Experimental and numerical investigation of convection heat transfer in transpiration cooling

The turbulent flow and heat transfer in a rectangular channel without and with transpiration cooling was investigated experimentally and numerically. The two-layer k–ε model was used to calculate the turbulent velocity and thermal characteristics of the main flow. The numerical results corresponded well with the experimental data including the surface temperature and heat transfer coefficients for the channel with and without transpiration cooling. The numerical results showed that the transpiration cooling greatly increases the boundary layer thickness and reduces the wall skin friction. The tests and calculations showed that increasing coolant blowing ratio sharply reduced both the wall temperature and the convection heat transfer coefficient. For a blowing ratio of 1%, the convection heat transfer coefficient was reduced by about 50%. The numerical and experimental results also agreed well with known correlations for constant thermophysical properties. The influence of variable properties on the convection heat transfer in transpiration cooling at high gas temperatures was also investigated.