Screw Type Water Chiller

1. Working principle of screw type water chiller

The screw type industrial water chiller is named screw chiller because of its key component-the compressor adopts the screw type. The unit consists of a gas refrigerant in the state from the evaporator; after adiabatic compression by the compressor, it becomes a high temperature and high pressure state. The compressed gas refrigerant is cooled and condensed at equal pressure in the condenser, and then changes into a liquid refrigerant after condensation, and then expands to a low pressure through a throttle valve and becomes a gas-liquid mixture. Among them, the liquid refrigerant under low temperature and low pressure absorbs the heat of the substance to be cooled in the evaporator and becomes a gaseous refrigerant again. The gaseous refrigerant re-enters the compressor through the pipeline to start a new cycle. These are the four processes of the refrigeration cycle. It is also the main working principle of the screw chiller.

2. Key points for selection of screw water chiller

a. The main control parameters of the screw chiller are the refrigeration performance coefficient, rated refrigeration capacity, input power and refrigerant type, etc.

b. The selection of the chiller should be considered according to the cooling load and purpose. For refrigeration systems under low-load operating conditions for a long time, multi-head piston compressor units or screw compressor units should be selected for easy adjustment and energy saving.

c. When selecting chillers, give priority to units with higher coefficient of performance. According to statistics, the average operating time of chillers at 100% load throughout the year accounts for less than 1/4 of the total operating time. The proportions of 100%, 75%, 50%, and 25% load operating time of 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 relatively flat efficiency curve. At the same time, the load adjustment range of the chiller should be considered when designing and selecting. The multi-head screw chiller has excellent partial load performance and can be selected according to actual conditions.

d. When selecting a chiller, pay attention to the conditions of the nominal working condition. The actual cooling capacity of the chiller is related to the following factors:

a) Outlet temperature and flow rate of cold water;

b) The inlet temperature, flow rate and fouling coefficient of the cooling water.

e. When selecting a chiller, pay attention 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 the nominal operating conditions.

f. Attention should be paid to the design and selection: 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 range, it should be understood whether the applicable range of the compressor is allowed and whether the power of the main motor is sufficient.