The Effect of Moisture Evaporating from the Cooling Coil Back to Space on System Performance

• Main Authors: Huang Shih Wei, 黃世偉
• Other Authors: M. T. Ke
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/30856853340343249297

碩士 === 國立臺北科技大學 === 冷凍與低溫科技研究所 === 89 === This research is to investigate the defect of an air conditioner that evaporates and blows the moisture on the cooling coil back to the room space during compressor off cycle. This results are in thermal discomfort owning to the rising of humidity inside conditioned space. Experiments and numerical simulations were performed with changing various parameters such as coil layout, supply air velocity, fin pitch, evaporator coil spacing tube diameter and its surface temperature. In order to reduce the moisture blowing back to the minimal extend. Two window-type air conditioners A and B were tested and the temperatures on cooling coil and air side, air flow rate as well as power consumptions under various conditions were obtained. The experimental results show that the amount of condensate on coil evaporating back to room space is very small using the newer air conditioner A for the hydrophilic coating of evaporator coil. It is also found that the refrigerant equilibrium time needed upon compressor sheeting down is about 30 minutes. On the other hand, the moisture blowing back to the space makes the cooling load rising about 19﹪ at supply air flow rate 193.8 CFM during the 30 minutes of equilibrium time when using the order air conditioner B. A 3D simulation model was also established based on computational fluid dynamics to evaluate this phenomena. The numerical results using B as benchmark shows that, the restrain of total heat blowing back when off cycle under various conditions. When the coil layout was changed from staggered type to in-line type, the air velocity decreased from 1.182m/s to 0.4m/s, the fin pitch was changed from 14FPI (fin per inch) to 10FPI, tube surface temperature was changed are 0.3﹪, 1.1﹪, 1.5﹪and 80﹪ respectively. While the effects of changing evaporator tube spacing and diameter on reducing the total heat blowing back are very small.