Multi-objective optimization of the structure of triangular chevron channels

Chevron channels are one of the popular techniques that are extensively used in different heat exchangers such as plate heat exchangers and solar air heaters to improve heat transfer potential. Numerical studies were carried out on turbulent heat transfer and friction factor loss through a triangular chevron channel for a uniform wall heat flux 3000 (W/m2) using air as a working fluid. The results of the average Nusselt number, friction factor and thermal enhancement factor (TEF) in different phase shifts (ϕ) are presented. Reynolds number were varied from 10000 to 30000 and horizontal moving of the plates were horizontally moved with regards to each other (phase shift) at the range of 0° ≤ϕ≤180° whereas, distance between chevron surfaces was constant (D=5 mm). The channels with phase shift angle of ϕ = 18.28º, are the most attractive from the viewpoint of energy saving. The Genetic Algorithm optimization using NSGA II algorithm showed that with increasing Reynolds number, Nusselt number (Nu) increased and the Thermal Enhancement Factor (TEF) decreased. It also proved that ϕ=18.28º was the optimum phase shift. The results also indicated that the triangular chevron channels with special geometry (Dv=7.43mm) have maximum Nu and TEF and the minimum friction factor.