Simultaneous Visualization of Velocity and Temperature Fields of Transient Natural Convection

2005 ◽  
Vol 127 (8) ◽  
pp. 800-800
Author(s):  
Ichiro Nakane ◽  
Akira Narumi ◽  
Kentaro Fukuda
Keyword(s):  
Natural Convection ◽  
Temperature Fields ◽  
Transient Natural Convection ◽  
Velocity And Temperature Fields ◽  
Simultaneous Visualization

New benchmark solutions for transient natural convection in partially porous annuli

2016 ◽  
Vol 26 (3/4) ◽  
pp. 1187-1225 ◽  
Author(s):  
Nicola Massarotti ◽  
Michela Ciccolella ◽  
Gino Cortellessa ◽  
Alessandro Mauro
Keyword(s):  
Natural Convection ◽  
Free Convection ◽  
Transient Flow ◽  
Flow Behavior ◽  
Outer Radius ◽  
Temperature Fields ◽  
Content Type ◽  
Transient Natural Convection ◽  
Velocity And Temperature Fields ◽  
Benchmark Solutions

Purpose – The purpose of this paper is to focus on the numerical analysis of transient free convection heat transfer in partially porous cylindrical domains. The authors analyze the dependence of velocity and temperature fields on the geometry, by analyzing transient flow behavior for different values of cavity aspect ratio and radii ratio; both inner and outer radius are assumed variable in order to not change the difference ro-ri. Moreover, several Darcy numbers have been considered. Design/methodology/approach – A dual time-stepping procedure based on the transient artificial compressibility version of the characteristic-based split algorithm has been adopted in order to solve the transient equations of the generalized model for heat and fluid flow through porous media. The present model has been validated against experimental data available in the scientific literature for two different problems, steady-state free convection in a porous annulus and transient natural convection in a porous cylinder, showing an excellent agreement. Findings – For vertically divided half porous cavities, with Rayleigh numbers equal to 3.4×106 for the 4:1 cavity and 3.4×105 for the 8:1 cavity, the numerical results show that transient oscillations tend to disappear in presence of cylindrical geometry, differently from what happens for rectangular one. The magnitude of this phenomenon increases with radii ratio; the porous layer also affects the stability of velocity and temperature fields, as oscillations tend to decrease in presence of a porous matrix with lower value of the Darcy number. Research limitations/implications – A proper analysis of partially porous annular cavities is fundamental for the correct estimation of Nusselt numbers, as the formulas provided for rectangular domains are not able to describe these problems. Practical implications – The proposed model represents a useful tool for the study of transient natural convection problems in porous and partially porous cylindrical and annular cavities, typical of many engineering applications. Moreover, a fully explicit scheme reduces the computational costs and ensures flexibility. Originality/value – This is the first time that a fully explicit finite element scheme is employed for the solution of transient natural convection in partially porous tall annular cavities.

Hot-Film Measurement of Natural Convection in Liquid Gallium With and Without Magnetic Fields

Volume 1 ◽  
2004 ◽  
Author(s):  
B. Xu ◽  
B. Q. Li ◽  
D. E. Stock
Keyword(s):  
Magnetic Field ◽  
Temperature Field ◽  
Natural Convection ◽  
External Magnetic Field ◽  
Narrow Range ◽  
Temperature Fields ◽  
Liquid Gallium ◽  
Numerical Predictions ◽  
Velocity And Temperature Fields ◽  
Hot Film

The velocity and temperature fields induced by natural convection in liquid gallium were measured. Measurements were taken with and without an external magnetic field applied to the liquid gallium. The velocity field was measured with a hot-film anemometer and the temperature field with a thermocouple. The hot film was calibrated over a narrow range of temperatures in a rotating turntable filled with liquid gallium. The external magnetic field damped both the velocity and temperature fields compared to similar conditions when no external magnetic field was present. The experimental results compared reasonably well with previous numerical predictions.

Unsteady Natural Convection in the Vicinity of a Doubly Infinite Vertical Plate

1962 ◽  
Vol 84 (4) ◽  
pp. 334-338 ◽  
Author(s):  
J. A. Schetz ◽  
R. Eichhorn
Keyword(s):  
Heat Flux ◽  
Natural Convection ◽  
Surface Heat Flux ◽  
Vertical Plate ◽  
Surface Heat ◽  
Temperature Fields ◽  
Flow Equations ◽  
Velocity And Temperature Fields ◽  
Unsteady Natural Convection ◽  
Infinite Vertical Plate

The viscous flow equations for the unsteady free convection of a fluid near a doubly infinite vertical plate whose temperature or heat flux is an arbitrary function of time are treated by means of Laplace transforms. Exact solutions are obtained for several typical examples with arbitrary Prandtl number. The results are then generalized to give integral expressions for the velocity and temperature fields due to any prescribed time variation in wall temperature or surface heat flux.

Transient Natural Convection of Water in a Horizontal Pipe With Constant Cooling Rate Through 4°C

1976 ◽  
Vol 98 (4) ◽  
pp. 581-587 ◽  
Author(s):  
K. C. Cheng ◽  
M. Takeuchi
Keyword(s):  
Natural Convection ◽  
Transient Flow ◽  
Temperature Fields ◽  
Freezing Process ◽  
Horizontal Pipe ◽  
Transfer Rates ◽  
Transient Natural Convection ◽  
Anomalous Density ◽  
Horizontal Cylinders ◽  
Relationship Of

A theoretical analysis is carried out to study the influence of an anomalous density-temperature relationship of water on the transient natural convection in horizontal cylinders with wall temperature decreasing at a uniform rate. Numercial solutions are obtained for three cases involving different cooling rates, pipe diameters, and initial uniform water temperatures for temperature conditions between 0 and 7°C. The transient flow and temperature fields, and local and overall heat transfer rates are presented to study the inversion of flow patterns caused by the maximum density at 4°C. The numerical results are compared with the experimental measurements and predictions of a quasi-steady boundary-layer model reported by Gilpin [2], and generally a good agreement is observed. Some implications on the subsequent freezing process are pointed out.

Natural Convection in Cubic and Rhomb-Shaped Enclosures

2013 ◽  
Author(s):  
Milorad B. Dzodzo
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Temperature Fields ◽  
Nusselt Numbers ◽  
Different Temperatures ◽  
Vertical Walls ◽  
Laminar Natural Convection ◽  
Velocity And Temperature Fields ◽  
Prandtl Numbers ◽  
Volume Method

Laminar natural convection in cubic and rhomb–shaped enclosures (rhomb angles 59°, 44° and 28.2°) with two opposite vertical walls kept at different temperatures was investigated experimentally and numerically. The enclosures were filled with glycerol and the Rayleigh (Ra) and Prandtl (Pr) numbers ranged from 2,000<Ra<369,000 and 2,680<Pr<7,000. The visualization of the velocity and temperature fields was obtained by using Plexiglass and liquid crystal particles as tracers. The finite volume method based on the finite difference approach was applied for numerical analysis. The velocity and temperature fields and average Nusselt numbers were found as a function of the Reyleigh and Prandtl numbers. Comparison of the average Nusselt numbers for cubic and rhomb-shaped enclosures indicates decrease of heat transfer for the cases when the lower and upper vertical walls of the rhomb-shaped enclosures are at lower and higher temperatures, respectively. This is due to the tendency of fluid stratification in the lower and upper corners.

Velocity and Temperature Fields Measurement of Natural Convection Flow Using Thermochromic Liquid Crystals

2005 ◽  
Author(s):  
Vale´rie Me´nard ◽  
Adel Stitou ◽  
Ste´phane Le Masson ◽  
David No¨rtersha¨user ◽  
Pierre Millan
Keyword(s):  
Liquid Crystal ◽  
Natural Convection ◽  
Particle Deposition ◽  
Temperature Fields ◽  
Convection Flow ◽  
Simple Relationship ◽  
Natural Convection Flow ◽  
Calibration Methods ◽  
Intensity Response ◽  
Velocity And Temperature Fields

Based on a particular property of some liquid crystal to reflect a specific wavelength for a specific temperature, Particle Image Velocimetry and Thermometry (PIVT) is a method allowing to measure simultaneously velocity and temperature fields. In a first part, this study discusses PIVT calibration methods and especially the effect of liquid crystal particle deposition on hue and intensity response. An experimental set-up is designed and the results confirm the high variations of intensity response with time and the need to use a simple relationship between hue and temperature. In a second place, these results are used to apply PIVT to an unsteady natural convection flow in a cavity containing an internal heat source.

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