US2196778A

US2196778A - Refrigeration

Info

Publication number: US2196778A
Application number: US293475A
Authority: US
Inventors: Dodge Parker
Original assignee: Johnson Service Co
Current assignee: Johnson Service Co
Priority date: 1939-09-05
Filing date: 1939-09-05
Publication date: 1940-04-09
Anticipated expiration: 1957-04-09

Description

April 9,1940. GE] 2,196,778

REFRIGERATION Filed Sept. 5, 1939 1 33 E 37 29 C 27 I E v E f) Q5 24 2 E --s 22 M 6 21 E 19 3 I: 18 L 20 l: E 7 17 12 6 V 5 E 15 j I I 3maentor Patented Apr. 9, 1940 UNITED STATE 7 REFRIGERATION Parker Dodge, Chevy Chase, MIL, assignor to Johnson Service Company, Milwaukee, Wis., a corporation of Wisconsin Application September 5, 1939, sci-in No. 293,475

6 Claims.

This invention relates to refrigeration, and particularly to means for controlling the supply of refrigerant to an evaporator in response to the temperature of a space cooled by such evaporator.

Prior to the present invention, it has been proposed to cause a small expansion valve of the superheat control type to pilot the action of a larger valve (known as a booster valve) which controlled the fiow of refrigerant to the evaporator. In this way, a small and inexpensive expansion valve, which, because of its small internal friction, can be made very sensitive, can accurately control supply of refrigerant to a large evaporator.

' In the operation of certain cooling plants, notably air conditioners, it is desirable to reduce the supply of refrigerant to the evaporator in response to falling temperature and thus reduce the total refrigerating eflect.

The present invention provides a method of controlling a booster valve in such a way that when temperature of the cooled space is at or above a chosen value, apilot valve of the superheat control type exercises solecontrol. As temperature of the cooled space falls below. such value, a space. thermostat increasingly modifies and then suppiants the control exercised by the pilot valve, causing the booster valve to close more and more with falling temperature.

The scheme is safe because the space thermostat can reduce but never increase the rate' of feed of liquid refrigerant beyond theilimits imposed by the superheat pilot valve. It is inexpensive and accurate because the mechanism controlled by the space thermostat is small and has slight internal friction.

A simple embodiment of the invention is illustrated in the accompanying drawing in which the single figure is a view largely in section as to the 40 control means and illustrating the refrigerating circuit with the compressor and condenser indicated in diagram.

a The means for drawing refrigerant from the evaporator andfor llquefying it would be, conventional, and may assume any form known in the refrigerating art. For example, the invention can be used with an absorption system.

In the drawing, the pipe I is the suction line leading to the compressor diagrammatically indicated at M. The compressor M delivers hot compressed vapor to a condenser diagrammatically indicated at. C in which it is cooled and thus caused to assume the liquid phase. From the condenser C, the liquid refrigerant is fed through connection 2 to the receiver 3.

The ,valve 4 is an ordinary suction limiting valve. The use of this is optional. When used, it prevents, or at least limits, the reduction of evaporator pressure and consequently the reduction of evaporator temperature, which would otherwise occur if the compressor should continue to operate at its normal volumetric rate while the supply of. refrigerant to the evaporator is restricted. The use of suction limiting valves iswell known, and one is here illustrated w to indicate the possibility of its inclusion, if 'de-" sired.

From the receiver 3, the liquid line 5 leads to the booster valve generally indicated by the numeral 6 applied to its body. The discharge side 5 of the valve is connected at l to the header 8 of an'evaporator, some ofwhose tubes are indicated at 9. The evaporator suction connection ii leads from the upper end of header 8 to suction line I, the limiting valve 4 being interposed, Y0

' if desired. T

The booster valve 6 is preferably of the balanced typeso as to be indifferent to pressure of flowing liquid reacting on the valve, and'is shown as comprising two poppet valve heads l2 and i3 on a common stem I4, and coacting with spaced seats in a shell l5, through which seats flow occurs in opposed directions from the inlet to the outlet of the valve. The stem II is urged upward by a light compression spring It so that head I! ls held in engagement with a flexible diaphragm It.

The diaphragm is clamped at its periphery between the body 6 of the booster valve and a bonnet l9 bolted thereto. It is subject on its lower face to the pressure of liquid refrigerant arriving through liquid line 5 (head pressure) and is loaded in the opposite (valve closing) direction by coil compression spring 20.. The stress on spring 20 is adjusted by a serewj i, 4o sealed by cap 22. The diaphragmis also loaded by fluid pressure communicated through pipe 23, as will be explained.

A by-pass connection 26 leads from the receiver 3, preferably but not necessarily abov the liq- -uid level therein, to a pressure motor operated throttling valve'25 and a restricted fiow orifice V fitting 26 connected in parallel between connection 24 and a connection 2'l, which leads to the superheat control expansion valve 28, and to 50 which the pipe 23 is also connected.

The fitting 26 is preferably arranged according to known practice to receive interchangeable orifice plates of different capacities. The valve 25 is operatedby'a bellows motor 29 connected 5 by capillary tube 3| with bulb 32 which contains a liquid adapted to develop a suitable rising pressure in response to rising temperature. pressure reacts upon motor 29 to close the valve 25 in opposition to a spring 33 which biases the valve in its opening direction.

The parts are so arranged that valve 25 closes when bulb 32 (which is subject to conditions in the cooled space) is at or above the chosen temperature and opens gradually as bulb temperature falls below that value.

The superheat control expansion valve 28 is preferably of the type in which a flow controlling valve responds to a valve closing force proportional to evaporator pressure, and a valve opening force proportional to temperature of refrigerant leaving the evaporator. It is so loaded as to reach equilibrium under conditions such that refrigerant leaving the evaporator is slightly superheated. Such valves are in common use and are manufactured in many commercial forms.

One form, which is shown and described in the patent to Newton No. 2,120,764, June 14, 1938, is illustrated in detail in the drawing, and requires no description beyond the general statement of its function above given. Its thermostatic bulb 34 is applied to suction connection I l, and affects the valve 28 through capillary tube 35. The valve 28 discharges through connection 31 to any point at evaporator pressure, conveniently the top of header 8.

The flow capacity of fitting 26, the stress'on spring 20, and the operating characteristics of valve 28 are so coordinated that when valve 25 is closed, i. e., when temperature at bulb 32 is at or'above the chosen value, valve 28 pilots the booster 6 to give the desired slight superheat at connection H. The effect is usually to operate evaporator 8'9 nearly flooded, but the invention is not limited to flooded action and does not exclude other known operative characteristics for the evaporator attainable with superheat control valves.

As temperature at bulb 32 starts to fall below the chosen value, valve 25 starts to open. For any asumed position of valve 28, pressure above diaphragm l8 will rise as valve 25 opens, thus closing the booster valve slightly. Within a limited range,

valves

25 and 28 control conjointly for opening of valve 25 increases the pressure on diaphragm I8 so that the booster valve closes somewhat. This reduces evaporator pressure and may increase the temperature at bulb 34because of the reduction of total refrigeration. In any event, valve 28 tends to open and restore balance, seeking, as it does, to limit superheat. If valve'25 opens far enough, valve 28 opens wide, and from then on valve 25, if it open further, alone controls the booster valve.

If theline 24 leads from above the liquid level in the receiver as shown, the secondary path via 24, 2B (25) 21, 28, 31, passes only refrigerant vapor. This is preferred because the refrigerating effect of the small volume of vapor is negligible whereas the use of liquid refrigerant would involve a larger refrigerative effect and require the use of much better insulation of the secondary path to ensure stable action.

While I prefer to use the superheat control type of expansion valve to pilot the booster valve, as shown, other types of automatic expansion valve are known and may be substituted. In such case,

the space thermostat modifies their action inan analogous way. a

While a choke by-pass around valve 25 15 bevchamber, the pressure in which serves to adjust the booster valve; a thermostatic valve responsive to a temperature influenced. by said evaporator and serving above a chosen temperature to establish a minimum flow rate from the receiver to I said chamber and as temperature falls below said value to enlarge said flow rate; and an automatic expansion valve connected between said chamber and a point in the circuit at evaporator pressure.

2. The combination of a refrigerating circuit including an evaporator and a receiver; a booster expansion valve controlling flow of refrigerant from receiver to evaporator and including a motor chamber, the pressure in which serves to adjust the booster valve; a thermostatic valve interposed in a connection between the receiver and said motor chamber, responsive to a temperature influenced by said evaporator and serving above a chosen temperature to establish a minimum flow rate from the receiver to said chamber and as temperature falls below said value to enlarge said flow rate; and an expansion valve responsive to the superheat at the evaporator outlet connected between said chamber and a point in the circuit at evaporator pressure.

3. The combination defined in claim 2 in which the receiver is only partially liquid filled and the connection from the receiver to the chamber leads from a point above the liquid level in the receiver.

4. The combination of a refrigerating circuit containing a volatile refrigerant and including an evaporator, means for withdrawing evaporated refrigerant from the evaporator and for liquefying the same at a pressure higher than that in the evaporator, and a valve controlling the delivery of liquid refrigerant from said liquefying means to the evaporator; a pressure motor connected to actuate said valve and comprising a movable abutment subject in a valve opening direction to the pressure in said liquefying means, and in a valve closing direction to pressure in a chamber; means for biasing said valve in a closing direction; means forming a by-pass from said liquefying means to said'chamber and thence to a point in the circuit at evaporator pressure; an expansion valve responsive to the superheat at the evaporator outlet controlling said by-pass' between said chamber and the point at suction pressure; regulating valve means interposed between the liquefying means and said chamber and operable to establish a minimum fiow rate and to enlarge the flow rate above such minimum; and thermostatic means subject to a temperature affected by said evaporator and connected to control said regulating valve means, the parts being so arranged that above a definite temperature the minimum fiow rate'is efiective, and as temperapansion valve controlling flow from condenser said controls being responsive to a combined effect of evaporator pressure and temperature of refrigerant withdrawn from the evaporator andthe other responsive to the efiect of temperature in a space cooled by said evaporator.

PARKER DODGE.