The throttling mechanism is one of the important parts in the refrigeration device, its function is to reduce the pressure of the saturated liquid (or supercooled liquid) under the condensing pressure in the condenser or the liquid receptacle to the evaporating pressure and the evaporating temperature after throttling, to achieve cooling purposes, adjust the flow of refrigerant into the evaporator to adapt to the evaporator load changes, the common throttling mechanism has the following several.