Problems of Shell-side Performance of Longitudinal Flow Shell and Tube Heat Exchanger with Decrease of L/D and Its Solutions

摘要

This paper presents numerical simulation of fluid flow and heat transfer in shell-side of large-scale shell-andtube heat exchanger with longitudinal flow by porous-medium and distributed resistance model. Such characteristics as flow field distribution, shell-side pressure drop, heat transfer performance, and overall performance factor of shell-side were studied with the change of L/D and Re. It showed that when L/D from 6.0 decreased to 1.5 with the same Re, fluid flow mal-distribution became seriously, pressure drop increased sharply, overall performance factor η decreased sharply. Especially, under the condition of L/D≤2.0, the problems became more and more seriously. By deeply analysis of the pressure field distribution, it discovered that more than 80% of total pressure drop occurred in the region of inlet and outlet, in where fluid flow mainly cross tube bundle. In order to solve the problems, an idea as a novel structure of multiparallel- channel inlet and outlet (MPC) in shell-side were proposed. Comprehensive investigation showed that MPC was very effectively not only in optimizing the fluid flow distribution of shell-side and enhancing globe heat transfer performance of heat exchanger, but also in decreasing shell-side pressure drop.