Asymmetrical Non-Uniform Heat Flux Distributions For Laminar Flow Heat Transfer With Mixed Convection In a Horizontal Circular Tube

Abstract

Non-symmetric heat flux distributions in terms of gravity in solar collector tubes influence buoyancy-driven secondary flow which has an impact on the associated heat transfer and pressure drop performance. In this study influence of the asymmetry angle (0°, 20°, 30° and 40°) with regard to gravity for non-uniform heat flux boundaries in a horizontal circular tube was investigated numerically. A stainless steel tube with an inner diameter of 62.68 mm, a wall thickness of 5.16 mm, and a length of 10 m was considered for water inlet temperatures ranging from 290 K to 360 K and inlet Reynolds numbers ranging from 130 to 2000. Conjugate heat transfer was modelled for different sinusoidal type outer surface heat flux distributions with a base-level incident heat flux intensity of 7.1 kW/m 2. It was found that average internal heat transfer coefficients increased with the circumferential span of the heat flux distribution. Average internal and axial local heat transfer coefficients and overall friction factors were at their highest for symmetrical heat flux cases (gravity at 0º) and lower for asymmetric cases. The internal heat transfer coefficients also increased with the inlet fluid 2 temperature and decreased with an increase in the external heat loss transfer coefficient. Friction factors decreased with an increase in fluid inlet temperature or an increase in the external heat loss transfer coefficients of the tube model.

Two-Dimensional Flow Through the Uniformly Porous Horizontal Pipe with Thermal Radiation and Cross-Diffusion Effects

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Two-phase investigation of water-Al2O3 nanofluid in a micro concentric annulus under non-uniform heat flux boundary conditions

“…Consequently, many researchers have investigated various problems around this issue. The proposed approaches for this purpose are the use of nanofluidics and non-uniform boundary conditions including non-uniform heat flux and non-uniform temperature (Ndenguma et al, 2017;Okafor et al, 2018;Wakif et al, 2018). HFF 30,4 Because of the low thermal conductivity of conventional heat transfer fluids such as water, oil and so forth, there has been a strong tendency among researchers to develop advanced heat transfer fluid with substantially higher thermal conductivities.…”

“…Consequently, many researchers have investigated various problems around this issue. The proposed approaches for this purpose are the use of nanofluidics and non-uniform boundary conditions including non-uniform heat flux and non-uniform temperature (Ndenguma et al , 2017; Okafor et al , 2018; Wakif et al , 2018).…”