A study on extraction mechanical displacement ventilation

• Main Authors: Jia-Ying Wu, 吳佳盈
• Other Authors: none
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/05985355163238895857

碩士 === 國立臺灣科技大學 === 機械工程系 === 103 === The purpose of this research is to study the extraction mechani- cal displacement ventilation and investigate the effects of the supply source and the extraction sink on mechanical displacement ventila- tion. The salt-bath technique is employed to conduct the experi- ments by using the acrylic reduced-scale model. A partition with an opening was placed in the middle of the acrylic reduced-scale model to divide the model into two individual chambers. According to the partition opening area, the experimental are categorized as two series, Ex(I) and Ex(II). The partition opening area of Ex(I) and Ex(II) is and 51 cm2 respectively. Each series includes four differ- ent extraction flow rate, Qex = 1,2,3 and 4 LPM. The density plume as a buoyancy source is placed on the top of the forced room and extraction device is installed on the bottom of the forced room. The environmental fluid flow throw in the opening on the top of the un- forced room. Experimental results show that as the extraction flow rate increases, the distance from the plume source to the interface height increases; and the density of the buoyancy layer decreases. The stratification stability highly depends on the inflow momentum. The smaller partition opening area induces the larger inflow momen- tum, such as Ex(I) series of experiments. The mixed layer of Ex(I) is more noticeable than that of Ex(II) for a give extraction flow rate. Comparisons between extraction mechanical displacement ventila- tion and supply mechanical displacement ventilation show that the intensity contour of the supply mechanical displacement ventilation is almost horizontal and that means the intensity is the same at the same level. The influence of sink on extraction mechanical dis- placement ventilation is apparent. When the extraction flow rate increases, the sink effect radius, rex, and the sink velocity at the sink effect radius, Vs(rex), increases. It causes the intensity difference be- tween the sink outlet and the distance away from it at the same level become sigificant. The intensity contour near the sink outlet has a vertical distribution. As the distance away from the outlet increases, the intensity at the same level decreases, i.e. the density increases.