Thermal hydraulic characteristics of cryogenic offset-strip fin heat exchangers

•Comprehensive studies were conducted on OSFs with cryogenic gaseous helium.•Variation tendencies of j and f factors at cryogenic conditions were revealed.•Fin structures exerted different levels of impact on PFHX’s compactness.•Some suggestions about selection strategy of fin structures were proposed. Plate-fin heat exchangers are essential in large-sized helium liquefiers/refrigerators. However, studies on the general fin performance data and applicable fin selection strategies at low temperatures have rarely been conducted. In this paper, the thermal-hydraulic characteristics of cryogenic helium flowing through offset-strip fins were investigated by experiments and simulations. Through the comparative means, the variation tendencies of fin surface performance at different temperature conditions were also revealed. The results showed, for j factors, the heat transfer performance deteriorated gradually with the decrease of temperature. For f factors, the values increased slightly at low temperatures, and they intended to increase more dramatically at smaller Re numbers. Additionally, sensitivity analysis revealed that, for the optimal object of volume quality, the selection of Re number, fin space and thickness deserved more attention, so that the designed heat exchanger could achieve sufficient heat transfer in compact space.