US2155510A - Air conditioning system - Google Patents

Description

April 25, 1939. w HEPH RD 2,155,510

AIR CONDITIONING SYSTEM Filed March 16, 1555 2 Sheets-Sheet 1 lnllmllllumm W INVENTOR 11.151551 B. $HEPPERD ATTORNEY April 25, 1939.

W. B. SHEPPERD AIR coumnonme SYSTEM Filed March 16, 1935' 2 Sheets-Sheet 2 INVENTOR Wmm S. S EPPERD BY ATTORNEY Patented Apr-.25, lass UNITED "STATES PATENT OFFICE;

. 2,155,510 1 am CONDITIONING SYSTEM wuuamnshepm su. Me,

. LewisLBcott,

St. Louis,

assignor to Mo.

Application M 16, 1935, Serial No. 11,396 1. Claims. (01. 62-478) This invention relates to an air conditioning system particularly adapted to heat or cool houses, and has for its object an improved systerm which is exceedingly simple and reliable in operation, as well as economical and inexpensive.

The majority of air conditioning systems for complete heating and cooling utilise, as the means of producing cold, compressors and electric motors which are high in first cost, noisy, and high in operating cost. In addition to this type of equipment they utilize some means of heating for the winter season consisting of an oil or gas burner, together with a heat absorbingmedb um, so that the complete-plant for winter and summer air conditioning gets very expensive.-

containing a body of liquid refrigerant in thermal connection with the body of air or other substance to be cooled; a boiler in which, by means of a source of heat, another body of the same raised to a high tempera ture, the vapor pressure e ng correspondingly wherein vapor from the hot liquid is accelerated to a high velocity by expanding it through a nozzle, thehigh velocity stream of vapor being so disposed as to entrain vapor from the flrstmentionedbody of refrigerant, the mixed stream of being, expelled through an outlet by itsfiown velocity; and a condenser, wherein the heat of vaporization is removed from the vapor that issues from the ejector; together with such accessorles as are required to remove the condensed referi'gerant from the condenser and replenish the supply in the evaporator and'the boiler as required. -It ls understood that other accessories will circulate the air or other matter being cooled by the evaporator and that a sumcientsupply of air, water, or other for removing the heat from the condenser-.1 also provide in my system an arrangement whereby, by use of a check valve and a shut-oi! valve. I can adapt and utilize this same apparatus; in-

My system is hermetically sealed parts, thereby being quiet the high pressure inflammability;

including ethylether, are inflammable, and are 40 breathed.

coolant will be provided" cluding the refrigerant, for complete heating and winter air conditioning.

I am fully aware that electors have been used in. connection 'with refrigeration cooling systems where water is used as the refrigerant. system requires the use of three ejectors in order to produce a vacuum on the water to be cooled at approximately 29%" because of the exceedinglylow vapor tension of water, andin order to get economy steam pressures must be used at ap proximately one hundred pounds or more, State laws'do not permit the use of high pressure steam without a licensed engineer attendant, which would not be practical for household use. A

pump of considerable size is required to circulate the cool water and another pump removes the condensate and returns it to the boiler. .I am also aware of the fact that a cooling system using an ejector with some refrigerant other than water has been proposed, but never to my knowledge been put into largely to the fact that no suitable refrigerant successful operation, due

has been found that would give economical results in a system of this type.

Among the refrigerants gested, chloroform, the various alcohols, and

the ethers except ethyl ether, boil under such excessively low pressures, or high vacua, that they 7 can be used successfully only in a cooling device adapted to expose a thin layer of the liquid refrigerant; if used in a tubular refrigerating coil of conventional design, adapted to boil the refrigerant within the tubes, only the uppermost layer of the refrigerant will be cooled to the desired temperature, and part of the cooling coil will be progressively warmer, with consequent decreased cooling efl'ect. Another fault of this class of compounds is their all of the alcohols and ethers explosive when their vapors are mixed with air. fire hazard makes them unsuitable for use in unattended domestic installations. Many substances of these classes are dangerous. poisons, being anaesthetics conscious, aswell as produce death; they are therefore not safe for usein cooling coils which are used directly forcooling air that is to be Such a 5 that have been sug- 25 the portion in the lower that will render a person un- Carbon .disulflde is both violently poisonous so and inflammable, hence is unsuitable for this use. Carbon tetrachloride is, not inflammable, in, fact it is an eflicientiire extinguisher; but it is sufilcisntly toxic to constitute a hazard when p esent in the quantity required for air cooling 5 flammable, and most of them are toxic as well,

making them unsuitable for domestic service.

The refrigerants commonly used in compression machinessuch as ammonia, sulphur dioxide,

dichlorotetrafluoroethane, dichlorodifluoromethane, methyl chloride, etc., if used in an ejector system would require boiler pressures of several hundreds of pounds; in most of them the boiler would operate above the critical temperature of the refrigerant. It is difilcult to construct a boiler to withstand the pressures, and even more dimcult-to replenish the liquid refrigerant in the said boiler as it is vaporized.

.Methylene chloride, commercially known as carrene, can be used in an ejector system, and has satisfactory pressure characteristics; it is almost non-inflammable, and is reasonably nontoxlc. -In service, however, its efficiency is impaired by the condensation of a considerable portion of the vapor into liquid during its expansion in the nozzle of the ejector; the portion condensed'is in the form of droplets which pass through the low pressure vapor without imparting to it all of this velocity. The said droplets have also a tendency to erode and roughen the surfaces of theejector nozzle and throat along which they are driven, causing a progressive lowering of efiiciency as the surfaces become roughened and impose increasing friction upon the vapor during its expansion. Such friction lowers the efiiciency of the ejector by reducing the velocity of the jet of vapor, issuing from the nozzle, and also by increasing the turbulence of the vapor'in that iet, which makes the high velocity jet of vapor less effective in entraining the lowpressure vapor that is drawn from the cooling coil.

The distinguishing features of the refrigerants, the use of which in the elector system constitutes this invention are: When any one of my refrigerants in the form of saturated high pressure vapor is supplied to the elector nozzle there is either no condensation'ora negligibly small amount of condensation during expansion. Such condensation would be a source of waste in a number of ways as above enumerated. My refrigerants used in the present invention condense little if at all when expanding in-=a nozzle. Thermodynamically the expansion characteristic is expressed by saying that the entropy of saturatedvapor shall increase slowly ornot at all with decreasing temperature. I have foimd that for best results the maximum condensation permissible is six percent; this is determinedfor any specific substance as follows: go Let (a) represent the entropy of saturated vanot at the temperature at which it comes from the boiler. 'l I Let (b) rent the'entropy of saturated vaporat the pressure prevailing in the evaporator. let represent the entropy of liquid refrigerant at the temperature and pressure prevailing in the-evaporator.

Then (a) must not be less than .94b+.06c. I In order to keep the evaporator or cooling unit.

7 down to a' practical size and to eliminate such accessories as circulating pumps, film type evaporators, spray type evaporators: etc., the pressure in the evaporator must not be less than three pounds per square inch, absolute (not 75 We) pressure. At this pressure 'the boiling temperature of the refrigerant. will not increase more than ilve' degrees per foot depth,

moderate cost the refrigerant must be such that the pressure in the boiler will not exceed 300 pounds per square inch under the highest possible operating temperature. This temperature will vary with the nature of the application; typical .cases will be the use of low-pressure steam as a source of heat, with a maximum possible temperature approximately 240 F. and average operating temperature a bit over 200 F.; or the use of a direct fired unit, with temperature and pressure limited by thermostatic or pressure actuated means or both, wherein the working temperature may with a suitable refrigerant go to 300 F. without exceeding 300 pounds pressure.

The refrigerant must be chemically inert and stable under operating conditions. By inert is meant that at the temperature encountered, and in the presence of traces of air that are likely to occur in the refrigerating apparatus, they shall not attack iron, copper, brass, and other commonly used structural metals or be decomposed by contact with them.

The refrigerants in order to be entirely safe in service must be non-toxic under conditions and concentrations encountered in service, and

must be non-inflammable in'order that the moderately large plants required for air conditioning service shall be free from fire hazard when installed in a building.

I have found that at; least three refrigerants comply with all of the above mentioned conditions. These refrigerants are:

A compound commonly called F-ll which is commercially known as fluorotrichloromethane Various other advantages will be apparent from the following detailed description of an embodiment of the invention; and the novel fea- "tures will be particularly pointed out hereinafter in connection with the appended claims.

The accompanying drawings illustrate diagrammatically a simple system constructed in accordance with my invention.

Figure 1 is a diagrammatic drawing of my complete air conditioning system.

Figure 2 is an enlarged sectionai'cut of my transfer unit which functions to transfer the liquid from the condenser back to the boiler.

Figure 3 Lean end sectional view taken, on the line--l-l .of Figure 2.

Figure4isanendsectionalviewtakenolithe line 2-2 of Figure 2..

I will first describe my system as it operates for cooling purposes.

'Referring now to the drawings. the numeral l indicates a gas burner which is automatically controlled by the room-thermostat 2, and which is ignited by the pilot light 3. The numeral 4 indicates a motor operated valve in the main gas line, the operation of which is controlled by the room thermostat as well as' by certain other controls which will be described. The numeral I indicates boiler coils for absorbing heat from the burner I, which coils are connected to the top header of the boiler indicated by the numeral 3. The numeral 1 indicates the chimney through which the products of combustion from the burner pass to the outside atmosphere.

The. liquid refrigerant above referred to is contained within the boiler coils I and top header 3, and when the burner I is in operation, the liquid refrigerant passes under pressure through the pipe 3 to the ejector nozzle 9 and issues from said nozzle at high velocity, and passes through the body of low pressure vapor to and imparts some of its motion to this low pressure vapor, and the combined stream is literally thrown through the Venturi opening H into the condenser l2 where a higher pressure than that of the cooling coil I3. is maintained. The condenser I2 contains pipes l4 through which cool water passes for condensing the vapor just referred to, the vapor giving up to the water the heat that it has removed from the air in the house.

' My refrigerant has high vapor density and moderate pressure; hence, the size of the ejector is moderate and its emciency high.

A float valve is which is contained in an enlarged header connected with the cooling coils l3 handles approximately twelve gallons per hour of the refrigerant for each ton of cooling capacity;

' The numeral it indicates a back pressure limit protect the boiler in case of denser l2 serves to force the the circuit to the motorized valve 4- in case of failure of the cool water supply to the condenser coil [4. The numeral H indicates a high temperature cut-out switch to cut-out switch is also a protection boiler pressures and acts to break the motorized valve 4 in case of excessive pressure or temperature. The'current is furnished for operating the motorized valve 4 through the power wires l8 and f3. The numeral conventional hand shutoff switch.

The numeral 21 indicates a metal cabinet which contains an air blower 22 adapted to suck air thrpugh filters 23 from the rooms to be cooled and over the cooling coil l3 and deliver it through the duct" 24 to pipes not shown connected with the rooms to be cooled.

The evaporator or cooling coil I3 is constantly I filled to a certain level with liquid refrigerant;

as this liquid evaporates due to absorbing heat from the air passing over it, the float valve i5 admits more liquid refrigerant to replace it. The liquid refrigerant passes from the lower part of the condenser l2 through the pipe 25 and is controlled by the float valve l5 as The pressure produced by the ejector in the conliquid refrigerant through the float valve I! back to the evaporator as rapidly as said float valve permits. The remaining liquid from the condenser l2 flows by gravity through valve 26 into the transfer unit 21. In the position shown in the drawings vent pipe 23 communicating with the condenser I2 is open through relief pipe 29 to the body of the transfer unit. The hydrostatic pressure of the refrigerant liquid cooling from the condenser a. position where pipe 28 to the condenser is closed and pipe 34 to the boiler is open. Under is heated and vaporized and the condenser l2 than does against excess I the circuit to 23 indicates the I boiler. Blower 22 the rooms, which is heated and is before described.

this condition the hydrostatic pressure of the liquid in the float chamber 21 opens valve 33 and liquid flows through outlet pipe 36 into the boiler. As soon as the liquid level is lowered, the float 3| causes rod 32 and valve 33 to move down, closing ofl. pipe 34 and the float chamber is again filled from the condenser as before described. It will be noted that pipe 33 extends slightly above the bottom wall of condenser l2 and that pipe 23 extends still further above the bottom wall of pipe 30. The transfer unit is shown in more detail in Figures 2, 3 and 4 in slightly modifled form, as in Figure 1 it is merely shown diagrammatically in the complete system. In the construction shown in Figure 2 of the transfer unit, the float 3! is adapted .to slide on the rod 32, which rod is connected to the piston valve 33. The float 3| is adapted to move coil spring 31 which eventually contacts an enlarged portion of valve 33 on the .to be moved into and from the positions, above described, by snap action which insures full travel of the valve 33 from fully open, through pipe 23 to fully open through pipe 34, or vice versa. The valve 33 being in the form of a piston valve with ports all around its periphery is perfectly balanced; hence, takes very litle power to operate and the snap action device insures it against eroding of the edges of the valve and seat. The above described transfer unit permits automatic transfer of theliquid refrigerant from the-condenser to the boiler in a completely hermetically sealed device without the use of any motors or .When'it is desired to use my air. conditioning system for winter operation for heating instead of cooling, the valve 42 is opened thereby. permitting the vapor from the boiler to pasfthrough.

. valve permits the flow of the liquid to the boiler,

back flow of liquid from the but prevents any functions to move the alrfrom air passes over the coil l3 and transferred through the duct to the rooms. When this system is used for heating in winter the thermostat 2 is arranged to turn the burner l on when the'temperature drops below 70. The control it which limits the pressure in the condenser 12 functions during the winter operation as well as the summer operation to protect the condenser and connected parts against excessive pressure. During the winter operation no water is used incoil l4 in "the condenser l 2; this condenser will be fllled with vapor from the boiler 6 and will thereby be maintained at the same temperature as the cooling coil l3. Condenser I 2 will therefore be coveredwith some sort of insulating material to retain this heat and prevent-it from acting. as a radiator; the liquid condenser under these back to the boiler in the same manner as before described .when the systemis operating as a cooling device. g g

I have given three refrigerants that, meet my requirements in such a conditions will flow system as above dethe same conditions of operation,

' with a non-return valve, a device whereby a vent causing refrigerant is commercially known as methane. I have found that of the requirements in the cooling as well as the heating cycle. The characteristics of F-113 are as follows:

Boiling point 118 F.

The vapor pressure of this fluid in the cooling coll I! when operating as a cooling plant is 3. pounds per square inch absolute at 50 F. Under the pressure in the condenser I2 is about twelve pounds per square inch absolute at 110 F. (Wherever cooling coil is used in this trifiuorotrichlorounder atmospheric pressure heat is transferred from the refrigerant boiling under low pressure to the air or other medium that is being cooled.)

The pressure in the boiler t is approximately 135 pounds per square inch absolute at 300 F. which is the preferred operating temperature of the fluid in the refrigeration cycle.

The specific volume of the vapor issuing from the. cooling coil i3 is eight cubic feet per pound and its latent heat issixty-six B. t. u. per pound.

When the unit is operating for heating instead .of cooling the vapor pressure in the cooling coil II is approximately twenty-eight pounds per square inch absolute. Under this condition the vapor density is 1.1 pound per cubic foot and the latent heat is approximately fifty-nine B. t. u. per pound.

The molecular weight of this substance is 187.4. The specific heat of theliquid at 70 F. is 0.198. The density of this liquid at 70 is about ninetyeight pounds per cubic foot.

I claim:

1. In an ejector system of refrigeration, a device for transferring the liquefied motive fluid from the condenser to the boiler. consisting of a vessel located above the boiler, said vesselhaving aliquid inlet pipe from the bottom of the condenser into the vessel provided with a non-return valve, and also liquid outlet pipe leading from the bottom into the boiler, this outlet also being provided said vessel also having at the top of the vessel is connected alternately, first to the condenser,

liquid to flow from the condenser through the flrst mentioned non-return valve into the said being connected to the boiler, into which the 'refrigerant liquid flows through the second mentioned non-return valve by gravity.

2. The process of refrigeration comprising extracting heat from space surrounding a liquid refrigerant by evaporation intensified by entraining vapors. from said liquid in a stream of expanding refrigerant gas to reduce the pressure on said liquid, said refrigerant comprising one of the group of halo-fiuoro derivatives of an aliphatic hydrocarbon, including fiuoro-dichloro-methane, fluoro-trichloro-methane and trichloro-trifluoroethane. y

v 3. The process of refrigeration comprising extracting heat from space surrounding a liquid refrigerant by evaporation intensified by entraining vapors from said liquid in a stream of expending refrigerant gas to reduce the pressure on said liquid, said'rei'rigerant' comprising ahalofinoro derivative'of an aliphatic hydrocarbon,

will boil at evaporator temperature at a not less than three pounds v uch absolute, and which has a pressure of not this fluid meets all Y description it is understood that the meaning intended is a device wherein from the surface of said said device of thesaid vessel vessel; the said vent then.

per square more than three hundred pounds per square inch for saturated vapor at a temperature of 300 1'.

4. The process of refrigeration comprising ex- ,tracting heat from space surroimding a liquid refrigerant by evaporation intensified by entraining vapors from said liquid in .a stream of expending refrigerant gas to reduce the pressure on said liquid, said refrigerant comprising fluorodichloro-methane, CHFCla.

5. The process of refrigeration comprising extracting heat from space surrounding a liquid refrigerant by evaporation intensified by entraining vapors from said liquid in a stream of expanding refrigerant gas to reduce the pressure on said liquid, said refrigerant comprising fluorotrichloro-methane, CFCla.

6. The process of refrigeration comprising extracting heat from space surrounding. a liquid refrigerant by evaporation intensified by entraining vapors from said liquid in a stream of expanding refrigerant gas to-reduce' the pressure on said liquid, said refrigerant comprising trichloro-trifluoro-ethane, CzClsFa.

I 7. The process of refrigeration comprising ap-- plying heat to a liquid refrigerant to produce a gas under pressure, extracting heat from space surrounding a body of liquid refrigerant through evaporation of said liquid by entraining vapors body in an expanding stream of said gas under pressure to reduce the pressure over said body, said refrigerant comprising a halo-fluoro derivative of an aliphatic "by-.- drocarbon having an entropy of vapor at boiler temperature of not less than .94 entropy of the vapor rt evaporator pressure plus .06 of the entropy of the liquid at evaporator temperature.

8. The process of refrigeration gas under pressure, extracting heat from space surrounding a body of liquid refrigerant through evaporation of said liquid by entraining vapors from the surface of said body in an expanding from boiler pressure to evaporator pressure will have not to exceed six per cent of condensation.

9. The process of refrigeration comprising applying heat to a liquid refrigerant to produce a 394; under pressure, extracting heat from space surrounding a body of liquid refrigerant through evaporation of said liquid by entraining vapors from the surface of said body in an expanding stream of said gas under pressure to reduce the pressure over said body, said refrigerant comprising a fluid which will boil at evaporator temperatureat a pressure'ofnot less than three pounds per square inch absolute, which has a pressure of not more than three hundred pounds per square inch ture of 300 ejector with a theoretically perfect frictionless nozzle from boiler pressure to evaporator pressure will have not to exued six per cent condensation.

aliphatic hyfor'saturated vapor at a tempera-- E, and which when expanded in an.

7 comprising ap plying heat to a liquid refrigerant to produce a 10. The process of refrigeration comprisingapplying heat toa. liquid refrigerant to produce a gas under pressure,

surrounding a body of liquid refrigerant through evaporation of said liquid by entraining vapors i from the surface of said body in an expanding stream of said gas under pressure to reduce the pressure over said body, said refrigerant comprising a fluid which will boil at evaporator temperature at a pressure oi not less than three pounds per square inch absolute, which has a

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