Comparison of performance of heat regenerators: Relation between heat transfer efficiency and pressure drop

Heat regenerators transfer heat from one gas to another, with an intermedia te storage in solids. The heat transfer surface for gas flow application sh ould provide at the same time high surface area and low friction factor. Th ree geometries of heat transfer surface, monolith, stack of woven screens a nd bed of spheres, have been compared. Their performance was evaluated from the pressure drop of the heat regenerator working at a given heat transfer efficiency. The comparison was performed using numerical simulation and pu blished measurements of heat transfer and flow friction characteristics. By adjusting the length and the period of the exchanger, it is possible to ob tain the same heat transfer efficiency with the three geometries. Beds of s pheres give very short and compact heat regenerators, working, at high pres sure drop. At the opposite, monoliths form long regenerators working at low pressure drop. Stacks of woven screens cover a wide range of performance: low porosity woven screen give high heat transfer efficiency and high press ure drop, while high porosity woven screens offer performance similar to th at of the monoliths. Copyright (C) 2001 John Wiley & Sons, Ltd.