1. The important control parameters of screw Chiller are the refrigeration performance coefficient, additional refrigeration capacity, input power and refrigerant type.　　
2. The selection of chillers should be considered in accordance with the cooling load and usefulness. For refrigeration systems with long periods of time under low-load operating conditions, multi-head piston shortening units or screw-type shortening units should be selected for easy adjustment and energy saving.
3. When choosing a chiller, give priority to the unit with a higher coefficient of performance. According to material statistics, the operating time of individual chillers at 100% load accounts for less than 1/4 of the total operating time. The proportions of 100%, 75%, 50%, and 25% load operating time in the total operating time are roughly 2.3%, 41.5%, 46.1%, and 10.1%. Therefore, when selecting chillers, priority should be given to models with a flat efficiency curve. At the same time, the adjustment scale of the chiller load should be considered when designing and selecting. The multi-head screw chiller has excellent partial load performance and can be selected in accordance with the reality.　　
4. When choosing a chiller, you should face up to the nominal working conditions. The actual cold output of the chiller is related to the following components: a) the temperature and flow of the cold water outlet; b) the inlet temperature, flow and fouling coefficient of the cooling water.　　
5. When selecting a chiller, you should face up to the normal operating scale of the type of unit. The current limit of the main motor is the current value of the shaft power under the nominal operating condition.　　
6. In the design and selection, we should face up to it: under the nominal working condition flow, the outlet temperature of the cold water should not exceed 15℃, and the outdoor dry bulb temperature of the air-cooled unit should not exceed 43℃. If it is necessary to exceed the above-mentioned scale, you should understand whether the operation scale of the shortened machine is acceptable, and whether the power of the main motor is sufficient.