The liquid refrigerant in the evaporator absorbs heat from the water and begins to evaporate when the chiller refrigerant recirculation system, a certain temperature difference between the ultimate refrigerant and water, the liquid refrigerant is also completely evaporated to a gaseous state and then sucked in and compressed by the compressor, gaseous refrigerant absorbs heat through the condenser, condensed into a liquid, after throttling through the thermal expansion valve turn into low temperature and low pressure refrigerant into the evaporator, complete the refrigerant cycle.