Computational study of fluid flow and heat transfer in composite packed beds of spheres with low tube to particle diameter ratio

A finite-volume-based computational study of transient laminar flow and heat transfer (neglecting natural convection) within a lid-driven square cavity due to an oscillating thin fin is presented. The lid moves from left to right and a thin fin positioned perpendicular to the right stationary wall oscillates in the horizontal direction. The length of the fin varies sinusoidally with its mean length and amplitude equal to 10 and 5 percent of the side of the cavity, respectively. Two Reynolds numbers of 100 and 1000 for a Pr=1 fluid were considered. For a given convection time scale tconv, fin’s oscillation periods (τ) were selected in order to cover both slow τ/tconv>1 and fast τ/tconv<1 oscillation regimes. This corresponded to a Strouhal number range of 0.005 to 0.5. The number of the cycles needed to reach the periodic state for the flow and thermal fields increases as τ/tconv decreases for both Re numbers with the thermal field attaining the periodic state later than the velocity field. The key feature of the transient evolution of the fluid flow for the case with Re=1000 with slow oscillation is the creation, lateral motion and subsequent wall impingement of a CCW rotating vortex within the lower half of the cavity. This CCW rotating vortex that has a lifetime of about 1.5τ brings about marked changes to the temperature field within a cycle. The dimensionless time for the mean Nusselt numbers to reach their maximum or minimum is independent of the frequency of the fin’s oscillation and is dependent on the distance between the oscillating fin and the respective wall, and the direction of the primary CW rotating vortex. The phase lag angle between the oscillation of the fin and the mean Nusselt number on the four walls increases as the distance between the fin and the respective wall increases.

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Heat Transfer in Packed Beds of Low Tube/Particle Diameter Ratio

ACS Symposium Series - Chemical Reaction Engineering—Houston ◽

10.1021/bk-1978-0065.ch020 ◽

1978 ◽

pp. 238-253 ◽

Cited By ~ 30

Author(s):

A. G. DIXON ◽

W. R. PATERSON ◽

D. L. CRESSWELL

Keyword(s):

Heat Transfer ◽

Particle Diameter ◽

Diameter Ratio ◽

Packed Beds

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Fluid Flow and Heat Transfer in a Lid-Driven Cavity Due to an Oscillatory Thin Fin: Transient Behavior

Volume 2, Parts A and B ◽

10.1115/ht-fed2004-56177 ◽

2004 ◽

Cited By ~ 1

Author(s):

Xundan Shi ◽

J. M. Khodadadi

Keyword(s):

Heat Transfer ◽

Fluid Flow ◽

Computational Study ◽

Transient Behavior ◽

Phase Lag ◽

Dimensionless Time ◽

Number Range ◽

Flow And Heat Transfer ◽

Periodic State ◽

The Mean

A finite-volume-based computational study of transient laminar flow and heat transfer (neglecting natural convection) within a lid-driven square cavity due to an oscillating thin fin is presented. The lid moves from left to right and a thin fin positioned perpendicular to the right stationary wall oscillates in the horizontal direction. The length of the fin varies sinusoidally with its mean length and amplitude equal to 10 and 5 percent of the side of the cavity, respectively. Two Reynolds numbers of 100 and 1000 with a Pr = 1 fluid were considered. For a given convection time scale (tconv), fin’s oscillation periods (τ) were selected in order to cover both slow (τ/tconv>1) and fast (τ/tconv<1) oscillation regimes. This corresponded to a Strouhal number range of 0.005 to 0.5. The number of the cycles needed to reach the periodic state for the flow and thermal fields increases as τ/tconv decreases for both Re numbers with the thermal field attaining the periodic state later than the velocity field. The key feature of the transient evolution of the fluid flow for the case with Re = 1000 with slow oscillation is the creation, lateral motion and subsequent wall impingement of a CCW rotating vortex within the lower half of the cavity. This CCW rotating vortex that has a lifetime of about 1.5τ brings about marked changes to the temperature field within a cycle. The dimensionless time for the mean Nusselt numbers to reach their maximum or minimum is independent of the frequency of the fin’s oscillation and dependent on the distance between the oscillating fin and the respective wall, and the direction of the primary CW rotating vortex. The phase lag angle between the oscillation of the fin and the mean Nusselt number on the four walls increases as the distance between the fin and the respective wall increases.

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

Energies ◽

10.3390/en11040937 ◽

2018 ◽

Vol 11 (4) ◽

pp. 937 ◽

Cited By ~ 3

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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