The present invention provides a system and method for an improved multistage, cascade refrigeration system using hot gas defrost to rid the evaporator of ice build-up which accumulates over time, while the air in the evaporator enclosure remains below the freezing point of water. The present invention thus provides greater defrost flexibility with increased ease of design and implementation than current refrigeration systems, which allows for more robust hot gas defrost function for multistage refrigeration systems, such that it is unaffected by temperature changes of the condensing fluid (ambient air temperature for air cooled condensers, water temperature for water cooled condensers), and can be readily adapted to any refrigerant suitable for a selected temperature range.

An air conditioning system and a startup control method. The air conditioning system includes: a compressor, a condenser, a thermal expansion valve and an evaporator connected via a pipeline; and a thermal temperature sensing bulb disposed on an outlet pipeline of the evaporator and associated with the thermal expansion valve; the air conditioning system further includes a thermal power source which is thermally coupled to the thermal temperature sensing bulb and controlledly cools or heats the thermal temperature sensing bulb. The thermal temperature sensing bulb is cooled or heated, as needed, by a thermal power source thermally coupled to the thermal temperature sensing bulb, thereby enabling the thermal expansion valve associated with the thermal temperature sensing bulb to be opened and closed more smoothly.

The present invention pertains to a thermal expansion valve for a heat exchanger with at least one header. The valve includes a valve block and a superheat defining mechanism. The valve block includes a high pressure inlet, a low pressure outlet, a first suction gas port and a second suction gas port. A contact surface for coupling the valve to the header includes at least one cylindrical portion of the valve block. The invention is also directed at a heat exchanger with a corresponding thermal expansion valve.

In a heat pump system, a suction stabilizer control circuit (SSCC) reduces or eliminates subcooling at the condenser and reduces superheating needed for compressor protection at the evaporator. The SSCC includes a bypass line that bypasses a predetermined portion of flow through a refrigerant liquid transport line around a thermostatic expansion valve (TXV).

A method of detecting electrical failure in a refrigeration system is provided. The method includes determining whether a present superheat of the refrigeration system is between a maximum superheat and a minimum superheat for the refrigeration system, the maximum superheat and the minimum superheat defining a normal operating range. The method also includes detecting an electrical property of an expansion valve assembly of the refrigeration system responsive to the superheat being outside the normal operating range. The method further includes determining whether the expansion valve assembly as experienced an electrical failure based on at least the electrical property. A signal indicating that the expansion valve has experienced an electrical failure is generated based on a determination that the expansion valve assembly has experienced the electrical failure.

An air conditioner unit and method of operating the same includes performing an operating cycle in a feedback control mode, including adjusting the an electronic expansion valve (EEV) to minimize an error between a measured superheat and a target superheat using a PI controller, determining that a target compressor speed has changed by greater than a predetermined speed threshold, and initiating a linear control mode of the operating cycle, including adjusting the EEV using a valve position equation that is a function of the target compressor speed, an indoor temperature, and an outdoor temperature. The controller may also start a transition timer upon initiation of the linear control mode, transition back into a feedback control mode upon expiration of the transition timer, and initialize the integral term of the PI controller based on the EEV position from the linear control mode.

A refrigeration system includes a heat exchanger configured to provide superheat control for the low temperature low pressure gas refrigerant flowing out of the evaporator and through the first side of the heat exchanger by transferring heat from the high pressure high temperature superheated gas refrigerant flowing through a second side of the heat exchanger. A modulating solenoid valve is located at the inlet of the second side of the heat exchanger and configured to modulate the flow of high pressure high temperature superheated gas refrigerant flowing through the second side of the heat exchanger. A temperature sensor is located in such a way as to measure the temperature of the gas refrigerant flowing out of the evaporator and through the first side of the heat exchanger. A controller is configured to calculate the superheat of the gas refrigerant based on the measured temperature and measured pressure of the gas refrigerant and may compare the calculated superheat to a superheat threshold. If the calculated superheat is less than the superheat threshold, the controller will modulate the flow the high pressure high temperature gas refrigerant flowing through the second side of the heat exchanger. The refrigeration system may be activated in a variety of methods by appropriate control of the valves and other system components.

An expansion valve includes: a body having a second passage through which a refrigerant returning from an evaporator passes, and a mounting hole communicating with the second passage; a power element mounted on the body in such a manner as to close the mounting hole; a shaft that transmits a drive force from the power element to a valve element; and a plate that separates an open space from the second passage, has an insertion hole, through which the shaft extends, coaxially along a central axis of the plate, and limits a flow of the refrigerant from the second passage into the open space to a flow through a clearance between the shaft and the insertion hole. The insertion hole is formed such that an opening area of the clearance between the shaft and the insertion hole is 7.0 mm.sup.2 or smaller.

A refrigeration apparatus includes a refrigerant circuit connecting heat-source units in parallel with usage units. First and second heat-source units have first and second compressors, first and second heat-source-side heat exchangers, first and second high-pressure receivers, first and second detecting elements detecting whether the receivers are near flooding, first and second bypass channels returning refrigerant in top parts of the receivers to intake sides of the compressors, and first and second motor-operated valves on the bypass channels, respectively. A controller performs excess refrigerant distribution control in which an opening degree of the first valve is controlled to be greater than an opening degree of the second valve when the second detecting element detects a nearly flooded state, and the opening degree of the second valve is controlled to be greater than the opening degree of the first valve when the first detecting element detects a nearly flooded state.

A thermal expansion valve comprises a valve body and a valve core member. The valve body is provided with a first connecting chamber, a lower cavity with a transmission member built in, and a first sealing member for separating the first connecting chamber and the lower cavity. A fifth pressure-bearing surface and a sixth pressure-bearing surface, pressed by a cold medium in the first connecting chamber in opposite directions, are disposed on a side wall of the valve core member. The first sealing member comprises a first flexible sealing element, disposed between the transmission member and an upper end portion of the valve core member and having a first edge portion connected to the valve body in a sealing manner. A sum of an effective stress area of a first pressure-bearing surface of the first flexible sealing element and a stress area of the fifth pressure-bearing surface is substantially equal to a sum of an effective stress area of a third pressure-bearing surface of the upper end portion of the valve core member and a stress area of the sixth pressure-bearing surface. Through the design of the structure of the thermal expansion valve, in an aspect, reliability of sealing between the valve body and the upper end portion of the valve core member can be ensured, sensitivity of the valve is improved, and difficulty of manufacturing the valve body and the valve core member can be reduced; and in another aspect, pressure influence caused by the cold medium in the first connecting chamber on the movement of the valve core member can be eliminated.