The effect of unit size on the flow and heat transfer performance of the "Schwartz-D" heat exchanger

As a representative type of triple periodic minimal surface (TPMS) topology, the S-D structure exhibits distinctive heat transfer properties and is ideal for constructing high-performance heat exchangers (HXs). To explore the effect of unit size on the flow and heat transfer performance, three crossflow S-D HXs with different unit sizes and the same porosity are designed and produced by metal additive manufacturing in this study. Simulation results show that the reduction in unit size induces a larger scale of bifurcation flow and increases the frequency of flow area change in HX. Experimental results demonstrate that when the smallest unit size is adopted, the HX's effectiveness can be improved by at least 10%, but at the cost of a 42% increase in pressure drop. Meanwhile, the advantage of small unit size in heat transfer enhance-ment will be further expanded under large flow rate conditions. In addition, it is found that the effect of flow ratio on the heat transfer performance of the S-D HXs appears to be linear, and the unit-based Reynold number may be an appropriate dimensionless parameter for correlating their pressure drop and heat transfer data. All in all, this study is expected to provide a better understanding and guidance for the design and optimization of TPMS HXs.& COPY; 2023 Elsevier Ltd. All rights reserved.