Augmentation of Natural Convection Heat Transfer from Horizontal Circular Cylinder by Means of Helical-Coil-Turns.

Document Type : Research Studies

Author

Lecturer at Mechanical Power Engineering Department., Faculty of Engineering., El-Mansoura University., Mansoura., Egypt.

Abstract

Augmentation of steady natural convection heat transfer from horizontal cylinder were studied experimentally. The test section consisted of a brass circular cylinder, of 301 mm length and diameters of 21.5/ 12.2 mm, heated with a constant heat flux supplied by an electrical resistive heater made of nickel-chrome wire coil. The experimental data have been obtained when the test cylinder is covered with eight type of helical-wire-coils wounded around it as well as when the cylinder is bare. The number of helix per meter length (NC) varied from 178 to 835 and the number of turns of each helical-coil per meter length (Nt) Varied from 50 to 196 at cylinder-to-helix diameters ratio (D/d) of 4.22. The tests were conducted in aim in the range of Rayleigh number of 2000 to 52000 and Prandtl number of nearly The results of heat transfer coefficient are represented in the relation of average Nusselt number versus Rayleigh number. The relations indicate that (Nu) is a significant function of (Ra), (Ne) and (Nt).
 The augmentation of heat transfer in case of use the helical-wire-coils varied from 5 to 106 % compared with the bare cylinder. 

Main Subjects

MEJ- Mansoura Engineering Journal
Volume 18, Issue 3
September 1993
Pages 51-62

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