US2628478A - Method of and apparatus for refrigeration - Google Patents

Description

Feb. 17, 1953 E. w. ZEARFOSS, JR 2,628,478

METHOD OF AND APPARATUS FOR REFRIGERATION Filed Dec. 13, 1949 s Sheets-Sheet 1 PRfl/l/Rf [/61 per 1420M: wall) f e I g l twr/mur- (a. za ,0 a.)

mam: (441,, row/v: //vc/// E/Vr/MZPI- la. rm per /6.) INVENTOR.

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Feb. 17, 1953 E. w. ZEARFOSS, JR 2,623,478

METHOD OF AND APPARATUS FOR REFRIGERATION Filed Dec. 15, 1949 3 Sheets-Sheet :5

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Patented Feb. 17, 1953 UNITED METHOD OF AND APPARATUS FOR REFRIGERATION Elmer W. Zearfoss, In, Philadelphia, Pa., assignor to Philco Corporation, Philadelphia, Pa., a corporation of Pennsylvania Application December 13, 1949, Serial No. 132,766

14 Claims.

The present invention relates to refrigeration, the instant disclosure being a continuation-inpart of my copending application, Serial Number @9337, filed September 15, 1948, now abandoned. More particularly, the invention relates to a refrigeration method and system in which volatile refrigerant is evaporated and then condensed to obtain the desired refrigerating effect.

Refrigerating systems of the kind here contemplated are generally provided with an evaporator in which low pressure liquid refrigerant vaporizes and absorbs heat in the process; with a compressor in which low pressure vaporized and heat-laden refrigerant is compressed to increase its pressure to a value corresponding to a saturation temperature well above normal atmospheric temperature; with a condenser in which high pressure vaporized refrigerant rejects to the ambient medium and reverts to a liquid state; and with a pressure reducing device in which the high pressure liquid refrigerant is subjected to an expansion process effective to bring the refrigerant down to the low evaporating pressure and temperature.

In the expansion process, the pressure of the liquid is lowered and part of the liquid evaporates into gas, known as flash gas, the heat of vaporization required to produce this flash gas removing heat energy from the refrigerant and leaving the remaining liquid refrigerant in a condition in which it can absorb heat energy in the evaporator. The flash gas produced has no further value as refrigerant, since it has already ab-- sorbed its heat of vaporization, and it is advantageous that such flash gas be removed from the refrigeration system at the point of expansion and before it can enter the evaporator. It is thence returned to the compressor where it can be recombined with the remaining refrigerant in the refrigerating system.

For the simple refrigeration cycle outlined above, the work of compression, which is the only work input required, increases as the difference between the evaporation and condensation pressures of the refrigerant increases. This pressure 4 range is fixed, for the useful portion of the refrigerant, by the prevailing operating conditions, but I have discovered that a possibility of bettering the performance of the system lies in reducing the pressure range of that portion of the refrigerant which becomes flash gas during the expansion process. Formation of flash gas begins as soon as the expansion of the refrigerant starts. When the pressure has dropped a finite increment, a finite fraction of refrigerant has become saturated vapor and is therefore no longer capable of providing a refrigerating effect. If it were possible to extract this vapor and recompress it immediately, the required work of compression would be much less than is the case when the vapor is first expanded and lowered in temperature to the final evaporator pressure and temperature, and then is recompressed through the entire pressure range of the system. If the vapor formed after the first finite interval were extracted, then the remaining liquid could be further expanded and the resulting flash gas again removed, and this process, by adjusting the pressure range to be covered in each partial expansion, could be repeated as often as desired before reaching the final evaporator pressure.

As will be seen, from the foregoing discussion, the average pressure range over which the flash gas must be recompressed will be smaller, the greater the number of expansion increments, or stages; and, in the limiting case, said average pressure range will be smallest with an infinite number of stages, which corresponds to a continuous removal of flash gas. Such a continuous removal of flash gas would therefore require the least work of compression, thus yielding the most efficient operation of the refrigeration system.

It has been found impractical to increase the number of expansion increments, or stages, to more than two or three, due to the prohibitive increase in equipment necessitated by such an increase in the number of stages. The removal of flash gas, by an infinite number of discrete stages, as hereinbefore outlined, is, of course, impractical (see Pages 47 and 48, Refrigeration and Air Conditioning, B. F. Haber and F. W. Hutchinson, Wiley, 1945) It is a feature of the present invention that there is effected continuous removal of saturated vapor flash gas formed in the transition from high pressure to low pressure refrigerant.

It is a primary object of the present invention to provide a method and apparatus for removing, in the most efficient manner possible, flash gas formed during a refrigeration cycle.

It is a further object of the present invention to increase the coeflicient of performance of a refrigeration system to a value considered impossible of attainment heretofore.

It is still another object to increase the coefficient of performance of a refrigeration system, While, simultaneously, reducing the volumetric capacity of the compressor required to give a predetermined amount of refrigeration.

These and other objects of the invention, and

the manner in which they are attained, will be more fully understood from the following description and with reference to the accompanying drawings in which:

Figure 1 shows a conventional pressureenthalpy diagram, well known in thermodynamics and illustrating the thermodynamic performance of an ordinary, simple refrigeration system;

Figure 2 shows a conventional pressureenthalpy diagram, illustrating the thermodynamic performance of an ordinary, multi-stage refrigeration system;

Figure 3 shows a conventional pressureenthalpy diagram, illustrating thevv thermodynamic performance achieved by the apparatus of the present invention;

Figure 4 represents, somewhat diagrammatically, a refrigeration system embodying the present invention;

Figure 5 illustrates, on an enlarged scale, a portion of a. control mechanism used in the system shown in Figure 4; and

Figure 6 is a further, somewhat diagrammatic representation illustrative of a refrigeration system comprising an alternative embodiment of the present invention.

Now making more detailed reference to Figure 1, lines aa and bb, respectively, represent the saturated liquid and saturated vapor lines of a volatile refrigerant such as dichlorodifluoromethane (Freon 12). Point 0 indicates the state of a pound of the refrigerant upon issuance from the condenser of a simple refrigeration system of the type previously described, and point 6 represents the state of said refrigerant after constant enthalpy expansion along line ce, as is usual. In the course of this expansion, the formation of flash gas causes a reduction of the available heat capacity per pound (represented graphically by line f-s) of the refrigerant, by the amount represented graphically by the line fc. This is not due only to the formation of the volume of flash gas which is unavoidably associated with an expansion such as the above, but also due to the fact, that since no flash gas is removed until the completion of the expansion, those portions of the flash gas which are formed in the early part of the expansion must further be cooled during subsequent expansion, and thus cause a still further reduction in the heat capacity originally available per pound of refrigerant. The liquid refrigerant, which is sometimes separated from the flash gas, is passed through the evaporator, changing its condition along line (5-8. Both flash gas and refrigerant are then recompressed along line s-d, necessitating an expenditure of work per pound which, in terms of heat units, is equal to the projection s-d of s-d on the enthalpy axis. The compressed refrigerant and flash gas are then returned through the condenser to state 0 and the cycle is ready to start again.

With reference to Figure 2, it will now be seen that if the flash gas formed during that portion of expansion ce denoted by segment 0-1, is removed in the state described by point I, this flash gas can be recompressed to the initial pressure condition along line s1dl, which corresponds to a smaller expenditure of compressor work per pound of flash gas than would have been required had this aforementioned portion of flash gas'been permitted to expand to the flnal evaporator pressure represented by point e. The refrigerant remaining, after removal of the flash gas at point iii Z, is now again a saturated liquid in a state described by point i and can now proceed to expand again at constant enthalpy, which will bring it, this time, to the state described by point m. Then, only the flash gas formed during expansion i-m need be removed at this time and recompressed over the total. pressure range along line s-d, together with the evaporated refrigerant which provides the useful refrigeration.

Having shown that the work per pound needed to recompress flash ga along line sl-di (represented by the projection Si'-dl' of Si-di on the enthalpy axis) is smaller than the work per pound needed to recompress flash gas along line s--d. (represented by the projection sd of sd on. the enthalpy axis), it now follows that the average work per pound required to recompress all the flash gas formed during the cycle of Figure 2 will be less than that required to recompress all the flash gas formed during the cycle of Figure 1. An, additional saving in the cycle of Figure 2 will resultv from. the fact that no flash gas need be formed, during expansion z'm, to effect further cooling of flash gas previously formed during, expansion cl. Thus there exists a greater heat capacity available per pound of refrigerant at. the final pressure, the increase being represented by segment e.--m of Figure 2, and which increase raises the. heat capacity available from an amount represented by 5-6, to an amount denotedby the. lines-m.

Figure 3 illustrates what occurs, in this thermodynamic refrigeration cycle, when the number: of stages of expansion and flash gas removal is actually, or effectively, increased to infinity. As shown in Figure 3, the expansion line cthen follows an isentropic, or reversible adiabatic. This can be explained as follows: It is physically impossible. to increase the number of discrete expansion stages to infinity, therefore alternative means, hereinafter described, are used to accomplish the equivalent effect, namely the continuous removal of flash gas immedaitely upon its formation and at the pressure at which it is formed. If, then, each infinitesimal amount of flash is removed as soon as it is formed, cooling thereof will not be required, as would have been the case had it been permitted to remain in the system duringv subsequent expansion, and the expansion becomes a reversible adiabatic process as herein before stated.

Comparative consideration of Figures 2 and 3 might, at first sight, lead to the erroneous conclusion that, if the expansion of Figure 3 is the same as. the expansion of Figure 2with the number of stages carried to infinity as a limit and, conversely, the size of each stage reduced to an infinitesimal decrementthen the line in Figure 3, showing that expansion, should coincide with the saturated liquid line ca. The error of this conclusion can readily be seen if it is recalled that it is the, practice in thermodynamics to draw diagrams, such as Figure 2, using the, rcfrigerant in the initial saturated liquid state as base of reference. This means that at point z of Figure 2, a new reference has been introduce-ii, amely the quantity of liquid refrigerant remain g in the system at that pressure and after having subtracted the flash gas previously form cl. This remaining liquid will form more flash during expansion i-m, losing a portion of its available heat capacity in the process. Thus, in Figure 2, the proportion of liquid and flash gas denoted by point m refers to the original quantity of refrigerant present at point while the proportion denoted by point I refers to the larger original quantity of refrigerant denoted by point c. This same reasoning must be applied to Figure 3, Where each proportion indicated by any point on line c-e, must be referred to the original total quantity of refrigerant. In short, it must be borne in mind that Figures 2 and 3 are conventional graphical representations of the thermodynamic changes in the respective processes, and the showings of said figures are quite independent of any physical apparatus employed to eflect these changes.

The average pressure range, shown by line Say-dav of Figure 3, over which such continuously removed flash gas must be recompressed, will now be smaller than that which could be obtained with any finite number of stages and, in addition, the heat capacity of the low pressure liquid refrigerant will be highest, since no cooling of flash gas takes place.

The former of these two effects, namely the decrease in average pressure range, makes possible the decrease in compression Work, and the latter, namely the increase in heat capacity availability, makes possible the reduction in vol: ume of refrigerant needed to produce a certain amount of refrigeration and, thereby, reduces the volumetric capacity and cost of the whole system.

The advantages of a method of removing flash gas continuously and as soon as it is formed are hence twofold. First, only as much flash gas is formed as is necessary to lower the refrigerant pressure and temperature to the values required by operating conditions and, secondly, that flash gas is removed in the manner requiring the least possible work, namely at the pressure at which it is formed.

The terms used in the foregoing analysis are well-known in the field of thermodynamics and accordingly, no further explanation is deemed necessary here. If a further clarification is desired, reference may be had to Refrigeration and Air Conditioning Engineering, B. F. Rabor and F. W. Hutchinson, Wiley, 1945.

Referring now to Figure 4, there is diagrammatically illustrated a refrigeration system which comprises a preferred embodiment of the present invention.

The system includes a conventional compressor iii, a conventional condenser H, and a receiving tank I2, containing a horizontally hinged mercury pool switch i3. The compression side of compressor iii, the condenser H and the receiving tank i2 are connected by refrigerant flow conduits. The system further comprises refrigerant flow conduits of substantially non-restrictive dimensions connecting receiving tank I2 to an insulated expansion tank or chamber 14 through a valve I5, and refrigerant flow conduits leading from insulated expansion tank M to the top header of evaporator 16 through a valve H. The tank M is preferably of such a nature that it is of low thermal mass, in order that the heat loss therein will be negligible.

Mercury switch 43 is connected to control means such as a solenoid (not shown) designed to operate valve IS in a manner described below. Further means are provided, such as temperature sensitive bulbs l8 and I9, for detecting differences in refrigerant temperature between the input of evaporator I6 and the output of expansion tank It, said means being connected to a control 28 arranged to actuate valve H in the manner described in detail below.

The suction port of compressor I0 is connected to an opening near the top of expansion chamber M. This compressor connection is effected by Way of a refrigerant conduit 22 of substantially non-restrictive dimensions. The reason for this arrangement will become apparent from the detailed description of its operation.

A temperature sensitive cycle switch control bulb 23 is (placed at the output of evaporator IE, to initiate and control the operation of compressor In in response to the temperature of the evaporator. This latter cycling control is conventional and, for the purpose of the present invention, no further description or illustration is necessary.

To obtain an understanding of the operation of the system, let it first be assumed that the system is at rest, the compressor, and other components not having recently been in operation. The ambient temperature and the temperature of the system itself are, of course, considerably in excess of the temperature necessary to cause control bulb 23 to startthe compressor l0 through conventional relays (not shown). When the compressor begins operation, valves and I! are both closed, as will become evident from the subsequent discussion.

.At this time the refrigerant is dissolved in the compressor oil, except for such refrigerant as still exists in the gaseous state throughout the remainder of the system, the pressure of the dissolved refrigerant being equal to the pressure of the gaseous refrigerant.

In operation, the compressor distillsrefrigerant from the oil in which it is dissolved and forces it into condenser H, where it is condensed into liquid refrigerant at a high pressure and temperature as represented thermodynamically by that portion of the process shown graphically by line 03-0 of Figure 3. This distillation reduces the pressure of that portion of the refrigerant remaining dissolved in the oil, and operation of the compressor simultaneously reduces the :pressure of such a small quantity of refrigerant as exists as vapor in tank M.

The liquid thus formed begins to fill receiving tank 12. The horizontally pivoted mercury switch l3, located inside this tank, is so connected that rising of the liquid above a certain level causes an electrical contact to be made which in turn causes actuation of solenoid operated valve I5.

Since substantially no liquid refrigerant exists in the system, until this initial filling of tank i2, switch l3 will evidently have heretofore maintained valve I5 closed, .as hereinbefore stated. The switch is so arranged that itwill'permit outflow of refrigerant through valve i 5 until a level is reached in tank It which is very much lower than that at which the switch makes contact.

Switch I3 then breaks contact and solenoid operated valve l5 closes, permitting renewed filling of receiving tank [2. The delayed opening of mercury switch 3 may be accomplished in any desired manner. For example, switch. l3 ma be constructed as shown in Figure 5, and comprise a horizontally .pivo ted float; M with a ridge '25 separating the high-buoyancy section P26 from the contact section v2'! and containing mercury pool 28 and normally open contacts 29 connected by leads to an external source (not shown) of electric pctentiai. When the liquid level denoted by reference numeral 36 rises to a predetermined height, section 26 also rises about pivot Stand some mercury spills over ridge 25 into contact 7 section 21. Since the cohesion of mercury. is greater than its adhesion, substantially all the mercury is drawn into contact section 27 and an electrical path is established between contacts 29, with the results hereinb efore described. When the liquid level 38 falls, on the other hand, the ridge 25 prevents the mercury from returning to section 25, and thereby openin contacts 29, until the liquid level has fallen to a predetermined low level, thus permitting valve I to remain open until tank I2 has been substantially emptied as hereinbefore described.

Receiving tank I2 will, in most commercially practicable systems, be located in a surrounding medium which is at the same ambient temper-- ature as the medium surrounding condenser II. Since the refrigerant temperature drop due to heat exchangethrough the conduits connecting condenser II and tank I2 will, in most cases, be

practically negligible, for the foregoing implies that the temperature of the refrigerant in tank I2 will, ordinarily, be higher than that of the surrounding medium. In that case, receiving tank I2 should be uninsulated, as shown in Figure 4, in order'to take advantage of the favorable heat exchange between the refrigerant in tank I2 and the lower temperature surrounding medium, and thus obtain further partial cooling of the hot refrigerant. If receiving tank I2 should belocated in a surrounding medium which is at a higher temperature than the temperature of the refrigerant as it arrives in the tank, then it would, of course, be advantageous to insulate tank I2, to prevent the refrigerant from being unnecessarily heated by the surrounding medium.

The opening of valve I5 permits the high pressure refrigerant to flow out of receiving tank I2 and into expansion chamber I l, still at substantially the same high pressure and temperature, but the refrigerant is prevented from reaching evaporator It by closed valve IT. The operation of valve I! is controlled bytemperature sensitive bulbs I8 and I9 which are connected to opposed bellows which, in turn, actuate a conventional system of levers generally designated by reference numeral and arranged to open and close valve IT, as follows. Bulb I8 is gas charged at 20 F. and bulb I9 is gas charged at 55 F., and the bellows and mechanical linkages 2d are so arranged that valve I I is closed when the temperature at bulb I9 exceeds the temperature at bulb I8 by F., or more, and open when the temperature at bulb I9 exceeds that at bulb I8 by 5 F. or less. Such arrangements are well-known'in the art and require no further discussion here. The temperature differentials listed above are not critical, but merely indicative of a preferred set of conditions. Since the normal room temperature is assumed to be higher than 55 F., the effective temperature differential between bulbs I 8 and I9created by gasv charging thereofis sufficient to keep valve I! initially closed, as here inbefore stated. The high-pressure liquid in tank I4 is now confined by closed valves I5 and I1, its only remaining communication with the other elements of the system being by Way of conduit 22, which leads directly to the suction port of compressor III. Each successive suction stroke of compressor II] will then result in the creation of a pressure differential between tank I l and the compressor cylinder. This, in turn, will cause the formation and removal at the pressure of formation, of a given incremental volume of gaseous refrigerant, or flash gas, from tank I4. Formation of each such volume of flash gas results incoolingof the remaining portion of liquid re.- frigerant in tank I 4. V

This process of decreasing the pressure of the refrigerant, forming flash gas and thereby cooling the liquid refrigerant, but (and importantly) removing each increment of flash gas to the compressor as soon as such flash gas is formed, constitutes the fundamental process of the present invention.

From the foregoing, it is clear that evacuation of gaseous refrigerant from tank It will proceed at a rate determined solely by the gradual reduction of pressure in tank I4 due to the operation of the compressor I9 and entirely independently of the pressure conditions anywhere else in the system.

When the refrigerant in tank I4 has been cooled to within 5 F. of the temperature at which bulb I8 is gas charged, this difference in temperature between bulbs I8 and I9 will be sensed and control 20 will operate to open valve I'I. Since the refrigerant in tank It is now still at a higher pressure than any refrigerant in evaporator I6-by virtue of the aforesaid 5 temperature diiferentialthe refrigerant will flow into evap orator I6.

By the simple expedient of introducing this refrigerant into the top header of the evaporator, as hereinbefore briefly stated, any back-flow of liquid refrigerant into the expansion tank is prevented, =even though the evaporator may be located above the expansion tank.

With the passage of the liquid reference from tank I4 into evaporator I6, unrestricted communication between the top header of this evaporator and the suction port of compressor III is established. This communication is by way of valve I? (which remains open for the time being, since there exists, as yet, no temperature diiferential sensible to feeler bulbs I8 and I9 which could cause this valve to close), through tank I4, which is now devoid of liquid refrigerant, and through conduit 22.

The liquid refrigerant in the evaporator, now absorbs heat from the medium to be refrigerated, in the usual manner, becoming vaporized in the process. Continued operation of compressor It will then result in the withdrawal of this vaporized refrigerant from the evaporator and in delivery thereof to the compressor where it is recompressed for renewed delivery to the condenser and recirculation through the system.

To preclude the possibility of delivery of a new load of hot high pressure refrigerant to expansion tank I4, which would cause valve I! to close prematurely, thereby preventing successful evacuation of the vaporized refrigerant from evaporator I6, the system is so designed that, for a given volumetric capacity of the physical components, there is not enough refrigerant available to enable tank I2 tofill up to its relief level before substantial evacuation of evaporator It has taken place. While many arrangements may be employed which fulfill the preceding requirement, for the sake of simplicity it may be assumed that the components are so proportioned that substantially all the refrigerant in the system is needed to fill tank I2 to a level high enough to cause valve I5 to open (as hereinbefore described). This arrangement, as hereinbefore pointed out, prevents the premature admission of hot refrigerant to tank I 4, thereby preventing the premature closure of valve H. In addition, there is, thus, evidently no possibility of tank I2 filling to a level which would cause valve I5 to open bellman; a,

fore expansion tank M has emptied into evaporator l6, thereby precluding any possibility of hot refrigerant contacting, or mixing with cold refrigerant.

When in steady state operation the closing of valve I! is effected by the first sensing by bulb 59, of the arrival of hot refrigerant from tank 12, which bulb then acts to cut tank It off from evaporator 45 until said refrigerant is suffi-ciently cooled.

Figure 6 represents an alternative embodiment of the refrigeration system of the present invention. This system is differentiated from the one shown in Figure 4 in that it has a compressor 32 which can, by means of conventional solenoidcontrolled reversing valves, 33, 34, 35, and 36, acting upon conduits 33a, 34a, 35a and 33a, respectively associated therewith, be made to interchange its suction and its compression sides with respect to an externally connected system. It further has two condensers 31 and 38. It has two insulated tanks 39 and 40, which are used alternately as receiving and expansion tanks. it further comprises valves 4! and 42, acting upon conduits 41a and 42a, respectively, which connect a single evaporator 43 to tank 39 and tank 49. Evaporator 43 is located below tanks 39 and 49, in order to enable refrigerant to flow from these tanks to evaporator 43 under the influence of the force of gravity. One pair of temperature sensitive feeler bulbs 44 and 45, similar to bulbs l3 and I9 of Figure 4, are arranged to sense the temperature at the output of tank 39 and in the evaporator 43, respectively, while another pair of feeler bulbs 46 and 41, also similar to bulbs l8 and [9 of Figure 4, are placed to sense the temperature at the output of tank 49 and in the evaporator 43, respectively. Bulbs 44 and 45 and bulbs 45 and 4'! are each connected to a pair of opposing bellows and linkages respectively designated by reference numerals 48 and 49 and similar to control 29 of Figure 4. Control 43 is arranged to control the opening and closing of valve 4! while control 49 controls the operation of valve 42. Bulbs 44 and 46 are gas charged at 55 and bulbs 45 and 41 are gas charged at 20 F. Controls 48 and 49 are so arranged as to close valves 41 and 42, respectively, when the temperature at the output of each respective tank exceeds the temperature in the evaporator by 30 F., or more, and to open valves 4! and s2, respectively, when the temperature at the output of each respective tank exceeds the temperature in the evaporator by F. or less. Thus each pair of temperature sensitive feeler bulbs (such as bulbs 44 and 45) cooperates with the control connected thereto (such as control 43) to operate the valve associated with the control (such as valve 41) in response to the difference in temperature existing between the respective tank and evaporator 43. I

A cycling bulb 50, similar to bulb 23 of Fi ure 4, is arranged to'sense the temperature of evaporator 43 and to control the operation of compressor 32 by means of conventional relays (not shown).

Tanks 39 and 49 are each equipped with horizontally pivoted mercury pool switches respectively numbered 5| and 52 and similar in construction to the switch illustrated in Figure 5. The set of contacts in each switch is connected to a sourceof electric potential (not shown) and each set of contactsis further connected to a conventional double-throw locking relayrepresented schematically by box 53--in such a mannor that closing of one switch throws therelay in one direction and looks it there, until closing of the other switch releases the relay from that position and throwsit in the opposite direction. Operation of the relay 53, due to the action of switch 5i, makes suitable electrical contacts (not shown), thus energizing the solenoids associated with valves 33 to 39, opening valves and 36 and closing valves 33 and 34, while operation of switch 52 causes relay 53 to reverse, making suitable electrical connections to energize solenoids to close valves 35 and 35 and open valves 33 and Thus, effectively, closing switch 5| connects tank 39 to the suction side of compressor 32 while closing switch 52 connects tank to the suction side of compressor 32. Since relay 53 is of the locking type, in each position, the first mercury switch to operate the relay loses control of relay 53 once it has caused it to operate, and only the other switch is capable'of reversing the relay position.

To assist full comprehension of the operation of this system, the following detailed description is presented. The system is assumed to be rest-the compressor 32 and the other components of the system not having been recently operatedand valves 33 and 34 having remained open from the time when the system had last been operated. The ambient temperature and the temperature of the system itself, are, of course, considerably in excess of the temperature necessary to cause cycling bulb 59 to initiate operation of the compressor, with the result that the comprcssor commences operation and the refrigerant in the compressor is forced into condenser 37 where it is condensed into hot liquid. This hot liquid refrigerant being at least at the ambient temperature and therefore at a higher temperature than is required to close valve 4|, this valve will close and the hot liquid refrigerant will accumulate in tank 39. .When it has reached a level sufiiciently high to tip and close switch 5 lthereby reversing relay 53 and connecting tank 39 to the suction side of compressor 32 as hereinbefore described-flash gas will start to form in tank 33 and will be removed by compressor 32, in a manner similar to the formation and removal of flash gas from tank 14 of the embodiment shown in Figure 4.

Again, removal of flash gas immediately upon, and at the pressure of formation, constitutesthe basic characteristic of this embodiment of the present invention.

The flash gas removed from tank 39 is compressed in compressor 32, condensed in condenser 38 and, having closed valve 42 bythe effect of its high temperature on bulb 43, begins to accumulate in tank 49. When the liquid refrigerant in tank 39 has, for example, been cooled to 25 F., valve 4i opens, as hereinbefore described and the cold refrigerant is gravity-fed into evaporator 43, where it absorbs heat from the surrounding medium, vaporizes and is exhausted by the suction of compressor 32, to which evaporator 43 is now connected. The gaseous refrigerant thus removed will be compressed in compressor 32, condensed in condenser 38 and also stored in tank 49. When sufiicient refrigerant has accumulated in tank 40 to tip and close mercury switch 52, the valves associated with compressor 32 reverse, as hereinbefore described, and tank 40 is now connectedtothe suction side of compressor 32, with the result that flash gas is now removed from tank 40 with the attendant cooling of theliquidrefrigerant remaining in tanli; 5.9. This flash gas is again compressed in compressor 32, condensed in condenser 3] and delivered to tank 39 where it closes valve 4i immediately upon arrival, thus permitting accumulation of hot liquid refrigerant in tank 39. When the temperature of the refrigerant in tank 40 has been lowered to 25 F., valve 42 opens as hereinbefore described and the refrigerant from tank 48 is gravity-fed into evaporator 43. The vapor formed in evaporator 43 isv again exhausted and compressed by compressor 32, condensed in condenser 3'! and stored in tank 39, the mercury switch 5! in the latter again reversing the compressor connections when the proper liquid level is reached, thus initiating anew'cycle. Here again, the temperature differentials referred to are not critical but are intended only to be indicative of a preferred set of conditions. Furthermore, it will be understood that mercury switches :H and 52 are so adjusted in tanks 39 and :33 as to permit maximum utilization of each tank and are, in addition, so located that each will tilt and make contact when substantially the same quantity of liquid refrigerant has accumulated in one tank as would be required to make the switch tilt in h o her. tank It is clear that the means for controlling valve I? of'figure i and valves 4 and 42 of Figure 6 are not, per se, an essential feature of the invention, and, that any conventional means suitable for accomplishing the desired results outlined; above, may be employed. A practical systemjwhich is suitable for this purpose, as indicated above, consists of two opposedbellows, each n of which is subjected, to the pressure existing in one of the pairv of temperature sensitive bulbs associated with each of the above valves, together with a system of linkages so arranged as to be responsive to the difference between i.'

the movements of the bellows. A suitable system, of bellows and linkages. such as outlined above is disclosed in Bauman. United States Patent No. 2,440,628, issued April 2'7, 1948, and assigned to the assignee of the present invention. The linkages may operate; the valves directly, as shown by the broken line connecting each valve to its respective control, or,.if desired, may serveto actuate, an, electrical system (notshown) used to; open and close the respective valves,

As will be evident from the foregoing description, both of the described embodiments accomplish and. bring out the'principle of the present invention, namely the substantially continuous removal of hash gas from the expanding refrigerant as soon; as such flash gas is formed, and at the pressure and temperature at which itis formed. 'As shown in the preceding discussion this results in the lowest possible requirement of work input into'the system, fora given amount of refrigeration, and therefore in the highestpossible coeincient of performance.

While two embodiments ofthe invention have been described with particularity, it will be understood that; the invention is susceptible of changes and; modifications, without departing from the essential spirit thereof; For example a si th r th n he. co p essor arran ements shown, might beempl'oyed to, effect thetransition. ofj the refrigerant from the gaseous tot'he liquid state, Similarly, as set, forth above, control of the flow. of. the refrigeranttoward thev evaporator maybe, accomplished in avariety of ways.- How-- ever, it will be evident that such changes and 12v modifications are contemplated, as may come within the scope of the appended claims.

I claim:

1. In a refrigeration system including a condenser and an evaporator. connected in circuit, and an expansion chamber disposed in the circuit intermediate said condenser and evaporator, the method of operation which includes the following steps: delivering to said chamber liquid refrigerant derived from said condenser; isolating the refrigerant in said chamber from said evaporator; gradually decreasing the pressure of the liquid refrigerant in said chamber to provide for the incremental formation of flash gas and consequent gradual cooling of the liquid refrigerant; effecting separation of increments of flash gas upon formation thereof and under substantially the temperature and pressure conditions at which said increments are formed; and delivering to said evaporator the resultant cool, low-pressure liquid refrigerant in said chamber.

2. In a refrigeration system including a compressor, a condenser and an evaporator connected in circuit, and an expansion chamber disposed in the, circuit intermediate. said condenser and evaporator, the method of operation which includes the following steps: compressing volatile refrigerant. fluid in the. gaseous state; condensing said delivering to. said chamber a predetermined quantity of liquid refrigerant derived from said condenser; isolating the refrigerant in said chamber from said evaporator; gradually decreasing the pressure. of the. liquid refrigerant in said chamber to provide for the incremental formation, of flash gas and consequent. cooling of the liquid refrigerant; effecting separation of increments of. flash gas immediately upon formation and under substantially the temperature and pressure. conditions atwhich said increments are formed, returning separated flash gas to the compressor under the influence of the suction of the compressor and recompressing said flash gas for subsequent re-use in. the. system; and delivering to said evaporator the cool, low-pressure liquid remaining in said chamber.

3.. In 'a refrigeration system including. a com.- pressor, a condenser and. an. evaporator con.- nected in circuit, and an expansion, chamber. dis. posed in the, circuit intermediate said condenser and evaporator, the method of operation which includes the following, steps: compressing volatile refrigerant fluid in the gaseous state; con.- densing the. compressed fluid; delivering a predetermined quantity of said condensed fluid. to

said expansion chamber; isolating the refrigerant in said chamber from said evaporator, grad,- ually reducing the pressure in said. expansion chamber under the influence of the suction of said compressor to provide: for the incremental formation of flash gas in saidv chamber and consequent cooling of the liquid refrigerant; effecting separation of each increment of flash, gas.

upon formation thereof and under" substantially the temperature and pressure conditions atwhich each increment is formed; recompressing the said separated flash gas for subsequent. re-use in the system and vaporizing; the remaining cool. low-pressure liquid in heat exchange relation with the evaporator.

4; In a refrigeration system including a condenser and an evaporator connected in circuit,

means for delivering liquid refrigerant from saidv condenser to said evaporator at, predetermined conditionsv of pressure and temperature,- said means comprising: apparatus for gradually deaeaaavs creasing the pressure of the liquid refrigerant prior to its delivery to said evaporator to provide for incremental formation of flash gas and consequent cooling of the liquid refrigerant; means for effecting separation of increments of flash gas immediately upon formation and under substantially the temperature and pressure conditions at which said gas is formed; and valve means effective to close off said chamber from said evaporator during cooling of the liquid refrigerant and to initiate substantially unrestricted delivery of the resultant cool, low-pressure liquid to said evaporator.

5. In a refrigeration system including a compressor, a condenser and an evaporator connected in circuit, means for delivering liquid refrigerant from said condenser to said evaporator at predetermined conditions of pressure and temperature, said means comprising: apparatus for gradually decreasing the pressure of the liquid refrigerant under the influence of the suction of said compressor and prior to the delivery of the refrigerant to said evaporator, t provide for formation of flash gas and consequent cooling of the liquid refrigerant, the compressor operating to effect separation of increments of flash gas upon formation and under substantially the temperature and pressure conditions at which each said increment is formed; and means effective to prevent flow of refrigerant from said chamber to said evaporator during cooling and to initiate substantially unrestricted delivery of the resultant cool, low-pressure liquid refrigerant to said evaporator.

6. In a refrigeration system including a compressor, a condenser and an evaporator connected in circuit, means for delivering liquid refrigerant from said condenser to said evaporator at predetermined conditions of pressure and temperature, said means comprising: an expansion chamber disposed in the circuit intermediate said condenser and said evaporator and within which gradual cooling of the liquid refrigerant and gradual reduction of its pressure takes place; means for removing increments of flash gas from said chamber and for returning each said increment to said compressor under substantially the pressure and temperature conditions at which it is formed; means for isolating the contents of said chamber from said evaporator during formation of flash gas; and means for delivering the resultant cool, low-pressure liquid refrigerant in said chamber to said evaporator.

7. In a refrigeration system including a compressor, a condenser and an evaporator connected in circuit, means for delivering liquid refrigerant from said condenser to said evaporator at predetermined conditions of pressure and temperature, said means comprising: an expansion chamber disposed in the circuit intermediate said condenser and said evaporator and within which cooling of the refrigerant and reduction of its pressure takes place; valve means for delivering to said chamber a predetermined quantity of liquid refrigerant derived from said condenser; conduit means interconnecting said chamber and said compressor to provide for separation of the flash gas formed in said chamber and the return of the same to said compressor under the influ-- ence of the suction of the compressor, such separation and return of each increment of flash gas being effected upon formation thereof and under substantially the temperature and pressure conditions at which each such increment is formed; means for isolating the contents of said chamber 1'4 from said evaporator during formation of flash gas; and means providing for delivery to said evaporator of the remaining cool, low-pressure liquid refrigerant in said chamber.

8. A system in accordance with claim '7, and further characterized in that said conduit means is ofsubstantially non-restrictive dimensions.

9. A. system in accordance with claim 7, and further characterized in ,1 that said last means includes valve means responsive to a predetermined temperature differential between said evaporator and said chamber.

10. In a refrigeration system, comprising: a compressor; a condenser; a storage tank; an expansion chamber; and an evaporator, said compressor, condenser, tank, chamber and evaporator being disposed in flow circuit; valve means disposed between said storage tank and said expansion chamber; and float means disposed within said storage tank and operatively connected to said valve means to maintain said valve means closed, whereby the flow of refrigerant from said storage tank to said-expansion chamber is interrupted until a predetermined quantity of refrigerant has accumulated in said storage tank, said float means being arranged to sense the accumulation of said predetermined quantity of refrigerant and to open and maintain fully open said valve means in response to said accumulation, whereby the substantially unimpeded;

flow of refrigerant from said storage tank to said; expansion chamber is re-estab-lished and sub-- stantial emptying of said storage tank is effected; and said fioat means being furtherarranged to: sense the substantial emptying of said predetermined quantity of refrigerant from said storage tank and to close and maintain closed said valve means in response to said emptying of said storage tank, whereby renewed accumulation of said predetermined quantity of refrigerant is initiated.

11. In a refrigeration system, comprising a compressor; a condenser; a storage tank; an expansion chamber, said expansion chamber being insulated to prevent substantial heat exchange between the contents of saidchamber and the medium surrounding it; and an evaporator, said compressor, condenser, tank, chamber and evaporator being disposed in flow circuit, first valve means disposed between said storage tank and said expansion chamber and arranged so as to open in response to accumulation of a predetermined quantity of liquid refrigerant derived from said condenser and to admit into said expansion chamber said quantity of liquid refrigerant; conduit means connecting said expansion chamber to the suction side of said compressor; second valve means disposed between said expansion chamber and said evaporator; a pair of temperature sensitive elements disposed to sense, respectively, the temperature of the contents of said expansion chamber and of said evaporator; control means responsive to said temperature sensitive elements and efiective to close and maintain closed said second valve means when the temperature of the contents of said expansion chamber exceeds the temperature of the contents of said evaporator by at least a predetermined differential, and to open, and maintain open, said second valve means when the temperature of the contents of said expansion chamber exceeds the temperature of the contents of said evaporator by less than a predetermined differential.

12. A refrigeration system, comprising: a compressor; a condenser; a receiver; an expansion chamber; and an evaporator, the aforesaid components being connected in circuit and adapted forthe undirectional flow of fluid refrigerant from said compressor, through said condenser, receiver and expansion chamber to said'evaporator, and from thence returning to said compressor; valve means interposed between said receiver 'andsaid expansion chamber, said valve means being effective to interrupt flow of reirigerant from said receiver to said chamber until a predetermined quantity of refrigerant has accumulated in said receiver, said valve means being responsive to accumulation of said predetermined quantity to re-establ'ish said'ilow of refrigerant from said receiver-to said chamber, and said valve means additionally'being responsive to substantial emptyingof "said receiver to again interrupt the fiow of refrigerant from said receiver'to said chamber, whereby renewed accumulation of said predetermined quantity of refrigerant is initiated; conduit meansby-passing said evaporator and connecting said'compressor with said chamber to provide for-reauction of the pressure in said chamber and consequentproduction of flash gas and return of the same to the compressor'under the influence of the suction'of the latter; valve means interposedbetween said expansion chamber'and said evaporator; and control apparatus providing for delivery'to said evaporator of the liquid refrigerantin said chamber, said-last means being effective to provide such delivery in accordance with the temperature differential between said evaporator and said Chamber.

1'3.'In a refrigerant flow system including a compressorand an evaporator: a pair of parallel refrigerant flow'paths interconnecting said compressorandevaporator, each of said paths comprising a condenser and .an expansion chamber in'series'fiow circuit, valve and conduit means so disposed as interchangeably to connect one of said :condensers .to the suction side 'of' said .compressort and the other one of said condensers to .thecompression side of said compressor, whereby reirigerant-is'a1ternately removed from one of saidpaths, compressed, and introduced into the other path, and control means soperativel-y con nected to said valve "means toeffect interchange of said compressor connections in response to a predeterminedaccumulation of liquid refrigerant :in that path connected to the compression side of said compressor prior to said interchange.

134. In a refrigerant flow system including a compressor, and an evaporator: a first refrigerant flow path interconnecting said compressor andevaporator, said first path including a first condenser and a first expansion chamber in series flow circuit; a second refrigerant flow path paralleling said first path and interconnecting said compressor and evaporator, said second path including a second condenser and a'second expansion chamber; means arranged to connect one -of said paths to the suction side .of said compressor and the other path to thekcompression side of said compressor, said compressor connections being interchangeable; first .valve means disposed intermediate said first expansion chamber and said evaporator; second valve means disposed intermediate said second expansion chamber and said evaporator; and first and second control meansioperativelyassociated, respectively, with said first and second valve means, and responsive to predetermined temperature differentials betweenueach corresponding expansion chamber and said evaporator to open and close said associated :valve means.

'ZEARFOSS, .JR.

EFEREN'fiES *QITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,106,287 .Doelling Aug. 4, 1914 1,718,312 Shipley June 25, 1929 1,994,037 Gay Mar. 12, .1935 2,094,565 Wolfert Sept. 28, 1937 2,299,811 Feicht Oct. 27, 1942 2,403,220 Hintze July 2, 1946 2,454,537 Atchison Nov. 23, 1948 "2,500,688 Kellie Mar. 14, 1950

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