Numerical modeling of a 2 K J-T heat exchanger used in Fermilab Vertical Test Stand VTS-1

• Finite difference based 2 K J-T heat exchanger model has been developed.
• J-T heat exchanger performance characteristics have been studied in different modes of operation of VTS-1.
• Heat exchanger sizing plays the significant role in vapor flash reduction during maintaining the constant liquid level.
• Study quantifies the effect of liquid supply temperature and shell-side inlet temperature on percent vapor flash reduction.

Fermilab Vertical Test Stand-1 (VTS-1) has been in operation since 2007 for testing superconducting radio frequency (SCRF) cavities at 2 K. This test stand includes a heat exchanger consisting of a single layer; helically wound finned tube, upstream of the J-T valve. A finite difference thermal model has been developed in Engineering Equation Solver (EES) to study the thermal performance of this heat exchanger during refilling of the test stand. The model can predict heat exchanger performance under various other operating conditions and is therefore useful as a design tool for similar heat exchangers in other facilities. The present paper discusses the different operational modes of this heat exchanger and its thermal characteristics under these operational modes. Results of this model have been compared with experimental data gathered from the VTS-1 heat exchanger, and they are in good agreement with the present model.