Numerical investigation on fin configuration improvement of 2 K sub-atmospheric plate-fin heat exchangers for the superfluid helium cryogenic systems

In order to improve the flow and heat transfer performance of 2 K sub-atmospheric pressure plate-fin heat exchanger, a new type of corrugated-serrated fin is proposed by combining corrugated and serrated fin. The Lw number is defined as a new structural parameter to describe the new type of fin. The numerical model of flow and heat transfer in the fin channels takes into account the influence of low temperature conditions with variable physical properties and has been fully verified by experimental data. Numerical investigation is performed to study the thermohydraulic characteristics of serrated fin, corrugated fin and corrugated-serrated fin. Meanwhile, three performance evaluation criteria Colburn factor j, friction factor f and TE-factor are used to qualitative compare their flow, heat transfer and overall thermo-hydraulic performance. The results reveal that the heat transfer performance of new corrugated-serrated fins is the best. Colburn factor j of the new fins increases by 19.97%~38.22% compared with corrugated fin, and increases by 25.09%~33.83% compared with serrated fin. The flow performance of the corrugated-serrated fin is slightly worse, but the overall thermo-hydraulic performance is better, especially at low Reynold number. Besides, the effects of various structural parameters on the thermohydraulic characteristics of the corrugated-serrated is obtained. The conclusions provide theoretical guidance on the design of 2 K sub-atmospheric plate-fin heat exchanger.