A Study on Natural Convection Enhancement in Vertical Tubes with Internal Structures: Implications for Industrial Cooling and Thermal Pollution Control

IJEP 46(5): 473-479 : Vol. 46 Issue. 5 (May 2026)

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Abinash Sahoo1, Ramesh Chandra Nayak2*, Ajit K. Senapati1, Mahesh Vasantrao Kulkarni3 and T. Venkatamuni4

1. GIET University, Department of Mechanical Engineering, Gunupur – 765 022, Odisha, India
2. Synergy Institute of Technology, Department of Mechanical Engineering, Bhubaneswar – 751 032, Odisha, India
3. Dr. Vishwanath Karad MIT World Peace University, Department of Mechanical Engineering, Pune – 411 038, India
4. V.S.B Engineering College, Department of Mechanical Engineering, Karur – 639 111, Tamil Nadu, India

Abstract

Buoyancy-driven heat exchange within upright channels is essential for addressing thermal pollution and enhancing the efficiency of industrial cooling units. This experimental work focuses on buoyancy-based heat flow from a heated object; heat transfer occurs through cylindrical ducts, with and without internal obstacles. Cylindrical ducts were subjected to a uniform heat flux due to surface contact with the heated object. The duct heat-flux range varied with the heat generated by the object. Experiments were conducted on two channels with internal diameters of 52 mm, wall thicknesses of 6 mm and lengths of 650 mm, yielding a length-to-diameter ratio (L/D) of 12.5. The applied wall heat flux (q”) ranged from 552-1997 W/m². An additional study was carried out on pipes of the same dimensions, alongwith internal rectangular rings having 4 mm thickness and 65-195 mm step size between rings. Experimental results, including temperature profiles along the tube wall and at the fluid exit, were obtained for both conditions with and without rings and a comparative statement is presented. The results disclose the impact of internal rings, tube length and duct heat flux. The presence of internal rings and a maximum length-to-diameter ratio of the tube approach enhancement of heat transfer from the heated object through the tube. This information for cooling system arrangement contributes toward reduced thermal pollution and improvement of the atmospheric environment.

Keywords

Natural convection, Vertical tubes, Internal structures, Heat transfer enhancement, Thermal pollution control, Industrial cooling, Ring spacing, Passive cooling techniques, Wall heat flux, Length-to-diameter ratio

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