US2944411A - Refrigeration system control - Google Patents

Description

July 12, 1960 w. L. MCGRATH 2,

REFRIGERATION SYSTEM CONTROL Filed June 10, 1955 2 Sheets-Sheet 1 FIG. I

IO M 55 In-" FIG. 3

INVENTOR. WILLIAM L. MC GRATH 'July 12, 1960 w. L. MCGRATH I 2,944,411

' REFRIGERATION svs'rm conmoz.

Filed June 10, 1955 2 Sheets-Sheet 2 IN V EN TOR.

WILLIAM L. MC GRATH BY WJ'M ATTORNEY.

2,944,411 o 7 REFRIGERATION SYSTEM CONT 'oL William L. McGrath, Syracuse, N. assignor to Carrier Corporation, Syracuse, N.Y., a corporation of Dela are Filed June 10, 1955, Ser. No. 514,481 V 14 Claims. (11. 62-196) This invention relates to refrigeration systems of the type using a mechanical compressor. More specifically,

this invention relates to a control for a refrigeration system wherein operation of the system is controlled between predetermined limits of evaporator temperature.

Refrigeration systems of the type under consideration are often used in air conditioning equipment such as room air'conditioners or the like. It is important that the sys tem be'constructed so'that operation thereof above a predetermined evaporator pressure, that corresponding toa 7 temperature of about 50 F., is prevented. Operation United States Patent 4 2,944,411 Patented July '12, 1960 ice.

condenser, for the purposes of this invention it may be connected to any location in the high side of the systemcapable of providing a source of uncondensed gas. Lo- 'cated in the line 17 is a normally closed constant pressure expansion valve 18.

The-constant pressure expansion valve '16 is designed so as to close when the pressure in the evaporator is such to indicate that the evaporator temperature is above a preselected value say 50" F. Therefore, flow of refrigerant to the evaporator is completely prevented. This permits the pressure in the evaporator 10 fall and obviate a situation where the compressor motor may become overloaded. When the pressure in the evaporator falls to a preselected point corresponding to an evaporator temabove this design evaporator temperature causes the compressor to overload and the motor driving the compressor may burn out or fail to operate through an overload protection device. Operation of the system at an evaporator pressure corresponding to a temperature below 28 F;

is also unsatisfactory because frost may accumulate on the evaporator coil and prevent eflicient operation of the.

system.

Accordingly, it provide a control for the system which will maintain operation of the system between predetermined temperature limits. This isv accomplished in one instance by. providing valve means in the system, responsive to evaporator pressure which will pass refrigerant either in the liquid or gaseous states, or will throttle off the flow .of refrigerant completely. 7. 7 i

The system under consideration includes theusual components such as an evaporator, a suction line, a compressor, a discharge line, a condenser, a liquid line connecting the condenser and the evaporator, and an expansion member located in the liquid line to throttle the flow of refrigerant to the evaporator, modified to include a lineconnecting the expansion member with asource of uncondensed gas. Other objects and advantages of the invention will be apparent upon the consideration of the ensuing specification and drawings, in which 7 I Figure 1 illustrates a refrigeration system equippedlto function in the mannencontemplated by this invention;

Figure 2 is asectional view through the expansion member constructed to function in the same manner as the system depicted in Figure 1, when included in a con-. ventional refrigeration system;

Figure 3 is a modification of the valve member shown in Figure 2; W I J Figure 4 is a schematic view. of a refrigeration system equipped with the expansion member illustrated in Figure 2; and

Figure 5 is a equipped with the valve member shown in Figure 3.

Referring more particularly to the drawings, it can be seen that Figure 1 illustrate a conventional refrigeration system including a compressor 10, and a discharge line 11 permitting flow of compressed gaseous refrigerant from thecompressorto condenser 12. Aftef the refrigerant has been converted to the liquid phase in the condenser, as it is passed in heat exchange relation with a cooling medium, flow thereof through capillary 13 and is thechief object of this invention'to perature of, for illustration, 28 F., the constant pressure expansion valve 18 openspermitting flow of gaseous refrigerant or a mixtu re of gaseous and liquid refrigerant to the evaporator through by-pass .line' 17. This raises the pressure inthe evaporator to a temperature above the minimum so as to prevent an abnormal accumulation of frost on thevcoil. When the pressure in the evaporator is such toindicate a temperature within the range of operation indicated above, the system functions in the same manner as a system equipped with an expansion member having a fixed orifice, such as a capillary.

Referring more particularly to, Figure 2, there is shown a construction that may be' used in a system illus-' trated in Figure 1 to take the place of valves 16 and 18 as well as capillary 13. The valve 20 shownin Figure 2 includes a casing 21, a horizontal partition 22 and a vertical partition23- connecting the horizontal partition with the bottom wall of the casing. This arrangement divides the interior of the'valve body into three compartments or chanrbers, 2 4, 25, and 26. The compartment 24 is provided with an opening 27 serving as a valve seat in the horizontal partition 22 permitting corn'municationbe' tween compartment 24- and the compartment 26,- Compartment 25 communicates with compartment 26 through an opening 28 serving asta valve seat and is provided with an opening "30 normally permitting'the flow of gaseous,

refrigerant from a location either in the compressor discharge line' of the condenser which will permit flow of the gaseous or uncondensed refrigerant or a mixture of,

gaseous and liquid refrigerant tothe Valve. Compartment 24contains an opening'29 for the flowof liquid refrigerant from the condenser to the compartment. Compartment 26 is provided with an opening 31 permitting 1 flow of refrigerant from thetvalve 20 to theevaporator;

schematic'view of a refrigeration system 7 Valve members 32 and 33, preferably in the formof balls or spheroids, are arranged in chambers 24 and 25 respectively to-control the openings 27 and 28. Spring members 34 and 35, one end of which is supported on the bottom wall of the valve, continuously urge the valve.

members 32 and 33 to the positions shown in Figure 2,

whereinthe valve members prevent passage of refrig-L erant from either of the compartments 24 and 25 to] the chamber '26. I

., Included in the compartment 26 is a diaphragm mem-f .ber 37 disposed transversely of the chamber. The periph-" eral portion of the diaphragm is secured to theside wall of the valve. Spring member 38 is arranged to apply; 7

I throughadjusting screw 39 and mounting member 40, a

' predeterminedpressure upon the upper-surface of'the diaphragm through cradle 41. This force is opposed by evaporator pressure acting against the under surface of the diaphragm. Secured to the underside of the diaphragm is an operating member 42 in the form of a conn'ectingrod 43havi'ng, pivotally secured thereto, an inverted U-shaped'member 43. Depending legs 44 of the inverted U-shaped member 43 are arranged to bear against the valve members 32 and 34 seated in openings 27 and 28. In constructing the valve it is important that there be a'difference in the strength of the springs 34 and 35 so that spring 35 will have more resistance to deformation or compression than spring 34 by an amount substantially equivalent to the range of evaporator temperatures chosen. In other words, when the diaphragm is subjected to pressure, indicating an evaporator temperature of approximately 50 F., the resultant of the forces acting on the diaphragm will force" the leg 44 directly above valvemember 32 into contact with the valve and will be sufiicient to move'the valve member against the action of the spring 34 to permit flow of liquid refrigerant through opening 29, into the compartment 24, and then into the compartment 26 through the opening 27. The refrigerant 'flows from the'compartment 26 to the evaporator through the opening 31. The operating rod '43 is pivotally mounted .so that, While the action of spring 35 in compartment will be sufficient to resist movement of the valve 28, the spring 34 will permit the movement ofvalve 27 to obtain the desired flow of refrigerant. 'To limit downward movement of the valve members '27 and 28, members 3h and 40' having threaded stern portions are mounted as shown in Figure 2. The exactpositioning of the members 39' and 40' is preselected thereby determining in advance the effective size of the opening between compartments24 and 26 in the first instance and compartments 25 and 26 in the second instance once the conditions necessary for opening the ports 27 and28 have been satisfied. Thus for illustration, when the evaporator pressure indicates an evaporator temperature below 50 F. the leg 44 of the inverted U-sha'ped member-43 forces the valve 32 against thejaction of the spring 34 into contact with upper end or stop member 39'; the refrigeration system functions in a manner similar to a system having a fixed orifice as an expansion member. in the line connecting the condenser and the evaporator. Thereafter a normal flow of refrigerant to the'evaporator through the expansion member occurs. In other words a rate of refrigerant flow normal for a system having such an expansion member occurs.

When the evaporator pressure drops to the lower limit of the range of operation desired, the resultant of the forces involved will cause spring 35 to be compressed so as to permit flow of gaseous refrigerant through opening into compartment 25 and through opening 28 to the compartment 26. Under these circumstances the flow of gaseous refrigerant and the liquid refrigerant directly to the evaporator will prevent further drop in evaporator pressure and the operating temperature corresponding thereto. This, of course, will prevent the accumulation of frost which would occur at low operating evaporator temperatures. 7

When the evaporator temperature reaches the upper limit of the preselected range, the pressure in chamber 26 rises to a value which when added to the pressure exerted by springs 34 and overcomes the action of spring 38 and the two ports 27 and 28 are closed as shown in Figure 2. Under these circumstances no refrigerant flows to the evaporator. The pressure in the evaporator is gradually reduced by the action of the compressor until eventually the action of spring 34 is overcome and liquid refrigerant feeds to the evaporator'through opening 27.

Another embodiment of the invention is shown in Figure 3 wherein a construction sensitive directly to changes inevaporator temperature to contrpl passage of refrigran to h e a o o i s o n. The e p as aa her 50 is shown composed of an upper section 51, formed of a material such as brass having a relatively high coefiicient of expansion, jointed to a lower section 52 also formed of the same material. Mounted in the upper section is an operating rod 53 formed of a material having a low coefficient of expansion such as Invar. An adjusting member 54 having a handle 55 and a threaded stem 56 is mounted in the top of the upper section and connected to the top of the oper t g rod "53 with the pin and slot type connection. The lower end of the rod 53 ispivotally connected to a U-sh'aped saddle 57 having a first leg 58 and a second shorter leg 59 connected by a cross piece 60.

Disposed within the lower section SZ'of the member 50 is a horizontal partition 62 having openings 63 and 64 serving as valve seats and permitting communication between a first compartment 65 defined by the horizontal partition and a vertical partition 68 and a second compartment 66,'and between a third compartment 67 adjacent compartment 65 and the compartment 66. Valve members 69 and'70 in the form of spheroids are urged to the positions shown in Figure S bysprings 71 and 72 respectively. In this embodiment the springs may be of the same strength. The stop members 73 and 74 having threaded stems of the lower section, oifer, at their ends, abutments for limiting downward movement of the valve memberspnder the influence of the operating rod 53 in a manner to be later described. An opening 75 in casing 52 serves to connect compartment 65 with'a line extending to the condenser so that liquid refrigerant flows to the expansion member 50. Opening 76 permits communication between compartment 67 and a portion of the condenser containing uncondensed refrigerant. 'For 'the purposes of this invention compartment 67 may be connected to any point on the high side of the refrigera tion system having gaseous refrigerant. Opening 77 serves to connect the expansion member 50 with a line leading to the evaporator. Refrigerant flow throughthe expansion member occurs as follows, through either opening or 76 or both, through either opening 63 or 64 or both, out through opening 77 to the evaporator. Springmember 78 is located on the upper surface of the horizontal partition 62 to engage a lateral extension 79 of the saddle member 57. Abutment member 80, opposes the action of spring member 78 to obtain a pivotal movement to be described later.

Considering the operation of the expansion member 50, it is contemplated that relative movement occurs between the brass section of the casing and theoperating rod in response to temperature variations of the refrigerant flowing through member 50. v'lhe refrigerant within the casing being at substantially'the same pressure as the evaporator, its temperature will'be substantially that prevailing in the evaporator. The rod 53 being secured to casing through adjusting member 54 moves with the casing as it expands or contracts in response tothetemperature variations. For example the parts are so constructed that when the evaporator temperature is above a preselected maximumsuch as 50 FJ-the casing expands to an extent that rod 53 .is moved outof engagement with either of the valves 69, 70. in response to 'a temperature reduction below the preselected maximum, contraction of the member 51, sufficient to cause movement of leg 58 of the saddle 57 into engagement .with valve 69, occurs. This action permits flow of liquid refrigerant from compartment 65 into compartment 66 .and through unrestricted opening 77 to the evaporator. Spring member 78 resists downward movement of the portion'of saddle member from which leg 59 depends, thereby causing pivoted movement of leg 58 into engagement with ball valve 69. w 7 V n n The parts are so constructed that a contraction of the casing 51, of an amount that would indicate an evaporator temperature of about 28 F., will cause the action of spring 78 to be overcome and the leg 59 to forcibly 5 engage the ball valve '70. This action in turn forces the ball valve 70 downwardly against the action of spring 72.

Thus, gaseous refrigerant flows into compartment 66to' supplement the refrigerant present therein by virtue of opening 63. The resulting mixture of refrigerant flows' The mixture 7 contains asubstantial amount of refrigerant in the gaseous to the evaporator in the usual manner.

state so that the evaporator pressure is prevented from falling below the predetermined low value, obviating the possibility of an accumulation of frost sufficient to impair eflicient operation of the cooling coil.

it will thus be obvious that, by the use of the invention described, operation of a refrigeration system between.

flow of substantially gaseous refrigerant from. the-jhigh pressure side of the refrigeration system to the evaporator, and means responsive toevaporator pressure corresponding to predetermined evaporator. temperature for controlling the eifectivearea of each opening.

2. The invention as described in claim 1 wherein said last mentioned means includes a valve assembly comprising a valve member and means urging said valve member to a position closing said inlets and aclinkage operable under the influence of evaporator pressure to oppose the valve member urging means. I I

3. The invention as described in claim 2' wherein said valve member urging means includes a helical spring with the spring engaging the valve member associated with the inlet permitting flow of liquidrefrigerant having less resistance to deformation than the spring associated with the valve member associated with the inlet permitting flow of gaseous refrigerant to the evaporator.

4. A refrigeration system comprising an evaporator; a compressor; a condenser and an expansion member connected to form a closed circuit for the flow of refrigerant, said expansion member having an outlet in communication with the evaporator, a first inlet normally admitting flow of liquid refrigerant} to the expansion member and a second opening .permitting flow of gaseous refrigerant to the expansion member, and means includ: ing two resilient elements each having a different resistance to deformation for controlling, in response to evaporator pressure, the eifective area of said inlets.

5. A refrigeration system including an evaporator; a compressor; a condenser-and an expansion member con; nected to form'a closed circuit for the flow of refrigerant, said expansion member being provided with an outlet in communication with the evaporator to permit flow of refrigerant thereto, and two inlets permitting flow of refrigerant into the expansion member, valves normally closing said inlets and means responsive to evaporator pressure for controlling the operation of the valves to regulate the flow of refrigerant to the expansion member.

6. The invention as set forth in claim 5 wherein one content in excess of the gaseous content in the refrigerant flowing into the other inlet.

7. The invention set forth in claim 6 wherein said last mentioned means includes an operating member having a first extension adapted to engage the valve associated with the first inlet and a second extension adapted to engage the valve associated with the second inlet.

8. The invention as set forth in claim 7 wherein said last mentioned means includes a movable diaphragm assembled within said expansion member and a connecting member pivotally connected tosaid diaphragm and rigidlyconnected to said operating member.

9. The invention as described in claim 5 wherein said refrigerant expanding means includes a housing formed of a material having a relatively high coefiicient of expansion, and an operating rod having a relatively low coefficient of expansion secured to the housing and movable therewith relative to the housing in response to evaporator temperature differentials.

10. The invention as described in claim 9 wherein the lower portion of said housing is provided with a horizontal partition and a vertical partition defining three separate compartments, two of the compartments being adjacent to one another and the third overlying the first two, the horizontal partition including openings therein permitting communication between the upper compartment and the two lower compartments.

11. The invention as described in claim 10 wherein the by-pass line permitting flow of supplemental refrigerant to the evaporator includes one of said compartments.

12. The invention as described in claim 11 wherein means are provided in said upper compartment for causing the operating rod to engage o'ne valve member for a predetermined period of time before engaging the other valve member.

13. In a refrigeration system including an evaporator, a compressor, a condenser, means for expanding refrigerant and lines connecting the system elements to form a closed circuit for the flow of refrigerant, control means,

7 including a by-pass line connecting the line between the mum evaporator operating temperature to prevent flow of refrigerant. to the evaporator.

14. In a refrigeration system the combination comprising an evaporator, a compressor, a condenser and an of said inlets permits flow of refrigerant having a gaseous expansion member interconnected to form a closed circuit for the flow of a refrigerant, said expansion member including a first inlet fo'r permitting flow of liquid refrigerant to the evaporator and a second inlet permitting flow of substantially gaseous refrigerant from the high pressure side of the refrigeration system to the evaporator, and means responsive to an evaporator operating characteristic of a predetermined magnitude for controlling the elfective area of each opening.

References Cited in the file of this patent UNITED STATES PATENTS 2,252,300 McGrath Aug. 12, 1941 2,344,215 Soling et a1 Mar. 14, 1944 2,614,394 McGrath Oct. 21, 1952 2,675,684 Shoemaker Apr. 20, 1954 2,694,904 Lange et a1 Nov. 23, 1954 2,701,455 Kleist Feb. 8, 1955 2,701,688 Dillman Feb. 8, 1955 2,702,671 Carter Feb. 22, 1955 2,742,765 Anderson Apr. 24,

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