Theory of a calorimeter at a permeable surface

Abstract

The calorimetric method for determining the heat flux at a permeable (or sublimating) surface requires the solution of several specific heat-transfer problems, since the calorimeter, bringing about discontinuities in the boundary conditions at the wall (the cessation of blowing, a jump in the temperature of the wall and of its catalytic properties, etc.), introduces perturbations into the boundary layer and measures a heat flux differing from the flux in the absence of a calorimeter. Within the framework of the boundary layer, schematization of such problems is usually based on the isolation of an internal boundary layer (sublayer), which is the region of the effect of the new phenomena at the wall, and develops in the main boundary layer [1–5]. To take account of the effect of the inhomogeneity of the flow in the main boundary layer on heat transfer through the sublayer, here the method of mean-mass values is used, which, as has been demonstrated using various examples in [4] and in the present work, has a good degree of accuracy (even in the neighborhood of the breakaway point) and is suitable for the profiles of an inhomogeneous flow of rather general form. Based on this, for a laminar boundary layer finite formulas are obtained below for the heat flux to a calorimeter of relatively small size at a permeable wall, which can be used for the analysis of experiments.