This article first reviews non-traditional heat exchanger geometry, laser welding, practical issues with microchannel heat exchangers, and high effectiveness heat exchangers. Existing microchannel heat exchangers have low material costs, but high manufacturing costs. This article presents a new expanded microchannel heat exchanger design and accompanying continuous manufacturing technique for potential low-cost production. Polymer heat exchangers have the potential for high effectiveness. This article discusses one possible joining method – a new type of laser welding named ‘forward conduction welding’, used to fabricate the prototype. The expanded heat exchanger has the potential to have counter-flow, cross-flow, or parallel-flow configurations, be used for all types of fluids, and be made of polymers, metals, or polymer–ceramic precursors. The cost and ineffectiveness reduction may be an order of magnitude or more, saving a large fraction of primary energy. The measured effectiveness of the prototype with 28 µm thick black low-density polyethylene walls and counterflow, water-to-water heat transfer in 2 mm channels was 72 per cent, but multiple low-cost stages could realize the potential of higher effectiveness.
Denkenberger, D. C., Brandemuehl, M. J., Pearce, Joshua M., & Zhai, J. (2012). Expanded microchannel heat exchanger: Design, fabrication, and preliminary experimental test. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 226(4), 532-544. http://digitalcommons.mtu.edu/materials_fp/33/