US2657543A

US2657543A - Method and apparatus for maintaining temperature and humidity constant

Info

Publication number: US2657543A
Application number: US53394A
Authority: US
Inventors: Eichmann Theophil
Original assignee: GEORGE B SCARLETT
Current assignee: GEORGE B SCARLETT
Priority date: 1948-10-08
Filing date: 1948-10-08
Publication date: 1953-11-03
Anticipated expiration: 1970-11-03

Description

Nov. 3, 1953 T. EICHMANN 2,657,543

METHOD AND APPARATUS FOR MAINTAINING TEMPERATURE AND HUMIDITY CQNSTANT Filed Oct. 8, 1948 N I awe/Mm:

m (BAR ATTORNEYJ Patented Nov. 3, 1953 METHOD AND APPARATUS FOR MAINTAIN- ING TEMPERATURE AND HUMIDITY CON- STANT Theophil Eichmann, Berne, Switzerland, assignor to George B. Scarlett, Kennett Square, Chester County, Pa.

Application October 8, 1948, Serial No. 53,394

I 7 Claims.

1 This invention relates to methods and apparams for maintaining temperature and humidity constant; and the nature and objects of the invention will be readily recognized and understood by those skilled in the arts involved in the light of the following explanation of the preferred method and the steps thereof of my invention and of the detailed description and explanation of the accompanying drawing illustrating what I now consider to be a preferred improvement and arrangement of apparatus of my invention capable of operation to carry out and perform such preferred method.

This invention relates particularly to a method of .keeping the temperature and the humidity constant in the air of a cold chamber by means of a refrigerating machine. The method according to the invention consists in the feature that the refrigerating machine, as well as an aircooled condenser and a water-cooled condenser connected in parallel therewith, are controlled by a thermostat and a hygrostat in such a way that the evaporator and the water-cooled condenser are set in operation by the thermostat, and, after attainment of a predetermined temperature and release by the thermostat, the evaporator and the air-cooled condenser are set in operation by the hygrostat, until the thermostat interrupts the action of the hygrostat and switches on the cooling operation again. insofar as the predetermined value of the humidity of the air has not already been reached previously by the hygrostat.

Apparatus of my invention for carrying out the method thereof is illustrated more or less schematically by Way of example in the accompanying drawing.

Referring to the drawing, the apparatus of the example includes an air-cooled condenser I in a passage l5, and a water cooled condenser 2 connected in parallel therewith by the hot, compressed gas supply line la and the condensate return line lb. An evaporator 3 is, in this instance, located in the passage l5 and is connected with the suction intake side of a compressor 4. by the suction or return gas line 3a. As will be understood by those skilled in the art, both condenser I and evaporator 3 are in heat exchange relation with the air of the chill room. The compressed gas discharge or pressure line 2a connects the discharge side of compressor 4 with condensing coil 2b of condenser 2. The compressed gas line la to the air cooled condenser is connected to and receives hot, compressed gases fromv the discharge line 2a from the compressor 4 just in advance of the condenser 2.

The water cooled condenser 2 is Supplied with cooling water by a supply line la, and water is discharged from the condenser by the discharge line 1b, in the usual manner of the conventional water cooled condensers familiar to the art. The cooling evaporator 3 receives condensed refrigerant for expansion therein, through a con densate supply line 31) which has its intake end in a condensate reservoir or tank IS, in accord ance with conventional practice. Condensed refrigerant is supplied to the reservoir l6 by a supply line 2c connected to the discharge end of condensing coil 2b and discharging into reservoir- IS. The condensate line lb from the air cooled condenser I is, in this instance, connected into line 20 for the return of condensate from air cooled condenser l to the reservoir I6. I An electricallycontrolled solenoid type valve 5 is connected into the condensate line 20 between condenser 2 and the condensate reservoir H; for controlling flow of condensate through this line. An electrically controlled solenoid type of valve 5 is connected into the condensate return line lb between the air cooled condenser l and the reservoir It for opening or shutting ofl this line to flow of condensate therethrough.

In the cooling operation or cycle of the apparatus, the cooled vapors are sucked out of the evaporator 3 by compressor 4 through the vapor return line 3a, compressed by the compressor, condensed in the condenser 2 and then returned to the evaporator 3 through line 20, reservoir l6 and line 3b, all in accordance with the usual refrigerating or cooling cycle familiar in the art. In the operation of the refrigerating cycle the valve 5 in line 20 is open while the valve 6 in line lb from the air cooled condenser l is closed. In the heatpumping or air conditioning operation of the apparatus, the valve 6 is opened while the valve 5 is in a partially closed or throttled position, so that the hot, compressed gases from the compressor 4 are discharged through line lav through the air cooled condenser l and returned as condensate through line lb to the reservoir IS.

The compressor 4 is power driven by an electric motor I! in the usual manner, this motor being in this instance supplied with operating current through a three-phase power circuit comprised by the circuit lines R-S-T. In this circuit there is located and connected the usual motor controlling and protecting contactor unit l8, as will be familiar to those skilled in the art. The operationv of the compressor and the operation and control of the solenoid valves 5 and 6 is effected automatically through an electrical control system which includes a thermostat 8 associated with a control or master relay 9, and a hygrostat I2 associated with a control relay II. The thermostat 8 and the hygrostat I2 are, of course, located in the chill room.

The thermostat .8, which as shown schematically may be of any of the well-known mercury tube types, is connected with the power circuit R-S-T by the controlling circuit line 8a, and is connected to the master relay 9 by a circuit line 8b for control of the cooling cycle. The master relay controls a circuit therefrom to the solenoid valve 5 which includes the circuit line 541. The relay 5 also includes and controls a circuit for effecting operation of the contactor I8 for controlling operation of the compressor 4 by the motor I'I, such circuit being constituted by the circuit line IBa. And the relay 9 also includes a controlling circuit for operating the fans II]. This latter circuit is constituted by a circuit line Ina.

The relay II is conditioned for control by the hygrostat I2 only when the temperature of the chill room has been lowered to a predetermined temperature by operation of compressor 4, condenser Z and evaporator 3 as a conventional cooling or refrigerating machine. When, however, the predetermined temperature controlled by the thermostat 8 is reached, the functioning of the thermostat eifects operation of control relay II for control by the hygrostat I2 of the predetermined humidity conditions in the chill room.

The relay II has a control circuit In therethrough in connection with hygrostat I2 and thermostat 8 including a circuit line I2b from relay II to the neutral lead Illb. Relay II is supplied with current by a circuit line I lb. The relay I I controls a circuit therethrough which connects by a circuit line I I with the circuit Illa to the fan Ill. The relay II also includes and controls a circuit therethrough which connects by a circuit line I8b with the circuit I8a to motor controlling contactor unit I8. The relay I! also includes and controls an actuating circuit through the solenoid operated valve 6 in the condensate return line II) from the air cooled condenser I. This circuit includes a circuit line 6a from relay I I to one side of solenoid valve 6 and to circuit line B?) from the other side of the solenoid to the neutral lead I 0b.

The system may include an electric motor driven circulating fan or fans I!) included in a circuit constituted by a circuit line Illa between relay 9 and one side of the motors Ill, and a connection from the opposite side of the motor of a fan III to the neutral lead IIlb.

An automatic pressure controlled valve 1 is connected in the cooling water supply line Ia to the condenser 2 for controlling flow through that line. This valve 1 is controlled by a pressure line To from compressor 4 in a manner such that upon a predetermined fall of pressure in compressor 4 the valve I is actuated to close lines Ia and thus stop consumption of water by the water cooled condenser 2, while at another predetermined higher pressure the valve is actuated to open position for supply of cooling water to the condenser in the normal refrigerating operation.

The air cooled condenser or air heater I is provided of such relatively large dimensions that during the operation of the system to include the heat pumping cycle the liquefying or condensing temperature is preferably 5 C. lower than the temperature in the water cooled condenser 2, As a result of this fall of pressure resulting from the lower condensing temperature as referred to above, the water valve I is caused to operate to close the cooling water supply line I to the condenser 2. And in addition, because of this fall of final pressure, the power required by the compressor is also reduced.

With the system of the invention functioning solely as a refrigerating or cooling cycle to lower the temperature in the chill room or other space to be refrigerated, the thermostat 8 has functioned to actuate the master relay 9 to condition the various circuits controlled thereby to cause operation of the compressor 4, fan or fans It! and the electrical shut-off valve 5, so that, liquid refrigerant is forced from condenser 2 through line 20, reservoir I6 and line 3b into the evaporator 3. The cold evaporation gases are then drawn back through line 3a to the suction side of compressor 4 for recycling, in the usual manner. In the system when. so operated, valve 5 is open while the valve I5 in the condensate return line I b from the air cooled condenser I is closed, thus effectively shutting off operation of that condenser to function as a heating element.

When, however, the predetermined temperature has been reached in the cold room, the thermostat 8 switches off the master relay 9 and, through the circuits as above described. conditions the control relay II for operation by the hygrostat I 2 upon an increase in the humidity of the cold room. When the predetermined humidity is reached and hygrostat I2 effects operation of control relay I I, the system is then caused to function partially as a heat pump to condition of the air in the cold room. The switching on of relay II by hygrostat I2 closes the circuit 6a6b through solenoid valve 6 to cause that valve to open. At the same time valve 5 has been caused to close or partially close, so that hot, compressed gases then circulate through line Ia to air cooled condenser I, and through that condenser to heat the air therein, with the resulting condensate being returned back to reservoir I6 through the return line Ib. During such operations, the refrigerating machine functions partly as a heat pump and cooperates with the air cooled condenser for air heater I, so that in the example apparatus hereof, the air in heat exchange relation with the evaporator 3 is first cooled through about 3 C, and is then warmed through about 5 C. in the succeeding air heater I which then functions as the condenser of a heat pump.

The change over from cooling operation solely of the system to an operation in which the system functions also as a heat pump, and conversely, is effected by means of the master relay 9 and control relay II. These relays are so controlled by the thermostat 8 and hygrostat I2 that the predetermined temperature has to be reached in the chill room before the thermostat relay 9 sets up the relay I I for control by the hygrostat. Hence, only when the predetermined temperature for which the thermostat 8 has been adjusted is reached in the chill room are the circuits for setting up the heat pumping function conditioned for control by hygrostat. In this manner, any undesirable raising of the temperature by the heat pump is prevented. The thermostat 8 controlling relay 9 effects operation of the system as a refrigerating cycle while the hygrostat I2 controls relay II effecting operation of the heat pump cycle. The change over from operation of the apparatus to perform the refrigerating cycle, to operation of the apparatus to include the heat pump cycle, is effected by the automatic changing over of the two condensers I and 2 which are connected in parallel. The electrical control shut off valves 5 and 6 are automatically operated to function for interrupting the condensation both in the water cooled condenser 2 and in the air cooled condenser], these valves being opened and closed by the relays 9 and II which are in turn controlled, respectively, by the thermostat 8 and the hygrostat 12.

In refrigerating plants comprising a plurality of chill rooms it may be desirable to perform an air-conditioning only in one or several of these rooms. In this case, a spring-loaded check valve may be used instead of the electrical shut-off valve 5. Thereby will be obtained an adjustable increase of pressure in the Water-cooled condenser 2. Due to thisoverpressure and by opening the valve 6 during the air-conditioning such a quantity of gas will be conducted to the air heater I, which suffices, when being condensed, for radiating an amount of heat to the room which is needed to eliminate the refrigerating output of the air-cooler 3 partially or completely.

The time of operation of a refrigerating machine is normally determined by the demand for cold of the chambers connected thereto. The time of operating amounts, if importance is attached to correct humidity of the air, to from 12 to 14 hours per day. With purely thermostatic control, therefore, the idle intervals are about equal in length to the cooling periods.

During the colder season, and particularly in winter, the demand for cold from the cooling plant falls off considerably, as the temperature dropis smaller, corresponding to the smaller difference between the temperature in the chill room and that in the surroundings. In extreme falls of the outside temperature the case may even arise that with known methods and cooling installations no cooling at all by tile refrigerating machine takes place. The shorter the running time of the machine, however, the moister does the chill room become, because the removal of moisture from the air in the room only takes place during the cooling. Particularly in a meat-storage room, in consequence of the withdrawal of moisture from the stored contents, after even two hours interruption of the cooling the relative humidity of the air in the chill room will rise to over 90 per cent; that is, it will reach a value at which the meat deteriorates owing to the formation of mould and the decomposition of protein. The storage of meat for a longer period is only feasible with a constant humidity of the air in the room of at most 75 per cent, that is, a humidity at which the formation of mould is precluded. In recent cooling installations an attempt has therefore been made, by artificially heating the air of the room during the colder season, to replace the absent heat transmission through the insulation from outside, and thereby artificially increase the running time of the refrigerating machine to that value which ensures the air-drying associated therewith. With fully automatic electrical refrigerating installations, electrical energy is as a rule adopted as the source of heat, that is to say, a source of heat which is rather expensive in operation. Thus for example a cooling plant with a refrigerating capacity of 10,000 calories per hour requires a heater of at least 6 kilowatts connected load. on an annual average, such heating is switched on for from 5 to 6 hours per day. For such an installation, therefore, the current consumption per year amounts to about 11,000 kilowatt-hours. A fur-1 ther disadvantage of the electrical heating of chill rooms consists in the fact that in the vicinity of the heater, in consequence of the unavoidable thermal radiation, the material that is being cooled is adversely affected. There is also the risk that the cooling elements may thaw off during the heating period, a disadvantage that should be obviated, since with the thawing is associated a further increase in the humidity of the air in the room. In the case of electrically heated chill rooms the refrigerating machine is controlled, or in other words switched on and off, by the thermostat, and the heating by the hygrostat. This control is associated with serious disadvantages, because the heating, switched on by means of a hygrostat, first has to heat up the air from 1 to 2 degrees centigrade before thether mostat has overcome its own difference and can switch on the refrigerating plant. During the heating-up time the humidity, which has in any case been raised, is thereby still further increased. Conversely, notwithstanding the relative moisture content of the air having been reached, the air-drying will still continue until the heat ac cumulated in the heater is discharged. In both cases, therefore, an over-control is effected in respect of air-drying and moistening. Great fluetuations in the humidity of the air are however just as injurious as too high or toolow a moisture content.

The method described enables the said disadvantages of the known cooling devices of fully automatic electrical refrigerating installations to be eliminated; the temperature and humidity to be maintained exactly at the adjusted value without fluctuations; and the economy of the plant to be improved by from 30 to per cent.

What I claim is:

1. A system for maintaining constant the tem perature and the humidity of a space to be conditioned comprising, in combination, a refrigerating machine including, a refrigerant compressor, a liquid-cooled condenser, and a, refrigerant evaporator in heat transfer relation with the space to be conditioned; an air-cooled condenser in heat exchange relation with the space to be conditioned and being connected in parallel with said liquid-cooled condenser; means for controlling the discharge of condensed refrigerant from said liquid-cooled condenser; means for cutting in and rendering active said air-cooled condenser to cause said compressor to function as a heat pump with said air-cooled condenser; temperature control means in the space to be conditioned in operative relation with said means for cutting out said liquid-cooled condenser; and humidity controlled means in the space to be conditioned in operative association with said means for cutting in said air-cooled condenser.

2. A system for maintaining substantially constant the temperature and the humidity of a space to be air conditioned, comprising, in combination, a refrigerating machine including a refrigerant compressor, a, liquid-cooled condenser, a refrigerant evaporator in heat exchange relation with the space to be conditioned, and refrigerant lines between and connecting said compressor, condenser and evaporator; an aircooled' condenser in heat exchange relation with the space to be conditioned; refrigerant lines connecting said air-cooled condenser directly with said compressor for supplying hot, compressed refrigerant gas to said condenser; means operable for controlling the operation of said I liquid-cooled condenser; a thermostat in the space to be air-conditioned for effecting the operation of said means for controlling the liquidcooled condenser; means for cutting in and rendering active said air cooled condenser to cause said compressor to supply hot compressed gases thereto and for cutting out and rendering inactive said air-cooled condenser; an hygrostat in the space to be conditioned for controlling said means for cutting in and cutting out said aircooled condenser; and said thermostat being operatively connected with said hygrostat for rendering the latter effective for controlling said means for cutting in and cutting out said aircooled condenser only when said thermostat has effected operation of the means for controlling said liquid-cooled condenser.

3. A method for air conditioning a chill room by maintaining substantially constant the temperature and the humidity of the air in the room by means of a refrigerating machine, including the steps of; operating the refrigerating machine to perform solely a refrigerating cycle to cool the air in the room to a predetermined temperature; then after attainment of the predetermined temperature, effecting operation of the refrigerating machine to transfer heat therefrom directly to the air in the room until the humidity condition in the room attains a predetermined value or until a predetermined temperature of the air in the room is attained, whichever is prior; and then repeating continuously the aforesaid steps in the sequence recited to maintain substantially constant predetermined temperature and humidity conditions in the room.

4. A system for maintainin constant the temperature and humidity of a space to be conditioned, comprising, in combination; a refrigerat ing machine including a compressor, a liquidcooled condenser, a refrigerant evaporator in heat transfer relation with the space to be conditioned, and refrigerant lines connecting said compressor, condenser and evaporator; an aircooled condenser in heat exchange relation with the space to be conditioned; refrigerant lines connecting said air-cooled condenser with said compressor for supplying hot compressed gas to said air-cooled condenser; means for controlling discharge of condensed refrigerant from said liquid-cooled condenser; a thermostat in the space to be conditioned for controlling the operation of said means for controlling said liquidcooled condenser; means for cutting in and cutting out said air-cooled condenser; and an hygrostat in the space to be conditioned for controlling the operation of said means for cuttin in and cutting out said air-cooled condenser.

5. A system for maintaining constant the temperature and the humidity of a space to be conditioned, comprising in combination; a refrigerating machine including a compressor, a liquidcooled condenser, a refrigerant evaporator in heat exchange relation with the space to be conditioned, and refrigerant lines operatively connecting said compressor, condenser and evaporator; an air-cooled condenser mounted in heat transfer relation with the space to be conditioned; refrigerant lines connecting said aircooled condenser in parallel with said liquidcooled condenser; a valve in the refrigerant lines between said liquid-cooled condenser and said evaporator adapted to control delivery of condensed refrigerant from said liquid-cooled condenser; a valve in the refrigerant line to said air-- cooled condenser for closing to cut out and for opening to cut in said air-cooled condenser; a thermostat in the space to be conditioned adapted to control said valve in the refrigerant lines for controlling delivery of refrigerant from said liquid-cooled condenser; and a hygrostat in the space to be conditioned for controlling said valve in said lines to said air-cooled condenser.

6. In a method for maintaining constant the temperature and the humidity of a space to be refrigerated by means of a refrigerating machine having a liquid cooled refrigerant condenser, and a refrigerant evaporator and an air cooled refrigerant condenser both in direct heat exchange relation with the air in the space to be conditioned, the steps of; operating the refrigerating machine to evaporate refrigerant in said evaporator to thereby cool the air in the space to be refrigerated to a predetermined temperature; then after attainment of the predetermined temperature, effecting operation of the machine to supply uncondensed refrigerant to said air cooled condenser for condensation therein and transfer of heat to the air in the space to be conditioned until the humidity condition in the room attains a predetermined value or until a predetermined temperature in the room is attained, whichever is prior; and then repeating continuously the aforesaid steps in the sequence recited to maintain substantially constant predetermined temperature and humidity conditions in the room.

'7. A system for maintaining constant the temperature and the humidity of a space to be conditioned, comprising in combination; a refrigerating machine including a compressor, a liquidcooled condenser, a refrigerant evaporator in heat exchange relation with the space to be conditioned, and refrigerant lines operatively connecting said compressor, condenser and evaporator; an air-cooled condenser mounted in heat transfer relation with the space to be conditioned; refrigerant lines connecting said aircooled condenser in parallel with said liquidcooled condenser; a valve in the refrigerant lines between said liquid-cooled condenser and said evaporator adapted to control delivery of condensed refrigerant from said liquid-cooled condenser; a valve in the refrigerant line to said aircooled condenser for closing to cut out and for opening to cut in said air-cooled condenser; a

thermostat in the space to be conditioned adapted to control said valve in the refrigerant lines for controlling delivery of refrigerant from said liquid-cooled condenser; and a hygrostat in the space to be conditioned for controlling said valve in said lines to said air-cooled condenser, the thermostat being operatively connected with said hygrostat to render the latter inoperative when said valve is opened for maximum discharge from said liquid-cooled condenser and to render said hygrostat operative when said valve is operated to control discharge from said condenser.

THEOPHIL EICHMANN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,837,798 Shipley Dec. 22, 1931 1,986,863 Terry Jan, 8, 1935 2,098,443 Vancott Nov. 9, 1937 2,154,136 Parcaro Apr. 11, 1939 2,293,532 Crane Aug. 18, 1942