US2304269A

US2304269A - Air conditioning system

Info

Publication number: US2304269A
Application number: US208088A
Authority: US
Inventors: William L Mcgrath
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1938-05-14
Filing date: 1938-05-14
Publication date: 1942-12-08
Anticipated expiration: 1959-12-08

Description

Dec. s, 1942. w. L. MGGRATH v 2,304,269

AIR CONDITIONING SYSTEM Filed llay 14, 1938 William Lucerna Patented Dec. 8, 1942 AIB. CONDITIONING SYSTEM william r.. McGrath, si. raul, Minn., signor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application may 14, 193s, serial No. zoaoss (c1. sz-i 7 Claims.

This invention relates to an air conditioning system and more particularly to asystem wherein sensible and latent heat is removed from air which is circulated through a space according to the requirements of the space.`

In accordance with my invention air eration system, the air then being circulated through the room or space to be conditioned. A compressor running at constant speed supplies refrigerant to the evaporator coils'and the iiow of refrigerant to each of the coils is controlled by suitable valve means. When the temperature of the space is above a desired value and the humidity is at or below a desired value, refrigerant is supplied to both of the evaporator coils. Should the humidity rise to an undesirable value, the flow of refrigerant to one of the evaporator coils is interrupted with the result that the temperature of the other evaporator coil will be lower than the temperature of the coils when refrigerant is iiowing through both of the coils. This is desirable since less heat must be removed from the air in order to eilect a reduction in temperature of the air than is necessary when dehumidication is required, since in order to reduce the temperature it is necessary only to remove sensible heat from the air whereas when dehumidification is required, both sensible and latent heat must be removed from the air. The coils are so arranged that a'portion of the air passes over one 'coil and another portion of the air passes over the other coil so that when one coil only is being utilized for dehumidiiication some of the air passing through the chamber will by-pass this coil and may be utilized for reheating the air. Means are also 'provided for supplying refrigerant to both of the coils should the temperature in the space `become excessively high regardless of the humidity in the space in order that amaximum amount of sensible cooling may take place. It is therefore an object of my invention to provide a novel control means for the evaporator coils of a refrigeration system wherein these coils are used to control the temperature andhumidity conditions within a space to be conditioned.

Other yobjectswill become apparent-upon a study of the specification, claims, and appended drawing, the single figure of which illustrates diagrammaticallyrone form of my invention.

Referring more particularly to the drawing, an air conditioning chamber, is represented by the reference character I0. .This chamber may include a fresh air inlet a return air inlet I2,

is circulated over a pair of evaporator coils of a refrigfor circulating air through the chamber I0 and a space I6 to be conditioned. Dampers |1 and il may be provided in the fresh and return air inlets, respectively, for controlling the proportions of fresh and return air admitted to the chamber I0. These dampers may be manually operated or automatically operated in any suitable manner.

Mounted within the chamber I0 and transversely arranged with respect to one another are a pair of evaporators and 2|. A compressor 22 driven by a motor 23 is provided for supplying refrigerant to the evaporator coils 2D and 2|. The high pressure side of the compressor 22 is connected by means of a pipe 26 with a condenser 21. A pipe 28 connected to the outlet of the condenser 21 leads the refrigerant to a pair of valves 30 and 3|. The outlet of valve 30 communicates with the inlet of the evaporator 20 by means of a pipe 33 and a second pipe 34 leads refrigerant from the outlet of valve 3| to the inthe outlets of evaporators 20 and 2|, respectivean outlet I3, and a 4fan I4 driven by a motor 65 ly, and communicate with a pipe 42 leading to the inlet of the compressor 22. In the operation of the refrigerating apparatus the refrigerant is compressed by the compressor 22, is condensed b3 the condenser 21, and then iiows into the coils 2|| and 2| providing the valves 22 and 3| are open, where the refrigerant is evaporated, the flow of 4refrigerant into the evaporators also being controlled by the `expansion valves, the refrigerant being evaporated inthe evaporators and absorbing heat from the air passing thereover and the evaporated refrigerant then flowing back to the compressor 22.

For controlling the operation of the `compressor I have illustrated a suction pressure controller 45. This controller may include an expansible bellows 45 connected by means of a pipe 41 to the pipe 42 leading to the inlet of the compresser. A lever 45 pivoted at 45 is biased by means of a spring 5|! into engagement with the upper portion' of the bellows. Lever 48 carries a mercury switch 52 of conventional construction and when the pressure on the suction side of the compressor drops to a low enough value, the bellows 45 contracts and a lever 4l is moved under Line wires 53 and 54 may be connected to a suit- The ilow of vrefrigerant being of any conventional y following circuit: from` conductors 56, mercury f motor 23, and conductor moves across the potentiometer justable resistance ance Y 661s connected by able source of power (not shown) and are provided for supplying` energyto the motor 23 as well as to the positioning means for the valves 36 and 3| as will be henceforth explained. Power is supplied to the motor 23 when the suction pressure onvthe suction side of the compressor is above a predetermined low value through the the line wire 53 through switch 52, conductor 51, 56 to the line 56. It will nowbe clear that when the'suction pressure drops to a low enough value this circuit to the motor 23 will be interrupted by the contraction of the bellows 46. Y

The positions oi valves 36 and 3| may be controlled by suitable means 66 and 6| which may be in the form of solenoids having an armature suitably connected to the valves. Energization of the solenoids causes the valves to open positions and upon deenergization of the solenoids the valves may be moved to closed positions under the influence 'oi' gravity or a suitable biasing means (not shown).

Mounted within the space to be conditioned is a thermostat indicated generally by the reference character 66. This thermostat mayinclude a bimetallic element 65 and an arm 66 carried thereby and engaging a resistance 61 across which the arm 66 sweeps in response to variations in temperature in the space |6, the arm moving to the rightin response to an increase in temperature and to the left upon a decrease in temperature. 'Ihe l.arm 66 and resistance 61 form a control potentiometer i'or a motor 68. This motor may be a proportioning motor of the type illustrated in Patent No. 2,028,110 issued to D. G. Taylor on January 14, 1936. '

Ihe terminals

66 and 16 of the motor are connected t0 the extremities oi' resistance 61 by means of conductors 1|' and 12, respectively. The terminal 16 is connected to the arm 66 of the thermostat 66 by means of conductors 13, '|6 and the center tapped resistance 15. Power is supplied to the motor by means oi.' wires 18 and 19 connected to a suitable source oi.' power will be v*understoodA upon a study of the above mentioned Taylor' patent that as the arm 66 61, the shaft 86 (not shown). It

to be moved Y l the arm 66 will have to move to A upon movement of the control range of the arm 66 will be shifted to wise'the cam |6| operates a switch arm driven by the motor 68 will rotate an amount i which is proportional to the extent oi'movement.

of the arm 66 with the resistance 61.

Also connected to the center terminals 16 of the motor 68 by' means of conductors 13, 82, ad-

83, and .conductor 6 6 is the control arm 65 oi' a second potentiometer. The

A arm 65 forms one arm 'of a bell crank lever pivoted at 66, the other arm 81vthereoi being biased by mea oi' spring 68 with of the ows 69. The bellows 86 is connected by means of a capillary tube 96 toa bulb 8|, the tube, bulb, and bellows being lled with a suitable volatile iluid. The bulb 6| may be positioned outdoors so that the bellows 86 will expand and contract in' response to variations in outdoor temperature. It will be apparent that as the bellows expands and contracts the ann'65 will be caused to move over the resistance 66. Upon an increase in outdoor temperature the arm 65 will moveY to the of conductors 86 and 1| with the terminal 66 oi the motor 68 and the opposite end of the resistmeans of conductors the upper portion' vclockwise direction arm Vther movement of the arm 66 to arm |66 will b'e moved into engagement with si and 12 with the motor terminal 1o. ii; win now be seen that the potentiometers 66 and 61 are connected in parallel to the motor cause movement of the shaft 86 of the motor 66.

By reason of the adjustable resistance 83 interposed in the circuit to the arm'85 this arm will have less effect on the motor for a given movearm 85 with respect to resistance 66 has theeilect of shifting the control range of the arm 66 with respect to the resistance 61 arm 85 moves to the right for example in respouse to anV increase in outdoor the right in order to cause the motor to return position so that the control range of will move to the right in response to a movement oi the arm 85 tothe right and likewise arm 85 to the left the the arm 66 the left. The provision oi the-center tapped resistance insures that the control range X of the arm 66 will have the same magnitude regardless of the position of this control. range. k

Carried by the shaft 86 are a pair of cams |66 and |6|. Operated by the cam |66 is a switch arm |62 which engages a iixed contact |63 upon movement of the cam to a position wherein the arm |62 is moved upwardly. Like- |66 which cooperates with a xed contact |65. These cams are so arranged that as the cams rotate in a |62 willilrst be moved into engagement with the contact |66 and subsequently the arm 66 will be moved into engagement with the contact |615. As the arm 66 moves towards the right the cams |66 and 6| are rotated in a clockwise direction by the motor 66 through an amount which is proportional to this arm. As the arm 66 movestoward the right in response to an increase in .the temperature of the space the arm |62 will first be moved by the cam '|66 ment with the switch contact |63 into engagethe right the the iixed contact |65. 'I'he temperatures at which the arms engage their respective contacts will depend upon the position of the control range X of the arm 66 oi' thermostat 66 and since this in turn depends upon the outdoor temperature it will be seen that as the-outdoor temperature rises the temperature at which the arms engage their respective contacts will be corre- 4 Spondinsly higher.

Also moimted within the space is is a humidity responsive device 6 which may be of any suitable construction and is shown as comprising a humidity responsive element lH-iixed at one end as at 2 and h'aving its opposite end connected to a lever ||3 pivoted at ||6 and biased upwardly by means vfiof'a spring H5. Carried by the lever |8 is a mercury switch |26, this switch including contacts |2|, |22, |23, and |26 and a mercury element |25. When the humidityis low the switch will be tilted in the position illustrated and 68 and accordingly movement of either arm or 66 with respect to the corresponding resistances will so that as the temperature Y to its initial 2,304,269 comme m and m wm be connected by 'me mercury element |20. Upon an increase in relative humidity the element will expand and orator coil, so that the air being circulatedV through the chamber I is not cooled thereby. 1

Should now the temperature inthe space increase to a high enough value, the arm |02 will be moved by cam |00 into engagement with' contact |00 since the movement of arm 00 of thermostat 00 to the right in response to an increase in temperature will cause shaft 00 to rotate the cam |00 in a-clockwise direction. The solenoids 00 and 0| will now be energized as follows, it being assumed that the humidity in the space has not risen to a sufllciently high valuel to tilt the switch |20 in the opposite direction. Current ilow-s through' the solenoid 00 as follows: from line 00 through conductor |00,v contact |00, switch arm |02, conductor |0|, contacts |20 and |20 of switch |20, conductors |00, |00 to the solenoid 00 and conductors |00 and |01 to the line 00. Current iiows through the solenoid 6| as follows: from line 00 through conductor |00, contact |00, switch arm |02, conductor |00, solenoid 0|, and conductors |00 and |01 to. the line 00.l Thus upon a rise in temperature to a certain value both valves 00 and 0| are open providing the humidity in the space is relatively low so that refrigerant is now supplied under the control of the expansion valves 00A and 01 to the evaporatcrs 20 and 2| Vwhereby a reduction in' temperature of the air passing through the chamber l0 is effected.

Assume now that the temperature is high and that the humidity in thespace reaches an undesirable value and that switch |20 is tilted in the opposite direction wherein the circuit through contacts |20 and |20 are broken and contacts |2| and |22 are bridged by the mercury element |20.

If the temperature in the space has not risen to such a high value that arm |00 has moved into engagement with contact |00, the aforedescrlbed circuit to the solenoid 00 is' interrupted and this solenoid' is therefore deenergized thus causing the valve 00 to be closed. Refrigerant nowilcws only arm |00, conductor |00, solenoid 60, and conductors |00 and |01 to the line wire 00. Both solenoids are now energized so that refrigerant is again supplied to both the evaporators and 2| and more sensible cooling in proportion to latent cooling oi the air is efiected sok that the temperature of the air will more rapidly be reduced to the desired value.

Assume now that the temperature of the air is at a desirable value so that both switch arms |02 l and |00 are out of engagement with their respective contacts but the humidity of the air rises to an excessive value so that contacts |2| and |22 of the switch |20 are bridged by th'e mercury element |20. Current now ilows through the solenoid 0| as follows: the line wire 00 through conductors |00,` |00, |00, contacts |2| and |22 of the switch |20, conductors |0|, |00, solenoid 0|, and conductors |09 and |01 to the line wire 00. The evaporator coll |2| is now available for dehumidification of the air although n sensible cooling is at the time required.

4When coil 2| is being usedfor dehumidicaf tion the temperature of the air leaving the outlet I0 may be'so low as to reduce the temperature of the air within the s/pace I0 below a desirable value. A coil |00 is accordingly placed downstream from the evaporators 20 and 2| and a suitable heating medium is supplied to this coil under the control of valve |0I. The stem |02 of the valve |0| may be connected by means of a link |00 to the arm |00 operated by a motor |00 Awhich may be a proportioning motor similar to the motor 00. The operation of this motor is l controlled by a thermostat |10 located in the space I0. This thermostat may be similar in construction to thejthermostat 00 and may include bimetallic element '|1| carrying an arm |12 for movement therewith over resistance |10, the arm |12 and resistance |10 forming the control potentiometer for the motor |00. Terminals `|10 and |10`of the motor are connected by means of conductors |10 and. |11 to the opposite ends of the resistance |10 and the terminal |10 is connected by means of conductor |10 to the arm |12 through the bimetallic element |1|. Wires |00 and |0| are provided to supply power to the motor |00. When the temperature of the air is at a high enough value the arm |12 o! the 50 thermostat |10 will be at the extreme right end through the evaporator coil 2 thus causing areduction in the suction pressure in the refrigeration system and therefore a reduction in temperature of the coil 2|. The greater proportion of the Heat that is removed from the air is now in the form of latent heat so'that the 1temperature and humidity in the space are both reduced. Some of the air passig through the chamber I0 will of course pass over the coil 20 and will not come into contact l,with the coil 2| so that only a relatively small proportion oi the air is cooled by the evaporators and the air bay-passing theA coil 2| may be utilized to reheat the air which is cooled and dehumidied by the coil 2|'.

Should now the temperature of the air increase l to an excessive degree while the humidity in the space is relatively high, the arm |00 will be moved by the cam |0| into engagement with the contact |00 thus again energizing the solenoid 00 through the following circuit: from the line wire 00 vthrough conductors |00, |00, `|0|, contact |00,

of resistance |10, and the valve |0| will be closed by the motor |00. Should thetemperature in the space I0 fall below a desired value, arm |12 will move toward the right over the resistance |10 thus causing operation of the motor |00 and opening of the valve |0| an amount proportional to the reduction in temperature below the desired value. In this manner whenever the temperature ci the air is lowered below the desired value in order to dehumidify the air or for any other reason, the temperature of the air will be again raised by means of ,the coil |00 to the proper value. E E

, It will now be seen that with my system that when the humidity o! the air is sunlci'ently low.

and when the temperature is higher than desirable, refrigerant is supplied to both evaporators 20 and 2|- Should the humidity become excessive, only one evaporator vis used and the temperature in that evaporator is accordingly reduced -so that dehumidincation of the airas well as sensible cooling will take place. Upon excessive temperature conditions refrigerant will be supplied to both coils regardless of the hu- 70 midity in the space in order to secure maximum perature so that as the outdoor pressure is above a n ltion system including `moving sensible and latent heat from the air t between said latent heat from air to pair cooling of the air. Also in case the humidity is high and the temperature is at the proper value, refrigerant will be supplied to one oi thecolls in order to secure dehumidiiication and the all'. if'necessary, will be reheated by means ol.' the coil |60. The temperature which will be maintained in the space will .be compensated by the controller 89 which responds to the outside temtemperature rises a higher indoor temperature will be maintained in order to secureproper conditions of comfort within the space. If desired however this outdoor temperature compensator may be omitted should it be desirable to maintain the same conditions within the space at all times regardless of the outdoor temperature. Thecompressor 22 will be controlled by the suction pressure and will continue to operate as long as the suction predetermined value.

Having described the preferred form of -my invention, many modincations may become apparentto those skilled in the art and it should therefore be understood that my invention is limited only by the scope o1 the appended claims.

I claim as my invention:

1. In an air conditioning system, a refrigeraevaporator means forV rebe conditioned, meam for causinga flow of refrigerant throughsaid evaporator means, means for circulating air past said evaporator ,means and through a space to be conditioned, dow con trol means for selectively controlling ilow of refrigerant through a portion oi' or through all of said evaporator means or preventing ilow of refrigerant through any ofV said evaporator means, and means in control ofsald flow control means. said last named means comprising means responsive to the temperature and humidity of.

said vspace for controlling said now control'means in a manner to prevent iiow of refrigerant to said evaporator means when the space temperature and space humidity ilowof refrigerant through all of said evaporator means when the space temperature increases to a first predetermined value and thespace humidity is low, for permitting now of refrigerant .through a portion only of said evaporator means whenever the space humidity rises to a predetermined value when said space temperature is predetermined value and a higher value, and for permitting ilow oi' refrigerant to all of said evaporator means regardless of space humidity when the space temperature rises to said higher predetermined value.

2. In an air conditioning system, a refrigeration system including are both low, for permitting `and. humidity is low,

erant into the other evaporator, and temperature and humidity responsive means for controlling said iii-st and second valves in a manner to .close both valves when space temperature and humidity are at low values, to open both valves -when space temperature is is at said intermediate high, and to open both when space temperature value and humidity is valves regardless of humidity when space temperature rises to a high value.

4. In an air conditioning system, a refrigeration system inclu compressor means and a pair oi' evaporators or removing sensible and latent heat from air-to be conditioned,l means for circulating air past said evaporators to a space to be conditioned, a rst valve` for controlling the flow of refrigerant into one evaporator, a second valve for controlling the flow of refrigerant into the other evaporator, temperature and humidity responsive means for controlling said rst and second valves in a manner to close both valves when space temperature and humidity are at low values, to open both valves when space tempera-V ture is at said intermediate value and humidityis low, to open only one valve when space temperature is at an intermediate value and humidity is high, and to open botlivalves regardless of humiditywhen space temperature rises to a high value, and a suction pressure controller for start-v ing said compressor vmeans when the suction pressure rises to a predetermined value and forstopping thecompressor means'when the suction pressure falls to a Vpredetermined lower value. Y

5. In an air conditioning system, a refrigeracompressor means and a pair of evaporators for removing sensibleV and latent heat from air to be conditioned, a first valve for controlling theilow of refrigerant into Y one evaporator, aA second valve for controlling v the flow of refrigerant into the other evaporator,

tion system including compressor means and a pair of evaporators for be conditioned, means for said evaporators to a space a ilrst valve for controlling circulating all' Past to be conditioned,

the flow of refrigerant into one evaporator, a'

removing sensible andv humidity responsive means for controlling atan.

and humidity is high, and tofirst and second valves,

humidity responsive means-for actuating saidboth of said valves when toa rst value and Said.

perature,

vond circuit .means with refrigerant, each means for circulating air past said evaporators to a space to be conditioned, flrst and second switches actuated in sequence upon rising tema humidity actuated switch, and electrical connections between said switchesand said valves for placing said switches in control of the Same, said electrical connections forming a flrst circuit means controlled by said ilrsttemperature actuated switch switch `Jfor opening`\ controlled by said first and second temperature actuated switches for caus-- said valves independently of said humidity actuated switch.

6. An air conditioning system comprising, in combination, a pair ofevaporators for removing latent and sensible heat from said air, compresser means for supplying said evaporatorsof said evaporators having a constant superheat expansion valve at the inlet thereof, a rst v alve controlling the flowof refrigerant into one of said evaporators, a second valve controlling the flow of refrigerant into the other of said evaporators, control means for said and temperature and control means to open the temperature rises at an intermediate value to open only one valve'A and said humidity actuated both of said valves, and a sechumidity is low, to close one of said valves when said humidity is high as long as the temperature is below a second value higher than said iirst value, and to reopen said one valve regardless of humidity when the temperature reaches said second value. y

'7. An air conditioning system comprising in combination, a pair of evaporators for removing latent and sensibleheat from said air, compressor means for supplying said evaporators with refrigerant, each of said evaporators having a constant superheat expansion valve at the inlet thereof, a first valve controlling the Vflow of refrigerant into one of said evaporators, a second valve controlling the ow of refrigerant into the other of said evaporators, control means for said iirst and second valves, and ltemperature and humidity responsive means for actuating said control means to open one of said valves when the humidity reaches a high value, and to open both of said valves when the temperature rises to a iirst value and said humidity is low, to close one of said valves when said humidity is high as long as the temperature is below a second value higher than said first value, and to reopen said one valve regardless of humidity when the temperature reaches said second value.

WILLIAM L. MCGRATH.