Chemically Etched Cryogenic Micro Structure Heat Exchanger

A tandem 4 K pulse tube refrigerator requires a recuperator to be fully accomplished. The recuperator should be a counter-flow heat exchanger which has micro heat-transfer structure like a regenerator of cryogenic refrigerators. However, the technology of such a heat exchanger is not well established yet. Hence, the development of a counter-flow compact heat exchanger with micro structure is demanded first in order to proceed to the recuperative 4 K pulse tube refrigerator. This paper describes the design, fabrication and preliminary performance test of such a heat exchanger. The stainless steel micro structure with approximately 0.1 mm characteristic length has been created by chemical etching. The parallel V-shape double-sided micro channels (chevron stucture) in the heat exchanger enable the flow to be three-dimensionally well mixed so that the heat transfer at low Reynolds number can be enhanced. The etched plates are stacked and bonded through a vacuum brazing process to compose a plate-type heat exchanger. The chemically etched micro-structure heat exchanger has thermal effectiveness of 97%.