Compactness factors for rolled, stacked-screen regenerative heat exchangers

The objective for the current research was to determine how the heat transf er and pressure drop characteristics changed in a stacked, wire-screen rege nerative heat exchanger (regenerator), if the screens which were used to co nstruct the matrix were rolled to decrease their thickness. More of the rol led screens would fit into a regenerator with a reduction in gas volume in the regenerator. During the course of the research, an improved method for determining the heat transfer characteristics of a porous medium regenerato r was developed. The results show that the compactness factor (j(H)/f) was adversely affected by rolling. Flattening the screens by 15%, 30%, or 50%, did not improve the heat transfer rate to the matrix, but it did increase t he total pressure drop. Rolling the screens caused a decrease in both wette d surface area and pore size. The heat transfer which is proportioned to th e wetted surface area was reduced. The pressure drop, which is strongly dep endent on pore size, increased. Rolling the screens also reduced the effect iveness of the regenerator. (C) 1998 Elsevier Science Ltd. All rights reser ved.