Type of Screw Chiller:
The screw-type chilled water units can be categorized into water-cooled and air-cooled types. The water-cooled version uses a cooling tower for water circulation to dissipate heat, whereas the air-cooled screw-type chilled water unit employs finned air for heat dissipation.
Key Selection Points for Screw Chiller:
The main control parameters of a screw-type chill water unit include the coefficient of performance, rated cooling capacity, input power, and type of refrigerant.
2. The selection of a chilled water unit should consider the cooling load and application. For refrigeration systems with longer operation at low load, it is advisable to choose a multi-head piston compressor set or a screw compressor set for ease of adjustment and energy savings.
When selecting a chilled water unit, prioritize those with higher performance coefficient values. According to statistics, chilled water units typically operate at full load for less than 1/4 of the total running time throughout the year. The proportion of running time at 100/75/50/25% load during the total running time is approximately 2.3%, 41.5%, 46.1%, and 10.1%, respectively. Therefore, when selecting chilled water units, it is advisable to opt for models 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 system, attention should be given to the nominal operating conditions. The actual cooling capacity of the chilled water system 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 chilled water unit, pay attention to the normal operating range of the unit model, primarily the current limit of the main motor, which is the current value of the shaft power under the nominal operating conditions.
6. In design selection, attention should be paid to: Under nominal operating flow conditions, the outlet temperature of chilled 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 the above range, it is important to understand whether the compressor's operating range allows for it and if the power of the main motor is sufficient.
