Asymmetrical non-uniform heat flux distributions for laminar flow heat transfer with mixed convection in a horizontal circular tube

Loading...
Thumbnail Image

Date

Authors

Okafor, Izuchukwu F.
Dirker, Jaco
Meyer, Josua P.

Journal Title

Journal ISSN

Volume Title

Publisher

Taylor and Francis

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 the 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/m2. 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 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.

Description

Keywords

Heat flux, Transfer coefficient, Non-uniform heat fluxes, Local heat transfer coefficient, Heat flux distributions, Fluid inlet temperature, Conjugate heat transfer, Tubular steel structures, Tubes (components), Stainless steel, Reynolds number, Laminar flow, Heat transfer coefficients, Heat transfer, Heat losses, Friction, Pressure drop, Internal heat transfer

Sustainable Development Goals

Citation

Izuchukwu F. Okafor, Jaco Dirker & Josua P. Meyer (2019) AsymmetricalNon-Uniform Heat Flux Distributions For Laminar Flow Heat Transfer With MixedConvection In a Horizontal Circular Tube, Heat Transfer Engineering, 40:1-2, 109-127, DOI:10.1080/01457632.2017.1421055.