Heat fluxes distribution and uncertainty in low-Reynolds flow regimes inside a ribbed channel

Experimental studies on the local convective heat transfer enhancement induced by ribs in channels are generally carried out in steady state, by imposing a known heat flux on the ribbed surface and subsequently retrieving the convective heat flux by means of a local heat balance, i.e. by subtracting all the non-convective heat fluxes from the source term. Such heat fluxes are retrieved from temperature measurements by means of models, whose complexity can range from simple algebraic expressions to complex simulations. In this context, an experimental technique based on FEM simulations, a radiative model for semi-transparent enclosures, and a filtering technique to retrieve the heat fluxes across the plane of the heated surface has been developed and tested in a 1:10 AR channel, for Reynolds number ranging from 650 to 7500 and a flow of air. This paper presents a discussion on the heat flux distribution as a function of the Reynolds number for a streamwise-pointing chevron (V) rib configuration with 60° angle of attack, with P/e = 20, showing the increasing weight of non-convective heat dissipations as the Reynolds number decreases, and their effect on the uncertainty of the Nusselt number measurement.