Numerical Study On The Heat Transfer Performance Of Porous Volumetric Solar Receiver

Disc solar thermal power generation system has a broad application prospect.The volumetric solar receiver is the core heat transfer unit of the disk solar thermal power generation system.However,the low thermal conductivity of air leads to the low heat transfer efficiency of the cavity volumetric solar receiver whose heat transfer fluid is air.Porous media has the advantages of high temperature resistance,large specific surface area and good heat transfer performance.Therefore,the heat transfer performance of the receiver can be improved by filling the interior of the receiver with porous media.In this paper,the heat transfer characteristics of volumetric solar receiver s with different structures under non-uniform heat flow boundary conditions are studied,and the effects of gradient parameters on the heat transfer performance of volumetric solar receivers with different structures are analyzed.The main research contents include:（1）The numerical simulation of convection and heat transfer in a volumetric solar receiver in porous media with non-uniform heat flow boundary is realized.Based on the Gaussian distribution model,the boundary conditions of the actual non-uniform heat flow of solar energy are defined,and a local non-heat equilibrium model is established.The reliability of the physical model and numerical calculation of the heat absorber is verified by the experimental data.（2）The influence of different structures on the heat transfer performance of the volumetric solar receiver with porous media is studied.The effects of porosity,pore size and turbulence parameters on the heat transfer performance of the volumetric solar receiver are analyzed.The results show that the drum type heat transfer performance is better than other structures,and the average outlet temperature of the drum type heat exchanger（RT-III）is 48.27K（+6.8%）higher than that of the cylindrical type heat receiver with the pore size d_p of 3mm.（3）The optimum combination of gradual pore size and gradual porosity in drum type heat sink is determined.The effects of parameter matching between constant pore size and gradual pore size,constant porosity and gradual pore size on the heat transfer performance of drum type receiver are compared and analyzed,and the permutation combination method was used to study the effects of different porosity and different pore size on the heat transfer performance of drum type volumetric solar receiver.The results show that the heat transfer performance of drum type receiver with gradient parameters is obviously better than that with constant parameters,and the average outlet temperature of heat transfer fluid with gradient porosityφ₃ and d_p3increases by 100.73K（+11.47%）compared with constant porosityφ₁ and constant pore size d_p1.Two new types of gradient porosityφ₄ andφ₅ are optimized by using gradient porosityφ₃ as the benchmark.Compared withφ₃,the average temperature of heat transfer outlet increases by 14.41K（+1.62%）under the condition of constant pore size d_p of 2mm.The research results can provide reference for the design and optimization of the heat transfer performance of the volumetric solar receiver with porous media.