- 學位論文
週期性擺動葉片對具有入出口的正方形容器內熱傳與質傳之影響
The Effect of a Guide Vane with Periodic Swing on the Heat and Mass Transfer within a Square Cavity with Inlet and Outlet Ports
摘要
過去的空調設計主要目的著重於室內溫度控制，使得室內環境可以達到冬暖夏涼，但隨著時代的進步，空調的功能不再僅止於提供冷房舒適，室內空氣品質不佳也經常造成人體健康的危害，所以近年來室內空氣品質便成了研究室內空調重要的一環。目前國內外的研究大多局限於噴流對室內空間穩態流場的影響，對動態流場的文獻分析甚少，然而實際環境下卻是送風葉片不斷的擺動，因此增設一具有週期性擺動之送風葉片，可改變進風風向及增加室內空間內流體的流動性，並有效排除室內空間的熱源及污染源並達到所謂健康空調的要求。本文利用計算流體力學軟體FLUENT模擬週期性擺動之送風葉片在不同振幅與頻率下對空間內壓損及熱質傳之影響。由模擬結果之流線圖得知隨著葉片向上擺動角度越大時，因噴流誘導可增加室內空間氣流流動；隨著葉片向下擺動角度越大時，渦流的強度(或尺寸)會逐漸增強，影響室內空間氣流流動。最後探討頻率與振幅對室內空間氣流之影響，發現固定頻率比較不同振幅下，擺動振幅15 o時有較低的壓損及較佳的熱質傳性能；固定振幅比較不同頻率下發現當頻率越大時葉片擺動的速度越快則空間內的渦流的強度(或尺寸)會逐漸增強，造成空間內熱質傳性能變差。
並列摘要
Air-conditioning in earlier days mainly focused on the control of indoor air temperature for improving the year-round indoor environment. With the development of our modern society, the function of air-conditioning no longer just provides the desired thermal comfort in the indoor space. Poor indoor air quality (IAQ) in the air-conditioned indoor space often results in human health hazards, and the IAQ issue has become one of the most important research topics in the HVAC industry recently. Most previous studies mainly focused on the effect of air jets on the steady flow in the space. Little research on the dynamic flow field was published. However, in reality, the air-supply is projected with the simultaneously swinging guide vane. Therefore, the addition of an air-supply guide vane with periodic swinging motion helps to project the direction of wind flow and increase the mobility of indoor air, and thus can effectively extract both the heat and pollution sources in the space and achieve the healthy air-conditioning requirements. In this study, the CFD software-FLUENT was applied to simulate the effects of periodic swinging frequency and amplitude of air-supply guide vane on the pressure loss, heat and mass transfer. Based on the results, with the increasing upward swinging angle of guide vane, the streamlines indicated that the projected air jets will induce air motion better in the space and increase the mobility of indoor air. Adversely, the strength of the vortex (or size) will gradually increase and affect the air flow in the space with the increasing downward swinging angle of guide vane. It is also found that the varied frequency and amplitude of the swinging guide vane have important impact on the air flow in the space. For varied swinging amplitude and fixed frequency, the case with swinging amplitude of 15 o shows lower pressure loss and better heat and mass transfer performance. Meanwhile, for varied swing frequency and fixed amplitude, the strength of the vortex (or size) will gradually increases within the space as the guide vane swings faster (with higher frequency) , resulting in the deterioration of heat mass transfer performance within the indoor space.