摘要

Heat transfer phenomena, which frequently involve convection, are usually described through a connective heat-transfer coefficient h. Precise measurement of h is difficult, since calculation requires knowledge of the temperature gradient between the solid surface and the fluid, measured, possibly, without disturbing the thermal layer. Optical techniques are powerful tools in experimental analysis because of their non-disturbing nature. In this paper, natural convection heat transfer in vertical channels is investigated by applying two different optical techniques, namely, schlieren and holographic interferometry. Experiments were conducted at DITEC, University of Geneva (Italy) and at the Energetic Department of the University of L 'Aquila (Italy) on the same test section. The obtained results are discussed and compared.