Preliminary Design Optimization of 2 K Superfluid Helium Plate-fin Heat Exchanger in Kilowatt Scale

Abstract

The 2 K cryogenic system is a key subsystem of the new generation superconducting accelerator, and the 2 K heat exchanger is the key equipment. With the increasing scale of 2 K cryogenic system, the demand for high-flow 2 K heat exchanger becomes more and more urgent, and the current application of the tube and fin type, coil and tube structure of the heat exchanger is gradually replaced by a more efficient and compact platefin heat exchanger in high flow conditions, but the platefin heat exchanger has more structural parameters, and it is difficult to take into account the heat transfer efficiency, pressure drop and volume size in the design process. In this paper, based on the basic differential equations of heat transfer and pressure drop and the related flow heat transfer correlation equation, the design calculation of a 50 g/s flow rate 2 K heat exchanger supporting a 1 000 W@2 K cryogenic system was carried out using the distributed parameter method. Five parameters affecting the performance of the heat exchanger were analyzed and the comprehensive optimization index of the heat exchanger was proposed using the weighting coefficient method. Based on the proposed optimization indexes, a genetic algorithm was used to optimize the heat exchanger with multiple foci on high heat transfer efficiency, low pressure drop and small size according to the engineering needs, and a series of optimization solutions were obtained, from which the solution focusing on heat transfer efficiency was selected as the preliminary design result. Based on the parameter of this result, a threedimensional model of the heat exchanger heat transfer channel was established, and CFD numerical simulation was used for simulation calculation. The simulation results were in good agreement with the design results, verifying the accuracy of the preliminary design results, and the performance of the heat exchanger under different operating conditions was analyzed for this optimization result. The optimization result shows that the heat exchanger is selected with perforated plate type fins to cold-hot-cold (CHC) structure for the arrangement, it has 10 layers of CHC structure, its length is 760 mm, fin height is 4 mm, fin spacing is 7.9 mm, heat transfer efficiency of the heat exchanger is 84.4%, pressure drop is 222.16 Pa, and the volume is 0.022 1 m3. A variety of fin types of heat exchangers will be studied in the future to meet the demand of heat exchanger use.

Keywords

• cryogenic system
• plate-fin heat exchanger
• distributed parameter method
• genetic algorithm
• numerical simulation