Influence of Rim Angles and Heat flux Distribution Boundary on the Heat Transfer of an Absorber Tube for a Parabolic Trough Solar Collector

Abstract

One of the most important solar concentrator among other concentrating collectors is the parabolic trough solar collector because of its successful application in solar electricity generation. This study investigated the influence of collector rim angles and non-uniform heat flux distribution boundaries on the inner heat transfer coefficients of an absorber tube for a parabolic trough solar collector. Laminar flow steady-state condition was considered where buoyancy effects were significant. Numerical simulation was conducted in ANSYS Fluent version 14.5. Sinusoidal non-uniform heat flux distributions boundary conditions were implemented via a user defined function in Fluent. It was established that the absorber tube-wall temperature rise with a rise in the collector rim angle and the circumferential span of non-uniform heat flux allocations limit. It was furthermore revealed that when buoyancy-driven secondary flow is present, the internal heat transfer coefficient increased more than twice advanced than the pure forced-convection case (i.e. no buoyancy effects), and representing heat transfer improvement due to secondary flow effects. Also, when buoyancy effects are present, the mean internal heat transfer coefficient improved as the heat flux intensity is increased, the collector rim direction and the circumferential span of the non-uniform heat flux distributions boundary. This study further discovered that the mean internal heat transfer coefficient became higher with a rise in the temperature of the absorber tube inlet flowing fluid.