g. a. sheikhzadeh

In order to improve the thermal management system for cooling an electric vehicle battery pack, the thermal performance of the battery pack in two states of charge and discharge in different working conditions by using a copper sheath around the batteries and a copper sheath, as well as a stair channel on top of the battery pack and using of nanofluid as cooling fluid, has been studied using numerical simulation. The thermal model for the battery pack with 71 cylindrical lithium-ion batteries, model 18650, has been investigated. To develop this model, the thermal behavior of the battery set has been studied and the effect of variables such as electric current rate on both charge and discharge processes, fluid flow rate, addition of copper oxide nanoparticles to water-based fluid, change of contact surface between neighboring batteries and creation The wave channel for the batteries has been investigated. Numerical simulation results confirm the useful effect of the cooling system. The simulation results show that increasing the electric current rate increases the temperature and decreases the uniformity of temperature distribution in the battery pack. For this purpose, some changes have been made to improve the thermal performance of the battery. Increasing the volume percentage of nanoparticles causes a decrease in the maximum temperature and temperature difference in the battery assembly and leads to an improvement in the thermal performance of the cooling system. Also, increasing the fluid flow rate reduces the maximum temperature and improves the temperature uniformity in the battery pack. With increasing coolant inlet flow rate, 7.7% and 12.5% decrease in maximum temperature and temperature difference in the charge discharge process are observed in the battery pack, respectively. Finally, increasing the contact surface between the batteries and the wave channel from 37 degrees to 57 degrees can reduce the temperature difference and maximum temperature in the battery set by 5.2 and 52.3 percent, respectively, but the temperature uniformity in the set has an adverse effect.

Microchannel heat sink has been employed and as a part of electronic equipment extensively investigated. In this investigation, heat transfer and fluid flow features of laminar flow of water in a manifold microchannel heat sink (MMHS) was numerically simulated. Selected heat flux was 100 W/m^2 and water was as working fluid. The effect of length of inlet/outlet ratio (λ=Linlet/Loutlet), the height of microchannel (Hch), and width of the microchannel (Wch) at Reynolds number (Re) range from 20 to 100 as independent parameters on the fluid flow and heat transfer features were examined. Obtained results demonstrate that in MMHS, the impinging jet on the bottom channel surface, inhibits the growth of hydrodynamic and thermal boundary layers, resulting in an enhanced heat transfer rate. Also, by increasing Re and keeping the geometric parameters constant, the heat transfer rate increases. Based on the present investigation, for low Re, it is better to choose a λ=Linlet/Loutlet >1 and for high Re, choose a λ<1. For low Re, maximum of performance evaluation criterion (PECmax) is obtained at Hch=300µm, and for high Re, PECmax is obtained at Hch=240µm. for Re=20 to 100, the maximum of PECmax is 1.765 and obtained at Re=100 and Hch=240µm.

Lattice Boltzmann method is one of computational fluid dynamic subdivisions. Despite complicated mathematics involved in its background, end simple relations dominate on it; so in comparison to the conventional computational fluid dynamic methods, simpler computer programs are needed. Due to its characteristics for parallel programming, this method is considered efficient for the simulation of complex geometry flows, in which a large amount of computational memories is needed. Because of the curved boundaries in the complex geometries, detecting the proper curved boundary condition is unavoidable for the lattice Boltzmann method. For this purpose, more works have been done, and different curved boundary conditions have been proposed. At the present work, first, some curved boundary conditions have been reviewed; then a simplified curved boundary condition is proposed. A computer program based on the lattice Boltzmann method, in FORTRAN language, has been prepared; in this program, the boundary condition along with some others applied on it is proposed. To verify the accuracy and correctness of the proposed boundary condition, 2D cavity flow has been simulated and compared to the available numerical results. Adaptation of the achieved results with those of previous researchers verifies the prepared program correctness. Also, two fluid flows have been simulated, a flow around a stationary cylinder in a 2D channel and one between two stationary and moving cylinders. The results of simulations with the proposed boundary condition, along with the previous boundary conditions, have been compared to the available results. Comparisons demonstrate that solutions with proper accuracy could be obtained by the proposed boundary condition.

In this paper, the presented correlations in scientific literature for friction factor of turbulent flow in the base fluid and nanofluid has been analyzed statistically. In order to perform the statistical analysis and select the best probability distribution function for the friction factor, from 48 probability distribution functions and 3 statistic of Kolmogorov-Smirnov, Anderson-Darling and chi squared has been used. The results show that, based on all three statistics, the probability distribution function of the friction factor in the base fluid and nanofluid is the Johnson SB probability distribution function. Furthermore, it was observed that the probability distribution function of the friction factor of the base fluid and nanofluid is wider than the normal distribution function. On the other side, the probability distribution function of Johnson SB has a right skewness.