Experimental and numerical studies of heat and mass transfer performance and design optimization of Fan-coil with high supply chilled water temperature in Air-Conditioning system

Raising chilled water temperature contributes to improving the energy efficiency of the water-chiller in air-conditioning (AC) system. However, the heat and mass transfer performance of fan-coil would be effected by high supply chilled water temperature (SCWT). This paper experimentally investigated the changing evolution of both cooling and dehumidity capacity of fan-coil in AC system, indicating the capacity of 3 rows fan-coil declines when SCWT rose from 9 ℃ to 12 ℃, which cannot satisfy the requirements of indoor comfort. Besides, experiment results show that increasing rows number of fan-coil is an effective way to solve the capacity decline issue. In order to further analyze the effects of fan-coil specification on its performance, the heat and mass transfer numerical model of fan-coil was proposed. The simulated results agreed with the experimental data well. The numerical analysis showing that when SCWT was 9, 10, 11, 12 ℃, the average increase of heat exchange was 561.50, 88.50, 332.73 W for rows number increasing from 4 to 6, diameter enlarging from 7 mm to 9 mm, tube spacing enlarging from 21 mm to 28.66 mm. The efficiency index was improved with smaller diameter and larger tube spacing. In order to ensure the optimal performance of fan-coil, the largest efficiency index was achieved. In this case, the corresponding SCWT was 10 ℃, which improved the COP of water-chiller by 10.8%. This work provides the design of fan-coil with high SCWT in AC system.