US2243478A - Air conditioning apparatus and method - Google Patents

Description

May 27, 1941. M. F. KNoY 2,243,478

AIR CONDITIONING APPARATUS AND METHOD A TTOR/VE Y6.

May 27, 1941. M. F. KNOY AIR CONDITIONING APPARATUS AND METHOD 2 Sheets-Sheet 2 Filed Dec. 6, 1957 A TToRA/E Ks.

Patented May 27, 1941 2,243,478 AIR CONDITIONING APPARATUS AND METHOD Marion F. Knoy, Long Beach, Calif.

Application December 6, 1937, Serial No. 178,435

4 Claims.

My invention relates to air conditioning apparatus, more particularly such apparatus utilizing changes in the state of a circulating uid heattransfer medium, and is directed to an improved form of such apparatus effective for temperature and humidity control at all seasons of the year.

In air conditioning apparatus of the type involved here, a suitable uid in a flow circuit is alternately vaporized and condensed to serve, in eiect, as a pump for transferring heat from one zone to another. One of the objects of my invention is to provide a reversible heat-transfer cycle whereby the fluid may be either vaporized or condensed at a selected point in the circuit.

The outdoor atmosphere constitutes a huge reservoir into which considerable quantities of heat may be discharged, or from which considerable quantities of heat may be withdrawn, without appreciable effect on its temperature as a whole. An object of my invention is to provide a reversible means whereby at one season of the year heat may be transferred from an indoor body of air to this outdoor reservoir, and, at another season of the year, transferred from the outdoor reservoir to the indoor body of air. In this latter function of transferring heat to an interior body of air, it is my further purpose to generate heat mechanically by electrically actuated means at consider-` ably less expense and with considerably vgreater eiliciency than is possible by the usual procedure of passing an electric current through a resistor.

Broadly described, one aspect of my invention comprises the combination of a heat exchanger exposed to outdoor air, a heat exchanger exposed to indoor air, means providing a fluid course' through the two heat exchangers for a suitable with the fluid course for subjecting said medium to pressure, and means to reverse the direction of fluid through the uid course.

One object of my invention is to arrange such a combination so that when the circulation is in one direction, one of the heat'exchangers will be suitably supplied with the liquid medium to serve as an evaporator, the second heat exchanger being suitably drained of liquid medium to serve heat-transfer medium, a compressor connected.

dispersed secondary heat exchangers exposed to indoor bodies of air at the various stations, ,with the system arranged for supplying each heat exchanger with liquid when the heat exchanger functions as an evaporator and for draining the heat exchanger when it functions as a condenser.

In another form of my invention, it is my purpose to provide a self-contained unit of a port able character having one of its heat exchangers adapted for exposure to outdoor air and the other of its heat exchangers adapted for exposure to indoor air.

- In the preferred form of my apparatus, I have the further object of providing a novel form of :temperature control achieved by making the compressor responsive to the pressure in one side of the heat-transfer circuit.'

In mild climates, myair conditioning apparatus by virtue of its reversible circulation alone will meet all seasonal requirements for temperature -control of an indoor body of air. In more extreme climates where the outdoor temperature falls substantially below 40 F., circulation reversal ofthe heat-transfer mediumy may notal ways sufllce to heat the indoor body of air to a comfortable temperature. With such exigency in mind, I may combine a combustion means withy at least a part of the uid course whereby the heat-transfer medium may serve as a means for conveying heat derived from fuel. 4

An important feature of the preferred forms of my invention is the provision of means such as a -spray arrangement for wetting the exterior surface of one or more of the heat exchangers in the system. Among my objects of such provision are: To facilitate transfer of heat between the heat exchanger andthe surrounding air; to wash the air; to control the humidity of the air; and to prevent frost formation on a heat exchanger functioning as an evaporator. An important advantage of such an arrangement is that the humidifying euect achieved may be regulated by varying the concentration of a solute in the spray liquid. y

The forms of my invention herein described are characterized by the conception of interrelating the spray means associated with one heat exchanger with the spray means associated with a second heat exchanger in such a manner that accumulation ofwater by condensation on the cooler side of the circuit may compensate in part for water lost on the warmer side of the circuit.

Other objects and advantages of my invention will be apparent in the following detailed description considered with the accompanying drawings.

In the drawings:

Fig. 1 is a vertical cross-sectional view largely diagrammatic` of my invention embodied in an air conditioning unit of a portable or semi-port able type.

Fig. 2 represents a flow chart for the circulation of the heat-transfer medium when the apparatus is functioning to cool the ,indoor air.

Fig. 3 is a similar ow chart indicating the movement `of the heat-transfer medium in the course of heating the indoor air by mechanical action.

Fig. 4 is a similar chart indicating the circulation of the medium when an auxiliary burner is in operation for heating by fuel consumption in extremely cold weather.

Fig. 5 is a diagrammatic view similar to Fig. 1 showing the principles of my invention incorporated in a multiple-unit apparatus for affecting l indoor air at a plurality of points.

Fig, 6 shows schematically an arrangement for simultaneous control of a plurality of .valves in one of my systems.

Fig. '1 is a sectional view indicating one modification of my invention.

Fig. 1 shows a room having a :door I8 and an exterior wall I I. An air conditioning unit, enclosed by a suitable casing I2, includes a duct I3 for circulating a stream of outdoor air through the unit, 'the duct comprising an intake portion I4 extending through the wall I I, and a discharge portion I5 likewise extending through the wall II. It will be obvious to those skilled in the art that operating conditions may be satisfied by merely extending duct portions I4 and I5 through 'a window or transom. In the interior of the unit the duct I3 is enlarged to provide a suitable chamber I8 for housing a heat exchanger I9, A vertical set of louvres 28 are provided on the downstream side of the heat exchanger compartment I8 and inclined for drainage towards the interior of the compartment, the bottom 2| of the compartment being formed as a pan to receive such drainage.

Blower means, such as a fan 22 driven by an individual motor 23, is provided for forcing cirlso culation of outdoor air through the duct I3. The

air conditioning unit also incorporates a duct 26 for indoor air, including an intake portion 21,

a discharge portion 28, and an intermediate chamber 29 for a second heat exchanger 38.

Preferably, as previously described, the second chamber will also be provided with a set 0f louvres 3l and will have its bottom 32 formed as a pan. A blower for forcing a stream of indoor air through the duct 26 may comprise a fan 33 driven by an individual motor 34. Since the two ducts I3 and 26 will ordinarily diner considerably in temperature, an intervening partition 4| of heat insulating material is desirable.

The outdoor heat exchanger I9 may be of a well known construction, comprisingv an upper `header 42 communicating with a pipe 43 and a lower header 44 communicating with a pipe 45, the ltwo headers being interconnected by suitable tubes 46 having ns 41. A separator 48 is associated with the pipe 43 adjacent the upper header 42 for the purpose of entraining any liquid that may tend to flow out of the header into. the pipe, the liquid draining towards the lower header 44 through'a suitable drain pipe 49 The heat exchanger A3l) for the indoor air is of similar construction, comprising an upper header 58 communicating with a. pipe 5I and a lower header 52 communicating with a pipe 53, the two headers being interconnected by a plurality of tubes 54 having fins 55. This second heat exchanger is likewise provided with a separator 56 associated with the upper header 58, the separator having a drain pipe 51 leading to the lower header 52.

A motor 39 actuates a compressor 58 for the heat-transfer medium, the operative intercomnections including a sheave 59 on the motor shaft 48, a sheave 6I) on a compressor shaft 6I, and a belt 62 interconnecting the two sheaves.

From the discharge side of the compressor 58 a pipe 63 controlled by a valve 64 communicates with the previously mentioned pipe 43 associated with the upper heat exchanger I9, and a second pipe 65 controlled by a valve 66 communicates with the pipe 5I associated with the lower heat exchanger 38. Insimilar manner, from the intake side of the compressor 58 a pipe 61 controlled by a valve communicates with the pipe 43 associated with the upper heat exchanger,

and a second pipe 69 controlled by a valve 10 communicates with the pipe 5I associated with the lower heat exchanger 38. It will be apparent that in such an arrangement the valves may be manipulated to cause the compressor to pump the heat-transfer medium -from either heat exchanger to the other.

'I'he closed circuit for the heat-transfer medium is completed by a fluid receiver or reservoir 1I with which pipes 45 and 53 communicate, the pipes having valves 12 and 13 respectively ad,- jacent the reservoir. Extending downward. into the liquid body within the reservoir 1I is a discharge pipe 14, the lower 'end of which has a valve 15 controlled by a iioar, 16 The upper end ofthe discharge pipe 14 has two branches, one branch 11 controlled by a valve 18 leading to the pipe 45 above the valve 12 and the other branch 19 controlled by a valve 88 leading to the pipe 53 above the valve 13.

In installations where an auxiliary combustion means may be desirable, I incorporate in my apparatus a boiler 8l, preferably associated with the reservoir 1 I. As shown in the drawings, the boiler may have an upper pipe 82 connected with the reservoirv 1I, and a second pipe 83 disposed to drain from the bottom of the reservoir. From the top of the boiler a pipe 84 controlled by a valve 85 communica-tes with pipe 5I associated with the lower heat' exchanger 38. A suit.. able burner 86 having a fuel pipe 81 is shown positioned at the lower end of the boiler.

Since heat is generated both by the motor 39 and the compressor 58, both may be enclosed by an inner casing 88 adapted to be vented to one or both of the air ducts. Thus, an intake vent pipe 89 controlled by a buttery valve 90 extends from the intake portion I4 of the duct I3 to the inner casing 88, the intake end of the vent pipe being directed upstream, as shown, and a discharge vent pipe 9| 'controlled by a butterfly valve 92 extends from the inner casing 88 to the discharge portion I5 of the air duct I3, the discharge end of the vent pipe being directed downstream, as shown. In similar manner an intake vent pipe 93 controlled by a buttery valve 94 and a discharge vent pipe 95 controlled by a butterfly valvel 96 interconnect the inner casing 88 and the duct 26 By manipulation of-the various butterfly valves, the inner casing 88 may be vented to the outdoor air when the unit is operating to cool the indoor air, and the casingmay be vented to the indoor air during the seasons when the apparatus is employed to heat the indoor air. r

For the heat-transfer medium, any of the well known refrigerants may be provided, such as ethyl chloride, methyl chloride, ammonia, the uid known to the trade as Freon, and the like. A suicient quantity of the heat-transfer fluid is introduced into the system to fill to the desired point whichever heat exchanger is functioning as an evaporator, sufticient liquid being retained automatically in the reservoir 1| to seal the lower end of the pipe 14. The heat-transfer medium in liquid state drains into the reservoir 1| from the heat exchanger that lfunctions as a condenser, and as the liquid inthe reservoir tends to rise above a level governed by the adjustment of the float 16, the liquid is released through the pipe 14 to flow into the heat exchanger that is functioning as an evaporator.

When it is desired to have the air conditioning apparatus operate to cool the indoor air, the various valves are adjusted to provide the closed circuit indicated diagrammatically by full lines in Fig. 2. In this circuit the heat-transfer medium in gaseous state is put under pressure by the compressor 58 and transmitted through the pipe 63, the valve 64, and the pipe 43 to the heat exchanger I9 associated with the stream of outdoor air. The temperature of the medium is lowered in the heat exchanger I9 and the resulting condensate drains through thepipe 45 and the valve 12 into the reservoir 1|.- From the reservoir 1| liquid under pressure is released through the pipe 14 to pass through the pipe 19, the valve 80, and the p ipe 53 into the lower header 52 of the heat exchanger 30, in which heat exchanger the liquid evaporates and takes up heat from the surrounding air stream. From the heat exchanger 30, the vaporized medium returns to the intake side of the compressor through the pipes and 69. It is apparent that in this mode of operation, the apparatus, in effect, pumps heat from the stream of indoor air in the duct 26 to the stream of outdoor air in the duct I3.

When it is desired to raise the temperature of the indoor body of air with respect to the outdoor atmosphere, the various valves are adjusted to provide a closed circuit in the reverse direction, as indicated diagrammatically by the full lines in Fig. 3. The heat-transfer medium in gaseous state is compressed by the compressor 58 and delivered to the heat exchanger 30 through the pipe` 65, the valve 66, and the pipe 5|. Within the heat exchanger 30 the medium changes to the liquid state giving up its latent heat of vaporization to the surrounding air stream. The liquid drains from the lower header 52 of the heat exchanger through the pipe 53 and the valve 13 to the reservoir 1 I, and from the reservoir flows upward to the heat exchanger I9 through the pipe 14, the pipe 11, the valve 18, and the pipe l5. Within the upper heat exchanger I9 to the liquefied heat-transfer medium is vaporized, taking its heat of vaporization from the surrounding air stream. The cycle is completed by the vaporized medium passing to the intake side of the comv apparatus will transfer a total of between 10,000

and 15,000 B. t. u., which is three or four times the amount of heat produced by passing the saine current through a resistance element.

When, in cold weather, the difference between the outdoor 'temperature and the indoor temperature is too large for satisfactory heating by the cycle indicated by Fig. 3, all the motors except the motor 34 driving the fan 33 are shut down, the various valves of the system are manipulated to provide the cycle shown in Fig. 4, and

the burner 86 under the boiler 8| is ignited. The heat-transfer medium warmed and vaporized in the boiler 8| will pass upwardly through the pipes 84 and 5| to the heat exchanger 30, where the cooling effect of the driven air stream from 'the room will cause the vaporized medium to liquefy, the latentr heat of vaporization being transferred to the room atmosphere. The liqueed medium is drained from the heat exchanger 30 through the pipe 53 and the valve 13 to the receiver 1 I, where it is permitted to return to the boiler through the lower pipe 83 or the upper pipe 82.

One of the features of my invention is the provision of means for wetting the surfaces of at least one of the heat exchangers in the system. Preferably such an arrangement will be extended to all of the heat exchangers involved. In Fig. 1 the reservoir means, generally designated by the numeral 99 is enclosed by a relatively heavy casing |00 of heat-insulating material. One tank for supplying both of the heat exchangers may be employed, but I prefer, for reasons that will become apparent, to provide'two separate tanks, one tank IOI for liquid to spray the heat exchanger I9, and a second tank |02 for liquid to spray the heat exchanger 30. The advantage of employing one reservoir for both heat exchangers is that increments' of liquid condensed at one heat exchanger returning to the common reservoir will offset, at least in part, decrements of liquid lost by vaporization-at the other heat exchanger. 'I'he advantage of employing two separate tanks is that a desirable temperature difference between the liquids employed for the two heat exchangers may be maintained.

I achieve the advantages of both these alternatives by employing two separate tanks, but spacing the tanks apart, interposing a heat insulating wall |03, and connecting the tanks by a pipe |04 of small diameter extending through the wall. By virtue of this 4arrangement liquid may be readily equalized between the two tanks with minimum transference of heat. To insure an adequate quantity of liquid for the spray system,

one of the tanks, for example, tank |02, may be provided with a water ysupply pipe |05 controlled by a suitable 'iioat valve |06; and to keep the spray system from/being flooded, a suitable overflow pipe |01 may extend into one of the tanks.

Liquid passes from the bottom of the tank |0I through a pipe |08 to a pump |09 from which nozzle |||,`the spray nozzle being directed toward the heat exchanger I9 on the upstream side thereof in the air 'duct-I3. Liquid gathering in the pan 2| below the heat exchanger I9 drains back into the tank |0I through a suitable drain pipe ||2. In like manner, liquid from the tank |02 passes through a pipe ||8 to a pump III and then through a pipe ||5 to a nozzle ||6 directed against the heat exchanger 30, and the liquid from the pan 82, below the heat exchanger it is delivered through a pipe I|0 to a spray returns to the tank |02 through a suitable pipe ||1.

The two pumps |09 and ||4 have a common shaft I8 driven bythe motor 39 through the medium of sheaves ||9 and a belt |20.

Fig. indicates how the principles of my invention may be embodied in a multiple-unit system in which a central exchanger |23 associated with the outdoor air is balanced with a plurality of dispersed secondary heat exchangers such as typified by secondary heat exchangers |24 and |25 associated with indoor air.

The central air conditioning unit of the system is housed in a suitable casing |26 providing an air duct |21 for the circulation of outdoor air, the air being driven by a suitable fan |29 that is operatively connected with a motor |29 by means including a belt |30. 'I'he air duct |21 is shaped to provide a suitable drainage pan |3| for spray liquid, and is provided with a setof louvres |32 disposed to drain liquid into the pan. A pipe |33 communicates with the upper header |34 of the heat exchanger |23, and a. second pipe |35 is connected with the lower header |36 of the yheat exchanger, the usual separator |31 being assopiated with the pipe |33 to drain to the lower header through a pipe |39.

The pipe |35 connects with a pipe |39 above a valve |40, the pipe |39 at its lower end draining into a receiver or reservoir |4| for the heattransfer medium employed in the system. The upper end of the pipe |39 connects with a. tank |42 that may be employed to control the liquid level in the heat exchanger |23 when that heat exchanger is functioning as an evaporator. Within the tank |42 the upper end of an intake pipe |43 is controlled by a float valve |44. The pipe |43 terminates at its lower end in the receiver |4| near the bottom thereof, and is con trolled by a suitable valv |45.

The secondary heat exchanger |24 is part of a secondary air conditioning unit housed in a casing |46, the casing being provided with an air duct |41 through which indoor air is propelled by a fan |49. The fan |48 is driven by a motor |49 through means including a belt |50. The air duct |41 is formed with a drainage pan |5| below the heat exchanger |24 and i's provided with sets of louvres |52.

The upper header |53 of the heat exchanger |24 communicates with a pipe |54 and the usual separator |55, the separator draining to the lower header |56 through a suitable pipe |51. The lower header |56 has a pipe |59 that connects with a second pipe |59 above a valve |90. The upper end of the pipe |59 is connected with the bottom of a tank |6| that may be employed to control the liquid level in the heat exchanger |24. 'I'he lower end of the pipe |59 connects with a pipe |62 that connects in turn with the previously 4mentioned pipe |39 to provide flow back to the receiver |4|. Within the tank |6| an intake pipe |63 is controlled by a iloat valve |64. Below the tank |6| the intake pipe |63 is controlled by a valve |65 and connects with a pipe |66 that connects in turn with the pipe |43 below the valve |45.

The second auxiliary air conditioning unit in the system incorporating the heat exchanger |25 is similar in construction to the unit just described. 'I'he second auxiliary unit is housed by a casing |61 that provides an air duct |69 through which indoor air ls driven by a fan |69. 'I'he fan |69 is driven by a motor |10 through means including a belt |1|. The air duct provides a drainage pan |12 and the usual set of louvres |13. A pipe |14 connects with the upper header |15 of the heat exchanger, and the usual separator |16 associated with the pipe |14 drains to the lower header |11 of the louvres through a suitable pipe |18. The lower header |11 of the heat exchanger has a pipe |19 that connects with a second pipe |90 above a valve |9|, the pipe |90 in turn connecting with the aforementioned pipe |62 that leads to the receiver |4|. The upper end of the pipe |90 connects with a tank |92 having an intake pipe |83 controlled by a oat valve |94. The intake pipe |93 has a valve below the tank |82, and leads to the previously mentioned pipe |66.

It is to be understood that, by preference, the central unit of the system incorporating the heat exchanger |23 will be located at a much lower level than the auxiliary air conditioning umts incorporating the heat exchangers |24 and |25, so that drainage from the auxiliary units to the central unit will simplified. For example, the

central air conditioning unit may be below thev first floor level of abuilding. In any installa.- tion where the central unit must be higher than the auxiliary unit, it will be within the skill of an ordinary mechanic to provide pumps or other means for the required circulation of the heattransfer medium.

'Ihe compressor |31 for the heat-transfer medium is driven by the motor |29 through means including a belt |88. The discharge pipe |99 of the compressor has two branches, one branch controlled by a valve |9I, and a second branch |92 connecting with the pipes |54 and |14 that lead to the upper headers, respectively, of the heat exchangers |24 and |25. To cut off rlow through the branch |92, a valve |93 is provided in the pipe |54, and a valve |94 in the pipe |14. The branch pipe |90 is connected with the pipe |33 through a short pipe |95, there being a valve |91 in the pipe |33 near the point of connection.

'I'he intake pipe |99 ofthe compressor likewise has two branches, one branch |99, controlled by a valve 200, connecting with the pipe |95, the other branch 20| communicating with two pipes 202 and 203. The' pipe 202 controlled by a valve 204 connects with the pipe |54 on the side of the valve |93 towards the heat exchanger |24, and the pipe 203, controlled by a valve 205, connects with the pipe |14 on the side of the valve |94 towards the heat exchanger |25.

In the central air conditioning unit, aboiler 206 having a burner 201 is connected with the -receiver |4| through an upper pipe 208 and a.

lower pipe 209, the lower pipe connecting with the bottom of the receiver. The pipe 2|0 from the top of the boiler 206 has a valve |96 andconnects with the pipe |95. The fuel pipe 2| to the burner 201 iscontrolled by a pressure-responsive valve 2|2 having a pipe 2|3 to transmit pressure from the boiler 206. y

When the system is employed to cool the indoor air, only the following valves are open:

valves |9|, |91, |40, |65, 204, |95, and 205. From thelcompressor |81 the vaporized heat-transfer medium flows through the pipes |89, |90, |95, and |33, to the heat exchanger |23, in which the heat-transfer`medium liquefles and then drains through pipes |35 and |39 to the receiver |4|-.

From the receiver |41, the liquefied heat-transfer medium iiows through the pipe |66 to the two secondary heat exchangers, the path to the heatA exchanger |24 being through thepipe |63, the

tank |6|, and the pipes |59 and |58, and the path to the heat exchanger |25 being through the pipe |83, the tank |82, and the pipes |80 and |19. In the two secondary heat exchangers the heat-transfer medium is vaporized in the usual manner, and the vapors are drawn back to the compressor |81, the flow from the heat exchanger |24 being through the pipes |54 and 202 to the pipe 20|, and the return ow fromv the heat exchanger |25 being through the pipes |14 and 203 to the pipe 20|.

When the system functions to transfer heat from the outdoor air to the indoor air, only the following valves are open': valves |93, |60, |94, |8I, |45, |91, and 200. From the discharge side ofthe compressor |81, the vaporized heat-transfer medium is delivered to the two secondary heat exchangers through the pipes |89,- |92, |54, and |14. In the two secondary heat exchangers the heat-transfer medium is liqueed, yielding up its latent heat of vaporization, and the liquid drains back to the receiver |4| in the central unit, the return from the heat exchanger |24 being through the pipes |58 and |59 to the pipe |62, and the return ilowfrom the heat exchanger |25 being through the pipes |19 and |80 `to the pipe |62. i

When the boiler 206 is in operation for providing heat in colder weather, only the following valves are open: valves |96, |9|, |93, |60, |94, and |8|'. The vaporized heat-transfer medium passes from the boiler 206 through the pipes 2|0, |33, |95, |90, and |92, branching to the heat exchanger |24 through the pipe |54 and to the heat exchanger |25 through the pipe |14. In the secondary heat exchangers the medium liquees, yielding its heat of vaporization, and the liquid flows back to the receiver |4|, the return ilow from the heat exchanger |24 being through the pipes |58 and |59 to the pipe |62, and the return ow from the heat exchanger |25 being through the pipes |19 and |80 to the pipe |62. From the receiver 4| the liquid returns to the boiler 206 through the pipe 209. 'I'he temperature of the boiler is maintained 'by the action of `the pressure-responsive valve 2|2.

In the multiple unit embodiment of my invention, as in the single unit embodiment previously described, I prefer to incorporate means for wetting the various heat exchangers. vThe central air conditioning unit includes a spray tank 2|5 having a supply pipe 2|6 controlled by a float valve 2|1 and a suitable overflow pipe 2|8. Liquid from the spray tank 2| 5 passes through a pipe 2|9 to a spray pump 220 from which-it is delivered through a pipe 22| to a nozzle 222 directed toward the heat exchanger |23, the pump being actuated by the motor |29 through suitable means including a belt 223. The liquid dripping from the heat exchanger |23 and the louw'es |32 collects in the pan |'3| and drains through apipe 224 back to the tank 2|5.

'Ihe liquid for spraying the heat exchanger |24 may conveniently be held in reserve in the drainage pan and, in the same manner, the liquid for spraying the heat exchanger |25 may be held by the drip pan |12. To insure an adequate supply of such liquid, a pipe 225 branches from the pipe 22| on the discharge side of the pump 220, the pipe 225 having one branch 226 extending into the pan |5| and controlled by a float valve 221 and a second branch 228 extending into the drip pan |12 and controlled by a float valve 229. To keep the two drip pans the drip pan |5| and a second overiiow pipe 23| from the drip pan |12 join at a pipe 232 that drains into the tank 2|5 in the central air conditioning unit.

In the spraying of the heat exchanger |24, liquid fmm the pan |5| passes through a pipe 233 into a pump 234 and then is delivered through a pipe 235 to aA spray nozzle 236, the pump being driven 'by the motor |49 through suitable means including a belt 231. In like manner, liquid from the drip pan |12 circulates through a pipe 238, a pump 239, and a pipe 240 to a sprayA nozzle 24|, the pump being driven lby the motor |10 through a belt 242.

Whenever the spray system gains water by condensation at the two secondary heat exchangers |24 and |25, the excess water drains back through the overflow pipes 230 and 23| to the tank 2|5 in the central unit. If the water added to the contents of the tank 2|5 over-compensates for loss of spray liquid by evaporation in the air duct |21, the excess liquid will drain away through the pipe 2|8; but if the added liquid is insufficient to offset such losses by evaporation, fresh liquid will be automatically introduced through the pipe 2|6 by automatic operation of the oat valve 2|1. On the other hand, if water is being lost from the spray system in the air ducts |41 and |68, replacement will be had automatically through the pipe 225 and its branches 226 and 226. If an insufficient quantity of moisture is condensed in the air duct |21 to compensate for ow through the pipe 225, additional water will be introduced into the system automatically through the pipe 2|6 by operation of the float valve 2|1. If the condensation in the air duct Ulmer-compensates for the fluid loss in the secondary units, the excess will flow away through the drain pipe 2|8.

The advantages of the spraying operation will be discussed first in relation to an indoor heat exchanger functioning as an evaporator to cool the air. The liquid being discharged from the spray nozzle is relatively cool because of its previous contact with the heat exchanger, and this relatively cool liquid traversing the space between the nozzle and the heat exchanger inthe form of spray droplets rapidly labsorbs heat from the air. Upon reaching the heat exchanger, the spray droplets, under the action of the relatively strong air currents, repeatedly impinge against the iin and tube surfaces of the heat exchanger. Each time a particle of liquid touches a metal surface, which metal is here of relatively low temperature, it loses heat, and each time it is swept oil the surface into the relatively warm air stream it absorbs heat. Since the solution is divided into myriad small particles having an immense aggregate surface, and since these particles alternate rapidly between the air stream and the metal surfaces before they finally reach the drip pan under the heat exchanger, the transfer of heat from the air stream to the heat exchanger is exceptionally rapid and efficient.

l The spraying operation also serves to wash the air stream by entrapping particles of dust, and I prefer additionally to achieve steriliza- -tion by adding a suitable germicidal agent to A solution y organic substances highly soluble in'or miscible with water are suitable'for my purpose. A sodium chloride, or calcium chloride brine, or some non-volatile organic solute such as glycerine v` mayV be employed. 'I'he first of these new adyantages is the prevention of frost formation A when the solution is continuously sprayed over y taking up heat when in contact with the surfaces of the heat exchanger and losing heat when being waited by the air stream from one metal surface to another. When the` apparatus is being operated on the heating cycle, the indoor sprays will, of course, wash the air as before described, and, again, a germicidal agent may be added to the liquid.

VAn important function of a brine or other chemical solution used asa spray for an indoor heat exchanger is to regulate the humidity of the indoor body of air to an effective extent. The salts mentioned and other well known compounds in aqueousvsolution will maintain a water-vapor tensionwell below that of pure water at the same temperature. If a saturated or near saturated air stream is exposed to such a solution, water vapor will be drawn from the air, there being a tendency for equalization of the two vapor tensions. On the other hand, if the air stream is extremely d ry, it will derive vapor content from the spray solution. Thus, in summer time when the heat exchanger is being employed as an evaporator to cool the air stream.. there will ordinarily be a distinct tendency for the spray solution to de-humidify the saturated air to a desirable extent. On the other hand, in winter time when the indoor heat exchanger is functioning as a condenser, the opposite tendency occurs, because in winter time the airis usually well below its dew point before vheating so that increase-in temperature makes the air extremely dry. The spray solution will not, of

course, permit the current of air to attain a relative humidity of 100% because its vapor ten- -sion is below that of ordinary water, but it willthan otherwise. The more soluble the salt or other chemical employed and the higher its ionization, the lower the vapor tension. It is apparent, then, that by controlling the concentration of the solution in thespraysystem, I maycontrol the humidity of the indoor air to a desirable extent..` y

I have previously pointed out that the provision for equalization between the body of liquid employed for a heat exchanger associated with the indoor air and thebody .of liquid employed for spraying a heat exchanger associated with the outdoor air permits water gained by condensation on one side of the spray system to be transferred to the other side of thev spray system to compensate for water loss by evaporation., It is to be noted that, in effect, I have provided means for replenishing the solution with distilled water, thereby avoiding the excessive` introduction of Cil minerals into the liquid as would result from replenishment with ordinary tap Water.

A refinement of my system consists in the introduction of a novel principle of temperature control in which the effectiveness of the compressor is arranged to be responsive to the pressure of the heat-transfer medium in the indoor heat exchanger. The effectiveness of this type of control is based on the fact that the boiling temperature of a liquid is determined by the pressure.

As an example of an arrangement for such temperature control, I show conventionally in Fig. 5 a device 243 associated with the compressor |81 for regulating the displacement per stroke of the compressor by means of clearance pockets in a manner familiar to those skilled in the art. The displacement-regulator 243 is adjustably responsiveyto pressure transmitted thereto through a pipe 244. The pipe 244 has two branches: one branch 245, having a valve 246, leads to the pipe 20| associated with the intake side of the compressor; the other branch 241, having a valve 24B, leads to the pipe |92 associated with the discharge side of the compressor. By manipulation of the valves 246 and 248, the displacementregula-tor 243 may be made responsive to the pressure in the secondary heat exchangers 24 and |25 when those heat exchangers are serving as, evaporators, as well as when those heat exchangers are serving as condensers for the heattransfer medium. When, in the course of heating the indoor air, the secondary heat exchangers a-re employed as condensers, the displacementregulator will be adjusted to respond to a drop in pressure by increasing the capacity of the compressor. On the other hand, whenthe secondary heat exchangers are employed in a cycle `regulation provides automatically for varying the load on the motor of the central unit and permits operation at maximum eiciency without the necessity of constant attention to the mechanism of the central unit. For further control of the temperature of the indoor body of air, the motors associated with the secondary unit may be controlled in` speed by manual means or by room thermostats in a well known manner. One advantage of the arrangement for temperature regulation just described is that it supplies a basis'for determining fan capacity, amount of chemical circulated, and amount of exchanger surface required to effect the desired heat exchange between the heat-transfer medium and the indoor body-of air at a given room temperature.

In each of the forms of-my invention it is necessary to manipulate several valves to reverse the cycle of the heat-transfer medium. It is contemplated that all the valves involved in .such

reverse the cycle. A construction i llz nsfi;maybeY "two pinions 252, each of which operatively engages a pair of pinions 253. Each of the pinions 253 controls one of the four dual valve stems. When the crank 25| is rotated in one direction, it closes the valves 64, 1U, 12, and 80, and opens the valves 66, 68, 13, and 1-8. Rotation of the crank in the opposite direction `has the opposite effect.

In a multiple-unit system such as shown in Fig. 5, it is advantageous to have the fans of the secondary units controlled by room thermostats. Thus, the fan motors |49 and |10 may each be controlled through wires 254 by a. room thermostatic switch 255. Preferably, a manual switch 256 will also be included in the control circuit. When, for example, the second-ary units are being heated by vapors generated in the central boiler 206, each of the fans in the secondary unit will normally be energized and devenergized automatically in accordance with temperature conditions. By opening the manual switch 256 associated with a given secondary unit, the secondary unit may be made inoperative for economy where, for example, one of the rooms of a building is not being used.

In one of the `forms of my invention I surround the receiver or reservoir for the heat-transfer medium with a relatively large body of liquid for storing heat. For example, instead of using the simple tank |4| shown in Fig. 5, I may employ a tank 251 having exterior fins 258, as shown in Fig. 7. This tank is encased by a relatively large and heavily insulated tank 259 that is substantially lled by a body of water 269. As relatively hot liquid is continuously entering the tank 251 in the normal operation of my apparatus, heat is transferred to the enveloping body of water 260 which will eventually approach the temperature of the liquid in the inner tank. An advantage of this arrangement is that after the compressor is shut down, the heat-transfer medium in the tank 251 will be kept at elevated temperature and will be caused to boil by pressure drop in the system. In this manner the system will tend to function for a substantial period after it is shut down mechanically.

The description and specific arrangements of my invention, set forth herein for the purpose of disclosure and illustration, suggest a wide range of modification and substitution Without departing from the principles of the invention. I specifically reserve the right to all such changes and substitutions that come within the scope of my appended claims.

I claim as my invention:

1. An air conditioning apparatus of the character described, including: a first heat exchanger exposed to a stream of outdoor air; a second heat exchanger exposed to a stream of indoor air; means for causing one of said heat exchangers to cool and the other to heat; a reservoir containing an aqueous solution of a non-volatile substance, the solution' having substantially lower vapor tension than pure water, said reservoir being adapted to receive solution drained from the exterior surfaces of. said rst heat exchanger; a second reservoir containing similar aqueous solution, said second reservoir being adapted to receive solution drained from the exterior surfaces of said second heat exchanger; means to spray said solution against the exterior surfaces of said first heat exchanger; means to spray said solution against the exterior surfaces of said second heat exchanger for controlling the humidity of said indoor air stream, said two reservoirs being interconnected whereby Water gained by condensation of moisture from the air at one of said heat exchangers will compensate at least in part for water lost by evaporation at 'the other heat exchanger; an inlet pipe connected with one of said reservoirs to add water thereto in further compensation for water lost from the liquid by evaporation whereby the total volume of the solution is maintained and whereby the concentration of said non-volatile material in the water is prevented from increasing; and an automatic valve controlling discharge from said inlet pipe inaccordance with the liquid level in said reservoir.

2. A reversible air conditioning system including: a first heat exchanger exposed to indoor air and adapted to function as an'evaporator for a heat-transfer medium to cool said air or alternatively to function as a condenser to heat said air; a second heat exchanger exposed to outdoor air to impart heat to said outdoor air by functioning as a condenser for said medium when said first heat exchanger is an evaporator and to derive heat from said outdoor air by functioning as an evaporator for said medium when said rst heat exchanger functions as a condenser; a reservoir containing a solution of sub-l stantially non-volatile material and water, vsaid solution having a vapor tension less than that of water alone and having a freezing point substantially less than 32 F., the surface of said rst heat exchanger draining into said reservoir; means including pressure means to spray said solution against said rst heat exchanger for controlling the humidity of said indoor air and for preventing frost formation on the heat exchanger when said rst heat exchanger functions as an evaporator; a second reservoir containing a solution of the same ingredients, the exterior surfaces of said second heat exchanger draining into said second reservoir; means including pressure means to spray said solution. against said second heat exchanger for preventing frost formation thereon ywhen the 'second heat exchanger functions as an evaporator and to evaporate water from said solution when the second heat exchanger functions as a condenser; means providing a fluid passage between said reservoirs whereby water lost from the solution at the first heat exchanger is at least partially replaced by moisture condensed from the air at the second heat exchanger, and, when the 'system is reversed, water lost from the solution at the second heat exchanger is at least partially replaced by moisture condensed at the flrst heat exchanger; and automatic means' to replenish said solution with water whenever the total volume of the solution in the two reservoirs drops to a predetermined extent.

3. In an air conditioning apparatus including a iirstheat exchanger exposed to a stream of outdoor air, a second heat exchanger exposed to a stream of indoor air, and means for causing one heat exchanger to cool and the other to heat, the ,combination therewith of: a rst body of aqueous solution of a non-volatile substance, the solution having substantially lower vapor tension than pure water; means to spray liquid from said body against the exterior surfaces of said first heat exchanger and to drain the liquid so sprayed back to said body; a second body of a like aqueous solutionymeans to spray liquid from said second .body against the exterior surfaces of said second water lost by evaporation in the other heat exchanger.

4. A method of operating an air conditioning apparatus of the character described including a first heat exchanger exposed to a stream oi' outdoor air and a second heat exchanger exposed to a stream of indoor air and wherein one heat ex- Cil changer acts as a cooler and the other acts as a heater, said method comprising: providing a rst body of an aqueous solution of non-volatile,

substance, the solution having substantially lower vapor tension than pure water; spraying liquid from said body on the exterior surfaces oi said rst heat exchanger; returning sprayed liquid drained from said first heat. exchanger to said body; providing a second body of like aqueous solution; spraying liquid from said second body on the exterior surfaces of said second heat exchanger for controlling the humidity of said indoor air stream; returning sprayed liquid drained from said second heat exchanger to said second body of liquid; and draining liquid from one of said bodies to the other of said bodies whereby water gained by condensation of moisture from the air at one of said heat exchangers will compensate at least in part for water lost by evaporation at the other heat exchanger.

MAION F. KNoY.

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