An Analytical Study of Laminar Counterflow Concentric-Tube Heaters with External Refluxes

• Main Authors: Yang Wen Yi, 楊文儀
• Other Authors: Ho Chii Dong
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/91318634326200969023

碩士 === 淡江大學 === 化學工程學系 === 89 === A new device of counterflow heat exchangers in concentric tubes with uniform wall temperature and with external refluxes has been designed. An orthogonal expansion technique for solving such a conjugated Graetz problem is developed and applied to investigate a substantially improving the heat transfer. An expression for calculating an infinite series of both positive and negative sets of eigenvalues and eigenfunctions was set up. Theoretical results show that the recycle-effect can enhance the heat transfer rate for large Graetz numbers were comparing with that in an open tube (without an inner tube inserted and without recycle). Competition between preheating effect and residence-time effect can be used to explain the heat transfer behavior. The effect of inserter location on the enhancement of heat transfer efficiency as well as on the increment of power consumption has also been discussed.