CoolMaster variable-frequency refrigerant pump free-cooling solution adopts “dual-engine triple-mode” intelligent technology, makes full use of outdoor natural cooling sources to extend free-cooling time. Overall energy efficiency ratio of data center is significantly improved. Full variable- frequency technology supports stepless adjustment of cooling capacity, achieves more precise and energy-efficient temperature control, suitable for medium to large data centers, computer rooms, industrial control rooms, power distribution rooms, and battery rooms, etc.