The invention is an impulse system and a method for heat transfer in thermal nonequilibrium state through a heat-transferring wall of a heat transferring volume. The system is based on a heat transferring volume and an impulse device in fluid, pressure and thermal communication with each other, where the impulse device delivers a heat load to the heat transferring volume through a working medium in condensed phase impulses. The impulse device controls the rate of delivery of impulses such that each subsequent impulse is received before the heat capacity of the heat transferring wall returns to an equilibrium state thereby resulting in an accumulation of the changes in heat capacity of the heat transferring wall and subsequent changes in the temperature of the heat-transferring wall above or below the wall thermal equilibrium state to increase the heat transfer flow through the wall.

A refrigeration system includes a compressor; a condenser; an expansion valve having a body with an expansion valve inlet and an expansion valve outlet; an evaporator all arranged in a refrigeration circuit; and a controller. The expansion valve body has a pathway comprising an inlet body capillary tube flow-connected to the expansion valve inlet, and an outlet body capillary tube flow-connected to the expansion valve outlet. The expansion valve comprises a solenoid operated valve element that is selectively positionable between the inlet body capillary tube outlet and the outlet body capillary tube inlet. The controller digitally controls the valve element to position the valve element either to allow flow through the pathway in an open position or to block flow through the pathway in a closed position.

A refrigerant cycle of the present invention includes including an outdoor unit, a plurality of indoor units, and a controller for controlling the refrigeration cycle using at least one EEV. The controller comprises a velocity PID component executing a velocity PID control using pulse number for driving an EEV, three-state controller determining a driving state of the EEV and generating pulse commands designating the driving state, and a state machine driving the EEV depending on the pulse commands generated by the three-state controller.

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.

A refrigeration apparatus including a compressor (301), a condenser (302), an expansion device (304), and an evaporator (305), fluidly connected to form a refrigeration cycle for a refrigerant, wherein the compressor (301) has a variable working capacity, and wherein the expansion device (304) has a configurable flow resistance with respect to the refrigerant passing through the expansion device. The apparatus further includes a controller (300) which is configured to determine a current working capacity of the compressor (301) and to control the resistance of the expansion device (304) in dependence on the current working capacity of the compressor (301). The controller (300) is further configured to control the resistance of the expansion device (304) in order to achieve a mass flow of the refrigerant through the expansion device (304), which mass flow corresponds to a mass flow of the refrigerant through the compressor (301).

A method of controlling fluid flow through a heating, ventilating, air conditioning, and refrigeration (HVAC-R) system includes measuring temperature and pressure at an outlet of an evaporator of the HVAC-R system, wherein the evaporator is in fluid communication with a compressor, a condenser, an expansion device between the evaporator and the condenser, and a flow control valve between the compressor and the condenser, and measuring a sub-cooling temperature at an outlet of the condenser. The measured evaporator temperature and pressure data is sent to a first superheat processor, and the measured sub-cooling temperature data is send to a second superheat processor. A control signal to the expansion device from the first superheat processor and a control signal to the flow control valve from the second superheat processor are then simultaneously sent.

An air conditioning apparatus includes a refrigerant circuit and a controller. The refrigerant circuit is configured to allow refrigerant to circulate through a compressor, a condenser, an LEV, and an evaporator. The LEV has an opening degree variable from a lower limit opening degree to an upper limit opening degree. The controller is configured to control the LEV to alternately repeat a first opening degree and a second opening degree in a range of less than or equal to a quarter of the upper limit opening degree, the second opening degree being smaller than the first opening degree.

The invention relates to a refrigerant for a cooling device (10) comprising a cooling circuit (11) comprising at least one heat exchanger (12), the refrigerant undergoing a phase transition in the heat exchanger, the refrigerant being a refrigerant mixture composed of a fraction of carbon dioxide (CO.sub.2), a fraction of 1,1-difluoroethene and a fraction of at least one other component, wherein the fraction of carbon dioxide in the refrigerant mixture is 45 to 90 mole percent, the fraction of 1,1-difluoroethene being 5 to 40 mole percent.

A method of maintaining a fluid flow rate in a heating, ventilating, air conditioning, and refrigeration (HVAC-R) system while maintaining superheat in the HVAC-R system at a desired level includes: continuously measuring an operating fluid temperature of the HVAC-R system and calculating superheat at a pre-determined rate, determining if the calculated superheat is stable, measuring and recording an operating fluid pressure of the system each time the calculated superheat is stable, recording an average operating fluid pressure each subsequent time the superheat is stable, calculating an output PWM and reducing fluid flow through a metering valve when an actual PWM is greater than the calculated output PWM by adjusting a PWM signal to a microvalve in the metering valve, and increasing fluid flow through the metering valve when the actual PWM is less than the calculated output PWM by adjusting the PWM signal to the microvalve.

A method of controlling fluid flow through a heating, ventilating, air conditioning, and refrigeration (HVAC-R) system includes measuring temperature and pressure at an outlet of an evaporator of the HVAC-R system, wherein the evaporator is in fluid communication with a compressor, a condenser, an expansion device between the evaporator and the condenser, and a flow control valve between the compressor and the condenser, and measuring a sub-cooling temperature at an outlet of the condenser. The measured evaporator temperature and pressure data is sent to a first superheat processor, and the measured sub-cooling temperature data is send to a second superheat processor. A control signal to the expansion device from the first superheat processor and a control signal to the flow control valve from the second superheat processor are then simultaneously sent.