Disclosed are an air conditioning system and its pressure ratio control method and device. The method includes: acquiring an actual pressure ratio of the compressor every preset time period in operation of the air conditioning system; judging whether the actual pressure ratio is greater than or equal to the first pressure ratio corresponding to a current level; controlling the compressor to downshift one level for operation if the actual pressure ratio is greater than or equal to the first pressure ratio corresponding to the current level; further judging whether the actual pressure ratio is less than the second pressure ratio corresponding to the current level if the actual pressure ratio is less than the first pressure ratio corresponding to the current level; and controlling the compressor to upshift one level for operation if the actual pressure ratio is less than the second pressure ratio corresponding to the current level.

A refrigeration cycle apparatus includes a refrigerant circuit in which refrigerant circulates in the order of a compressor, an oil separator, a first heat exchanger, a decompressing apparatus, and a second heat exchanger and returns to the compressor. The refrigeration cycle apparatus further includes: an oil reservoir that stores refrigeration oil; a first pipe that connects the oil separator and the oil reservoir, the first pipe sends the refrigeration oil separated by the oil separator to the oil reservoir; a second pipe that connects the oil reservoir and a suction side of the compressor; a third pipe that connects the oil reservoir and the suction side of the compressor at a position lower than a position at which the second pipe is connected to the oil reservoir; and a heater that heats the refrigeration oil separated by the oil separator.

The present disclosure provides a multi-air conditioner for heating/cooling operation including: at least one of indoor units for heating/cooling operation including an indoor heat exchanger respectively; and an outdoor unit for heating/cooling operation including a compressor, an outdoor heat exchanger, and a switching unit configured to be disposed in a discharge side of the compressor to switch a flow of refrigerant, wherein the outdoor unit for heating/cooling operation includes a receiver which selectively stores refrigerant or oil according to a cooling or heating operation mode and provides the stored refrigerant or oil to the compressor. Accordingly, in the accumulator of the multi-air conditioner for heating/cooling operation using the receiver, the receiver that is not used in the heating mode can be converted and used for oil storage, thereby preventing oil burnout without adding a structure.

The method for controlling the refrigerator includes operating a first cooling cycle for cooling the first storage compartment to operate the compressor and operating a first fan for the first storage compartment, and switching the first cooling cycle to a second cooling cycle for cooling the second storage compartment to operate the compressor and operating a second fan when a stop condition of the first cooling cycle is satisfied. A temperature of each storage compartment is sensed at sampling time intervals in each cooling cycle. Further, a cooling power of the compressor is determined for each sampling time based on a sensed current temperature of the storage compartment, and the compressor is operated at the determined cooling power.

An air-conditioning apparatus includes heat-source-side units each including a compressor and a heat-source-side heat exchanger, a load-side heat exchanger and a load-side expansion device, a first header, a second header, bypass expansion devices, circuit switching units, discharge pressure sensors, bypass pressure sensors, and a controller configured to control, in a heat-source-side unit in defrosting mode, the circuit switching unit in such a manner that a portion of refrigerant discharged from the compressor flows into the heat-source-side heat exchanger and configured to control, in the heat-source-side unit in defrosting mode, an opening degree of the bypass expansion device in the heat-source-side unit in such a manner that a value representing a difference between a value obtained by the discharge pressure sensor and a value obtained by the bypass pressure sensor is equal to or greater than a predetermined value.

A cooling system is designed to generally allow for one or more compressors to be bypassed when ambient temperatures are low. The system includes a bypass line and valve that opens when ambient temperatures are low and/or when the pressure of the refrigerant in the system is low. In this manner, the refrigerant can flow through the bypass line instead of through one or more compressors. These compressors may then be shut off. To supply any needed pressure to cycle the refrigerant, the system may include a pump that turns on when the bypass line is open. When ambient temperatures are extremely low, thermosiphon may be used to cycle the refrigerant.

A control module for a refrigeration system includes a startup mode control module that receives an off time of a compressor and an ambient temperature, determines whether the off time and the ambient temperature indicate that the compressor is in a flooded condition, and selects, based on the determination, between a normal startup mode and a flooded startup mode. A compressor control module transitions from the flooded startup mode to the normal startup mode after a predetermined period associated with operating in the flooded startup mode and operates the compressor at a first speed in the normal startup mode and operates the compressor at a second speed less than the first speed in the flooded startup mode.

A multi-stage refrigeration system (100) includes: a refrigeration loop (110), which includes a gas suction port of a multi-stage compressor (111), a condenser (112), a first throttling element (113), an evaporator (114) and an exhaust port of the multi-stage compressor which are sequentially connected through pipelines; an economizer branch (120), which includes an economizer (121), a second throttling element (122) and a first control valve (123), the economizer having an economizer liquid inlet connected to the condenser via the first throttling element, an economizer liquid outlet connected to the evaporator via the second throttling element, and an economizer exhaust port connected to an intermediate stage of the multi-stage compressor via a control valve; and a bypass branch (130), which is joined to the evaporator from the downstream of the second throttling element and connected to the condenser via the first throttling element, and on which a second control valve (131) is arranged.

There is provided a vehicle air conditioning apparatus capable of removing frost formed on an outdoor heat exchanger at the same time as cooling of a battery. The vehicle air conditioning apparatus performs the operation in a first battery cooling mode, a second battery cooling mode, or a solo battery cooling mode, when it is determined that the battery needs to be cooled and also determined that the frost formed on the outdoor heat exchanger needs to be removed. By this means, it is possible to cool the battery and melt the frost formed on the outdoor heat exchanger at the same time by the battery cooling operation, and therefore it is possible to reduce the power consumption compared to the case where the battery cooling operation and the defrosting operation are performed individually.

A method of managing a compressor start operation, the method includes controlling a valve disposed upstream of a compressor to lower a saturated suction temperature of a refrigerant to be below an ambient temperature while starting the compressor.