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

scholarly journals Effects of polymer additives in the bulk of turbulent thermal convection

2015 ◽  
Vol 784 ◽  
Author(s):  
Yi-Chao Xie ◽  
Shi-Di Huang ◽  
Denis Funfschilling ◽  
Xiao-Ming Li ◽  
Rui Ni ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Transport ◽  
Thermal Convection ◽  
Polymer Concentration ◽  
Local Heat ◽  
Heat Fluxes ◽  
Small Scale ◽  
Polymer Additives ◽  
Thermal Plumes ◽  
Minute Amount

We present experimental evidence that a minute amount of polymer additives can significantly enhance heat transport in the bulk region of turbulent thermal convection. The effects of polymer additives are found to be the enhancement of coherent heat fluxes and suppression of incoherent heat fluxes. The enhanced heat transport is associated with the increased coherency of thermal plumes, as a result of the suppression of small-scale turbulent fluctuations by polymers. The incoherent heat flux, arising from turbulent background fluctuations, makes no net contribution to heat transport. The fact that polymer additives can increase the coherency of thermal plumes is supported by the measurements of a number of local quantities, such as the extracted plume amplitude and width, the velocity autocorrelation functions and the velocity–temperature cross-correlation coefficient. The results from local measurements also suggest the existence of a threshold value for the polymer concentration, only above which significant modification of the plume coherent properties and enhancement of the local heat flux can be observed. Estimation of the plume emission rate suggests a stabilization of the thermal boundary layer by polymer additives.

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.

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.

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