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Publication numberUS2481348 A
Publication typeGrant
Publication dateSep 6, 1949
Filing dateAug 21, 1946
Priority dateAug 21, 1946
Publication numberUS 2481348 A, US 2481348A, US-A-2481348, US2481348 A, US2481348A
InventorsRobert G Miner, Clarence L Ringquist
Original AssigneeTrane Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Air-conditioning apparatus with defrosting means
US 2481348 A
Abstract  available in
Images(2)
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Claims  available in
Description  (OCR text may contain errors)

P 1949- c. L. RINGQUIST ETAL AIR CONDITIONING APPARATUS WITH DEF'ROSTING MEANS Filed Aug. 21, 1946 2 Sheets-Sheet 1 bniom 526m JNVENTORS C.L.Rmsquls'r & ROBERT G.MINEP.

HTTORfiYS I Patented Sept. 5, 1949 UNITED STATES PATENT OFFICE AIR-CONDITIONING APPARATUS WITH DEFROSTING MEANS Clarence L. Ringqulst and Robert G. Miner, La

Crosse, La Crosse, Wis.

Win, assignors to The Trane Company,

Application August 2t, 1946, Serial No. 691,952

3 Cla,

apparatus. 5

It is well known that where air or gas must be dehumidified to a condition at or below the frost point, a duplication of equipment is required so that the air or gas can be delivered on a continustages for conditioning air or gas, whereby the air or gas may be economically dehumifled and reheated in a comparatively small space.

Another object of this invention is to provide an apparatus which will condition air or gas by dehumidiiying it and subsequently reheating it so that the conditioned air or gas will have a continuous uniform moisture content and dry bulb temperature.

Still another object of the present invention is to provide a means of control whereby the conditioned air or gas will be uniform as to moisture content and dry bulb temperature.

With the foregoing and other advantages in view, this invention consists in the apparatus and system hereinafter described and claimed and fiustrated 1n the accompanying drawings where- Fig. 1 is a diagrammatic view of a. preferred and practical embodiment of the new and improved air or as conditioning system, and

Fig. 2 is a simplified diagrammatic view of the cycles of operation of the new and improved air or gas conditioning system.

ous basis without shutting down the equipment It is to be understood that these drawings are for removal of ice or frost accumulations. The illustrative of the present invention, and are not present invention pets a considerable saving to be considered as limitations thereof, since variin refrigeration since the total amount of refrlgous changes and modifications may be made witheration is available for the purpose of conditionout departing from the spirit of the invention or ing this air or gas, and at the same time the nethe scope of the appended claims. cessity oi duplicating certain of the equipment Referring to the drawings in which th am is eliminated. reference numerals have been used to indicate One object of the present invention, then, is to the Same, like P d fi st ad t n t i provide an apparatus for conditioning air or gas, Fig. 1, the reference numeral it indicates genparticularly when the air or gas must be coner -11y an inlet duct or pipe through which air or ditionecl to a temperature at or below the frost s i moved by he fan i through either the duct point, it or it, then through the duct space 20, and Another object of this invention is to provide then through either duct it or it to the outlet an apparatus which will allow air or gas that has duct 22. The system may be arranged in either been conditioned below the frost point to be de- 5 horizontal or vertical position as desired. livered on a continuous basis without the neces- As a typical illustration to aid in the undersity of using more than one system or apparatus standing of the operation of this new and novel for this purpose. apparatus, assume the following conditions:

Still another object of the present invention is Gas at 70 F. saturated is to b condit d to provide an apparatus which will deliver on a 30 to F. saturated when leaving coil as in duct continuous basis, in one direction, air or gas that it or when leaving coil 26 in duct it. This 70 has been conditioned below the frost point withg s enters the pparatus through the inlet duct out the necessity of shutting down the apparatus it into the duct l6the duct it being closed by for defrosting. the damper 24- The gas then passes over the Another object of the present invention is to 35 c il 6. def osting that coil, provided a previous provide an apparatus for conditioning air or gas cycle has occurred. The gas then passes out of which may use warm, unconditioned air or gas h t and into he duct pace ZIP-the to defrost the cooling coils in this apparatus. amp r 2 ei 11 an open position. The Yet another object or the present invention is damper 30 meanwhile is in closed position, thus to provide a sequence of cooling and reheating 4Q forcin h as o pass over the coil 32 where it is reduced to 57.5 F. saturated. The gas then flows into the duct l6the damper 34 being in open position. The gas then passes over coil 36 and is reduced to 25 F. saturated. The gas then leaves the duct I 6 through the open damper 36 and into outlet duct 22. In this illustration the purpose of reducing the gas temperature to 25 F. saturated was the elimination of moisture. It is to be understood, of course, that other temperatures and conditions may be used with equally good results. Any sensible heat pickup after reducing the gas 25 F. saturated is a. gain. Therefore; the gas may now travel through the heating coil, which has been designated by the reference numeral 40, and which is interposed in the outlet duct 22. C011 46 is connected by pipe circuits 42 and 44 to cooling coil 32 to form a heat reclamation cycle. A pump 46 is interposed in the pipe circuits 42 and 44 to circulate the heat exchange medium from cooling coil 32 to heating coil 46 and back again.

The heating coil 40 restores to the gas, as sensible heat, both the latent and sensible heat which the cooling coil 32 abstracted. Thus the gas has been dehumidifled to the equivalent of 25 F. saturated, but leaves the apparatus with part of the sensible heat restored, which had to be removed for dehumidiflcation. Conversely, this heat reclamation causes the heat exchange medium to be reduced in temperature by the passage of 25 F. gas over the heating coil 46. The heat exchange medium, thus reduced in temperature, is returned to the cooling coil 32 at a lower temperature than at which it left the same coil, thus causing a direct saving in the amount of refrigeration required to reduce the gas temperature to 25 F. The coil 40 might be omitted entirely, and it need only be used when it is desired to raise the outlet temperature of gas emitting either from the coils 26 or 36. If desired, the coil 32 may also be omitted from the apparatus. In this illustration given above, the gas now leaves the apparatus through the outlet duct 22 at a dew point temperature of 25 F., but a dry bulb temperature of 60 F.

As in all refrigeration dehumidifying apparatus where it is necessary to use a cooling medium at or below the frost point, ice or frost will form on the coil or other apparatus used for heat transfer purposes. In the illustration given above ice has gradually accumulated on the coil 36 until its effectiveness as a transfer medium is about to be impaired. The defrosting of the coil 36 and the simultaneous transfer of the function of dehumidifying and cooling from the coil 36 to the coil 26 may be accomplished as follows:

The cooling coils 26 and 36 are supplied with a cold heat exchange medium, for. example, brine from a refrigeration unit 48 through a pipe circuit 56 having a circulating pump 52 therein to circulate the heat exchange medium. The brine circuit is formed by the supply pipe 56 from the refrigeration unit 48 to the valves 54 and 56, which selectively allow the flow of cooling medium either to the cooling coil 26 or the cooling coil 36. A pump 52 is interposed in the return conduit 66 to pull the cooling medium from the coils back to the refrigerating unit 46. The valves 54 and 56 are connected to and rendered operative by the valves 62 and 64, respectively, these latter valves 62 and 64 being connected to a pneumatic temperature controller 93 by line 69. The temperature controller 93 is connected to a power supply 68, either air (as shown) or electric or other suitable power means, and is responsive to a thermally sensitive element, generally designated by the reference numeral 92 to regulate the amount of flow of the brine.

If desired, a precooling unit I06 may be interposed in the inlet air duct I2. This precooling unit I60 may use cold water or any other suitable cooling medium. This precooling coil I then operates to cool the warm, unconditioned air or gas entering the apparatus thus removing a portion of the moisture from the air or gas in liq-,

uid. form. The removal of this moisture lengthens the time that it takes for the cooling coils 26 and 36 to frostup. The cooling coils 26 and 36 are thus kept operating for longer periods of time without the necessity of changing the air flow the apparatus operates more efllciently when a portion of the moisture is removed by said precooling, for the emciency of the cooling coils is impaired by the deposition of frost on the coils, and the longer this can be prevented the more efficient the apparatus. As an alternative method of construction, if desired, the cooling coil which has been designated by the reference numeral 32 may be moved from its position between the cooling coils 26 and 36 as is shown most clearly in l, and positioned in the air or gas inlet I2 to occupy the position of the precooling coil I60 as shown in Fig. 1. If the coil 32 is positioned in the air or gas inlet I2, then the warm entering air or gas may be cooled and a portion of the moisture may be removed from said air or gas as liquid. Removal of any moisture from the incoming air or gas lengthens the time that it takes for the cooling coils 26 and 36 to frost up. It has also been found that positioning the coil 32 in the air inlet I2 rather than between the coils 26 and 36, as shown in Fig. 1, results in a higher exit temperature of the air from the outlet 22 since the reheating coil 40, which is connected to the coil 32 by suitable conduits which contain heat exchange medium, operates at a higher temperature since the heat exchange medium in these conduits is not cooled as much as when the cooling coil 32 is positioned between the cooling coils 26 and 36. When the coil 32 is positioned in the air inlet I2, or when a precooling coil I00 is used in the air inlet I2, the incoming air or gas is cooled so that it takes somewhat longer to defrost the coils 26 or 36 when they have become frosted up than when the warm entering air or gas is allovged to flow directly over the frosted coils 26 or 3 In the sequence of operations described above the cold heat exchange medium is only supplied to coil 36, the flow of this medium being shut off to coil 26 by valve 54. As accumulations of ice and frost on the coil 36 develop, it is necessary to shift to cooling coil 26 if the efficiency of the apparatus is to be maintained. This shift is accomplished as is shown most clearly in Fig. 2. The arrows indicate the direction of gas flow. In Fig. 2 the top drawing labeled Cycle A shows the flow of gas as described in the illustration just given. In this cycle the gas enters the inlet duct I4 and flows into the duct I6, since the damper 24 is in a closed position and shuts off the duct I8. The gas then flows through coil 26, defrosting said coil, and thenenters the duct 20 through the open damper 28 and passes through the coil 32 and out into duct I8 through open damper 34. Here the gas flows through cooling coil 36, which is operating, and then out through the outlet duct 22 and through the reheating coil 46. The second drawing of Fig. 2, which is labeled Cycle A to B, shows a transition period between the shift from operating cooling coil 36 to operating cooling coil 26. As the cooling coil 36 begins to-lose efiiciency due to accumulations of ice and frost, the damper 24 is shifted by means of driving motor 60 actuated by valve I6, so that duct I6 is shut off. Simultaneously driving motor I4 actuated by valve I8 closes the dampers 34 and 28, to which it is connected by means of a suitable linkage designated generally by the reference numeral 84, and valve 54 opens to admit refrigerant flow to coil 26 to precool this coil. The gas entering through inlet duct I2 now passes into duct I6, and then passes directly through cooling coil 36 and out the outlet duct 22 and through reto defrost the coil. It has also been found that heating coil 40. During this cycle, which continues only for a relatively short period of time, coil 36 is operating, and coil 26 has refrigerant flowing therethrough and is therefore being precooled.

The third drawing of Fig. 2, labeled "Cycle B shows subsequent operation; Valve 80 actuates driving motor 82, which opens dampers l2 and tsaid dampers being connected to the driving motor 32 by means of a suitable linkage 85. At the same time the valve 83 actuates driving motor d to shift the damper 3d so as to close duct id. Gas entering the duct i2 now passes into duct iii and over coil it, defrosting said coil. The gas then passes through the open damper t0 and over coil 32, then through open damper l2, over cooling coil 2t, then passes out the outlet duct 22, and through reheat coil t. In this cycle, coil lit is being defrosted, and coil 2B is cooling the as.

The last drawing of Figure 2, which has been labeled Cycle B to A shows the transition as the cooling coil 2% loses efldciency due to accumulations of ice and frost. Driving motor 60 is actuated by valve to, and shifts damper 2t to close on duct it, and at the same time valve 80 actuates driving motor 02 to close dampers i2 and t0 and valve to opens to admit refrigerant to coil 3% to precool this coil. The gas entering through inlet duct it now passes through duct it and directly through coil 2t, and then out the outlet cycle coil it is operating, and coil as has refrigerant flowing therethrough and is therefore being precooled. Like cycle A to B this cycle. is of relatively short duration, after which the operations are repeated-the drawing labeled .Cycle A showing the positions of the dampers and the flow of gas just described. These cycles, above described, may be repeated as often as desired with either manual control or an automatic device, such as a cycle timer, or other suitable automatic apparatus, to make entirely automatic the functioning of the apparatus. While we have shown our apparatus with numerous motors and controls, it is to be understood that the apparatus may be greatly simplified, for example, a single motor with suitable linkage and earns may be used to operate the dampers 2t, 3t, 30, 28, I2, and 33.

It is apparent from the above description that the method of operation used in the present invention is a continuously operating system for the delivery of gas or air at dew points as low as the frost point, or lower, without the necessity of shutting down the apparatus for defrosting or deicing. It will also be readily apparent that the present invention does away with the necessity of duplicating apparatus.

In order to demonstrate further advantages of the apparatus of the present invention described herein, reference may be made to a technical problem of cooling 10,000 C. F. M. of free air or gas, which on entering the apparatus at 70 F. saturated, leaves at a final condition of 60 F. dry bulb and F. dew point. The conditioning of the air or gas, as set forth in the above example, might be obtained by the use of a single cooling coil such as the cooling coil 26 or at, and then reheated, but a refrigeration requirement of 90 tons would be necessary. However, by the use of the new and improved apparatus of the present invention, utilizing the here in described method of dehumidifying and reheating, it is possible to reduce the refrigeration all) i 6 load from 90 tons to 56 tons, and at the same time deliver this gas or air at the same dew point.

A thermally sensitive element 92 is responsive to the temperature of the outgoing air in the outlet 22 and is connected to pneumatic temperature controller 93 to control the operation of valves 5t and 56 and to regulate the amount of refrigerant which is supplied to these cooling coils. In this manner the temperature and/or the humidity of the outgoing air may be accurately controlled.

The thermally sensitive element 92 and pneumatic temperature controller 90 by proper controls and apparatus, may also be used to selectively direct the flow of cooling medium either to the cooling coil 26 or the cooling coil 36 and may also be used to control the operation of the driving motors 60, it, 82 and 90, which in turn control the operation of the dampers 2t, 3t and 20, i2 and 30, and 38, respectively so as to direct the flow of air initially either through the duct It or the duct It as previously described.

The cycle would be changed in the following manner. Assume that the system is operating on cycle A as shown in Fig. 1. As coil 36 becomes frosted the temperature in duct 22 tends to rise, but element 92 and temperature controller 93 cause the valve 56 to increase the flow of brine to maintain the control temperature. However, a point is reached when the maximum possible flow of brine is going through the coil, and because of the frost on the coil the temperature in duct 22 continues to rise. Element 02 and temperature controller 93 respond to this abnormal temperature rise and the temperature controller 93 sends out a pressure above normal control pressure. This abnormal pressure, byproper controls such as a program device, is then used to actuate the valves 62, 6t, l0, i8, 80, and 88 in the proper sequence to produce changes in the cycle as described above. Such controls are well known in the art and it is not considered necessary to show them in detail.

If it is desiredto control the operation of the said valves, motors and dampers responsive to an interval of time, then a device (not shown) designed to operate a valve upon the lapse of a predetermined interval of time may be used either in conjunction with or substituted for the pneumatic temperature controller or, an instrument (not shown) responsive to the accumulation of frost 'on the cooling coils 2t and 36 may be either used in conjunction with or substituted for the thermostat 92.

Although the term air has been used in the specification and the claims, it is to be understood that we are using the word air in its generic sense to mean atmospheric air or any other gas, for the apparatus of this invention is suitable for heating any type of air or gas and we do not wish to limit our applications to atmospheric air alone. It is also to be understood that the illustrations and examples given have been by way of illustration and not limitation since various changes and modifications may be made.

ducts first as desired, and means to supply refrigerant to whichever of said coils is last in the path of said air, and to cut oil the supply of refrigerant to the coil first in the path of said air, both of said last two means being responsive to conditions indicating that one of the coils in the ducts has becomefrosted.

2. In an air conditioning apparatus comprising a casing with air inlet and outlet and two ducts, means to move air through said casing and through a first coil positioned in one of said ducts and then through a second coil positioned in the other of said ducts, means to selectively send the air through one or the other of said ducts first as desired, and means to supply refrigerant to whichever of said coils is last in the path of said air "and to cut of! the supply of refrigerant to the coil first in the path of the air.

3. In an air conditioning apparatus comprising a casing with air inlet and outlet and two ducts, means to move air through said casing and through a first coil positioned in one of said ducts, and then through a second coil positioned in the duct space between the said two ducts and then through a third coil positioned in the other of said ducts, means to selectively send the air through one or the other of said ducts first as desired, and means to supply refrigerant to whichever of said coils is last in the path of said air and to cut off the supply of refrigerant to the coil first in the path of the air.

4. In an air conditioning apparatus comprising a casing with air inlet and outlet and two ducts, means to move air through said casing and through a first coil positioned in one of said ducts, then through a second coil positioned in the duct space between the said two ducts and then through a third coil positioned in the other of said ducts, means to selectively send air through one or the other of said ducts first as desired, and means to alternately supply refrigerants to one and then the other of the said first and third cooling coils in said ducts, and a reheating coil positioned in the path of air emitting from said outlet and operatively connected by conduits containing heat exchange medium with the aforesaid second cooling coil.

5. In an air conditioning apparatus comprising a casing with an air inlet and outlet and two ducts, means to move air through said casing and through a first cooling coil positioned in one of said ducts and then throu'gh a second cooling coil positioned in the other of said ducts, means to selectively send air through one or the other of said ducts first as desired, means to alternately supply refrigerant to first one and then the other of said cooling coils, both of said last two means being responsive to conditions indicating that one of said coils has become frosted.

6. An apparatus of the type described comprising a casing with air inlet and outlet and two ducts, a cooling coil positioned in one of said ducts, a second cooling coil positioned in the other of said ducts, means to move air through said casing and alternately through either of said ducts and cooling coils first as desired, and means to alternately supply refrigerant to first one and then the other of said cooling coils, both of said last two means being responsive to conditions indicating that one of said cooling coils has become frosted.

7. An apparatus of the type described comprising a casing with air inlet and outlet and two ducts, a cooling coll positioned in one of said ducts. a second cooling coil positioned in the other 8 of said ducts, means to move air through said casing and alternately through either of said ducts and cooling coils first as desired, and means to alternately supply refrigerant to first one and then the other of said cooling coils, a third cooling coil positioned in the space between said ducts and operatively connected by ducts containing heat exchange medium with a reheating coil positioned in the path of air emitting from said outlet.

8. An apparatus of the type described comprising a casing with air inlet and outlet and two ducts, a cooling coil positioned in said inlet to pre-cool air fiowing through the apparatus, means to move air through said casing and through a second cooling coil positioned in one of said ducts and then through a third cooling coil positioned in the other of said ducts, means to selectively send the air through one or the other of said ducts first as desired, and means to supply refrigerant to whichever cooling coil is last in the path of said air and to cut oil. the supply of refrigerant to the cooling coil in the other duct,

9. An apparatus of the type described comprising a casing with air inlet and outlet and two ducts, a cooling coil positioned in said inlet to pre-cool air flowing through the apparatus, means to move air through said casing and through a second cooling coil positioned in one of said ducts and then through a third cooling coil positioned in the other of said ducts, means to selectively send the air through one or the other of said ducts first as desired, and means to supply refrigerant to Whichever cooling coil is last in the path of said'air, and to cut off the supply of refrigerant to the cooling coil in the other duct, both of said last two means being responsive to conditions indicating that one of the cooling coils in the ducts has become frosted.

10. In an air conditioning apparatus comprising an air inlet and outlet and two ducts, a cooling coil positioned in said air inlet, and a reheating coil positioned in said air outlet and connected to said cooling coil in said inlet by conduits containin heat exchange medium, means to move air through said air inlet and cooling coil and then successively through a second cooling coil positioned in one of said ducts and then through a third cooling coil positioned in the other of said ducts and then through said reheating coil and out the said air outlet, and means to selectively send the air through one or the other of said ducts first as desired, and means to supply refrigerant to whichever cooling coil is last in the path of said air and to cut off the supply of refrigerant to the cooling coil in the other duct.

11. In an air conditioning apparatus comprising an air inlet and outlet and two ducts, a cooling coil positioned in said air inlet and a reheating coil positioned in said air outlet and connected to said cooling coil in said inlet by conduits containing heat exchange medium, means to move air through said air inlet and cooling coil and then successively through a second cooling coil positioned in one of said ducts and then through a third cooling coil positioned in the other of said ducts and then through said reheating coil and out the said air outlet, and means to selectively send the air through one or the other of said ducts first as desired, and means to supply refrigerant to whichever cooling coil is last in the path of said air and to cut of! the supply of refrigerant to the coolin coil in the other duct, both of said last two :4 be responsive to conditions indicating that one of the cooling coils in the ducts has become frosted.

it. A fluid conditioning apparatus comprising a w having an inlet duct, an outlet duct, and two branch ducts connecting said inlet duct and said outlet duct, a heat exchanger in each of said branch ducts, means for moving fluid from said inlet duct to said outlet duct, movable means in said casing for directing said fluid from said inlet duct to said outlet duct first through one of said heat exchangers and then through the other of said heat exchangers, means for moving said movable means to direct said fluid from said inlet duct first through said other of said heat exchangers and then through said one of said heat exchangers, and means to supply refrigerant to whichever of said heat exchangers is last in the path of said fluid.

it. A fluid conditioning apparatus comprising inlet duct and an outlet duct, 'a first duct ooecting said inlet duct and said outlet duct,

9. second duct connecting said inlet duct and said outlet duct, a first heat exchanger in said recting said fluid from said inlet duct to said 1' outlet duct first through said first coil and then through said second coil, and means for moving said valve means to direct said fluid from said inlet duct to said outlet duct first through-said second coiland then through said first coll.

CLARENCE L. RINGQUIST. ROBERT G. MINER.

REFERENCES CITED The following references are of record in the file of this patent:

mm STATES PATENTS Number N i r 2,185,047 Weinstein Dec. 26, 1939 1 2,200,118 Miller May 7, 1940 2,445,705 Weinstein July 20, 1948

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2185047 *Jun 5, 1939Dec 26, 1939Trane CoApparatus for air conditioning
US2200118 *Oct 15, 1936May 7, 1940Honeywell Regulator CoAir conditioning system
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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2693939 *May 6, 1949Nov 9, 1954Edward E BrattonHeating and cooling system
US2763132 *Aug 31, 1953Sep 18, 1956Lawrence S JueDehumidifying apparatus
US2884764 *Nov 25, 1955May 5, 1959Desomatic Products IncReversible cycle system
US2939295 *Dec 29, 1958Jun 7, 1960American Air Filter CoAir conditioning apparatus
US3058317 *Mar 31, 1958Oct 16, 1962Superior Air Products CoVaporization of liquefied gases
US3151469 *Oct 2, 1961Oct 6, 1964Lester K QuickHeat reclaiming system
US3209553 *Jun 4, 1964Oct 5, 1965Yoshitoshi SohdaDefrosting device in a refrigerator
US3572052 *May 15, 1969Mar 23, 1971Streater Ind IncDucted refrigeration unit
US3732703 *Jun 28, 1971May 15, 1973Rinipa AbAir conditioning plant for buildings
US4566531 *Oct 5, 1983Jan 28, 1986Daimler-Benz AktiengesellschaftVehicle air conditioning arrangement
US5237831 *Sep 27, 1991Aug 24, 1993EolasAir conditioning apparatus
US5369961 *Oct 23, 1992Dec 6, 1994Seiler; WolframApparatus for the defrosting of refrigerating driers below 0 degrees celsius
US5890368 *May 13, 1997Apr 6, 1999Lakdawala; NessDehumidifier
US6021644 *Aug 18, 1998Feb 8, 2000Ares; RolandFrosting heat-pump dehumidifier with improved defrost
US9200829 *Sep 24, 2013Dec 1, 2015Walter StarkLow temperature cooling and dehumidification device with reversing airflow defrost for applications where cooling coil inlet air is above freezing
US20070214810 *Mar 30, 2005Sep 20, 2007Tomohiro YabuHumidity Control System
US20150082824 *Sep 24, 2013Mar 26, 2015Walter StarkLow temperature cooling and dehumidification device with reversing airflow defrost for applications where cooling coil inlet air is above freezing
WO2010131257A3 *Mar 15, 2010Mar 17, 2011Surendra Himatlal ShahEnergy efficient frost free sub-zero air conditioner
Classifications
U.S. Classification62/151, 62/160, 62/325, 62/278
International ClassificationF24F5/00, F25D21/12
Cooperative ClassificationF25D21/125, F24F5/0007, F25B2347/021
European ClassificationF24F5/00C, F25D21/12B