Cross-flow heat exchangers for anti-freezing of liquid nitrogen

• We propose a cross-flow heat exchanger for subcooling liquid nitrogen.
• The possibility of freeze-out is a crucial design issue for long HTS cables.
• A two-pass cross-flow heat exchanger is fabricated and experimentally tested.
• The cross-flow is effective in reducing the freeze-out risk of liquid nitrogen.

Cross-flow heat exchangers are proposed and experimentally investigated as an anti-freezing scheme of liquid nitrogen. The possibility of freeze-out of liquid nitrogen is an important design issue in developing long superconducting cables, as the supply temperature of liquid nitrogen is close to its freezing temperature (63.3 K). Plate-fin heat exchangers are fabricated as typical counter-flow and newly proposed two-pass cross-flow in laboratory scale, and tested with cold helium gas at temperatures below 60 K. The experimental results show that the cross-flow heat exchanger is less vulnerable to the freeze-out condition, since the temperature distribution is basically two-dimensional. The cross-flow heat exchangers are effective in avoiding a complete clog-up of all passages and reducing the risk of freeze-out of liquid nitrogen.