Turbulent duct flow with streamwise nonuniform heating at the duct wall

A combined experimental and analytical/numerical investigation has been carried out for turbulent flow in a flat, rectangular duct with streamwise nonuniform heating at one of the principal walls. The investigated heating pattern consisted of adiabatic zones periodically inserted between isothermal heated zones. The relative streamwise lengths of the heated zones and the adiabatic zones were varied parametrically, as was the Reynolds number. Heat transfer coefficients were determined at each of the heated zones, both in the thermal entrance region and in the fully developed region. It was found that the presence of the adiabatic zones can give rise to substantial enhancement of the heat transfer coefficients at the heated zones. For a duct of fixed overall length, the use of the adiabatic zones represents a loss in transfer surface area, which brings about a net decrease in the overall rate of heat transfer. The agreement between the numerical and experimental results was typically in the two percent range, an outcome which recommends the numerical model as a tool for studying other nonuniform heating patterns.