Revista de ciencias e ingeniería de materiales

Mixed Convection Heat Transfer in an Absorber Tube with Non-uniform Heat Flux Distributions Boundary for a Linear Fresnel Solar Thermal Collector: Review Work

Abstract

Izuchukwu F. Okafor* and Bappah Adam Umar

This work reviewed the mixed convective heat transfer in absorber tubes similar to that of a linear Fresnel solar collector. Studies on the experimental and numerical simulations on linear Fresnel solar thermal collectors were reviewed to establish the gaps in the literature for further studies that could improve the overall performance of a linear Fresnel solar collector. The solar heat flux impinges on the absorber tubes of a linear Fresnel solar collector, from underneath independent of the position of the sun. This resulted in a circumferential non-uniform heat flux distributions around the tube wall, contrary to previous studies which assumed uniform heat flux boundaries for convenience. A number of studies had investigated mixed convection heat transfer in horizontal circular tubes for uniform heat flux distribution boundary symmetrical to the direction of the gravitational field. Studies are lacking for linear Fresnel solar collectors due to non-uniform circumferential heating of the absorber tubes from underneath for weak turbulent or laminar flow conditions. Studies are also lacking in the literature for the case of asymmetrical non-uniform heat flux distributions boundary on the absorber tube when the incident solar radiation deviated from the zenith angle position due to the sun tracking system of the collector. The degree of asymmetry of the heat flux distribution boundary could have significant influence on the internal heat transfers characteristics of the absorber tubes.