A system includes a flash tank, a load, a first compressor, a second compressor, and a liquid injection line. The flash tank stores a refrigerant. The load uses the refrigerant from the flash tank to remove heat from a space proximate the load. The first compressor compresses the refrigerant from the load. The second compressor compresses the refrigerant from the first compressor. The liquid injection line is coupled to the flash tank and to the second compressor and sends a liquid refrigerant from the flash tank to mix with the refrigerant from the first compressor before the refrigerant from the first compressor is received by the second compressor.

The present invention refers to methods for controlling a double suction compressor for application in refrigeration systems, capable of meeting the different demands for cost, efficiency and control of temperatures by means of techniques of complexity levels and different configurations of the elements from the control loop (temperature sensors, actuators, controllers, etc.). The proposed solutions include the description of a method for controlling and adjusting the refrigeration capacities of a refrigeration system equipped with a double suction compressor, the refrigeration system comprising compartments to be refrigerated and comprising at least two evaporators (20) positioned in the compartments to be refrigerated (60,70), the double suction compressor (10) being controllable to alternate its compression capacity, the method comprising steps of (i) Continuously measuring at least a temperature coming from a temperature sensor (SET,SCT) associated with at least one of the evaporators (20) and (ii) acting in the compressor's (10) compression capacity, from the measurement of step (i).

In a heat pump apparatus, it is aimed to enhance efficiency of a defrost operation by reducing a loss of heat radiation during the defrost operation and reducing a compressor input during the defrost operation. The heat pump apparatus includes a main refrigerant circuit in which a compressor, a first heat exchanger, an expansion mechanism, and a second heat exchanger are connected sequentially, and also includes a bypass circuit including an on-off valve and providing a connection by bypassing the expansion mechanism. The main refrigerant circuit includes a four-way valve that switches between a heating operation and the defrost operation by switching an order in which the refrigerant circulates through the main refrigerant circuit. The main refrigerant circuit also includes a first temperature detection unit and a second temperature detection unit. Based on values detected by these temperature detection units, a degree of superheat of the first heat exchanger during the defrost operation is computed. When the heating operation is switched to the defrost operation, the heat pump apparatus increases a circulation amount of the refrigerant circulating through the refrigerant circuit by opening the on-off valve, and also controls an operation frequency of the compressor such that the degree of superheat is at a predetermined target value.

A refrigeration system includes a compressor, a condenser, a heat transfer component, and a refrigerant loop arranged to allow a flow of a refrigerant fluid. The compressor, the condenser, and the heat transfer component are connected in the refrigerant loop. The system further includes a bypass path extending between an output side of the compressor in the refrigerant loop and an input side of the heat transfer component in the refrigerant loop. A bypass valve is connected in the bypass path. A control circuit is in communication with the bypass valve. The control circuit is configured to open the bypass valve to allow the refrigerant fluid to pass to the heat transfer component thereby increasing the refrigerant fluid provided to the heat transfer component and artificially increasing a load on the refrigeration system. Other examples refrigeration system and examples methods are also disclosed.

A heat pump device having a refrigerant circuit includes: a valve configured to maintain an opening degree during non-energization; a valve drive circuit configured to cause operation of the valve; a valve controller configured to control the valve drive circuit; and a power source circuit configured to supply a power source to the valve drive circuit. The power source circuit includes: a first power source circuit unit configured to receive power source supply from outside to generate a DC voltage; and a second power source circuit unit for backup. The second power source circuit unit receives power source supply from the outside to store power in a capacitor, and connects the capacitor in parallel to a first output electric path of the first power source circuit unit.