US20150267951A1 - Variable refrigerant charge control - Google Patents
Variable refrigerant charge control Download PDFInfo
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- US20150267951A1 US20150267951A1 US14/221,702 US201414221702A US2015267951A1 US 20150267951 A1 US20150267951 A1 US 20150267951A1 US 201414221702 A US201414221702 A US 201414221702A US 2015267951 A1 US2015267951 A1 US 2015267951A1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B45/00—Arrangements for charging or discharging refrigerant
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B13/00—Compression machines, plants or systems, with reversible cycle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2345/00—Details for charging or discharging refrigerants; Service stations therefor
- F25B2345/001—Charging refrigerant to a cycle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2345/00—Details for charging or discharging refrigerants; Service stations therefor
- F25B2345/003—Control issues for charging or collecting refrigerant to or from a cycle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2345/00—Details for charging or discharging refrigerants; Service stations therefor
- F25B2345/006—Details for charging or discharging refrigerants; Service stations therefor characterised by charging or discharging valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/05—Compression system with heat exchange between particular parts of the system
- F25B2400/053—Compression system with heat exchange between particular parts of the system between the storage receiver and another part of the system
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/05—Compression system with heat exchange between particular parts of the system
- F25B2400/054—Compression system with heat exchange between particular parts of the system between the suction tube of the compressor and another part of the cycle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/16—Receivers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/19—Pumping down refrigerant from one part of the cycle to another part of the cycle, e.g. when the cycle is changed from cooling to heating, or before a defrost cycle is started
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2600/00—Control issues
- F25B2600/25—Control of valves
- F25B2600/2519—On-off valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2600/00—Control issues
- F25B2600/25—Control of valves
- F25B2600/2523—Receiver valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2700/00—Sensing or detecting of parameters; Sensors therefor
- F25B2700/19—Pressures
- F25B2700/195—Pressures of the condenser
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2700/00—Sensing or detecting of parameters; Sensors therefor
- F25B2700/21—Temperatures
- F25B2700/2116—Temperatures of a condenser
- F25B2700/21163—Temperatures of a condenser of the refrigerant at the outlet of the condenser
Definitions
- This application relates to HVAC systems and, more particularly, to HVAC refrigerant charge levels.
- HVAC Heating, Ventilation, and Air Conditioning
- an apparatus for adjusting refrigerant charge level has a reservoir, a reservoir line, a reservoir valve, and one or more side valves.
- the reservoir line connects the reservoir and a liquid line, and has a connection to the liquid line.
- the liquid line connects an indoor heat exchanger and an outdoor heat exchanger.
- the reservoir valve is on the reservoir line.
- the one or more side valves are on the liquid line.
- a method for adjusting refrigerant charge level is provided.
- An indicator of effectiveness of a refrigerant-using system is calculated.
- the indicator is compared to a target indicator of effectiveness.
- a refrigerant charge level is adjusted to reduce the difference between the indicator and the target indicator.
- FIG. 1 depicts a HVAC system with a refrigerant charge control apparatus
- FIG. 2A depicts the refrigerant charge control apparatus configured for normal operation
- FIG. 2B depicts the refrigerant charge control apparatus configured to fill a reservoir during cooling
- FIG. 2C depicts the refrigerant charge control apparatus configured to fill the reservoir during heating
- FIG. 2D depicts the refrigerant charge control apparatus configured to drain the reservoir using gravity
- FIG. 2E depicts the refrigerant charge control apparatus configured to drain during cooling
- FIG. 2F depicts the refrigerant charge control apparatus configured to drain during heating
- FIG. 3 depicts a HVAC system with an alternate refrigerant charge control apparatus
- FIG. 4A depicts the alternate refrigerant charge control apparatus configured for normal operation
- FIG. 4B depicts the alternate refrigerant charge control apparatus configured to fill a reservoir
- FIG. 4C depicts the alternate refrigerant charge control apparatus configured to drain the reservoir during cooling
- FIG. 4D depicts the alternate refrigerant charge control apparatus configured to drain the reservoir during heating
- FIG. 5 depicts a method which a controller may perform to use a subcooling value to control the refrigerant charge
- FIG. 6 depicts a method which a controller may perform to use an Energy Efficiency Ratio (EER) to control the refrigerant charge.
- EER Energy Efficiency Ratio
- HVAC Heating, Ventilation, and Air Conditioning
- System 100 includes indoor unit 102 , outdoor unit 104 , and controller 105 .
- Indoor unit 102 would be located inside a structure to be heated or cooled, such as a building or refrigerator.
- Outdoor unit 104 would be located outside the structure. This combination of an indoor unit and an outdoor unit is generally used in residential HVAC systems but may also be used in other applications, such as refrigeration.
- HVAC system 100 Prior to the operation of apparatus 101 , HVAC system 100 operates conventionally. A continuous flow of refrigerant moves in a loop through HVAC system 100 . This loop may be called the “vapor compression cycle.” Compressor 106 compresses refrigerant in gas vapor form, and then discharges the refrigerant through discharge line 108 . The compressed refrigerant gas vapor enters reversing valve 110 . Reversing valve 110 can change between a cooling configuration, shown by solid lines, and a heating configuration, shown by dashed lines.
- the refrigerant flows from reversing valve 110 to outdoor heat exchanger 112 .
- the refrigerant flows through outdoor heat exchanger 112 , releasing heat into the outdoor air and condensing into a liquid.
- the liquid refrigerant flows through liquid line 114 .
- Liquid line 114 has expansion device 116 A and expansion device 116 B. Expansion devices 116 A and 116 B expand liquid refrigerant flowing through them, reducing the pressure of the refrigerant. However, due to check valves or the like, expansion device 116 A only acts on refrigerant flowing toward outdoor heat exchanger 112 , and expansion device 116 B only acts on refrigerant flowing toward indoor heat exchanger 118 . Refrigerant flowing in the opposite directions, through expansion device 116 A toward indoor heat exchanger 118 or through expansion device 116 B toward outdoor heat exchanger 112 , bypasses the respective expansion device and does not expand.
- the liquid refrigerant bypasses expansion device 116 A and flows to expansion device 116 B. Expansion device 116 B reduces the pressure of the liquid refrigerant flowing through it.
- the refrigerant then flows through indoor heat exchanger 118 , absorbing heat from the structure and evaporating into a gas vapor.
- the refrigerant then flows to reversing valve 110 , where it is directed through suction line 120 and back into compressor 106 to be compressed again.
- the refrigerant flows from reversing valve 110 to indoor heat exchanger 118 .
- the refrigerant flows through indoor heat exchanger 118 , releasing heat into the structure and condensing into a liquid.
- the liquid refrigerant flows through liquid line 114 .
- the liquid refrigerant bypasses expansion device 116 B and flows to expansion device 116 A.
- Expansion device 116 A reduces the pressure of the liquid refrigerant flowing through it.
- the refrigerant then flows through outdoor heat exchanger 112 , absorbing heat from the outdoor air and evaporating into a gas vapor.
- the refrigerant then flows to reversing valve 110 , where it is directed through suction line 120 and back into compressor 106 to be compressed again.
- Outdoor heat exchanger 112 may be called the outdoor coil.
- Indoor heat exchanger 118 may be called the indoor coil.
- outdoor heat exchanger 112 may be called the condenser and indoor heat exchanger 118 may be called the evaporator.
- outdoor heat exchanger 112 may be called the evaporator and indoor heat exchanger 118 may be called the condenser.
- Expansion devices 116 A and 116 B may be expansion valves.
- Refrigerant charge control apparatus 101 comprises reservoir line 124 , reservoir 126 , reservoir valve 128 A, indoor side valve 128 B, and outdoor side valve 128 C.
- Reservoir line 124 connects liquid line 114 to reservoir 126 .
- Reservoir 126 may be a tank which holds excess refrigerant.
- Reservoir valve 128 A may be positioned on reservoir line 124 .
- Indoor side valve 128 B may be positioned on liquid line 114 between reservoir line 124 and indoor heat exchanger 118 .
- Outdoor side valve 128 C may be positioned on liquid line 114 between reservoir line 124 and outdoor heat exchanger 112 .
- Valves 128 A, 128 B, and 128 C can each be opened, to permit the flow of refrigerant, or closed, to block the flow of refrigerant.
- Valves 128 A, 128 B, and 128 C may be solenoid valves.
- Indoor side valve 128 B and outdoor side valve 128 C are called “indoor” and “outdoor” to identify their locations relative to reservoir line 124 and heat exchangers 112 and 118 .
- the “indoor” and “outdoor” names do not identify whether the valves 128 B-C are indoors or outdoors.
- Indoor side valve 128 B may be located indoors or outdoors.
- Outdoor side valve 128 C may be located indoors or outdoors.
- Refrigerant charge control apparatus 101 can be operated to fill reservoir 126 with refrigerant from liquid line 114 , reducing the amount of refrigerant for compressor 106 to compress. Refrigerant charge control apparatus 101 can also be operated to drain refrigerant from reservoir 126 into liquid line 114 , increasing the amount of refrigerant for compressor 106 to compress.
- Controller 105 operates valves 128 A, 128 B, and 128 C to adjust the “refrigerant charge level,” the amount of refrigerant in the vapor compression cycle. Where valves 128 A-C are solenoid valves, controller 105 may send current through valves 128 A-C directly or send a signal that causes current to be sent through valves 128 A-C. Controller 105 may be a unit controller that controls the overall operation of units 102 and 104 , or may be a separate controller that only controls the refrigerant charge level.
- FIG. 2A depicted is a configuration 200 A of refrigerant charge control apparatus 101 in normal operation, when reservoir 126 is not being drained or filled.
- Reservoir valve 128 A is closed, indoor side valve 128 B is open, and outdoor side valve 128 C is open.
- Refrigerant flows through liquid line 114 as it would in the absence of refrigerant charge control apparatus 101 .
- refrigerant would flow through liquid line 114 from left to right during cooling and from right to left during heating.
- refrigerant charge control apparatus 101 is configured to fill reservoir 126 during cooling.
- Reservoir valve 128 A and outdoor side valve 128 C are open, while indoor side valve 128 B is closed.
- Refrigerant 202 flowing from outdoor heat exchanger 112 through liquid line 114 is blocked by indoor side valve 128 B.
- Refrigerant 202 is instead forced through reservoir line 124 into reservoir 126 .
- refrigerant charge control apparatus 101 may return to configuration 200 A.
- refrigerant charge control apparatus 101 is configured to fill reservoir 126 during heating.
- Reservoir valve 128 A and indoor side valve 128 B are open, while outdoor side valve 128 C is closed.
- Refrigerant 202 flowing from indoor heat exchanger 118 through liquid line 114 is blocked by outdoor side valve 128 C.
- Refrigerant 202 is instead forced through reservoir line 124 into reservoir 126 .
- refrigerant charge control apparatus 101 may return to configuration 200 A.
- refrigerant charge control apparatus 101 is configured to drain reservoir 126 using gravity.
- Indoor side valve 128 B and outdoor side valve 128 C are open, allowing refrigerant 202 to flow through liquid line 114 normally.
- Reservoir valve 128 A is also open, allowing gravity to drain refrigerant 202 in reservoir 126 into liquid line 114 .
- refrigerant would flow through liquid line 114 from left to right during cooling and from right to left during heating. After charge is removed from reservoir 126 , refrigerant charge control apparatus 101 may return to configuration 200 A.
- configuration 200 D depends on gravity
- reservoir 126 should be placed above liquid line 114 .
- configurations 200 B and 200 C can be used to drain reservoir 126 using a pressure difference. Reservoir 126 may therefore be placed at the same height as or lower than liquid line 114 . If reservoir 126 is above liquid line 114 , gravity can still aid configurations 200 B and 200 C in draining reservoir 126 .
- FIG. 2E depicted is configuration 200 C used to drain reservoir 126 during cooling.
- Outdoor side valve 128 C is closed, blocking the flow of refrigerant from outdoor heat exchanger 112 and reducing the pressure on the other side of outdoor side valve 128 C.
- Reservoir valve 128 A and indoor side valve 128 B are open. The reduced pressure draws refrigerant from reservoir 126 into liquid line 114 . After charge is removed from reservoir 126 , refrigerant charge control apparatus 101 may return to configuration 200 A.
- FIG. 2F depicted is configuration 200 B used to drain reservoir 126 during heating.
- Indoor side valve 128 B is closed, blocking the flow of refrigerant from indoor heat exchanger 118 and reducing the pressure on the other side of indoor side valve 128 B.
- Reservoir valve 128 A and outdoor side valve 128 C are open. The reduced pressure draws refrigerant from reservoir 126 into liquid line 114 . After charge is removed from reservoir 126 , refrigerant charge control apparatus 101 may return to configuration 200 A.
- HVAC Heating, Ventilation, and Air Conditioning
- System 300 is identical to system 100 except that apparatus 301 has been substituted for apparatus 101 .
- Refrigerant charge control apparatus 301 comprises reservoir line 124 , reservoir 302 , reservoir valve 128 A, indoor side valve 128 B, and outdoor side valve 128 C.
- Reservoir line 124 may connect liquid line 114 to reservoir 302 .
- Valves 128 A, 128 B, and 128 C may be positioned as in apparatus 101 .
- Controller 105 operates valves 128 A, 128 B, and 128 C to adjust the refrigerant charge level.
- Reservoir 302 may be a tank which holds excess refrigerant.
- Suction line 120 passes through reservoir 302 , and may pass through the middle of reservoir 302 .
- Refrigerant stored in reservoir 302 does not flow through suction line 120 into compressor 106 .
- a tank with a suction line passing through it is commonly called a charge compensator.
- FIG. 4A depicted is a configuration 400 A of refrigerant charge control apparatus 301 in normal operation, when reservoir 302 is not being drained or filled.
- Reservoir valve 128 A is closed, indoor side valve 128 B is open, and outdoor side valve 128 C is open.
- Refrigerant flows through liquid line 114 as it would in the absence of refrigerant charge control apparatus 301 .
- refrigerant would flow through liquid line 114 from left to right during cooling and from right to left during heating.
- refrigerant charge control apparatus 301 is configured to fill reservoir 302 .
- Reservoir valve 128 A, indoor side valve 128 B, and outdoor side valve 128 C are open.
- the refrigerant passing through suction line 120 is cooler than the refrigerant passing through liquid line 114 .
- the temperature difference draws refrigerant from liquid line 114 through reservoir line 124 and into reservoir 302 .
- refrigerant charge control apparatus 301 may return to configuration 400 A.
- refrigerant charge control apparatus 301 is configured to drain reservoir 302 during cooling.
- Reservoir valve 128 A and indoor side valve 128 B are open, while outdoor side valve 128 C is closed.
- the closed outdoor side valve 128 C blocks the flow of refrigerant through liquid line 114 , reducing the pressure in liquid line 114 after valve 128 C below the pressure in suction line 120 .
- Refrigerant drains from reservoir 302 into liquid line 114 and flows toward indoor heat exchanger 118 . After charge is removed from reservoir 302 , refrigerant charge control apparatus 301 may return to configuration 400 A.
- refrigerant charge control apparatus 301 is configured to drain reservoir 302 during heating.
- Reservoir valve 128 A and outdoor side valve 128 C are open, while indoor side valve 128 B is closed.
- the closed indoor side valve 128 B blocks the flow of refrigerant through liquid line 114 , reducing the pressure in liquid line 114 after valve 128 B below the pressure in suction line 120 .
- Refrigerant drains from reservoir 302 into liquid line 114 and flows toward outdoor heat exchanger 112 . After charge is removed from reservoir 302 , refrigerant charge control apparatus 301 may return to configuration 400 A.
- HVAC systems 100 and 300 are capable of both heating and cooling.
- a system which can perform both may be called a heat pump.
- one of valves 128 B and 128 C may be removed.
- indoor side valve 128 B is unnecessary.
- outdoor side valve 128 C is unnecessary.
- An exception is a refrigerant charge control apparatus 101 which relies on configuration 200 B or 200 C to drain reservoir 126 . In such an apparatus 101 , both valves 128 B and 128 C are used even if the HVAC system is only capable of one of heating or cooling.
- reversing valve 110 is unnecessary because the direction of refrigerant flow does not reverse.
- Expansion device 116 A is also unnecessary in an air conditioner because refrigerant does not flow through liquid line 114 toward outdoor heat exchanger 112 .
- Expansion device 116 B is also unnecessary in a heater because refrigerant does not flow through liquid line 114 toward indoor heat exchanger 118 .
- Refrigerant charge control apparatuses 101 and 301 are shown inside outdoor unit 104 . However, this is not necessarily the case. Refrigerant charge control apparatuses 101 and 301 may also be inside indoor unit 102 .
- Refrigerant charge control apparatuses 101 and 301 may fill or drain their respective reservoirs by cycling between the normal operation configuration and a fill or drain configuration. For instance, refrigerant charge control apparatus 101 does not necessarily change to configuration 200 B, wait for reservoir 126 to fill sufficiently, and then change to configuration 200 A. Refrigerant charge control apparatus 101 could alternately begin cycling between configuration 200 B and configuration 200 A until reservoir 126 fills sufficiently, then change to configuration 200 A.
- valves 128 A, 128 B, and 128 C are electronic flow valves with variable flow rates.
- controller 105 may adjust the flow rate of the open valve to adjust the rate reservoir 126 or 302 fills or drains.
- Compressor 106 is preferably a variable speed compressor, which can operate at a wide range of possible speeds.
- Compressor 106 may also be a multiple stage compressor, which can operate at a few discrete speeds.
- Compressor 106 may also be a single stage compressor, which operates at only a single speed.
- the benefit of adjusting the refrigerant charge increases with the range of speeds compressor 106 is capable of. With a single stage compressor 106 , the benefit is very limited. The benefit is also less with a multiple stage compressor 106 than a variable speed compressor 106 .
- the speed of compressor 106 increases when the load on the HVAC system is high and decreases when the load on the HVAC system is low.
- the refrigerant charge level should be relatively high.
- only liquid refrigerant should leave the expansion device which expands the refrigerant.
- This expansion device is 116 B in the cooling configuration and 116 A in the heating configuration. If the refrigerant charge level is too low, a mixture of liquid and gas refrigerant will leave the expansion device, which will reduce the performance of the evaporator coil.
- the refrigerant charge level should be relatively low. Less refrigerant is needed to keep gas refrigerant from leaving the expansion device which expands the refrigerant. At the same time, unnecessary refrigerant increases the pressure of the refrigerant in the vapor compression cycle and additional power is used moving that excess refrigerant.
- Method 500 uses a subcooling value to determine whether the refrigerant charge level should be changed.
- the subcooling value is the amount the temperature falls below the saturation temperature of the refrigerant for that pressure.
- the subcooling value is a measure of the effectiveness of the system 100 or 300 .
- Controller 105 may have a memory which stores target subcooling values for a given load on the HVAC system.
- the target subcooling values represent an ideal subcooling value when the refrigerant charge level is optimized for a given load. These target subcooling values may be determined during testing or simulation of the HVAC system.
- controller 105 may measure the temperature and pressure of the liquid leaving the condenser. At 504 , controller 105 may calculate the subcooling value from the temperature and pressure. At 506 , controller 105 may compare the subcooling value to the target subcooling value for the present operating load.
- controller 105 may operate valves 128 A, 128 B, and 128 C on charge control apparatus 101 or charge control apparatus 103 to adjust the refrigerant charge level. Whether to increase or decrease the refrigerant charge level may be a matter of trial and error for controller 105 , based on whether the last adjustment to the refrigerant charge level brought the subcooling value closer to the target subcooling value. If the refrigerant charge level was previously increased and the subcooling value is now closer to the target subcooling value, controller 105 may continue to increase the refrigerant charge level.
- controller 105 may continue to decrease the refrigerant charge level. However, if the refrigerant charge level was previously increased and the subcooling value is now further from the target subcooling value, controller 105 may begin decreasing the refrigerant charge level. If the refrigerant charge level was previously decreased and the subcooling value is now further from the target subcooling value, controller 105 may begin increasing the refrigerant charge level.
- a liquidity sensor may be added to the liquid line.
- the liquidity sensor may be an optical or turbidity sensor which looks for bubbles through a side glass in the liquid line. The absence of bubbles indicates there is sufficient refrigerant charge level in the liquid line. Thus, if the liquidity sensor finds the refrigerant is sufficiently free of bubbles, controller 105 may always decrease the refrigerant charge level.
- Method 600 uses EER (Energy Efficiency Ratio) to determine whether the refrigerant charge level should be changed.
- EER is the ratio of energy expended to the amount of heating or cooling performed.
- the EER is an indicator of the effectiveness of the system 100 or 300 . The higher the EER, the more efficiently the system is operating.
- the amount of energy being expended can be obtained from the inverter driving the compressor.
- the amount of energy being expended can be measured from compressor current, compressor voltage, and phase angle at the compressor.
- the amount of heating or cooling performed is measured by a heat transferring capacity of the HVAC system.
- the heat transferring capacity may be the sensible capacity of the system, regardless of whether the system is heating or cooling. If the system is cooling, the heat transferring capacity may alternately be the latent capacity of the system, or the total of the sensible and latent capacities of the system.
- the sensible capacity may be expressed as the product of indoor airflow rate, a constant, and rise in air temperature. The sensible capacity may therefore be calculated from the indoor airflow, return air temperature, and supply air temperature.
- the return air is the volume of air returned to indoor unit 102 from the structure.
- the supply air is the volume of air passed over indoor heat exchanger 118 and discharged to the structure.
- Indoor unit 102 may have a return air temperature sensor where it receives the return air and a supply air temperature sensor where it discharges the supply air.
- the latent capacity may be predicted from lab test data and present conditions, such as indoor temperature, humidity, and indoor airflow. Alternately, latent capacity may be predicted from the rate of condensate (water vapor that is condensed on the surface of the evaporator).
- Controller 105 may have a memory which stores target EERs for a given load on the HVAC system.
- the target EERs represent an ideal EER when the refrigerant charge level is optimized for a given load. These target EERs may be determined during testing or simulation of the HVAC system.
- controller 105 may measure the energy used by the compressor and sensible capacity of the HVAC system.
- controller 105 may calculate the EER from the energy used and sensible capacity.
- controller 105 may compare the EER to the target EER for the present operating load.
- controller 105 may operate valves 128 A, 128 B, and 128 C on charge control apparatus 101 or charge control apparatus 103 to adjust the refrigerant charge level. 608 may be performed identically to 508 , except with the difference between the EER and target EER used in place of the difference between the subcooling value and target subcooling value.
- reservoirs 126 and 302 may vary depending on the particular HVAC system.
- a reservoir should be large enough to accommodate the difference between the largest and smallest optimal refrigerant charge levels for the different operating loads of the system.
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- Air Conditioning Control Device (AREA)
Abstract
An apparatus and method for adjusting refrigerant charge level are provided. The apparatus has a reservoir, a reservoir line, a reservoir valve, and one or more side valves. The reservoir line connects the reservoir and a liquid line, and has a connection to the liquid line. The liquid line connects an indoor heat exchanger and an outdoor heat exchanger. The reservoir valve is on the reservoir line. The one or more side valves are on the liquid line. In the method, an indicator of effectiveness of a refrigerant-using system is calculated. The indicator is compared to a target indicator of effectiveness. A refrigerant charge level is adjusted to reduce the difference between the indicator and the target indicator.
Description
- This application relates to HVAC systems and, more particularly, to HVAC refrigerant charge levels.
- One area that has not been fully optimized in Heating, Ventilation, and Air Conditioning (HVAC) systems is the refrigerant charge level. Variable speed compressor technology greatly increased the efficiency of HVAC systems by allowing the compressor speed to be better adjusted to match the load on the system. However, the refrigerant charge level (amount of refrigerant in the system) in a conventional HVAC system remains the same regardless of the load on the system. The refrigerant charge level is therefore optimized for a single operating condition. It would be desirable if a HVAC system could optimize its refrigerant charge level for the current operating condition.
- In an embodiment, an apparatus for adjusting refrigerant charge level is provided. The apparatus has a reservoir, a reservoir line, a reservoir valve, and one or more side valves. The reservoir line connects the reservoir and a liquid line, and has a connection to the liquid line. The liquid line connects an indoor heat exchanger and an outdoor heat exchanger. The reservoir valve is on the reservoir line. The one or more side valves are on the liquid line.
- In another embodiment, a method for adjusting refrigerant charge level is provided. An indicator of effectiveness of a refrigerant-using system is calculated. The indicator is compared to a target indicator of effectiveness. A refrigerant charge level is adjusted to reduce the difference between the indicator and the target indicator.
- For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following Detailed Description taken in conjunction with the accompanying drawings, in which:
-
FIG. 1 depicts a HVAC system with a refrigerant charge control apparatus; -
FIG. 2A depicts the refrigerant charge control apparatus configured for normal operation; -
FIG. 2B depicts the refrigerant charge control apparatus configured to fill a reservoir during cooling; -
FIG. 2C depicts the refrigerant charge control apparatus configured to fill the reservoir during heating; -
FIG. 2D depicts the refrigerant charge control apparatus configured to drain the reservoir using gravity; -
FIG. 2E depicts the refrigerant charge control apparatus configured to drain during cooling; -
FIG. 2F depicts the refrigerant charge control apparatus configured to drain during heating; -
FIG. 3 depicts a HVAC system with an alternate refrigerant charge control apparatus; -
FIG. 4A depicts the alternate refrigerant charge control apparatus configured for normal operation; -
FIG. 4B depicts the alternate refrigerant charge control apparatus configured to fill a reservoir; -
FIG. 4C depicts the alternate refrigerant charge control apparatus configured to drain the reservoir during cooling; -
FIG. 4D depicts the alternate refrigerant charge control apparatus configured to drain the reservoir during heating; -
FIG. 5 depicts a method which a controller may perform to use a subcooling value to control the refrigerant charge; and -
FIG. 6 depicts a method which a controller may perform to use an Energy Efficiency Ratio (EER) to control the refrigerant charge. - In the following discussion, numerous specific details are set forth to provide a thorough explanation. However, such specific details are not essential. In other instances, well-known elements have been illustrated in schematic or block diagram form. Additionally, for the most part, specific details within the understanding of persons of ordinary skill in the relevant art have been omitted.
- With reference to
FIG. 1 , depicted is a Heating, Ventilation, and Air Conditioning (HVAC)system 100 with a refrigerantcharge control apparatus 101.System 100 includesindoor unit 102,outdoor unit 104, andcontroller 105.Indoor unit 102 would be located inside a structure to be heated or cooled, such as a building or refrigerator.Outdoor unit 104 would be located outside the structure. This combination of an indoor unit and an outdoor unit is generally used in residential HVAC systems but may also be used in other applications, such as refrigeration. - Prior to the operation of
apparatus 101,HVAC system 100 operates conventionally. A continuous flow of refrigerant moves in a loop throughHVAC system 100. This loop may be called the “vapor compression cycle.”Compressor 106 compresses refrigerant in gas vapor form, and then discharges the refrigerant throughdischarge line 108. The compressed refrigerant gas vapor enters reversingvalve 110. Reversingvalve 110 can change between a cooling configuration, shown by solid lines, and a heating configuration, shown by dashed lines. - In the cooling configuration, the refrigerant flows from reversing
valve 110 tooutdoor heat exchanger 112. The refrigerant flows throughoutdoor heat exchanger 112, releasing heat into the outdoor air and condensing into a liquid. Fromoutdoor heat exchanger 112, the liquid refrigerant flows throughliquid line 114. -
Liquid line 114 hasexpansion device 116A andexpansion device 116B.Expansion devices expansion device 116A only acts on refrigerant flowing towardoutdoor heat exchanger 112, andexpansion device 116B only acts on refrigerant flowing towardindoor heat exchanger 118. Refrigerant flowing in the opposite directions, throughexpansion device 116A towardindoor heat exchanger 118 or throughexpansion device 116B towardoutdoor heat exchanger 112, bypasses the respective expansion device and does not expand. - The liquid refrigerant bypasses
expansion device 116A and flows toexpansion device 116B.Expansion device 116B reduces the pressure of the liquid refrigerant flowing through it. The refrigerant then flows throughindoor heat exchanger 118, absorbing heat from the structure and evaporating into a gas vapor. The refrigerant then flows to reversingvalve 110, where it is directed throughsuction line 120 and back intocompressor 106 to be compressed again. - In the heating configuration, the refrigerant flows from reversing
valve 110 toindoor heat exchanger 118. The refrigerant flows throughindoor heat exchanger 118, releasing heat into the structure and condensing into a liquid. Fromindoor heat exchanger 118, the liquid refrigerant flows throughliquid line 114. The liquid refrigerant bypassesexpansion device 116B and flows toexpansion device 116A.Expansion device 116A reduces the pressure of the liquid refrigerant flowing through it. The refrigerant then flows throughoutdoor heat exchanger 112, absorbing heat from the outdoor air and evaporating into a gas vapor. The refrigerant then flows to reversingvalve 110, where it is directed throughsuction line 120 and back intocompressor 106 to be compressed again. -
Outdoor heat exchanger 112 may be called the outdoor coil.Indoor heat exchanger 118 may be called the indoor coil. During cooling,outdoor heat exchanger 112 may be called the condenser andindoor heat exchanger 118 may be called the evaporator. During heating,outdoor heat exchanger 112 may be called the evaporator andindoor heat exchanger 118 may be called the condenser.Expansion devices - Refrigerant
charge control apparatus 101 comprisesreservoir line 124,reservoir 126,reservoir valve 128A,indoor side valve 128B, andoutdoor side valve 128C.Reservoir line 124 connectsliquid line 114 toreservoir 126.Reservoir 126 may be a tank which holds excess refrigerant. -
Reservoir valve 128A may be positioned onreservoir line 124.Indoor side valve 128B may be positioned onliquid line 114 betweenreservoir line 124 andindoor heat exchanger 118.Outdoor side valve 128C may be positioned onliquid line 114 betweenreservoir line 124 andoutdoor heat exchanger 112.Valves Valves -
Indoor side valve 128B andoutdoor side valve 128C are called “indoor” and “outdoor” to identify their locations relative toreservoir line 124 andheat exchangers valves 128B-C are indoors or outdoors.Indoor side valve 128B may be located indoors or outdoors.Outdoor side valve 128C may be located indoors or outdoors. - Refrigerant
charge control apparatus 101 can be operated to fillreservoir 126 with refrigerant fromliquid line 114, reducing the amount of refrigerant forcompressor 106 to compress. Refrigerantcharge control apparatus 101 can also be operated to drain refrigerant fromreservoir 126 intoliquid line 114, increasing the amount of refrigerant forcompressor 106 to compress. -
Controller 105 operatesvalves valves 128A-C are solenoid valves,controller 105 may send current throughvalves 128A-C directly or send a signal that causes current to be sent throughvalves 128A-C. Controller 105 may be a unit controller that controls the overall operation ofunits - With reference to
FIG. 2A , depicted is aconfiguration 200A of refrigerantcharge control apparatus 101 in normal operation, whenreservoir 126 is not being drained or filled.Reservoir valve 128A is closed,indoor side valve 128B is open, andoutdoor side valve 128C is open. Refrigerant flows throughliquid line 114 as it would in the absence of refrigerantcharge control apparatus 101. InFIG. 2A , refrigerant would flow throughliquid line 114 from left to right during cooling and from right to left during heating. - With reference to
FIG. 2B , depicted is aconfiguration 200B of refrigerantcharge control apparatus 101. Inconfiguration 200B, refrigerantcharge control apparatus 101 is configured to fillreservoir 126 during cooling.Reservoir valve 128A andoutdoor side valve 128C are open, whileindoor side valve 128B is closed.Refrigerant 202 flowing fromoutdoor heat exchanger 112 throughliquid line 114 is blocked byindoor side valve 128B.Refrigerant 202 is instead forced throughreservoir line 124 intoreservoir 126. After charge is added toreservoir 126, refrigerantcharge control apparatus 101 may return toconfiguration 200A. - With reference to
FIG. 2C , depicted is aconfiguration 200C of refrigerantcharge control apparatus 101. Inconfiguration 200C, refrigerantcharge control apparatus 101 is configured to fillreservoir 126 during heating.Reservoir valve 128A andindoor side valve 128B are open, whileoutdoor side valve 128C is closed.Refrigerant 202 flowing fromindoor heat exchanger 118 throughliquid line 114 is blocked byoutdoor side valve 128C.Refrigerant 202 is instead forced throughreservoir line 124 intoreservoir 126. After charge is added toreservoir 126, refrigerantcharge control apparatus 101 may return toconfiguration 200A. - With reference to
FIG. 2D , depicted is a configuration 200D of refrigerantcharge control apparatus 101. In configuration 200D, refrigerantcharge control apparatus 101 is configured to drainreservoir 126 using gravity.Indoor side valve 128B andoutdoor side valve 128C are open, allowing refrigerant 202 to flow throughliquid line 114 normally.Reservoir valve 128A is also open, allowing gravity to drain refrigerant 202 inreservoir 126 intoliquid line 114. InFIG. 2D , refrigerant would flow throughliquid line 114 from left to right during cooling and from right to left during heating. After charge is removed fromreservoir 126, refrigerantcharge control apparatus 101 may return toconfiguration 200A. - Because configuration 200D depends on gravity, to use
configuration 200D reservoir 126 should be placed aboveliquid line 114. As an alternative to configuration 200D,configurations reservoir 126 using a pressure difference.Reservoir 126 may therefore be placed at the same height as or lower thanliquid line 114. Ifreservoir 126 is aboveliquid line 114, gravity can still aidconfigurations reservoir 126. - Referring to
FIG. 2E , depicted isconfiguration 200C used to drainreservoir 126 during cooling.Outdoor side valve 128C is closed, blocking the flow of refrigerant fromoutdoor heat exchanger 112 and reducing the pressure on the other side ofoutdoor side valve 128C.Reservoir valve 128A andindoor side valve 128B are open. The reduced pressure draws refrigerant fromreservoir 126 intoliquid line 114. After charge is removed fromreservoir 126, refrigerantcharge control apparatus 101 may return toconfiguration 200A. - Referring to
FIG. 2F , depicted isconfiguration 200B used to drainreservoir 126 during heating.Indoor side valve 128B is closed, blocking the flow of refrigerant fromindoor heat exchanger 118 and reducing the pressure on the other side ofindoor side valve 128B.Reservoir valve 128A andoutdoor side valve 128C are open. The reduced pressure draws refrigerant fromreservoir 126 intoliquid line 114. After charge is removed fromreservoir 126, refrigerantcharge control apparatus 101 may return toconfiguration 200A. - With reference to
FIG. 3 , depicted is a Heating, Ventilation, and Air Conditioning (HVAC)system 300 with an alternate refrigerantcharge control apparatus 301.System 300 is identical tosystem 100 except thatapparatus 301 has been substituted forapparatus 101. Refrigerantcharge control apparatus 301 comprisesreservoir line 124,reservoir 302,reservoir valve 128A,indoor side valve 128B, andoutdoor side valve 128C.Reservoir line 124 may connectliquid line 114 toreservoir 302.Valves apparatus 101.Controller 105 operatesvalves -
Reservoir 302 may be a tank which holds excess refrigerant.Suction line 120 passes throughreservoir 302, and may pass through the middle ofreservoir 302. Refrigerant stored inreservoir 302 does not flow throughsuction line 120 intocompressor 106. A tank with a suction line passing through it is commonly called a charge compensator. - With reference to
FIG. 4A , depicted is aconfiguration 400A of refrigerantcharge control apparatus 301 in normal operation, whenreservoir 302 is not being drained or filled.Reservoir valve 128A is closed,indoor side valve 128B is open, andoutdoor side valve 128C is open. Refrigerant flows throughliquid line 114 as it would in the absence of refrigerantcharge control apparatus 301. InFIG. 4A , refrigerant would flow throughliquid line 114 from left to right during cooling and from right to left during heating. - With reference to
FIG. 4B , depicted is aconfiguration 400B of refrigerantcharge control apparatus 301. Inconfiguration 400B, refrigerantcharge control apparatus 301 is configured to fillreservoir 302.Reservoir valve 128A,indoor side valve 128B, andoutdoor side valve 128C are open. The refrigerant passing throughsuction line 120 is cooler than the refrigerant passing throughliquid line 114. The temperature difference draws refrigerant fromliquid line 114 throughreservoir line 124 and intoreservoir 302. After charge is added toreservoir 302, refrigerantcharge control apparatus 301 may return toconfiguration 400A. - With reference to
FIG. 4C , depicted is aconfiguration 400C of refrigerantcharge control apparatus 301. Inconfiguration 400C, refrigerantcharge control apparatus 301 is configured to drainreservoir 302 during cooling.Reservoir valve 128A andindoor side valve 128B are open, whileoutdoor side valve 128C is closed. The closedoutdoor side valve 128C blocks the flow of refrigerant throughliquid line 114, reducing the pressure inliquid line 114 aftervalve 128C below the pressure insuction line 120. Refrigerant drains fromreservoir 302 intoliquid line 114 and flows towardindoor heat exchanger 118. After charge is removed fromreservoir 302, refrigerantcharge control apparatus 301 may return toconfiguration 400A. - With reference to
FIG. 4D , depicted is aconfiguration 400D of refrigerantcharge control apparatus 301. Inconfiguration 400D, refrigerantcharge control apparatus 301 is configured to drainreservoir 302 during heating.Reservoir valve 128A andoutdoor side valve 128C are open, whileindoor side valve 128B is closed. The closedindoor side valve 128B blocks the flow of refrigerant throughliquid line 114, reducing the pressure inliquid line 114 aftervalve 128B below the pressure insuction line 120. Refrigerant drains fromreservoir 302 intoliquid line 114 and flows towardoutdoor heat exchanger 112. After charge is removed fromreservoir 302, refrigerantcharge control apparatus 301 may return toconfiguration 400A. -
HVAC systems valves indoor side valve 128B is unnecessary. In a HVAC system which is only capable of cooling, also called an air conditioner,outdoor side valve 128C is unnecessary. An exception is a refrigerantcharge control apparatus 101 which relies onconfiguration reservoir 126. In such anapparatus 101, bothvalves - Additionally, in a heater or air conditioner, reversing
valve 110 is unnecessary because the direction of refrigerant flow does not reverse.Expansion device 116A is also unnecessary in an air conditioner because refrigerant does not flow throughliquid line 114 towardoutdoor heat exchanger 112.Expansion device 116B is also unnecessary in a heater because refrigerant does not flow throughliquid line 114 towardindoor heat exchanger 118. - Refrigerant
charge control apparatuses outdoor unit 104. However, this is not necessarily the case. Refrigerantcharge control apparatuses indoor unit 102. - Refrigerant
charge control apparatuses charge control apparatus 101 does not necessarily change toconfiguration 200B, wait forreservoir 126 to fill sufficiently, and then change toconfiguration 200A. Refrigerantcharge control apparatus 101 could alternately begin cycling betweenconfiguration 200B andconfiguration 200A untilreservoir 126 fills sufficiently, then change toconfiguration 200A. - Depending on tubing size, using simple solenoid valves for
valves valves electronic flow valve controller 105 may adjust the flow rate of the open valve to adjust therate reservoir -
Compressor 106 is preferably a variable speed compressor, which can operate at a wide range of possible speeds.Compressor 106 may also be a multiple stage compressor, which can operate at a few discrete speeds.Compressor 106 may also be a single stage compressor, which operates at only a single speed. However, the benefit of adjusting the refrigerant charge increases with the range ofspeeds compressor 106 is capable of. With asingle stage compressor 106, the benefit is very limited. The benefit is also less with amultiple stage compressor 106 than avariable speed compressor 106. - With a variable speed or
multiple stage compressor 106, the speed ofcompressor 106 increases when the load on the HVAC system is high and decreases when the load on the HVAC system is low. Generally speaking, when there is a relatively low load on the HVAC system, the refrigerant charge level should be relatively high. Ideally, only liquid refrigerant should leave the expansion device which expands the refrigerant. This expansion device is 116B in the cooling configuration and 116A in the heating configuration. If the refrigerant charge level is too low, a mixture of liquid and gas refrigerant will leave the expansion device, which will reduce the performance of the evaporator coil. - Likewise, when there is a relatively high load on the HVAC system, the refrigerant charge level should be relatively low. Less refrigerant is needed to keep gas refrigerant from leaving the expansion device which expands the refrigerant. At the same time, unnecessary refrigerant increases the pressure of the refrigerant in the vapor compression cycle and additional power is used moving that excess refrigerant.
- However, this inverse relationship between load and optimal refrigerant charge level is only true in general. It is possible to have too high a refrigerant charge level with a low load or too low a refrigerant charge level with a high load. Thus, it is not necessarily possible to determine whether the refrigerant charge level should be increased or decreased solely from the present load on the HVAC system.
- With reference to
FIG. 5 , depicted is amethod 500 whichcontroller 105 may perform to control the refrigerant charge level.Method 500 uses a subcooling value to determine whether the refrigerant charge level should be changed. When the gas refrigerant passes through the condenser and changes into a liquid, the temperature of the refrigerant falls but the refrigerant remains at the same pressure. The subcooling value is the amount the temperature falls below the saturation temperature of the refrigerant for that pressure. The subcooling value is a measure of the effectiveness of thesystem -
Controller 105 may have a memory which stores target subcooling values for a given load on the HVAC system. The target subcooling values represent an ideal subcooling value when the refrigerant charge level is optimized for a given load. These target subcooling values may be determined during testing or simulation of the HVAC system. - At 502,
controller 105 may measure the temperature and pressure of the liquid leaving the condenser. At 504,controller 105 may calculate the subcooling value from the temperature and pressure. At 506,controller 105 may compare the subcooling value to the target subcooling value for the present operating load. - At 508,
controller 105 may operatevalves charge control apparatus 101 or charge control apparatus 103 to adjust the refrigerant charge level. Whether to increase or decrease the refrigerant charge level may be a matter of trial and error forcontroller 105, based on whether the last adjustment to the refrigerant charge level brought the subcooling value closer to the target subcooling value. If the refrigerant charge level was previously increased and the subcooling value is now closer to the target subcooling value,controller 105 may continue to increase the refrigerant charge level. Likewise, if the refrigerant charge level was previously decreased and the subcooling value is now closer to the target subcooling value,controller 105 may continue to decrease the refrigerant charge level. However, if the refrigerant charge level was previously increased and the subcooling value is now further from the target subcooling value,controller 105 may begin decreasing the refrigerant charge level. If the refrigerant charge level was previously decreased and the subcooling value is now further from the target subcooling value,controller 105 may begin increasing the refrigerant charge level. - To assist
controller 105 in determining whether to increase or decrease the refrigerant charge level, a liquidity sensor may be added to the liquid line. The liquidity sensor may be an optical or turbidity sensor which looks for bubbles through a side glass in the liquid line. The absence of bubbles indicates there is sufficient refrigerant charge level in the liquid line. Thus, if the liquidity sensor finds the refrigerant is sufficiently free of bubbles,controller 105 may always decrease the refrigerant charge level. - With reference to
FIG. 6 , depicted is analternate method 600 whichcontroller 105 may perform to control the refrigerant charge level.Method 600 uses EER (Energy Efficiency Ratio) to determine whether the refrigerant charge level should be changed. EER is the ratio of energy expended to the amount of heating or cooling performed. The EER is an indicator of the effectiveness of thesystem - In a compressor driven by an inverter, the amount of energy being expended can be obtained from the inverter driving the compressor. In a compressor not driven by an inverter, the amount of energy being expended can be measured from compressor current, compressor voltage, and phase angle at the compressor. The amount of heating or cooling performed is measured by a heat transferring capacity of the HVAC system. The heat transferring capacity may be the sensible capacity of the system, regardless of whether the system is heating or cooling. If the system is cooling, the heat transferring capacity may alternately be the latent capacity of the system, or the total of the sensible and latent capacities of the system.
- The sensible capacity may be expressed as the product of indoor airflow rate, a constant, and rise in air temperature. The sensible capacity may therefore be calculated from the indoor airflow, return air temperature, and supply air temperature. The return air is the volume of air returned to
indoor unit 102 from the structure. The supply air is the volume of air passed overindoor heat exchanger 118 and discharged to the structure.Indoor unit 102 may have a return air temperature sensor where it receives the return air and a supply air temperature sensor where it discharges the supply air. - The latent capacity may be predicted from lab test data and present conditions, such as indoor temperature, humidity, and indoor airflow. Alternately, latent capacity may be predicted from the rate of condensate (water vapor that is condensed on the surface of the evaporator).
-
Controller 105 may have a memory which stores target EERs for a given load on the HVAC system. The target EERs represent an ideal EER when the refrigerant charge level is optimized for a given load. These target EERs may be determined during testing or simulation of the HVAC system. - At 602,
controller 105 may measure the energy used by the compressor and sensible capacity of the HVAC system. At 604,controller 105 may calculate the EER from the energy used and sensible capacity. At 606,controller 105 may compare the EER to the target EER for the present operating load. At 608,controller 105 may operatevalves charge control apparatus 101 or charge control apparatus 103 to adjust the refrigerant charge level. 608 may be performed identically to 508, except with the difference between the EER and target EER used in place of the difference between the subcooling value and target subcooling value. - The size of
reservoirs - It is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Many such variations and modifications may be considered desirable by those skilled in the art based upon a review of the foregoing description of various embodiments.
Claims (15)
1. An apparatus for adjusting refrigerant charge level, the apparatus comprising:
a reservoir;
a reservoir line connecting the reservoir and a liquid line, the liquid line connecting an indoor heat exchanger and an outdoor heat exchanger, the reservoir line comprising a connection to the liquid line;
a reservoir valve on the reservoir line; and
one or more side valves on the liquid line.
2. The apparatus of claim 1 , wherein the one or more side valves comprises an indoor side valve on the liquid line between the indoor heat exchanger and the connection to the reservoir line.
3. The apparatus of claim 1 , wherein the one or more side valves comprises an outdoor side valve on the liquid line between the outdoor heat exchanger and the connection to the reservoir line.
4. The apparatus of claim 1 , wherein the one or more side valves comprises:
an indoor side valve on the liquid line between the indoor heat exchanger and the connection to the reservoir line; and
an outdoor side valve on the liquid line between the outdoor heat exchanger and the connection to the reservoir line.
5. The apparatus of claim 1 , wherein the reservoir valve and the one or more side valves each comprise a solenoid valve.
6. The apparatus of claim 1 , wherein the reservoir is above the liquid line.
7. The apparatus of claim 1 , wherein:
a suction line passes through the reservoir; and
the suction line is connected to a compressor.
8. A method for adjusting refrigerant charge level, the method comprising:
calculating an indicator of effectiveness of a refrigerant-using system;
comparing the indicator to a target indicator of effectiveness; and
adjusting a refrigerant charge level to reduce the difference between the indicator and the target indicator.
9. The method of claim 8 , wherein adjusting the refrigerant charge level comprises opening or closing a solenoid valve.
10. The method of claim 8 , wherein:
the indicator comprises a subcooling value;
the target indicator comprises a subcooling value; and
calculating the indicator comprises measuring a liquid temperature and liquid pressure.
11. The method of claim 8 , wherein:
the indicator comprises an energy efficiency ratio;
the target indicator comprises an energy efficiency ratio; and
calculating the indicator comprises:
measuring an energy usage of a compressor; and
measuring a heat transferring capacity of the system.
12. The method of claim 11 , wherein the heat transferring capacity comprises a sensible capacity of the system.
13. The method of claim 12 , wherein measuring the sensible capacity comprises measuring an indoor airflow, a return air temperature, and a supply air temperature.
14. The method of claim 11 , wherein the heat transferring capacity comprises a latent capacity of the system.
15. The method of claim 11 , wherein the heat transferring capacity comprises a total of:
a sensible capacity of the system; and
a latent capacity of the system.
Priority Applications (2)
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US14/221,702 US20150267951A1 (en) | 2014-03-21 | 2014-03-21 | Variable refrigerant charge control |
CA2885755A CA2885755A1 (en) | 2014-03-21 | 2015-03-19 | Variable refrigerant charge control |
Applications Claiming Priority (1)
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US14/221,702 US20150267951A1 (en) | 2014-03-21 | 2014-03-21 | Variable refrigerant charge control |
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US14/221,702 Abandoned US20150267951A1 (en) | 2014-03-21 | 2014-03-21 | Variable refrigerant charge control |
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US20210088263A1 (en) * | 2019-09-23 | 2021-03-25 | Lennox Industries Inc. | Method and system for charge determination |
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US11435123B2 (en) * | 2018-12-19 | 2022-09-06 | Toromont Industries Ltd | Refrigeration system with transfer system |
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