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Free convective heat transfer from horizontal, inclined, and vertical cylinders in air was experimentally studied by means of a Mach-Zehnder interferometer. The effect of the Rayleigh number on both local Nusselt numbers along the perimeter of the cylinder and the average Nusselt number over the surface of the cylinder was investigated by varying the experimental Rayleigh numbers in a range of 1.1 × 104 to 3.4 × 105. The effect of orientation of the cylinder on heat transfer rates was also examined by varying the angle of inclination of the cylinder with respect to the horizontal. Angles of 0°, 45°, 60°, 75°, and 90° were studied. The experimental results in terms of the Nusselt number were correlated as a function of the Rayleigh number for different angles. A universal equation is given that correlates the experimental results for all angles studied. The present results are in good agreement with those of previous researchers.

An experimental and numerical study is performed on natural convection heat transfer from a horizontal isothermal inner tube to a surrounding isothermal outer tube. Experimental results are obtained using a Mach-Zehnder interferometer and the governing equations are solved numerically using a variational finite element method. Emphasis is given to the effect of inner tube eccentricity and azimuthal angular location on the thermal field in the annulus. Results are obtained for air at three specific Rayleigh numbers in the transition regime, Ra = 5 × 10 2 , 10 3 , 1.5 × 10 3 .

An interferometric technique was used to study coupled convective heat transfer for an inclined solar collector. The collector was simulated by an inclined, closed rectangular cavity which was heated isothermally at the bottom plate and cooled by natural convection at the top plate. Both plates had dimensions 457.2 mm wide and 424.2 mm long. Infinite interferograms, for temperature field visualization, and finite interferograms for analysis were obtained. The parameters studied were Rayleigh number, aspect ratio, and angle of inclination. The Rayleigh number was varied from subcritical to 6 × 105 and the aspect ratio was changed from 6.68 to 33.4. The angle of inclination was 15° and 60° to the horizontal. The temperature on the cold plate was found to increase with distance from the lower boundary. Temperature reversal occurs in the cavity and first appears in the corner regions. The temperature gradients were obtained and thus the local heat transfer coefficients were calculated indicating a strong dependence from side boundaries. In comparison with reports where both surfaces were isothermal a significant difference in the dependence of average Nusselt number on Rayleigh number was found. At high Rayleigh numbers the average Nusselt number is less dependent on Rayleigh number for the cavity with a non-isothermal top surface than for the isothermal top surface.

P-v-T properties are tabulated for superheated heavy water vapour (660 to 760 Deg. F. and 1030 to 2130 psia). In this range values of pressure appear in agreement with experimental data to 1.0%. Th...