US2919558A

US2919558A - Air conditioning system

Info

Publication number: US2919558A
Application number: US654898A
Authority: US
Inventors: Rodney F Lauer
Original assignee: Borg Warner Corp
Current assignee: Borg Warner Corp
Priority date: 1957-04-24
Filing date: 1957-04-24
Publication date: 1960-01-05
Anticipated expiration: 1977-01-05

Description

Jan. 5, 1960 R. F LAUER AIR CONDITIONING SYSTEM Filed April 24, 1957 I "a f: a r& -3 I E0770? BTULB.

INVENTOR. Ron/var 14054:

BY W W ATTO 1 United States Patent 2,919,558 AIR CONDITIONING SYSTEM Rodney F Laner, Spring Garden Township, York County, Pa., assignor to Borg-Wamer Corporation, Chicago, 111., a corporation of Illinois Application April 24, 1957, Serial No. 654,898

Claims. (Cl. 62160) This invention relates to reversible refrigerating apparatus more commonly known as heat pumps.

It is well known, of course, that refrigerating apparatus can be reversed and utilized for heating an enclosurerather than for cooling an enclosure. Operated in this manner, heat is picked up from outside air or water by evaporating low temperature refrigerant which is then compressed to a sulficiently high pressure and corresponding temperature by the refrigerating compressor to give up its heat to the air within the enclosure, the'refrigeraiit becoming condensed thereby. Since in the great majority of instances there is not sufficient amounts of water practically available, outside air must be utilized as the heat source.

There are many factors limiting the use of outside as a heat source, however. The primary one is the 'fact that as the outside air temperature drops, the capacity of the apparatus drops at the very time when heating requirements are increasing. This drop is caused by two factors: one, as the outside air temperature drops, the temperature differentials at which the compressor must operate correspondingly increase, since the upper or condensing temperature must remain fairly constant and at an elevated temperature. The volumetric efficiency of the compressor thereby decreases, since it is a well established fact that the efficiency of a compressor varies inversely as the pressure differential at which it must operate, corresponding to the temperature differential, increases. lwo, as the outside air temperature drops, the evaporator of the refrigerating apparatus must operate at a correspondingly lower temperature and corresponding pressure to remove heat from the outside air, thereby decreasing the density of the refrigerant gas circulated. It will be appreciated, of course, that with a compressor of a fixed volumetric displacement, as the density of the refrigerant decreases, the total weight of refrigerant circulated decreases with a corresponding decrease in capacity. The capacity, of course, is directly dependent on the pounds of refrigerant circulated through the apparatus.

For the above reasons, heat pumps, although performing satisfactorily in moderate climates, are not in general use in those chmates having sustained cold periods below 30 F. unless, as pointed out above, there is sufficient water available as a heat source.

With the continual expansion of air conditioning there has been a considerable research effort expended in trying to increase the capacity of the heat pump at low outside air temperatures. It can be easily understood that great economies could be effected if the same apparatus that was used to cool an enclosure in the summer could be efliciently used to heat the enclosure in the winter.

It is an object of this invention to provide a heat pump system utilizing a primary refrigerating apparatus including an outdoor heat-exchanger for absorbing heat from the outside air and an indoor heat-exchanger in heat-exchange relation with the room air to be heated and, in addition thereto, a secondary refrigerating apparatus including, an evaporator utilizing hot liquid refrig- 2,919,558 Patented Jan. 5, 1960 erant in the primary refrigerating apparatus as a heat source, and a condenser in heat-exchange relation with the room air to be heated.

The secondary refrigerating apparatus serves to cool the refrigerant liquid in the primary system from a condensing temperature in the order of 105 F. to a temperature in the order of F. The fact that the evaporator temperature of the secondary refrigerating apparatus .is considerably higher than the temperature in the outdoor heat-exchanger of the primary refrigerating apparatus, which for winter operations acts as an evaporator at temperatures ranging down to 0 F., results in a high co-efiicient of performance for this secondary apparatus which reflects on the overall co-eflicient of performance of the entire system in a beneficial way. The outside air cooling capacity of .the primary system is increased by reason of the fact that each pound of refrigerant circuiated to the outdoor neat-exchanger contains fewer 'B.t.u.s, having been cooled by the secondary refrigerating apparatus, and therefore can pick up more B.t.u.'s in evaporation. These extra B.t.u.'s are transrerred to the secondary apparatus and are then discharged into the air to be heated by the condenser of the secondary refrigerating apparatus.

it is a further object of the invention to provide a heat pump system as aboveset out and wherein actuating means are provided for the secondary apparatus responsive to a predeterm ned low outside air temperature. in operation "the pr rn'ary refrigerating apparatus, which cools air during summer operation, may be reversed as soon as there is a need for heating in the enclosure. This apparatus generally will be able to supply suflicient heat down to some predetermined low temperature, say 30 F. As the outside temperature reaches the predetermined low point, a control W111 actuate a switch putting the secondary apparatus in operahon to provide the additional heating required.

A still rurtner object of the invention is to provide an air conditioning system including a primary refrigeratmg apparatus having an indoor heat-exchanger in heatexciiange relation with the air to be heated and an outdoor heat-excnanger in heat-exchange relation with the outside air and including a secondary refrigerating apparatus comprising a condenser in heat-exchange relation with the air to be heated and an evaporator in heatexchange relation with liquid refrigerant flowing between the indoor and outdoor heat-exchangers of the primary apparatus; and means for directing the refrigerant in a Iii'st path through said heat-exchangers when cooling is desired and in a reversed path when heating is desired and further including means responsive to a predetermined low-outdoor temperature for actuating the secondary apparatus.

The invention consists of the novel constructions, arrangements and devices to be hereinafter described and vclaimed for carrying out the above-stated objects and such other objects as will appear from the following description of preferred embodiments of the invention described with reference to the accompanying drawings, in which:

Fig. 1 is a schematic representation of an air conditioning system embodying the invention, including a re-' a motor 14 is positioned to withdraw air from the enclosure via inlet 11 and. thence through duct 10, dischargferring to an indoor heat-exchanger, I mean only that the heat-exchanger is in heat-exchange relation with the air to be heated or cooled. When referring to the outdoor heat-exchanger, I mean only that the heat-exchanger isin heat-exchange relation with outside air. It will be appreciated-that the terms indoor and outdoor refer solely to the function of the heat-exchangers rather than to their physical location. A hot gas line 29 connects the discharge 'of compressor 16 with a three-way.

valve 21. From three-way valve 21, refrigerant lines 22 and23 are provided, line 22 leading to the indoor heatexchangcr and line 23 to the outdoor heat-exchanger. A suction line 24 communicates valve 21 back to' the inlet of the compressor. Heat-

exchangers

18 and 19 are interconnected by a liquid line 25 having a restrictor or capillary tube-26 therein. 7 I

A duct 27 is provided with an inlet 28 and an outlet 29 communicating with the outside air space. Outdoor heat-exchanger 1 9'is locatedwithin'duct 2 7, and a' fan 30 driven by a motor 31 is provided and positioned to circulate outside thereover. p x

A secondary refrigerating apparatus is provided and comprises'acompr'essor 32 driven by a motor 33 andincludeshneva riorator 34, and vacondenser 35 located .in

duct 10;" 'Evapor'ator'3'4 is in heat-exchange relation with,

theliquid line 25 which interconnects indoor heat-ex: changer18 with outdoor heat-exchanger 19. A hot gas line 36 connects the discharge of compressor 32 with condenser 35. The condenser communicateswith the evaporator through liquid line 37 having a restrictor or capillary'tub'e 38 therein. A suction line 39 connects the evaporator to the'inlet of the compressor 32 to complete the circuit. V

A duct 4-0 having a filter 41 therein, connects the duct 10 with the outside air' space by way of an inlet 42 should it be desired to bring in a certain amount of outside air to mix with the circulating .room air passing through duct 10. A damper 43 is provided for regulating the flow of outside air.

Power for operating the apparatus is supplied through a master switch 44. With switch 44 closed, electrical current is suppied to

lines

45 and 46 which are connected directly to motor 17.

Lines

47 and 48 are appropriately connected across

lines

45 and 46 and are directlyconnected to motor 31.

Lines

49 and 50 are also connected across

lines

45 and 45 and are connected to motor 14. I A thermostaticrlly controlled soenoid switch 51, comprising a switch blade 52 and solenoid 53, is provided in line 45 and is connected to a conventional heating-cooling thermostat 54 which controls the operation'of the switch 51. Leads. 55 and 56 are connected directly across

lines

45 and 46 and lead to a transformer 57 for reducing the volvge to-thermostat 54. Leeds 58 and 59join the thermostat with solenoid 53 for energizing thesarne.

Apair of le:

ds

60 and 61 are connected across

lines

45 and 46 and connected to the secondary compressor motor 33. in order that'motor 33 be not actuated when switch 44 is first closed, line 6 1-has a thermost tically controled switch 62 therein connected to a bellows 63 operativefy connected to a thermostatic control bulb 6 4 by way of a capillary 65. Control bulb 64 is so set th t upon a, predetermined low outside air temperature in the order of about 30 F., bellows 63 will contrrct, closing When cooling of the enclosure R is desired, valve"2'1 is rotated 90 in a clockwise, direction to its position as shown in Fig. 2. Thermostat 54 functions to open switch 51 on a drop in temperature in the conditioned space, shutting down the primary refrigerating apparatus. On rise in temperature when cooling is, therefore, indicated, thermostat 54 acts to energize solenoid 53 to actuate switch blade 52 to its upper, closed position to actuate the primary refrigerating apparatus. With switch blade 52 closed under the influence of thermostat 54, an electricai circuitis completedto electric motor 17 through

lines

45 and 46. Since leads 49 and 50 connected tomotor 14 are connected directly across

lines

45 and 46, motor 14 is actuated at this time. Similarly, motor 31 is actuated since leads 47 and 48 connected thereto are directly connected across

lines

45 and 46. Primaryrefrigerant gas compressed in compressor 16 then flows via hot gas line 20, valve 21 and line 23 into the outdoor heat-exchanger 19 where it gives up its heat to the outside air and-is condensed. The high pressure liquid then flows through capillary 26 and has its pressure and corresponding temperature reduced thereby, The now low pressure, cold liquid then flows via' liquid line 25 into indoor heatexchanger 18 picking up heat from the room air flowing thereover. As therefriger'ant vaporizes in heat-exchanger 18, the'vaporo'r gas fiows' via refrigerant line 22, through valve 21 and suctionline 24-.back to the inlet of compressor 16 to complete. the cycle. The secondary refrigerating'apparatus is, of course, not operative during the 30 d ina y e In operation, when heating is desired, valve 21 is set as.

shown. On the lieating cycle thermostat 54 functions reversely to its operation on the cooling cycle. As the temperature inthe enclosure drops below the desiredtemperature, thermostat 52 closesswitch- 51 allowing current to flowto the'rnotors operating the primary refrigerating apparatus and fans 13,. and 30 (the same c rcuitsare set up as on the cooling cycle). Upon a rise in temperature .in the conditioned space above the predetermined, level,

I comp etc the cycle.

switch '62 thereby actuating the motor 33 of compressor.

operation.

thermostat 54 will-open switch 51 and thereby discontinue the current supply to

motors

14, 17 and 31. With switch 51'closed, hot, primary, compressed refrigerant gas exits compressor 16 by way of hot gas line 20 flowing through valve 21 and thence into refrigerant line 22 leading to the indoor heat-exchanger18. The hot refrigerant gas is liquified by room air flowing through the duct 10 and over heat-exchanger 18 and gives up its heat of condensation to the said air. Hot liquid refrigerant leaves indoor heat-exchanger 18 by way of liquid line 25. In flowing through capillary 26, the pressure and corresponding temperature of the refrigerant liquid en route to the outdoor heat-exchanger 19 is reduced so that it will be at a temperature sufiiciently low to pick up heat from the cold outside air flowing over the heat-exchanger under the niiuence of fan 30. In its passage through the heat-exchanger 19, the liquid refrigerant is vaporized and this vapor or gas flows through refrigerant line 23, valve 21 and suction line 24 back to the inlet of compressor 16 to When additionalcapacity is called for, switch 62 is closed underthe influence of bulb 64 and the secondary refrigerating apparatus is activated by current flow through,line.,45,, lead 60 .to motor 33 and thence through lead 61 (with switch 62 closed) and back to line 46 to..complete. the circuitr Cold secondary liquid refrigerant in theievaporator 34 removes heat from the hot primary refrigerant liquid flowing through liquid line 25 en route :from heat-exchanger 13 to heat-exchanger 19. This serves both to sub-cool the primary reirigerant liqu'd and-t0- vaporize the secondary refrigerant liquid in evaporator 34., The secondary refrigerant vapor or gas thenfiows by way of suction line 39 into the inlet of compressor 32. It is compressed therein to a high pressure and corresponding high temperature and the hightemperature gas thenflows by way or hot gas line 36 to condenser 35 where the gas is condensed by the room air flowing thereover, giving up its heat of condensation to the room air. The secondary refrigerant, now liquid, then flows via liquid line 37 through capillary 38 wherein its pressure and temperature are correspondingly reduced as it passes therethrough. The cold low pressure liquid then flows back into the evaporator 34 in heat-exchange relation with the hot primary refrigerant liquid therein to complete the circuit.

Fig. 3 is a pressure-enthalpy diagram illustrating the thermal cycle of my heat pump system. The normal heat pump system cycle would be as follows: starting at A the refrigerant gas is compressed in compressor 16 to point B increasing both its pressure and its total heat content. The increase in total heat content due to compression is the amount BC B.t.u.s per pound. The refrigerant is condensed to a liquid at point D in indoor heat-exchanger 18 at a constant pressure. The total amount of heat given up in the indoor heatexchanger to the fluid flowing thereover is, therefore, the amount BD B.t.u.s per pound. In passing through capillary 26, the refrigerant is then throttled down to a considerably lower pressure to point G and at a constant enthalpy. The refrigerant evaporates in outdoor heat-exchanger 19 to point A picking up AG B.t.u.s per pound.

What I have done then is sub-cooled the primary refrigerant liquid from D to point E'in evaporator 34. The B.t.u.s per pound picked up in the secondary refrigerating apparatus would then be DE. This heat, plus the heat of compression of the secondary compressor, is then given up to the air flowing over condenser 35. The primary refrigerant is then expanded from E to F and in evaporating in outdoor heatexchanger 19, picks up the extra B.t.u.s per pound G-F which is equivalent to D-E, the amount picked up by the secondary apparatus.

I wish it to be understood that my invention is not -to be limited to the specific constructions and arrangements shown and described, except only insofar as the claims may be so limited, as it will be apparent to those skilled in the art that changes may be made without departing from the principles of the invention.

What is claimed is:

1. A heating system comprising a primary refrigerating apparatus, including a compressor, an indoor heatexchanger in heat-exchange relation with a fluid to be .heated, and an outdoor heat-exchanger in heat-exchange relation with outside air, all connected in a closed refrigerating circuit; means for directing a refrigerant fluid from said compressor via said circuit to said indoor heat-exchanger thence to said outdoor heat-exchanger and back to said compressor; and a secondary refrigerating apparatus, including an evaporator for removing heat from refrigerant fluid en route from said indoor heat-exchanger to said outdoor heat-exchanger, a condenser for rejecting said heat into the fluid to be heated, and means for actuating said secondary refrigerating apparatus independently of said primary refrigerating apparatus.

2. An air conditioning system comprising a primary refrigerating apparatus, including a compressor, an indoor heat-exchanger, an outdoor heat-exchanger and refrigerant flow connections therebetween; means for directing refrigerant fluid from said compressor to said outdoor heat-exchanger, thence to said indoor heatexchanger and back to said compressor when cooling is desired; means for directing said refrigerant fluid in a reverse path when heating is desired whereby the funcions of said heat-exchangers are reversed; means for flowing a fluid to be conditioned in a path including said indoor heat-exchanger; means for flowing outside air over said outdoor heat-exchanger; and a secondary refrigerating apparatus, including a condenser placed in said conditioned fluid path and an evaporator in heatexchange relation with liquid refrigerant flowing between said indoor and outdoo heat'exchangers.

3. The system as set out in claim 2, wherein the evaporator of said secondary refrigerating apparatus is in heat-exchange relation with that portion of the refrigerant flow connections between the indoor and outdoor heat-exchangers.

4. The system as set out in claim 2; and actuating means for said secondary refrigerating apparatus responsive to a predetermined low outside air temperature.

5. A heating system comprising a primary refr gerating apparatus including a compressor, an indoor heatexchanger in heat-exchange relation with air to be heated, an outdoor heat-exchanger in heat-exchange relation with outside air, and refrigerant flow connections therebetween; a secondary refrigerating apparatus including a condenser in heat-exchange relation with the air to be heated and an evaporator in heat-exchange relation with the refrigerant flow connections between the indoor and outdoor heat-exchangers; and actuating means for said secondary refrigerating apparatus responsive to a predetermined low outside air temperature.

6. An air conditioning system comprising a primary refrigerating apparatus including a compressor, an indoor heat-exchanger, an outdoor heat-exchanger and refrigerant flow connections therebetween; means for directing refrigerant fluid in a path from said compressor to said outdoor heat-exchanger, thence to said indoor heat-exchanger and back to the compressor when cooling is desired; means for directing said refrigerant fluid in a reverse path when heating is desired whereby the functions of sad heat-exchangers are reversed; means for flowing a fluid to be conditioned in a path including said indoor heat-exchanger; means for flowing outside air over said outdoor heat-exchanger; a secondary refrigerating apparatus for removing heat from hot refrigerant liquid flowing from said indoor heat-exchanger to said outdoor heat-exchanger when the system is heating and including a condenser placed in said conditioned fluid path; and means for actuating said secondary refrigerating apparatus responsive to a predetermined low outside air temperature.

7. A heat pump system comprising a first refrigerating apparatus including an outdoor heat-exchanger for absorbing heat from outside air and an indoor heatexchanger in heat-exchange relation with a fluid to be heated and supplied to an enclosure; a second refrigerating apparatus including, an evaporator utilizing hot refrigerant in said first apparatus as a heat source and a condenser in heat-exchange relation with the fluid to be heated; a first thermal responsive means for controlling operation of said first and second apparatus; and a second thermal responsive means for further controlling the operation of said second apparatus.

8. The system of claim 7 wherein said first thermal means is responsive to the temperature within the enclosure to be heated, and said second thermal means is responsive to outside air temperature.

9. A heat pump system comprising a first refrigerating apparatus including an outdoor heat-exchanger for absorbing heat from outside air and an indoor heatexchanger in heat-exchange relation with a fluid to be heated; and a second refrigerating apparatus including an evaporator utilizing hot refrigerant in said first apparatus as a heat source, a condenser in heat-exchange relation with the fluid to be heated, and actuating means for said second refrigerating apparatus responsive to a predetermined low outside air temperature.

10. A heat pump system comprising a first refrigerating apparatus including an outdoor heat-exchanger for absorbing heat from outside air, an indoor heatexchanger in heat-exchange relation with a fluid to be heated and a flow connection for the liquid refrigerant en route from said indoor heat-exchanger to said outdoor heat-exchanger; and a second refrigerating appararus including a condenser in heat-exchange relation with the fluid to be heated and an evaporator positioned in heat-exchange relationship with said flow connection for utillzing hot refrigerant in said first apparatus as a heat source.

References Cited in the file of this patent UNITED STATES PATENTS Gibson Nov. 12, 1940 McGrath May 20, 1941 Newton Jan. 6, 1948