US2380386A - Air conditioning system - Google Patents

Description

y 1945,- R. B. P. CRAWFORD AIR CONDITIONING SYSTEM Original Filed March 13, 1939 INVENTOR. 'Ro'laanfiff CraLwforL BY J A Patented July 31, 1945 Robert B. 1 Crawford, Washington, D. C.

Original application March 13, 1939, Serial No. 261,487. Divided and this application May,9, 1942, Serial No. 442,320

11 Claims.

This invention relates to an air conditioning system and while the invention is particularly adaptable in connection with ra'ilway'car air conditioning, its principles are broadly applicable to air conditioning systems for all types of structures. v

The invention is concerned primarily with producing cooling and dehumidifying and particularly, with maintaining air in a. space at desirable conditions of humidity by means of expanding form of air conditioning system embodying my invention.

Figure 2 is a diagrammatic illustration of the control arrangements applying to the air conditioning system of Fig. 1.

Figure 3 is a cross-sectional view taken along the line 3--3 of Figure 2.

compressed airand separating the moisture v therefrom. In railway car air conditioningmompressed air from the train line may conveniently be used for the purpose, the compressed air being expanded through a turbine and then having'part 'of its moisture separated out in a separating chamber. Fresh air may be entrained with the air as it is expanded. Also, the invention contemplates that the power produced by the turbine be utilized to drive auxiliary equipment forming a part of the system. The invention also comprehends providing mechanical refrigeration means for performing sensible cooling of the air, the mechanical refrigerating apparatus beingso controlled as to do only sensible cooling with the humidity being maintained at the proper level by controlling the amount of air being expanded through the turbine.

In accordance with the foregoing general precepts of my invention, its primary object is to provide an air conditioning system wherein humidity in a space is maintained by supplying relatively dry air which has been expanded through a turbine and passed through a moisture separating chamber and maintaining the tem perature by effecting sensible cooling of the space air by means of mechanical refrigerating equipment.

Another object of the invention is to maintain temperature and humidity in a, space by passing controlled volumes of air through a turbine to be expanded therein, separa'tingmoisture from the expanded air and maintaining the temperaportion of a railway car illustrating a preferred The present application is a division ofmy earlier filed application, SeriaLNo. 261,487, filed March 13, 1939, Patent No. 2,304,151, issued December 8, 1942.

Referring to the drawing, an air conditioning system is shown in Figure 1 which, as shown, may be located in the end portion of a railway car.

In this figure, compressedairfrom the train line or other suitable source flows through a pipe i0 to a turbine II located beneath the car, the air driving the turbine and expanding therein and being delivered to an eliminator or separator chamber I2 provided with a series of eliminating plates I3 for removing moisture from the air,

, The inlet of the chamber I! through which the expanded air is delivered is provided with a suitable fresh air inlet opening I4 which is so formed that the air discharged from the turbine II will entrain fresh air which will flow through the opening I4 and mix with the expanded air from the turbine II.

Prior to passing to the turbine H, the compressed air in the line I0 is suitably cooled by passing through a spray from a series of spray nozzles I6, that portion of the pipe I0 located below the spray I6 being provided with a series of fins ll spaced closely enough together so that water flowing thereover will be held thereon by capillary action between the fins, thus increasing the cooling effectof the water. The water to the spray I6 is delivered from a. suitable storage tank I8 to which water is delivered from any suitable source and one. railroad train the water leaving wash basins, water fountains, etc., may be delivered to this tank l8 so that this water is put to a useful purpose. .The compressed airwhich has now been reduced in temperature bythe spray I6 flows to the turbine ll under the control of a valve 20 operated by a proportioning motor 2| which is controlled in a manner to be later described. In order to utilize the energy given up by the compressedair in expanding in the turbine s II, the condenser 28 consisting of finned tubes and the pipe 2| having separate nozzles so that the condensate is separated over the rlnned tubes. The air leaving the turbine II, which on expending to atmospheric pressure has its temperature greatly reduced to a value belowits 'dew-' point, will produce av flne log ormist in the chamber I! when mixed with humid air entering at H. and this air which is mixed with the fresh unconditioned air has this moisture removed by means of the eliminator plates I I and the combination of the expanded air having a low dewpoint with the fresh unconditioned air will produce a mixture of air having a low relative humidity.- This air passesthrough a passage-way, 21 within the rear compartment which. leadsto an outlet opening 28 communicating with another passageway 29 which may be located within the root or the car and extending longitudinally thercoi'and provided with suitable downwardly to'tbe compressor and motor 40 and when-the switch arms 68 and 81 are in engagement with 1 directed openings ill by means of which theair passes to the passenger space of the car. Return air is circulated through a path including the passenger spree, rear compartment and chamber 2| of said carand mixed in the chamber 29 with the fresh conditioned air by means of a fan 3| a rise in suction pressure to a predetermined value the bellows 55 will expand and move the arm 81 back into engagement with the contact ll. The arms I53 and 51 are normally biased in a clockwise direction by coil springs as shown.

Th battery as is provided for supplying power their respective contacts, power is supplied to the motor 40 as follows: from one side at battery 28 through conductors II and ti, arm 88, contact 52, conductor armjl, contact 58, conductorv 15, motor and conductors I and I! back to the other side oi th'e battery 28. Accordingly,- it will be seenthat the compressor is placed in, over,

.-ation whenevcrfthe suction pressure is above a predetermined .value and the bead pressure is bea low a predetermined value. But should the head pressure becomehigh enough or the suction pressure become low enough the circuit .to the compressor motor will be. interrupted and-the comlocated within a chamber 32 which has outlets I3 air outlet 2! so that the air will be properly mixed with the fresh conditioned air. The chamber 82 has inlets 33 and "a which may be located. in

, the rear compartment oi." the carvand the vestibule respectively and dampers 35 suitably interconnected by adjusting mechanism 36 are pro-1 vided for regulating the flow 01' air through these i -and 84 located above and below the conditioned adjusted and are so arranged-that both dampers will be simultaneously opened'or closed.

Located within the chamber 82 i a cooling coil 38 which is provided ior removing sensible heat only from the recirculated-air and this cooling coil iorms the evaporator. 01' a mechanical refrigerating'system which includes a compressor 39. driven by a motor i l. The high pressure side oi the compressor'coin'municates by means or. a pipe compressed air to pressor will stop operating. The suction pressure controller will be set at such a value as, io'r'exainpie, so lbs. to lbs.', that during normal operation of the system the temperature of evaporator" willnot become low enough to cause condensation of moisture thereon as it is intended that the evaporator eiiect only sensible cooling 0! the air,

but will be between 55 1". and It, for example. 1

.The condenser "is preierably'so located the spray'ifi wilialso cool the condenser in the sameway as it does the'pipe' it which carries vice ll.

- ualswitches may be provided if desired for interrupting operation or the'ian SI and the compresscdmotor 40 whenever desired. a I

.The now oi refrigerant through the cooling 0011,38 is controlled by an expansion valve 11,

ll with condenser 25 which in turn communicates by means or pipe 42 withfithe inlet oithe evaporator ll. The outletiot the evaporator com municates with the inlet or the compressorby this expansion valve being a thermostatic type having suitable means for varying the s'uperheat setting thereof. The construction or thls'expa'nsion valve forms no part of the presentinvention means of the pipe- 49. The operation of'the ccmpressor as illustrated is controlled by {a device responsive to the pressure .onthje high pressure i side of the system and a device responsive to the I pressure on the lcwpressure oi -the; s'ystem. For this W; a. bellows-t ,il isaconnected by means oi'a pi e on with one pipe connected to the high pressure side or the compressor, and the bellows ll controls the Position bran II which cooperates with a fixed electrical contact P i'i jected to a pressure corresponding to the temperbut'maybeconstructed as illustrated in Patent No. 2,019,724, issued November 5, 1935.10 C. A.

Otto. Such an expansion valve comprises. an operating-diaphram or bellows iorming a pair 01' chamb'era'one or which is connected to a bulb I! y means-oi a capillary ll, this-bulb being "provided with a suitable volatile iill and being positioned in contact with the outlet oi the evapit. The arrangement is; such that as the head pressure on the compressor rises to a suincientiy high value the bellows ll'willexpand and move the arm I! out of engagement with the contact I:

and upon a drop in thehead'pres sureto apr n termined value, the bellows will contact-and'the arm II will move back into. 1 contact. It. A second bellows II -is such that upon adrop in suction'pressure'to a predetermin d v ue. the "or the beitiled electrical contact Illiei. u

orator so that one oi the chambers will be sub- .ature or the refrigerant leaving the evaporator;

(The details or the 'expansionlvalve mechanism may. bemore fully understood by inspecting Elgure 2.) The. other or the said chambers is subiccted-to' the pressure of the refrigerant in the evaporator so that the operating diaphragm or ,bcllows moves in accordancewith variationsin "the superheat oi the refrigerant at the outlet of evaporator. v o by memo! a spring ll (see Ike hrs 2) The. valve: is biased towards and the tension oi'the spring may be adiust'edb'y means of a propcrtionina motor ll so that the valve is adjusted to maintain varying degrees oi super-heat which has-the cases I m. v

the turbine or espansion dethe battery 91.

ing the effective cooling surface of the evaporator. The adjustment of this spring by the motor 8| is controlled by a thermostat 82, which thermostat is shown as comprising a bulb 83 located in the return air inlet duct 34a, this bulb being connected by means of a capillary tube 84 with the bellows 85 which controls the position of a slider arm 86 with respect to a potentiometer resistance 81. (Figure 2.) As the temperature of the air in the car or the air entering the inlet 34a increases, the bellows 85 will expand and move the arm 86 to the right with respect to the lished between the evaporator coil and the member 9| which will energize a relay 92. This relay comprises a winding 93, and an armature 94 connected to a switch blade 95 which cooperates with fixed electrical contacts 96 and 91, the armature moving the blade 95 so that it engages contact 96 when the relay is energized and so that-it engages the contact 91 when the relay is deenergized. A battery 91' may be provided to supply power to the relay 92 or any other suitable sources of power may be employed. As soon as condensation forms on the evaporator and a circuit between the evaporator coil 38 and the member 9| is completed by the moisture thereon,

relay winding 93 will be energized as follows: from the battery 9'! through conductor 98, evaporator coil 38, member 9|, conductor 99, winding 93, and conductor I08 back to the other side of Energization of the relay causes arm 95 to move into engagement with contact 96 as described above.

The member 9| may be compos'edpf a sheet of perforated material wound around .the pipe and clamped together by means of a clamping screw as shown in Figure 3. The spacer members 9|] are separated as shown in Figure 3 to permit an upward flow between the evaporator coil and the member 9| so that evaporation of moisture which condenses on the evaporator coil may be rapidly effected, the perforations in the member 9| permitting that portion of the evaporator coil surrounded thereby to be contacted by the air passing through the chamber 32. Y

When the relay 92 is energized by reason of I condensation of moisture on the evaporator indicating that the evaporator is removing latenttion pressure on the compressor will rapidly decrease so that the compressor will shut down. Until the temperature in the evaporator rises suff ciently so that the, moisture on the evaporator 76 coil has been evaporated, the expansion valve will remain closed so that there will be no further cooling thereby. As' soon as the moisture on the evaporator coil has evaporated however, the circuit to the relay 92 will be interrupted and the arm 95 will move into-engagement with the contact 91. The center terminal of the motor 8| will nOw be connected to the control arm 86 of the temperature responsive device 82 as follows: from the center terminal of the motor through conductor I05, arm 95, contact 91, and conductor I08 to the arm 86. The right hand end of the resistance 81 is connected by means of the conductor I09 to the right hand terminal of the motor 8| and the other end of the resistance 81 is connected by means of conductors H6 and H11 to the left hand terminal of the motor 8|. It will accordingly be apparent that the motor 8| will operate in accordance with the temperature at the bulb 83 and as the temperature increases the motor will operate to adjust the setting on the spring 89 so that the expansion valve will maintain the refrigerant at the evaporator outlet at a lower degree of superheat so that agreater portion of the evaporator coil will be effective and more cooling will be pro duced thereby. Conversely, upon a decrease in temperature of the air entering the inlet 34a the spring of the expansion valve will be adjusted so that a higher degree of superheat of the refrigerant at the evaporator outlet will be maintained and a smaller area of the coil will be effective for cooling purposes and the temperature of the air passing thereover will be reduced to a lesser extent. It will be apparent that when the relay 92 is energized by reason of condensation on the evaporator, the movement of arm 95 out of engagement with contact 91 interrupts the circuit to the control arm 86 so that the thermostat has no control whatever over the position of the expansion valve.

For controlling the operation of the valve 28 which regulates the flow of compressed air from the pipe l0 through the turbine is a humidity responsive device .I H? which responds to the humidity of the air passing from the rear compart ment of the car through the return air inlet opening 34a. The humidity responsive device comprises a humidity responsive element 6 which, controls the position of a slider arm II! with respect to a potentiometer resistance 8, the slider and resistance cooperating to control the motor 2| which positions the valve 20. Upon an increase in humidity of the air in the space being conditioned, or of the air passing through the return air inlet 34a, the slider arm ||1 will move to the right over the resistance H8 and cause the motor 2| to move the valve 28 towards open position by an amount which is proportional to the increase in humidity. As the amount of compressed air to the turbine H is increased, there will be a greater amount of cooled air with a low dew-point admitted to the chamber' l2 and accordingly mixed with the cooled return air from the chamber 32 which will have the effect of reducing the relative humidity in the space being conditioned. This humidity responsive device may operate to move the valve from a fully closed positionto a fully 01 "ned position as the humidity in the space increases from 45% to 55% ior example.

It will now be understood that accordingto the invention, the humidity in the space is controlled by controlling the supply of compressed air to the turbine and as the humidity increases, the valve 28 moves from closed to open position.

The sensible cooling of the air in the conditioned space'is effected mainly by the evaporator coil 38 of the refrigeration system which reduces the temperature of the recirculated air but which is controlled so that it does not effect any latent cooling of the airin the conditioned space so that the load on the refrigeration system is kept at a minimum. In order to secure this result the compressor is operated to maintain the suction pressure between values of 50 pounds to 65 pounds, for example, assuming a refrigerant such as Freon or F12 is utilized which will maintain the coil temperature between values such as 55 F. and 70 F'., and by maintaining the suction pressure between these limits, under normal circum stances no moisture will condense on the evaporator coils. Should there be such condensation of moisture, however, indicatin that the refrigcrating system is effecting some latent cooling, the device 9! operates to energize the relay 92 which closes the expansion valve. Normally, however, the expansion valve is controlled in accordance with the temperature in the condensed space and this valve is adjusted to maintain a maximum superheat when the temperature in the space is 75, for example, and to reduce the superheat as the temperature increases so that at 80, for example, the amount of superheat will be at a minimum. Accordingly, substantially all of the sensible cooling of the air is effected by the refrigeration system at high efficiency and the latent cooling is effected by the compressed air of the expansion system, and the energy given up by the compressed air inthe expanding thereof is utilized for driviri 'g the generator 22 to charge the battery 23 which furnishes energy for the compressor drivingg motor and the fan motor. This may be augmented by another source of power if necessary. J

While a preferred form of the air conditioning system embodying my invention has been illustrated, particularly in connection with railway cars and the. like, it should be understood that the system disclosed is applicable in general to air conditioning systems for all types of structures.

Having described a preferred form or my invention, it should be understood that various modifications may become apparent to those skilled in the art and such modifications will fall within the realm and scope of the invention. The invention is to be limited therefore, only in accordance with the scope of the claims appended hereto.

I claim as my invention:

1. In an air conditioning system for a railway mechanical refrigeration system having an evaporator for cooling such air and control means therefor operative to maintain said evaporator at a temperature sufficientl high normally to pre- I vent removal of water from the air cooled by the evaporator, said dehumidified air and said cooled air being mixed before being used.

3. In an air conditioning system, in. combination, means for dehumidifying a first supply of air comprising means supplying compressed air,

' means cooling and expanding said first supply of air, means for cooling, without dehumidification, a second supply of air comprising a mechanical refrigeration system including an evaporator for cooling said second supply of air and control means for normally maintaining the evaporator temperature sufflciently high to prevent dehumidification of said second supply of air, and means for mixing said first and second supplies of air and delivering such mixture to a desired point of use.

4. In an air conditioning system, in combination, means for dehumidifying a first supply of air comprising means supplying compressed air, means cooling and expanding said first supply of air, means for cooling, substantially without dehumidification, a second supply of air comprising a mechanical refrigeration system including an evaporator for cooling said second supply of air, control means for normally maintaining the evaporator temperature sufiiciently high to prevent dehumidification of said second supply of air and means responsive to the actual production of condensate by said evaporator for permitting said evaporator temperature to increase, and means for mixing said first and second supplies of air and delivering such mixture to a desired point of use.

5. In a system for cooling air, in combination, a mechanical refrigeration system including an evaporator over which the air is passed for cooling the air, and means responsive to the actual car, means utilizing compressed air from the train line for causing a flow of fresh air into the car, means for expanding the compressed air to remove latent heat therefrom, means for causing sensible cooling of the air in the car, aid means including an evaporator of a mechanical refrigeration system over which the air is circulated, the condenser of the refrigeration system being provided with a plurality of closely spaced fins, means for supplying waste water from the raily car to said fins to increase the cooling capacity thereof, and means utilizing the same Waste water for cooling the compressed air before it is delivered to the expanding means.

2. In an air conditioning system for a space, in combination, means to supply dehumidified air to said space including means supplying compressed air, means cooling and expanding such air, and

means for supplyi cooled air to said space without removing moisture from such air including a 76 collection of moisture on said evaporator for permitting the temperature of said evaporator to rise until such, moisture has been evaporated.

6. In a system for cooling air, in combination, a mechanical refrigeration system including an evaporator over which the air is passed for cooling the air, 'means responsive to a condition of the refrigerant in the system operative normally to prevent the temperature of said evaporator from falling below a value at which moisture is removed from the air passing over the evaporator, and additional means responsive to the actual collection of moisture on said evaporator for permitting the temperature of the evaporator to rise until such moisture has been removed.

7. A method of conditioning the air in a space which comprises cooling compressed air, expanding the cooled compressed air, removing moisture from the expanded air, entraining fresh air with the expanded air and delivering the mixture to the space, recirculating air through a path including the space, cooling the recirculated air in a portion of said path by,removing sensible heat from the air without removing latent heat therefrom, controlling the sensible cooling of the recirculated air in response to the temperature of the air in a portion of said path, and controlling the amount of compressed air which is expanded and delivered to the space in response to the humidity of the air in a portion of said path.

' 8. In an air conditioning system for a space, a source of compressed air, an expanding means, means for directing said compressed air to said may be expanded and cooled, means for cooling the compressed air passing to the expanding expanding means wherein the compressed air may be expanded and cooled, means for cooling the compressed air passing to the expanding means, means for removing moisture from the expanded air, means for entraining fresh unconditioned air with the air leaving said expanding means and delivering the mixture of fresh and cooled air to the space, means for recirculating air through a path including the space, a sensible coolin means, means for directing said recirculating air over said sensible cooling means, means responsive to the temperature of the air in a portion of said path controlling said sensible cooling. means, and

, means, means for removing moisture from the exmeans responsive to the humidity of the air in a portion of said path controlling the flow of air to the expanding means.

9. In an air conditioning system for a space, a source of compressed air, an expanding means, means for directing said compressed air to said expanding means wherein the compressed air may be expanded and cooled, means for cooling the compressed air passing to the expanding means,

means for removing moisture from the expanded air, means for entraining fresh unconditioned air with the air leaving said expanding means and delivering the mixture of fresh and cooled air to the space, means for recirculating air through a path including said space, a sensible cooling means, means for directing said recirculating air over said sensible cooling means, said sensible cooling means comprising an evaporator of a direct expansion refrigerating system, means responsive to the temperature of the air in a por- Y tion of said path for controlling the flow of refrigerant through said evaporator, and means responsive to the humidity of the air in a portion of the path for controlling the flow of air to the expanding means.

10. In an air conditioning system for a space, a source of compressed air, an expanding means, means for directing said compressed air to said expanding means wherein the compressed air panded air, means for entraining fresh unconditioned air with the air leaving said means and delivering the mixture of fresh and cooled air to the space, means for recirculating air through a path including said space, a sensible cooling means, means for directing said recirculating air over said sensible cooling means, said sensible cooling means comprising an evaporator Of a direct expansion refrigerating system,

means responsive to the humidity of the air in a I portion of said path for controlling the flow of air to the expanding means, and means responsive to the condensation of moisture on said evaporator coil for interrupting the flow of refri erant therethrough.

11. In an air conditioning system for a railway car space, means utilizing compressed air from the train line for causing a flow of fresh air into the space, means for expanding the compressed air to remove latent heat therefrom, means for circulating other air in-a flow path including said space, means for causing sensible cooling of said other air, said means including an evaporator of a mechanical refrigerating system over which said other air is circulated, the condenser of the refrigerating system being provided with a plurality of closely spaced fins, means for supplying waste water from the railway car to said fins to increase thecooling capacity therefor, said waste water also being used to cool said compressed air before the same is expanded, means responsive to the humidity of the air in a portion of said flow path for controlling the supply of compressed air to the expanding means, and means responsive to the temperature of the air in a portion of said flow path in control of the flow of refrigerant 40 through said evaporator.

expanding 1

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