Özet:

An experimental study on natural convection heat transfer from two parallel horizontal cylinders in horizontal cylindrical enclosure was carried out under condition of constant surfaces temperature for two cylinders and cylindrical enclosure. The study included the effect of Rayleigh number, rotation angle that represent the confined angle between the passing horizontal plane in cylindrical enclosure center and passing line in two cylinders centers, and the spaces between two cylinders on their heat loss ability. An experimental set-up was used for this purpose which consist water container, test section which is formed of plastic cylinder that represent the cylindrical enclosure, and two heating elements which are formed of two copper cylinders with (19 mm) in diameters heated internally by electrical sources that represents transfer and heat loss elements through this set-up. The experiments were done at the range of Rayleigh number between (), cylinders rotation angle at (), and spacing ratio at (). The study showed that the ability of heat loss from two cylinders is a function of Rayleigh number, cylinders rotation angle, and the spaces between them. This ability is increased by increasing of Rayleigh number and it was showed that this ability reaches maximum value at the first cylinder () and minimum value at the second cylinder () at spacing ratio (S/D=3) and rotation angle () for the first and () for the second cylinder respectively. The effective variables on natural convection heat transfer from the above two cylinders are related by two correlating equations, each one explains dimensionless relation of heat transfer from each cylinder that represented by Nusselt number against Rayleigh number, rotation angle, and the spacing ratio between two cylinders.

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