Ceramic heat pipes for high-temperature heat recovery

Abstract

This paper summarizes the results of a conceptual design study for ceramic heat pipe recuperators conducted by the AiResearch Manufacturing Company, a division of the Garrett Corporation, for the University of California Los Alamos Scientific Laboratory. The function of the recuperator is to preheat combustion air with industrial furnace exhaust gases, thus effecting a substantial fuel saving as compared with unrecuperated, non-preheated furnaces. The proposed recuperator system consists of two heat exchanger units: a high-temperature ceramic heat pipe recuperator using sodium as the working fluid and a low-temperature metallic plate-fin recuperator. Systems were designed for three furnace applications. The ceramic unit consists of a bundle of individual heat pipes acting in concert, with a partition separating the air and exhaust gas flow streams. The overall flow configuration is counterflow. The metallic unit is of a crossflow configuration, and is similar to AiResearch designs used for other applications. Potential fuel savings are in the 40–50% range. Calculated simple payback periods, based on potential fuel cost savings and estimated system costs, are less than six months for all designs, exclusive of specific retrofitting and high-temperature burner costs.