Optimal Design of Finned-Tube Heat Exchangers and Thermal Analysis by ANSYS

• Main Authors: SU, CHE-WEI, 蘇哲緯
• Other Authors: Liaw, Shih-Pin
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/81354056304731466292

碩士 === 國立臺灣海洋大學 === 機械與機電工程學系 === 104 === The objective of this study is to optimize the design work of finned-tube air heaters. Water, steam and Dowtherm oil are chosen to be the hot working fluids. First, a single fin tube is investigated experimentally, and the measured temperatures and fin efficiency are verified by theoretical curves and Ansys software. During the thermal analysis, the LMTD method is applied. The pressure drop as well as heat transfer coefficients have been calculated in both the tube and shell sides. The length of tube, the height and pitch of fins, number of passes, and layout are varied parametrically. The computer program was coded in Microsoft Excel which includes fluid physical properties query systems, especially accompanied with a VB program to fit the required operating pressure. First, the energy balance was checked, and then the basic information includes sizes of the tube and fin array were served as input to the code. A preliminary design can be accessed once the fluid velocity inside the tube and the overall heat transfer coefficient are guessed,. Finally, the design is optimized by modifying the input parameters. Through structural analysis, it is found that in the same tube pace, reduction in the height of the fins can improve the fin efficiency, whereas the total heat transfer rate anf pressure drop decrease simultaneously. The optimum fin height is between 8 and10mm. The increase in number of passes in tube side can increase the velocity significantly which results in enhance the heat transfer rate. The effect of fin array allocation is also studied. Finally, the simulation results reveals that the locations of inlet and exit of the fluids appears the differences in temperature and pressure distributions, which can provide the reference of the design work.