US2206115A - Air conditioning apparatus - Google Patents

Description

July 2, 1940.

J. w. OBREITER, JR

AIR CONDITIONING APPARATUS Filed Feb. 25, 1939 Z/g- I G 6707100747- 3 %.ssukssmr 30 E ,2 ATTORNEY.

Patented July 2, 1940 PATENT OFFICE AIR CONDITIONING APPARATUS Joseph W. Obreiter, Jr., Glen Ridge, N. J., as signor to himself and William L. Ashby, Bloomfield, N. J., as trustees Application February 23, 1939, Serial No. 258,005

18 Claims.

The invention relates to air conditioning apparatus, and more particularly to apparatus in which the operation of the compressor in the circulation of the refrigerant through the evaporator unit is automatically controlled according to the desired capacity of said unit, so far as the transfer of heat from surrounding matter is concerned. q

In apparatus heretofore used in systems for conditioning air, or in refrigerating plants for other purposes, the refrigerant in gaseous form is compressed and delivered to a condenser where it is liquefied by contact with surfaces cooled either by circulating water or circulating air.

This liquid is delivered under pressure to the high pressure end of an evaporator unit in which it is again gasified as a result of the absorption or transfer of heat thereto from the surrounding air or other matter.

The outlet, hot, or lowpressure end of the evaporator unit is connected by a return pipe line to the compressor, thus setting up a cycle necessary to a continuing operation of the systern."

The amount of refrigerant passed through the evaporator unit varies not only with variance in the temperatures about same and the amount of heat absorbed by the refrigerant from the surrounding matter, but with the maintenance of a desired temperature in this surrounding matter. The pressure in the return line from the evaporator unit is considerably lower than the pressure at which the liquid refrigerant is delivered thereto, and the gas or vapor at said delivery end is superheated as a result of the absorption of heat thereby from surrounding matter.

If refrigerant in a volume in excess of that required to maintain the desired temperature 40 about the evaporator unit is present, a portion of this refrigerant is not evaporated before it is drawn with the gas into the compressor. This is objectionable since it impairs the eificiency of the compresssor. Furthermore, with this condition there will be a rise in the pressure in the return line to the compressor, or a loss in the desired relative proportional pressures at which the refrigerant is delivered to the evaporator unit and at which it is returned to the compressor. I

It has been the practice, in order to obviate this condition, to provide a thermostatic control for the expansion valve in the delivery line which is responsive to the varying temperature in the return line adjacent the evaporator unit.

(or ass-'6) With a low temperature adjacent the thermostat, the expansion valve is closed, thus retarding or stopping the delivery of liquid refrigerant to the evaporator unit and, when there is excessive superheating of the gas in said return line, evi- 5 dencing an inadequate supply of refrigerant, the valve is opened to increase the flow of the liquid refrigerant to said evaporator unit.

With varying demands upon the evaporator unit, a variable quantity of the refrigerant is 10 delivered to that unit and there is also a-variance in the pressure in the return line which has its efiect upon the rate of flow or volume of the refrigerant delivered to the unit and of the efficiency of the compressor,

In the ordinary apparatus, this requires frequent stoppage of the compressor during which an automatic adjustment of pressures upon opposite sides of the evaporator unit occurs. Under some conditions, the volume of gas being re- 20 turned is inadequate to develop the desired pressures by the compressor, and this also is a disturbing factor in the operation of the apparatus.

With the varying load upon the compressor, the heat of compression in the gases delivered 25 to the condenser differs, and since the condenser must be operated to take care of peak capacity of the compressor, there are, when water is used in the condenser, heavy losses, so far as the amount of circulating water is concerned. 30 1 With the above conditions in mind, I have provided an apparatus in which it is possible, except under the most extraordinary conditions, to continuously operate the compressor at its maximum capacity, thus ensuring uniform work- 35 ing conditions within a permissible range of variation.

In the apparatus of the invention, the relative pressures in the feed line for the liquid to the evaporator unit, and in the return line therefrom, 40 will be automatically maintained, irrespective of the demands of the evaporator unit and of the variance in the volume of refrigerant to meet such demands.

' By thus controlling such pressures, wide fluc- 45 tuation in the conditions about the evaporator unit, as well as the operation of the compressor under varying loads according to change in such demands, is avoided.

The apparatus is so constructed that any losses 5o arising from the continuous operation of the compressor are neutralized by savings effected in the operation of the condenser when water is used in this-condenser.

By maintaining a maximum gas pressure in 55 the crankcase of the compressor, when this type of compressor is used, an effective sealing of this crankcase is possible and air leakage into the refrigerating system is prevented. Furthermore,

when the compressor has the usual type of piston with inlet valves in the head thereof, oil will not be drawn from the crankcase into the cylinder with the resultant formation of oil slugs.

Furthermore, in apparatus embodying the invention, the capacity of the evaporator unit may be varied to meet the requirements for varying loads or working conditions without disturbing other working conditions in and.about the apparatus, and the compressor may be started and brought up to speed without difficulty at loads below the peak loads placed upon the evaporator unit.

The invention consists primarily in air conditioning apparatus embodying therein a compressor, a condenser, means delivering compressed gas from said compressor to said condenser, an evaporator unit, connections between said condenser and the high pressure side of said unit including an expansion .valve, connections between said compressor and the low pressure side of said unit, thermostatically actuated means varying the capacity of said expansion valve in accordance with the conditions at the low pressure side of said unit, and means for compensating for variation in pressure in the connection between the compressor and the lowpressure side of the unit without interfering with the output of said compressor, said means having therein a by-pass including therein a heat exchanger leading from said high pressure connections between said valve and said condenser and discharging into said low pressure connections, and means for -regulating the flow of liquid through said bypass by and in accordance with the pressure conditions in said low pressure line adjacent said by-pass; and in such other novel features of construction and combination of parts as are hereinafter set forth and described, and more particularly pointed out in the claims hereto appended.

Referring to the drawing,

Fig. 1 is a schematic view of an apparatus embodying the invention with one arrangement of the necessary parts and Fig. 2 is a similar view with another arrange- I ment of said parts.

Like numerals refer to like parts in both of said views.

In the embodiment of the invention shown in both forms of the drawing, I employ a compressor ID of any desired type, that shown in the drawing having a piston provided with ordinary intake valves in the head thereof, and a return line from the hot or low pressure side of the evaporator unit discharging into the crankcase of the compressor. This compressor is driven from an electric motor II.

The oiftake of the compressor is connected with a condenser l2 of the usual water cooled,

type, the piping through which the compressed gases flow from the compressor to the condenser being indicated at l3 and H, the former of which discharges into the shell iii of a heat exchanger, and the latter of which leads from the bottom of said shell into said condenser l2. The compressed gasses are passed through the heat exchanger in the form of theinvention illustrated, to utilize a portion of the refrigerant in extracting the heat of compression from these gases before the delivery of the compressed gas or condensate to the condenser l2, and inversely to utilize these gases to vaporize the refrigerant used in maintaining a substantially uniform working condition of the compressor by what I term a balance loader mechanism in the apparatus. By this arrangement, the work required of the said condenser I2 is materially reduced, thus effecting a very material saving in the volume of water required in the operation of the condenser.

The evaporator unit is shown at I6. While a single evaporator coil is shown inthis unit, it is obvious that two or more coils could be supplied with liquid refrigerant by the compressor l0 and still secure the same operative effect, provided that the compressor had a capacity adequate to furnish the necessary volume of refrigerant to the various coils in the unit.

Circulating water is delivered to a. coil I'l within the shell of the condenser l2 through a pipe I8 and passes from said coil through a discharge pipe I9. Arranged in the pipe line I8 is an ordinary automatic regulating valve 20 controlling the supply of circulating water to the condenser, according to the pressure conditions in the condenser. An automatic switch mechanism 2| is employed to control the circuit to the motor I I if the condenser pressure, or the pressure conditions at the suction side of the compressor. become too high or too low.

The detailed construction of the mechanism '2l and of the regulating valve 20 is immaterial to the present invention. Such devices have long been used in other types of refrigerating apparatus for the same purpose. It is a well known form of safety device for interrupting the circuit to the motor I I, to. stop the compressor operation, and to regulate the volume of cooling fluid according to pressure conditions in the condenser.

Connections, consisting of a pipe line 22 lead from the condenser l2, convey the liquid refrigerant from the condenser I 2 to the high pressure or cold side of the evaporator unit Hi.

Arranged in this line is an expansion valve 23 of the usual construction, containing therein a thermostatic controllingmechanism consisting of a bulb 24 located adjacent the low pressure or hot side of the evaporator unit I6, and a capillary tube 25 through which the valve is actuated with the development of a temperature in excess of that required in the operation of the apparatus when the load upon the evaporator unit is below its peak. This control feature is old and well known in the refrigerating art.

With the use of an automatic thermostatically actuated expansion valve, the supply of liquid refrigerant to the evaporator unit will vary automatically with the requirements of that unit to establish a fixed temperature condition about same. When these conditions are such as to require the extraction of a large volume of heat from the matter surrounding the unit, the refrigsuperheated at the low pressure or hot side of the unit. This condition requires the delivery to the unit of liquid refrigerant in greater volume. The use of the bulb 24 results in the opening of the valve 23 as a result of the expansion of the expansible material in the bulb and the delivery of an increased volume of the liquid refrigerant to the unit. With this increased volume of refrigerant, the pressure at the low pressure or hot side of the unit is increased, and the pressure drop across the unit, as well as the extent of the superheating of the gases being withdrawn from the unit, will both be reduced. With the reduction of the temperature of th gases, the expansible material will contract and the valve will be allowed to have closing movement by its spring whenever the degree of superheating and resultant pressure have attained a point where this can occur. With the partial closing of the valve 23, the flow of the liquid 1 refrigerant will be reduced in volume. In this manner, the supply of liquid refrigerant is adapted to the desired working conditions of the evaporator unit in developing the desired surrounding temperature. 7

' The temperature required to actuate the valve will vary with apparatus of different capacities, there being no critical temperature and no temperature requirements which cannot be varied according to the design of the apparatus in other respects.

Between ,the low pressure or hot side of the evaporator unit and the compressor is a pipe connection 26 which, with the type of compressor shown in the drawing, discharges into the crankcase thereof. It is a common practice to use, in. this return or low pressure line, a back pressure valve controlled by a humidostat or hygrostat or a thermostat,-this back pressure valve, shown at 21, being of old and Well known construction and serving to prevent, in large measure, the development in the operation of the'apparatus of excessively low pressures at the low pressure or hot 'end of the evaporator by the suction of the compressor.

All of the-parts heretofore described and the general arrangement and operation of these parts are old and well known in the refrigerating art,

excepting the use of the shell l5 of the heat exchanger.

As heretofore pointed out, with this arrangement the flow-of the hot gases from the evaporator unit will vary with changing working conditions of, or demands upon, the unit, and the pressure in the return line 26 will be subject to constant variation. If the volume of liquid refrigerant delivered to the unit I6 is increased, there is a drop in the temperature and a decrease of the pressure drop across the unit; an increase of the pressure of the gases flowing from said unit I6, and a decrease in the-effect of the suction developed by the compressor at the hot or low pressure end of the unit. With high pressure and low temperature, the suction of the compressor may cause a rate of flow which may reach'a point where some liquid refrigerant may actually be withdrawn from the unit and discharged within the compressor. With lower pressures and higher temperatures in the connections upon the low pressure or hotv side of the unit,'this condition cannot develop.

The balance loader of the invention consists of an evaporating coil 28 within the shell l5, and connections between one end of this coil and the high pressure or cold line between the condenser l2 and the evaporator unit l6, and between the other end of this coil and the low pressure or hot return line from the other side of said unit l6. The first of these connections is indicated at 29 and the latter at 30.

Arranged in the pipe line 29 is an electrically operated valve 3| and an expansion valve 32, the latter being controlled bythe prevailing pressure at the low pressure or hot side of the coil 28 by a thermostatic control consisting of a bulb 33 and a capillary tube 34 connecting said bulb with pressure return pipe 26 of the refrigerating system, this by-pass being between the compressor and the evaporator unit.

By using an evaporator coil in this by-pass, the temperature and pressure at which the refrigerant in gaseous form is delivered through the return line 26 to the compressor, ensures the presence in this return line of hot gas at a pressure approximating that required for the most efiicient operation of the main evaporator unit.

The volume of liquid refrigerant flowing through this by-pass when the balance loader" is in operation, is controlled by the expansion valve 32, and the operative moment of the balance loader is controlled by the electrically actuated valve 3| which may be of the solenoid or any other desired or well known type.

Arranged in the line 26 is apressurestat 35 controlling the electrical circuit for actuating the valve 3|, which pressurestat will define thelimits within which the balance loader is brought into and maintained in operating condition. This pressurestat is of old and well known construction, and if desired, other switch actuating mechanisms responsive to either heat or pressure may be used for controlling the circuit to said valve.

The humidostat, hygrostat or thermostat for controlling the back pressure valve 21 is indicated at 36.

In the embodiment of the invention shown in in the condenser shell itself above the coil in which the water is circulated for liquefying the refrigerant, or in the high temperature zone of the condenser. I Below this coil 28, I provide a baffle'3'l for compelling the heated gases delivered by the compressor'to flow about the coil 28 in a manner to secure not only the cooling of these gases, but to ensure the vaporization of the liquid refrigerant passing through the coil 28 in the manner above referred to.

The operation of the cooling unit of air conditioning or other refrigerating apparatus is substantially asfollows:

Before starting the operation of the apparatus, pressures throughout same will be equalized and the temperatures will be sufiiciently high to ensure the valves 23 and 32 being partially opened.

When starting a run of the apparatus embodying the invention, the compressor I6 is' actuated by the motor II to accumulate refrigerant in liquid form in the condenser l2 and build uppressure above such liquid The expansion valve 23 functions in the usual manner, to expand the liquid refrigerant passing through the high pres sure or cold line 22 to the high pressure or cold side of the evaporator unit l6. The refrigerant thus delivered absorbs heat from circulating air or other surrounding matter, and is thus rapidly evaporated and discharged from the low pressure or hot end of the unit and returned through the pipe 26 to the crankcase or other device for maintaining a supply of the refrigerant in'gaseous-form available to the compressor in continuing the succeeding cycles of operation of the apparatus. With delivery of the refrigerant in small volume and at low pressure before the desired high pressure has been developed in the condenser l2, the pressure in the return line 26 will be low and the temperature of the gases will be high, or such gases will be superheated.

A- portion of the liquid refrigerant is by-passed across the heating unit and is expanded by the valve 32 through the coil 28, and is evaporated by the absorption of the heat, including the heat of compression, from the gases being delivered by the compressor. The gases discharged from said coil 28, like those from the coil of the evaporator unit, are returned to the compressor through the return line 26. The superheated gases in the line 26 expand the material in the bulb 24, and the superheated gases in the pipe 30 expand the material in the bulb 33, thus causing the opening of first the valve 32 and then the valve 23 in a manner to admit a larger volume of expanded liquid into the evaporator unit I6 and into the coil 28. This, as heretofore stated, raises the pressure at the low pressure or hot side of the evaporator unit and of the coil 28 and cools both bulbs 24 and 33. This results in closing movement of both valves in the above order.

In starting, the pressure in the return line for the hot gases delivered by the evaporator unit is too low to ensure an effective compressor operation and an efficient continued action of the evaporator unit. The hot gases delivered through the by-pass will, with the hot gases delivered from the evaporator unit, rapidly establish that differential of pressure between the high pressure or cold side of the apparatus and the low pressure or hot side thereof necessary to ensure an effective compressor operation in building up the desired pressures throughout the apparatus.

The pressurestat 35 or other switch mechanism operated by pressure or by temperature conditions in the return line 26 will function to maintain the valve 3| open and thus permit liquid refrigerant to flow from the high pressure line 22 through the valve 32 and the coil 28 to the line 26 of the by-pass until such pressures and temperatures in the line 26 have been established as will ensure'the normal operation ofthe apparatus. The valve 3| is then closed by the pressurestat.

The point of delivery of low pressure, hot gases through the by-pass is between the back pressure valve 21, when such is used, and the low pressure side of the compressor, so that when pressures are being built up between the back pressure valve and the unit I6, a continuous delivery of hot gases from the by-pass to the line 26 is assured, since this by-pass leads from between the valve 23 and the condenser I2. Thus not only are hot gases drawn by the suction of the compressor at all times, but the effect of this suction upon the low pressure or hot side. of the evaporator unit is modified in a manner to ensure a more effective operation of this unit as a result of the development of the desired differential of pressure at opposite ends thereof.

The low pressure in the line 26- will ensure a continued supply of liquid refrigerant to the coil 28, and as the gases at the outlet of this coil become more highly superheated, more liquid refrigerant will be passed through the coil and thus tend to maintain an increasing volume of gases at higher pressure being delivered to the pipe 26 and therethrough to the compressor.

With this condition, which will be constantly fluctuating, there will be a more rapid condensation of the gases delivered by the compressor by reason of the greater' absorption of heat therefrom at said coil 28. This has the effect of more rapidly bringing the pressure conditions throughout the system to thoserequi'red in the normal operation of the apparatus.

As the pressure in the return line 26 increases to the minimum required for the efllcient operation of the evaporator unit I6, the valve 3| will be automatically closed, since under this condition, gas in sufficient volume will be delivered to the pipe 26 from the unit I6 to ensure continued operation of the device at its peak capacity.

If the valve 23 is operating under full capacity, the temperature and the pressure in the return line 26 will be such as to maintain the valve 3| closed, but with the partial closing of this valve 23 and with the lowering of the pressure in the return line 26 to any appreciable extent, the valve 3| will again be opened, thus causing a flow of the liquid, refrigerant through the by-pass across the unit I6 in volume sufficient to maintain the pressure and temperature of the gases being drawn by the suction of the compressor to that required for high efliciency in the operation of the unit I6. With a decrease in the flow of the liquid refrigerant through the valve 23 to the evaporator unit, there is an increase in the temperature and a decrease of the pressure in the return line, but by by-passing the evaporator unit by means of a balance loader, a substantially constant effect of the suction of the compressor is maintained and the compressor itself is thus enabled to operate continuously to deliver the refrigerant to the condenser in a substantially constant volume at a substantially there will be a constant balancing action, due

to fluctuations inthe capacity ofthe two valves 23 and 32. Those conditions which result in a partial opening or closing of the valve 23 will result in pressure conditions at the pressurestat 35 which will result in the closing or opening of the valve 3| with a resultant expansion of liquid refrigerant through the 'valve 32, which latter will have closing movement following opening movement of the valve 23 and will have opening movement following closing movement of the valve 23. This results in a continuous flow of substantially the same volume of refrigerant throughout the system at all times with continuous operation of the compressor and irrespective of the demands upon the evaporator unit I6. If these demands are great, the entire volume of liquid refrigerant may be passed through this unit. With lower demands, the quantity of refrigerant passed through this unit will be proportioned to such demands and the remaining refrigerant will be delivered to the return line through the by-pass.

By using a shell I5 forming a part of the connections between the outlet of the compressor and the condenser, and by maintaining a supply of gas at substantially uniform pressure in. the return line, there will be but little variation in the temperature of the gases being delivered by the compressor to the condenserl These gases will be partially condensed as a result of the absorption of the heat therefrom by the expansion of refrigerant through the coil 28, and there will be but little variationin the demands upon this coil. Under this condition, the only variation in the volume, temperature and-pressure of the hot gases delivered to the return line 26 through the by-pass will result from the volume of the liquid delivered through the expansion valve '32 responsive to temperature conditions at the low pressure or high temperature side of the coil 28, which will result as a reaction from the'increase of temperature and the decrease of pressure at the low pressure or hot side of the evaporator unit. With this condition, there will be a constant balancing of the operativeeffectsof the evaporator unit It and of the vaporizer 28in the by-pass, tending to equalize the suction at the low-pressure or hot end of the evaporator unit l6, irrespective of the volume of refrigerant passing therethrough, and a substantially constant load on the compressor.

In. the manner above described, the differential of pressures upon opposite sides of the evaporator unit can be substantially maintained. I believe by thus maintaining substantially constant pressures in the line 22 and in the return line 26, and a constant diflerential of these pressures, a substantial saving in the operation of a plant with a continuous operation of the compressor can be eifected.

In the embodiment of the invention illustrated in Fig. 2, the working conditions will be exactly like those heretofore described, since by placing the coil 28 in the shell of the condenser the only efiect upon the result will be a possible more efiective utilization of the liquid expanded through this coil in securing a more rapid liquefaction of the gases delivered to the condenser by the avoidance of the absorption of heat in passing the gases from the shell IE to the condenser.

The form of the invention shown in Fig. 1.

corresponds with that which has been used in a large air conditioningplant. In a smaller plant, the back pressure valve 21 and the pressurestat 35 may be dispensed with, since the apparatus as a whole may be so designed as to secure an adequate balancing action by the two valves 23 and 32 without resorting to the use of such instruments. In larger plants, requiring a more accurate control of the operation of the evaporator unit, greater efliciency and greater savings result from the use of such instruments.

The use of the automatic cutout 2| is a safety factor, the operation of which will result from only extraordinary conditions. In the ordinary evaporator unit this cutout is employed to interrupt the functioning of the compressor in the event of the development of excessively high pressures in the condenser l2, or excessively low pressures in the return line 26. With the apparatus of my invention, however, such pressures are maintaining within a range of fluctuation pe'rmitting a continuous operation of the compressor, so thatunder ordinary ,working conditions this automatic cutout will never function.

I believe it to be broadly new to provide, in an apparatus of the character herein described, a by-pass across the line to and from the evaporator unit, containing therein an evaporator including an expansion valve to deliver a varying quantity of hot gases to the return line between "the evaporator unit and the compressor in volume proportioned to the refrigerant delivered to the evaporator unit, but in inverse ratio to that assing through said unit.

It is not my intention to limit the invention to the detailed construction of any of the elements or instruments disclosed in the accompanying drawing, it being obvious that such connections between said compressor and the low pressure side of said unit, thermostatically actuated means varying the capacity of said expansion valve in accordance with the conditions at the low pressure side of said unit, and means for compensating for variation in pressure in the connection between the compressor and the low pressure side of the unit without interfering with the output of said compressor, said means having therein a by-pass including therein a heat exchanger leading from said high pressure connections between said valve and said condenser and discharging into said low. pressure connections, and means for regulating the flow of liquid through said. by-pass by and in accordance with the pressure conditions in said low pressure line adjacent said by-pass.

2. Air conditioning apparatus embodying therein a compressor, a c0ndenser,-means delivering compressed gas from said compressor to said condenser, an evaporator unit, connections between said condenser and the high pressure side of said unit including an expansion valve, connections between said compressor and the, low pressure side of :said unit, thermostatically actuated means varying the capacity of said expansion valve in accordance with the conditions at the low pressure side of said unit, and means for compensating for variation in pressure in the connection between the compressor and the low pressure side of the unit without interfering with the output of said conipressor, said means having therein a by-pass including therein an evaporator coil, connections including therein an expansion valve between one end of said coil and the high pressure side of said unit intermediate said condenser and said expansion valve, and the other end of said coil and saidconnections between the compressor and the low pressure side of said unit, means automatically varying the capacity of said by-pass expansion valve in accordance with the conditions adjacent the outlet of said coil and means for regulating the flow ofliquid through said by-pass by and in accordance with the pressure conditions in said low pressure line adjacent said by-pass.

3. Air conditioning apparatus embodying therein a compressor, a condenser, means delivering compressed gas from said compressor to pressure side of the ,unit without interfering with the output of said compressor, said means having therein a by-pass including therein an evaporator coil, connections including therein an expansion valve between one end of said coil and the high pressure side of said unit intermediate said condenser and said expansion valve, and the other'end of said coil and said connections between the compressor and the low pressure side of said unit, means automatically varying the capacity of said by-pass expansion valve in accordance with the conditions adjacent the outlet of said coil, a valve in the connections between said coil and said high pressure connections, and a mechanism responsive to pressure in the connections to the compressor from the low pressure side of said unit for controlling the operativeinterval of said last named valve by and in accordance with the pressure conditions in said low pressure line adjacent said by-pass.

4. Air conditioning apparatus embodying therein a compressor, a condenser, means delivering compressed gas from said compressor to said condenser, an evaporator unit, connections between said condenser and the high pressure side of said unit including an expansion valve, connections between said compressor and the low pressure side of said unit, thermostatically actuated means varying the capacity of said expansion valve in accordance with the conditions at the low pressure side of said unit, and means for compensating for variation in pressure in the connection between the compressor and the low pressure side of the unit without interfering with the output of said compressor, said means having therein a by-pass including therein an evaporator coil, connections including therein an expansion valve between one end of said coil and the high pressure side of said unit intermediate said condenser and said expansion valve, and the other end of said coil and said connections between the compressor and the low pressure side of said unit, means automatically varying the capacity of said bypass expansion valve in accordance with the conditions adjacent the outlet of said coil, means for regulating the flow of liquid through said by-pass by and in accordance with the pressure conditions in said low pressure line adjacent said by-pass, and a back pressure valve in the connections between the low pressure side of the unit and the compressor positioned between said unit and the point of discharge of the by-pass connections.

5. Air conditioning apparatus embodying therein a compressor, a condenser, means delivering compressed gas from said compressor to said condenser, an evaporator unit, connections between said condenser and the high pressure side of said unit including an expansion valve, connections between said compressor and the low pressure side of said unit, thermo statically actuated means varying the capacity of said expansion valve in accordance with the conditions at the low pressure side of said unit, and means for compensating for variation in pressure in the connection between the compressor and the low pressureside of the unit without interfering with the output of said compressor, said means having therein a by-pass including therein an evaporator coil, connections including therein an expansion valve between one end of said coil and the high pressure side of said unit intermediate said condenser and said expansion valve, and the other end of said coil and said connections between the compressor and the low pressure side of said unit, means automatically varying the capacity of said by-pass expansion valve in accordance with the conditions adjacentthe outlet of said coil, means for regulating the flow of liquid through said by-pass by and in accordance with the pressure conditions in said low pressure line adjacent said by-pass, a back pressure valve in the connections between the low pressure side of the unit and the compressor positioned between said unit and the point of discharge of the by-pass connections, and external means controlling the pressure at which said back pressure valve opens.

6. Air conditioning apparatus embodying therein a compressor, a condenser, means delivering compressed gas from said compressor to said condenser, an evaporator unit, connections between said condenser and the high pressure side of said unit, connections between said compressor and the low pressure side of said unit, a thermostatically actuated expansion valve having a bulb adjacent the low pressure or hot end of the evaporator unit, and means for compensating for variation in pressure in the connection between the compressor and the low pressure side of the unit without interfering with the output of said compressor, said means having therein a by-pass including therein an evaporator coil, connections between one end of said coil and the high pressure side of said unit intermediate said condenser and said expansion valve, and the other end of said coil and said connections between the compressor and the low pressure side of said unit, a thermostatically actuated expansion valve having a bulb adjacent the outlet of said coil and means for regulating the flow of liquid through said by-pass by and in accordance with the pressure conditions in said low pressure line adjacent said by-pass.

7. Air conditioning apparatus embodying therein a compressor, a condenser, means delivering compressed gas from said compressor to said condenser, an evaporator unit, connections between said condenser and the high pressure side of said unit, connections between said compressor and the low pressure side of said unit, a thermostatically actuated expansion valve having a bulb adjacent the low pressure or hot end of the evaporator unit, means for compensating for variation in pressure in the connection between the compressor and the low pressure side of the unit without interfering with the output of said compressor, said means having therein a by-pass including therein an evaporator coil, connections between one end of said coil and the high pressure side of said unit intermediate said condenser and said expansion valve, and the other end of said coil and said connections between the compressor and the low pressure side of said unit, a thermostatically-actuated expansion valve having a bulb adjacent the outlet of said coil, a valve in the connections between said coil and said high.

pressure connections, and a mechanism responsive to pressure in the connections to the compressor from the low pressure side of said unit for controlling the operative interval of said last named valve by and in accordance with the pressure conditions in said low pressure line adjacent said by-pass.

8. Air conditioning apparatus embodying therein a compressor, a condenser, means de'e livering compressed gas from said compressor 'to said condenser, an evaporator unit, connecstatically actuated means varying the capacity of said expansion valve in accordance with the conditions at the low pressure side of said unit, means for compensating for variation in pressure in the connection between the compressor and the low pressure side of the unit without interfering with the output of said compressor, said means having therein a by-pass including therein an evaporator coil, connections including therein an expansion valve between one end of said coil and the high pressure side of said unit intermediate said condenser ands'aid expansion valve, and the other end of said coil and said connections between the compressor and the low pressure side of said unit, means automatically varying the capacity of said by-pass expansion valve in accordance with ,the conditions adjacent the outlet of said coil, an electromagnetically operated valve in the connections between said coil and said high pressure connections, and a pressurestat arranged in the connections to the compressor from the low pressure side of said unit for controll ng the operative interval of said last named valve by and in accordance with the pressure conditions in said low pressure line adjacent said by-pass.

9. Air conditioning apparatus embodying therein a compressor, a condenser, means delivering compressed gas from said compressor to said condenser, an evaporator unit, connections between said condenser and the high, pressure side of said unit including an expansion valve, connections between said compressor and the low pressure side of said unit, a thermostatically actuated expansion valve having a bulb adjacent the low pressure or hot end of the evaporator unit, means for compensating f orvariation in pressure in the connection between the compressor and the low pressure side of the unit without interfering with the output of said compressor, said means having therein a by-pass including therein an evaporator coil, connections between one end of said coil and the high pressure side of said unit intermediate said con-.

denser and said expansion valve, and the other end of said coil and sa d connections betwe n the compressor and the low pressure side of said unit, a thermostatically actuated expans on valve having a bulb adjacent the outlet of said coil, an electro-magnetically operated valve in the connections btween said co l and said high pressure connections, and a pressurestat arranged in the connections to the compressor from the -low pressure side of said unit for controling the operative interval of said last named valve by and in accordance with the pressure conditions in said low pressure line adjacent said by-pass.

10. Air conditioning apparatus embodying therein a compressor, a condenser, means dolivering compressed gas from said compressor to said condenser, an evaporator unit, connections betwen said condenser and the h gh pressure side of said unit, connections between said compressor and the low pressure side of said unit, a. thermostatically actuated expansion valve for the evaporator unit having a bulb adjacent the low pressure or hot end, of the evaporator unit, means for compensating for variation in pressure in the connection between the compressor and the low pressure side of the unit without interfering with the output of said compressor, said means having therein a by-pass including therein an evaporator coil, connections between one end of said coil and the high pressure side .of said unit intermediate said condenser and said expansion valve, and the other end of said coil and said connections between the compressor and the low pressure side of' said unit, a thermostatically actuated expansion,

valve having a bulb adjacent the outlet of said coil, an electro-magnetically operated valve in the connect ons between said coil and said high pressure connections, a pressurestat arranged;

in the connections to the compressor from the low pressure side of said unit for controlling the operative interval of said last named valve by and in accordance with the pressure conditions in said low pressure line adjacent said by-pass,

and a back pressure valve in the connections between the low pressureside of the unit and the compressor positioned between said unit and the point of discharge of the by-pass connections.

11. Air conditioning apparatus embodying therein a compressor, a condenser, means delivering compressed gas from said compressor to said condenser,-an evaporator unit,-connec'- tions between said condenser and the high pres sure side of said unit including an expansion valve, connections between said compressor and the low pressure side of said unit, thermostatically actuated means varying the capacity of said expansion valve in accordance with the conditions at the low pressure side of said unit, means for compensating for variation in pressure in the connection between the compressor and the low pressure side of the unit without interfering with the output of said compressor,

said means having therein a by-pass including therein an evaporator coil, connections including thereinan expansion valve between one end of said coil and the high pressure side of said unit intermediate said condenser and said expansion valve, and the other end of said coil and said connections between the compressor and the low pressure side of said unit, means automatically varying the capacity of said by-pass expansion valve in accordance with the condi tions adjacent the outlet of said coil, an electromagnetically operated valve in the connections between said coil and said high pressure connections, a pressurestat arranged in the connections to the compressor from the low pres- 12. Air conditioning. appara tus embodying therein a compressor, a condenser, means delivering compressed gas from said compressor to said condenser including the shell of a heat exchanger, and connections between said shell and said compressor and said shell and said condenser, an evaporator unit, connectionsbetween said condenser and the high pressure side of said unit including an expansion valve, con-" nections between said compressor and the low/ pressure side of said unit, means automatically varying the capacity of said expansion valve in accordance with the conditions at the low pressure side of said unit, and means for compensating for variation in pressure in the connection between the compressor and the low pressure side of the unit without interfering with the output of said compressor, said means having therein a by-pass including therein an evaporator coil in said shell, connections having an expansionvalve therein between one end of said coil and the connections between the condenser and the high pressure side of said unit, connections between the other end of said coil and the connections between the compressor and the low pressure side of said unit, and means regulating the volume of liquid expanded through said coil by and in accordance with the pressure conditions in said low pressure line adjacent said by-pass.

l3.'Air conditioning apparatus embodying therein a compressor, a condenser, means delivering compressed gas from said compressor to said condenser including the shell of a heat exchanger, and connections between said shell and said compressor and said shell and said condenser, an evaporator unit, connections between said condenser and the high pressure 'side of said unit including an expansion valve, connections between said compressor and the low pressure side of said unit, means automatically varying the capacity of said expansion valve in accordance with the conditions at the low pressure side of said unit, and means for compensating for variation in pressure in the connection between the compressor and the low pressure side of the unit without interfering with the output of said compressor, said means having therein a by-pass including therein an evaporator coil in said. shell, connections including therein an expansion valve between one end- ,of said coil and the connections between the condenser and the high pressure side of said unit, and connections between the other end of said coil and the connections between the compressor and the low pressure side of said unit, means automatically varying the capacity of said by-pass expansion valve in accordance with the conditions adjacent the outlet of said coil, a valve in the connections between saidcoil and said high pressure connections, and a mechanism responsive to pressure, in the connections to the compressor from the low pressure side 55, of said unit for controlling the operative interval ofv said last named valve by and in ac- .cordance with the pressure conditions in said low pressure line adjacent said by-pass.

14. Air conditioning apparatus embodying therein a compressor, a condenser, means delivering compressed gas from said compressor to said condenser including the shell of a heat exchanger, and connections between said shell and said compressor and said shell and said condenser, an evaporator unit, connections between said condenser and the high pressure side of said unit including a thermostatically actuated expansion valve having a bulb adjacent the low pressure or hot end of the refrigerating unit for varying the capacity of said expansion valve in accordance with the conditions at the low pressure side of said unit, connections between said compressor and the low pressure side of said unit, means for compensating for variation in pressure in the connection unit, a valve in the connections between said expansion valve and said high pressure connections, and a mechanism responsive to pressure in the connections to the compressor from the low pressure side of said unit for controlling the operative interval of said last named valve by and in accordance with the pressure conditions in said low pressure line adjacent said by-pass.

15. Air conditioning apparatus embodying therein a compressor, a condenser, means delivering compressed gas from said compressor to said condenser including the shell of a heat exchanger, and connections between said shell and said compressor and said shell and said condenser, an evaporator unit, connections between said condenser and the high pressure side of said unit including a thermostatically actuated expansion valve having a bulb adjacent the low pressure or hot and of the refrigerating unit for varying the capacity of said expansion valve in accordance with the conditions at the low pressure side of said unit, connections between said compressor and the low pressure side of said unit, means for compensating for variation in pressure in the connection between the compressor and the low pressure side of the unit without interfering with the output of said compressor, said means having therein a by-pass including therein an'evaporator coil in said shell, connections having therein between one end of said coil and the connections between said condenser and the high pressure side of said unit, a thermostatically actuated expansion valve having a bulb adjacent the outlet of said coil, connections between the other end-of said coil and the connections between the compressor and the low pressure side or said unit, and a valve in the connections be-' tween said expansion valve and said high pressure connections, a mechanism responsive to pressure in the connections to the compressor from the low pressure side of said unit for controlling the operative interval of said last named valve by and in accordance with the pressure conditions in said low pressure line adjacent said by-pass, a back pressure valve in the connections between the low pressure side of the unit and the compressor positioned between said unit and the point of discharge of the by-pass connections, and external means controlling the pressure at which said back pressure valve opens.

16. Air conditioning apparatus embodying therehracompressur, a condenser, means delivering compressed gas from said compressor to said condenser including therein a heat exchanger, an evaporator unit, a connection between said condenser and said evaporator unit, connecting means between said connection and said heat exchanger, connecting means between the intake of said compressor and the low pressure or hot side oi! said evaporator unit, and connecting means between said last named connecting means and'said heat exchanger, valve means in the connection between said condenser and said evaporator unit, and in the first named connecting means, several means controlled respectively by the pressure conditions in said connecting means between said evaporator unit and said compressor, by the temperature conditions adjacent the low pressure or hot side of said evaporator unit, and by' the temperature conditions adjacent said heat exchanger to automatically actuate said valve means to inversely vary the relative volumes of liquid refrigerant flowing through said unit and through'said heat exchanger by and in accordance with the pressure conditions in the connecting means between said evaporator unit and said compressor.

17. Air conditioning apparatus embodying therein a compressor, a shell condenser, means delivering compressed gas from said compressor to said condenser, an evaporator unit, connections betwen said condenser and the high pressure side of said unit including an expansion valve, connections between said compressor and the low pressure side of said unit, thermostatically actuated means varying the capacity of said expansion valve in accordance with the conditions at the low pressure side of said unit, and means for compensating for variation in pressure in the connection between the compressor and the low pressure side of the unit without interfering with the output of said oompressor, said means having therein a by-pass including therein an evaporator coil 'in the upper part of the shell of said condenser, connections having an expansion valve therein' between one end of said coil and the connections between the condenser and the high pressure side of said unit, and connections between the other end of said coil and the connections between the compressor and the low pressure side of said unit, means regulating the volume of liquid expanded through said coiland means for regulating the flow of liquid through said by-pass connections to said coil by and in accordance with the pressure conditions in said low pressure line adjacent said by-p'ass.

18. Air conditioning apparatus embodying therein a compressor, a shell condenser, means delivering compressed gas from said compressor to said condenser, an evaporator unit, connections between said condenser and the high pressure side of said unit including an expansion valve, connections between said compressor and the low pressure side of said unit, thermostatically actuated means varying the capacity of said expansion valve in accordance with the conditions at the low pressure side of said unit, and means for compensating for variation in pressure in the connection between the com- .pressor and the low pressure side of the unit without interfering with the output of said compressor, said means having therein a by-pass including therein an evaporator coil in the upper part of the shell of said condenser, a bafile in said shell controlling the flow of compressed gases about said coil, connections having an expansion valve therein between one end of said coil and the annections between the condenser and the high pressure side of said unit, and connections between the other end of said coil and the connections between the compressor and the low pressure side of said unit, means regulating the volume of liquid expanded through said coil and means for regulating the flow of liquid through said by-pass connections to said coil by and in accordance-with the pressure conditions in said low pressure line adjacent said by-pass.

JOSEPH W. OBREITER, JR.

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