Selection method of refrigeration host
The chillers used in the ice storage system need to adapt to the air conditioning and ice storage conditions, so they are often called dual-condition chillers. The available types are piston chillers, screw chillers, and two-stage or three-stage centrifugals. Type water chiller, its cooling capacity is suitable range and performance coefficient. It can be seen that the performance of centrifugal chillers is slightly better, but please note that it is best to use medium temperature and medium pressure refrigerants, such as R22, R134a, etc., for centrifugal chillers for air conditioning ice storage; The vacuum of the evaporator is too high under working conditions. Generally, ice storage air conditioning systems mostly use screw chillers.
At the same time, when designing ice storage air conditioning systems, it is also necessary to grasp the changes in the cooling capacity of the chiller under different operating conditions. Of course, this requires the help of the performance characteristics data provided by the manufacturers. When there is no specific manufacturer’s data, the design can be based on the following data:
(1) For air-conditioning conditions, when the air-conditioning water supply temperature is 7°C and the cooling water inlet temperature is 32°C, when the mass concentration of 25-30% glycol aqueous solution is used as the refrigerant, the cooling capacity is about water 97% of the refrigerant.
(2) Every time the cooling water inlet temperature decreases (or increases) by 1℃, the cooling capacity of the unit increases (or decreases) by approximately 1.3%.
(3) For every 1℃ decrease in the temperature of the water supply for air conditioning, the cooling capacity of the unit will decrease by about 3% for piston and centrifugal units, and about 2.6% for screw units. Of course, when selecting the capacity of the refrigeration unit, a margin of 5-10% should be added.
In addition, when selecting the refrigeration host of the air conditioning ice storage system, it is necessary to determine the water supply temperature of the refrigerant carrier during the ice storage period. As mentioned above, the figure shows the freezing hours of a certain coil type ice storage tank and the cold carrier The relationship between the water supply temperature of the agent. It can be seen from the figure that if the freezing hours can be as long as 12 hours, the final required water supply temperature is -5℃; if the freezing hours can only be 8 hours, the water supply temperature at the end of freezing will be as low as -6.4 ℃.
