US 4,484,452 AGranted

Heat pump refrigerant charge control system

AssigneeThe Trane Company

InventorMarion E. Houser, Jr.

Life of this patent

Estimating the term…

Loading patent…

Abstract

A microcomputer controlled charge control system for modulating charge in a heat pump refrigerant circuit. A charge receiver has its interior in thermal communication with the compressor suction line and has a single charge flow line connected via a charge control valve to the refrigerant circuit at a point intermediate two controllable expansion valves in the high side of the circuit. Super-heating and subcooling strategies are employed to maintain the charge level in the circuit at optimum performance levels, automatically adapting to changes in environmental load conditions on the heat pump heat exchange coils. Additional control strategy is employed to shift refrigerant charge into and out of the circuit during transient operation, such as during start-up, stop and reversal into defrost, to optimize operating efficiency during these transient conditions and also to assure correct placement of the refrigerant charge, for example, to avoid compressor slugging during start-up following an off cycle or a reversal in refrigerant flow.

Claims15

Dependent claims

An improved refrigerant charge control system for a heat pump used to temperature condition an indoor zone under variable load conditions, said heat pump having a refrigerant circuit including indoor and outdoor heat exchange coils, a refrigerant compressor, and a switchover valve adapted to reverse the flow of refrigerant through the refrigerant circuit so that the heat pump may be selectively operated in either a heating mode or a cooling mode;

the circuit further including a first refrigerant flow line interconnecting one end of each of the heat exchange coils via the compressor and the switchover valve, the first flow line having suction and discharge line sections, and a second refrigerant flow line directly interconnecting the other ends of the heat exchange coils, the improvement comprising:
first and second controllable expansion valves in the second refrigerant flow line;
a refrigerant charge receiver, the interior of which is in thermal communication with said suction line section;
a third refrigerant flow line including a controllable charge control valve connecting said charge receiver to the second refrigerant line at a point intermediate said first and second controllable expansion valves;
means for sensing refrigerant temperature and pressure at predetermined points in the refrigerant circuit;
and control means responsive to said sensed temperatures and pressures for controlling operation of said valves to provide bidirectonal flow of refrigerant into and out of the refrigerant circuit at said intermediate point to adjust the amount of refrigerant charge in the refrigerant circuit for efficient operation of the system in each of the heating and cooling modes, as the temperature conditioning load on the heat pump changes.

3 more elements

An improved refrigerant charge control system for a heat pump used to temperature condition an indoor zone under the variable load conditions, said heat pump having a refrigerant circuit including indoor and outdoor heat exchange coils, a refrigerant compressor, and a switchover valve adapted to reverse the flow of refrigerant through the refrigerant circuit so that the heat pump may be selectively operated in either a heating mode or a cooling mode;

the circuit furter including a first refrigerant flow line interconnecting one end of each of the heat exchange coils via the compressor and the switchover valve, the first flow line having suction and discharge line sections, and a second refrigerant flow line directly interconnecting the other ends of the heat exchange coils, said control system comprising:
first and second electrically modulated expansion valves disposed in the second refrigerant flow;
a refrigerant charge receiver, the interior of which isin thermal communication with said suction line section;
a third refrigerant flow line including an electrically controlled valve connecting said charge receiver to the second refrigerant line at a point intermediate said first and second electrically modulated expansion valves;
means for determining superheat at the suction line section of the refrigerant circuit;
means for determining subcooling at the second refrigerant flow line of the refrigerant circuit;
and
control means for controlling operation of the first and second electrically modulated expansion valves and the electrical controlled valve in the third refrigerant flow line to adjust the proportion of refrigerant charge stored in the charge receiver and flowing in the refrigerant circuit to achieve predetermined levels of superheat and subcooling during operation of the heat pump in both the heating and cooling modes as the temperatures conditioning load changes.

5 more elements

Dependencies are inferred from the claim text.