Analysis of heat transfer in a cylindrical annulus fitted with two inverted trapezoidal isothermal blocks attached symmetrically at inner cylinder.

This paper presents a numerical study of the thermoconvective effects induced by the presence of two inverted trapezoidal isothermal blocks of height h and width l = 0.109, in an annular space confined between two isothermal coaxial horizontal cylinders filled with air, Pr = 0.7, and of radii ratio, R = 2. This investigation gives an accurate description of the influence of the height of blocks on the flow pattern and on the average heat transfer rate, Nug, for a range of Rayleigh numbers Ra up to 104 and for an angular position of blocks φm = 0.82π. The steady solutions obtained are either uni- or bi-cellular flows. A critical height hc,a is determined, characterizing the appearance of the bicellular flow. The numerical study identified a heat transfer enhancement strategy by properly selecting adequate heating block heights. In particular, it appears that increasing h for a given Rayleigh number does not always lead to better heat transfer rates. [ABSTRACT FROM AUTHOR]