Complex 3D-flow analysis and corrugation angle effect in plate heat exchangers

Abstract

This article presents a detailed analysis of the thermo-hydraulic transfers for single-phase flow in brazed plate heat exchangers (BPHE) using numerical simulations. The comparison of the simulation and experimental results show similar trends on the variations of the global thermo-hydraulic quantities, as the friction and convective heat transfer coefficients, with respect to Reynolds number. Whether for simulations or experiments, there is a significant change in the hydraulic behavior for Re ≈ 200, which may suppose a change of the flow structure into the BPHE. The influence of the chevron angle (β) on the flow structure and on the pressure drops for Reynolds numbers ranging from 1 to 2500 has been conducted on a representative flow fields. Based on the analogy that complex 3D-flow may be regarded as two 1D-flows of sinusoidal cross-section in flow interaction, it was defined a flow characteristic observable, which quantifies the mass transfer rate from one groove to the other. The analysis shows that flow structures are not only sensitive to chevron angle but also to the mass flow rate. It is pointed out that the variation of the friction coefficient versus the Reynolds number is correlated to the flow structure classes, of type “helical” and “cross-flows”. Based on these results and for the full range of Reynolds number, the study reveals two categories of PHE hydraulic behavior depending on the chevron angle with a limit around 60° for the change of the PHE behavior.