US3320763A

US3320763A - Controls for refrigeration systems

Info

Publication number: US3320763A
Application number: US508736A
Authority: US
Inventors: James R Harnish
Original assignee: Westinghouse Electric Corp
Current assignee: YORK-LUXAIRE Inc A CORP OF DE
Priority date: 1965-11-19
Filing date: 1965-11-19
Publication date: 1967-05-23
Anticipated expiration: 1984-05-23
Also published as: DE1501175B2; DE1501175A1; DE1501175C3; GB1126496A; FR1516006A

Description

y 1967 J. R. HARNISH 3,320,763

CONTROLS FOR REFRIGERATION SYSTEMS Filed Nov. 19, 1965 FIG'L IO EVAPORATOR COR ACCUMULATOR JCONDENSE con.

c --HERMET|C l5 COMPRESSOR 5| 2 24 m 55 l A 59 BALL |NVENTOR= JAMES RHARNISH, BYW 17. 9%

ATTORNEY United States Patent ()fifice 3,329,753 Patented May 23, 1967 3,320,763 CONTROLS FOR REFRIGERATION SYSTEMS James R. Hamish, Staunton, Va., assignor to Westinghouse Electric Corporation, Pittsburgh, 'Pa., 2 corporation of Pennsylvania Filed Nov. 19, 1965, Ser. No. 508,736 9 Claims. (Cl. 62-197) This invention relates to controls for refrigeration systems.

In my copending application, Ser. No. 447,008, filed Apr. 9, 1965, now Patent No. 3,264,837, there is disclosed a refrigeration system using a sub-cooling control valve as an expansion valve to over-feed an evaporator during normal operation, the sub-cooling control valve being shunted by an automatic expansion valve responsive to the pressure of the refrigerant leaving the evaporator, for preventing the evaporator from becoming starved during abnormal operation when the condensing pressure is insufiicient to properly operate the sub-cooling control valve. Such valves are not readily available for relatively large refrigeration systems, and if available, their costs would be relatively high.

A feature of this invention is that a relatively small, sub-cooling control valve operates as a pilot valve to control a relatively large expansion valve during normal operation, with the sub-cooling control valve shunted by a relatively small automatic expansion valve which operates as a pilot valve to control the expansion valve during abnormal operation when the condensing pressure is insufiicient to properly operate the sub-cooling control valve.

It is conventional to use a solenoid-operated valve in the high pressure liquid line of a refrigeration system to provide positive liquid shut-off during shut-downs of the system. In a relatively large system, a relatively large shut-01f valve is required. Another feature of this invention is that a relatively small, solenoid-operated, liquid shut-off valve is used in the control line of the previously mentioned, relatively large expansion valve.

In a large refrigeration system, the over-load control setting of a compressor motor, and the high pressure cut-out setting, may be critical because of pull-down requirements during warm start-ups when the outdoor ambient temperature is relatively high, and one or both of such controls may turn the compressor motor off. Another feature of this invention is that a relatively small, automatic expansion valve responsive to the evaporator pressure, is located in the control line of the previously mentioned, large expansion valve, and operates t adjust the expansion valve to starve the evaporator for preventing excessive pressures during such warm startups.

An object of this invention is to use a relatively small, sub-cooling control valve to control a relatively large expansion valve in a refrigeration system.

Another object of this invention is to use a relatively small, automatic expansion valve to control a relatively large expansion valve in a refrigeration system.

Another object of this invention is to use a relatively small, sub-cooling control valve, shunted by a, relatively small, automatic expansion valve, to control a relatively large expansion 'valve in a refrigeration system.

Another object of this invention is to prevent excessive refrigerant pressures in a refrigeration system during warm start-ups at high outdoor ambient temperatures. This invention will now be described with reference to the annexed drawings, of which:

FIG. 1 is a diagrammatic view of a refrigeration system embodying this invention;

FIG. 2 is an enlarged side section of the automatic expansion valve of FIG. 1;

FIG. 3 is an enlarged, side section of the sub-cooling control valve of FIG. 1, and

FIG. 4 is an enlarged side section of the main expan .sion valve of FIG. 1.

A conventional, hermetic, refrigerant compressor C having an enclosed electric motor CM, is connected by discharge gas tube 10 to one end of condenser coil 11, the other end of which is connected by liquid tube 12, through a heat exchange coil which is not shown, within accumulator 13, to the inlet of main expansion valve 14. The outlet of the valve 14 is connected by tube 15 to one end of evaporator coil 16, the other end of which is connected by tube 17 to the top of the accumulator 13. The accumulator 13 is connected by suction gas tube 18 to the suction side of the compressor C. The components in the accumulator 13 are fully disclosed in the previously mentioned application.

The tube 12 is also connected between the accumulator 13 and the expansion valve 14 to tube 20 which is connected through valve 21 to the inlets of sub-cooling control valve 22 and automatic expansion valve 23 operating as pilot valves. The outlets of the

valves

22 and 23 are connected by tube 24 through solenoid-operated valve 25 to the top of piston chamber 26 of the main expansion valve 14.

The valve 23 has a diaphragm chamber '30 with a diaphragm 31 extending across its center. The interior of the chamber 30 below the diaphragm 31 is connected by capillary tube 32 to the tube 17. The valve 23 has a partition 34 extending across its interior between its inlet and outlet, with a valve opening 35 therein. A valve piston '36 below the opening 35, is connected by piston rod 37 to the center of the diaphragm 31. A coiled spring 38 extends between the center of the top of the diaphragm 31 and the top of the chamber 30, and biases the piston 36 towards open position.

The valve 21 is similar to the valve 23 except that it is adjusted to close at a different pressure as will be described later, and has a diaphragm chamber 39, the lower portion of which is connected by a capillary tube 40 to the tube 32.

The sub-cooling control valve 22 has a diaphragm chamber 41 with a diaphragm 42 extending across its center. It has a partition 43 extending across its interior between its inlet and outlet, with a valve opening 44 therein. A valve piston 45 above the opening 44 is connected by piston rod 46 to the center of the diaphragm 42. A coiled spring 47 extends around the rod 46 between the bottom of the chamber 41 and the top of the valve piston 45, and biases the piston 45 towards closed position. The interior of the chamber 41 above the diaphragm 42 is connected by capillary tube 50 toa conventional thermal bulb 51 in heat exchange contact with the tube 12 between the accumulator 13 and the coil 11. The interior of the chamber 41 below the diaphragm 42 is connected by capillary tube 52 to the interior of the tube 12 adjacent to the bulb 51.

As shown by FIG. 4, the piston chamber 26 of the main expansion valve 14 has a piston 55 slidable therein. A partition 56 extends across the interior of the valve 14 between its inlet and outlet and has a valve opening 57 therein. A valve piston 58 below the opening 57 is connected by piston rod 59 to the center of the piston 55. A coiled spring 60 extends between the bottom of the piston 58 and the bottom of the valve 14, and biases the piston 58 towards closed position. The piston 55 has a pressure equalizing passage 61 extending therethrough.

Referring now to FIG. 1, a solenoid 65 is connected to the valve 25 to open and close the latter. The compressor motor CM is connected to electric supply line L1, and through switch S1 of motor starter MS, and wire 66 to electric supply line L2. The starter MS is connected through switch TS of thermostat T, and

wires

67 and 68 to the lines L1 and L2. The solenoid 65 is connected by wire 69 and the wire 66 to the line L2, and is connected by wire I 76 and switch S2 of the starter MS to the line L1.

Operation When the thermostat T calls for cooling, it closes its switch TS which energizes the motor starter MS. The latter closes its switches S1 and S2. The closed switch S1 energizes the compressor motor CM, starting the compressor C. The closed switch S2 energizes the solenoid 65 which opens the valve 25. The compressor C supplies discharge gas through the tube 11) into the condenser coil 11. Refrigerant liquid flows from the coil 11 through the tube 12 and the heat exchange coil (not shown) within the accumulator 13, into the expansion valve 14 which meters refrigerant to the evaporator coil 16. Gas and unevaporated liquid from the coil 16 flow through the tube 17 into the accumulator 13. Gas separated from the liquid within the accumulator 13 flows through the suction gas tube 18 to the suction side of they compressor C.

The valve 21 is adjusted to be open during normal operation so as to permit liquid to flow from the tube 12 into the inlets of the

pilot valves

22 and 23. It may be set to start to close when the pressure of the refrigerant leaving the evaporator coil 16 in a system using F22 refrigerant increases, for example, above 84 p.s.i. as will be described later.

The pilot valve 23 is adjusted to be closed during normal operation when the evaporator pressure is normal, and to open when the evaporator coil 16 is about to become starved as will be described later.

During normal operation, the sub-cooling control valve 22 adjust the expansion valve 14 to meter refrigerant to the evaporator coil 16 at the rate at which refrigerant is condensed in the condenser coil 11 while maintaining, for example, F. subcooling at a condensing temperature of 100 F. An increase in the temperature of the liquid in the tube 12 at the bulb 51, acts through the bulb 51, the capillary tube 50 and the diaphragm 42 of the valve 22, to adjust the piston 45 of the valve 22 towards closed position, reducing the'liquid pressure above the piston 55 of the valve 14, and causing the valve piston 58 of the valve 14 to move towards closed position so as to back up more liquid within the condenser coil 11, for increasing the sub-cooling of the liquid. Increased liquid pressure in the tube 12 where the capillary tube 52 is connected-to the latter, acts through the tube 52 and the diaphragm 42 to adjust the valve piston 45 of the valve 22 towards open position, increasing the liquid pressure above the piston 55 of the valve 14, and causing the valve piston 58 of the valve 14 to move towards open position. For an increase in the rate at which refrigerant is condensed in the coil 11, if the valve 14 is not sufficiently open, liquid in the coil 11 will back up until the pressure is increased sutficiently or the temperature is reduced sufliciently to cause the valve 22 to adjust the valve 14 towards open position, and vice versa. When the condensing rate changes, the valve 22 readjusts the valve 14 accordingly, but the latter meters refrigerant to the evaporator coil 16 at the rate at which refrigerant is condensed in the condenser coil 11. The valve 14 continuously overfeeds the evaportor coil 16 as disclosed in the previously mentioned application.

During abnormal conditions, such as at very low outambient temperatures or other conditions resulting in abnormally low condensing pressures, the liquid subcooling at the bulb 51 may be insufiicient for the valve 22 to adjust the expansion valve 14.sufi"1ciently open to prevent the evaporator coil 16 from becoming starved. At such times, the pilot valve 23 responds through the capillary tube 32 to the resulting reduced pressure of the refrigerant within the tube 17 at the outlet of the evaporator coil 16, the reduced pressure below the diaphragm 31 of the valve 23, permitting the spring 38 to move the piston 36 to open position, supplying liquid above the piston 55 of the valve 14 to cause the valve piston 58 of the valve 14 to open sulficiently to provide sufiicient refrjgerant to the evaporator coil 16 to prevent it from becoming starved.

The bleed passage 61 in the piston 55 of the valve 14 permits pressure in the chamber above the piston 55 to equalize the evaporator pressure when the valve 22 or the valve 23 moves towards closed position, by flowing through the passage 61 :and the interior of the valve 14 into its outlet, thus permitting the spring 60 to move the valve piston 58 of the valve 14 towards closed position.

On start-ups of the system, when the latter is a water chilling system, at an outdoor temperature of, say F., the chilled water temperature may be 90 F. or even higher. This means that the compressor has to operate at very high suction pressures, and correspondingly high discharge pressures until the water has been chilled down to a temperature below 55 F. The condenser would be sized to operate at an outdoor air temperature of about F., but only when the temperature of thechilled water leaving the chiller is at, say, 50 F. Consequently, warm start-ups during high outdoor ambient temperatures, may result in the compressor motor being tripped out by an overload control or by a high pressure cut-out. The valve 21 prevents this. When the evaporator pressure increases above 84 p.s.i., this pressure transmitted by the capillary tube 40 to the interior of the diaphragm chamber 39 of the valve 21,.causes the valve 21 to throttle towards closed position, decreasing the quantity of liquid supplied to the

pilot valve

22 or 23 whichever is operating, and. causing the valve 14 to throttle towards closed position to starve the evaporator, thus preventing excessively high refrigerant pressures and compressor motor overload.

When the thermostat T is satisfied, it opens its switch TS, deenergizing the motor starter MS which opens its switch S1, stopping the compressor motor CM. At the same time, the switch S2 of the starter MS opens, deenergizing the solenoid 65 which closes the valve 25 in the control tube 24 of the expansion valve 14, shutting off the supply of liquid to the piston chamber 26 of the valve 14 so that the spring 60 closes the valve piston 58. of'the valve 14, providing positive shutoff when the system is turned off.

Since the valves 21., 22, 23 and 25 are in the liquid supply to the piston chamber 26 of the expansion valve 14, they can be relatively small valves, for example, three ton valves for controlling a one hundred ton valve 14.

While the invention has been disclosed as embodied in a non-reversible system having condenser and evaporator coils, it may be used in heat pumps, and in systems in which the evaporators are water or other liquid chillers, and/ or in which the condensers are liquid cooled.

What is claimed is:

1. In a refrigeration system having a compressor, a condenser, an expansion valve and an evaporator connected in series in a refrigeration circuit; a pilot valve having an inlet connected to said circuit between said condenser and said expansion valve to receive refrigerant liquid from said circuit, said pilot valve having an out let, said pilot valve having means including means responsive to the pressure and the temperature of the refrigerant liquid leaving said condenser for opening and closing said pilot valve, said expansion valve having a chamber connected to said outlet of said pilot valve for receiving refrigerant liquidv from said pilot valve 'when said pilot valve is open, and means including means responsive to the pressure of the liquid entering said 2. The invention claimed in claim 1 in which there is provided a second pilot valve having an inlet connected to said inlet of said first mentioned pilot valve and having an outlet connected to said outlet of said first mentioned pilot valve, and in which said second pilot valve has means including means responsive to the pressure of the refrigerant at said evaporator for opening said second pilot valve on a decrease in the pressure of the refrigerant at said evaporator and for closing said second pilot valve on an increase in the pressure of the refrigerant at said evaporator.

3. The invention claimed in claim 2 in which a liquid tube connects said inlets of said pilot valves to said circuit, in which a second liquid tube connects said outlets of said pilot valves to said chamber, and in which a third pilot valve is connected in one of said tubes, said third valve having means including means responsive to the pressure of the refrigerant at said evaporator for opening said third valve on a decrease in the pressure of the refrigerant at said evaporator and for closing said third valve on an increase in the pressure of the refrigerant at said evaporator.

4. The invention claimed in claim 3 in which means is provided for starting and stopping said compressor, in which a shut-off valve is connected in one of said tubes, and in which means is provided for closing said shut-01f valve when said compressor is stopped and for opening said shut-off valve when said compressoris started.

5. The invention claimed in claim 1 in which a liquid tube connects said inlet of said pilot valve to said circuit, in which a second liquid tube connects said outlet of said pilot valve to said chamber, and in which a second pilot valve is connected in one of said tubes, said second pilot valve having means including means responsive to the pressure of the refrigerant at said evaporator for opening said second pilot valve on a decrease in the pressure of the refrigerant at said evaporator and for closing said second pilot valve on an increase in the pressure of the refrigerant at said evaporator.

6. The invention claimed in claim 5 in which means is provided for starting and stopping said compressor, in which a shut-off valve is connected in one of said tubes, and in which means is provided for closing said shut-01f valve when said compressor is stopped and for opening said shut-off valve when said compressor is started.

7, The invention claimed in claim 1 in which means is provided for starting and stopping said compressor, ir which a liquid tube connects said inlet of said pilot valve to said circuit, in which a second liquid tube connect: said outlet of said pilot valve to said chamber, in whicl a liquid shut-off valve is connected in one of said tubes, and in which means is provided for closing said shut-ofi valve when said compressor is stopped and for opening said shut-off valve when said compressor is started.

8. In a refrigeration system having a compressor, a condenser, an expansion valve and an evaporator connected in series in a refrigeration circuit; a pilot valve having an inlet connected to said circuit between said condenser and said expansion valve to receive refrigerant liquid from said circuit, said pilot valve having an outlet, said pilot valve having means including means responsive to the pressure of the refrigerant at said evaporator for opening said pilot valve on a decrease in the pressure of the refrigerant at said evaporator and for closing said pilot valve on an increase in the pressure of the refrigerant at said evaporator, said expansion valve having a chamber connected to said outlet of said pilot valve for receiving refrigerant liquid from said pilot valve when said pilot valve is open, and means including means responsive to the pressure of the liquid entering said chamber for adjusting said expansion valve towards open position on an increase in the pressure of the liquid entering said chamber and for adjusting said expansion valve towards closed position on a decrease in the pressure of the liquid entering said chamber.

9. The invention claimed in claim 8 in which means is provided for starting and stopping said compressor, in which a liquid tube connects said inlet of said pilot valve to said circuit, in which a second liquid tube connects said outlet of said pilot valve to said chamber, in which a liquid shut-01f valve is connected in one of said tubes, and in which means is provided for closing said shut-off valve when said compressor is stopped and for opening said shut-off valve when said compressor is started.

References Cited by the Examiner UNITED STATES PATENTS 2,571,625 10/1951 Seldon 62225 3,023,591 3/1962 Tilney 6221O X MEYER PERLIN, Primary Examiner,

Claims

1. IN A REFRIGERATION SYSTEM HAVING A COMPRESSOR, A CONDENSER, AN EXPANSION VALVE AND AN EVAPORATOR CONNECTED IN SERIES IN A REFRIGERATION CIRCUIT; A PILOT VALVE HAVING AN INLET CONNECTED TO SAID CIRCUIT BETWEEN SAID CONDENSER AND SAID EXPANSION VALVE TO RECEIVE REFRIGERANT LIQUID FROM SAID CIRCUIT, SAID PILOT VALVE HAVING AN OUTLET, SAID PILOT VALVE HAVING MEANS INCLUDING MEANS RESPONSIVE TO THE PRESSURE AND THE TEMPERATURE OF THE REFRIGERANT LIQUID LEAVING SAID CONDENSER FOR OPENING AND CLOSING SAID PILOT VALVE, SAID EXPANSION VALVE HAVING A CHAMBER CONNECTED TO SAID OUTLET OF SAID PILOT VALVE FOR RECEIVING REFRIGERANT LIQUID FROM SAID PILOT VALVE WHEN SAID PILOT VALVE IS OPEN, AND MEANS INCLUDING MEANS RESPONSIVE TO THE PRESSURE OF THE LIQUID ENTERING SAID CHAMBER FOR ADJUSTING SAID EXPANSION VALVE TOWARDS OPEN POSITION ON AN INCREASE IN THE PRESSURE OF THE LIQUID ENTERING SAID CHAMBER AND FOR ADJUSTING SAID EXPANSION VALVE TOWARDS CLOSED POSITION ON A DECREASE IN THE PRESSURE OF THE LIQUID ENTERING SAID CHAMBER.