What's new in convective heat transfer?

This paper describes the quest for invariant descriptors of the convective process, and the new requirements those descriptors put on quantitative full-field thermal imaging. There is increasing need, in applications, for heat transfer descriptors which can deal with non-uniform thermal boundary conditions, including those induced by conjugate effects. This paper discusses two approaches which have arisen within the past 10 years: (1) the use of hadiabatic and Tadiabatic to describe the convective process and more recently, (2) the emergence of discretized Green's functions for convection. Both of these approaches acknowledge the effects of upstream heat transfer on local behavior but both do so using coefficients which, themselves, are invariant with respect to changes in the thermal boundary conditions. Thus measurements made in the lab can be applied in the field, under different thermal boundary conditions. Both approaches can be used in complex flow fields, such as flows on surfaces with obstructions. To realize the full potential of either approach, the uncertainties in full-field optical data acquistion techniques must be reduced by about a factor of 3.