The amount of water vapor in the compressed air is determined by the temperature of the compressed air: reducing the temperature of the compressed air reduces the amount of water vapor in the compressed air while maintaining the constant pressure of the compressed air, and the excess water vapor condenses. Into a liquid. The dryer (refrigerated dryer) uses this principle to use refrigeration technology to dry compressed air. Therefore, the dryer (refrigerated dryer) has a refrigeration system. In the refrigeration system of a cold dryer, the evaporator is a device for conveying a cold amount, in which the refrigerant absorbs the heat of the compressed air to achieve the purpose of dehydration and drying. The compressor is the heart and acts to draw, compress, and deliver refrigerant vapor. The condenser is a device that emits heat, and the heat absorbed in the evaporator is transferred to a cooling medium (such as water or air) along with the heat converted from the input power of the compressor. The expansion valve/throttle valve acts as a throttle to reduce the pressure of the refrigerant, simultaneously controls and regulates the amount of refrigerant liquid flowing into the evaporator, and divides the system into two parts, a high pressure side and a low pressure side. In addition to the above components, the SSS type dryer also includes energy regulating valves, high and low pressure protectors, automatic drain valves, control systems and other components.