Improving channel layouts in printed circuit heat exchangers for efficient supercritical carbon dioxide cooling

Abstract

An analysis is conducted to investigate the impact of channel layouts in a Printed Circuit Heat Exchanger (PCHE) on the cooling process of supercritical carbon dioxide (CO₂) using water (H₂O). Sixteen different models are evaluated under two cooling conditions: one far from the pseudo-critical point and the other near it. To assess the performance of the PCHE, a conjugate heat transfer model is solved using the finite volume method. The variations in the thermo-physical properties of supercritical CO₂ are obtained from the NIST REFPROP database. The findings reveal that reducing the channel diameter has a more significant impact on the thermal performance of the cold-side than the hot-side. Under cooling conditions far from the pseudo-critical point, this reduction increases the heat transfer coefficient by 43.5 % on the cold-side and by 8.4 % on the hot-side. However, this effect on the hot side becomes increasingly pronounced as CO₂ approaches the pseudo-critical point. Under the specified cooling conditions, flipping only the hot-side plate enhances CO₂ cooling efficiency by improving synergy and mitigating heat transfer deterioration. Notably, this modification results in a 7.12 % improvement in the overall performance of the PCHE. This configuration is particularly effective when cooling conditions are near the pseudo-critical point and when the channel diameter is reduced. The optimal channel layout is influenced by the channel diameter. For heat transfer plates with large and equally sized channel diameters, flipping only the hot-side plate achieves the highest overall performance, with an improvement of approximately 6.87 %. In contrast, for heat transfer plates with small and equally sized channel diameters, simultaneously flipping both the hot-side and cold-side plates yields superior performance, with an improvement of approximately 7.11 %. Furthermore, when dealing with heat transfer plates of different channel diameters, it is recommended to flip only the hot-side plate.