Performance Simulations of Ceramic Recuperator and Stairshaft Pressurization Systems by STAR-CD
本文應用 STAR-CD 套裝軟體分別模擬兩個案例。第一個案例為模擬兩50KW陶瓷板式熱交換器（材料分別為碳化矽以及堇青石）之溫度場及壓力場．並利用此數據作接下來之熱應力之分析。裝設的環境，其廢熱側進口溫度為1000℃，預熱側進口溫度為27℃。因為計算格點將近兩百二十萬個，為了提高計算的效能，本案例使用STAR-CD平行計算軟體來處理。模擬出來的結果顯示碳化矽及堇青石兩熱交換器其總熱傳量分別為56.74 KW和56.72KW。和傳統經驗公式比較的誤差為2~4%，由此可見模擬結果相當的準確。此案例模擬出來的速度場和壓力場可提供作為陶瓷板式熱交換器的熱應力計算，這是傳統經驗所無法辦到的。
ABSTRACT This thesis utilizes a commercial code, STAR-CD, to simulate two projects. The first part is to predict the thermal and pressure flow field inside two 50W ceramic compact heat exchangers to provide the input data for the following thermal stress analysis. The ceramic materials used in the heat exchanger are SiC and MAS, respectively. In the operation condition, the highest temperature in exhaust gases is 1000□C, whereas the lowest one in preheated air is 27□C. In order to calculate efficiently, a parallel computing algorithm is used to handle the large number of grids, 2,200,000 approximately. The predicted total heat transfer rates of the SiC and MAS recuperators are about 56.74 and 56.72kW. The difference between the predicted heat transfer rate using STAR-CD and the analytic one is only about 2~4%, indicating that the predicted heat transfer rate is quite accurate. The predicted temperature and pressure profiles from the present study are used to compute the thermal stress analysis of Ceramic Plate Recuperator, whereas the analytic ones can not provide such information. The second part is to evaluate the stairshaft pressurization system in a high-rise building. The story number of the stairshaft is 21 and 4 of which are underground. The supply air fan with a capacity of 19000 CMH is set on the roof. In order to understand the different effects on the performance of smoke prevention, three models of stairshaft configuration, the stairshaft without stairs, the stairshaft connecting with lobbies, and the stairshaft with scissors-typed stairs are established respectively. The varying parameters are the door with or without weather strip (leakage effect), the fire door opening conditions, closed or opened, and the use of compressible or incompressible flow assumptions. The simulation results show the installation of door weather strip is found beneficial to pressurization, however, the conditions of opened or closed fire door affect the pressure distributions in stairshaft more effectively. Besides, the stairshaft with or without stair has decisive influence on the predict results. The flow with incompressible flow assumption can not show the density which becomes higher due to compression in the top levels. Finally, the predict results by STAR-CD show the capacity of supply fan using analytic method may have the risk of insufficient pressure.
|Appears in Collections:||Thesis|