US2884764A

US2884764A - Reversible cycle system

Info

Publication number: US2884764A
Application number: US549213A
Authority: US
Inventors: Gert K A Siggelin
Original assignee: DESOMATIC PRODUCTS Inc
Current assignee: DESOMATIC PRODUCTS Inc
Priority date: 1955-11-25
Filing date: 1955-11-25
Publication date: 1959-05-05
Anticipated expiration: 1976-05-05

Description

y 1959 e. KEA. SIGGELIN 2,884,764

REVERSIBLE CYCLE SYSTEM Filed Nov. 25, 1955 IJ4FUSES r68 r66 s-rAFcrsR. I oy m ENSING BULB Him AIRSTREAM LF '1 l I l #24 COOLING HEAT l- (asnsm t ounc) REVERSIBLE FLUID" a FLOW 49 FAN 46 2 5 SOLENOID COMPRESSOR PILOT VALVE MOTOR s fi man/lone BULB I F Ahmaaa as r/a 69 4I-WAY VALVE\ 46; SOLENOID PILOT VALVE r20 I COMPRESSOR INVENTOR GERT K. A. S/GGEL/N .BY M

ATTORNEY- U ited State patnt REVERSIBLE CYCLE SYSTEM Gert K. A. Siggelin, Falls Church, Va;, assignor' to DesomaticP'roducts, Inc., Falls:Church, Va., a corporation ofaDelawzu-e Application November25,.1955, SeriallNo. 549,213

20Claims. (Cl. 62-81) This invention, relates to an improved, reversible fluid flow-thermodynamic cycle. and apparatus operating with suchfor removal of vapors from. gases including dehumidification and other practical applications of such cycle.

Thisinvention further provides an improved devaporizingof. gases in a reversible fluid flow thermodynamic cyclewherein vaporremoval from gasesis effected by refrigeration ofthe gas in contact with refrigerated coils,

wherein .the refrigerant passing through separate coils,

such: as the evaporator and condenser of a compressed gas. refrigerating cycle, as well as gas flowing serially in. contact: with these coils are both periodically re,- versedfor improved devaporizing andienhanced thermo? dynamic. efiiciency of the refrigeration: cycle.

The invention further provides enhancedcontrol; for optimum.dehimidification of gases with; variably volume, sensible heat and moisture contents.

Inoneaspect of this invention the gases may bev efiiciently. devaporized. For instance, air may be dehimidified. to dew points below 32 F-. or even below F., as desired by, periodically reversingthe gas flow in se-v quence, first over a cold refrigerant evaporator coil and x then over. a. relatively warm condenser coil efliciently to deposit its moisture uponthe. cold evaporator'coils.

Periodically when the-heattransfer efiiciency, tends to be now heated warm,- condenser, coil has :its ice .film rapidly melted. Onev result of this cycle. is: a. continuous" and eflicient heatexchange firstvto' cool thegas to depositmoisture on the cold evaporating coil and. thereby. effecting dehumidification to a dew point close to thetemperature. of that cold coil, without interference. of. an

ice deposit, thereby producing an; unusually low dew pointinthe gas. overv the warm condensing coil of. the refr1gerating system the gas becomes reheated to normal temperature, but, remains. very dry gas of, even lower relative humidity,, while most efliciently cooling the condenser. of there frigerating system to enhance the efliciency of, that sys. tem.

Thus this system is .a controllably reversed refrigerating system comprising both a condensing and an evaporating-coil anda-'controllablyreversed gas cycle. passed in'sequence overthese coils for highly eflicient'dehumidification to any desired 10w dew point while simultaneous- Then passingthecold dehumidified gas;

1y enhancing the: refrigeration. system efliciency. For

further improvement in efliciency of thesystem, the fan;

reversible with the refrigeration system, may be operated: at controlled speeds responsive todesired temperatures For or vapor content of the gas passed over the coils. example, a gas of high moisture content or high sensi ble heat is desirably passedmore slowly over the coils than gas under opposite conditions.

There are other practical applications of this. system besides efficient devaporization ofgases and enhanced efficiency of a refrigerant cycle. For instance, while it may be desirable to dehumidify a gas to a dew point below such as'is'practically' available under present sys' terns, it is also desirable in air conditioning systems to" reheat the cold dehumidified gas to a comfortable temperature thereby greatly reducing its relative humidity.

In another aspect Where vapors are desirably removed from a. gas such as in a natural gasoline recovery system from petroleum gases, that natural gasoline may be removed by passing the. wet gas in contact With refrigeration coils tocondense the liquids carried thereby upon theevaporator coil for recovery thereof. However, the gas itself "becomes cooled, oftimes to an undesirably low temperature, resulting in loss of gas pressure on the system and the passage of the devaporized cold gas in.

contact with the warm condensing coil of therefrigerating system warms and restores the. sensibleheat. of the. gas, thereby increasing its pressure to substantially the original pressure of they system thereby maintaining the system ata substantially constant pressure and obviating distribution problemsin gas flow.

The present system, moreover, allowing passage of gasesat acontrolled rate over evaporating and condensing coils in seriesmay be controlledto such rate as 'not only enhances the efliciency of the refrigerating system but also may correspond to a rate adjusted to maximum efficiency to remove the vapor content of. such gases.- For instance the timing of the.

to a maximum degree. reversal of cycles may be controlled by the ice deposit on the evaporator coil as well as other desirably con trolled variables of the system, or it maybe'simply'set. for periodic reversal regularly with passage of a certain time period.

The system will be further explained in' conjunction;

with. the drawings, appended hereto wherein:

Fig. l illustrates diagrammatically the: complete sys. tem; and

Fig. Zis-an overallwiring diagram for such-system.

ReferringtolFig. 1, arefrigerant gas such as.:Freon7 is compressed in compressor. 10, of conventional refrigeraant compressor construction; to a pressuresuflicient' to;

liqui fy that. gas when: cooled 'lb610W its critical: tempera.

turevand passed UHdEIJSUChfPIBSSUI'C through arliner124. to.a 4-way valve.14-.=and thence; by. way of:.line-16':toi" a condenser COl-l 18i. Thattcondenser. coil-may xbezsanya conventional; refrigerant heat exchanger designed. for

cooling of the-refrigerant gas in contact with v a cold.gasi that has been dehumidified. For example, .it'. may-be ofi conventional fin .=coil Lor other. known' heat exchanger con struction;

The hot? compressed gas becomes-condensed incoil? 18' tona liquid refrigerant-under the relatively-high pres sure of the compressor 10 and :passesthrough line 20 by check valve 22 in line 24to' receiver26"; It passes from receiver" 26*through' a conventional thermo expansion valve 28 as controlled-by a remote control'bulb 30 sensitive-to the degree of super heat containedin.

low pressure refrigerant gas, The gaseous, and"liquid- Freon from thermo expansion va1ve28'f pass through line.

32 by way of check valve 34 and'thence into the evaporator coil 36 where it is evaporated to a gas and de- Patentedi May- 5, 1959-- velops lowest refrigerating temperature well below 30 F. and often as low as --30 F.

The low pressure cold gas from evaporating coil 36 is returned to the low pressure side of 4-way valve 14 byv way of line 38 and thence returned to the suction side of the compressors by way of line 40. As shown a conventional sensing bulb 30 responsive to the temperature of the gas in line 40 is set to control the thermo expansion valve 28 at about 5 of superheat in the return gas.

A gas lead duct 42 is taken from line 12 to bleed a small quantity of refrigerant gas under high pressure and serves to actuate the 4 way valve through a conventional diaphragm valve control 49 which actuates arm 44 thereby moving the 4-way valve by pneumatic pressure for reversing the direction of flow between

ducts

16 and 38. After actuation to reverse the valve 14, gas in line 42 is returned by way of line 46 to the low pressure line 40. While the actual reversal of the vane position of 4-way valve 1-4 is effected by the gas pressure produced in compressor through

lines

12 and 42, the actual operation of the valve reversal mechanism is triggered by a small solenoid actuated pilot valve 48 (Fig. 2) which directs the flow of gas to the diaphragm control 49. The solenoid controlled gas pressure actuated valve control 49 for a multiway valve is of known construction and accordingly is shown here only diagrammatically.

When the refrigerant flow in the refrigerating system is reversed, as triggered by the solenoid pilot valve 48, gas pressure in line 42 actuates arm 44 and reverses 4- way valve 14 to its dotted line position. In that position compressed gas in line 12 passes first by way of duct 38 to coil 36, which now becomes a reheating or condenser coil, and the condensed compressed gas therein then passes through line 32 into line 24 protected by check valve 50 and again passes to receiver 26. From receiver 26 the refrigerant passes out through thermo expansion valve 28 and into line 20 protected by check valve 52, and thence into evaporating (cooling) coil 18 from which it finally returns to 4-way valve 14 by way of line 16 and thence to the suction side of the compressor 10, again by way of line 40. I

As shown in the full line position of the apparatus of Fig. l, the coil 36 is the evaporator coil and produces the lowest temperature while coil 18 is the condenser coil and will be heated by the condensationof the condensing refrigerant. Both coils are mounted within a gas duct 59 through which gas passes in the direction of the full line arrows. That gas, passing first over the cold evaporator coil 36, is cooled to below its dew point and deposits its condensed vapor content on the surface of coil 36 as liquid. The cold gas then passes onward in contact with coil 18 which, relatively warm, reheats the gas such as air to approximately the same temperature as it originally was before cooling. The reheated gas then passes out of duct 59 as reheated gas of even lower relative humidity. A reversible fan 60 is mounted preferably, but not essentially, between the coils, inducing flow over the cooling coil and forcing flow over the heating coil. Liquid as deposited moisture accumulating on coil 36 drips off the coil into a sump or pan 61 to receive the accumulated liquids at the bottom of the cold coil, from which the liquid may be continuously or periodically drained through duct 63, controlled by a valve 65. When solid phase liquid such as ice begins to accumulate on the cold coil 36, the flow of gas over both coils is reversed by reversing the fan 60, while simultaneously reversing the refrigerant flow as described. Coil 18 therefore then becomes the cold evaporator coil of the refrigeration system and coil 36 becomes the hot condenser coil thereof. This reversal of the fan then causes the air to flow in reverse direction as shown by the dotted line arrows and a similar sump or pan 67 mounted belowcoil 18 receives de- 4 posited liquid drained from coil 18 and this liquid is withdrawn therefrom through duct 69 continuously or intermittently as controlled by valve 71.

Fan 60 is operated at a speed either coordinated for continuous speed variation with the vapor content or temperature characteristics of the gas passing through duct 59, or that speed control, on the same principles will 7 be set at two or three alternate practical speeds for the particular gas characteristics.

By this variation, for example, a gas with a high sensible heat or a gas with a high vapor content may be passed more slowly over the cooling and reheating coils than one which is already at approximately its dew point or one which may have little moisture content to deposit, or even one wherein extreme dew point lowering is not necessary, and therefore the gas could be flowed over the coils at greater speed. Since the deposited moisture is continuously or intermittently removed from the system, and the cycle is reversed as soon as the accumulation of solid phase liquid or ice upon the cooling coil (evaporator) takes place, or as soon as heat exchange by ice accumulation has been reduced to a selected value, the practical temperature of the gas cooled by the cooling coil may be almost as low as the temperature of the coil itself because of the efiicient heat exchange in the absence of ice or at some practically fixed limit for dehumidification efiiciency. For these reasons the dew point of the gas may be reduced as desired to a temperature far below i that of ordinary dehumidifying systems wherein the dew point of the gas cannot be reduced below the temperature of ice or solid phase liquid upon the cooling coil. Upon reversal of the refrigerant flow there is momentary, but,

practically very little lag in readjustment of temperatures I of the respective coils.

Moreover, it will be appreciated that a cold gas chilled in contact with the cooling (evaporator) coil becomes more highly efficient to cool the condenser coil over which ,it passes in reheat thereof. This makes the refrigeration system per se more efficient. Finally, following the known air flows and with means controlled by a timer circuit for reversing the flow of air over the respective coils. The speed of the fan motor may be controlled for continuous variation by varying the resistivity and thereby the current passing to the fan motor, continuously varying with the temperature sensed in the air stream by a sensing bulb. However, for most practical purposes the fan motor may be controlled at two difierent selected speeds for operation at either, and at temperatures alternately in either of two practically selected temperature ranges.

As shown in Fig. 2 the fan 60 (Fig. 1) is mounted for drive on the armature of reversible fan motor 62. The fan motor derives electrical power as a single phase motor from two lines 64 and 66 of a three phase current supply including a third line 68 thereof used for powering a three phase compressor motor 70. One electrical lead 72 is connected to a contact pole 74 of a temperature sensitive snap acting switch arm 76 which feeds the current to respective current contact leads 78 and 80 for either of two speed current supply. These leads 78 and 80 connect with respective coil windings of either of the two speed wound single phase fan motor 62. The switch arm 76 comprises a micro switch of standard construction which, as shown diagrammatically, is actuated by an arm 82 connected to a diaphragm 84 whoseposition is variable responsive to fluid pressure above the diaphragm. exerted' by fluid in a sensing bulb- 86' exposed tov the gassuchsas movedby the fan 60; and the fluid ofthe sensing bulbnis connected-tothe top of the diaphragm spacerthrough a capillary tube 88 for transfer of: fluid pressure-tothe diaphragm 84. Theother circuit lead 90 completes the current flow to the motor 62;

'Fhe motori 62 in knownconstruction has: a,,reversing ci1 (not shown) which determines the. direction ofrotation-gof the armature as controlled by the polarity of a capacitator 92 inv circuit by way of lead 94 with one end ofiisaid coil-and 96 at the other. A lead 98 takenfrom line; 78 passes polarizing current through aswitch-arm 101}: to direct current to. either ofleads 94 and 9.6 byway rson- 116; Coil 116 is energizedby leads 118and' 120 carryingcurrentfrom lines 122 and- 124 whichsimultaneously energizea second solenoidof pilot valve 48,

lines

122 and 124 being directly connected to the-power input circuit lines 64 and 66. A timer motor 126 is energized by leads128: and 130 connected respectively to power inlet leads 90 and 72. The timer motor which may be'a small electric motorcontinuously rotating and geared to a. selected:v slow rate actuates by its armature through a cam driven contact switch arm 132 in line122 makes andbreaks the circuit therein according to a predetermined timeperiod.

When the switch arm 132 is closed by timer motor 126 to complete the circuit in line 122, the solenoid pilot valve 48 is energized to reverse the position of the 4-way valve 14, as explained above, and simultaneously energizes coil 116 thereby moving the solenoid armature and its arm 11'4-to lower both switch arms 100 and 108 to dotted line position, thereby reversing the polarity of capacitator 92 andsimultaneously thereby reverses the direction of fan motor 62.

The-speed control of the fan in either direction is relatively independent of the direction control of that motor 62'whereby switch arm 76 will be moved to high or low speed (dotted line) positions as controlled independently by sensing bulb 86 responsive to the temperature of the airflow.

While the temperature control circuit as shown is for alternate speeds high and low, preselected, the speed variation circuit may be continuously variable with the temperature and forthat purpose instead of the snap acting switch 76 arrangement as shown, a variable resistor may be substituted to merely vary the current to the fan by temperature or other continuous control element for-purposes of varying the fan speed.

Similarly, while a timer comprising the electrical motor 126; is shown to give, by a continuous rotary drive, a periodic measurement of time, the solenoid 116 may be made responsive to other control factors in the cycle to obtain reversibility of the fan motor at a critical point offthe cycle. For instance, instead of the control motor 126 as measuring a continuous time period, a control such as .the resistivity of an ice layer deposited. upon the evaporator coil 36 of the refrigeration system may be used, whereby after a layer of a certain thickness or resis t-ivity or heat transfer differential results, that critical value, may be used as electrical control upon switch 132 to eifect reversal of both refrigerant flow by solenoid 48 aswell as fan motor 62.

Therefrigerant gas compressor motor 70 is preferably a three-phase motor actuated by a master switch 134 passing current to each of lines 64, 66 and 68 which may be conventionally protected by fuses 136. The three-phase motor- 70 is protected by a conventional overload circuit comprising resistors 138. in each oftwo of the three lines,

' ice.

each: resistorcooperatingwith a normally closed switcli 1 46to open the same. whenoverloading current, developing anexcessive temperature in resistors 138, is present; In orderto, make the compressor circuit independent of the fan circuit; thereby allowing the compressor power to be cutoff While allowing the'fanmotor to continue,

an additionalswitch 142 is placed in the circuit which isprotectedby a starting coil 144 and condensers which in: turn energizes the three switches 146- to closed position. The entirecompressor-circuit portion enclosed within the dotted line box is merely aconven-tional startercircuit for a heavy dutycompressor motor with overload protection, While as-shown the compressor motorfor heavy duty isof'three phase-type, for smaller installationsanordinary single-phase compressor motor may be substituted.

Asthus described, animproved thermodynamic cycle is providedhaving improved utility for several purposes.

For example, inasmuch as vapor containing gases are cooled-to approximately the temperature ofthe evaporator coil of the refrigeration system without substantial solid phasecoatingto develop upon the refrigerating coil in which eventthe dew' point will-vary with the heat transfer up to the dew point at the meltingpoint of the Suchintermediate can also be obtained by operating under-other-conditions ofreduced heat transfer such as by passage of gas oven theevaporator coil at higher rates.

In a further advantage of such system the-relative 'humidity of a low dew point gas is greatly decreased byreheat of-the gas.

As another advantageous use of the present system,

the-refrigerant cycle issub'stantially increased inefficiency by the; cold-gas produced in contact with the evaporator coil to usethatcold gas as-a more efficient cooling medium-for thecondensing coil.

As a further improvement in the art, thesystem-herein described provides for flow of gas correlated with a particular refrigerant system to-flow the gas fordehumidifi cation: andreheating at a rate for optimum refrigerationefficiency as well as for optimum dehumidification efii-' ciency sothat the I system is flexible to handle gases of variable moisture: as well as the sensibleheat contents.

Certain modificationswwill occurto those skilledin the-- art and such variations of-thea system as are-known for dehumidification of' gases, for air conditioning and for operation and constructionofrefrigeration systems comprising gas compression. and expansion may be used It is accordingly intended thatthe description" -given-herein be-regard'ed as exemplary and not limiting herein.

except as defined in'theclaims appended'hereto.

I claim: 1 A-reversible thermodynamic cycle system comprising arefrigeration apparatus includinga refrigerant gas compresser, a refrigerant condenser, a refrigerant evaporator, and duct means interconnecting said refrigeration apparatus elements to pass refrigerant from the com pressor to the--condenser and then to the evaporator, means for passing a gasfirst inheat exchange contact with saidevaporator and then' in heat exchange contact with said condenser, means for reversing the cycle of refrigerant flow whereby the evaporator becomes the.

condenser and'thecondenser the evaporator of therefrigeration system, and means for reversing the flow of gas in heat exchange: contact with said evaporator and condenser. L

2'. A reversible cycljegas devaporrzing systemcomprlsingan evaporator and a condenser, a refrigerant gas compresser and means for passing refrigerant first to the, condenser andthen to the evaporator, means for passing 7*, gas to be devaporized first inheatexchange contact with said evaporator to be cooled and deposit liquified vapors thereon and then in heat exchange contact with saidcon-' denser for reheating the cooled devaporized-gas, means for reversing the flow of refrigerant in the refrigerant cycle whereby the condenser becomes the evaporator and the evaporator the condenser,,means for reversing flow of gas to be devaporized for continued heat exchange contact first with the evaporator and then with the condenser and means for removing liquified vapors deposited on said evaporator in both directions of gas flow.

- 3. A reversible thermodynamic cycle apparatus comprising two independent heat exchangers, a refrigerant compressor adapted to compress refrigerant gas and means to pass compressed refrigerant gas first to one heat exchanger as a condenser and then to the other as an evaporator, a rnultiway valve comprising means to reverse the fiow of refrigerant from said compressor where by the function of the heat exchangers is reversed and the evaporator then functions as a condenser and the condenser than functions as an evaporator, means to pass a gas in heat exchange relationship to both of said heat exchangers in series first to the cold heat exchanger comprising the evaporator to become cooled and then to the warm heat exchanger comprising the condenser to become reheated, and means coupled with said refrigerant flow reversing means for reversing the flow of gas in heat exchange contact with said heat exchangers.

4. Apparatus as defined in claim 3 wherein the means to pass gas over said heat exchangers in series is a fan having a reversible motor adapted to rotate said fan in reverse with the reversal of said refrigerant cycle.

5. Apparatus as defined in claim 3 wherein the means to pass gas over said heat exchangers in series is a fan having a reversible motor, and means for varying the speed of said motor in both directions of rotation.

6. Apparatus as defined in claim 3 wherein the means to pass gas over said heat exchangers in series is a fan having a reversible motor, and means for varying the speed of said fan between an approximately fixed high speed and an approximately fixed lower speed in both directions of rotation.

7. Apparatus as defined in claim 3 wherein the means to pass gas over said heat exchangers in series is a fan having a reversible motor, and means for varying the speed of said motor in both directions of rotation, said means for varying the speed of rotation being responsive to the sensible temperature of the influent gas passed in contact with said heat exchangers.

8. A reversible thermodynamic cycle apparatus comprising two independent heat exchangers, arefrigerant compressor, means to pass compressed refrigerant in sequence first to one heat exchanger as a condenser and then to the other as an evaporator, and means to reverse the sequence of flow of refrigerant from said compressor to said heat exchangers whereby the function of each heat exchanger is reversed and the evaporator upon flow reversal then functions as a condenser and the condenser then functions as an evaporator, a motor driven fan mounted in said apparatus to pass a gas in heat exchange relationship to both of said heatex changers in series first to the cold heat exchanger functioning as an evaporator whereby the gas becomes cooled and then to the warm heat exchanger functioning as a condenser whereby the cooled gas is reheated, means coupled with said refrigerant'flow reversing means for reversing the fan motor and thereby the direction of flow of gas in heat exchange contact with said heat exchangers, and a timer in circuit with said reversible motor and refrigerant flow reversing means for periodically effecting reversal of both. i

-9. A reversible thermodynamic cycle apparatus comprising two independent heat exchangers, a refrigerant compressor, means to pass compressed refrigerant from said compressor in series first to one heat exchanger as a condenser and then to the other as an evaporator,.' and a" 4-way valve mounted to reverse the sequence of flow of refrigerant from said compressorto both ofsaid heat exchangers whereby the function-of each heat exchanger is reversed and the evaporator upon flow reversal then functions as a condenser and the condenser then functions as an evaporator, said heat exchangers being mounted within a gas conveying-duct, an electric motor driven fan-- in said duct to pass a gas in heat exchange relationship tov both of said heat exchangers in series first to the coldv heat exchanger functioning as an evaporator whereby the gas becomes cooled and then to. the warm heat exchanger functioning as a condenser whereby the cooled gas is re-- heated, a solenoid mounted to actuate said 4-way valve to eifect refrigerant flow reversal, means for reversing the direction of drive of said fan motor whereby the direction of flow of gas in heat exchange contact with said heat exchangers is reversed, electric circuit means coupling said 4-way valve actuating solenoid and said fan motor in both directions of rotation having means for reversing the direction of rotation of said fan motor, and a timer in said circuit adapted to periodically effect reversalv simultaneously of said fan motor and the 4-way valve 11. In an improved thermodynamic cycle the steps comprising compressing a refrigerant gas, serially condensing said refrigerant gas in a heat exchanger whereby heat is evolved and then evaporating the condensed gas in a second heat exchanger whereby heat is absorbed to produce cooling, passing an extraneous gas serially first in heat exchange contact with the gas being evaporated to cool the extraneous gas and then in contact with the first heat exchanger to reheat the extraneous gas, periodically reversing the cycle of refrigerant flow to pass compressed gas to the heat exchanger that was the cold evaporator to condense the refrigerant therein and to evolve heat, passing the condensed refrigerant then to the heat exchanger that was the condenser to evaporate the same absorbing heat and producing cooling, and simultaneously reversing the flow of extraneous gas over said heat exchangers in series with the reversal of refrigerant flow therein.

12. The method of devaporizing a gas comprising passing the gas in heat exchange contact with the cold evaporator of a compressor-expander refrigeration system to cool said gas and deposit liquified vapor on said evaporator and thereby effect devaporizing of said gas, then serially passing the cold devaporized gas in heat exchange contact with the hot condenser of said compressor-expander system, whereby the devaporized gas is reheated, reversing the cycle of said compressor-expander refrigeration system whereby the condenser becomes the evaporator and the evaporator the condenser and simultaneously reversing the flow of gas to be devaporized in heat exchange contact with said refrigerant system, Whereby the gas to be dehurnidified continues to pass serially in heat exchange contact with an evaporator and condenser of said system, and removing liquified vapors dc duction of heat exchange of the gas to be devaporized in contact with the evaporator element by solid phase liquid formation.

16. The method as defined in claim 11 wherein the volume of gas passed in contact with the evaporator and condenser elements is varied with the ambient temperature of the gas.

17. The method of reducing the dew point of a gas below 32 F. by refrigeration dehumidification comprising passing the gas in contact with the evaporator coil of a compressor-expander refrigeration system while maintaining the temperature of said evaporator coil at a temperature below 32 F., and then reheating the dehumidified gas by passing the same in contact with the condenser coil of said refrigeration system while removing condensed liquid phase moisture deposited upon said cold evaporator coil, whereby solid phase moisture tends to form upon said cold evaporator coils and reduce heat exchange with the gas being cooled thereover, periodically reversing the cycle of refrigerant flow between the condenser and the evaporator coils to make the condenser the evaporator and the evaporator the condenser, and simultaneously reversing the How of air to be dehumidifiedwhcreby cooling for dehumidification of said air is effected upon an ice free evaporator coil while the ice deposited upon the condenser coil, which was formerly the evaporator coil before reversal, becomes melted by the heat produced in said coil upon reversal.

18. The method as defined in claim 17 wherein the gas to be dehumidified is passed over said coils at a rate variable with its sensible heat content.

19. The method as defined in claim 12 wherein the extraneous gas is passed in heat exchange with the gas being evaporated at a rate variable with its ambient temperature.

20. A reversing thermo-dynamic system comprising a refrigeration system. including two heat exchangers adapted to act alternately as a condenser and an evaporator in serial flow of refrigerant therethrough and a reversing means in the refrigerant cycle to reverse the sequence of flow of refrigerant through said heat exchangers, means for passing a gas serially in heat exchange contact with both of said heat exchangers reversible to pass said gas in serial contact with said heat exchangers in either sequence, and timing means interconnected with both refrigerant and gas flow means to periodically and simultaneously reverse the direction of flow of both refrigerant and gas flows.

References Cited in the file of this patent UNITED STATES PATENTS 2,037,857 Fox Apr. 21, 1936 2,124,981 Krackowizer July 26, 1938 2,296,530 McGrath Sept. 22, 1942 2,438,120 Freygang Mar. 23, 1948 2,481,348 Ringquist Sept. 6, 1949 2,525,560 Pabst Oct. 10, 1950 2,549,547 Trask Apr. 17, 1951 FOREIGN PATENTS 53,017 Sweden Nov. 8, 1922