Impact of velocities and geometry on flow components and heat transfer in plate heat exchangers

Abstract

• Influence of velocity on flow is investigated experimentally and numerically. • The flow is mainly determined by substreams velocity and angle β . • Higher velocities promote furrow component and at fixed Re entail lower f and Nu. • Redefined Re , Nu and f shall reflect substreams flow path and velocity. • Numerical results are best validated in terms of heat flux and pressure drop. This study aims at better understanding of the complex flow phenomena in plate heat exchangers. This is identified in the literature to be crucial for improvement of numerical models and generalized heat transfer and pressure drop correlations with respect to their applicability in heat exchanger optimization. 3D numerical simulations of the flow in corrugated channels of plate heat exchangers with different corrugation angles ( β 28° and 65°) were performed in order to investigate in detail complex flow patterns and their influence on the heat transfer and pressure drop at laminar, transient and turbulent flow conditions. The study is supported by the visualization and thermal–hydraulic tests ( Re = 0.1–6037) carried out on the channels with corresponding chevron angles, using fluids of different viscosity to explore effects of different velocities at fixed Re numbers. Consequent alternation of flow patterns is believed to cause recorded differences in heat transfer and pressure drop data. Results from the simulations are analysed in different sections of the channels in light of the flow substreams, velocity distribution, wall shear stress and wall heat flux distribution. They confirm assumptions from the present visualization tests on the longitudinal and furrow substreams interactions and characteristics, as well as on the thermally and hydrodynamically developing flow conditions within a basic cell. A suitability of comparing simulations and experimental data in terms of Fanning friction factor and Nusselt number is discussed relative to the definitions of characteristic length, hydraulic diameter and mean velocity at different flow patterns. The computed heat transfer and pressure drop is in a relatively good agreement with the performed tests and literature data. The presented numerical-experimental analysis outlines importance of the substreams velocity on their interactions and flow components size, which in turn determines PHE channel heat transfer and pressure drop characteristics. The present findings may serve for improvement of CFD modelling, generalized correlations and definition of Re , Nu and f to allow for comparison of heat transfer and pressure drop data at different geometries and flow conditions.