Investigation of the Characteristics of Regenerative Heat Exchangers

The objective of the current research was to investigate the effects of reducing screen thickness on the volume and compactness factor of stacked, wire-screen regenerators. An improved transient step-change method was devised which integrated experimental data with a numerical model of the flow to determine the heat transfer coefficient and friction factor. The improvements to the approach are: (1) the measured inlet temperature trace is used, (2) the heat transfer coefficient is based on a parameter called the sponge effect delay time, and (3) the important effect of the tube surrounding the matrix is included in the numerical model. The data show that the heat transfer is the same for reduced thickness screens as it is for unrolled screens once the decrease in surface area caused by rolling the screens is taken into account. However, the friction factor increases, particularly for a 50% reduction in screen thickness. Consequently, the ratio of Colburn factor to friction factor, the compactness factor, decreases as the thickness of the screens decrease. The effectiveness of the regenerators is also adversely affected by the rolling.Air Force Inst of Tech Wright-Patterson AFB OH is the author of 'Investigation of the Characteristics of Regenerative Heat Exchangers', published 1996 under ISBN 9781423577959 and ISBN 1423577957.