For the indirect cooling method, glycol liquid as the secondary coolant is cooled in the refrigerating unit, pumped to the cooler in the house to cool the air.

Analyses and calculates the thermal characteristics of the key equipment-air cooler for indirect free cooling tower used in communication rooms.

According to the theory of indirect evaporative cooler, heat can be taken away through water evaporation by wrapping water absorbent film on the cooling surface of air conditioner condenser.