US2885864A

US2885864A - Heat transfer system using expendable coolant

Info

Publication number: US2885864A
Application number: US540553A
Authority: US
Inventors: Harry L Benjamin
Original assignee: United Aircraft Products Inc
Current assignee: United Aircraft Products Inc
Priority date: 1955-10-14
Filing date: 1955-10-14
Publication date: 1959-05-12
Anticipated expiration: 1976-05-12

Description

May 12, 1959 H. l.. BENJAMIN 2,885,864

HEAT TRANSFER SYSTEM USING EXPENDABLE cooLANT Filed oct. 14, 1955 United States Patent() y HEAT TRANSFER SYSTEM USING c EXPENDABLE cooLANr 16 Claims. (Cl. til-51) Dayton, Ohio, assignor to United Inc., Dayton, Ohio, a corporation This invention relates to heat transfer systems, and particularly to such systems utilizing an expendable coolant.

While not so limited, the invention has especial application to problems of interior cooling an aerial craft capable of flight at speeds which are multiples of the speed of sound. Thus, the instant system is essentially selfcontained and may operate effectively to cool a predetermined space, as for example a compartment containing electronic equipment, by circulating and recirculating substantially the same body of air in such compartment without appreciable change in the rate of cooling of such air over a predetermined period of time.

An object of the invention is to introduce a principle of cooling by an expendable coolant in the application of electronic and like cooling packages to aerial craft.

Another object of the invention is to present a heat transfer system designed for high level substantially constant performance over a predetermined period of time. i

A'further object of the invention isto provide a unitary system of the kind described characterized by safe guards designed to prevent misoperation thereof.

Still another object of the invention is to incorporate in a heat `transfer system as described control devices responsive to the temperature of the air or other gaseous medium to be cooled and to the temperatureof the coolant, as well as overriding controls obviating misoperation as might result from failure to refill the coolant system. l I

A stillfurther object of the invention is to achieve effective cooling of recirculated air without the use of compressors and like bulky equipment, resulting in a refrigeration system of especial utility in aerial craft.

The drawing is a schematic presentation of the invention in its illustrated form. y

Referring thereto, principal elements of the system include a closed storage tank holding a quantity of an evaporative liquid coolant, in the present instance ammonia, and a heat exchanger 11 through which the ammonia from the tank 10 is guided in heat transfer relation to a gaseous medium, considered here to be air. The air is drawn from the space to be cooled and is forced by an axial vane fan 12 through the heat exchanger 11 and back to the space to be cooled. The

lower and upper ends of the heat exchanger 11 serve.

respectively as the inlet and outlet sides thereof, as regards the liquid flow, while the left hand and right hand sides thereof, or front and back, serve as the inlet and outlet sides for the air. Flow to the heat exchanger from the tank 10 is by way of a conduit 13. Flow from the liquid outlet side of the exchanger is by way of a conduit 14 in common communication with a conduit 15 leading back to the tank 10 and with a conduit 16 leading to waste, as to the atmosphere. The liquid coolant circulating system is, as noted, closed. A pressure relief valve 17 holds the fluid pressures in the tank 10 to a safe operating value. A pressure regulating valve 18 is interposed in the waste conduit 16 and serves to maintain the absolute pressure at the liquid outlet of rblies 19, 21 and 22, all normally closed. Respective "electro-

magnetic coils

23, 24 and 25 serve when energized to open the individual valves for flow therethrough. A by-pass conduit 26 is connected in the conduit 13 in parallel relation to the valve 19 therein. Within conduit 26 is a throttling or expansion valve 27. Still further, a ller connection 28 is interposed in the liquid coolant system for filling of the system, as by way of the by-pass conduit 26.

As heat is brought to the heat exchanger 11, by the flowing of heated air therethrough, the liquid ammonia therein is raised in temperature and in pressure. The vapors so produced How upward out of the heat exchanger by way of conduit 14 and in the open position of the valve 21 are returned by the conduit 15 to the top of tank 10 where they are condensed at the surface of the now sub-cooled liquid therein. A natural flow is, therefore, set up which continually raises both the temperature and the pressure in the heat exchanger and in the tank.

An electrical control system is provided operating essentially to power a motor 29 driving the fan 12 and to eifect opening and closing of the several valves 19, 21 and 22. A source 31 of electric power, which may be an A.C. generator or the like, is connected by`

power conductors

32 and 33 to opposite sides of a rectifier 34 which in turn supplies direct current to

power supply lines

35 and 36. A conductor 37 is connected across the supply lines `35 and 36 and has interposed therein an electro-magnetic coil 38 and a normally open starting switch 39. The switch 39' may be arranged in series relation with the means for initiating the heat load, to insure that the heat transfer apparatus begins to operate simultaneously with the imposition of such load. For example, closing of the switch 39 may be used to turn on electronic equipment which is the source of the heat to be dissipated.

Closing of the switch 39 energizes the coil 38 which pulls over a four pole starting relay 41. Three parts of the relay 41 close circuits, as indicated, through respective windings 42 of the three phase fan motor 29 which accordingly are energized, causing the fan 12 to operate to liow heated air through the heat exchanger 11. A part of such heat is absorbed in the liquid ammonia in the heat exchanger, as before noted, and vapors are released from the ammonia to initiate circulation of the coolant as before described. A fourth part 43 of the relay 41 closes a circuit in a conductor 44 extending between the

power supply lines

35 and 36, and in which is a signal light 45 which accordingly is illuminated and signifies that the heat transfer apparatus is in operation.

The opening of valves 19 and 21 to permit circulation between the tank 10 and heat exchanger 11 is made dependent upon the attaining of a predetermined high temperature value in the air. Thus, there is placed on the air outlet side of the heat exchanger an air temperature responsive thermostatic switch 46 normally open and interposed in a conductor 47 which at its one end is connected through a branch 48 with the aforementioned conductor 44 and thence to a power supply line. At its other end the conductor 47 extends into a step relay assembly 49 and more particularly to a switch arm 51 therein which together with a companion arm 52 make up a pair of relay arms movable between opposed positions simultaneously in response to the alternate energizing of opposing electro-magnetic coils 53 and 54. In the position of the parts shown in the drawing, arm 51 connects the conductor 47 to a contact 55 from which extends another conductor 56 including in a series relation therein the electro-magnetic coils 23 and 24 and extending to engagement with the power supply line 35 at a contact point S7. The closing of switch member 43, in the starting relay 41, accordingly results not only in illumination of the power light 45 but also in the opening of valves 19 and 21 shortly thereafter orY as soon as the air temperature rises to a minimum operating value as defined by the thermostat 46.

The valve 22 remains closed at this time. The coil 25 thereof is in a line 58 connected at its one end to the contact point 57 but at its other end to a contact 59 in the step relay assembly 49 and representing the alternate position of adjustment for the relay arm 51. In the illustrated position of the parts, therefore, the contact 59 is open and the circuit through coil 25 accordingly is open and the valve 22 controlled thereby remains closed. The opening of this valve is under control of a thermostatic switch 61 in the tank 10 and sensitive to the temperature, of the liquid coolant therein. At a predetermined high temperature, the switch 61 closes a circuit through a conductor 62 connected at its one end to a contact 63 in a filling switch assembly 64. The contact 63 is in the position of the parts illustrated engaged by a switch arm 65 which together with a switch arm 66 forms a pair of arms in the switch assembly 64 movable as a unit between alternate positions of adjustment. The arm 65 is connected through a lead 67 to the aforementioned conductor 48 which is in turn connected through conductor 44 and switch arm 43l to the power supply line 36. At

its other end the conductor-62 extends to power supply line 35 and it includes near such end the previously mentioned electro-magnetic coil 54 in the step relay 49.

Closing of the thermostatic switch `61 accordingly results in energizing of the coil 54. The pair of switch arms 51 and 52 thereby are pulled over to their alternate positions of adjustment, with the arm 51 leaving contact 55 and engaging contact 59. The result, it will-be apparent, is to energize coil 25 of valve 22 and at the same time to deenergize coils 23 and 24 of the valves 19 and 21. The

valves 19 and 21 accordingly close and the valve 22 opens. Further discharge of vapors from the heat exchanger 11 therefore is denied return to the tank but is directed instead to waste by way of the conduit 16. The system will continue so to operate, expending the vaporized ammonia, for so long as the heat exchange apparatus remains in continuous operation and irrespective of what may be the further change in temperature in the tank 10. Since the heated vapors from the heat exchanger no longer are being returned to the tank, the temperature therein will not rise appreciably above the value at which the thermostatic switch 61 closes, except as they may be influenced by ambient temperatures. Also, should the temperature in the tank 10 drop below the value at which switch 61 closed, the switch will open and coil 54 will be deenergized but no change in the position of the switch arms 51 and 52 will take place since the coil 53 also is deenergized and the switch arms are not spring loaded in either direction.

With the closing of valve 19, the further supply of liquid coolant from the tank 10 to the inlet side of the heat exchanger 11 is by way of by-pass passage 26 and expansion valve 27 therein. 'Ihe latter operates in a manner conventional in devices of its kind to admit liquid coolant from the tank to the heat exchanger at a more or less constant rate despite variations in temperature and pressure thereof, responding not only to the pressure of the coolant within the tank but also to the pressure and temperature of the coolant between the outlet side of the heat exchanger and the pressure regulating valve 18.

The iilling connection switch 64 is operated in conjunction with and if desired as a part of the-same operation by which the filler nozzle is inserted in the connectionv 28.

Thus, the switch arms 65 and 66 are interconnected by a part 68 and urged by a spring 69 normally to occupy the position illustrated wherein the arm 65 engages conftact 63 and arm 66 engages an open or blank Contact 71. Insertion of the ller nozzle, however, may be utilized mechanically to move the"l switch assembly to its alternate position of adjustment in which the switch arm 65 engages 'anbpen or blank contact v72 and the switch arm 66 engages' a contact 73 fromfwhich extends a conductor 74 leading to the supply line 35 and including in its length the'electro-magnetic coil 53 of the step relay 49. With the filling connection switch so positioned, the electro-magnetic coil 54 is deenergized so that the step relayswit'ch elements 51 and 52 move over to 'their illustrated positions. The valve 22`is at this time, therefore, closed and the system may be refilled without loss of any of the liquid to waste.

The switch-arm 52 of the step relay 49, when in its refill position as illustrated', vengages a contact 75 from which extends a conductor 76 extending into a holding relay 77 and out of they relay to the supply line'35. Included in the conductor 76 is an electro-magnetic coi1l78. A switch element 79 is included in-the relay 77 for inuencing by the coil 78 and is interposed in a conductor 81' extendingbetween the supply-

lines

35 and 36 and which further includes a reset signal light-82. around the coil 78 fromthe conductor 76 to the conductor 81 on one side of the switch 79. Adjustment of the step relay 49 to the refill position illustrated closes a circuit through the electro-magnetic coil 78v and closes switch 79 which in turn completes a circuit through conductor 81 and illuminates the reset light 82. The illuminated light 82 indicates tothe pilot or other person in charge of the system that the tank 10 has been refilled. The light remains illuminated, it will be recognized from the construction and arrangement of parts, throughout operation of the system, even though the step relay 49 is adjusted to its alternate position in response to rising temperature in the tank. When power to the system is cut olf, however, the switch 79 opensy and the holdingcircuit established through by-pass conductor 83 is broken. Should the system be putin operation'without adjustment of the filling connection switch 64, therefore, the reset light 82 will not go on and the pilot will be warned that theammonia tank l10 has not been'rei-lledl It will be understood in this connection, that the tank is filled prior to each ilight or other use of the heat transfer system and thatr heat exchanger size and construction, and the rate ofV evaporation of the ammonia, being calculated to produce a drop in temperature of the circulated air from a relatively high temperature to a low value corresponding approximately to the temperature value at which air thermostat 46 closes'. Further in such typical operation the throttling or`expansion valve 27 is designed to operate between extreme pressures in the tankl of 247 pounds at F. and 66 pounds at 35 F.

In further regard to ow of coolant fromy the tank 10, it will be understood that the driving force therefor is vapor pressure within the tank. The creation of such pressure is a function of heating Vof lthe coolant in the tank, as may be accomplished by relatively high ambient temperatures or by circulation of some of the coolant through the heat exchanger 11.

The system does not discharge to waste until a temperature has been reached in the tank insuring a pressure sufficiently higher than that maintained by the pressure regulator L18 to provide and ymaintain proper ow. As f A by-pass lead 83 extendsy be'fore noted, the system is designed to provide adequate cooling Aover a predetermined time interval, as for example a flight of six hours. Thus, the temperature at which the tank thermostat 61 closes is high enough to insure that in a flight of maxim-um duration the tank temperature will not drop below the value necessary to create the vapor pressures required for proper operation.

The utilizing of the heat exchanger 11 as a means for heating the coolant, in the initial phase of operation, obviates the need for a separate tank heater and its controls or of any other means for driving the coolant from the tank.

What is claimed is:

1. A heat transfer system utilizing an expendable coolant, including a storage tank holding an expendable uid coolant, a heat exchanger, means for circulating said coolant through said exchanger and back to said tank, and means for diverting llow out of said exchanger to waste in by-passing relation to said tank and in response to the exceeding of a predetermined temperature value in said tank.

2. A heat transfer system according to claim 1, characterized in that said last named means comprises an electrical circuit including a thermostatic switch in said tank and solenoids in series relation with said switch, and further comprises Valves controlled by said solenoids.

3. A heat transfer system utilizing an expendable coolant, including a storage tank holding an expendable iluid coolant, a heat exchanger arranged for the passage of said coolant and a gaseous medium therethrough in heat exchange relation, means for supplying coolant from said tank to said heat exchanger, valve means controlling How of said coolant, a fan for llowing the gaseous medium through said exchanger, an electrical control circuit including solenoid means for said valve means and a motor for operating said fan, and a manually operable switch for opening and closing said circuit through said motor and an automatic switch responsive to the temperature of said coolant for opening and closing said circuit through said solenoid means.

4. A heat transfer system utilizing an expendable coolant, including a heat exchanger, a storage tank holding an expendable fluid coolant, means conducting the coolant from said tank to said heat exchanger, alternate iiow paths from said heat exchanger to waste and back to said tank, separate normally closed valves controlling ow through said alternate flow paths, and temperature responsive means for opening said valves.

5. A heat transfer system according to claim 4, characterized in that the valve controlling flow to waste opens in response to attaining a predetermined high tem perature in said storage tank.

6. A heat transfer system according to claim 4, wherein another iluid is circulated through said heat exchanger, characterized in that the valve controlling iiow of said Huid coolant back -to said tank tends to open in response to attaining of a predetenmined high temperature by Said other fluid.

7. A heat transfer system, including a heat exchanger, a storage tank holding a quantity of an expendable iluid coolant, means for conducting said coolant to said heat exchanger, alternate ilow paths from said heat exchanger to waste and .back to said tank, ow control means responsive to attaining of a predetermined high temperature in said tank for closing olf return flow to said tank and opening flow to waste, and means adjusted in response to operation of said last named means maintaining lflow of said coolant to waste after opening thereof irrespective of the temperature in said tank.

8. A heat transfer system, including a heat exchanger, a storage tank holding an expendable liquid coolant, means for conducting said coolant from said tank to said heat exchanger, a fan for owing a gaseous medium through said heat exchanger, a rst normally closed flow path for said liquid coolant back to -said tank, a second normally closed ow path for said liquid coolant from said heat exchanger to waste, an electrical control circuit.

including means for starting said fan, a normally open thermostatic switch in said circuit closing at a predetermined high temperature of said gaseous medium to effect opening of (said ow path to said tank, and a normally open thermostatic switch in said tank closing at a predetermined high temperature in said tank to eifect closing of said last mentioned flow path and opening of the flow path to waste.

9. A heat transfer system according to claim 8, characterized 4by a relay in said circuit maintaining the flow path to said tank closed and the flow path to waste open after the closing of said thermostatic switch in said tank irrespective of the temperature in said tank.

10. A heat transfer system utilizing an expendable coolant, including a closed liquid coolant circulating system' comprising a storage tank and a heat exchanger having inlet and outlet sides communicating with said tank, an alternate ow path from the outlet side of said heat exchanger leading to waste, a normally closed valve in said alternate ow path, an electrical control system for said valve comprising an electromagnet which when energized opens said valve, thermostatic switch means in said tank closing a circuit through said electromagnet at a predetermined high temperature level, and manual switch means for opening the circuit through said electromagnet in overriding relation tosaid thermostatic switch.

.11. A heat transfer system according to claim l0, characterized by means for refilling said liquid circulating system, said normal switch means being settable in conjunction with the relling of such system.

12. A heat transfer system utilizing an expendable coolant, including a storage tank holding a liquid coolant, a heat exchanger having inlet and outlet sides communicating with said tank, means responsive to a changing condition of said coolant for opening said system for the escape to waste of coolant from the outlet side of said heat exchanger, said means including an electromagnetically controlled valve closed when deenergized, a control circuit including a step relay in a first position of which said valve is closed and in a second position of which said valve is open, means responsive to a changing condition of said coolant for moving said relay from iirst to second position, and other means for resetting said rel-ay to rst position.

13. A heat transfer system utilizing an expendable evaporative coolant, including a heat exchanger, means for ilowing a heated fluid therethrough, a storage tank holding the coolant, a ow line leading from the tank to said heat exchanger and a return flow line from said heat exchanger back to the tank, the coolant passing through the heat exchanger prior to entering said return ow line in heat transfer relation to said heated iluid, the force for flow of said coolant being vapor pressure in said tank, means for closing said return flow line in response to a rising temperature in said tank above a selected value higher than the temperature of vaporization of said coolant, an alternate ow line for said coolant out of said heat exchanger, and normally closed means in said alternate ow line operable concomitantly with the closing of said return flow line to open said alternate flow line.

14. A heat transfer system utilizing an expendable evaporative coolant, including a storage tank holding the coolant, the coolant being expelled from said tank by the force of vapor pressures therein created by the heating of said coolant to the temperature value of vaporization, a heat transfer device with which the coolant expelled from said tank is brought into contact, means to ow another and heated uid in contact with said device whereby to vaporize said coolant, means to return the vaporized coolant back to said tank to raise the pressure therein, and means responding to the attaining of a predetermined temperature in the tank indicating a capability of the tank to continue expelling coolant over a predetermined lengthl of timeto off tanky and maintain it closed during saidtime irrespective of subsequent dropsin temperature infsaid tank,jla path to AWaste fonvaporized coolant released from 'saidl heat transfer ydevice'during said predetermined-length of time, and lclosure means in said path connected' to Vthe last named means for concomitant operation whereby in response to the attaining of a predetermined temperature in the tank return flow to the tank is cut oi and the path to waste is opened.

15. A heat transfer system utilizing an expendable evaporative coolant, including a storagetank holding the coolant, the coolant being expelled from said'tank by the force of vapor pressures therein created by the heating of lsaid coolant to the temperature value of vaporization, a source of heat with which the expelled coolant is brought in heat exchange relation, means to return ow of the coolant fromsaid source to'said tank to utilize the heat from said source to raise the ltemperature insaid tank to a value suficient to continue expelling coolant therefrom over a predetermined length of time, thermal means responsive to the temperature in the tank, means connected to and operated by'said thermal means to close off return ow to the tank in the presence of a tank temperature at or abovesaid value, and means in common connection with said thermal means and said last named means operable concomitantly with the closing offof return ow to the tank to open oW from said heat source to waste.

16,.1A`herat transfer system utilizing an expendable evaporative coolant, including a storage tank holding the coolant, the coolant being expelled from said tank by the force of vapor pressures therein created by the heating of said coolant to the temperature value of vaporization, including `a heat exchange, a flow line to conduct coolant from said storage tank to said heat exchanger, another flow line to conduct the coolant from said heat exchanger to Waste, an alternate ow line to conduct the coolant from said heat exchanger back to said tank, a normally closed valve preventing flow in said alternate path, means for bringing another fluid into heat transfer relation to said coolant through said heat exchanger, means responding to a predetermined high temperature value of said second uid for opening said valve, and means respond' ing to a predetermined high temperature value of said coolant in the tank for closing said valve.

References Cited in the le of this patent UNITED STATES PATENTS 2,100,474 Fish Nov. 30, 1937 2,120,299 Stranaglia June 14, 1938 2,456,890 St. Clair Dec. 21, 1948 2,580,710 Wildhack Jan. 1, 1952 2,603,070 Gilmore July 15, 1952 2,657,542 Wildhack Nov. 3, 1953 FOREIGN PATENTS 470,624 Canada Jan. 9, 1951