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研究生:秦銘志
研究生(外文):Ming-Chih Chin
論文名稱:CFD於溫室系統模擬之應用
論文名稱(外文):Application of Greenhouse System Simulation by CFD
指導教授:蔡循恒蔡循恒引用關係
指導教授(外文):Hsun-Heng Tsai
學位類別:碩士
校院名稱:國立屏東科技大學
系所名稱:機械工程系
學門:工程學門
學類:機械工程學類
論文種類:學術論文
論文出版年:2006
畢業學年度:94
語文別:中文
論文頁數:65
中文關鍵詞:溫室數值模擬太陽熱輻射
外文關鍵詞:greenhousenumerical simulationsolar radiation
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本研究主要以密閉型溫室為對象進行數值模擬分析,探討溫室在太陽熱輻射照射下,溫室水牆運作及停止時,熱輻射對溫室內部所產生之溫室效應的影響進行模擬;模擬過程中主要使用DO熱輻射模式,調整太陽黑體放射率、材質的吸收係數及漫射分率三種參數設定,搭配太陽熱輻射量對於地面溫度變化之模擬,以快速選取太陽黑體放射率,並配合實驗量測數據之驗證,以確定模擬之準確性。
由模擬結果可知,當溫室水牆運作時可降低溫室內部溫度,使內部溫度低於環境溫度,並有效抑止溫室效應在溫室內發生;而水牆運作與否對於溫室內部流場趨勢並無太大之影響,但均會在水牆上方形成迴流現象造成熱量之累積;本論文最後將溫室實驗所量測之數據與模擬結果相互比對,兩者間溫度最大誤差位於水牆關閉溫室地面處為1.52 %,而溫度最小誤差位於水牆入口處為0.06 %。藉由本模擬結果可作為事先預測溫室內部溫度分佈,使溫室在改良時有參考依據,並減少時間與金錢之浪費。
This research studies the fluid and temperature fields in a close greenhouse under the influence of solar radiation mainly by the means of computational fluid dynamics (CFD). The influence of greenhouse effects due to solar radiation is further understood through simulation for the water wall in the greenhouse is either in operation or totally turned off. By using discrete ordinates (DO) radiation model, the ground temperature changes obtained through CFD approach was compared with the actual measurements. The three most critical input parameters for the DO radiation model including the blackbody emissivity, the absorption coefficient, and the diffusion fraction of material were individually adjusted so that the corresponding CFD results agreed with the measurements. To speed up the process to determine the sun blackbody emissivity, a photometer was used to provide a good initial guess. After that, a simulation was performed using these three parameters and its result was compared with the experimental data to confirm the accuracy of the simulation.
According to the simulation results, a water wall in operation in a greenhouse can effectively reduce the temperature in the greenhouse and therefore restrain the greenhouse effects from taking place in the greenhouse. However, the water wall in operation has very little influence on the airflow in the greenhouse. Regardless of the situations whether the water wall is in operation or not, there exists a flow circulation at the corner between the water wall and the greenhouse roof where heat accumulation takes place and leads to an increase in local temperature. For the case for which the water wall is not in operation, the maximum relative error between several ground temperature measurements in the greenhouse with their associated simulation results was 1.52 %. Furthermore, the minimum relative error was found to be 0.06 % at the velocity inlet on the water wall. Apparently, simulation results can predict the temperature distribution in the greenhouse and can be used as a guide to improve greenhouses without wasting a great deal of time and money.
目錄
摘要…I
Abstract…II
誌謝…IV
目錄…V
表目錄…VII
圖目錄…VIII
符號索引…X
第1章 前言…1
1.1 研究背景…1
1.2 研究動機…2
1.3 文獻回顧…3
第2章 數學模型…7
2.1 統御方程式…8
2.2 紊流模式…10
2.3 多孔隙介質統御方程式…13
2.4 熱輻射模式…15
2.4.1 不透明壁面邊界之定義…16
2.4.2 半透明壁面邊界之定義…18
第3章 數值方法與驗證…20
3.1 數值方法…20
3.1.1 離散化…20
3.1.2 壓力與速度(pressure-velocity coupling)之耦合算法…24
3.1.3 格點系統…25
3.1.4 收斂標準…25
3.2 數值方法驗證…26
3.2.1 實驗數據量測…26
3.2.2 實驗量測結果…29
3.2.3 數學模型驗證…29
3.2.3.1 幾何模型與初始條件…29
3.2.3.2 數學模型與邊界條件…30
3.2.4 數值模擬結果…31
3.2.4.1 幾何模型黑體放射率調整…31
3.2.4.2 材質漫射分率之調整…33
3.2.4.3 玻璃材質吸收係數之調整…37
3.2.5 數值模擬驗證之討論…40
第4章 結果與討論…41
4.1 溫室幾何外型與網格系統…41
4.2 邊界條件設定…43
4.3 數值模擬結果…44
4.3.1 水牆關閉…44
4.3.1.1 溫度分佈情形…44
4.3.1.2 溫室內流場情形…50
4.3.2 水牆啟動…52
4.3.2.1 溫度分佈情形…52
4.3.2.2 溫室內流場情形…58
第5章 結論…61
5.1 結論…61
5.2 未來展望…61
參考文獻…62
作者簡介…65
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