the holes.

The decrease of inert gas circulation necessary to keep constantthe gradient of temperature is much larger at low. temperatures than at higher temperatures and for this reason the holes must be closer together or larger or both at the colder end of the evaporator and progressively at an increasing distance apart or smaller or both towards the less cold end.

The total pressure in the evaporator may be so limited that the maximum temperature of evaporation of the refrigerant is considerably lower than atmospheric temperature. For example, using ammonia as the refrigerant, the total pressure may be two atmospheres absolute.

-At the lower end of the range of partial presat a temperature of -20 'C. Incidentally at this part of the evaporator very little inert gas if any may be present as all or nearly all may have been already diverted, but this does not aflect the upper limitation of temperature as the latter depends upon the total pressure whether due to gas or vapour or both.

Asthe primary use of the machine is to cool fluids and for instance in cooling compressed air for obtaining liquid air or oxygen, the cooling is effected from atmospheric temperature, a suitable excess of cold should in such case be produced at 20 C. to cool the air from say +20 C. to say -l9 0. Below -19 C. the c001 ing is effected with but slight difference of temperature sufficient merely to effect heat transmission, by the cold produced along the range of temperatures from --20 C. to -71 C. To produce the excess of cold at -20i C. evaporation of the ammonia is continued by ebullitionunder the total pressure of 2 atmospheres absolute,

like in refrigerating machines having no inert,

erant from the inert gas which enters the absorber cold from the evaporator.

The diverted inert gas mixture is conducted in heat-exchange with the gas left in the evap- The weak liquor is thus rendered capable of absorbing'more refrigaisaoso orator, and may be led also in heat-exchange proximity with the gas coming from the absorber. The diverted gas mixture is sent to a convenient part of the absorber. It may be advantageous in some cases to keep separated the diverted inert gas mixtures of various proportions of gas and vapour and to conduct the various parts of the diverted gas mixture into parts of the absorber where the composition is similar.

constructional embodiments of diffusion refrigerating machines according to the invention are illustrated by way of example on the accompanying drawings, in which:

Fig. 1 is an elevation partly in section of an entire diffusion refrigerating machine.

Fig. 2 is a sectional elevation of the evaporator of the machine, on a larger scale than Fig. 1.

Fig. 3 is a sectional elevation of the absorber of the machine, on a larger scale than Fig. 1.

"Fig. 4 is a sectional elevation of a modified machine.

Referring more particularly to Figs. 1 to 3:

a. is the boiler of the refrigerating machine, heated by a gas burner b.

a is a horizontal cylindrical portion of the boiler a located at the level of and providing a wide expanse of upper surface of the liquid in the boiler. v

c is a rectifier extending upwards from the boiler a and cooled by an internal pipe coil to and from which water flows by connections c 0.

d is a condenser connected to the rectifier e.

e is an absorber.

j is an evaporator.

a is a pump delivering rich liquor, coming from the absorber e by a pipe 9 to one end of the outer tube It of a coiled tube heat-exchanger. .the other end of which latter is connected to the horizontal portion a of the boiler, by a pipe h Weak liquor leaves the boiler a by a pipe i which extends within the coiled outertube h of the heat-exchanger, from whence the pipe i passes provided with a stop cock F, to a precooler in the evaporator f, and thence the weak liquor passes to the absorber e, as described hereinafter.

The condenser d delivers liquid refrigerant, for instance ammonia, to the evaporator f by a pipe d Before entering the evaporating space in the evaporator j, the liquid refrigerant traverses a pipe coil 1 in the upper portion of the evaporator f wherein the liquid refrigerant is cooled approximately to the temperature reigning in such upper part of the evaporator. .The cooled liquid refrigerant is delivered, by a pipe In connected to the pipe coil j and branching into two branches k and It provided with stop cocks It k into the evaporator ,f at two levels.

M, the liquid refrigerant'overflows, from an an- I nular trough I, an annular weir l straddled by a wire gauze wick l, which distributes the liquid refrigerant on to pipe coils beneath. In the.

upper portion of the evaporator the respective pipe coils are the already mentioned pipe coil 1 wherein the liquidrefrigerant is cooled, and a second pipe coil m intercoiled therewith and connected to the weak liquor supply piper;

Owing to being cooled in the coil m before entering the absorber e, the weak liquor more readily absorbs refrigerant vapour coming from the evaporator I by a pipe f connecting the top of fie evaporator to the upper end of the absor r e.

The top of the absorber e is connected by a pipe e to a pipe coil 11 extending downwards within the evaporator f and opening into the evaporator at the bottom thereof. I I I Above the pipe coil n is an annular trough 0,

into which the branch pipe It delivers liquid refrigerant to overflow a weir o straddled by a wire gauze wick on to the pipe coil n. I

The absorber e and evaporator f are charged with inert gas, for instance nitrogen, which is driven by a fan e from the absorber 6 along the pipe 8 and pipe 0011 n into the evaporator f. The inert gas becomes refrigerated by the refrigerant evaporating on the pipe coil n, before being discharged into the lower end of the evaporator f.

' The lower portion of the evaporator f issur- I rounded by a jacket 9. with whichthe interior of the evaporator f communicates by a helical row of holes q. The jacket pl is connected by a pipe 1' with an annular space between the wall of the absorber e and, a cylindrical partition s in the absorber c. This annular space is closed at the top by the base of an annular trough t at the top of the absorber e and is open at the lower end whereby the annular space communicates with the space within the cylindrical partition .9.

Inside the absorber e, a sheet metal fairing or core 11. provides an annular space surrounded by the cylindrical partition s and in which a pipe coil '0, traversed by cooling water, extends beneath the trough t. The trough t is bordered by an annular weir t straddled by a wire gauze wick t over which weak liquor flows and is distributed over the pipe coil 11.

Evaporation takes place at the lower end of the evaporator f where the inert gas is delivered, precooled, by the pipe coil n, under the minimum partial pressure and therefore at the minimum temperature. Evaporation proceeds upwards under progressively increasing partial pressure, and therefore at progressively increasing temperatures, as the gas ascends in the evaporator. In ascending in theevaporator f the inert gas mixed with the refrigerant vapour progressively flows out through the holes q into the jacket :1 and thence directly to the absorber e. The dis-- tance between successive holes q increases from the lower to the upper end of the helical row, such that the inert gas mixture leaves the evaporator ata rate which causes the amount of refrigerant evaporated to be uniform as the partial pressure and temperature increase.

At the upper end of the row of holes q all or most ofthe inert gas has passed from the evapo-* rator i into the jacket p, and the evaporation proceeds by ebullition at the total pressure and therefore at the maximum temperature in the part of the evaporator 1 between the termination of the row of holes q and the lower trough 0. Here an excess of cold is produced at the maximum temperature and is utilised as hereinafter described.

Between the two troughs l and o in the evapo rator j, evaporation also proceeds at the total pressure and maximum temperature, and, as above described, is utilised to precool the weak liquor in the pipe coil m and the liquid refrigerant in the pipe coil ;i.

w are two pipe coils extending intercoiled with the inert gas pipe coil n downwards beneath the lower trough o in the evaporator "f. Fluid to be cooled, such as nitrogen in an oxygen plant, is passed in parallel downwards through the two pipe coils w, and thus becomes cooled by the refrigerant evaporating in the evaporator beneath the lower trough o. I

The total pressure in the evaporator ,f is kept low, for instancetwo atmospheres absolute, and in consequence the maximum temperature of evaporation of ammonia is below atmospheric temperature, namely for two atmospheres absolute, is -20 C. The fluid has, however, to be cooled from atmospheric temperature for instance +20 C. to for instance 19 C. before being cooled by the refrigerant evaporating at, a range of temperatures under the range of partial pressures reigning in the lower, gas traversed, portion of the evaporator. This first portion of the cooling is efiected by the excess of cold produced, as above described, at the maximum evaporation temperature under the totalpressure.

The evaporated refrigerant not removed by the inert gas which has escaped through the holes q, passes, together with any remaining inert gas, from the top of the evaporator j into the top of the absorber e by the pipe I interconnecting the absorber e and evaporator f. The resistance to flow in this pipe 1 causes a slight excess of pressure in the evaporator ,f promoting the leakage of inert gas through theholes q.

Any unevaporated liquid refrigerant drains from the bottom of the evaporator f by a pipe a into a jacket :11 surrounding the rich liquor pipe 9 Some of the refrigerant boils in this jacket 11 and by the bubbles of vapour so produced the remainder of the liquid refrigerant is raised up a pipe 2 into the bottom of the absorber e where it mixes with and is absorbed in the rich liquor.

x is a non-return valve in the pipe :2:.

The cooling of the rich liquor effected by the refrigerant in the jacket 3/, reduces the liability of the suction of the pump g causing evaporation from the rich liquor.

The inert gas does not serve to equalise the pressure thoughout the machine. The pressure in the boiler and condenser is greater than the pressure in the absorber and evaporator and the rich liquor is raised to the boiler pressure by the pump a. For instance with ammonia a boiler and condenser pressure of 9 atmospheres absolute is required to effect condensation with cooling water at 20 C.

The modified construction of diffusion refrigerating machine shown in Fig. 4 is intended to be used in cascade with the machine shown in Figs. 1 to 3, in order to extend the range of temperatures to a lower minimum temperature, for instance to -100 C. For this purpose, a refrigerant such as ethane and an absorption liquid such as butane, or toluol, or ethylene as the-refrigerant with dichlorethylene as the absorbent, which will not freeze at the minimum temperature are employed. Also, as usual in cascade refrigeration, evaporating liquid refrigerant from the higher temperature refrigerating machine, such as ammonia, is used to cool to the condensing temperature, which is below atmospheric temperature, the refrigerant, such as ethane in the lower temperature refrigerating machine, and also to cool the absorber.

The machine however can be used as an independent refrigerating machine with a refrigerant condensing at atmospheric temperature.

a is the boiler wherein liquor is heated'by steam generated in a chamber a by a gas burner b. c isthe rectifier. d is the condenser, cooled by ammonia evaporating in a pipe I.

The evaporator ,f is superposed on and is connected to the absorber e, by a tubular neck 2.

In this neck 2 the cold inert gas mixture descends from the evaporator fin contra-flow heatexchange with inert gas, freed from refrigerant ascending in pipes 3, from the absorber e to the evaporator ,f.

Liquid refrigerant passes by a pipe d to a cooling coil 7' in the evaporator j and thence by a pipe is with stop cock k to an annular trough at the top of the evaporator f.

The refrigerant descends over a weir o and wick 0 on to the pipe coils 7' and w, wherein respectively liquid refrigerant is precooled and extraneous fluid is cooled.

A cylindrical partition 4 closed'at the upper end extends upwards from the neck 2. This partition 4 is formed with a helical row of holes q, through which inert gas mixed with refrigerant vapour progressively passes out of the annular space wherein evaporation of the descending refrigerant takes place. This progressive escape of gas mixture is arranged to render substantially uniform the production of cold along the range of increasing partial pressures and temperatures in the evaporator, as already explained.

Below the holes q the refrigerant boils at the total pressure and the vapour enters the neck 2 through openings 5 in the partition 4.

The inert gas mixture passes to the bottom of the absorber e along the interior of a cylindrical partition 6 extending downwards from the neck 2.

Weak liquor is delivered into an annular trough t at the top of the annular space surrounding the cylindrical partition 6 in the absorber e. The weak liquor overflows a weir t straddled by a wick t which delivers the liquor on to a cooling pipe coil 12 traversed by a cooling liquid, such as liquid ammonia if a cascade machine, or, if not, by cooling water.

The liquor enriched by absorbing refrigerant from the gas mixture, passes by a pipe 9 to a pump g which forces it through the outer member h of a heat-exchanger coil to a pipe h which delivers it into the boiler a.

I claim:

1. In a diffusion refrigerating machine, a boiler, a refrigerant receiver connected to said boiler, an evaporator charged with inert gas and connected to said refrigerant receiver and having means providing progressive outlet of inert gas from adjacent one end of and along said evaporator, an absorber charged with inert gas and connected to said boiler, an inlet conduit interconnecting said absorber and said evaporator and providing circulation of said inert gas from said absorber to said end of said evaporator adjacent said progressive outlet means, and an outlet conduit interconnecting said progressive outlet means of said evaporator and said absorber and providing circulation of said inert gas from said evaporator to said absorber.

2. In a diffusion refrigerating machine, a boiler, a refrigerant receiver connected to said boiler, an evaporator charged with inert gas and connected to said refrigerant receiver and having means providing progressive outlet of inert gas from adjacent one end of and along said evaporator, an

absorber charged with inert gas and connected to said boiler, an inlet conduit interconnecting said absorber and said evaporator and providing circulation of said inert gas from said absorber to said end of said evaporator adjacent said progressive outlet means, an outlet conduit interconnecting said progressive outlet means of said evaporator and said absorber and providing circulation of said inert gas from said evaporator to said absorber, and a second outlet conduit interconnecting said evaporator beyond said progressive outlet means and said absorber.

3. In a diffusion refrigerating machine, a boiler, a refrigerant receiver connected to said boiler, an evaporator charged with inert gas and connected to said refrigerant receiver and having means providing progressive outletv of inert gas from adjacent one end of and along said evaporator, an absorber charged with inert gas and connected to said boiler, an inlet conduit interconnecting said absorber and said evaporator and providing circulation of said inert gas from said absorber to said end of said evaporator adjacent said progressive outlet means and extending in contraflow heat-exchange proximity with inert gas circulating in said evaporator, and an outlet conduit interconnecting said progressive outlet means of said evaporator and said absorber and providing circulation of said inert gas from said evaporator to said absorber.

4. In a diffusion refrigerating machine, a boiler, a refrigerant receiver connected to said boiler, an evaporator charged with inert gas and connected to said refrigerant receiver and having means providing progressive outlet of inert gas from adjacent one end of and along said evaporator, an absorber charged with inert gas and connected to said boiler, an inlet conduit interconnecting said absorber and said evaporator and providing circulation of said inert gas from said absorber to said end of said evaporator adjacent said progressive outlet means and extending in contra-flow heatexchange proximity with inert gas circulating in said evaporator, an outlet conduit interconnecting said progressive outlet means of said evaporator and said absorber and providing circula tion of said inert gas from said evaporator to said absorber, and a second outlet conduit interconnecting said evaporator beyond said progressive outlet means and said absorber.

5. In a diffusion refrigerating machine, a boiler, a-refrigerant receiver connected to said boiler, an evaporator charged with inert gas and having means providing progressive outlet of inert gas from adjacent one end of and along said evaporator, an absorber charged with inert gas and connected to said boiler, an inlet conduit inter' connecting said absorber and said evaporator and providing circulation of said inert gas from said absorber to said end of said evaporator adjacent said progressive outlet means, an outlet conduit interconnecting said progressive outlet means of said evaporator and said absorber and providing circulation of said inert gas from said evaporator to said absorber, a second outlet conduit interconnecting said evaporator beyond said progressive outlet means and said absorber, and an inlet conduit interconnecting said refrigerant receiver and said evaporator in heat-exchange proximity with refrigerant evaporating in said evaporator between said second outlet conduit and said progressive outlet means.

6. In a diffusion refrigerating machine, a boiler, a refrigerant receiver connected to said boiler, an evaporator charged with inert gas and having means providing progressive outlet of inert gas from adjacent one end of and along said evaporator, an absorber charged with inert gas and connected to said boiler, an inlet conduit interconnecting said absorber and said evaporator and 1 providing circulation of said inert gas from said absorber to said endof said evaporator adjacent said progressive outlet means and extending in contra-flow heat-exchange proximity with inert gas circulating in said evaporator, an outlet conduit interconnecting said progressive outlet means of said evaporator and said absorber and providing circulation of said inert gas from said evaporator to said absorber, a second outlet conduit interconnecting said evaporator beyond said progressive outlet means and saidabsorber, and an inlet conduit interconnecting said refrigerant receiver and said evaporator in heat-exchange proximity with refrigerant evaporating in said evaporator between said second outlet conduit and said progressive outlet means.

'1. In a diffusion refrigerating machine, a boiler, a refrigerant receiver connected to said boiler, an evaporator charged with inert gas and connected to said refrigerant receiver and having'a series of holes extending from adjacent one end of and along said evaporator, an absorber charged with inert gas and connected to said boiler, an inlet conduit interconnecting said absorber and said evaporator and providing circulation of said inert gas from said absorber to said end of said evaporator adjacent said series of holes, and an outlet conduit interconnecting said series of holes of said evaporator and said absorber and providing circulation of said inert gas from said evaporator to said absorber.

8. In a difiusion refrigerating machine, a boiler, a refrigerant receiver connected to said boiler, an evaporator charged with inert gas and connected to said refrigerant receiver and having a series of holes extending from adjacent one end of and along said evaporator, an absorber charged with inert gas and connected to said boiler, an inlet conduit interconnecting said absorber and said evaporator and providln'g-cir oulation of said inert gas from said absorber to said end of said evaporator adjacent said series of holes, an outlet conduit interconnecting said series of holes of said evaporator and said absorber and providing circulation of said inert gas from said evaporator to said absorber, and a second outlet conduit interconnecting said evaporator beyond said series of holes and said absorber.

9. In a diffusion refrigerating machine, a boiler, a refrigerant receiver connected to said boiler, an evaporator charged with inert gas and connected to said refrigerant receiver and having a series of holes extending from adjacent one end of and along said evaporator, an absorber charged with inert gas and connected to said boiler, an inlet conduit interconnecting said absorber and said evaporator and providing .circulation of said inert gas from said absorber to said end of said evaporator adjacent said series of holes and extending in contra-flow heat-exchange proximity with inert gas circulating in said evaporator, andan outlet conduit interconnecting said series of holes of said evaporator and said absorber and providing circulation of said inert gas from said evaporator to said absorber, and a second outlet conduit interconnecting said evaporator beyond said series of holes and said absorber.

10. In a diffusion refrigerating machine, a boiler, arefrigerant receiver'connected to said boiler, an evaporator charged with inert gas and connected to said refrigerant receiver and having a series of holes extending from adjacent one end of and along said evaporator, an absorber charged with inert gas and connected to said boiler, an inlet conduit interconnecting said ohsorberand said evaporator andproviding circulation of said inert gas from said absorber to boiler, an evaporator charged with inert gas and having a series of holes extending from adjacent one end of and along said evaporator, an absorber charged with inert gas and connected to said boiler, an inlet conduit interconnecting said absorber and said evaporator and providing circulation of said inert gas from said absorber to said end of said evaporator adjacent said series of holes, an outlet conduit interconnecting said series of holes of said evaporator and said absorber and providing circulation of said inert gas from said evaporator to said absorber, a second outlet conduit interconnecting said evaporator beyond said series of holes and said absorber, and an inlet conduit interconnecting said refrigerant receiver and said evaporator in heatexchange proximity with refrigerant evaporating in said evaporator between said second outlet conduit and said ser es of holes.

12. In a diffusion refrigerating machine, a

boiler, a refrigerant receiver connected to said boiler, an evaporator charged with inert gas and having a series of holes extending from adjacent one end of and along said evaporator, an absorber charged with inert gas and connected to said boiler, an inlet conduit interconnecting said absorber and said evaporator and providing circulation of said inert gas from said absorber to said end of said evaporator adjacent said series of holes and extending in contra-flow heatexchangeproximity with inert gas circulating in said evaporator, an outlet conduit interconnecting said series of holes of said evaporator and said absorber and providing circulation of said inert gas from said evaporator to said absorber,

a second outlet conduit interconnecting said evaporator beyond said series of holes and said absorber, and an inlet conduit interconnecting said refrigerant receiver and said evaporator in heat-exchange proximity with refrigerant evaporating in said evaporator between said second outlet conduit and said series of holes.

13. In a diffusion refrigerating machine, a;

' boiler, a refrigerant receiver connected to said boiler, an evaporator connected to said refrigerant receiver. an absorber connected to said evaporator, a pump, a conduit conducting liquor from said absorber to said pump, a conduit conducting liquor from said pump to said, boiler, a

conduit conducting liquor from said boiler to 75 said absorber, and a conduit in heat-exchange proximity with said conduit conducting said liquor to said pump and conducting to said absorber refrigerant drainingfrom said evaporator.

15. In an absorption refrigerating machine. a boiler, a refrigerant receiver connected to said boiler, an evaporator connected to said refrigerant receiver, an absorber connected to said evaporator, a pump, a conduit conducting liquor from said absorber to said pump, a conduit conducting liquor from said pump to said boiler, a conduit in heat-exchange proximity with refrigerant evaporating in said evaporator and conducting liquor from said boiler to said absorber, and a conduit in heat-exchange proximity with said conduit conducting said liquor to said pump and conducting to said absorber refrigerant draining from said evaporator.

16. A method of producing a range of temperatures in a diffusion refrigerating machine and uniformly cooling a fluid byand along said range of temperatures, consisting in evaporating refrigerant under increasing partial pressures of refrigerant in an inert gas, progressively decreasing the amount of said inertgas flowing past said refrigerant as said partial pressures increase,

' and passingsaid fluid in contra-flow heat-exchange proximity with said inert gas wherein said refrigerant is evaporating under said increasing partial pressures.

17. A method of producing a wide range of temperatures in a vdiflusion refrigerating machine \and limiting the production of cold at the higher-temperatures of said range of temperatures, consisting in precooling by heat-exchange with refrigerant evaporating in said machine inert gas and refrigerant liquid in said machine prior to admission of said inert gas to said refrigerant liquid, evaporating said refrigerant in said inert gas under partial pressures of refrigerant increasing approximately to the total pressure of said inert gas and refrigerant, and

progressively diverting said inert gas from said refrigerant as said partial pressures increase.

18. A method of producing a wide range of temperatures in a diffusion refrigerating machine and uniformly cooling a fluid by and along said range oftemperatures. consisting in precooling by heat-exchange with refrigerant evapcrating in said machine inert gas and refrigerant liquid in said machine prior to admission of said inert gas. to said refrigerant liquid, evaporating said refrigerant in said inert gas under partial pressures of refrigerant increasing approximately to the total pressure of said inert gas and refrigerant, progressively diverting said inert gas from said refrigerant as said partial pressures increase, and passing said fluid in contra-flow heatexchange proximity with said inert gas within said refrigerant is evaporating under said increasing partial pressures.

GUIDO MAIURI.