Theoretical Study on Optimum Tube Arrangement in Shell and Tube Heat Exchanger

本课题旨在阐明管组内的流动和换热特性，并得到可用于管壳式换热器设计的换热系数和压力系数的表达式。对二维Navier-Stokes方程和能量方程进行了数值求解。在计算中，考虑了温度与黏度的关系，并采用k-二方程模型来计算湍流流态。本研究的主要结论和有待解决的问题如下：(1)对于层流流型，定量地阐明了管的布置和管的加热条件（壁温均匀或壁热流均匀）对压力和局部换热系数的影响。(2)温度相关的粘度对流动和传热特性有很大影响，需要确定一个估计粘度的参考温度，以获得这些特性的无因次相关表达式。(3)通常的k-二方程湍流模型可以应用于管库流动，但很难得到准确的结果。辐合和热平衡比层流差得多。(4)提高数值解的精度，获得压力系数和换热系数的无因次表达式，是今后需要解决的问题。

This project was carried out to clarify the flow and heat transfer characteristic in tube banks, and to obtain expressions for the heat transfer coefficients and pressure coefficients which may be used for the design of shell and tube heat exchanger. Two-dimensional Navier-Stokes and energy equations were solved numerically. in the calculations, temperature dependent viscosity is considered and k- two-equation model is applied for turbulent flow regime.The main conclusions of this study and the problems to be solved are as follows:(1) For laminar flow regime, the effects of tube arrangements and heating conditions of tubes (uniform wall temperature or uniform wall heat flux) on pressure and local heat transfer coefficients are clarified quantitatively.(2) Temperature dependent viscosity has large effects on flow and heat transfer characteristics and a reference temperature to estimate viscosity should be determined to obtain dimensionless correlation expressions for these characteristics.(3) The usual k- two-equation model of turbulence may be applied for flow in tube bank, however, it is very difficult to obtain the accrate results. the convergence and the heat balance become much poorer than laminar flow.(4) To improve the accracy of numerical solution and to obtain dimensionless expressions for pressure and heat transfer coefficients are remained to be solved in near future.