影響通風遮陽板夏季節能效益的參數模擬分析

Numerical Parametric Study of Ventilated Shading Plates Energy Performance in Summer

葉孟穎(Meng-Ying Yeh)

指導教授 ： 顏瑞和

國立臺灣大學/工學院/機械工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.01305

摘要

近年來通風遮陽板或遮陽牆系統於增強建築立面外牆夏季隔熱能力的應用逐漸增多，但文獻中對於此種通風遮陽牆的隔熱效益探討多為案例討論，缺乏各種參數與遮陽牆隔熱能力的關係式，在比較各種不同參數組合下的遮陽牆隔熱能力時會產生困難。文獻也缺乏探討流道壁面的輻射放射率的影響。本研究旨在以數值模擬分析影響遮陽板隔熱能力的變數，最終發展出包含多項參數之泛用通風遮陽板隔熱能力關係式，此關係式可使得比較各種不同參數條件下的遮陽板隔熱能力更容易。本研究使用商用計算流體力學(CFD)軟體FLUENT作為二維數值模擬分析的工具，模擬結果與文獻實驗以及實際設施的量測結果進行比較驗證。研究結果顯示壁面放射率的降低對遮陽板隔熱性能有顯著的提升；入熱量在流道寬度增大到一定程度後即不會有太大變化。本研究也分析了天氣環境變數對等效熱阻的影響，並運用熱電路節點觀念，可得到誤差更小的遮陽板等效熱阻關係式。以此為基礎拓展其適用範圍加入更多變數，最終得到了泛用的遮陽板隔熱能力關係式，只要是流道高為3m，流道寬在0.1m以上的通風遮陽板，均可利用本研究得到的泛用等效熱阻或入熱量關係式進行通風遮陽板隔熱能力的快速估算。泛用關係式的參數包括了太陽輻射量Ia、室內外溫差ΔT、等效流道壁面放射率ε_eff以及外牆體熱阻Rw。依入熱量對Ia和ΔT的敏感度分析，在太陽輻射量相對較強的地區，加入成本考量，選擇降低等效流道壁面放射率ε_eff是較合適的隔熱策略；而在室外溫度相對較高的地區，選擇提高外牆體熱阻Rw是較合適的隔熱策略。利用泛用等效熱阻進行動態模擬可在不同的天氣條件、不同的Rw、ε_eff設置下，與實際以流道進行的模擬結果比較有著不錯得一致性，因此泛用等效熱阻關係式可應用於減少動態模擬的計算時間。

關鍵字

通風遮陽板 ； 立面外牆 ； 數值模擬 ； 自然對流 ； 等效熱阻 ； 泛用關係式

並列摘要

The use of Ventilated Shading Plates or Ventilated wall systems to improve the thermal insulation of vertical walls in buildings has increased in recent years. However, most research on the energy performance of such Ventilated wall has been case studies. Due to the lack of literature reporting the energy performance correlations as functions of numerous parameters, it is difficult to compare the energy performance of Ventilated wall under different sets of parameters. There has been also relatively little research about the influence of radiation emssivity of flow channel surface. The purpose of this study was to investigate the parameters affecting the energy performance of Ventilated Shading Plates by numerical simulation and to provide a general energy performance correlations as functions of numerous parameters. These correlations permit a simple way to compare the energy performance of Ventilated Shading Plate. The simulations were conducted using commercial CFD code, FLUENT. Simulation results were compared with experimental data to validate the simulation model. Results of this study showed that thermal insulaton of Ventilated Shading Plate is increased sensibly as the radiation emssivity of flow channel surface decreased. The heat gain will not change much as the flow channel width increased to a certain extent. The influence of climatic condition on the equivalent thermal resistance of Ventilated Shading Plate was also investigated. We proposed a equivalent thermal resistance correlation with smaller error by the aid of thermal resistance network concept. Then general correlations was proposed by adding more parameters. The presented equivalent thermal resistance correlation and heat gain correlation can be used to estimate the thermal energy performance of Ventilated Shading Plate whose height and width are 3m and greater than 0.1m respectively. The general correlations are functions of absorpted solar radiation Ia, temperature difference between indoor and outdoor ΔT, effective emissivity of flow channel surface ε_eff, and thermal resistance of vertical wall Rw. The sensitivity analysis of heat gain against Ia and ΔT showed that decreasing effective emissivity of flow channel surface ε_eff is a more appropriate strategy in areas with relatively strong solar radiation. It also showed that increasing thermal resistance of vertical wall Rw is a more appropriate strategy in areas with relatively high outdoor temperature. The dynamic simulation results applying equivalent thermal resistance were in good agreement with the results from direct CFD simulations for different climate conditions and different Rw, ε_eff. Therefore, the general equivalent thermal resistance correlation can be used to reduce the computation time of dynamic simulations.

並列關鍵字

Ventilated shading plate ； External vertical wall ； Numerical simulation ； Natural convection ； Equivalent thermal resistance ； general correlations

參考文獻

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