Experimental study on local variation of buoyancy-aided mixed convection heat transfer in a vertical pipe using a mass transfer method

Local heat transfer of buoyancy-aided mixed convective flow in a vertical pipe was investigated experimentally through analogous mass transfer experiments using a copper electroplating system. The Rayleigh number ranged from 1.69 × 10⁸ to 2.11 × 10¹³ and the Reynolds number from 210 to 16,050, covering laminar and turbulent regimes, respectively. The test results for laminar- and turbulent-forced convections agreed well with existing forced convection correlations. The local heat transfer rates of laminar mixed convective flow were higher than those of the forced convection correlation and decreased monotonously downstream. However, the local heat transfer rates of the turbulent mixed-convective flow showed heat transfer impairment compared with the forced convection case, as well as a non-monotonous behavior along the axial position due to buoyancy influences. Our analysis results confirmed the successful application of a mass transfer system to heat transfer studies.