Laminar Free Convection Heat Transfer through Horizontal Duct Connecting Two Fluid Reservoirs at Different Temperatures

This technical note develops an analytical result for heat transfer by laminar free convection in a long horizontal parallel-plate channel connecting two reservoirs containing the same fluid but kept at different temperatures. The analysis is based on the integral method. The Nusselt number result is presented in chart form in terms of the Rayleigh number based on height, Ra, and the height/length aspect ratio, h/L.