Heat Transfer Characteristics Researchon Solar Air Porous Media

According to the urgent need of high efficiency, low cost of the solar thermal power generation, and combining the developing trend of energy use and thermal science research, the key basic problem of porous air heat absorber thermal science has been studied. Hot spots and damages often appear in the process of using the air receiver. The main reason is that solar energy is gathered to form high density, non-uniform flow of radiant energy, which makes the heat absorbing materials produce strong thermal stress and thermal shock. So the development of high absorption rate, high heat transfer efficiency, high reliability, low cost of air receiver have become a key part of the engineering technology. It is the ideal heat-absorbing material which has the characteristics of good heat transfer, high temperature resistant. So the porous ceramics which are used for as heat absorber are popular in current. We use air as the heat transfer fluid because it is easy to make and control.The heat flux distribution of the entrance to solar heat absorber is not uniformly. Fluid flow instability would cause the high temperature of local area which has major impacts on the Heat absorber performance. Porous heat absorber internal flow model and the gas/solid two phase heat transfer model were set up. Comsol Software simulation was used to study the internal heat and mass transfer characteristics of porous media heat receiver. And the factors influencing air temperature distribution in heat receiver have been analyzed. This research mainly includes the following two aspects:(1) the heat transfer characteristics of single-layer homogeneous porous medium in heat receiver research focus on analyzing medium pore density, porosity, entrance inlet velocity, and the boundary heat flux density of the temperature distribution of solid phase and gas phase two phase. The results reply that the density, porosity, the entrance inlet velocity, and the boundary heat flux density of porous media have a bigger influence on the temperature distribution of solid and gas phase which provide a reference to analyze the solar heat receiver thermal performance(2)Researches on heat transfer characteristics of new double-layer foam ceramic medium in solar heat transfer characteristics of solar porous media heat receiver. This paper adopts the similar method. Two layer porous media non-local heat balance equation and double-phase energy equation were established. The result replies that the size of the two layers of different porosity and pore density have the major impact on the overall temperature distribution and temperature distribution of import and export.The first layer thickness of porous media has a larger effect on simulation results of the entire model.