The intercooler is suitable for use in a two-stage or multi-stage chilled water chillers refrigeration system, connected between the low pressure class exhaust pipe and the high pressure level suction pipe, to avoid the water chiller high pressure level compressor exhaust temperature is too high, so that the refrigerant The liquid gets supercooled before entering the evaporator. In the water chiller, the high-pressure liquid refrigerant from the condenser enters the intercooler in two ways into the serpentine coil, and the other enters the shell of the container into the space outside the coil. There are three functions of the intercooler: one is to reduce the water chiller low-level exhaust temperature, the second is to separate the water chiller low-level exhaust in the entrainment of lubricating oil, the third is to cool the serpentine coil of liquid refrigerant to make it cool. Thus, the intercooler is a heat exchanger belonging to the refrigerant in the water chiller. It is important that the refrigerant level in the intercooler be kept constant. Such as ammonia two-stage compression water chillers, the system used in the intercooler is a float valve or liquid level controller and liquid supply solenoid valve as a liquid supply device. The Freon two-stage compressed water chillers, which use the intercooler is the use of thermal expansion valve as a liquid supply device.