Numerical Study of Flow and Heat Transfer in Novel Structure Packed Beds

2009 ◽  
Author(s):  
Jian Yang ◽  
Qiuwang Wang ◽  
Min Zeng
Keyword(s):  
Heat Transfer ◽  
Particle Shape ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Particle Model ◽  
Physical Parameters ◽  
Packed Beds ◽  
Transfer Performance ◽  
Flow And Heat Transfer ◽  
Better Than

A forced convection heat transfer inside micro pores of structure packed beds with spherical or ellipsoidal particles are numerically studied in this paper. Three-dimensional Navier-Stokes equations and RNG k-ε turbulence model with scalable wall function are adopted for present computations. The effects of packing form and particle shape are carefully studied and the flow and heat transfer performances in uniform and nonuniform packed beds are also compared in detail. The macroscopic hydrodynamic and heat transfer results are obtained from micro pore cells by using integrating method. The results show that, with the same physical parameters, the pressure drops in structure packed beds are much lower than those in randomly packed beds while the overall heat transfer efficiencies (except SC packing) are much higher. The traditional correlations of flow and heat transfer extracted from randomly packings are unavailable for structured packings, and some modified correlations are obtained. Furthermore, it finds that, with the same particle shape (sphere), the overall heat transfer performance of SC packing is better than that of BCC packing. With the same packing form (BCC), the overall heat transfer performance of spherical particle model is better than that of ellipsoidal particle model and with the same particle shape and packing form (BCC packing with sphere), the overall heat transfer performance of uniform packing is better than that of non-uniform packing.

scholarly journals Numerical Study on Heat Transfer Performance in Packed Bed

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 414 ◽  
Author(s):  
Shicheng Wang ◽  
Chenyi Xu ◽  
Wei Liu ◽  
Zhichun Liu
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Transfer Process ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Continuous Phase ◽  
Heat Transfer Process ◽  
Packed Beds ◽  
Transfer Performance ◽  
Entransy Dissipation

Packed beds are widely used in industries and it is of great significance to enhance the heat transfer between gas and solid states inside the bed. In this paper, numerical simulation method is adopted to investigate the heat transfer principle in the bed at particle scale, and to develop the direct enhanced heat transfer methods in packed beds. The gas is treated as continuous phase and solved by Computational Fluid Dynamics (CFD), while the particles are treated as discrete phase and solved by the Discrete Element Method (DEM); taking entransy dissipation to evaluate the heat transfer process. Considering the overall performance and entransy dissipation, the results show that, compared with the uniform particle size distribution, radial distribution of multiparticle size can effectively improve the heat transfer performance because it optimizes the velocity and temperature field, reduces the equivalent thermal resistance of convection heat transfer process, and the temperature of outlet gas increases significantly, which indicates the heat quality of the gas has been greatly improved. The increase in distribution thickness obviously enhances heat transfer performance without reducing the equivalent thermal resistance in the bed. The result is of great importance for guiding practical engineering applications.

A Numerical Study of the Flow and Heat Transfer in the Pin Fin-Dimple Channels With Various Dimple Depths

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Yu Rao ◽  
Yamin Xu ◽  
Chaoyi Wan
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat Transfer ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Transfer Performance ◽  
Number Range ◽  
Flow Friction ◽  
Pin Fin ◽  
Flow And Heat Transfer

A numerical study was conducted to investigate the effects of dimple depth on the flow and heat transfer characteristics in a pin fin-dimple channel, where dimples are located spanwisely between the pin fins. The study aimed at promoting the understanding of the underlying convective heat transfer mechanisms in the pin fin-dimple channels and improving the cooling design for the gas turbine components. The flow structure, friction factor, and heat transfer performance of the pin fin-dimple channels with various dimple depths have been obtained and compared with each other for the Reynolds number range of 8200–80,800. The study showed that, compared to the pin fin channel, the pin fin-dimple channels have further improved convective heat transfer performance, and the pin fin-dimple channel with deeper dimples shows relatively higher Nusselt number values. The study still showed a dimple depth-dependent flow friction performance for the pin fin-dimple channels compared to the pin fin channel, and the pin fin-dimple channel with shallower dimples shows relatively lower friction factors over the studied Reynolds number range. Furthermore, the computations showed the detailed characteristics in the distribution of the velocity and turbulence level in the flow, which revealed the underlying mechanisms for the heat transfer enhancement and flow friction reduction phenomenon in the pin fin-dimple channels.

Numerical Modeling of Turbulent Flow and Heat Transfer Within a Bayonet Tube

2007 ◽  
Author(s):  
Feng Sun ◽  
G.-X. Wang
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Experimental Result ◽  
Working Fluid ◽  
Transfer Performance ◽  
Flow And Heat Transfer ◽  
Air Jet ◽  
The Impact

This paper presents a numerical study of turbulent flow and heat transfer in a bayonet tube under steady state. First, various turbulent models and wall treatment methods have been tested and validated against the experimental result from a turbulent air jet. The proper combination of turbulent model and wall treatment is then recommended for the turbulent flow within a bayonet tube. The study focuses on the heat transfer performance at the interface of working fluid and the outer tube wall under different Reynolds numbers. Various geometry parameters are considered in this work and the impact of geometry on the heat transfer performance is investigated. Results indicate that the heat transfer at the bottom of the bayonet tube is enhanced compared with that at the straight part. At low Re (< 8000), the maximum Nu occurs at the stagnation point, while the position of the maximum Nu moves away from the stagnant point as Re exceeds 8000. The results are believed to be helpful for the optimized design of a bayonet tube with fully turbulent flows.

A Numerical Study of the Flow and Heat Transfer Characteristics of Outward Convex Corrugated Tubes With Twisted-Tape Insert

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Longbin Yang ◽  
Huaizhi Han ◽  
Yanjun Li ◽  
Xiaoming Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Swirling Flow ◽  
Numerical Study ◽  
Twisted Tape ◽  
Transfer Performance ◽  
Heat Transfer Characteristics ◽  
Corrugated Tube ◽  
Flow And Heat Transfer ◽  
Flow Heat

This work presents a mathematical model for simulating the swirling flow in an outward convex corrugated tube with twisted-tape insert (CT). The synergistic effect on the flow, heat transfer, and friction loss behaviors between the surface-based and fluid-based enhancements is numerically investigated. Renormalized group (RNG) k-ε turbulence model applied in our paper is verified by comparing with experimental results investigated by Manglik and Bergles. Comparisons of the CT and smooth tube with twisted-tape insert (ST) plots are confirmed to investigate the performance differences between them. When comparing the performance of the CT against the ST, the maximum ratio of Nusselt number (Nuc/Nus), ratio of friction factor (f/fs), and overall heat transfer performance (η) values realized in the CT are 1.36, 1.53, and 1.15 times higher, respectively, than the maximum values for those same variables in the ST.

scholarly journals Numerical Simulation of Flow and Heat Transfer in Structured Packed Beds with Smooth or Dimpled Spheres at Low Channel to Particle Diameter Ratio

Energies ◽  
2018 ◽  
Vol 11 (4) ◽  
pp. 937 ◽  
Author(s):  
Shiyang Li ◽  
Lang Zhou ◽  
Jian Yang ◽  
Qiuwang Wang
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Heat Transfer Performance ◽  
Particle Diameter ◽  
Packed Bed ◽  
Packed Beds ◽  
Transfer Performance ◽  
Heat Transfer Characteristics ◽  
Flow And Heat Transfer

Packed beds are widely used in catalytic reactors or nuclear reactors. Reducing the pressure drop and improving the heat transfer performance of a packed bed is a common research aim. The dimpled structure has a complex influence on the flow and heat transfer characteristics. In the present study, the flow and heat transfer characteristics in structured packed beds with smooth or dimpled spheres are numerically investigated, where two different low channel to particle diameter ratios (N = 1.00 and N = 1.15) are considered. The pressure drop and the Nusselt number are obtained. The results show that, for N = 1.00, compared with the structured packed bed with smooth spheres, the structured packed bed with dimpled spheres has a lower pressure drop and little higher Nusselt number at 1500 < ReH < 14,000, exhibiting an improved overall heat transfer performance. However, for N = 1.15, the structured packed bed with dimpled spheres shows a much higher pressure drop, which dominantly affects the overall heat transfer performance, causing it to be weaker. Comparing the different channel to particle diameter ratios, we find that different configurations can result in: (i) completely different drag reduction effect; and (ii) relatively less influence on heat transfer enhancement.

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