密排六方颗粒填充床内对流换热的模拟研究
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摘要
针对颗粒堆积结构对填充床内对流换热的影响,利用ICEM和FLUENT等流体力学软件对密排六方堆积结构进行建模,采用RNG k-ε湍流模型以及等比例缩放的壁面函数对结构内转捩流和湍流进行数值模拟,使用CFD-Post后处理软件计算分析结构内流体的压力降、流动阻力系数和综合换热系数,并与无序堆积结构和具有同样孔隙率的面心立方堆积结构进行比较。结果表明,相比于面心立方堆积结构和无序堆积结构,密排六方堆积结构内流体的压降明显增加;在孔隙雷诺数小于1500时,密排六方堆积结构内流体的阻力系数小于面心立方堆积结构及无序堆积结构内流体的阻力系数;密排六方堆积结构的颗粒壁面努塞尔数明显大于面心立方堆积结构及无序堆积结构的颗粒壁面努塞尔数,该堆积结构具有更好的综合换热效率。
To investigate the influence of particle stacking structure on the convective heat transfer in the packed bed, modeling of hexagonal close-packed structure was carried out by means of such fluid mechanics software as ICEM and FLUENT. The RNG k-ε turbulence model and the scaled wall function were applied to numerically study the transition flow and turbulent flow in the structure. CFD-Post post-processing software was used to calculate the pressure drop of fluid,resistance coefficient and the integrated heat transfer coefficient, which were then compared with those of disordered stacking structure and face-centered cubic packing structure of the same porosity. The results show that the pressure drop of fluid in the dense hexagonal packing structure increases obviously compared with the face-centered cubic packing structure and the disordered packing structure. When the pore Reynolds number is less than 1500, the fluid resistance coefficient in the hexagonal close-packed structure is smaller than that in the face-centered cubic packing structure and disordered packing structure. The Nusselt number of particle walls in the densely arranged hexagonal packing structure is obviously higher than that in the face-centered cubic packing structure and disordered packing structure, which has higher comprehensive heat transfer efficiency.
To investigate the influence of particle stacking structure on the convective heat transfer in the packed bed, modeling of hexagonal close-packed structure was carried out by means of such fluid mechanics software as ICEM and FLUENT. The RNG k-ε turbulence model and the scaled wall function were applied to numerically study the transition flow and turbulent flow in the structure. CFD-Post post-processing software was used to calculate the pressure drop of fluid,resistance coefficient and the integrated heat transfer coefficient, which were then compared with those of disordered stacking structure and face-centered cubic packing structure of the same porosity. The results show that the pressure drop of fluid in the dense hexagonal packing structure increases obviously compared with the face-centered cubic packing structure and the disordered packing structure. When the pore Reynolds number is less than 1500, the fluid resistance coefficient in the hexagonal close-packed structure is smaller than that in the face-centered cubic packing structure and disordered packing structure. The Nusselt number of particle walls in the densely arranged hexagonal packing structure is obviously higher than that in the face-centered cubic packing structure and disordered packing structure, which has higher comprehensive heat transfer efficiency.
引文
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[2] Yang J,Wang Q W,Zeng M,et al.Computational study of forced convective heat transfer in structured packed beds with spherical or ellipsoidal particles[J].Chemical Engineering Science,2010,65(2):726-738.
[3] Liu Y,Wang J Y,Cheng Z L,et al.Experimental investigation of fluid flow and heat transfer in a randomly packed bed of sinter particles[J].International Journal of Heat and Mass Transfer,2016,99:589-598.
[4] Kuwahara F,Yamane T,Nakayama A.Large eddy simulation of turbulent flow in porous media[J].International Communications in Heat and Mass Tran-sfer,2006,33(4):411-418.
[5] Zhu Q B,Xuan Y M.Pore scale numerical simulation of heat transfer and flow in porous volumetric solar receivers[J].Applied Thermal Engineering,2017,120:150-159.
[6] Latour L L,Kleinberg R L,Mitra P P,et al.Pore-size distributions and tortuosity in heterogeneous porous media[J].Journal of Magnetic Resonance,1995,112(1):83-91.
[7] Bustos C I,Toledo P G.Pore-level modeling of gas and condensate flow in two- and three-dimensional pore networks:pore size distribution effects on the relative permeability of gas and condensate[J].Transport in Porous Media,2003,53(3):281-315.
[8] Wu P,Wang L ,Feng X,et al.Surface-particle-emulsion heat transfer model between fluidized bed and horizontal immersed tube[J].Journal of University of Science and Technology Beijing,2002,9(2):99-103.
[9] Yang X H,Lu T J,Kim T.Effective thermal conductivity modelling for closed-cell porous media with analytical shape factors[J].Transport in Porous Media,2013,100(2):211-224.
[10] Guo B Y,Yu A B,Wright B,et al.Simulation of turbulent flow in a packed bed[J].Chemical Engineering and Technology,2006,29(5):596-603.
[11] Yang J,Bu S S,Dong Q T,et al.Experimental study of flow transitions in random packed beds with low tube to particle diameter ratios[J].Experimental Thermal and Fluid Science,2015,66:117-126.
[12] Baker M J,Tabor G R.Computational analysis of transitional air flow through packed columns of spheres using the finite volume technique[J].Computers and Chemical Engineering,2010,34(6):878-885.
[13] Ferng Y M,Lin K Y.CFD investigation of thermal-hydraulic characteristics in a PBR core using different contact treatments between pebbles[J].Annals of Nuclear Energy,2014,72:156-165.
[14] Yang J,Zhou M,Li S Y,et al.Three-dimensional numerical analysis of turbulent flow in porous media formed by periodic arrays of cubic,spherical,or ellipsoidal particles[J].Journal of Fluid Engineering,2014,136(1):1-10.
[15] Yang J,Wu J Q,Zhou L,et al.Computational study of fluid flow and heat transfer in composite packed beds of spheres with low tube to particle diameter ratio[J].Nuclear Engineering and Design,2016,300:85-96.
[16] Guo Z H,Sun Z N,Zhang N,et al.CFD analysis of fluid flow and particle-to-fluid heat transfer in packed bed with radial layered configuration[J].Chemical Engineering Science,2019,197:357-370.
[17] Hu Y X,Yang J,Wang J Y,et al.Investigation of hydrodynamic and heat transfer performances in grille-sphere composite pebble beds with DEM-CFD-Taguchi method[J].Energy,2018,155:909-920.
[18] Li S Y,Zhou L,Yang J,et al.Numerical simulation of flow and heat transfer in structured packed beds with smooth or dimpled spheres at low channel to particle diameter ratio[J].Energies.2018,11(4):1-15.
[19] Hu Y X,Wang J Y,Yang J,et al.Experimental study of forced convective heat transfer in grille-particle composite packed beds[J].International Journal of Heat and Mass Transfer,2019,129:103-112.
[20] Suabsakul G.Numerical simulation of micro-channel heat sink with dimpled surfaces[J].American Journal of Applied Sciences.2012,9(3):399-404.
[21] Wang J Y,Yang J,Cheng Z L,et al.Experimental and numerical study on pressure drop and heat transfer performance of grille-sphere composite structured packed bed[J].Applied Energy,2017,227:719-730.
[22] Bu S S,Yang J,Li S Y,et al.Numerical simulation of convective heat transfer in structured packed beds of particles with different particle contact treatment methods[C]//Proceedings of the ASME Summer Heat Transfer Conference,2012:849-857.
[23] Alkhalaf A,Refaey H A,Al-Durobi N,et al.Influence of contact point treatment on the cross flowmixing in a simple cubic packed bed:CFD simulation and experimental validation[J].Granular Matter.2018,20(2):22-35.
[24] Getachew D,Minkowycz W J,Lage J L.A modified form of the κ-ε model for turbulent flows of an incompressible fluid in porous media[J].International Journal of Heat and Mass Transfer,2000,43(16):2909-2915.
[25] Ergun S.Fluid flow through packed columns[J].Chemical Engineering Progress,1952,48(2):89-94.
[26] S?zen M,Kuzay T M.Enhanced heat transfer in round tubes with porous inserts[J].International Journal of Heat and Fluid Flow,1996,17(2):124-129.
[27] Wakao N,Funazkri T.Effect of fluid dispersion coefficients on particle-to-fluid mass transfer coefficients in packed beds:correlation of sherwood numbers[J].Chemical Engineering Science,1979,33(10):1375-1384.
[28] Srinivasan R,Raghunandan B N.Experiments on thermal response of low aspect ratio packed beds at high Reynolds numbers with varying inflow temperature[J].Experimental Thermal and Fluid Science,2013,44(1):323-333.
[29] Toit C G D.Radial variation in porosity in annular packed beds[J].Nuclear Engineering and Design,2008,238(11):3073-3079.
[30] Bu S S,Yang J,Dong Q T,et al.Experimental study of flow transitions in structured packed beds of spheres with electrochemical technique[J].Experimental Thermal and Fluid Science,2015,60:106-114.