US2691276A - Refrigerant circuit for air conditioners - Google Patents

Description

Oct. 12, 1954 A. TRASK REFRIGERANT CIRCUIT FOR AIR CONDITIONERS Original Filed Aug. 12. 1950 Patented Oct. 12, 1954 REFRIGERANT CIRCUIT FOR AIR GONDITIONERS Allen Trask, Chicago, Ill., assignor to Welbilt Stove Company, Inc., Maspeth, N. Y., a corporation of New York Continuation of application Serial No. 179,034, August 12, 1950. This application December 9, 1950, Serial No. 200,080 3 7 4 Claims. 1

This invention relates to-a refrigerant circuit for air conditioners. More particularly it relates to a refrigerant circuit utilizing a spring loaded expansion valve.

This application is a continuation of my previous application, Serial No. 179,034, filed August 12, 1950, and entitled Air Conditioner Refrigerant Circuit, now abandoned.

A general object of my invention is to provide a novel and improved refrigerant circuit for air conditioners and the like of cheap and simple construction and of improved operation.

Another object is to provide a refrigerant circuit including a spring loaded expansion valve which will approximate the load responsive performance of a conventional refrigerant circuit using a thermostatic type expansion valve.

Another object is to provide a refrigerant circuit including a' spring loaded expansion valve adapted for efficiently handling a wide range of variable air conditioning loads, the cost of which approximates that of a conventional refrigerant circuit using a capillary tube type refrigerant device.

Another object is to provide a refrigerant circuit wherein a fin tube type evaporator is continually provided with liquid refrigerant throughout its entire circuit or circuits.

Another object is to provide a refrigeration system circuit wherein a fin tube type condenser is continually drained of liquid refrigerant throughout its full circuit as fast as the liquid refrigerant is condensed.

Another object is to provide a refrigeration circuit of low manufacturing and assembly cost which may be dehydrated by the circulation of a dry inert gas throughout, and thus eliminate the need for baking in a high temperature oven under a vacuum as is normally required in circuits using capillary tube expansion devices.

Another object is to provide a refrigerant circuit adaptable to a small self-contained air conditioner and constructed to facilitate service, adjustments, repair, replacements, and recharging with refrigerant while in its installed position.

Another object is to provide a refrigerant circuit for small self-contained air conditioners which is adaptable for dehydrating and charging with refrigerant in a finished cabinet after final assembly, except for the attachment of removable cabinet access covers.

A further object is to provide a refrigerant circuit approximating the cost of a conventional circuit usin a capillary tube refrigerant expansion device, which is less susceptible to the ill effects of moisture and foreign matter entrained in the circuit than the conventional circuit embodying a capillary tube refrigerant expansion device.

A still further object is to provide a refrigerant circuit for room air conditioners approximating the cost of a conventional circuit using a capillary tube, which willaccept, and function with, its'full air conditioning load in a very short period of time. 1 a

Another object is to provide a refrigerant circuit for room air conditioners comprising a spring loadedexpansion valve, which circuit can be checked for proper refrigerant charge by the process of removing the evaporator fan blade and observing the frost-back of the evaporator and the accumulator while the system is-in operation.

Room air conditioners usually employ a refrigerant circuit embodying 'a' capillary tube refrigerant expansion device. Design engineers are confronted with a choice of using a capillary tube or a thermostatic type expansion valve. It is generally conceded that the thermostatic expansion valve imparts superiorperformance to an air conditioner, but the capillary tube expansion device is usually selected because of its lower cost. The industry seems to be socompetitive that top performance is usually compromised in favor of saving a small amount of money. Thus to achieve superior air conditioner performance through the use of an expansion device and refrigerant circuit approximating the cost of a capillary tube circuit of conventional design is a valuable objective for an invention.

The capillary tube circuit leaves much to be desired-with respect 'to factory assembly, performance in the field, and service repairing. The capillary tube is essentially a constant load refrigerant control device which can be fit to a given system'fo'r best performance only under one load condition, and will not give equal efficiency under loads either lighter or heavier than the compromise load under which it-works best. Under light loads, the evaporator is starved of refrigerant and only partly in operation. Under extra heavy loads the capillarytube restricts the refrigerant fiow from the condenser excessively causing liquid refrigerant to accumulate in and fill some of the condenser, thus reducing the effective condenser area and its efliciency. Excessively high compressor head pressures result, and also a corresponding increase in current demand of the compressor motor. Since room assembly line.

overloaded lighting circuit-s this: excessive power demand by capillary tube systems under peak loads is a very serious defect. This invention eliminates these defects.

Another disadvantageof the capillary tube expansion'ldevice that. this inventionovercomes is that capillary tube refrigerant circuits have to be dehydrated by the process of baking them .in a high temperature oven with a high vacuum maintained within the circuit during'the baking process. This baking and vacuum process is made necessary by the fact that the smallpassage within the capillary tubew-ill not pass a dry inert gas, such as nitrogen or carbon dioxide, which might otherwise housed, and which is recommended for systems embodyi ng this invention. When dehydrating with an inert gas the compressor of the refrigeration system is used for pumping the gas through the refrigerant circuit. The exact device used must be of such gas passing capacity-that itwi-ll-pass'i;he-=full com-- pressor capacity without inducing anexcessive head'pressure. -A capillary tube cannotpass the gasvoluine pumped the compressor of its respective system. Ihe expansion valve of this invention will pass inert gas in the volume pumped by'its respective "compressor.

- Ihe dehydrating of a refrigeration system by means of baking under a vacuum is much more expensive and time "consuming-than the dehydrating process carried on with an inert gas.

When the baking and vacuum process is used the refrigerant circuit ofan'air'conditioner, for example, must be completely assembled and dehydrated separately,-'and'then installed as a unit in the final assembly involving usually a cabinet and other components. This separate dehydratin process interfereswi-th the timing and smooth flow of a quantity productionassembly line, and

line at the end'oi whichthe dehydration process is performedwith an inert gas-through one flexible tubeconnection that is used for pressure testing, for filling with inert dehydrating gas, for drawing-a vacuum, and finally for charging with refrigerant. Thus time and: duplication-of eilortis saved by combining the above necessary processes at onelocationatthe'end of the final The savings thus made in assembly through the useof this invention contribute toward cost reductions which bring down u the cost of systems embodying this invention to substantially thesame costlevel of systems embodying theconventional capillary. tube.

The smalldiameter; long passageof capillary tubes used in room air conditioning systems makes them exceptionally susceptible to \blocking by foreign matter and frozenwateraccidentally left in the systems. In room air conditioners 4 bcdying a capillary tube expansion device in its refri erant circuit to require twenty (20) to thirty (30) minutes time after the starting switch is turned on, to progressively accept the full rated load ina balanced operating conditionwith the evaporator normally flooded with refrigerant throughout its full length. This is a severe disadvantage that the user of an air conditioner often regrets. It is highly desirable to have room air conditioners deliver their full rated capacity of cooled air in one or two minutes after the unit has been turned on. Air conditioners embodying this invention will deliver their full rated capacity in cooled air within one or two minutes after being started.

It is generally conceded in the industry that for all practical. purposes the air conditioners very undesirable to everyone involved; the user,

the distributor, the dealer, and the factory that produced the machine. .iAwfieldiservicable .air conditioner is very desirable. This invention makes practical the field servicing of aakhermetically sealed. air conditioning system.

The quantity of. refrigerant charge in rarefrigerant circuit usinga capillary tube cannot be checked after the machine has :been put into operation. "Ihis is. a.serious disadvantage to .a service man because the presence of .a slow leak in a circuit canbest be: determined by the checking of the quantityot refrigerant charge. when such check is possible. This invention creates a refrigerant circuit wherein the; quantity of refrigerant .charge .in an, air conditioner. can. be checked by the processof removing the evaporator-- fan and running theunit to observe frost accumulation on the evaporator and the-.accu- -mulator. {With the normal charge .in circuits of this invention, theevaporator. will become fully frosted: and the accumulator. frosted partway up from the bottom. 'iThe accumulationof less frost than this-will indicate thatsomeof the refrigerant hasleaked out of the system since it left the-factory. The service. mancan in the event ofaoleak then repair it and-recharge the machine with refrigerant;.-wi-thout removing it from its installedposition. .Thisisa time saving and moneysaving advantage.

. Theseand other-objectsand advantagesof my inventionwili more fully. appear from-the following description made in connection with the accompanying drawings, wherein like reference characters refer-to.similarparts throughout. the several viewsandxin which:

llE'f-igure Lisa diagrammatical; view ofoneembodiment of. my invention showing the arrangementof the various elementscontainedtherein; FigureZ .isa vertical sectional view-of one type of expansion valve utilized in my invention;

Figure 3 is-a verticalsectional view ofanother type of valve which: maybe utilized in myinven- 7 tion.

---Figure sis avertical sectional view of still another type of expansion valve-which may be utilized in my invention.

'One embodiment of my invention-includes, as shown in'Figure 1, a compressor 5 of the hermetic type havinga reciprocating piston (not shown) and adapted for compressing a refrigerant of the type known commercially as Freon. The outlet of the compressor 5 is connected for fluid communication by a conduit 6 to the inlet of an aircooled fin tube condenser l. A conduit 8 connects for fluid communication the outlet of the condenser l with the inlet of an expansion valve indicated generally as S. The outlet of expansion valve 9 is connected by a fluid conduit Iii to the inlet of the evaporator indicated generally as H. The evaporator is that portion of the air conditioner which absorbs the heat from the air which is to be recirculated through the room. The outlet of the evaporator l l is connected by fluid conduit l2 to an accumulator it as shown in the- Figure l. A suction conduit it connects the upper portion of the accumulator it with the inlet of the compressor 5.

A portion of the conduit 8, as best shown in Figure 1, is arranged in heat exchange relationship with a portion of the conduit is to form a heat exchanger which has been indicated generally as it. That portion of the conduit 8 has been indicated as 8a in Figure 1 and that portion of the conduit It has been indicated as Ma. In practice the heat exchange relationship between the two conduits is obtained by metallically fusing them together with solder for a relatively long length. Often the contacting portion of conduit to with conduit Me is formed in the shape of a loop to confine a long contact length in a relativeiy small space.

The valve 9 may be any of three types shown Figure 2, 3, and l. Figure 2 shows a vertical sectional view of one type of expansion valve having an inlet passage [6 which leads to valve nozzle ll. At the lower end of valve nozzle H is a valve seat it which is adapted to receive a ballpcinted needle l 9 which in turn is carried at the inside of the bottom of movable cup 20. The cup 24) fits outside the nozzle l7 with ample clearance to permit a fluid to pass therebetween. There is an aperture 2! formed in the side of the cup 29 which at all times establishes communication between the outlet 22 of the valve 9 and the interior of the cup 25. The cup 20 is provided with an outwardly extending flange 23 against which a coiled spring 24 abuts. As shown, the spring 2 3 encircles the cup 20 and pushes upwardly against the flange 23.

A pair of rods 25 have their lower ends resting on the upper surface of the flange 23 of the cup 20. These rods extend upwardly through the main body of the valve proper through apertures provided therefor. These apertures are of sufiicient diameter to provide clearance around the rods 25 for free longitudinal movement thereof and for transmittal of refrigerant vapor pressure therethrough. The upper ends of rods 25 press upwardly against the lower surface of diaphragm 25. Mounted above the diaphragm 26 is a coiled spring 2? which pushes downwardly thereagainst.

' The tension placed upon the spring 21 may be regulated by an adjustment knob 28. The entire upper portion of the valve is protected from dust and the like by cover 29.

Figure 3 shows a valve of somewhat similar construction to that shown in Figure 2 wherein like parts are identified with like numerals. In

i9 fromits seat 18 against the oppositepressure of spring 24 and the refrigerant vapor pressure under the diaphragm 26. In this structure a refrigerant, passing from valve seat is to valve outlet 22, is confined to pass through a restriction tube 3i.

Figure 4 shows another modified form of the expansion valve structure of Figure 2 wherein similar parts are identified with like numerals. In this structure the needle id as attached inside the bottom of the movable cup 28 and the cup surrounds a cylindrical guide 32 for maintaining needle lil aligned with its seat it. The holes 33 in cylindrical guide 32 provide a restricted passage for the refrigerant, passing from valve seat 23 to valve outlet 22.

In each of the three expansion valve structures shown there is a spring loaded metal valve engaging a valve seat, a valve outlet, and a means for restrictingthe flow of refrigerant between the valve seat and the valve outlet.

My commercial adaptation of my invention to room air conditioners of one horse power and less in size, are the first structures embodyin my invention that have been seen, tested and investigated by engineers skilled in the art. The operation and the results obtained in the functioning of a refrigerant circuit constructed in accord ans with invention has not, up to the present time, been completely explained to the satisfaction the engineers skilled in the art who have the opportunity to observe and study the functioning and results of a reduction to practice. The functioning of such a circuit will be described below in accordance with what I believe to be the best probable explanation available.

I have had opporturnties to carefully observe the functioning and results obtained by my invention in refrigeration testing laboratories, in room air conditioners, and I find these results highly desirable. The reasons for these results obtained will be explained below to the best of my ability. However, it is possible that there may be error in this explanation.

In operation, compressed refrigerant vapor is pumped from the compressor 5 through conduit ii to the condenser E where it is condensed to a liquid by the transfer therefrom of its latent heat to cooling air drawn through the condenser by means not shown. Liquid refrigerant from the condenser i flows through conduit 2 to heat exchanger i5 from whence it enters expansion valve 9.

For the purpose of this explanation, it will be considered that the expansion valve 9 is adjusted to maintain. 4-6 lbs. refrigerant vapor pressure in the evaporator of a room air conditioner with the room air at degrees dry bulb tem-- perature and 67 degrees wet bulb temperature, a relative humidity condition of 50%, and the incoming condenser air at the dry bulb temps ture of degrees. These conditions will be hereinafter referred to as the normal load.

When the normal load is imposed on evap orator a substantially solid stream of liquid refrigerant will flow from the condenser l, through the heat exchanger l5, and into the expansion valve 9. The liquid when viewed through a sight glass put in conduit 8 for test purposes has very few bubbles in it, and the sub-cooling has been observed at approximately 12 degrees. It ap pears probable that considerably more refriger-- ant vapor leaves the condenser "E than arrives at the expansion valve 9, due to condensation of the vapor within the heat exchanger. The presence of bubbles indicates that the condenser l is completelydrained' of liquidrefrigerant'a'nd ,its;;in side surfacetherefore is all in use in the process of condensing refrigerant from the vapor to, the liquid state. ;It isone of the important obj ectives of this invention to .cons truct a refrigeran circuit wherein the condenser is always working at full eficiency-by reason of its being drained of liquid refrigerant as; fast as it is condensed.

ifhe refrigerant which issupplied to the valve Qby the conduit 8 isconducted through the valve inlet passage i6 and into the valve nozzle ii. The flow of refrigerant between the valve seat if; and theneedle is is governed by a combination of the pressure existing within the evaporator H and the physical form of the refrigerant as; it flows between ;t -e valve ,seat; is and the restriction between the valve seat is and the valve outlet 22. Ashereinbefore explained, the restrictionin the valve shown in Figure 2, is the hole 2! in the cuptdand the clearance space between cup wand nozzle H. In Figure 3, the restriction is theoriflce in the restrictor tube iii. In Figure l, the restriction is made by holes 33 in cylindrical guide 32.

As the refrigerant flows from the valve seat it?" to the valve restriction, a portion of the liquid refrigerant becomes vaporized into what is known in the industry as flash gas. This flash gas is brought about by the pressure reduction on the refrigerant as it passes the nozzle 18. lhe amount of flash gas produced is determined by the amount of sub-cooling in the iquid refrigerant,,and the pressure on the refrigerant at the point where theflash gas occurs between the valve nozzle. 18 and the valve restriction. The

restriction to refrigerant flow is more effective against refrigerant with much flash gas entrained, than it is against a flow of liquid refrigerant with a minimum of flash gas. In other words, the amount of refrigerant passed by the restriction to the outlet 22 of the valve is inversely proporional to the amount of flash gas in the refrigerant. Thus the amount of flash gas, and the factorscontrolling the amount of hash gas in circuits involving this invention, are of major importance to the invention.

As stated above, the refrigerant flow through the valve seat i8 is partly determined by the pressure within the evaporator H. The needle 19 is arranged to increase the valve opening upon a decrease of evaporator pressure, and to decrease the valve opening upon an increase in evaporator pressure. This is brought about by the combination of evaporator pressure upward on diaphragm 1-26 and the counteracting spring pressure of spring 21 downward on the diaphragm. The diaphragm movement is transmitted through rods 25 to open and close the valve seat H) by moving the needle 19, through its pressure on flange 23 of cup 20.

A circuit of my invention may be set for the evaporator pressure, and therefore temperature, desired under normal operating conditions by putting the system under a normal load, and then adjusting the expansion valve 9 manually by.

adjusting the pressure on. spring 2'1, through turning the adjusting screw 28.

It has been observed in testing a room air conditioner embodying my invention that under an increased load on the evaporator H due to either warmer air, increased relative humidity of the air, or both, then the pressure in the evaporatorwill rise substantially in proportion to the increase in load. It is my belief that this evaporator pressure, and therefore temperature, in-

. decreasein thevalveopening will restrict it. In

any .event, increased-loads result in increased refrigerantflo-w into the evaporator to absorb the heatdoadand carry-it to the-condensingunit.

It has also been observedin testinga room-air conditioner embodying my invention, that under a decreased load-on, the evaporator H due to either cooler air, reduced relative humidity of the air, 01:,both, then the-pressure in the evaporator will fall substantially in proportion to the decrease in load. It is my belief that this evaporator pressure, and therefore temperature, reduction is broughtaboutby an increase in the amount of flash sas between the valve seat 68 and the valve restriction under increased loads. The increased proportion of flash gas produces a foam or froth in; the refrigerant to which the valve restriction offers increased restriction to ilow, and thereby under the influence of the decreased load on the evaporator, the refrigerant pressure in the evap- ;orator falls. ;The decreased evaporator pressure delivered to theunder side of the diaphragm 2S through -the clearance around rods 25, will bring about an increased valve opening, but it appears from the operatingresults that the increase in the amountof flash gas will decrease the refrigerantilowmore than the resulting small increase ;in the valveopening willincrease it. In other words, under evaporator load less than normal the valve restriction seems to take over refrigerant throttling control from the diaphragm. action. In any event, decreased loadsresult in decreased flow ofrefrigerant to theevaporator and lower pressures and. corresponding lower temperatures in the evaporator.

After the refrigerant passes through the circuit or circuits of the evaporator H, it will pass into ;the accumulator l3 as a combination of liquid and vaporized-refrigerant. Since the final throttling ,control on the refrigerant is brought about by the proportion of flash gas in the refrigerant just be- 1 fore it encounters the valve restriction, some uncondensed vapor. always leaves the condenser with the liquid. refrigerant. The. condenser is kept drained of liquid refrigerant by the need for some vapor in the expansion valve for contributing to the throttling action in the valve. Therefore, in myinvention, all the liquid refrigerant is passed out of the-condenser as fastas it is condensed, through the expansionvalve 9, and into the evaporator: ll.

The circuit is chargedwith a measured quantity of refrigerant that will under normal load be sufviicient to. keep the, evaporator circuits supplied with liquid refrigerant and the accumulator l3 partially full of liquid refrigerant. The amount of liquid refrigerant in the accumulator is a surplus for the circuit from which more or less vapor supplied to the circuit according to load demandsand variable vapor pressures elsewhere in v the circuit. The accumulator i3 is constructed as aliquid trap. so that under no circumstances will 9 liquid refrigerant flow to the compressor from the evaporator.

From the accumulator is saturated refrigerant vapor flows through conduit id to heat exchanger 15 wherein heat from hot liquid refrigerant in conduit 8a is conducted through a solder bond to conduit l la wherein the refrigerant vapor becomes superheated, and the liquid in conduit 8a becomes sub-cooled in a corresponding amount. As hereinbei'ore explained, some of the refrigerant vapor from the condenser passes through or into the heat exchanger l5. Condensing of a portion of this vapor will materially afiect the amount of sub-cooling of the liquid refrigerant in the heat exchanger. The more latent heat of condensation given up to the suction vapor in conduit Ma, the less will be the liquid sub-cooling.

From the heat exchanger E the superheated refrigerant vapor flows from conduit i la into the suction inlet of the compressor 5 wherein it is compressed to the condensing pressure required by the condenser l, and then discharged into the condenser. This completes the refrigerant circuit.

Referring to Figure 3, in this structure of expansion valve the valve restriction responsive to the proportion of flash gas entrained in the flow of refrigerant is the restrictor tube 3 l as hereinbefore explained. When this expansion valve is applied to air conditioning systems of various capacities, the internal diameter of the bore of the restrictor tube may be as follows to serve the purposes of my invention.

Tons capacity: Restrictor orifice diam., inches /a /32 1-2 "its 51O 1G-l5 1/ The variation of evaporator pressures between low and high loads may be made to range between 5 pounds and pounds as desired by increasing or decreasing the restrictor bore diameter as set forth in the table above. When the fan or blower commonly used in air conditioning to circulate air over the evaporator, is stopped, while the remainder of the system is in operation, the evaporator pressures and temperature will fall below freezing temperature to cause frost to accumulate on the portions of the evaporator and accumulator which enclose liquid refrigerant. By this frosting process, the quantity of refrigerant charge in the system can be checked for proper amount.

The expansion valve 9 will pass an inert gas in this circuit in the volume pumped by the compressor. Thus in factory dehydrating an inert dry gas may be used for the purpose of dehydrating, instead of the more costly process of dehydrating in a high temperature oven under a vacuum within the circuit. Also the expansion valve of this circuit will pass foreign matter and/or ice crystals accidentally entrained within the circuit, more easily than will a capillary tube when used as a corresponding expansion device. The movement of the valve needle induced by pressure variations on the diaphragm assists in the passing of foreign matter through the valve seat.

The structure disclosed in this application is entirely new to the art and provides a number of advantages over the types of circuits known. It accomplishes the ten (10) valuable objectives enumerated in the first part of this specification.

illary tube expansion devices commonly used.

Field service involving opening, reps 1g, and recharging the circuit with refrigerantis made possible. My circuit has an efiiciency, sensitivity,

and control -approximately equal in performance to the thermostatic expansion valve but has a cost substantially less approximating the cost of circuits embodying conventional capillary tube expans'ion devices;

It will, of course, be understood that various changes may be made in the form, details, arrangements, and proportions of the various parts without departing from the scope of my inven tion.

What I claim'is: I

1. An air conditioner refrigerant circuit including in combination a compressor, a condenser, a heat exchanger, an expansion valve, and an evaporator interconnected conventionally in a series circuit, said expansion valve including an inlet and an outlet, a valve-seat, an actuating diaphragm arranged with one of its sides subjected to refrigerant pressure on the downstream side of said valve seat tending to throttle the valve, a spring together with atmospheric pressure operative on the opposite side of said. diaphragm and tending to open said valve, and a restricting refrigerant passage between said valve seat and said outlet arranged to effect pressure drop in the refrigerant passing therethrough in direct proportion to the amount of vapor refrigerant mixed with the liquid refrigerant flowing therein, whereby the pressure and temperature in said evaporator is lowered in response to an increase of refrigerant vapor passing through said restricting passage.

2. An air conditioner refrigerant circuit including in combination a compressor, a condenser, a heat exchanger, an expansion valve, and an evaporator interconnected conventionally in a series circuit, said expansion valve including an inlet and an outlet, a valve seat, an actuating diaphragm arranged with one of its sides subjected to refrigerant pressure on the downstream side of said valve seat tending to throttle the valve, a spring together with atmospheric pressure op" erative on the opposite side of said diaphragm and tending to open said valve, and a. restricting refrigerant passage between said valve seat and said outlet arranged to effect pressure drop in the refrigerant passing therethrough in direct proportion to the amount of vapor refrigerant mixed with the liquid refrigerant flowing therein, whereby the pressure in said evaporator may be varied between high and low loads in a range between 5 pounds and 10 pounds per square inch as desired by increasing or decreasing the restriction of said restricting passage.

3. An air conditioner refrigerant circuit including in combination a compressor, a condenser, a heat exchanger, an expansion valve, and an evaporator interconnected conventionally in a series circuit, said expansion valve including an inlet and an outlet, a valve seat, an actuating diaphragm arranged with one of its sides sub-- jected to refrigerant pressure on the downstream side of said valve seat tending to throttle the valve, a spring together with atmospheric pressure operative on the opposite side of said diaphraemandatendingztouopenesaidn valve; are:

stricting :refrigerant *passagegbetweemsaidqvalye seat yand -said ;out let,:,and ;means includinevsaid. restriotionto:efleotawpressurerdrop the-re frigerant passing 'theret-hrough toisaid .evaporator; whereby the re,frigerant;:pressure -v and tem:

peraturedmsaid evaporator jsrreduced -in,-- direct proportion to theamountwfvvapor refrigerant mixed :with the liquid refrigerant fiowmgthrough" said restricted rpassagewresultin e in: a; moderate.-

rise andv fall of evaporator: temperature .zin; 1 response to; a:;corresponding:-rise and :falL in :the 3 temperaturechair-entering-said evaporator.

4.11mair onditionerr refri erant ircuit. in:

eluding in combination a compressor;,a;con-r.

dense1:; at xchanaers m expansion valvefiand anev poratorinterconnectedconventionallymas;

series mircu-itrgsaid expansionzrlvalve ainclu inav r inlet, and an:out1et.:a:,-va1ve seat; anactuati-ng-diawphragm arranged with one of its sides subjected;

to refrigerant pressure on the downstream side of said :valve.-,seat :tendingzto zthrottlethe fvalve a spring togetherwwithratmospherie pressure operative on' the. opposite side. sofxisaid *diaphragmriand tending :to open said-waive;v agrestriotingr refrig erant passage betweenrsaid valve seat and said: outlet; and means including gsaid restrictionzto 9 Number efie'ct aminimum pressure drop in the refrigerant passing therethrough to said evaporatornvhereby the; refrigerant pressure in. said evaporator, is varied in a range between 5 and 10 pounds per square. inch in direct proportion to the amount References Cited in the file of this patent UNITED STATES PATENTS- Name Date 1,878,798 Mufliy Sept. 20, 1932 1,965,552 Lear July 3, 1934 2,099,085 Shrode Nov. 16, 1937 2,154,874 smith Apr. 18, 1939 2,220,831 Swart Nov. 5, 1940 2,221,062 Starr Nov. 12, 1940 2,291,362 Warneke July 28, 1942 2,459,173 McCloy Jan. 18, 1949 2,463,899 Nicholas 1 Mar. 8, .1949 2,466,863 Phillips Apr. 12, 1949,

Augtrey et a1, Apr. 3, 1951

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