A method of cooling a boil-off gas (BOG) stream from a liquefied gas tank comprising at least the step of heat exchanging the BOG stream with a first refrigerant in a heat exchanger, the heat exchanger having an entry port and a warmer exit port, and comprising at least the steps of: (a) passing the first refrigerant into the entry port of the heat exchanger and into a first zone of the heat exchanger to exchange heat with the BOG stream, to provide a first warmer refrigerant stream; (b) withdrawing the first warmer refrigerant stream from the heat exchanger at an intermediate exit port between the entry port and the warmer exit port; (c) admixing the first warmer refrigerant stream with an oil-containing refrigerant stream to provide a combined refrigerant stream; (d) passing the combined refrigerant stream into the heat exchanger through an entry port located in a second zone of the heat exchanger that is warmer than the first zone; (e) passing the combined refrigerant stream out of the heat exchanger through the warmer exit port. The present invention is a modification of a refrigerant cycle for BOG cooling, and LNG re-liquefaction in particular, that allows the use of a cost-efficient oil-injected screw compressor in the refrigerant system. The present invention is also able to accommodate the possibility of different flows or flow rates of the first refrigerant stream and the oil-containing refrigerant stream, such that there is reduced or no concern by the user of the process in relation to possible oil freezing and clogging of the heat exchanger caused by variation of the flow or flow rate of the oil-containing refrigerant stream.

An electric motor for a vapor compression system is disclosed. The electric motor is provided with a working fluid. The electric motor includes a housing forming cavity therein. The housing includes a rotor, a stator, and a shaft. The rotor is secured to the shaft and the stator surrounds at least a portion of the rotor. An airgap is formed between the rotor and the stator. An inlet of the housing receives the working fluid and is in fluid communication with the airgap. An outlet of the housing is in fluid communication with the airgap and receives the working fluid from the airgap. The electric motor further includes an impeller that induces flow of the working fluid between the inlet and the outlet.

An electric motor for a vapor compression system is disclosed. The electric motor is provided with a working fluid. The electric motor includes a housing forming cavity therein. The housing includes a rotor, a stator, and a shaft. The rotor is secured to the shaft and the stator surrounds at least a portion of the rotor. An airgap is formed between the rotor and the stator. An inlet of the housing receives the working fluid and is in fluid communication with the airgap. An outlet of the housing is in fluid communication with the airgap and receives the working fluid from the airgap. The electric motor further includes an impeller that induces flow of the working fluid between the inlet and the outlet.

A multi-type air conditioning device controls an evaporation temperature and a condensing temperature, depending on required capacity of an indoor unit. The air conditioning device compares a current evaporation temperature or condensing temperature with a reference value, of an evaporation temperature or an condensing temperature, corresponding to a lower limit flow rate, of a gaseous refrigerant, required for refrigerating machine oil not to accumulate in, but to flow through, the gas branch pipes, and calculates an amount of the refrigerating machine oil accumulated in a gas branch pipe which does not satisfy the lower limit flow rate. When the calculated amount exceeds a set amount, the air conditioning device performs oil collecting operation, and controls the oil collecting operation in view of a flow rate of a gaseous refrigerant in gas branch pipes.

A refrigeration system has: (a) a fluid tight circulation loop including a compressor, a condenser and an evaporator, the evaporator having at least three evaporator zones, each evaporator zone having an inlet port, the circulation loop being further configured to measure the condition of the refrigerant with a refrigerant condition sensor disposed within the evaporator upstream of the evaporator outlet port; and control the flow of refrigerant to the evaporator based upon the measured condition of the refrigerant within the evaporator, and (b) a controller for controlling the flow rate of refrigerant to the evaporator based upon the measured condition of the refrigerant within the evaporator upstream of the evaporator outlet port.

A cooling system drains oil from low side heat exchangers to vessels and then uses compressed refrigerant to push the oil in the vessels back towards a compressor. Generally, the cooling system operates in three different modes of operation: a normal mode, an oil drain mode, and an oil return mode. During the normal mode, a primary refrigerant is cycled to cool one or more secondary refrigerants. As the primary refrigerant is cycled, oil from a compressor may mix with the primary refrigerant and become stuck in a low side heat exchanger. During the oil drain mode, the oil in the low side heat exchanger is allowed to drain into a vessel. During the oil return mode, compressed refrigerant is directed to the vessel to push the oil in the vessel back towards a compressor.

A refrigerant circuit includes a first compressor connected to a first suction pipe and a first discharge pipe and configured to compress a refrigerant, a second compressor connected to a second suction pipe and a second discharge pipe and configured to compress the refrigerant discharged from the first compressor, a radiator, and a high-pressure passage connecting the second discharge pipe and the radiator. A first oil drain passage guides an oil in the second compressor to one of the first suction pipe and an intermediate port of the first compressor, without via the high-pressure passage.

An accumulator fixing device for a compressor includes a bracket body, a first arm portion extending from the bracket body and coupled to an accumulator, and a second arm portion extending from the bracket body and coupled to a housing of a compressor. The bracket body has a cavity formed concavely on one surface facing the compressor to reduce vibration generated and transmitted from the compressor.

A fluid temperature control system cools a fluid by means of a multiple refrigeration apparatus including a high-temperature-side refrigerator (100), a medium-temperature-side refrigerator (200) and a low-temperature-side refrigerator (300). The medium-temperature-side refrigerator (200) in the multiple refrigeration apparatus has a medium-temperature-side first evaporator (204) and a medium-temperature-side second evaporator (224). A high-temperature-side evaporator (104) of the high-temperature-side refrigerator (100) and a medium-temperature-side condenser (202) of the medium-temperature-side refrigerator (200) constitute a first cascade condenser (CC1). The medium-temperature-side second evaporator (224) of the medium-temperature-side refrigerator (200) and a low-temperature-side condenser (302) of the low-temperature-side refrigerator (300) constitute a second cascade condenser (CC2). The medium-temperature-side refrigerant and the low-temperature-side refrigerant are the same refrigerant. The fluid allowed to flow by a fluid flow apparatus is cooled by the medium-temperature-side first evaporator (204) of the medium-temperature-side refrigerator (200), and is then cooled by the low-temperature-side evaporator (304) of the low-temperature-side refrigerator (300).

This disclosure relates to a compressor having a shaft, wherein the shaft is hollow to define a fluid passage extending along the shaft and a motor arranged along the shaft. A motor cooling line is configured to convey a cooling fluid to the motor, wherein the motor cooling line is fluidly connected to the fluid passage. The compressor may be a refrigerant compressor used in a heating, ventilation, and air conditioning (HVAC) chiller system.