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| 1 | A Multiple-Relaxation-Time Lattice Boltzmann Model for Natural Convection in a Hydrodynamically and Thermally Anisotropic Porous Medium under Local Thermal Non-Equilibrium Conditions显示文摘To investigate the natural convective process in a hydrodynamically and thermally anisotropic porous medium at the representative elementary volume(REV)scale,the present work presented a multiplerelaxation-time lattice Boltzmann method(MRT-LBM)based on the assumption of local thermal non-equilibrium conditions(LTNE).Three sets of distribution function were used to solve the coupled momentum and heat transfer equations.One set was used to compute the flow field based on the generalized non-Darcy model;the other two sets were used to solve the temperature fields of fluid and solid under the LTNE.To describe the anisotropy of flow field of the porous media,a permeability tensor and a Forchheimer coefficient tensor were introduced into the model.Additionally,a heat conductivity tensor and a special relaxation matrix with some off-diagonal elements were selected for the thermal anisotropy.Furthermore,by selecting an appropriate equilibrium moments and discrete source terms accounting for the local thermal non-equilibrium effect,as well as choosing an off-diagonal relaxation matrix with some specific elements,the presented model can recover the exact governing equations for natural convection under LTNE with anisotropic permeability and thermal conductivity with no deviation terms through the Chapman-Enskog procedure.Finally,the proposed model was adopted to simulate several benchmark problems.Good agreements with results in the available literatures can be achieved,which indicate the wide practicability and the good accuracy of the present model. | YANG Bo WU Wei LI Maodong ZHAI Wei | 2020 | Journal of Thermal Science2020，29，3： | 3 |
| 2 | Design and Operational Strategy Research for Temperature Control Systems of Isothermal Compressed Air Energy Storage Power Plants显示文摘Energy storage technology is critical for intelligent power grids. It has great significance for the large-scale integration of new energy sources into the power grid and the transition of the energy structure. Based on the existing technology of isothermal compressed air energy storage, this paper presents a design scheme of isothermal compressed air energy storage power station, which uses liquid to compress air, hydraulic piston to transfer potential energy, hydraulic turbine to generate electricity at constant pressure, and liquid occupancy to store the gas at constant pressure. Then the technical features and control strategies of its internal temperature control subsystem are studied, and the mathematical model is constructed. A hierarchical relay operation is put forward to address the actual construction and operational requirements of compressed air energy storage power plants. Finally, through physical platform experiments and MATLAB simulation, the feasibility of the design is validated. | FU Hao JIANG Tong CUI Yan LI Bin | 2019 | Journal of Thermal Science2019，28，2： | 2 |
| 3 | Simulation and Experimental Study on Thermal Conductivity of Nano-Granule Porous Material Based on Lattice-Boltzmann Method显示文摘Nano-porous materials have excellent thermal insulation performance,whose microstructure and physical properties,however,have great influence on the thermal conductivity.To accurately describe the stochastic phase distribution,a random internal morphology and structure generation-growth method,called the quartet structure generation set(QSGS),has been proposed in the present paper.The model was then imported into lattice Boltzmann algorithm as a fully resolved geometry and used to investigate the effects on heat transfer at the nanoscale.Furthermore,a three-dimensional Lattice Boltzmann method(LBM)D3Q15 was adopted to predict the nano-granule porous material effective thermal conductivity.This ideal method provided a significant advantage over similar porous media methods by directly controlling and adjusting of granule characteristics such as granule size,porosity and pore size distributions and studying their influence directly on thermal conductivity.To verify the accuracy of the proposed model,some experiments based on guarded hot plate meter(GHPM)were conducted.The results indicated that the simulation results agreed well with the experimental data and references values,which illustrated that this method was reliable to generate the microstructure of nano-granule.What’s more,the effects of pressure,core distribution probability,cd and density were investigated.There existed an optimal density(about 120 kg·m^(-3))making the effective thermal conductivity being minimum and an optimal core distribution probability about cd=0.1 making the uniformity being the best.In addition,the present approach is applicable in dealing with other porous materials as well. | KAN Ankang MAO Shang WANG Ning SHI Bingling | 2021 | Journal of Thermal Science2021，30，1： | 2 |
| 4 | Combustion Wave Propagation of a Modular Porous Burner with Annular Heat Recirculation显示文摘A numerical investigation of the different arrangements of porous media in a combustor with annular heat recirculation is conducted.The effect of annular heat recirculation and porous block arrangement on the characteristics of combustion wave propagation is numerically studied.Results show that power input,heat capacity of porous matrix,arrangement of porous blocks,and annular heat recirculation are major factors that influence the propagation of combustion wave.The overall temperature of ceramic porous burner is higher than that of ceramic-metal type burner due to the lower heat storage capacity of the former,especially for the temperature downstream.The flame temperature is higher upstream and lower downstream with metal foams in the annulus than that without metal foams.The flame temperature of uniformity type burner is more uniform than that of gradually-varied and modular type burners.The flame front moves more slowly with metal foams in the annulus than that without metal foams due to the better preheating effect of metal foams.The flame position moves downstream,and the flame temperature gradually decreases and is eventually extinguished due to the low preheating temperature. | SONG Fuqiang WEN Zhi FANG Yuan WANG Enyu LIU Xunliang | 2020 | Journal of Thermal Science2020，29，1： | 2 |
| 5 | Analysis of Heat and Mass Transfer for a Single-Planar-Anode-Supported Solid Oxide Fuel Cell Considering Internal Reforming显示文摘The temperature uniformity and component concentration distributions in solid oxide fuel cells during operating processes can influence the cell electrochemical and thermal characteristics.A three-dimensional thermal-fluid numerical model including electrochemical reactions and water-gas-shift(WGS)reaction for a single channel solid oxide fuel cell was developed to study the steady-state characteristics,which include distributions of the temperature(T),temperature gradient((35)T/(35)x),and fuel utilization.It was shown that the maximum temperature(Tmax)changed with operating voltage and the maximum temperature gradient(((35)T/(35)x)max)occurred at the inlet of the channel of a solid oxide fuel cell by simulation.Moreover,the natural convection condition had a great influence on T and(35)T/(35)x.The thermal stress generated by temperature differences was the key parameter and increasing the convection heat-transfer coefficient can greatly reduce the thermal stress.In addition,the results also showed that there were lower temperature gradients and lower current density at high working voltage;therefore,choosing the proper operating voltage can obtain better cell performance. | ZHANG Zhuqian WANG Yulei BA Liming | 2020 | Journal of Thermal Science2020，29，3： | 2 |
| 6 | MWCNTs/SWCNTs Nanofluid Thin Film Flow over a Nonlinear Extending Disc: OHAM Solution显示文摘The aim of this research is the improvement towards the consumption of energy in the field of engineering and industry. The efforts have been paid to the enhancement of heat transmission and cooling process through a nanofluid coating of a nonlinear stretching disc. The combination of Water(H2 O) and multiple walled carbon nanotubes(MWCNT)/single walled carbon nanotubes(SWCNT) have been used as a nanofluid. The spreading of a thin nano-layer with variable thickness over a nonlinear and radially stretching surface has been considered. The estimated results of the problem have been accomplished using the Optimal Homotopy Analysis Method(OHAM). The residual errors of the OHAM method have been shown physically and numerically. The important physical parameters of skin friction and Nusselt number have been calculated and discussed. The other embedding parameters like generalized magnetic parameter, Prantl number, nanofluid volume fraction and Eckert number have been intended and discussed. The obtained results have been compared with the Numerical(ND-Solve) method for both sorts of CNTs. The closed agreement of both methods has been achieved. | GOHAR TAZA Gul WARIS Khan MUHAMMAD Shuaib MUHAMMAD Altaf Khan EBENEZER Bonyah | 2019 | Journal of Thermal Science2019，28，1： | 1 |
| 7 | Axially Oriented Structured Porous Layers for Heat Transfer Enhancement in a Solar Receiver Tube显示文摘The present work reports a numerical investigation of heat transfer and pressure drop characteristics in a solar receiver tube with different shaped porous media for laminar and low Reynolds number turbulent flow regimes.Numerical simulations have been performed with finite volume-based code ANSYS(v-2017)for different shapes of porous layers axially oriented in the tube.The plain-shaped porous medium fitted up to 50%of the tube shows better performance than other-shaped porous layers.Simulations have also been performed for axially oriented structured porous media with different sizes.Axially oriented structured porous medium develops a lateral flow disturbance enhancing the intermixing of the liquid and porous medium at their interface.Structured porous medium with a 3-crest configuration shows the best heat transfer performance among all the shapes of porous media.It offers a maximum of 148%heat transfer enhancement compared to a half-filled plain porous layer,whereas it reports a maximum of 564%enhancement compared to the flow without a porous layer.The lateral flow tendency or the swirling effect helps better heat transfer performance in the axially oriented structured porous media.Performance evaluation criterion(PEC)in all types of porous media is more in the transitional flow regime than in the laminar and turbulent flow regimes.For the same operating conditions,the maximum value of the PEC in the present work is 120%higher than the maximum value of PEC for other-shaped porous media reported in the literature.Correlations for Nusselt number have been developed for both laminar and turbulent flow regimes for three crests shaped porous medium. | DAS Shefali VERMA Neha PATHAK Manabendra BHATTACHARYYA Suvanjan | 2021 | Journal of Thermal Science2021，30，5： | 0 |
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