CFD numerical simulation study of an indoor space with the underfloor air distribution system under different heating source conditions

• Main Authors: Yu-Wen Wang, 王郁雯
• Other Authors: Yi-Jiun Lin
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/2v4ea4

碩士 === 國立臺灣科技大學 === 機械工程系 === 107 === This study uses CFD simulation software to study the indoor environment characteristics of the space with the underfloor air distribution (UFAD) system. There are two parts of this study. The first part of this CFD simulation study is to verify the numerical model, and that was conducted by comparing the numerical simulation results with the experimental measurements in a real building. The heat transfer condition on the boundary plays a significant role in the simulation model. The following two heat transfer boundary conditions are considered in this indoor space. One is the constant temperature, and the other is the constant heat flux. The convection heat transfer coefficient is estimated in the regime of forced convection for a vertical plate. This study shows that the simulation cases of two different boundary conditions with similar total heat transfer rates give approximate temperature stratification results. The simulation cases with the proper total heat transfer rates provide reasonable temperature stratification results compared with the experimental field measurements in a real building. The second part of this study investigates the characteristics of temperature distribution in the space which has different heat source conditions, i.e. heating by the surrounding walls and the ground floor. The simulation results show that the stratification height of the ground floor heating case is less than that of the surrounding walls heating case for the same supply flow rate. The throw height of the supply air from the diffuser is about 1.3 times the buoyant jet length scale for the surrounding walls heating case. In the ground floor heating case, the throw height is about 1.19 times and 1.14 times the buoyant jet length scale. The results show that the ground floor heating case may induce unsatisfied draught rating at 0.3 m due to the velocity difference to large. The results reveal that the heating location condition not only changes the stratification height but also varies the temperature distribution performances, especially for the upper layer. In the surrounding walls heating case, the largest temperature gradient takes place in the upper layer. In general, the stratification height and the transition layer are higher when the supply air flow rate increases.