Effect of aperture size on free convection and radiation heat transfer in isoflux upward-facing cylindrical cavities

Taking isoflux upward-facing cylindrical cavities as object, the effect of aperture size on free convection and radiation heat transfer was studied experimentally and numerically. The influences of tilt angle and heat flux under different aperture sizes were also tested. The reliability of experiment was confirmed by experimental uncertainty analysis and reproducibility. The results indicate that the larger the aperture size is, the lower the temperature of cavity surfaces is and the stronger the free convection and radiation heat transfer are. The effect of aperture size on free convection heat transfer is of more significance for the cavities with small aperture size, while the behavior is opposite to its effect on radiation heat transfer. Aperture size has no influence on the variation trends of free convection and radiation heat transfer Nusselt numbers (Nuc and Nur) with tilt angle and heat flux. To facilitate engineering applications, some suggestions and empirical correlations with high prediction accuracy were proposed.