Theoritical Investigaion Of Natural Convection Heat Transfer In Heated Vertical Tubes
Journal Title: International Journal of engineering Research and Applications - Year 2018, Vol 8, Issue 11
Abstract
An theoretical investigation of natural convection heat transfer in heated vertical ducts dissipating heat from the internal surface is presented. The ducts are open-ended and circular in cross section. The test section is electrically heated imposing the circumferentially and axially constant wall heat flux. Heat transfer experiment is carried out for four different channels of 45mm. internal diameter and 3.8mm thickness with length varying from 450mm to 850mm. Ratios of length to diameter of the channel are taken as L/D = 10, 12.22, 15.56, and 18.89. Wall heat fluxes are maintained at q// = 250 to 3341 W/m2 . The studies are also carried out on intensified channels of the same geometrical sizes with the discrete rings of rectangular section. Thickness of the rings are taken as t = 2.0, 3.0, 3.8mm; step size (s) of the rings are varying from 75mm to 283.3mm and the other ratios are taken as: ratio s/D = 1.67 to 6.29, ratio t/D = 0.044 to 0.084 and ratio s / t = 19.74 to 141.65. A systematic experimental database for the local steady state natural convection heat transfer behaviour is obtained. The effects of L/D ratio and wall heating condition on local steady-state heat transfer phenomena are studied. The effects of ring thickness and ring spacing on heat transfer behaviour are observed. The present experimental data is compared with the existing theoretical and experimental results for the cases of vertical smooth tubes and also for tubes with discrete rings.
Authors and Affiliations
Ramesh Chandra Nayak, Asish Kumar Patra, Sharmistha Jena
Keywords
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- EP ID EP416596
- DOI 10.9790/9622-0811026570.
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