Due to the large energy compensation caused by the fixed dew point on the cooling coil (CC) in the conventional constant temperature and humidity air-conditioning system

a new system employing a temperature and humidity independent control device(THIC device) in the CC and a method of PID split-range control

is developed in this paper. Based on the experiment verification

the operation states and the energy saving effects of the system under different heat and moisture loads have been simulated by TRNSYS 16 software. The results show that under different working conditions

the system can automatically control air temperature and humidity independently with a high precision

by adjusting the mass flow rate and the temperature of the chilled water into the CC

and the output of the heater or the humidifier. In the design of such CC

the heat transfer area should be calculated under a higher inlet temperature of the chilled water (for example

12℃ instead of the usual 7℃). The system is energy-efficient with a rate of 30% under low temperature high humidity condition and about 50% under high temperature and low humidity condition

compared with the conventional system.