Screw Chiller Type:
The screw chillers can be divided into water-cooled and air-cooled types based on their cooling methods. The water-cooled version uses a cooling tower water circulation system for heat dissipation, while the air-cooled screw chillers utilize finned air cooling.
Key Selection Points for Screw Chiller:
1. The main control parameters of a screw-type chill water unit include the coefficient of performance (COP), rated cooling capacity, input power, and refrigerant type.
2. The selection of a chilled water unit should be based on the cooling load and application. For refrigeration systems with long operating hours at low load conditions, it is advisable to choose multi-head piston compressor units or screw compressor units, which are convenient for adjustment and energy-saving.
3. When selecting a chilled water unit, prioritize those with higher performance coefficient values. According to statistics, the chilled water units typically operate at full load for less than 1/4 of the total running time throughout the year. The operating time ratios for 100/75/50/25% loads during the total running time are approximately 2.3%, 41.5%, 46.1%, and 10.1%, respectively. Therefore, it is advisable to choose units with flatter efficiency curves. Additionally, when designing and selecting, consider the load adjustment range of the chilled water unit. Multi-head screw chilled water units have excellent part-load performance and can be selected based on actual conditions.
4. When selecting a chilled water unit, attention should be given to the nominal operating conditions. The actual cooling capacity of the chilled water unit is related to the following factors:
a) Cold water outlet temperature and flow rate;
b) Inlet water temperature, flow rate, and dirtiness factor for cooling water.
5. When selecting a chill water unit, pay attention to the normal operating range of the unit model, mainly the current limit of the main motor, which is the current value of the shaft power under the nominal operating condition.
6. When selecting the design, pay attention to the following: Under the nominal operating flow rate, the outlet temperature of the cold water should not exceed 15°C, and the outdoor dry bulb temperature of the air-cooled unit should not exceed 43°C. If it is necessary to exceed these limits, ensure that the compressor's operating range permits it and that the main motor's power rating is sufficient.
