Buoyancy Effects on Cooling a Heat Generating Porous Medium: Coal Stockpile

In this study, the effects of buoyancy on heat and fluid flow within and around a coal stockpile are numerically investigated by both a FORTRAN code and the commercially available CFD-ACE software. Numerical simulations are backed up by theoretical results based on scale analysis. Transient variation of maximum temperature inside the coal stockpile is monitored for different coal properties. Besides, the effects of reduction of the stockpile porosity on the prevention of self-heating are studied. In doing so, on top of numerical results and as an independent prediction tool, Bejan’s Intersection of Asymptotes method is applied to find the optimum porosity of the stockpile. Finally, the energy flux vectors are used to track the correct path of energy transportation in the computational domain.     

Experimental determination and prediction of methane hydrate stability in alcohols and electrolyte solutions

In petroleum exploration and production operations, gas hydrates pose serious flow assurance, economic and safety concerns. Thermodynamic inhibitors are widely used to reduce the risks associated with gas hydrate formation. In this communication, in order to establish the effects of salts and thermodynamic inhibitors on the locus of incipient hydrate–liquid water–vapour (H–L_W–V) curve, we report new experimental dissociation data for various quaternary systems, methane/water/thermodynamic inhibitor/salts for a pressure range of 6.89–29 MPa.     

Effects of temperature-dependent viscosity variation on entropy generation,heat and fluid flow through a porous-saturated duct of rectangular cross-section

Effect of temperature-dependent viscosity on fully developed forced convection in a duct of rectangular cross-section occupied by a fluid-saturated porous medium is investigated analytically. The Darcy flow model is applied and the viscosity-temperature relation is assumed to be an inverse-linear one. The case of uniform heat flux on the walls, i.e. the H boundary condition in the terminology of Kays and Crawford [12], is treated. For the case of a fluid whose viscosity decreases with temperature, it is found that the effect of the variation is to increase the Nusselt number for heated walls. Having found the velocity and the temperature distribution, the second law of thermodynamics is invoked to find the local and average entropy generation rate. Expressions for the entropy generation rate, the Bejan number, the heat transfer irreversibility, and the fluid flow irreversibility are presented in terms of the Brinkman number, the Peclet number, the viscosity variation number, the dimensionless wall heat flux, and the aspect ratio (width to height ratio). These expressions let a parametric study of the problem based on which it is observed that the entropy generated due to flow in a duct of square cross-section is more than those of rectangular counterparts while increasing the aspect ratio decreases the entropy generation rate similar to what previously reported for the clear flow case by Ratts and Raut [14].     

Pore-Scale Numerical Experiment on the Effect of the Pertinent Parameters on Heat Flux Splitting at the Boundary of a Porous Medium

Pore-scale heat and fluid flow simulation through reconstructed porous media is presented with the aim of investigating the physics of heat flux splitting at the boundary of porous media. As such, the effects of the solid to fluid thermal conductivity ratio, porosity, pore-scale Reynolds number, Prandtl number and heat conduction within the solid matrix are investigated. The results of the present study for heat transfer coefficient and pressure drop are compared with available experimental data and good agreement was observed. The validated results are then used to investigate the validity of the existing volume-averaged models. It was observed that while results based on the volume-averaged models are reasonably close to current predictions for $\varepsilon \le 0.7$ , the discrepancy between the two becomes notable for higher porosities. While existing models rely exclusively on porosity and thermal conductivity ratio, our newly proposed correlations show the effects of Reynolds number on the heat split mechanism for high porosities. On the other hand, the Prandtl number, at least for the range of parameters studies here, is found to be less influential on the boundary heat split mechanism.     

Probing the origins of neutrino mass with supernova data

We study type II supernova signatures of neutrino mass generation via symmetry breaking at a scale in the range from keV to MeV. The scalar responsible for symmetry breaking is thermalized in the supernova core and restores the symmetry. The neutrinos from scalar decays have about half the average energy of thermal neutrinos. The Bose-Einstein distribution of the scalars can be established with a megaton water Cerenkov detector. The discovery of the bimodal neutrino flux is, however, well within the reach of the Super-Kamiokande detector, without a detailed knowledge of the supernova parameters.     

Turbulent heat transfer and nanofluid flow in an annular cylinder with sudden reduction

Journal of Thermal Analysis and Calorimetry - In this study, catalyst formation [Pb(H2O)6][ATZ]·H2O (ATZ?=?azo tetrazolium anion) was successfully synthesized originally;...     

On the calculation of extended max and min operations between convex fuzzy sets of the real line

In this paper we will identify the sets of so-called sub- and pseudo-highest intersection points of convex fuzzy sets of the real line and will explore their properties. Based on the properties of these sets, an algorithm for calculating extended max and min operations between two or more convex fuzzy sets of the real line with general membership functions, not necessarily continuous, is proposed.     

等通量壁多孔饱和圆管中粘性耗散对热发展强迫对流的影响

基于Brinkman流动模型，研究了等通量壁多孔饱和圆管中粘性耗散对强迫对流的影响，在热发展区域，进行了数值研究；在充分发展区域，进行了摄动分析并求得温度分布的表达式和Nusselt数。在发展区域，利用数值解得到的充分发展Nusselt数与渐近分析结果进行了比较，吻合很好。