US1918820A - Method of and means for refrigeration - Google Patents

Description

July 18, 1933. w. s. NOLCKEN 0 METHOD OF AND MEANS FOR REFRIGERATION Filed July 13, 1951 s Sheets-Sheet 2 //V V N TOR wonrman seams: NOLCKFN,

3% E v Z Arr-onus" y 1933. w. G. NOLCKEN 1,918,820

METHOD OF AND MEANS FOR REFRIGERATION Filed July 13, 1931 3 Sheets-Sheet 3 L 7/ fix K A c M l I I l I I l I I I I I /NVE/V7'OR F/ G. 4-. WOLDEMAR GEORGE NOLCKEN,

2k 4 pal Patented July 18, 1933 UNITED STATES WOLDEMAR GEORGE NOLCKEN, OF LONDON, ENGLAND METHOD or AND iammsron. Bmmnnmrmn Application filed July 13, 1831, Serial No. 550,388, and in Great Britain July 28, 1980.

This invention relates to refrigerating apparatus of the ice box type.

In refrigerators of this type a sourw of extreme cold, such as solid CO commonly 5 known as dry ice, has been used and in order to prevent the too rapid dissipation of the refrigerant various means have been provided to control the evaporation. All such means function as insulators of low heat conductivity and they have been introduced between the refrigerant and the refrigerated commodity, as for examplethc ice blanket which surrounds and protects the subliming hydrated carbon dioxide ice in the product known under the trade mark Hydrice.

In all known arrangements of this kind, however, a certain amount of energy obtained from the solid refrigerant has been dissipated without any useful advantage being obtained therefrom since the heat flow takes place through a large temperature range without doing any work.

The object of the present invention is to provide an improved refrigerating apparatus of the ice box type in which this loss of energy is utilized so that more economic refrigeration is produced.

According to the present invention refrigerating apparatus of the absorption type 39 is operatively disposed between the solid refrigerant and the refrigerating chamber, the

energy necessary for driving the apparatus being that hitherto wasted in the manner described.

In carrying out the invention I may use the known refrigerating apparatus comprising a generator, condenser, absorber and evaporator. For the purpose of the present specification and claims thegenerator will be referred to as an evaporator since, as will be evident hereafter, the generator employed has the function solely of an evaporator.

In carrying out the invention the apparatus is rearranged in such a way that the two evaporating chambers are placed in the refrigerating chamber and the dry ice may be associated with the condenser in the same refrigerating chamber; or alternatively it may be disposed in a separate refrigeratin chamber. The latter course may beadopteg where it is desired to refrigerate to an ex- I tremely low temperature.

In carrying out the invention the heat flow in the apparatus is arranged in such a way that the absorber has the highest temperature, the condenser the lowest temperature, and the two evaporators have an intermediate temperature. This will be more fully Y explained hereafter.

It is customary to distinguish between absorption and adsorption, the former being essentially a process of dissolution, as for example ammonia in water, whilst the latter is a process of surface adsorption, as for example with silica gel or-charcoal in contact with vapours. In order to avoid confusion, both these processes will be referred to as absorption, it being underst0od that the general thermodynamic principles involved are alike in both cases.

Whereas in absorption machinery of the known type, the energy for producin refrigeration is derived from a source of eat, such as steam, electricity, gas or the like, in the apparatus according to the invention the energy for producing refrigeration is, as above set forth, derived from a source of intense cold, such as solid carbon dioxide for example.

Various ways of carrying out the present so invention are illustrated by way of example in the accompanying drawings, wherein i Fig. 1 is a diagrammatic representation of the heat flow in knownrefrigerating apparatus of the absorption type,

Fig. 2 is a diagram of the heat flow in apparatus according to the present invention,

Fig. 3 shows diagrammatically the application of the invention to an ammonia-water absorption plant of the openc'ycle type,

- Fig. 4 illustrates in diagrammatic form an intermittent ammonia-watermachine.

Fig. 5 is a. diagrammatic view of a modified form of apparatus using a, solid absorbent.

Referring first to Figs. 1 and2, Fig. 1 is a diagrammatic representation of a closed circuit absorption machine ofa well known type, and Fig. Qrepresents the same machine rearranged according to the invention. Alike reference letters in Figs. 1 and 2 denote alike arts. p The shaded portion LMNO represents a section through the heat insulating wall of a cold room or ice box. Parts of Figs. 1 and 2 which are inside the cold room are shown below the band LMNO and parts shown above the band are outside the cold room.

The working temperatures of the various parts of the two machines illustrated in Figs. 1 and 2 respectively, correspond to their respective levels in the diagram, warmer parts being shown above the colder ones, and with reference to the common temperature scale on the left side of the drawings.

- It will be understood that the range of possible working temperatures of the two machines is not limited to this scale.

Referring first to Fig. 1, G is the generator,

A the condenser, C is the evaporator and E the absorber. The refrigerant passes through the circuit in the order, generator to condenser, condenser to evaporator, evaporator to absorber, and absorber to generator, as shown by the plain lines and arrows. The generator is heated by steam, electricity, gas burner or the like, and the absorber and con denser are cooled by water or air.

In every absorption machine there are necessarily three working temperatures, T, T1 and T2, to be considered, and two working ressures. In Fig. 1 the generator G is at the igh temperature T of the source of heat and the working medium within it is at the high working pressure. The condenser A is at the intermediate temperature T1 of the cooling water or air, and at high pressure. From the condenser A the high pressure refrigerant flows into the evaporator (I through the expansion valve V, which lowers its pressure. The evaporator G contains low pressure refrigerant at the low temperature T2 of the cold room. In the absorber E, the refrigerant vapour from the evaporator C is absorbed at the low working pressure and intermediate temperature T1. The pump P compresses to the high workingpressure, and conveys to the generator G the absorption solution from E,

saturated with refrigerant. The return flow of the dilute solution from 'the generator to the absorber is omitted in the diagram. The high pressure side of the system is shown in double lines and the low pressure side in plain lines.

The direction of the heat flow through the machine is shown by'the dotted lines and arrows.

From the source of heat a quantity Q of heat at the high temperature T flows into the generator G and is rejectedto cooling water or air by the condenser A at the intermediate tem tity Q2 of heat to be absorbed by the evaporator C at the low temperature T2 of the cold room, and to be rejected to cooling water or perature T1. This causes a further quanair by the absorber E at the intermediate temperature T1.

The'ratio of heats for the ideal reversible process is expressed by the known equation Fig. 2 represents the absorption machine rearranged according to the invention. The absorber E is cooled by water or air and the condenser A by dry ice. The generator G and evaporator C absorb heat from the cold room? pansion valveV. The return flow of the weak'absorbent solution from the generator G to the absorber E through a pressure pump is omitted in the diagram Fig. 2.

The four organs of the machine are displaced with reference to the three working temperatures T, T1 and T2, and all temperatures are much lower than in Fig. 1. Accordingly the two working pressures are also lower.

Heat flows through the machine in the same direction as in Fig. 1 with reference to the organs of the plant, namely from the generator G to the condenser A and from the evaporator C to the absorber E as indicated by the dotted lines and arrows. With reference to the working temperatures, however, the direction of the heat-flow is reversed. Thus heat is taken in at the intermediate temperature T1 and rejected at the high and low temperatures T and T2 respectively.

A quantity Q2 of heat is rejected by the condenser A to the dry ice atthe temperature T2 and a quantity Q of heat is rejected by the absorber E to cooling water or air at the temperature T.- Both heats Q, and Q2 are absorbed in the cold room at the temperature T1 by the generator G and the evaporator C.

The heat equation for the ideal reversible absorption process may be transposed thus when it expresses the ratio of heats removed from the cold room to the heat rejected to the dry ice for any given range of workingtem ratures. As can beseen this ratio is at a 1 times greater than unity, that is to say, the quantity of heat withdrawn from the cold room is at all times greater than the quantity the balance being rejected to the cooling water or' air by the generator.

Stated briefly-in absorption machines, such as shown .for example in Fig. 1, a quantity Q2 of low temperature heat is absorbed in the cold room, 'umped up to a higher temperature level of cooling water or air to which it is rejected. The energy for the pumping of heat is supplied by the fall of the high temperature heat Q, from the generator tothelow temperature level of the condenser.

In the rearranged absorption machine (Fig. 2) this energy is supplied by the fall of low temperature heat from the generator to a still lower temperature level of the condenser.

In both machines, the part of the system comprising the generator and condenser acts in the .manner of a heat engine, and the part comprising the evaporator and absorber in the way of a heat pump, the latter being driven by the former. Whereas in the arrangement shown in Fig. 1 the heat engine works at a higher temperature level than the heat pump, in Fig. 2 the heat pump is at a higher temperature level than the heat engine. Accordingly, the working pressures within the two systems are also reversed. In Fig. 1 the heat engine works at high pressure and in Fig. 2 the pump. Such reversal of the working pressures is provided by interchanging the pump P and the valve V as in Figs. 1 and'2.

In order to drive an absorption machine by cold instead of by heat, means must be provided for the reversal of the working temperatures and pressures, that is to say the portion of the machine which acts as heat engine must work at lower temperatures and pressures than the portion which acts as heat pump.

In absorption machinery of the closed cycle type, wherein a pressure equalizing inert gas is used, this gas is in the circuit between the evaporator and absorber, that is to say the art which functions 'as heat. pump, is at a ower partial refrigerant vapour pressure than the part which works as heat engine, the total pressure throughout the system being the same.

The machine may be rearranged according to the invention by placing the pressure equalizing gas in circuit between the genera tor and condenser, that is in the region which acts as heat engine, and which must be at a lower partial pressure and temperature than the heat pump.. A machine rearranged in this manner is illustrated in Fig. 3.

In absorption machinery of the open cycle .or reversible type, the whole machine operates alternately as heat engine and as heat pump, both operations being carried out intermittently one after the other. During the ator. The gas space in the generator -generating 'period, when the machine acts as heat engine, the pressures and temperatures throughout the system are hi h and during the absorption period when eat is pumped from the evaporator to the generator-absorber, the working pressures and temperatures are low.

In accordance with the invention a reversible absorption machine may be arranged in such a way that the generating period takes place at a lower temperature and pressure than the absorption period. A machine rearranged in this manner is illustrated in Fig. 4. Fig. 5 illustrates a similar arrangement using a solid absorbent. v

Referring to Fig. 3 of the drawings, A is the ammonia condenser, which is kept at 109 degrees; with CO ice. The liquid ammonia flows by gravity through the outlet pipe B into the evaporator or boiler C, which refrigerates the insulated cold chamber LMNO (dotted line). The dry ammonia vapour formed in the boiler flows through the pipe D into the absorber E, where it is absorbed by water, kept at a constant temperature by cooling water or air. The warm strong liquor ammonia from the absorber flows through the pipe F into the generator G, and the cold weak liquor from the generator returns to the absorber through the pipe H. The enerator G is connected to the condenser by two pipes J and K wherein an inert gas circulates between the condenser and the em}:-

t e two pipes J and K and the gas space in the condenser A all contain the inert gas, which is prevented from escaping into the evaporating side of the system by the liquid seal in the pipe B. The ammonia is evaporated from the liquor in the generator at cold room temperature and low partial pressure into the inert gas. The gas saturated with ammonia rises in pipe J and the dry gas falls in pipe K. In the condenser A the ammonia gas mixture is cooled below the dew-point and the ammonia condensed. The pipes J and K are disposed as counterfiow heat interchangers. It will be observed that in general for every lb. of ammonia condensed in contact with the CO ice, another lb. is absorbed in the absorber and the heat of absorption rejected to the cooling water or air; whereas two lbs. are being evaporated inside the cold room, one in the generator G and the other in the evaporator C. It will also be observed that the chemical heat of combination of ammonia and water, which is exothermic, assists the process of refrigeration, whereas in the absorption plant proper it counteracts it.

Within the condenser A, the receptacle R, is disposed in a manner used for the construction of vacuum flasks. The container B may be charged with dry ice from without the cold chamber, and is protected by an extra heavily insulated lid. The condenser A is 7 a pipe D into the weak liquor pipe also heat insulated, on the outside, i. e. against the air in the cold room, internal bafiles are suitably disposed within the clearance space formed b the container R and the condenser A, wit a view to increasing the total internal surface of condensation, as well as to circulate the mixture of gases and vapours through long and tortuous channels. Suflicient clearance is provided for the formation of a coat of solid NH, on the outer surface of the container R. The lower portion of the condenser A forms a sump, wherein the liquid NH, collects.

From the bottom of the condenser A, the liquid NH, flows into the eva orator C, through the U-shaped pi B. ence in the hydrostatic evel of the liquid NH, in the two limbs of the U-shaped pipe B, provides the pressure head for the um ing of the liquor in the pipe H. Pref drab y the U-pipe B is heat-insulated against the cold room, in order to avoid or reduce to a minimum any possible heating of the highly subcooled NH, up to boiling point, and the resulting formation of gas bubbles in the U-pipe B.

From the evaporator C, the liquid NH, may be made to circulate in the known manner through the evaporator coil C,. In order to provide a separate temperature control, a magnetically operated stop valve W may be fitted, the said valve being connected to, and rated by, a thermostat located in the cold 0 amber. Alternatively, several temperatures may be provided in several cold chambers by connecting the container C to a plurality of evaporator coils. Each coil may be operated by a thermostatically controlled sto valve.

'l he dry and saturated NH, vapour, resulting from the eva ration of the liquid in the evaporator C col ects in the top part of'the container C, and flows through the S-shaped H. The pipe D is'in heat inter-change with the pipe F. The superheated ammonia vapour is dis charged into the rising limb of the U-pipe H, when it produces the pumping of the weak liquor from the generator to the higher level of the absorber E, in the known manner of gas lifts. In the absorber the solution is made to flow over pipes and baflles, wherein the cooling water is circulated. From the bottom of the absorber E, the warm rich solutionfiows by gravity through the U-pipe F into the generator G. The pipes F and H. are disposed in counterflow heat inter change. V

The de -aeration device S is of the known t pe and is fitted between the absorber E and e generator G, for the purpose of returning to the generator any non-absorbable gases which have escaped into the evaporator side of the system. Such escape of inert gases e differ-- from the condenser side of the system could for example take place when the plant is out of action for some time.

The generator G is provided onthe outside with fins and ribs or other suitable devices, for the purpose of increasing its heat conducting surface. Inside it the solution delivered by the mpipe F, flows over a plurality of internal ha es, which spread the solution out into thin sheets, exposing amaximum of liquid surface to the inert lgas, which enters by the pi e K and rises to t e top of the genera-- tor. n contact with the strong liquor the inert gas becomes saturated with NH, vapour and rises to the top of the generator G. The weakened solution collects at the bottom of the generator G and is returned to the ab sorber E through the pipe H.

The inert gas, saturated with ammonia,

rises in the 1pe J in consequence of its reduced spiac 0 weight and higher temperature. ydrogen, which is usual in absorption plants, is therefore not suitable as an m ert medium. Nitrogen may be emplo ed,'or any of the heavier inert gases). In t e condenser A the ammonia content of the gas in the ipe J is condensed and precipitated to the ttom of the vessel A, whence it flows into the pipe B. The cold inert gas from the condenser, having deposited its ammonia content, descends through the pipe K in consequence of itsincreased density and lower temperature, and is returned tohe generator G.

The pipes J and K are 'spos'ed in heat inter-change. This heat inter-change is not complete, and the resulting thermosyphonic circulation assists and accelerates the natural gravity circulation of the mixture of gases and vapours. I 7

As may be seen from Fig. 3 the pressure of tor C and the pipe D is slightly higher than thepressureintheinertgascycle. Thebalance is taken up by the column of liquid ammonia in pipe B, which provides the necessary'pressure for pumping the absorption solution in the gas 11ft in pipe H. .An increase in pres sure in C tends to accelerate the action of the gas lift and with it to speed up the circulation throughout the system. A fall in pressure in C tends to slow down the circulation. When the pressure in C is equal to or less than the pressure in the inert gas circuit, the gas lift stops and all circulation in the system ceases.

The pressure in C is the saturated vapour pressure of the boilingliquid refrigerant and is determined'by the temperature of the boiling liquid. The vpressure in the inert gas cycle is the combined partial pressures of the inert gas and therefrigerant vapour given ofi in the generator E. Whereas the vapour Emressure of the refrigerant varies within wide f 'ts with the temperature the inert gas the pure refrigerant vapour in the evaporathe warmer one.

, to the surrounding atmosphere.

. pressure varies but little. A rise in cold room temperature therefore tends to produce an excess pressure in C, causing the circulation to be accelerated and a fall in the cold sures are equal is the lowest temperature.

which can be reached in the cold room. The

.amount of inert gas initially charged into the machine determines this temperature, large quantities of gas producing high pressures and temperatures, and small quantities low pressures and temperatures.

In this way an automatic temperature'control is provided b the inert gas, which may be char ed into t e machine up to a predetermine pressure-corresponding to the lowest temperature limit in the cold room.

In Fig. 3, the condenser A, evaporator C and absorber E are all three in the 'same cold room. It will be understood that two cold rooms could be provided and kept at widely different temperatures, by placing the condenser A in the coldest room ahd C and E into The coldest room would be cooled by the direct action of the intensely cold dry ice contained in the receptacle R.

The absorber has been described as of the water-cooled type, but it will be understood that an air-cooled absorber may equally well be used, provision beiifg made for suitable baflles, fins or ribs on the outer surface of the absorber, to ensure efficient heat transmission Adequate air circulation over the heat transmitting surfaces should also be provided.

Refrigerating apparatus as described consists of a series of steel ipes and containers suitably disposed and ail welded together to form an hermetically closed system, provided where necessary with bafiles, fins and webs to produce surface efi'ects where required and the necessary heat interchanges as will be readily understood.

Referring now to Fig. 4, A is a condenserevaporator, which is provided With a compartment S, in which carbon dioxide ice may be placed. G is the generator and E the-absorber which may be air or water cooled. The dotted line LMNO represents a section through the cold-room or refrigerator.

At the beginning of the generating period, almost all the ammonia is dissolved in the strong warm aqua contained in the absorber.

condenser is lowered and condensation of the ammonia vapour takes nlace on the outer walls of the container S. The liquid condensatefalls to the bottom of the vessel A, where it accumulates. .The rapid fall of pressure throughout the system causes the strong liquor in the absorber E to be syphoned over 9 into the generator G through the pipe H.

Evaporation of the ammonia from the liquor in the generator and condensation in the condenser proceeds until the concentration pressure --temp3rature equilibrium corresponding to the low condenser temperature is reached. When all the carbon dioxide has evaporated, the process automatically reverses. The pressure throughout the I system rises, the weak liquor: is syphoned back into the absorber and absorption of the ammonia vapour evolved in the condenserevaporator Aby the liquor continues until the original pressure-temperature-concentration equilibrium is reached again, and the plant is ready for re-icing. The water vapour, which is entrained from the generator and conden s and gradually accumulates in the conden r-e'vaporator, may-be periodically,returned to the generator through. a bypass pipe.

During the generating period, the machine works at a lower temperature than during the adsorption period. This feature is useful in railway and motor van refrigeration, where intense initial refrigeration is required, in rder to ecool quickly a warm vehicle af r it has en iced up and before it starts on its journey.

The respectlve dlmensions of the container J 0 I S and the two commun'icat' vessels G and E are such that the combine total weight of ammonia and water in the system is equal to the weight of the dry ice in S, when completely filled. The pressures within the sys-' 106 tem are those of the saturated ammonia solution and depend on the temperature of the solution. As there is no sourceof heat the pressures are low and the machine may be. made of comparatively light material.

Instead of a water-ammonia system a solid adsorbent such as silica gel may beused with sulphur dioxide or any other suitable refrigerant.

The solid cannot conveniently be transferred into and out of the refrigerator as can the liquor; hence other methods must be used for the purpose of conveying heat from the refrigerator to the cold adsorbent during the icing period and for rejecting heat from the hot adsorbent to the cooling water or air durin the adsorption period.

Reference s now had to Fig. 5. A is the condenser and S the dry ice receptacle. The evaporator coil 0 is connected to the condenser as shown, and may be of any suitable shape or size. The'solid adsorbent is the heat insulated container E, which co unicates with the condenser A through the pine if;

D. LMNO' is a section' through the roof of the cold room- The twp pipes J and K each contain a volatile liquid and are hermetically sealed off, each formin a separate condenser-eva orator circuit. e evaporator coil of the pipe J and the condenser coil of the pipe K are both inside the container E and are shown alon ,side each other in Fig. in order to avoid o the generating period, the refrigerant condenses in contact with the dry ice, and the adsorbent gives off refrigerant and is thereby cooled. Heat flows through the pipe K from the cold room into the adsorber E. Durin the adsorption period the process is reverse The refrigerant evaporates in C and the vapour is adsorbed in E. The heat of adsor tion is rejected to the atmosphere through t e pigsJ.

is a stop valve in the vapour return line of the evaporator C; the valve W is operated b a thermostat located in the'cold room, for

t e purpose of providing a temperature control.

At the predetermined low cold room temperature at which the thermostat is set to opcrate, the valve W closes the return pipe of the evaporator G. Vapour builds up in the evaporator coil and the liquid refrigerant is driven back into the sump of the heat insulated condenser A. No more heat is withdrawn from the cold room by the evaporator C until the temperature rises again and the thermostat opens the valve W. When W is shut the temperature and pressure in A falls Fapidly and the evolution of vapour from the adsorbent increases. The pipe K contains a small quantity of an inert gas, together with the volatile liquid, which prevents the evaporator coil of K from falling below a predetermined temperature, corresponding to the pressure of the inert gas, as is well known. The valve W opens w enever the temperature rises. Such rise may be caused by exhaustion of the adsorbent or of the dry ice supply. In both cases refrigeration is taken over automatically b the evaporator C. I

. The application of the invention is not limited to solid carbon dioxide only, butmay be applied in every instance, where the difi'erence in temperature between the refrigerant and refrigerator is of sufiicient magnitude to warrant the interposition of a reversed ab sorption or adsorption plant, for the pur ose of increasing the quantity factor of the cat removed from the refrigerator by reducing the intensity factor of the heat drop. For example, liquid air and other cold liquefied gases would serve the same purpose as the CO but in practice the latter should be used on account of its relative cheapness.

What I claim and desire to secure by Letters Patent is t 1. In refrigeratin apparatus of the icebox t pe, the metho of producing an additiona refrigerating effect by interposing between the refri erant and the refrigerating chamber, a refrigerating apparatus working on the well known'absorption principle, 0 erated by the existing flow of heat from t e refrigerating chamber to ,the refrigerantsaid method consisting in condensing a"vapour in heat exchan e with the refrigerant, evaporating the con ensate at a higher pressure and temperature in heat exchange with the refrigerating chamber, absorbing thevapour in an absor tion medium at a still higher temperature in, eat excha e*with a cooling medium, and expelling the vapour from the absorbent at low pressure in heat exchange with the refrigerating chamber.

2. Refrigerating apparatus comprising a refrigerating chamber, an absorption machine consisting ofa condenser, absorber and two evaporators, connected in operative cycle, the elements being disposed within the refrigerating chamber with" the exception of the absorber, and a receptacle adapted to contain dry ice in heat exchange with said condenser.

3. Refrigerating apparatus comprising a refrigerating chamber, an absorption machine consisting of a condenser, absorber and two evaporators, connected in operative cy-v cle, including conduit means between the condenser and one evaporator for the circulation of an inert as therebetwec the elements being disposed within the efrigerating chamber with the exception of the absorber,

and a receptacle adapted to contain dry ice in gua heat exchange with said condenser.

4. Refrigerating apparatus comprising a refrigerating chamber, an absorption machine consisting of a condenser, absorber and two evaporators, connected in operative cycle, including conduit means between the absorber and one evaporator for the intermittent siphoning over of absorbent solution, the elements being disposed within the refrigerating chamber with the exceptionof the absorber, and a receptacle adapted to contain dry ice in heat exchange with said condenser. Y 1

5. Refrigeratingapparatus comprisinga" I refrigerating chamber, an absorption mber to the generator-absorber and from the generator-absorber to the cooling medium, and a receptacle adapted to receive dry ice in heat exchange with said condenser.

WOLDEMAR GEORGE NOLCKEN.

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