US2624181A - Means and method of controlling refrigeration systems - Google Patents

Description

Jan. 6, 1953 L. R. ERWIN ETAL 2,624,181

MEANS AND METHOD 0 CONTROLLING REFRIGERATION SYSTEMS Filed May 9, 1949 3 Sheets-Sheet l VIII'II'IA LEE Pa EQW/N, 8

JOSEPH 5. G/Q/FF/rH, IN VEN TORS. HUEBNERBEEHLERWORREL.

HERZ/GJ CALDWELL, By A TTORNEYS.

' Filed May 9, 1949 Jan. 6, 1953 1.. R. ERWIN ETAL 2,624,181

MEANS AND METHOD OF CONTROLLING REFRIGERATION SYSTEMS 3 Sheets-Sheet 2 ZEEPOY EPA/NV,

JOSEPH 5. @P/FF/ 7//,

IN VEN TORS.

HUEENER, BEEHLER, WORREL,

HEPZ/G 8 CALDWELL, By ATTORNEYS.

Jan. 6, 1953. L. R. ERWIYN ErAL 2,624,131

MEANS AND METHOD OF CONTROLLINGREFRIGERATION SYSTEMS Filed May 9, 1949 Q 5 S SheQtS-Sheet a,

Lax-20y 52mm, & Josmu B. GE/FF/TH,

IN VEN T 0R5.

Patented Jan. 6, 1953 MEANS AND ME'IHO REFRIGERATI Lee Roy Erwin, Monrovia, and Pasadena, Calif., assignors Equipment, Inc., Cleveland,

of Delaware D 0F CONTROLLING 0N SYSTEMS Joseph B. Griffith, to Affiliated Gas Ohio, a corporation Application May 9, 1949, Serial N0. 92,102

8 Claims.

Our invention relates to the means and method for controllin refrigeration systems, and has particular reference to the means for controllin an expansion valve.

The standard-type compressor refrigerator system usually comprises a compressor, a condenser,

a receiver and an evaporator coil having an expansion valve positioned between the receiver and the evaporator coil to control the flow of liquid refrigerant into the evaporator coil.

vThe expansion valve is essentially a diaphragm-operated valve which is responsive to differences-in pressure on opposite faces of the diaphragm, one side of the diaphragm being responsive to the pressure in the refrigerant line; the other side being responsive to pressure from a temperature bulb positioned at some point in th refrigeration system which is used to control the admission of liquid refrigerant into the evaporator.

The usual position for the temperature bulb is adjacent the exhaust or suction line in heat transferring relation.

Due to the fact that the evaporator has a much lower pressure than the compressor side of the expansion valve, the refrigerant tends to boil at arelatively low temperature and in so doing, absorbs relatively large quantities of heat from the surrounding medium. As the boiling refrigerant progresses through the evaporator, it reaches a point of saturation, that is, where all liquid has boiled and become gas. From that point on, the gas begins to be superheated, that is, the temperature rises above the boiling point. It is usually this superheated exhaust gas that is applied to the temperature bulb to control the expansion valve.

In case of increasingly heavy demand, it will readily be seen that the point in the evaporator where saturation is reached, progresses upstream in the evaporator and the gases passing the point adjacent the temperature bulb are superheated to a greater degree, thereby causing the expansion valve to open and admit more liquid refrigerant into the system until the superheated gases are dropped back to the predetermined setting of the expansion valve, at which time the expansion valve closes.

Some systems are designed with a reservoir for liquid refrigerant between the expansion valve and the evaporator, and in such cases it is usually highly desirable to maintain a constant level of fluid therein. In such installations, the use of the standard-type control means is unsatisfactory. There is usually sufficient lag betweenthe responsive bulb temperature 'of the superheated gases and the demand of the refrigeration system that the expansion valve either closes tooslowly allowing the liquid level to run too high, or opens too slowly thereby allowing the reservoir to run dry.

One of the objects of our invention is to provide a control means which is modulated and subjected to a substantially instantaneous reaction upon a changing load demand for the refrigeration system.

Applicants are aware that others have attempted to maintain substantially constant liquid levels, but such endeavors have usually taken the form of mechanical float valves. Such valves are not entirely satisfactory because any piece of mechanical equipment is subject to failure, and being positioned insid of the evaporator unit, would be difficult to reach for repair and maintenance.

A further object of our invention is to provide a control unit which has no mechanical moving parts and which is readily available for maintenance and repair should the same be necessary.

We have found that a much more effective means for controlling the level of liquid refrigerant in the receiver consists in placing a temperature responsive bulb in contact with the liquid refrigerant in the receiver. A temperature responsive bulb in such position becomes immediately responsive to the level of the liquid refrigerant. It, however, becomes necessary to supply heat to the vapor system of the temperature responsive bulb from some source in order to operate the expansion valve. This can be done most conveniently by placing the temperature also in communication with the exhaust gases in the suction lineor by subjecting the capillary tube connecting the expansion bulb to the expansion valve to some independent and constant source of heat. It is, therefore, among the objects of our invention to provide a means and method for controlling the level of liquid refrigerant in a flooded coil refrigeration system which is immediately responsive to the liquid refrigerant level and which actuates the expansion valve also in response to an independentsource of heat or the superheat contained in the suction line.

It is' also a further object of our invention to provide a control unit adapted to actuate the expansion valve in response to temperature changes in both the suction line and a refrigerant receiver between the expansion valve and the expansion or evaporator coil A further object of our invention is to provide -ample only and not limitation.

pansion valve l3, and an adapted to interrupt the flow a method of controlling a pressure responsive expansion valve in a refrigeration system by subjecting said valve to the sum of the vapor pres-.

sures generated in response to the temperature of refrigerant entering the expansion coil and the refrigerant in the suction line being discharged from the coil.

Other and further objects and advantages of our invention will become apparent from the drawings and the specifications relative thereto.

In the drawings:

Figure 1 is a schematic illustration of a refrigerating system having a control embodying the principles of our invention.

Figure 2 is a partial sectional View showing the details of one form of our control.

Figure 3 is a sectional view taken on line 3-3 of Figure 2.

Figure 4 is a view similar to Figure 2 showing a modification of our invention.

Figure 5 is a similar view showing a further modification of our invention.

Figure 6 is an enlarged fragmentary sectional view of a further modification of our invention.

Figure 7 is a view taken on line of Figure 6.

Figure 8 is an enlarged fragmentary sectional elevation of a further modification of our invention showing the capillary tube subjected to an independent source of heat.

Figure 9 is a similar view showing a modification in the details of inserting the temperature responsibe bulb into the receiver.

We have illustrated our invention in connection with a refrigerator system, such as is disclosed in the co-pending application of William G. Cartter and J. Richard Ewell, filed on the 24th day of January, 1949, Serial No. 72,372. Whereas, we are illustrating our invention in connection with the system disclosed in said copending application, it is to be understood that such disclosure and explanation is by way of ex- It shall be understood that our control system is applicable to any type of refrigeration wherein it is desired to maintain a fairly constant level of refrigeration liquid in a reservoir between the expansion valve and the evaporator coil.

The system comprises sor I0, a condenser |I,

essentially a compresa receiver l2, an exevaporator unit, designated generally M. A suction line |5 communicates between the exhaust of the evaporator unit and the compressor.

The evaporator unit |4 comprises essentially a primary coil 20, a superheat coil 2| and a cup or refrigerant reservoir 22.

For the purposes of explaining the present invention, it is necessary only to explain that in such a system as is illustrated herein it is highly desirable to maintain a substantially constant level for liquid refrigerant 23 in the reservoir 22.

As will be seen in Figure 2, we have provided an expansion valve, designated generally l3, having an inlet 25, a discharge 26 and a valve 21 of refrigerant from the inlet to the discharge 26. The valve 21 is mounted on a stem 28 and is controlled by a diaphragm 29. The valve is preloaded by means of a compression spring 30. It will, therefore, be apparent that the position of the valve 27 will be responsive to the force of the spring 30, the pressure in the discharge 26 and the pressure on top of the diaphragm 29.

Pressure on top of the diaphragm 29 is regulated by means of a temperature responsive bulb 3| which is in communication with the upper surface of the diaphragm 23 by means of a capillary tube 32. The pressure system including the conduit or capillary tube 32 and the bulb 3|, contains a vapor. The volume of the tube 32 is so small that the pressure in the conduit is determined almost entirely by the mean temperature of the vapor in the bulb 3|. While under very cold operating conditions a portion of the vapor may condense on the walls and at the bottom of the bulb 3|, the system is essentially a gas or vapor system.

The structure so far described is more or less standard. However, in a standard system, the temperature responsive bulb 3| is placed adjacent the suction line 5 and on the outer surface thereof. It has been noted that such standard placement of the temperature responsive bulb 3| is not entirely satisfactory because of the delayed action in response to varying refrigeration loads.

In order to overcome this objection, we have positioned the temperature responsive bulb 3| so that it is responsive to the temperature of the liquid refrigerant in the reservoir 22, as well as the temperature of the superheated gases in the suction line l5. In order to accomplish this, we have provided a cylindrical member 35 formed with inturned annular flanges 36 and 31 which defines an annular chamber 38 in direct communication with the passageway of the suction line l5.

The inturned flanges 36 and 31 define apertures in axial alignment through which a tube 39 is disposed in a gas-tight relation. It will readily be seen that the tube 39 will rapidly assume the temperature of the gases in the suction line I5 because the gases flow in intimate contact with the outer walls of the tube 39.

The top of the receiver 22 is formed with an aperture 42 through which the lower end of the tube 39 is disposed so that the lower end which is closed extends downwardly into the liquid refrigerant 23. The temperature responsive bulb 3| is disposed inside the tube 39 and extends substantialiy the full length thereof so that a portion of the bulb is responsive to the temperature of the suction line gases and also to the temperature of the liquid refrigerant in the accumulator 22. In this manner the pressure exerted on the diaphragm 29 is dependent on the sum or net value of the pressures created by the two temperature regions at the bottom and top of the bulb 3| respectively. For example, under normal operation the bottom portion of the bulb 3| in contact with the liquid refrigerant 23 is generally colder than is the upper portion which is in contact with the suction line l5. Should the level of liquid 23 drop, the bottom portion of the bulb 3| would become warmer, thereby increasing the pressure in the pressure system including the tube 32, even though the upper portion in contact with the pipe I5 remains unchanged in temperature. This increase in pressure creates a wider opening at the valve 21 admittin more liquid to the reservoir 22, thereby raising the level to its previous point.

In similar manner, should the temperature in the upper region of the bulb 3| which is respon- |5 increase, the pressure in the tube 32 will go up as before, even though the liquid level in the reservoir 22 and hence the temperature in the bottom of the bulb 3| remains unchanged.

A similar although converse operation is effected upon drop in temperature in the suction line I5, or upon rise in liquid level 23.

It is thus seen that the valve I3 is made continually responsive to both the temperature at the inlet of the evaporator 14, in this case to the liquid level 23, and to the temperature at the outlet of the evaporator M, i. e., the temperature in the suction line l5. Each of the two regions is effective tocontrol the valve is independentlyof the temperature in the other region.

Due to the fact that the temperature of the gases in the suction line I5 tends to lag behind the load demand ofthe refrigeration system, the expansion valve lags behind such loads when it is dependent solely upon the temperature of the suction line for its control. By making the temperature responsive bulb 3 I responsive to the temperature of the suction line gases and to the temperature in the accumulator 22, a modulating action is obtained.

As the demand for refrigeration is increased, the level of the liquid refrigerant 23 in the reservoir 22 tends to fall thereby exposing more of the tube 39 to contact with the gases in the reservoir 22 rather than the liquid refrigerant. Such action has animmediate effect on the expansion valve because of the slower rate of heat transfor between gases and metals as compared with liquid to metal and the consequent effect on the expansion bulb, which permits the discharge of more liquid refrigerant into the reservoir 22, thereby tending to raise the level of the liquid 23, and in raising the liquid subjects the tube to the temperature of the liquid refrigerant, thereby tending to close the valve 21. However, the temperature of the gases in the suction line IS increases when the load on the refrigerating system increases so that the action of the temperature of the liquid 23 tending to close the valve and the action of the superheated gases in the suction line tending to open the valve, create a stable condition and result in the valve finding a balance point. This arrangement not only results in an immediate response to load changes, but also results in a modulating action which tends to balance the valve at the correct open setting rather than having it either full open or full closed, as is usually the case where the temperature responsive bulb is merely responsive by conduction to the heat in the suction line.

Our invention involves a method of controlling a pressure responsive expansion valve of a refrigeration system, which comprises the steps of placing a quantity of vapor in heat-communicating relation with refrigerant entering the expansion coil of said refrigerating system, placing a second quantity of vapor in heat-communicating relation with the refrigerant being exhausted from said coil, and communicating the sum of the pressures of said vapors to said pressure responsive expansion valve for actuation thereof.

Figure 4 illustrates a modification of the control system shown in Figure 2. In the modification shown in Figure 4, we have eliminated the tube 39 and have disposed the cylindrical member 35 through the top of the receiver 22 and have extended the temperature responsive bulb 3! through the annular chamber 38 and into-the reservoir 22.

It will be apparent that such an arrangement results in a more immediate response to temperature changes than is the case in the structure shown in Figure 2. However, the structure shown in Figure 2 is preferred because of the simplicity of sealing the engagement between the tube 39 v the tube 39 and the aperture 42.

and between These parts can readily be welded together in such a mannor that .gas cannot escape therefrom. It has been found that even a slight air gap between the tube 3| and the walls of the tube 39 does not materially affect the temperature response, so that even though the response of the bulb pressure to temperature changes is slower in the first embodiment, the differenceis not sufficient to warrant the use of the modification of Figure 4 except in special circumstances where a highly sensitive response is essential.

Figure 5 illustrates a further modification in that we have substituted the temperature responsive bulbs 50 and 5| in place of the single temperature responsive bulb 3|. The temperature responsive bulb 50 is directly in communication with the gases in the suction line l5 and immediately responds thereto. The bulb 5| is inserted inside of the reservoir 22 and is in direct contactwith the liquid 23 and the gases in the reservoir 22 and, therefore, is immediately responsive to changes in temperature therein. The two bulbs 50 and 54 are connected in series by means of a capillary tube 52.

The type of construction illustrated in Figure 5 has certain disadvantages over the structure shown in Figure 2, namely, in the probem of sealing the parts against leakage of air and yet so arranging the assembly that the parts may be readily removed for repair. and maintenance.

However, the structure shown in Figure 5 may be preferred in some installations because, as will be readily apparent, the chamber 35 and the bulb 50 need not be placed immediately adjacent the reservoir 22 as is the case of Figure 2.

The structure shown in Figure 5 illustrates the basic principles of our invention; namely, that the diaphragm of the expansion valve 32 is responsive to the sum of the pressures in the bulbs 50 and 5| which are controlled by the temperature of the surrounding medium. Therefore, the expansion valve is responsive to temperature both in the reservoir and in the suction line, which. as has been heretofore explained, gives a modulating action to the valve tending to stabilize it and to give an immediate response to load demand.

In Figures 8 and 9, we have illustrated a further modification of our invention wherein the temperature responsive bulb is positioned in heattransferring relation with the liquid refrigerant contained in the receiver and showing the capillary tube connecting the temperature responsive bulb to the expansion valve but subjected to an independent source of heat rather than the superheat of the suction line. Like reference nu merals indicate like parts of the other forms.

In the modification illustrated in Figure 8, we have illustrated a temperature responsive bulb 15 connected to the expansion valve l3 by means of a capillary tube 16. A well 11 extends downwardly to approximately the surface of the liquid refrigerant 23 and the temperature responsive bulb I5 is disposed therein. A source of heat, such as an electric coil 18, is placed in heattransferring relation with the capillary tube 16.

Upon rising of the liquid level, the heat transference between the well 11 containing the temperature responsive bulb 15 becomes faster and the temperature in the bulb l5 and, consequently, the vapor pressure contained therein decreases to permit closing of the expansion valve [3. When the liquid level again falls below a critical and the annular flanges 36 and 31 point, the rate of heat transference from the temperature responsive bulb becomes insufficient to overcome the rate of heat application from the source of heat thereby raising the vapor pressure affecting the expansion valve to open the expansion valve and permit the now of liquid refrigerant into the receiver.

In this modification the valve 53 is responsive only to the level of liquid 23 in the reservoir 22, the outlet temperature in the suction line 21 having no effect on the valve. The purpose of the coil '18 is to maintain substantially constant temperature in the tube ll'; thereby protecting it from temperature change of the ambient air which would, even though the volume of the tube 16 is small, tend to introduce a pressure change upon the valve it. It has been found desirable to make the tube it in the form of a coil so as to lengthen the travel distance between bulb T and valve 13, thereby giving a cushioning effect to any sudden changes in temperature resulting from rapid rise or fall of the liquid level 23. The cushioning eifect introduces a slight time lag in the response of the valve 53 and tends to prevent hunting thereof.

Figure 9 illustrates a further modification insofar as the details of construction are concerned, namely, the well if has been eliminated and a packing gland 8E3 substituted therefor having an aperture 81 through which the expansion bulb it is disposed. A packing nut 82 is in threaded engagement with the packing gland and has a resilient gasket 83 positioned therebetween. Such a construction gives a more intimate contact between the temperature responsive bulb I? and the liquid refrigerant 23, which results in a more rapid reaction. Such a construction, however, may not always be desirable in that the bulb may not be replaced without first removing the refrigerant and releasing the pressure inside the receiver 22.

While we have herein shown and described our invention in what we have conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope or" our invention, which is not to be limited to the details disclosed herein, but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices.

Having described our invention, what We claim as new and desire to secure by Letters Patent is:

1. In a refrigeration system having an pansion valve, a reservoir to receive liquid refrigerant, an expansion coil in communication with said reservoir and a suction line adapted to exhaust gaseous r frigerant from said expansion coil, means responsive to temperature variations adapted to actuate said expansion valve, said means comprising means defining a chamber in series in said suction line, a tubular member extending through said chamber and into said reservoir, a bulb containing a vapor adapted to vary the pressure in said bulb in response to temperature variations disposed in said tubular member, and a capillary tube communieating the pressure from said bulb into said expansion valve for actuation thereof.

2. In a refrigeration system having an expansion valve, a reservoir adapted to receive liquid refrigerant, an expansion coil in communication with said reservoir and a suction line adapted to exhaust gaseous refrigerant from said expansion coil, means responsive to temperature variations adapted to actuate said expansion valve, said means comprising means defining 2.

chamber in series in said suction line, a tubular member extending through said chamber and into said reservoir, said tubular member having a closed bottom and an open top, a bulb containing a vapor adapted to vary the pressure in said bulb in response to temperature variations disposed in said tubular member, and means communicating the pressure from said bulb into said expansion valve for actuation thereof.

3. In a refrigeration system having an expansion valve, a reservoir adapted to receive liquid refrigerant, an expansion coil in communication with said reservoir and a suction line adapted to exhaust gaseous refrigerant from said expansion coil, means responsive to temperature variations adapted to actuate said expansion valve, said means comprising means defining a chamher in series in said suction line, temperature responsive to pressure generating means disposed through said chamber and into said liquid refrigerant reservoir and responsive to the respective temperatures thereof, and means communicating the pressure from said pressure generating means into said expansion valve for actuation thereof.

l. In a refrigeration system having an expansion valve, a liquid refrigerant reservoir adapted to receive liquid refrigerant from said expansion valve and a suction line adapted to exhaust gaseous refrigerant from said system, said expansion valve being formed with a diaphragm actuable by pressure differentials across its face to control said expansion valve, temperature responsive pressure generating means in heat transferring relation with said gaseous refrigerant in said suction line, and temperature responsive pressure generating means in heat transferring relationship with the interior of said reservoir, the diaphragm of said expansion valve being responsive to the sum of the pressures in each of said pressure generating means.

5. A method of controlling a pressure responsive expansion valve, which is responsive to vapor pressure, of a refrigeration system in which there is an expansion coil having an inlet in communication with said expansion valve for the introduction of refrigerant into said coil and a discharge comprising the steps of placing a quantity of vapor in heat-communicating relation with refrigerant entering said coil, placing a second quantity of said vapor in heat-communicating relation with the refrigerant being discharged from said coil, and communicating the sum of vapor pressures generated by said vapors to said expansion valve for actuation thereof,

Refrigeration control apparatus comprising, in combination in a refrigerant system, an expansion valve, a liquid refrigerant reservoir connected to said valve to receive liquid refrigerant therefrom, an evaporator communicating with said reservoir to receive refrigerant therefrom, a suction line connected to said evaporator to withdraw vaporized refrigerant therefrom, and a vapor-containing conduit having a portion thereof disposed in said reservoir adjacent the surface of the liquid therein and having a portion disposed in heat transfer relation with said suction line, said conduit communicating with said valve to actuate the same in response to vapor pressure in said conduit, whereby the position of said valve is determined both by the liquid level in said reservoir and by the temperature of refrigerant withdrawn through said suction line.

7. Refrigeration control apparatus comprising,

in combination in a refrigerant system, an extion of refrigerant temperature both at said pansion valve, a reservoir connected to receive inlet and at said outlet. liquid refrigerant from said valve, an evaporator communicating with said reservoir to receive re- LEE ROY ERWIN. frigerant therefrom, and a vapor-containing con- 5 JOSEPH B. GRIFFITH. duit disposed vertically, partially in and partially out of the liquid refrigerant in said reser- EFERENCES CITED voir and connected to said valve to actuate the The foll wing efe n e are f record in the same in response to vapor pressure in the confil of this patent; duit, whereby the position of said valve is made 1 sensitive to liquid level in said reservoir. UNITED STATES PATENTS 8. Refrigeration control apparatus comprising, Number Name Date in combination in a refrigerant system, an ex- 1,985,617 Morton Dec. 25, 1934 pansion valve, an evaporator having an inlet 2,0355% Williams Mar. 31, 1936 communicating with said valve and an outlet, 15 2,078,966 Newill May 4, 1937 a pressure conduit containing fluid completely 2,133,959 Buchanan Oct. 25, 1938 in vapor phase connected to said valve to actu- 2,320,055 Stickel -1 May 25, 1943 ate the same in response to vapor pressure in 2,539,062 Dillman Jan. 23, 1951 the conduit, a portion of said conduit being (115- OTHER REFERENCES posed in heat transfer relation with said inlet, 29 and another portion of said conduit being disposed in heat transfer relation with said outlet whereby the pressure in said conduit is a func- Audels Refrigeration and Air Conditioning Guide, Audel and Company, publishers, 49 West 23rd Street, New York 10, New York, p. 951.

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