Experimental investigation on the thermal-hydraulic performance of serrated fins and novel serrated-perforated fins for PFHEs in cryogenic helium systems

Plate-fin heat exchangers (PFHEs) are crucial components in cryogenic helium systems (CHS), significantly affecting the overall system efficiency. The thermal-hydraulic performance of fins plays a critical role in the heat transfer efficiency and compactness of PFHEs. However, there is a notable lack of experimental research on the thermal-hydraulic characteristics of the fins under cryogenic helium conditions, particularly at the near liquid helium (LHe) temperature range (4.5 K). Inaccurate fin performance parameters can lead to deviations in heat transfer area and pressure drop calculations of PFHEs, adversely affecting the design and optimization of CHS. To address this, the thermal-hydraulic performance of serrated fins (SFs) and novel serrated-perforated fins (SPFs) are investigated experimentally at liquid nitrogen (77 K) and liquid helium (4.5 K) temperature ranges. The results are compared quantitatively with predicted values of empirical correlations derived from the steam-air test methods at room temperature, revealing variation in heat transfer and flow performance at cryogenic conditions. The experimental data show that the j factor of SFs at LHe and LN2 temperatures falls below predicted values, with root mean square errors (RMSE) ranging from 8.13 % to 60.84 % and 6.37 %–50.99 %, respectively. The f factor at LN2 temperature also shows a significant deviation from predicted values of empirical correlations, with RMSE ranging from 10.93 % to 38.34 %. These results indicate that most empirical correlations based on room temperature steam-air test methods have limited applicability to cryogenic helium conditions. For the novel SPFs, the perforated structure enhances heat transfer performance but compromises flow performance. The experimental results demonstrate that the thermal-hydraulic performance of SPFs is significantly superior to that of SFs under cryogenic conditions. This study provides significant theoretical and experimental foundations for the efficient design and optimization of PFHEs in CHS.