Effects of temperature-dependent viscosity on fluid flow and heat transfer in a helical rectangular duct with a finite pitch

Balasubramanian

Proceedings of the Institution of Mechanical Engineers, Part E:

et al. 2019

Wavy microchannels have been shown to possess improved heat transfer capabilities because of greater fluid mixing and boundary layer thinning. In this study, fluid flow and heat transfer characteristics of circular wavy microchannels with tangentially branched secondary channels, were numerically investigated. Its heat transfer and fluid flow characteristics were compared with other specific wavy microchannel geometries. Three-dimensional numerical studies were carried out in the Reynolds number range of 100–300 with uniform heat flux wall boundary condition, using Ansys Fluent commercial software. Validation of the model was done with experimental data from literature. Circular wavy microchannels, owing to constant curvature, lead to nearly constant Dean vortices strength. The tangential branched secondary channels helped in further effective fluid mixing and in reinitializing the boundary layer. These phenomena had significant effect on its heat transfer and fluid flow behavior. Circular wavy microchannels with tangentially branched secondary channels, having secondary channel width to primary channel width ratio (ω) equal to 0.25, showed higher overall performance than other designs considered in the present study. Velocity vectors, velocity and temperature contours are presented to explain the fluid flow and heat transfer characteristics. It is observed that circular wavy microchannels with tangentially branched secondary channel design (ω = 0.25) gives 39.36% higher Nusselt number with 21% increased pressure drop as compared to sinusoidal wavy microchannel design. The overall performance factor of circular wavy microchannel with tangentially branched secondary channel design (ω = 0.25) is higher in the Reynolds number range of 100–250 than all other designs considered in this study.

Section: Microchannel Model and Mathematical Formulationmentioning

confidence: 99%

Section: Microchannel Model and Mathematical Formulationmentioning

confidence: 99%

Numerical investigation of heat transfer and fluid flow characteristics in circular wavy microchannel with tangentially branched secondary channels

Balasubramanian

Proceedings of the Institution of Mechanical Engineers, Part E:

et al. 2019

“…reported about the viscous dissipation impact on the Cross model with heat transfer analysis. Recently, many researchers have made investigations into heat transport 12‐27 …”

Section: Introductionmentioning

confidence: 99%

Interpretation of infinite shear rate viscosity and a nonuniform heat sink/source on a 3D radiative cross nanofluid with buoyancy assisting/opposing flow

et al. 2021

With respect to bionomical concerns and energy security, the performance of refrigeration systems should be enriched, which can be done by improving the characteristics of working liquids. Nanoliquids have attracted interest in the fields of engineering and industry due to their prominent thermophysical characteristics. Researchers have used nanoliquids as working liquids and noticed significant fluctuations in thermal execution. In this study, our prime aim was to study the impact of thermal radiation and varying thermal conductivity on a cross‐nanofuid with the addition of a nonuniform heat sink–source, chemical process, and activation energy (AE) together with effects of assisting and opposing buoyancy. Furthermore, the relationship of zero‐mass flux together with the mechanism of thermophoresis and Brownian motion is considered. Traditionalistic transformations gave the ordinary differential equations (ODEs), which are further dealt with the approach of the Shooting Scheme to change the boundary value problem (BVP) into an initial value problem (IVP) and a numerical comparison is made with the Matlab solver package bvp4c. Bvp4c is based upon a collocation scheme, which yields numeric outcomes for nonlinear ODEs with IVP. Impacts of the involved parameters on mass transfer profile, heat, and momentum fields are shown through graphs. Mass transfer of the cross nanofluid increases with increasing values of AE parameter. Values of physical quantities like drag forces, rate of transport of heat and mass in the case of assisting/opposing flow are tabulated. The drag force magnitudes are greater for enhancing values of M, a, and n, while on the other hand, the opposing tendency is seen for We1 and We2. The magnitude of the rate of heat transport (Nusselt number) falls for greater values of m, σ, δ, and Nt, but in contrast, it accelerates for E, Pr, and n.

“…Many industries are interested in working fluids undergoing thermal processes and there is continuous research in optimizing the size and cost of heat exchangers and enhancing the rate of heat transfer. Some fluids have pressure and temperature dependent properties with different degrees, the variation of viscosity as a result of temperature change for example is more significant than other properties for most fluids [1]. The most common practice in a lot of studies is to use constant thermophysical properties or only temperature-dependent viscosity fluids to simplify the complexity level of the fluid model with tolerable accuracy since temperature-dependent fluids are more complex to solve than fluids with constant properties [1,2].…”

Section: Introductionmentioning

confidence: 99%

“…Some fluids have pressure and temperature dependent properties with different degrees, the variation of viscosity as a result of temperature change for example is more significant than other properties for most fluids [1]. The most common practice in a lot of studies is to use constant thermophysical properties or only temperature-dependent viscosity fluids to simplify the complexity level of the fluid model with tolerable accuracy since temperature-dependent fluids are more complex to solve than fluids with constant properties [1,2]. However, in the aim of more accurate results and the seek for more optimized solutions with the aid of computational tools, thermophysical temperature-dependent properties of fluids have been recently a topic of engineering interest.…”

Section: Introductionmentioning

confidence: 99%

Turbulent Axisymmetric Non-Isothermal Flow of The Hitec Molten Salt with Temperature Dependent Properties: A Numerical Investigation

ElShafei

Guaily

Boraey

2021

ARFMTS

This study aims to investigate the Hitec molten salt’s thermal-hydraulic behavior in a smooth round pipe under broad ranges of surface heat flux and Reynolds number (q = 104 – 105 W/m2, Re = 104 – 105). Mesh independent study was performed to ensure the robustness of the model to achieve accurate solutions. Presentation of temperature, pressure and thermophysical properties for multiple cases are presented and discussed. Temperature gradient decreases at high Reynolds number leading to small change in thermo-physical properties. While pressure seems not to be affected by the change in the applied surface heat flux, it increasess linearly across the pipe with the increase in Reynolds number. This analysis aims to provide better understanding of the thermal-hydraulic behavior for fluids with temperature dependent properties for a wide range of Re and surface heat flux.