Development of an economical high temperature microchannel recuperator for solid oxide fuel cells

To improve the performance of solid oxide fuel cells, a secondary power cycle can be driven by the recuperation of exhaust gas heat. Microchannel recuperators are attractive for waste heat recuperation due to compact form factors which also minimize the mass of the expensive superalloys required. This paper introduces a new microchannel lamination architecture with the potential to further reduce the cost of high temperature microchannel recuperators. The design consists of a two fluid counterflow microchannel array containing alternating high and low pressure channels made from a high temperature nickel alloy. High pressure microchannels are hermetically sealed by laser welding. Low pressure microchannels contain microchannel flow inserts in the form of micro-scale pyramidal truss networks that prevent the channels from collapsing during operation. A clamshell housing is used to encapsulate the array and provide headering for the low pressure channels. To demonstrate the feasibility of the new microchannel lamination architecture, a sub-scale heat exchanger was designed and fabricated. Functional testing of the device shows a heat exchanger effectiveness of 52% with a pressure drop of 8.7 [kPa] through the low pressure side at a Reynolds number similar to that needed for the full-scale device. Based on our results, a full-scale design is proposed that uses 25% the raw material as the conventional design leading to an estimated cost reduction of over fourfold.