Enhanced Gas-Side Heat Transfer in Rectangular Micro-Honeycombs

Abstract

Gas and air-side heat transfer is ubiquitous throughout many technological sectors, including HVAC (heating, ventilating, and air conditioning) systems, thermo-electric power generators and coolers, renewable energy, electronics and vehicle cooling, and forced-draft cooling in the petrochemical and power industries. The poor thermal conductivity and low heat capacity of air causes air-side heat transfer to typically dominate heat transfer resistance even with the use of extended area structures. In this paper, we report design, analysis, cost modeling, fabrication, and performance characterization of micro-honeycombs for gas-side heat transfer augmentation in thermoelectric (TE) cooling and power systems. Semi-empirical model aided by experimental validation was undertaken to characterize fluid flow and heat transfer parameters. We explored a variety of polygonal shapes to optimize the duct shape for air-side heat transfer enhancement. Predictions using rectangular micro-honeycomb heat exchangers, among other polygonal shapes, suggest that these classes of geometries are able to provide augmented heat transfer performance in high-temperature energy recovery streams and low-temperature cooling streams. Based on insight gained from theoretical models, rectangular micro-honeycomb heat exchangers that can deliver high performance were fabricated and tested. High- and low-cost manufacturing prototype designs with different thermal performance expectations were fabricated to explore the cost-performance design domain. Simple metrics were developed to correlate heat transfer performance with heat exchanger cost and weight and define optimum design points. The merits of the proposed air-side heat transfer augmentation approach are also discussed within the context of relevant thermoelectric power and cooling systems.