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Heat Transfer Research
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Heat Transfer Research

DOI: 10.1615/HeatTransRes.2017017830
pages 1433-1458

EFFECTS OF WALL CONJUGATION AND FLUID AXIAL CONDUCTION IN CIRCUMFERENTIALLY PARTLY HEATED PIPES AND MINIPIPES

Ulas Atmaca
Department of Mechanical Engineering, Selcuk University, 42031 Konya, Turkey
Şefik Bilir
Department of Mechanical Engineering, Selcuk University, 42031 Konya, Turkey
Ali Ateş
Department of Mechanical Engineering, Selcuk University, 42031 Konya, Turkey

ABSTRACT

Transient conjugated heat transfer in circumferentially partly heated thick-walled pipes and minipipes with thermally developing laminar flows is investigated, involving three-dimensional wall conduction and fluid axial conduction. The problem is handled for an initially isothermal, two-regional infinite pipe, for which the upstream region is completely insulated and the downstream region is circumferentially partly insulated by considering an instant increase in the outer wall temperature of the other circumferential part in the downstream region. Solution is made numerically by a finite-difference method, and a parametric study is conducted to analyze the effects of four defining parameters, namely, the Peclet number, wall-to-fluid thermal conductivity ratio, wall-to-fluid thermal diffusivity ratio, and wall thickness ratio, on heat transfer characteristics. The results show that in both the wall and the fluid sides, besides backward heat transfer due to axial conduction, a large amount of heat is transferred because of angular conduction from the circumferentially heated to the unheated part of the pipe. Wall conjugation highly compensates the effects of partial heating and an important percentage of heat transfer to fluid is realized from the unheated circumferential part of the pipe. The results are also seen to be much affected by the parameter values.