The effect of air film thermal resistance on the behaviour of dynamic insulation

The authorsʹ previous analysis of dynamic insulation is extended to include the inner and outer air film resistances with the objective of modelling the variation in surface temperature with airflow. The boundary condition that comes closest to predicting the variation of the surface temperature with air flow is one which assumes that the conduction heat flux at the wall surface, rather than the net heat flux, is equal to the flux incident on the wall from global environmental temperature, Tei. Comparison of predictions of the temperature drop across the inner and outer air films with data from a hot box experiment shows that the theory correctly predicts the variation in surface temperature with air flow through a porous wall.