US2279787A

US2279787A - Air conditioning apparatus

Info

Publication number: US2279787A
Application number: US157681A
Authority: US
Inventors: Leroy G Huggins
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1937-08-06
Filing date: 1937-08-06
Publication date: 1942-04-14
Anticipated expiration: 1959-04-14

Description

April 1942- G. HUGGINS I 2,279,787 I AIR CONDITIONING APPARATUS:

Filed Aug. 6, 1937 2 Sheets-Sheet 1 FHGJ.

our-nook AIR INVENTOR LEROY G Hus-ems.

BY i 2 ATTORNE April 14, 1942. G. HUG GINS ,2 ,7 7.

AIR CONDITIONING APPARATUS Filed Aug. 6, 1937 2 Sheets-Sheet 2 H IGH MOTOR LOW MOTOR SPEED OUTDOOR HIE HIGH MOTOR 25 SPEED WITNESSES:

INVENTOR Laaov G. Huacms ATroR Patented Apr. 14, 1942 min-1 OFFICE AIR CONDITIONING APPARATUS Leroy G. Huggins, Manuela-ohm, dam, to

Westinghouse Electric .4: Manufacturing Company, East Plttsburg Pa.,-a corporation of Pennsylvania Application August 6, 1937, Serial No- 157,681

I (c1. sz- -s) My invention relates to apparatus for cooling and dehumidifying air for an enclosure, and it has for an object to provide improved means for Another object is to provide air cooling and dehumidiiying apparatus including a variable speed compressor and an air cooling evaporator, and to maintain the refrigerant pressure in the evaporator sumciently low for dehumidifylng the when the compressor is operating at low speed. w

A further object is to vary the operation of the apparatus so as to maintain both the temperature and the humidity of the air in the enclosure withln desired limits. Still another object is to vary the sensible heat and the latent heat removal from an enclosure, and the ratio of sensible to latent heat, to maintain both the temperature and the humidity of the air in the enclosure within desired limits. v

The above and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which: Fig. 1 is a diagrammatic view of one. embodiment of .air conditioning apparatus embodying my invention;

Fig. 2 is an enlarged detail sectional view showing the thermostatic expansion valve;

Fig. 3 is a diagrammatic view of a second embodiment; and,

varying the operation thereof.

Fig. 4 is a diagrammatic view-of another modiflcation of the control.

Referring to the'drawings in detail,.I show an illustrated evaporator comprises a plurality of coils ll arranged in parallel with respect to the flow of air; each coil comprising a plurality of- 3 tubes disposed in a horizontal plane and connected for flow of refrigerant successively through the several tubes from the right-hand side to the left-hand side of the evaporator as shown in the drawing. The evaporator II is part of a mechanical refrigerating system comprising compressors and I8, assumed for convenience to be of equal capacity and driven by electric motors Ila and la, respectively, a condenser I9, a liquid receiver 2| and a thermostatic expanslon valve 22, for controlling the admission of liquid refrigerant to the evaporator. A conduit 23 conveys the compressed refrigerant from the compressors to the condenser, and a conduit 24 conveys the condensed refrigerant from the liquidrecelver to the valve 22. A disair conditioning chamber In containing a refrigerant evaporator ii for cooling! and dehumidifying air for'an enclosure [2. Air withdrawn from the enclosurev is conveyed to the chamber 10 .through a duct l3; and outdoor air tributor fitting 20 and distributor tubes 20' serve to distribute'ithe refrigerant from the valve 22 to'the several coils of the evaporator ii. in this case in equal proportions- A'suction conduit 25 returns'the refrigerant vaporized in the evaporator II to the compressors. Any suitable re-' frigerant may be used, such as dichlodifluoro-- methane.

The thermostatic expansion valve 22 is responsive to the superheat of the va rized refrigerant leaving the evaporator and regulates the admission of liquid refrigerant to the evaporator to maintain said superheat substantially constant.

The valve 22, shown in detail in Fig. 2, has a pressure-responsive diaphragm 26 for actuating the same and a spring 21 biasing the same in.

closing direction. The pressure of the vaporized refrigerant in the suction conduit 25 is conveyed through a tube 28 and imposed on the is conveyed thereto through a duct M. A fan IS controlled in any suitable manner, operates to draw the air'through the 'ducts lt and ll,

across the evaporator ll, and througha duct l6 into the enclosure l2. Suitable dampers may be provided in the several ducts as is well understood in the art. A damper IS in the duct and a damper It in the duct ll are shown by way of example.

The evaporator H, i on the drawings, is of a suitable commercial form and'of the type known as a dry evaporator; that is, the refrigerant'flows at. substantial velocity shown diagrahnmatically through several tubes or turns in- 'serles The 55,

thevaporized refrigerant and the pr diaphragm in valve closing direction. A thermostatic bulb 29 is disposed in contact with the suction conduit 25 or in any suitable heat transfer relation to the vaporized refrigerant therein.

ant, and its pressure is conveyed through a tube 3| and imposed on the expansion valve 22 in valve opening direction., Since the pressure in the bulb 29 is aiunction of the temperature. of

veyed through the tube 28 is a functio of its saturation temperature, the" difference is a measure of the superheat and acts' on the diaphragm' 28 in valve opening direction to maintain the superheat substantially constant. The setting of the spring 21 controls the superheat that the con-" pendent upon the relative capacities of the compressors and chosen so that the portion of the evaporator containing liquid refrigerant is reduced in the same proportion that the compressor capacity is reduced when the compressor I8 is shut down. For the present case, a setting of 40 F. superheat is assumed.

A small electric heating element 32 is disposed adjacent the thermostatic 'bulb 29 for the pur-. pose of selectively raising the temperature of the liquid in the bulb above-the temperature of the refrigerant in the suction conduit to such an extent that the superheat of the latter will be reduced to the usual F. and a greater portion of the evaporator will contain liquid refrigerant.

Control mechanism The control mechanism includes a thermostat T for controlling the cooling action to maintain substantially the desired temperature in the enclosure, a humidostat H exercising a degree of control over the dehumidifying action so as to maintain substantially the desired humidity of the air in the enclosure, and a second thermostat T1 for discontinuing dehumidiflcation before such action reduces the temperature to an undesirable extent. These control instruments are made responsive to the condition of the air in the enclosure, as by disposing them within the enclosure. I desire it to be understood that these instruments, which are represented only diagrammatically on the drawings, may be of any suitable form and construction known in the art of instruments and that they may embody any and all features known in the art. For example, they are preferably provided with suitable adjustment for varying the values to which they respond. Also, suitable provision may be made for causing them to operate with a snap action.

Relays 33 and 34 are provided for controlling the supply of electric current from line conductors L1 and L: to the motors Ila-and Ila, respectively. The control mechanism may be supplied with current from line conductorsL: and L4, which may be connected to the sarnefsource as the line conductors L1 and L2. The thermostat T has a set of-contacts 35 adapted to be closed upon in-' crease in temperature of the air in the enclosure l2 to a first predetermined maximum temperature, such as 80 F., and a secondset of contacts 33, adapted to be closed upon increase to a slightly higher predetermined maximum temperature, such as 82 F., these temperatures representing substantially the temperatures desired to be maintained within the enclosure l2. Thecontacts 35 control a circuit 31 for the winding of the relay 33. The contacts 36 control a. circuit 38 for thewinding of the relay 3! and a circuit 39 for the heating element 32. The humidostat H has contacts 4| and 42 which are adapted to be closed simultaneously by the humidostat upon increase in the humidity of the air in the enclosure l2 to a predetermined maximum value desired to be maintained thereby,

such as 50% relative humidity. The contacts ll and 42 are arranged in parallel with the

contacts

35 and 36, respectively, and are adapted to supply current to the

circuits

31 and 33, re-

spectively. The humidostat H is further provided with a back contact 33 adapted to break the connection between thev contacts 36 and the circuit 38 when the contacts II and 42 are closed. The purpose of these contacts is to permit the contacts 32 to close the circuit 33 without closing the circuit 39. The thermostat T1 is adapted to open its contacts 44 when the temperature of the air in the enclosure is reduced to a value, for example 78 R, such that further reduction in temperature would cause discomfort, or such that further cooling action would not be desired. These contacts are connected between the line conductor La and the contacts 4| and 42, so that they are adapted to prevent dehumidifying action under control of the humidostat H.

Fig. 1.0peration Assume first that the thermostat T closes its contacts 35 in response to increase in temperature to 80 F. The circuit 31 is completed and energizes the relay 33 to start operation of the motor Na and the compressor II. No current is supplied to the heating element 32, so that the thermostatic bulb 29 responds to the actual temperature of the refrigerant leaving the evaporator ll.

Theair conditioning apparatus now operates in the usual manner of such apparatus, but at one half of full capacity. vaporized refrigerant is compressed by the compressor I1, conveyed through the conduit 23 to the condenser l9, condensed therein, collected in the liquid receiver 2|, and conveyed through the conduit 24 to the thermostatic expansion valve 22. From the latter, it is distributed by the distributor fitting 20 and the distributor tubes 20' to the several coils of the evaporator, in which it serves to cool the air flowing over the evaporator. The

vaporized refrigerant leaving the evaporator coilsis returned to the compressor through the suction conduit 25.

,The thermostatic expansion valve 22 operates, as explained above under the description of this valve, so as to maintain a predetermined degree of superheat of the refrigerant vapor leaving the evaporator, which is assumed to be 40 F., since a no current is supplied to the heating element 32. The setting ,of the thermostatic expansion valve to such a high degree of superheat causes the same to restrict the flow of refrigerant to the evaporator coils, so that a reduced portion of the length of each coil contains liquid refrigerant, the remainder containing vaporized refrigerant which is being superheated to the high 7 If the same degree of superheat were maintainedwhen only one compressoris operating, then the I one compressor in operation would not be able to remove vapor at a sufliciently'high rate to provide a sufliciently low refrigerant temperature in the evaporatorfor dehumidiflcation. By

providing the high superheat, so that only half apparatus is so operating,

, trol ineffec mand for dry bulb temperature reductionisuperfri'gerant, there is maintained a proper relation of compressor capacity to effective evaporator surface, so that a sufliciently low refrigerant pressure and temperature mayrbe maintained. The operation is substantially the same as in conventional practice, except that only half of the compressor capacity and halfcof the evaporator surface are effective. In other words, the evaporator is operating at half capacity.

Upon increase in temperature above 82 F., the thermostat T closes its contacts 36,- thereby closing

circuits

38 and 38. The relay 34 energizes the motor "6 for operating-the compressor l8, and the circuit 39 supplies electric current to the heating element 32. Both compressors are now in operation. At this time, the heat supplied by the heating element 32 to the thermostatic bulb 29, raises the pressure in the latter to such anextent as to indicate a temperature thirty degrees higher than it would indicate if such heat were not supplied, or thirty degrees higher than the temperature of the vaporized refrigerant. The net result is that the thermostatic expansion valveoperates to maintainten degrees of superheatof the refrigerant leaving the evaporator, since the remaining thirty of the forty degrees-required by the thermostatic expansion valve is supplied by the heating element.

The evaporator ll now operates in the conventional manner of such apparatus, such quanas can be completely evaporated and super-'- heated 10 F.

Now assume that the relative humidity of the tity of liquid refrigerant being supplied thereto air in the enclosure l2 rises to50%. The humid- I ostat H closes its contacts 4! and 42 and opens its contacts ll. Also assume that the dry .bulb temperature of the air is below 82 F., the temperature The contacts 35 may be either open or closed. The contacts 4! and 42 energize the

circuits

31 and 38 to cause operation of both compressors, while the open contacts .43 prevent energization of the heating element 32 by the-contacts 42.

, Since the heating element 32 is not energized, the

thermostatic expansion valve operates to maintain-a high degree-of superheat with the result that -a reduced portion of the evaporator is supplied with liquid refrigerant while, at the same at which the contacts 3 are closed.

time, both compressors l1 and llare operating.

It will be seen that the ratio of compressor capacity to effective evaporator surface is greatly increased, so that'a lower pressure and a lower temperature of the refrigerant-in the evaporator are provided.

s eflective evaporator surface cools the airin'con- The reduced temperature of the for example,

invention in which modulating control of the heating element 32 is'provided and in which variable compressor capacity is provided by a two-speed compressor ilb driven by a two-speed motor He. The control for the motor includes relays 33a and Ma which are controlled by circuits 31a and 38a, respectively, and which are adapted to effect such connections between the terminals of the motor "a and the line conductors L, Li and L2, as to effect operation of the motor at low speed and at high speed, respectively. Inasmuch as such connections, spe cifically, form no part of the present invention, and depend upon the particular motor and type of electric current used, they are not described herein, the particular connections shown on the drawing being known in the art as suitable for three phase alternating current motors.

The relay a has contacts 5| adapted to open the connection made by the relay 38 whenever both relays are energized atthe same time, so

that high speed operation is effected at such v time. The relay 34a also has contacts 52in the circuit 39 arranged so that the circuit 39 may be closed only when the relay 34a is energized to effect high speedv operation.

again as examples of first and second predetermined maximum temperatures. The contactor is also adapted to'successively engage the several rheostat contacts ,to decrease the resistance in the circuit 39, upon successive increases in temperature. For example, the first to the fourth contacts (from left to right) may be engaged in response to values of 85,-84, 83 and 82 F., respectively. i v

The humidostat H actuates a contactor arm 59, which isconnected to the line conductor L:

and adapted .to engage a contact segment it connected to the circuit 38a upon' increase in relative humidity above a predetermined value, The contactor 59 is also adapted to successively engage the first to the sixth rheostat contacts 55 (from left 'to right), for increasing the resistance in the circuit, upon increase in relative humidity, to 50, 52, 54, 56, 58 and 60%, respectively.

Fig. 3--Operat ion Assume first that the relative-humidity in the enclosure I2 is 50%, so that the contactor 59 thermostat T closes its contacts 38 while the ment 3! is energized to supply liquid refrigerant then the heating elethereby rendering the humidity responsive on-.-

tive. *In other words,-inaximum deewes the first contact 65. If the temperature is below the cooling apparatus is shut down.

As the temperature increases to 80?, thethermo- I stat T moves the contactor it into engagement with the contact ll, thereby closing the circuit- Ila and energizing the relay 33a. The motor compressor unit then operates at low speed, which speed'may be one-half the full or high speed. As the circuit." is opened by the contacts 52' of the high speed relay'lla. the bulb 2| is not heated, and the effective evaporator surface is reduced. to the minimumvalue, for example, by one half. The apparatus thus opercircuit 35a to energize the high speed relay 34a.

It also engages the fourth contact 54. The relay 34a effects high speed operation of the motor compressor and its contacts 52 close the circuit 33. The maximum amount of current is supplied to the heating element 32 due to the engagement of the contactor 59 with the first contact 55, so that the effective portion of the evaporator is at a maximum. The apparatus now operates in'the same manner as that of Fig. 1, when the contacts 35 are closed, the only difference being that the full compressor capacity is provided by full or high speed of the multi-speed compressor instead of by two compressors.

Next assume that the temperature is below 82, the compressor either being shut down or operating at low speed. As the humidity increases to 52% and 54%, the contactor 59 movesto the second and third contacts 55, but this has no eifect since the circuit 39 is opened by the contacts 52. As the humidity reaches 55%, however,-

the contactor 59 engages the. high speed contact 5| to close the circuit 33a. The energized relay 34a effects high-speed operation of the compressor and also closes the circuit 39. Theheating element 32 is now/ energized, but by a reduced amount of current, due to the fact that two resistance sections are interposed in the circuit, the

usual manner of such apparatus but the pressure and temperature of the refrigerant in the evaporesistance is interposed in the circuit and the effective evaporator surface is reduced to increase the degree of dehumidification. Further increase in relative humidity to 58 or 60 5 percent has no effect, however, since the contactor 55 engages the'fourth contact 54, thereby shunting the fourth and fifth resistance'sections. The reason for this is that-the temperature indicates 'a demand for sensible heat removal greater than that obtained when the fourth and fifth resistance sections are in a circuit.

As the temperature increases further to 83,

84, 85, the additional resistance sections are successively shunted to gradually increase the '15 effective surface, and also gradually reduce the shunted to provide maximum effective evaporator surface.

It will thus be seen that in this embodiment there is provided modulating control of .the eifective evaporator surface in response to a humidity condition, together with modulating control in response to temperature adapted to supersede the humidity responsive control to the extent that the temperature may call for gerater eil'ective evaporator surface than that provided by the humidity responsive control.

Fig. 4

The control scheme shown in Fig. 4 is similar to that shown in Fig. 3 except that two separate rheostats controlledby the thermostat and the contact 59 being in engagement with the third humidostat, respectively, are provided for controlling the circuit 39 and these rheostats are connected in parallel so that the circuit is infiuenced by both temperature and humidity ex- 4o'cept when one or the other causes maximum rator are" onlypartially reduced, so that the degree of dehumidification is increased to a limited extent. As the contactor 59 moves towardv theright and engages the several contacts 55, the resistance is gradually increased and the amount of current supplied to the heating element 32 is gradually decreased. Thus, the thermostatic expansion valve 22 gradually increases the amount of superheat of the vaporized refrigerant, resulting in gradual reduction in temperature and pressure of the refrigerant in the evaporator, and gradual increase of the degree of dehumidification in accordance with the increase in humidity and demand fordehumidification.

, When the temperature is 82 and the contactor engages the high speed contact 58 and the fourth contact 54, there is indicated a demand for cooling greater than that supplied by half speed operation, but yet sumciently moderate to permit some of the cooling effect to be utilized for a'greater degree .of dehumidificatibn. In this case, the effective portion of the evaporator is controlled by the humidostat to a limited extent.

current to-be supplied thereto. In this embodiment, the contactor 55 engages contacts 55a of a rheostat 52 and the contactor 53 engages contacts 55a of a rheostat 53. When each contactor engages a contact other than the first, then each perature or humidity varies the amount of current supplied to the heating element 32 and the rti'on of the evaporator surface that is effective. However, if either contactor engages the first contact, then fullline voltage is supplied to the circuit. so that the maximum portion of the evaporator-surface is eflfective. In this case, the other rheostat is ineffective. The operation of this embodiment is in other respects the same as that of Fig. 3.

While I have shown my invention in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications 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.

What I claim is: 1. In air cooling and dehumidifying apparatus, the combination of evaporator means comprising a plurality of refrigerant passages arranged 0- in parallel, means for eifecting flow of a stream of airover said evaporator means, a variable speed compressor, condensing means, means operable automatically to eifect operation of the compressor at low speed and to restrict the now of refrigerant to said evaporator means so. that liquid refrigerant extends through a relatively small portion of each of said passages in response to a predetermined temperature and to effect operation of said compressor at high speed andto increase'the flow of refrigerant to said evaporator means so that liquid refrigerant extends through a greater portion of each of said passages in response to a higher predetermined temperature.

2. In air cooling and dehumidifying apparatus, the combination of evaporator means, means for effecting flow of a stream of air over said evaporator means, compressor means of variable capacity, condensing means, and means operable automatically to eflect operation of the compressor means at full capacity and to. supply a maximum portion of the evaporator means with liquid refrigerant in response to a predetermined maximum temperature and independently of humidity, to effect operation of the compressor means at reduced capacity and to supply a reduced portion of the evaporatormeans with liquid refrigerant in response to a relatively low humidity and a temperature intermediate said predetermined maximum temperature and a predetermined minimum temperature, and to effect operation of the compressor means at full capacity and to supply a reduced portion of the evaporator means with liquid refrigerant in response to a relatively high humidity and a temperature intermediate said predetermined maximum temperature and a predetermined minimum temperature.

tus, the combination of evaporator means, means for efiecting flow of a stream of air over said evaporator means, compressor means of variable capacity, condensing means, and means operable automatically to effect operation of the compressor means at reduced capacity and to supply a reduced portion of the evaporator means with liquid refrigerant in response to a relatively low humidity and a temperature intermediate-predetermined maximum and minimum values, to effect operation of the compressor means at full capacity in response to either a temperature 3. In air cooling and dehumidifying appara tus, the combination of evaporator means, means for effecting flow of a stream of air over said evaporator means, a multi-speed compressor,

condensing means, and means operable auto- -increased capacity inresponse to matically to effect operation of the compressor at low speed and to supply a relatively small portion of the evaporator means with liquid refrigerant '1 response to a relatively low humidity and a temperature intermediate a predetermined maximum temperature and a predetermined minimumr temperature, to effect operation of-the compressor at high speed and to supply a greater portion of the evaporator means with liquidrefrigerant in response to said predetermined maximum temperature and independently of humidity, and to effect operation of the compressor at high speed and to supply a relatively small portion of the evaporator means with liquid refrigerant in response to a relatively high humidity and a temperature intermediate said predetermined maximum temperatubfi and to a predetermined minimum tempera e.

i 4. In air cooling and dehumidifying apparatus, the combination of evaporator means, means for effecting flow of a stream of air over said evaporator means, compressor means of variable ca.- pacity, condensing means, means operable automatically to eifect operation of the compressor means at reduced capacity and to supply a reduced portion of the evaporator means withliquid in-response to a low humidity condition, to effect operation of the compressor means at T: predetermined maximum value of a humidity condition, andtd vary the portion of the evaporator means supplied with liquid refrigerant gradually-in reabove said predetermined maximum value or a relatively high humidity, and to vary the portion of the evaporator means supplied with liquid refrigerant gradually in response to gradual variations in humidity while said compressor means is operating at full capacity.

6. In air cooling and dehumidifyingapparatus, the combination of evaporator means, variable capacity compressor means and a condenser connected in a refrigerant circuit, means operable automatically to increase and decrease both the portion of the. evaporator means containing liquid refrigerant and the rat-- of fluid translation (by volume) of the compressor means in response to increase and decrease, respectively, in temperature of air, and means operable automatically to increase said rate of fluid translation and thereby also the ratio of said rate of fluid translation to the portion of the evaporator means containing liquid refrigerant in respons to increase in humidity of air. I

7. In air cooling and dehumidifying apparatus,

.the combination of evaporator means, means for effecting flow ofa stream of air over said evaporator means, variable capacity fcompressor means, meansoperable automatically to initiate and terminate operation of the compressorin response to increase above and decrease below a predetermined temperature of air, means for automatically increasing and decreasing both the portion of the evaporator means containing liquid refrigerant and the rate of fluid translation (by volume) of said compressor means in res onse to increase and decrease, respectively, in temperature of air, and means operating automatically to increase and decrease the rate of fluid translation (by volume) and thereby also the ratio of swsaid'rate of. fluid translation to the liquid-containing portion or the evaporator means in response to increase and decrease, respectively, in humidity of air.

8. In air cooling and dehumidifying apparatus, the combination of evaporator means, variable capacity compressor means and a condenser connected in a refrigerant circuit, means operable in response to increase in temperature of air above a first predetermined valuefor effecting operation of the apparatus with a reduced portion of the evaporator means containing liquid refrigerant and the compressor operating at reduced rate of fluid translation (by volume),

- means operable in response to increase in huto gradual variations in the value of said I 5. In air cooling and dehumidifying apparamidity of air for increasing the rate of fluid translation (by volume) of said compressor means and-thereby also the ratio of said rate of fluid translation to the liquid-containing portion ofthe evaporator means, and means operable in response to increase in temperature of air above a second and higher predetermined value for increasing the liquid containing portion of the evaporator means independently of humidity.

9. In an air cooling and dehumidifying apparatus thecombinationof evaporator means,

means for efiecting flow of a stream of air over said evaporator means, compressor means of variable capacity, condensing means, and means operable automatically to efiect operation of the compressor means at reduced capacity and to supply a reduced portion or the evaporator means with liquid refrigerant in response to a relatively low humidity and temperatures intermediate predetermined maximum and minimum'values, to

eflect normally operation of the compressor 10 means at sufliciently high capacity to lower the pressure in the evaporator to a minimum when the temperature rises above a predetermined high value or the humidity becomes relatively high, and to vary the portion of the evaporator means supplied with liquid refrigerant gradually in response to gradual variations in humidity while the compressor means is operating to maintain the pressure in the evaporator at a minimum.

1 LEROY G. HUGGINS.