A comparative study on the convection heat loss characteristics of solar cavity receiver based on the Boussinesq approximation and the ideal gas law

摘要

A comparative study on the convection heat loss characteristics of a cavity receiver with the wall and environment temperature difference ranging in 10K ≤ ΔT ≤ 300K has been done,considering the air properties with the Boussinesq approximation and the ideal gas law-based temperature-dependent properties respectively.The temperature and velocity contours,the variations of convection heat loss of the receiver Qcv and the deviation percentages versus temperature difference ΔT have been presented.Results show that,the thickness of air thermal boundary layer on the cavity wall decreases with the increase of ΔT,while the inflow velocity of cold air and the outflow velocity of hot air increases,which makes the convection heat loss of receiver Qcv increases.However,using the two methods,the differences of temperature and velocity distributions inside receiver become more noticeable as ΔT increases,especially for the receivers with smaller aperture ratio AR and larger cavity aspect ratio L/D.Hence,either the Boussinesq approximation or the ideal gas law-based temperature-dependent properties is appropriate when ΔT ≤ 80K,because the deviation percentage of Qcv is less than 10％; however,when the temperature difference is relatively large,such as 200K ≤ ΔT ≤ 300K,the deviation percentage is so large that the ideal gas law-based temperature-dependent properties is more appropriate.