Title: Maximum possible efficiency for energy recovery from low-grade heat sources

Authors: Martin Gellender

Addresses: Department of Environment and Resource Management, GPO Box 2454, Brisbane, Queensland 4001, Australia

Abstract: Gas-to-gas heat exchangers are increasingly being used to recover low-grade heat (or cooling) to reduce energy requirements for space heating, drying and other applications. The efficiency of heat recovery is often limited by practical considerations which could – in principle – be reduced or eliminated by development of new materials and technology. However, this paper posits a fundamental limitation on the efficiency of heat recovery that may be achieved, determined by the temperature difference between the inlet streams, the rate of heat transfer per unit volume and properties of the particular gases (or other fluids) between which heat is transferred.

Keywords: heat recovery efficiency; heat exchangers; heat transfer; thermodynamics; exergy; laminar flow; counter-current; low-grade heat; temperature difference; inlet streams.

DOI: 10.1504/IJEX.2011.042070

International Journal of Exergy, 2011 Vol.9 No.2, pp.235 - 253

Published online: 23 Aug 2011 *

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