Numerical Simulation For The Heat Transfer Of Solar Absorber Employing The Generalized Sources

With the shortage of fossil energy and the continuous strengthen of people's environmental awareness; the large-scale development and utilization of solar energy are getting more and more significant. The solar energy volumetric absorber as the high-efficiency and the high reliable heat exchanger offers a big probability for the large-scale use of solar energy.The Pin-fin array heat exchangers are the most potential solar thermal power plant heat exchangers, which consists of pin fin array. The internal complexity of the sturcture caused the complexity of flow, and the convective heat transfer couples with radiation in high-pressure and high-temperature is one of the most important characteristics.The focused sun light passes through the window into the exchanger, and the heat energy is evenly distributed by pin-fin array's reflection and radiation. Work fluid from entrance flows through the interior of exchanger, and brings energy out of the exchanger by convection. In this process, the cylindrical arrays existence increase the heat transfer area and also enhance the disturbance of fluid, but their objective existence have also increased flow resistance at the same time. The above characteristics can be described by adding source items in the related governing equations. This paper adopt continuum model to add energy source item in energy conservation equation and flow resistance source item in momentum conservation equation equivalently without taking into account of the flow details and cylindrical array's existence, so that we can research on heat transfer performance of the exchanger on macro. In this paper, multi-regions model is employed to deal with energy source item, the basic idea is that: according to the different height of the cylindrical array has different heat transfer coefficient, the flow zone is divided into several regions that are top region, free region, cylinder region and bottom wall region. The flow and convection characteristics of different regions are studied, and the heat transfer equations of different regions of the cylindrical array are obtained, so the energy source is obtained. The flow resistance source item is got by pressure drop coefficient. Based on above work, the numerical model is got. The expressions of the sources have been compiled in the UDF of the commercial software Fluent, then do numerical simulation.The simulation results have a good agreement with the experimental data. Therefore, the treatment of source items can reflect the dynamic properties of the real model and play a significant role on simplifying the real model.