Influence of baffles upon natural-convective steady-state heat transfers inwards across horizontal eccentric annuli

Abstract

Flow patterns, temperature distributions and steady-state heat transfers inwards across a horizontal annular, atmospheric-pressure, air-filled eccentric cavity have been determined. Several different configurations of two low-conductivity baffles (arranged symmetrically with respect to the vertical plane through the centre-lines of the pipes), inserted across the cavity and extending its whole length, were tested. With the horizontal inner pipe located at a vertical eccentricity of −0·65 (i.e. in the lower region of the outer pipe), the optimal inclination of the two baffles, corresponding to the least rate of convective heat exchange, was achieved at ±140° from the vertically downwards radius vector emanating from the centre of the inner pipe. This enabled a reduction of ∼6% in the steady-state convective heat leak to be achieved compared with that for the plain eccentric annulus under similar temperature differences between the pipes. However, by using a vertical baffle (i.e. at an angle of 0°), an increase of ∼ 14% in the convective heat leak through the air occurred. The results agree qualitatively with those expected on the basis of previous studies for the inverse case (of a concentric annulus) with the heat flowing outwards.