US2280425A - Air conditioning apparatus - Google Patents

Description

April 21, 1942.

c. M. SANDERS; JR AIR CONDITIONING APPARATUS Filed June 2, 1938 Fla. 1

INVENTOR cmmz; nsanosmm ATTORN Patentecl Apr. 21, 1942 2,280,425 AIR C(DNI JITIONING APPARATUS Charles M. Sanders, Jr., Oak Park, 11]., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, .Pa., a corporation of Pennsylvania Application June 2, 1938, Serial No. 211,310

13 Claims.

My invention relates to air conditioning apparatus, more particularly to a'refrigerant evaporator for cooling and dehumidifying air, and it has for an object to provide improved apparatus. a i

A further object is to provide improved means for varying the capacity or cooling effect of the evaporator for partial load operation.

A moreparticular object is to reduce the effective portion of the.evaporator for partial load operation while at the same time maintaining the effective portion at a sufficiently low tempertaure to maintain a desired degree of dehumidiflcation.

A further object is to reduce the portion of the evaporator montalning liquid refrigerant.

Apparatus incorporating my invention includes a conventional evaporator of the so-called dry type, including a plurality of coils through which refrigerant flows in parallel and over which the air may flow either in series or in parallel,

- more commonly in parallel. Liquid refrigerant is distributed to the several coils in any known manner and the admission thereof from a common supply. is controlled by a thermostatic expansion valve which includes a temperature responsive element subjected to the temperature of the vaporized refrigerant discharged from the several coils ofthe evaporator, the temperature element being usually strapped to the suction "conduit. In accordance with my invention, I

provide means for selectively extracting or bleeding a small portion of refrigerant from one of the coils at an intermediate point of the refrigerant path and I convey this extracted re-- frigerant to the suction conduit at a point such that the temperature responsive element is affected by the temperature thereof. Accordingly,

the expansion val e restricts theadmission of liquid refrigerant, to all of the coils, so that vaporization of refrigerant is completed at a point adjacent the extraction point. Thus, the portion of the evaporator containing liquid refrigerant is reduced.

The above and other objects are effected by my invention as will be apparent from the following description and' claims taken in accordance with the accompanying drawing, forming a part of this application. in which:

Fig. 1 is a diagrammatic view of air conditioning apparatus incorporating my invention; and

Pisa-2 and 3am enlarged detail views of modifications thereof. I

Referring to the drawing in detail I show an mixed and enter an air conditioning chamber l3 containing an evaporator M. A motor driven Ian l5 draws the air through the chamber l3 and over the evaporator I4 and discharges the same through a duct I6 to the enclosure Ill.

The evaporator I4 is of conventional construction, comprising a plurality of serpentine refrigerant coils ll, the, coils shown having four tubes. Liquid refrigerant is supplied under control of an expansion valve 18 and is distributed to the inlet ends of the coils by a group of dis tributor tubes 19 which are also sometimes referred to as capillary tubes. The outlet ends of the several coils are connected to a discharge or suction header 2| which is in turn connected unload the associated cylinders when the solenoids are energized. The compressed refrigerant is conveyed through a conduit to a condenser 26, from which thecondensed refrigerant is conveyed through a supply conduit 21 to the valve l8.

The-valve I8 is of the type commonly known as a thermostatic expansion valve, regulating the admission of liquid refrigerant to the evaporator so as to maintain a'predetermined desired bulb 28 arranged in contact with the suction conduit 22. The bulb 28 preferably contains fluid similar to that used as refrigerant and provides a pressure varying as a function of the temperature of the vaporized refrigerant. This pressure is communicated to the valve through a tube 29 and is. imposed thereon in valve opening direction. The pressure of the vaporized refrigerant-in the conduit. is alsocommunicated through a tube 2| and imposed on the valve in valve closing direction; The resultant of the two pressures is, therefore, ameasure of the superheat of the vaporized refrigerant, so that the valve regulates the refrigerant admission so as to maintain said degree of super-heat substantween the second and third tubes of the coiland the other end is connected to the suction conduit 22 at a point in advance of the thermostatic bulb 28. A valve 33 is connected in the conduit 32 and is operated by a solenoid 34, the valve being opened when the solenoid is energized and closed when the solenoid is deenergized.

.The control for the apparatus includes line conductors L1 and L: which supply electric current, a masteror entrance switch 35 and a twostep thermostat T provided with contacts 36 and 31. contacts 36 as the temperature in the enclosure and to open the contacts 31 as the temperature exceeds a slightly higher predetermined value, such as 81 F. The contacts 36 control a circuit 38 which controls the motor-compressor unit 23. The solenoids of the unloader mechanisms 24 and the solenoid 34 are connected in parallel, the circuit 39 therefor extending through the contacts 36 and 31 in series. It is to be understood that the illustration of the control is diagrammatic,

and that suitable conventional relays and other known expedients and instrumentalities commonly used in the art may readily be applied by anyone skilled in the art.

Operation Consider first that the temperature is above 81, calling for full load operation. This means that the contacts 36 are closed to effect operation of the motor-compressor unit. The contacts 31 are open to deenergize the solenoid 34 and close the valve 33 and to deenergize the solenoids of the-unloader mechanisms 24, so that all the cylinders of the motor-compressor unit are loaded. The apparatus now operates in a conventional manner. Refrigerant is compressed by the compressor, condensed in the condenser and admitted to the evaporator under the control of the thermostatic expansion valve l8. The refrigerant is distributed to the several coils l1 and evaporated in the coils by the heat extracted from the air flowing over the evaporator. The vaporized refrigerant returns to the motor-compressor unit through the suction conduit 22. Inasmuch as the valve 18 controls the refrigerant in such a manner as to maintain a constant degree of superheat of the discharged refrigerant vapor, preferably about F., it will be apparent that a relatively small and substantially constant portion of each coil adjacent the outlet end will contain refrigerant which hasbeen fully vaporized and is being superheated. The remainder of eachv coil contains liquid refrigerant and is at sumciently low temperature to cool and dehumidify the air flowing over the evaporator.

The apparatus is designed, by proportioning compressor capacity to evaporator surface and capacity, so that the air is cooled to a sufiiciently low temperature to effect the desired degree of dehumidification of the air. When the temperature drops to a value between 80 and 81 indicating a reduced .cooling demand, partial load operation is provided. At

The thermostat T is arranged to close the' l6 exceeds a predetermined value, such as 80 F.,

such a temperature, the contacts 31 are closed thereby energizing the several solenoids. The

unloader mechanisms 24 unload two of the compressor cylinders, so that the compressor capacity is reduced to one-half. The solenoid 34 opens the valve 33 to by-pass a small portion of the refrigerant flowing through the lower-most coil l8 to the suction conduit 22. The admission of this refrigerant to the suction conduit reduces the temperature of the vaporized refrigerant and of the suction conduit, so that the pressure within the thermostatic bulb 28 is reduced and the expansion valve operates to reduce the admission of liquid refrigerant to the several coils. The valve restricts the admission so that approximately one-half of each coil contains liquid refrigerant.

In the operation Just described, the reduced compressor capacity is balanced by a corresponding reduction in the liquid-containing or fully effective portion of the evaporator, so that the suction pressure in the evaporator is maintained at a sufficiently low value to enable said liquidcontaining portion to be effective to dehumidify the air flowing over the evaporator. There is thus provided suitable means for operating at partial load while at the same time maintaining the temperature of the effective portion of the evaporator at a sufiiciently low temperature for dehumidification.

The present invention resides in novel and improved means for varying the portion of the evaporator containing liquid refrigerant. It may be used in connection with any suitable control system, such as the one illustrated or the one disclosed and claimed in the application of L. G. Huggins, Serial No. 157,681, filed August 6, 1937.

In Fig. 2, I show a modification in which the by-pass conduit 32 projects into the interior of the suction conduit 22 and discharges directly against that part of the wall of the suction conduit which is in contact with the thermostatic bulb 28. The purpose of this arrangement is to subject the bulb 28 more nearly to the temperature of the refrigerant at the intermediate point of the coil to which the by-pass conduit 32 is connected and to reduce the extent to which it is influenced by the higher temperature of the vaporized refrigerant flowing through the header 2 I.

In the embodiment shown in Fig. 3, the bypass conduit 32a extends first in direct contact with the thermostatic bulb 28 and then discharges into the interior of the suction conduit against the portion in contact with the thermostatic bulb 23. With this arrangement, the bulb '28 is subjected still more fully to the temperature of therefrigerant flowing through the by-pass conduit and affected to a lesser extent by the higher temperature of the refrigerant flowing from the header 2|.

When the thermostatic bulb 28 is subjected fully to the temperature of the refrigerant at the point of extraction, the valve 28 will control the admission of refrigerant to the evaporator so that liquid refrigerant will be completely vaporized and the refrigerant vapor will be superheated 10 degrees F. at the point of extraction, just as if the refrigerant were returned to the suction conduit after passing through the first two rows of the coils. However, the vaporized refrigerant, other than the small portion by-passed, continues on through the third and fourth rows in which it is further superheated.

The liquid containing or effective portion of the evaporator, when the valve 33 is open, may be varied as desired by correspondingly varying the extraction point at which the by-pass conduit 32 is connected to one of the coils. It may also be varied by varying the degreeto which the bulb 28 is subjected to the temperature of the refrigerant at the point of extraction.

While Ihave shown my invention in several forms, it will be obvious to those skilled in the art that itis not so limited but is susceptible of various other changes and modifications without departing from the spirit thereof, and I desire,

therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

WhatIclaim is:

1. In refrigerating apparatus, the combination of an evaporator having a refrigerant passage, a valve for controlling admission of liquid refrigerant tosaid passage, a suction conduit connected to the outlet end of said passage for receiving vaporized refrigerant therefrom, means for controlling said valve in accordance with the superheat of the vaporized refrigerant discharged from said refrigerant passage to said conduit and including temperature responsive means subjected to the temperature of said vaporized refrigerant, and means for selectively by-passing refrigerant from-said passage at an intermediate point there- I of to said suction conduit and subjecting said temperature responsive means to the temperature of said by-passed refrigerant whereby said valveregulates the admission of liquid refrigerant to said passages so that a smaller portion of the passage contains liquid refrigerant. 2. In refrigerating apparatus, the combination of evaporator means comprising a plurality of refrigerant passages, a valve for controlling admission of liquid refrigerant to said passages, a suction conduit connected to the outlet ends of said passages for receiving vaporized refrigerant therefrom, means for controlling said valve in accordance with the superheat of the vaporized refrigerant discharged from said refrigerant pas-'- sages to said conduit and including temperature responsive means subjected to the temperature of said vaporized refrigerant,. and 7 means for selectively by-passing refrigerant from one of said frlgerant leaving said evaporator for controlling said valve inresponse to said temperature, and

a means for selectively reducing the average temperature imposed on said temperature responsive element below that of said leaving refrigerant.

5. In apparatus for cooling ,an enclosure, the combination of an evaporator, a compressor, a condenser, and an expansion valve connected in a refrigerant circuit, means for conveying airin heat transfer relation-to said evaporator and into the enclosure, means including 'a temperature-responsive element subjected to the temperature of the vaporized refrigerant leaving said evaporator for controlling said valve to control the super- 6 heat of said vaporized refrigerant, and means operable in response to a condition of the air in the enclosure for withdrawing refrigerant from the circuit at a point containing liquid refrigerant and utilizing-the withdrawn refrigerant to reduce the temperature imposed on said temperature responsive element and thereby causing said valve control means to maintain a higher degree of superheat of said vaporized refrigerant.

'6. In apparatus for cooling an enclosure, the combination of a refrigerant circuit including a liquid refrigerant supply line, a valve, an evaporator, and a suction conduit connected in refri erant flow relation in the order stated, means for conveying air in heat transfer relation to said evaporator and into the enclosure, means including a temperature-responsive element subjected to the temperature of the vaporized refrigerant in said suction conduit for controlling said valve to control the superheat ofv said vaporized refrigerant, and means operable in response to a condition of the air in the enclosure for withdrawing refrigerant from therefrigerant circuit at a point containing liquid refrigerant and admitting the passages at an intermediate point thereof to said suction conduit and subjecting said temperature responsive means to the temperature of said by I passed refrigerant, whereby said valve regulatesthe admission of liquid refrigerant to said passages so that a smaller portion of each passage contains liquid refrigerant.

3. In air cooling-apparatus, the combination of an evaporator of the dry type, means forsupplying liquid refrigerant thereto, a suction conduit for removing vaporized refrigerant from the evaporator, a valve for controlling flow of liquid refrigerant to the evaporator, means responsive trolling said valve, and means for by-passlng refrigerant from the evaporator at an intermediate point of the refrigerant flow path therein. to saidsuction conduit to modify the temperature imposed on said temperature responsive means and thereby to vary the portion of the evaporator containing liquid refrigerant.

4. In air cooling apparatus, the combination of an-evaporator, a compressor, a condenser and to pressure of the vaporized refrigerant and to the temperature of said suction conduit for conwithdrawn refrigerant to the suction conduit at a point as far upstream as said temperature-responsive element to reduce the temperature imposed on said temperature-responsive element and thereby causing said valve control means to maintain a higher degree of superheat of the vaporized refrigerant leaving the evaporator.

, 7. In combination with a refrigerating apparatus having a plurality of evaporators arranged in parallel for evaporating refrigerant, a distributor for distributing liquid refrigerant to the evaporators, a common outlet for the evaporators and means for circulating refrigerant through the evaporators, a thermostatic expansion valve including thermostatic means responsive to the temperature of superheated refrigerant adjacent the common outlet for the evaporators for regulating the flow of liquid refrigerant to the evaporators through the distributor to maintain a desired amount of liquid refrigerant in the evaporators, and means fordiverting a portion of the liquid refrigerant which hasv passed through the expansion valve and supplying said diverted portion to said common outlet for cooling the thermostatic means.

an expansion valve connected in a refrigerant circuit, means including a temperature responsive element subject to the temperature of the re 8. .In combination with a refrigerating apparatus having evaporator means in which refrigerant is evaporated for controlling the-condition of a medium and means for circulating refrigerant through the evaporator means, a thermostatic expansion valve including thermostatic meansresponsive to the temperature of the superheated refrigerant adjacent the outlet of the evaporator means for regulating the flow of refrigerant to the evaporator means to maintain a desired amount of liquid refrigerant in the evaporator means, means for cooling the thermostatic means of the thermostatic expansion valve to change the amount of liquid refrigerant maintained in the evaporator means, and means responsive to the condition of the medium being controlled by the evaporator means for controlling said lastmentioned means.

9. In combination with a refrigerating apparatus having evaporator means in which refrigerant is evaporated for controlling the condition of a medium and means for circulating refrigerant through the evaporator means, a thermostatic expansion valve including thermostatic means responsive to the temperature of the superheated refrigerant adjacent the outlet of the evaporator means for regulating the flow of refrigerant to theevaporator means to maintain a desired amount of liquid refrigerant in the evaporator means, conduit means for passing refriegrant in heat-exchange relationship with the thermostatic means of the thermostatic expansion valve for cooling the thermostatic means to change the amount of liquid refrigerant maintained in the evaporator means, valve means in said conduit means for controlling the flow of refrigerant therethrough, and means responsive to the condition of the medium being controlled by the evaporator means for controlling said valve Y means.

orator means, means for cooling the thermostatic means of the thermostatic expansion valve by the evaporation of liquid refrigerant adjacent the thermostatic means to change the amount of 1iquid refrigerant maintained in. the evaporator means, and means responsive to the condition of the medium being controlled by the evaporator means for controlling said last-mentioned means.

11. In combination with a efrigerating apparatus having evaporator means in which refrigerant is evaporated for controlling the condition.

of a medium and means for circulating refrigerant through the evaporator means, a thermostatic expansion' valve including thermostatic means responsive to the temperature of the superheated refrigerant adjacent the outlet of the evaporator means for regulating the flow of refrigerant to the evaporator means to maintain a desired amount of liquid refrigerant in the evaporator means, means for supplying liquid refrigerant to said superheated refrigerant at a point as far upstream as the thermostatic means of the thermostatic expansion valve for cooling the thermostatic-means to change the amount of liquid refrigerant maintained in the evaporator means, and means responsive to the condition of the medium being controlled by the evaporator means for controlling said last-mentioned means.

12. In a refrigerating system, the combination of an evaporator having a plurality of conduits each having an inlet and an outlet, a refrigerant distributor connected to the inlet of each conduit, a single expansion valve for controlling flow of liquid refrigerant to the distributor, said single expansion valve including an element responsive to the temperature of thevaporized refrigerant discharged from the evaporator, conduit means for withdrawing liquid refrigerant from a portion of the refrigerating system containing liquid refrigerant at apressure sufficient to cause flow through the conduit means and supplying said withdrawn refrigerant to said discharged vaporized refrigerant at a point as far upstream as the temperature-responsive element, whereby the temperature of the latter is reduced, valve means controlling flow through said conduit .means, and means responsive to a condition brought .about by evaporation of refrigerant in said evaporator for controlling said last-mentioned valve means.

13. In combination with a refrigerating apparatus having a plurality of evaporators arranged in parallel for evaporating refrigerant, a distributor for distributing liquid refrigerant to the evaporators, a common outlet for the evaporators and means for circulating refrigerant through the evaporators, a thermostatic expansion valve including thermostatic means responsive to the temperature of the superheated refrigerant adjacent the common outlet for the evaporators for regulating the flow of liquid refrigerant to the evaporators through the distributor to maintain a desired amount of liquid refrigerant in the evaporators, and means for cooling the thermostatic means of the thermostatic expansion valve to change the amount of liquid refrigerant maintained in the evaporators.

CHARLES M; SANDERS, JR.

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