A free cooling/vapor compression integrated air-conditioning system

which combines vapor compression refrigeration and a separate heat pipe

was proposed in this study. A first coolant and liquid-pump-driven second coolant are circulated throughout the system. The integrated system can operate on three modes: vapor compression refrigeration

dual refrigeration

and free cooling. In hot seasons

the refrigerating capacity is entirely provided by the vapor compression refrigeration unit

whereas in cold seasons

the refrigerating capacity is fully provided by the heat pipe unit. In transition seasons

the free cold source is used as much as possible by the heat pipe unit

and inadequate refrigeration capacity is supplemented by the vapor compression refrigeration unit. Moreover

a prototype of the HKF-200FH refrigeration unit is designed and tested. The compression and heat-pipe units are paralleled by a shell-tube type evaporative condenser whose tube side is used as an evaporator of the compression unit to supply refrigeration capacity to the shell-side second coolant when operating in compression refrigeration mode or dual refrigeration mode. The test results show that the refrigeration capacity of the integrated system changed little with an increasing energy efficiency ratio (EER) when the ambient temperature decreased. The refrigeration capacity in the compression refrigeration mode (ambient temperature is 35 ℃) and heat-pipe mode (ambient temperature is 10 ℃) were 197.38 and 196.89 kW with EER of 3.5 and 17.26

respectively. Since May 2014

the prototype of the HKF-200FH has been safely and reliably operated at an EB-level cloud storage laboratory in Beijing. The long-term operation results have shown an energy-saving rate of 45% compared with traditional vapor-compression-type computer room air conditioners.