Studying anomalous scaling and heat transport of turbulent thermal convection using a dynamical model

2010 ◽  
Vol 239 (14) ◽  
pp. 1346-1352 ◽  
Author(s):  
Emily S.C. Ching
Keyword(s):  
Heat Transport ◽  
Thermal Convection ◽  
Dynamical Model ◽  
Anomalous Scaling

The Effect of Rotation on Thermal Convection

1972 ◽  
Vol 2 (2) ◽  
pp. 92-93 ◽  
Author(s):  
J. O. Murphy ◽  
R. Van Der Borght
Keyword(s):  
Rayleigh Number ◽  
Heat Transport ◽  
Cell Size ◽  
Thermal Convection ◽  
Convection Zone ◽  
Total Heat ◽  
The Sun ◽  
Maximum Heat ◽  
Solar Convection Zone ◽  
Solar Convection

An investigation into the influence of rotation on thermal convection has some applicability in the study of the solar convection zone. Of particular interest is the effect of rotation on the total heat transport and the cell size for maximum heat transport at high Rayleigh number, which is estimated to be as high as 1020 for the Sun.

Effect of Polymer Additives on Heat Transport in Turbulent Thermal Convection

2010 ◽  
Vol 104 (2) ◽  
Author(s):  
Roberto Benzi ◽  
Emily S. C. Ching ◽  
Elisabetta De Angelis
Keyword(s):  
Heat Transport ◽  
Thermal Convection ◽  
Polymer Additives

On heat transport and energy partition in thermal convection with mixed boundary conditions

2019 ◽  
Vol 31 (6) ◽  
pp. 066601 ◽  
Author(s):  
Yada Nandukumar ◽  
Suman Chakraborty ◽  
Mahendra K. Verma ◽  
Rajaram Lakkaraju
Keyword(s):  
Boundary Conditions ◽  
Heat Transport ◽  
Thermal Convection ◽  
Mixed Boundary ◽  
Mixed Boundary Conditions ◽  
Energy Partition

A comparison of turbulent thermal convection between conditions of constant temperature and constant heat flux

2008 ◽  
Vol 595 ◽  
pp. 203-219 ◽  
Author(s):  
R. VERZICCO ◽  
K. R. SREENIVASAN
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Heat Transport ◽  
Constant Temperature ◽  
Thermal Convection ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Experimental Conditions ◽  
Thermal Plumes ◽  
Dimensional Argument

We numerically investigate turbulent thermal convection driven by a horizontal surface of constant heat flux and compare the results with those of constant temperature. Below Ra ≈ 109, where Ra is the Rayleigh number, when the flow is smooth and regular, the heat transport in the two cases is essentially the same. For Ra > 109 the heat transport for imposed heat flux is smaller than that for constant temperature, and is close to experimental data. We provide a simple dimensional argument to indicate that the unsteady emission of thermal plumes renders typical experimental conditions closer to the constant heat flux case.

Heat transport properties of plates with smooth and rough surfaces in turbulent thermal convection

2014 ◽  
Vol 740 ◽  
pp. 28-46 ◽  
Author(s):  
Ping Wei ◽  
Tak-Shing Chan ◽  
Rui Ni ◽  
Xiao-Zheng Zhao ◽  
Ke-Qing Xia
Keyword(s):  
Boundary Layer ◽  
Transport Properties ◽  
Heat Transport ◽  
Thermal Convection ◽  
The Other ◽  
Scaling Exponent ◽  
Present Level ◽  
Experimental Resolution ◽  
Rough Plate ◽  
Heat Transport Properties

AbstractWe present an experimental study of turbulent thermal convection with smooth and rough surface plates in various combinations. A total of five cells were used in the experiments. Both the global $\mathit{Nu}$ and the $\mathit{Nu}$ for each plate (or the associated boundary layer) are measured. The results reveal that the smooth plates are insensitive to the surface (rough or smooth) and boundary conditions (i.e. nominally constant temperature or constant flux) of the other plate of the same cell. The heat transport properties of the rough plates, on the other hand, depend not only on the nature of the plate at the opposite side of the cell, but also on the boundary condition of that plate. It thus appears that, at the present level of experimental resolution, the smooth plate can influence the rough plate, but cannot be influenced by either the rough or the smooth plates. It is further found that the scaling of $\mathit{Nu}$ with $\mathit{Ra}$ for all of the smooth plates is consistent with the classical $1/ 3$ exponent. But the scaling exponent for the global $\mathit{Nu}$ for the cell with both plates being smooth is definitely less than $1/ 3$ (this result itself is consistent with all previous studies at comparable parameter range). The discrepancy between the $\mathit{Nu}$ behaviour at the whole-cell and individual-plate levels is not understood and deserves further investigation.

scholarly journals Enhanced heat transport in thermal convection with suspensions of rod-like expandable particles

2021 ◽  
Vol 928 ◽  
Author(s):  
Shi-Yuan Hu ◽  
Kai-Zhe Wang ◽  
Lai-Bing Jia ◽  
Jin-Qiang Zhong ◽  
Jun Zhang
Keyword(s):  
Thermal Expansion ◽  
Heat Transport ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Thermal Convection ◽  
Temperature Fields ◽  
Glycerol Solution ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard ◽  
Large Rayleigh Number

Thermal convection of fluid is a more efficient way than diffusion to carry heat from hot sources to cold places. Here, we experimentally study the Rayleigh–Bénard convection of aqueous glycerol solution in a cubic cell with suspensions of rod-like particles made of polydimethylsiloxane. The particles are inertial due to their large thermal expansion coefficient and finite sizes. The thermal expansion coefficient of the particles is three times larger than that of the background fluid. This contrast makes the suspended particles lighter than the local fluid in hot regions and heavier in cold regions. The heat transport is enhanced at relatively large Rayleigh number ( $\textit {Ra}$ ) but reduced at small $\textit {Ra}$ . We demonstrate that the increase of Nusselt number arises from the particle–boundary layer interactions: the particles act as ‘active’ mixers of the flow and temperature fields across the boundary layers.

Experimental and numerical investigation of thermal convection in a water saturated porous medium induced by heat exchangers in high temperature borehole thermal energy storage

2021 ◽  
Author(s):  
Victorien Djotsa Nguimeya Ngninjio ◽  
Wang Bo ◽  
Christof Beyer ◽  
Sebastian Bauer
Keyword(s):  
Porous Medium ◽  
Temperature Distribution ◽  
Heat Transport ◽  
Thermal Convection ◽  
Heat Storage ◽  
Saturated Porous Medium ◽  
Storage Unit ◽  
Thermally Induced ◽  
Water Saturated ◽  
Storage Temperatures

<p>Borehole thermal energy storage is a well-established technology for seasonal geological heat storage, where arrays of borehole heat exchangers (BHE) are installed in low permeability geological media dominated by conductive heat transfer. Increasing storage temperatures would increase storage capacities and rates and would thus allow for a better inclusion of BTES in the energy system. When using storage temperatures of up 90°C, however, highly permeable zones or intermediate layers may allow for thermally induced fluid migration and convective heat transport in the storage medium, which may increase heat losses from the storage and thus limit the thermal performance of the BTES system. Therefore, we present results from experimental work and subsequent numerical modelling aimed at quantifying thermally induced convection for a lab-scale BHE in a water saturated porous medium for a temperature range of 20°C to 70°C.</p><p>The experimental heat storage unit consists of a fully water saturated coarse sand within a cylindrical polypropylene barrel of 1.23 m height and 0.6 m radius and a vertical coaxial BHE, which is grouted by a thermally enhanced cement. The barrel is cooled from the outside using ventilators and laboratory air. A grid of 68 thermocouples is emplaced in the storage medium for monitoring the temperature distribution. For the stationary experiment, heat is transferred to the storage unit using a supply temperature of 70°C for 6 days until a steady state temperature distribution is achieved, followed by 3 days of heat recovery. The dynamic experiment begins with 3 days of heating with 70°C followed by 6 cycles of alternating heating at 70°C and cooling at approximately 18°C for 12 hours each.</p><p>The stationary experiment reveals a vertical temperature stratification, with temperatures increasing up to 48°C towards the top of the porous medium, as well as a horizontal temperature gradient along the top of the sand, while the lower part of the barrel and the outer wall remain at the laboratory temperature of approximately 18°C. This temperature distribution has stabilized after about 90 hours and represents a clear tilted thermal front, suggesting a significant contribution of induced thermal convection to the overall heat transport. The cyclic experiment shows a decrease of storage temperatures relative to the stationary experiment, with temperatures near to the BHE at the top of the porous lower by 2.5°C and 4.75°C, respectively, because the heating phase is not long enough to reach the stationary temperature distribution. This lower horizontal temperature gradient indicates a weakened thermal convection, however the thermal stratification is conserved. This shows that even under the cyclic loading conditions thermal convection may impair high temperature BTES operation and efficiency.</p><p>Numerical process simulation of coupled flow and heat transport accounting for variable density and the experimental boundary conditions reproduces the spatial and temporal temperature distribution of both experiments with good accuracy. This shows that induced thermal is causing the observed temperature distributions.</p>

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