Buoyancy-driven heat transfer enhancement in a two-dimensional enclosure utilizing nanofluids

Heat transfer augmentation in a two-sided lid-driven differentially heated square cavity utilizing nanofluids

https://www.eis.hu.edu.jo/deanshipfiles/pub10311353.pdf

Numerical study of natural convection in partially heated rectangular enclosures filled with nanofluids

This review pertains to the body of work dealing with internal recirculating flows generated by the motion of one or more of the containing walls. These flows are not only technologically important, they are of great scientific interest because they display almost all fluid mechanical phenomena in the simplest of geometrical settings. Thus corner eddies, longitudinal vortices, nonuniqueness, transition, and turbulence all occur naturally and can be studied in the same closed geometry. This facilitates the comparison of results from experiment, analysis, and computation over the whole range of Reynolds numbers. Considerable progress has been made in recent years in the understanding of three-dimensional flows and in the study of turbulence. The use of direct numerical simulation appears very promising.

/pdf/fluid-mechanics-in-the-driven-cavity-25evptx577.pdf

Fluid mechanics in the driven cavity

Geometry: shape, size, aspect ratio and orientation Flow Type: forced, natural, laminar, turbulent, internal, external Boundary: isothermal (Tw = constant) or isoflux (q̇w = constant) Fluid Type: viscous oil, water, gases or liquid metals Properties: all properties determined at film temperature Tf = (Tw + T∞)/2 Note: ρ and ν ∝ 1/Patm ⇒ see Q12-40 density: ρ ((kg/m) specific heat: Cp (J/kg ·K) dynamic viscosity: μ, (N · s/m) kinematic viscosity: ν ≡ μ/ρ (m/s) thermal conductivity: k, (W/m ·K) thermal diffusivity: α, ≡ k/(ρ · Cp) (m/s) Prandtl number: Pr, ≡ ν/α (−−) volumetric compressibility: β, (1/K)

Convection Heat Transfer

Experiments have been performed to investigate heat dissipation from a heated square cylinder in a channel by oscillating flow. During the experiments, the input power and oscillating amplitude (A) are fixed. The effects of the Reynolds number based on the mean flow velocity (Re = 350 and 540) and the oscillating frequency (0 Hz < f p < 60 Hz) on the heat transfer enhancement are examined. The time-averaged Nusselt number and the Strouhal number were determined for each oscillating condition. The measured Strouhal numbers according to the Reynolds number are compared with the previous results and good agreement is found. The occurrence of the "lock-on" phenomenon is demonstrated for a square cylinder. When the pulsating frequency is in the lock-on regime (fp ~ 2fso), the heat transfer from a square cylinder is dramatically enhanced. The heat transfer enhancement is pronounced as the Reynolds number increases

Heat dissipation from a heated square cylinder in an oscillating channel flow

Mass transfer characteristics for a rotating cup-like cylinder

Effect of circumferential variation of sidewall temperature on buoyant convection in a vertical cylinder

A numerical investigation was carried out for natural convection of air (paramagnetic fluid) in a cubic enclosure subjected to constant gravity and time-periodic magnetizing force. Since the magnetizing force expressed as the gradient of magnetic induction squared in each direction, has three-dimensional characteristics, three-dimensional modeling of system would be required to investigate the effect of magnetizing force more accurately. In this study as a sequent research, the basic analysis of Kang and Hyun [16] was extended to the case of three-dimensional and to cases when the magnitude of magnetizing force is varied. Two geometrical configurations for the location of electrical coils, were considered. The amplification characteristics of heat transfer rate in the cube according to the change of the magnitude of magnetizing force, were investigated especially when the resonance occurs. The numerical results showed that the heat transfer is enhanced appreciably by application of large magnitude of magnetizing force. In addition, the results for two- and three-dimensional cases were also compared.

Resonant enhancement of natural convection in a cubic enclosure under time-periodic magnetizing force

A numerical study is made of the spin-up from rest of a three-layer fluid in a closed, vertically-mounted cylinder. The densities in the upper layer ρ1 middle layer ρ2 and lower layer ρ3 are ρ3>ρ2>ρ1, and the kinematic viscosities are left arbitrary. The representative system Ekman number is small. Numerical solutions are obtained to the time-dependent axisymmetric Navier-Stokes equations, and the treatment of the interfaces is modeled by use of the Height of Liquid method. Complete three-component velocity fields, together with the evolution of the interface deformations, are depicted. At small times, when the kinematic viscosity in the upper layer is smaller than in the middle layer, the top interface rises (sinks) in the central axis (peripheral) region. When the kinematic viscosity in the lower layer is smaller than in the middle layer, the bottom interface rises (sinks) in the periphery (axis) region. Detailed shapes of interfaces are illustrated for several cases of exemplary viscosity ratios.

Jae Min Hyun

Papers

Heat dissipation from a heated square cylinder in an oscillating channel flow

Mass transfer characteristics for a rotating cup-like cylinder

Effect of circumferential variation of sidewall temperature on buoyant convection in a vertical cylinder

Resonant enhancement of natural convection in a cubic enclosure under time-periodic magnetizing force

Flow Characteristics in Spin-Up of a Three-Layer Fluid