Numerical Modelling of Heat Transfer Systems

To cite this article: Mohammad Ghalambaz, Ali Doostanidezfuli, Hossein Zargartalebi & Ali J. Chamkha (2017) MHD phase change heat transfer in an inclined enclosure: Effect of a magnetic field and cavity inclination, Numerical Heat Transfer, Part A: Applications, 71:1, 91-109,

Analytical expressions for the Nusselt number at the inner and outer pipes, kept at unequal temperatures, for laminar forced convection through annuli including viscous dissipation have been obtained in the conduction limit. This article examines the dependence of the limiting Nusselt numbers on Brinkman number and the degree of asymmetry in inner and outer pipe temperatures. Further, the limiting temperature profile obtained when viscous dissipation is included serves the purpose of providing the downstream boundary condition needed in solving the elliptic form of conservation of thermal energy equation that arises when axial conduction is included

This paper presents the effects of aerodynamic drag reduction devices on a heavy truck-trailer. Aerodynamic analysis including the assessment of fuel economy for both basic and modified truck-trailer profile was carried out numerically by using ANSYS FLUENTsoftware. It was found that modifications to the basic truck-trailer reducedaerodynamic drag by 21 % and improved fuel savings up to 15 % without making any negative impact on its stability. The effect of protruded profile such as external rear view mirror on aerodynamics of truck-trailer was also analyzed

To able to employ nanofluids in engineering applications, it is essential to investigate heat transfer properties in addition to thermophysical characteristics. In this work, the convection heat transfer coefficient of graphene oxide-distilled water nanofluid along a circular copper tube having a constant heat flux at the outside surface has been investigated both numerically and experimentally under turbulent flow regime. While the nanofluid convection heat transfer and head loss of pressure have been evaluated in the experimental section, the tube wall surface temperature, the convection heat transfer coefficient and friction factor have been obtained by using finite volume method in the numerical part with a three-dimensional domain by assuming single-phase flow. Surface and fluid temperatures and pressure drop of the distilled water have been acquired and compared with the related output from the correlation. Besides, the variations of the tube surface temperatures and the convection heat transfer coefficients of the nanofluids have been examined as numerical and experimental comparisons. The contours of the temperatures, convection heat transfer coefficients and pressure distributions for fluids have been presented. The convection heat transfer performances of the nanofluids according to the different volumetric flow rates, concentrations and the heat flux values have been exhibited in this study. The heat transfer coefficient increment value for the nanofluid of 0.02 vol% concentration and with a flow rate of 1.5 l/min (Re = 5032) has been obtained as about 48% for 5073.244 W/m 2 (350 W) heat flux according to the distilled water.

The Normalized Variable Formulation (NVF) methodology of Leonard [1] provides the proper framework for the development and analysis of High-Resolution convection-diffusion schemes, which combine the accuracy of Higher-Order schemes, with the stability and boundedness of the first-order upwind scheme. However, in its current form the NVF methodology helps in deriving convective schemes for uniformly or nearly uniformly discretized spaces. To remove this shortcoming, a new Normalized Variable and Sapce Formulation methodology is developed (NVSF). In the newly developed technique, spatial parameters are introduced so as to extend the applicability of the NVF methodology to non-uniformly discretized domains. Furthermore, the required conditions for accuracy and boundedness of convective schemes on non-uniform grids are also derived. Several schemes formulated using NVF, are generalized to non-uniform grid using the suggested method. Both formulations are tested on non-uniform grids by solving two problems. Computational results show substantial improvement in accuracy when using the NVSF methodology with third order High-Resolution schemes.

In the present study, the effects of different types thermal bridges formed by beams for floor-wall junctions in reinforced concrete structures, with and without balconies , and the optimum configuration of the insulation layers to avoid heat loss were investigated as numerically. Both insulation between the walls and internal insulation was selected for floor-wall junctions and internal insulation was used for floor-wall junctions with balcony. Fluent package program was used to solve the temperature domain numerically. Results showed that high heat transfer rates were obtained in the region of thermal bridges for all building models. It was also obviously obtained that heat transfer rate decreased with making insulation on the beam surfaces.

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The liquid flow and conjugated heat transfer performance of single phase laminar flow in rectangular microchannels equipped with longitudinal vortex generators (LVGs) are numerically investigated. Deionized-water with temperature-dependent thermo-physical properties is employed to conduct the simulations. Three dimensional simulations are performed using an open-source flow solver based on finite volume approach and SIMPLEC algorithm. Five different configurations of the microchannel with different angles of attack of the LVGs are considered. Simulation results are compared with available experimental data and a deviation below 10% is achieved. The results show that there is a 2-25% increase in the Nusselt number for microchannels with LVGs, while the friction factor increased by 4-30%, for Reynolds number ranged from 100 to 1100. The overall performance of some specific configurations of the microchannels with LVGs is higher than that of the conventional smooth microchannels.

Electric drive mining trucks, which are of heavy loads and high efficiencies, are widely used for off-road applications such as large-scale open-pit metal mines, coal mines, and water conservancy constructions. Unlike on-road trucks, off-road mining trucks usually work with fixed routes and in the mode of full-load uphill and no-load downhill along a high slope. The recoverable potential energy accounts for more than one-third of the uphill driving work. If this part of the energy can be recovered and reused, the vehicle fuel consumption and CO₂ emission can be significantly reduced.
As most of China’s large open-pit mines are located in cold areas, the low temperature will aggravate the degradation mechanism of the batteries, resulting in the high cost of the mining dump truck with a battery energy storage system. Therefore, it is necessary to develop a new energy storage system with large capacity, high power, high efficiency, and low-temperature resistance.
This paper takes the high-capacity composite pressure energy storage systems as the research objects, analyzes the influence of layouts on the performance of energy storage systems, and puts forward the method of using the oil-circulating hydro-pneumatic energy storage system to recover the downhill potential energy of mining trucks through layout comparison study; The thermal process model of circulating hydro-pneumatic energy storage system is established, its thermal effect mechanism is explored, and an effective coupling heat dissipation method with low energy consumption is proposed; Then, the multi-objective nested optimization method based on the adaptive hybrid surrogate model is used to obtain the optimal structure of circulating hydro-pneumatic energy storage system under the corresponding optimal energy management strategy with less computation cost; Finally, through the real vehicle test of the electric mining truck and the bench test of its composite powertrain, it is verified that the optimal structure and energy management strategy of the system can effectively reduce the fuel consumption and CO₂ emission of the mining truck.
Firstly, based on the hydraulic and compressed air energy storage systems, four basic hydro-pneumatic energy storage layouts are established: open volume layout, open mass layout, closed volume layout, and closed mass layout. Taking energy density and minimum specific power as the evaluation indicators, the energy and power characteristics of four basic layouts are analyzed, and their vehicle applicability is evaluated. According to the demand for braking energy recovery and energy storage of mining trucks in cold areas, the circulating hydro-pneumatic energy storage system model is established. The analysis results show that the system has good power and energy characteristics at the same time, which provides a feasible method for energy recovery and utilization of large mining trucks in cold environments.
Aiming at the overheating problem of circulating hydro-pneumatic energy storage system during high-capacity and high-power energy recovery, the thermal process model of the energy storage system is established, the factors that lead to overheating are explored, and the coupling heat dissipation method is proposed. By combining the surplus cold potential in the downhill process and the surplus heat potential in the uphill process of the mining truck, the temperature potential coupling heat dissipation is realized in the way of low energy consumption. The calculation results show that the maximum temperature of hydraulic oil is reduced to 52.79℃, and 28% of heat can be released through the cooling system, which effectively solves the overheating problem in the energy storage process of circulating hydro-pneumatic energy storage system.
Aiming at the efficient energy recovery and utilization of the system in the uphill process of the mining truck, an energy management strategy of the circulating hydro-pneumatic energy storage system is proposed. Aiming at the minimum fuel consumption of the whole vehicle, the power distribution strategy of the composite powertrain is obtained based on the dynamic programming algorithm. Through the real vehicle test of the electric mining truck under its working conditions and the bench test of its composite powertrain, it is verified that the energy management strategy can effectively reduce the fuel consumption of the mining truck.
Finally, to further improve the energy density of the circulating hydro-pneumatic energy storage system, the nested optimization method based on the adaptive hybrid surrogate model is adopted by using the Pareto optimal solution set. And combining the contradictory objectives of energy density and energy storage efficiency into the global normalized optimization objective, the optimal structure of the circulating hydro-pneumatic energy storage is obtained with less computation cost, which provides a basis for the design and application of the energy storage system for mining trucks.

Important heat transfer parameters of aluminum foams of varying pore sizes are investigated through CT-scanning at 20 micron resolution. Small sub-samples from the resulting images are processed to generate feature-preserving, finite-volume meshes of high quality. All three foam samples exhibit similar volumetric porosity (in the range ~ 91-93%), and thereby a similar thermal conductivity.

... [77. CD Pérez-Segarra , C. Oliet , and A. Oliva , Thermal and Fluid Dynamic Simulation of Automotive Fin-and-Tube Heat Exchangers, Part 1: Mathematical Model , Heat Transfer Eng. , vol. 29 , pp. 484 – 494 , 2008 . [Taylor & Francis Online], [Web of Science ®] View all ...

This paper discusses a new boundary element computer program applicable to thermal diffusion. The nonlinear transient case is especially considered, and the solutions used to get an integral equation with boundary integrals only are pointed out. The numerical procedures used to disconnect space and time integrations and to take into account the nonlinearities on the domain and on the boundary

In the present study, the effects of different types thermal bridges formed by beams for floor-wall junctions in reinforced concrete structures, with and without balconies, and the optimum configuration of the insulation layers to avoid heat loss were investigated as numerically. Both insulation between the walls and internal insulation was selected for floor-wall junctions and internal insulation was used for floor-wall junctions with balcony. Fluent package program was used to solve the temperature domain numerically. Results showed that high heat transfer rates were obtained in the region of thermal bridges for all building models. It was also obviously obtained that heat transfer rate decreased with making insulation on the beam surfaces.