The main control parameters of a screw chiller are the refrigeration performance coefficient, rated cooling capacity, input power, and refrigerant type.
The selection of water chillers should be considered based on the cooling load and purpose. For refrigeration systems that operate at low loads for a long time, it is advisable to select a multi head piston compressor unit or a screw compressor unit for ease of regulation and energy conservation.
When selecting chillers, priority should be given to units with higher performance factors. According to data statistics, the operation time of general water chillers at 100% load throughout the year accounts for less than 1/4 of the total operation time. The operating time ratio of 100%, 75%, 50%, and 25% load within the total operating time is approximately 2.3%, 41.5%, 46.1%, and 10.1%. Therefore, when selecting chillers, priority should be given to models with relatively flat efficiency curves. At the same time, the adjustment range of the chiller load should be considered during design and selection. The multi head screw chiller has excellent partial load performance and can be selected according to actual conditions.
When selecting a water chiller, attention should be paid to the nominal operating conditions.
The actual cooling capacity of a water chiller is related to the following factors:
a) Cold water outlet temperature and flow rate;
b) Inlet water temperature, flow rate, and fouling coefficient of cooling water.
When selecting a water chiller, attention should be paid to the normal operating range of this type of unit, mainly because the current limit of the main motor is the current value of the shaft power under nominal operating conditions.
During design selection, it should be noted that under nominal operating conditions, the outlet temperature of cold water should not exceed 15 ℃, and the outdoor dry bulb temperature of air-cooled units should not exceed 43 ℃. If it is necessary to exceed the above range, it is necessary to understand whether the use range of the compressor is allowed and whether the power of the equipped main motor is sufficient.