Heat exchanger design hots up

Abstract:

<p>This document is a report for the project titled 'Heat exchanger design hots up'.</p> <p>This project was a 12-month Development LINK project that built on the findings from a previous project (AFM126) on innovations in heat recovery systems for tubular heat exchangers. In the previous project, laminar flow and heat transfer in the shell were of interest, whereas in this project, shell and tube flow with heat transfer under both laminar and turbulent conditions were considered. Commercial considerations dictated that any modifications to heat exchanger equipment required to promote heat transfer in heat recovery mode should also, ideally, result in enhanced performance in the conventional mode of operation.</p> <p>This project, and its predecessor, concentrated on one particular type of shell and tube heat exchanger, namely a multi-tube heat exchanger with 7 tubes of external diameter 16mm and a shell of internal diameter 70mm (a Tetra Spiraflo MT 70/7x16C-6, as shown in Fig. 1). A number of design changes, aimed at improving the performance of the heat exchanger, were considered. Attention was first focussed on changes that improved the uniformity of flow distribution within the tubes of a tube bundle and in the shell around the tube bundle. Of primary interest were wall corrugation pattern, tube wall thickness, centre tube diameter and shell-side baffles.</p> <p>By using CFD to experiment numerically with novel exchanger designs, it was possible to highlight the most promising features and thus reduce the quantity of real experimental testing. Computational work, carried out at the University of Plymouth, used the CFX code. The well-known k-&epsilon; turbulence model was used, as well as a 'shear-stress-transport' (SST) model incorporating more realistic flow physics near the tube and shell walls. </p> <p>Commercial exploitation will initially be achieved with the ongoing improvement programme for Tetra Spiraflo tubes. Availability of CFD models for flow behaviour prediction will enable new exchanger designs to be evaluated prior to building prototypes. For example, changes in heat transfer performance were demonstrated computationally as a result of altering the depth of tube corrugations. However, it was questionable whether current manufacturing tolerances could allow these to be consistently reproduced in practice, which is an area that will be addressed in the future.</p> This report contains additional illustrations and cross-section figures.

Author(s):

Tucker, G.