Modeling a thermoplate conical heat exchanger in a point focus solar thermal collector

A three-dimensional ANSYS-FLUENT Computational Fluid Dynamics (CFD) model of the central receiver in a compact hybrid solar-thermal collector is presented. The small scale cavity receiver is conical in shape, laser welded from Inconel 625 with a 38 mm entrance aperture, and uses pressurized water as the Heat Transfer Fluid (HTF) within a thermoplate serpentine flowpath. The coupled thermofluidic CFD model examines a simplified unrolled version of this dimpleplate heat exchanger, representing the laminar flow within 10 × 1 mm expanded flowpath serpentine channels complete with intrachannel spot welds and non-uniform concentrated solar irradiance heating. The computational model is validated against experimental results with the receiver at the focus of a 2.7m² parabolic dish, two-axis tracking rooftop solar collector. For steady state conditions with the outlet HTF reaching temperatures in excess of 200 °C, the HTF temperature rise predicted by the computational model is in agreement with the experimental data. In order to accurately capture the heat losses from the heat exchanger to its surrounding, we present an additional three-dimensional CFD model including the heat exchanger and surrounding thermal insulation. Contours of temperature and velocity at the midplane of the dimpleplate receiver heat exchanger are presented.