Parametric Thermo-Hydraulic Benchmarking of Capsule and Dimple Plate Heat Exchanger Channels via Periodic Unit-Cell CFD

Direct comparisons between capsule- and dimple-embossed plate heat exchanger channels are limited by differences in operating conditions and metric definitions across published studies. This study addresses that comparison gap through a side-by-side assessment under a common steady-state, single-phase water-flow Reynolds-averaged Navier–Stokes framework, unit-cell approach, thermal boundary conditions and reporting definitions at Re = 4282. Four seven-case sweeps vary capsule angle, capsule height, dimple height and dimple flow-entry angle; one additional case combines the largest tested dimple height and angle. The unit cells use lateral periodic boundaries and a streamwise quasi-periodic iteration loop for velocity and turbulence profiles, while inlet temperature remains prescribed. The performance evaluation criterion (PEC) combines the two-wall Nusselt number with the Fanning friction factor to quantify the heat-transfer–flow-resistance trade-off. The heat-transfer coefficient uses both walls’ total heat rate and area, referenced to each case’s fluid-domain mass-average static temperature. Relative embossing depth (RED) is height divided by the case-specific hydraulic diameter. Constructed PEC ranges are 254.6–273.0 for capsule angle, 254.8–294.6 for capsule height, 234.0–285.2 for dimple angle and 214.8–251.0 for dimple height. The combined dimple case gives PEC = 305.14, compared with 294.64 for the 5 mm capsule case. Their 3.56% separation is not an uncertainty-resolved performance advantage. These are comparative outcomes within the tested parameter ranges and unit-cell heating conditions.