Points for Attention in Selection of Screw Chillers

Date:Apr 08, 2020

Screw chillers are named screw chillers because their key components, compressors, are screw type.  It can be divided into water-cooled screw chillers and air-cooled screw chillers according to different heat dissipation modes.

The refrigerating capacity of screw chillers ranges from 92880Kcal/h to 747760 kcal/h, and the compressor power can range from 8 kw to 1280 kw. it can be widely used in various industries with extremely large refrigerating capacity, with dozens of models to choose from.  So when choosing screw chillers, what should we start from?  The chief engineer of Shanghai meileke refrigeration equipment co., ltd. will take you to analyze the matters needing attention in selecting screw chillers:

1. The selection of screw chillers should be considered according to the cooling load and the intended use.  For the refrigeration system with low load and long operation time, it is suitable to select multi-head piston compressor or screw compressor, which is convenient for conditioning and energy saving. It is also commonly known as double-head screw chiller. With the change of load, the chiller can automatically determine the number of starts to ensure the starting compressor is in a good working state, thus effectively saving electric energy.

2. When selecting screw chillers, priority should be given to those with higher performance coefficient values.  According to previous statistics, the normal chiller's operating time under 100% load accounts for less than 1/4 of the sub-operating time.  The operating time ratio of 100%, 75%, 50% and 25% load within the sub-operating time is approximately 2.3%, 41.5%, 46.1% and 10.1%.  Therefore, when selecting chillers, priority should be given to chillers with relatively flat efficiency curves.  At the same time, the adjustment range of chiller load should be considered in the design and selection. The multi-head screw chiller has excellent partial load performance and can be selected according to the actual situation of the factory.

3. When selecting screw chillers, attention should be paid to the conditions of nominal working conditions.  The actual cooling capacity of water chillers is related to the following two points:

A, cold water outlet temperature and flow rate;

B, cooling water inlet temperature, flow rate and fouling coefficient.

4. When selecting screw chillers, attention should be paid to the normal working scope of this type of screw chillers, mainly because the current limit of the motor is the current value of shaft power under surface working conditions.

5. Attention should be paid when designing and selecting screw chillers: under nominal operating flow rate, the outlet temperature of cold water of water-cooled units 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 categories, when understanding whether the use category of the compressor is allowed and whether the power of the auxiliary motor is sufficient.

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