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Highlights - Solidification of multilayer PCM within a fined triplex capsule is modelled. - A two-dimensional finite volume numerical technique is used for simulations. - Variation of liquid fraction values and PCM layers temperatures are reported. Abstract Efficient latent heat storage systems represent an important opportunity to improve the thermal performance and operational capability of industrial systems (e.g. solar thermal). In this paper, numerical study is performed to evaluate the heat transfer and solidification features, phase change period and temperature distribution of double-layer Phase Changing Materials (PCM) in a finned triplex tube. A two-dimensional finite volume numerical technique is used to solve the governing equations considering conduction and convection heat transfer mechanisms at a fixed Rayleigh number of 106. After comparing the results for single and double layer configurations, possible arrangements of two different PCMs are discussed in terms of different thicknesses of each PCM, fin sizes and different heat transfer fluid temperatures. Results are illustrated as the form of temperature, liquid fraction, stream function and velocity magnitude contours and their changes over the freezing time. Variation of liquid fraction values, average and minimum temperatures of layers in a double-layer PCM are reported for better insight into the heat transfer features of the latent heat thermal energy storage system to enable uniform discharging designs and balance the phase changing rate within the whole annulus.

Efficient cooling strategies are very important issues in thermal management of lithium-Ion battery system and these techniques should provide cost effective and energy saving solutions for temperature rise of the system during battery operation. A pseudo 2D electrochemical model has been used to investigate the electrochemical and thermal condition of commercial 18650 Lithium-Ion battery. This analysis was compared to previous experimental studies and results showed that the model predicts the temperature rise and thermal power generation very well. Results from the electro-thermal analysis were used to examine a cooling method. In this strategy, the cylindrical Li-ion cell is submersed within a thin cylindrical tank containing water-Al2O3 nanofluid. Air flow is employed to remove the heat from the system during discharge process. After testing this method for a single cell with various sizes of the secondary cylinder, critical and thermally dangerous arrangements of Li-ion cells were analyzed employing the new technique. 3D transient Computational Fluid Dynamics (CFD) simulations were used to see the effect of presence of the secondary cylinder on temperature rise. Results revealed that the new method reduces the maximum temperature of the cells efficiently.

Purpose - The purpose of this paper is to numerically investigate two dimensional steady state convective heat transfer in a differentially heated square cavity with constant temperatures and an inner rotating cylinder. The gap between the cylinder and the enclosure walls is filled with power law non-Newtonian fluid. Design/methodology/approach - Finite volume-based CFD software, Fluent (Ansys 15.0) is used to solve the governing equations. Attribution of the various flow parameters of fluid flow and heat transfer are investigated including Rayleigh number, Prandtl number, power law index, the cylinder radius and the angular rotational speed. Findings - Outcomes are reported in terms of isotherms, streamlines and average Nusselt number (Nu) of the heated wall for various considered here. Research limitations/implications - A detailed investigates is needed in the context of 3D flow. This will be a part of the future work. Practical implications - The effect of a rotating cylinder on heat transfer and fluid flow in a differentially heated rectangular enclosure filled with power law non-Newtonian fluid has practical importance in the process industry. Originality/value - The results of this study may be of some interest to the researchers of the field of chemical or process engineers.

Similarity solutions are carried out for flow of power law non-Newtonian fluid film on unsteady stretching surface subjected to constant heat flux. Free convection heat transfer induces thermal boundary layer within a semi-infinite layer of Boussinesq fluid. The nonlinear coupled partial differential equations (PDE) governing the flow and the boundary conditions are converted to a system of ordinary differential equations (ODE) using two-parameter groups. This technique reduces the number of independent variables by two, and finally the obtained ordinary differential equations are solved numerically for the temperature and velocity using the shooting method. The thermal and velocity boundary layers are studied by the means of Prandtl number and non-Newtonian power index plotted in curves.

Numerically investigation of free convection heat transfer in a differentially heated trapezoidal cavity filled with non-Newtonian Power-law fluid has been performed in this study. The left inclined surface is uniformly heated whereas the right inclined surface is maintained as uniformly cooled. The top and bottom surfaces are kept adiabatic with initially quiescent fluid inside the enclosure. Finite volume based commercial software FLUENT 14.5 is used to solve the governing equations. Dependency of various flow parameters of fluid flow and heat transfer is analyzed including Rayleigh number, Ra ranging from 10^5 to 10^7, Prandtl number, Pr of 100 to 10,000 and power index, n of 0.6 to 1.4. Outcomes have been reported in terms of isotherms, streamline, and local Nusselt number for various Ra, Pr, n and inclined angles. Grid sensitivity analysis is performed and numerically obtained results have been compared with those results available in the literature and found good agreement.

Numerical study is carried out using large eddy simulation to study the heat and toxic gases released from fires in real road tunnels. Due to disasters about tunnel fires in previous decade, it attracts increasing attention of researchers to create safe and reliable ventilation designs. In this research, a real tunnel with 10 MW fire (which approximately equals to the heat output speed of a burning bus) at the middle of tunnel is simulated using FDS (Fire Dynamic Simulator) for different ventilation velocities. Carbone monoxide concentration and temperature vertical profiles are shown for various locations to explore the flow field. It is found that, with the increase of the longitudinal ventilation velocity, the vertical profile gradients of CO concentration and smoke temperature were shown to be both reduced. However, a relatively large longitudinal ventilation velocity leads to a high similarity between the vertical profile of CO volume concentration and that of temperature rise.

In this study, natural convection heat transfer and buoyancy driven flows have been investigated in a right angled triangular enclosure. The heater located on the bottom wall while the inclined wall is colder and the remaining walls are maintained as adiabatic. Governing equations of natural convection are solved through the finite volume approach, in which buoyancy is modeled via the Boussinesq approximation. Effects of different parameters such as Rayleigh number, aspect ratio, prantdl number and heater location are considered. Results show that heat transfer increases when the heater is moved toward the right corner of the enclosure. It is also revealed that increasing the Rayleigh number, increases the strength of free convection regime and consequently increases the value of heat transfer rate. Moreover, larger aspect ratio enclosure has larger Nusselt number value. In order to have better insight, streamline and isotherms are shown.

Unsteady numerical simulation of Rayleigh Benard convection heat transfer from a 2D channel is performed. The oscillatory behavior is attributed to recirculation of ascending and descending flows towards the core of the channel producing organized rolled motions. Variation of the parameters such as Reynolds number, channel outlet flow area and inclination of the channel are considered. Increasing Reynolds number (for a fixed Rayleigh number), delays the generation of vortices. The reduction in the outflow area leads to the later and the less vortex generation. As the time progresses, more vortices are generated, but the reinforced mean velocity does not let the eddies to enter the core of the channel. Therefore, they attach to the wall and reduce the heat transfer area. The inclination of the channel (both positive and negative) induces the generated vortices to get closer to each other and make an enlarged vortex.