Solids Circulation in Turbulent Fluidized Beds and Heat Transfer to Immersed Tube Banks

1979 ◽  
Vol 101 (3) ◽  
pp. 391-396 ◽  
Author(s):  
F. W. Staub
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Flow Regime ◽  
Fluidized Beds ◽  
Flow Model ◽  
Flow Measurements ◽  
Turbulent Flow Regime ◽  
Gas Fluidized Beds ◽  
Tube Banks ◽  
Superficial Gas Velocity

In gas fluidized beds of large particles, a change in flow regime from bubbling flow to turbulent flow has been observed as the superficial gas velocity is increased. Solids flow and heat transfer models based on the bubbling flow regime are not generally adequate in the turbulent flow regime. A turbulent flow model is given here that is supported by limited solids flow measurements. A simplified model of the heat transfer to tube banks immersed in fluidized beds, that employs the solids flow model, is also given and is shown to be supported by data over a wide gas pressure and temperature range with particles in the 350μm to 2600μm size range.

Thermal Performance of Sensible Energy Storage Module Consisting of a Cementitious Matrix: The Effect of Operating Conditions

2020 ◽  
Author(s):  
Justin Caspar ◽  
Julio Bravo ◽  
Shuoyu Wang ◽  
Ahmed Abdulridha ◽  
Sudhakar Neti ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Energy Storage ◽  
Turbulent Flow ◽  
Flow Regime ◽  
Thermal Performance ◽  
Operating Conditions ◽  
Initial Time ◽  
Time Rate ◽  
Turbulent Flow Regime

Abstract The fluid flow and heat transfer inside a concrete thermal energy storage module is simulated for various heat transfer fluid flow rates and inlet temperatures. The storage performance of the module is characterized based on the volume-averaged temperature and normalized energy distribution through the block versus time. In the turbulent flow regime, induced mixing in the pipe strongly enhanced the performance of the module compared to the laminar regime. The block was able to fully charge and discharge in a turbulent flow regime, whereas that behavior was not present in the laminar flow regime. Varying the heat transfer temperature had an effect on the time rate of change of temperature as well as the charge times. As the thermal gradient increased, the initial time rate of temperature in the block increased as well as the charge time. Since the block has higher theoretical energy at a larger gradient, power over a longer duration is necessary to reach a saturation point. By characterizing the thermal performance of the module, the effect of material properties and operational parameters can be studied in order to design a module that can meet the needs of a power generation plant.

Enhanced Heat Transfer Through the Use of Nanofluids in Forced Convection

2004 ◽  
Author(s):  
Daniel J. Faulkner ◽  
David R. Rector ◽  
Justin J. Davidson ◽  
Reza Shekarriz
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Convective Heat Transfer ◽  
Flow Regime ◽  
Forced Convection ◽  
Convective Heat ◽  
Reynolds Numbers ◽  
Enhanced Heat Transfer ◽  
Low Reynolds Numbers ◽  
Turbulent Flow Regime

Much attention has been paid in recent years to the use of nanoparticle suspensions for enhanced heat transfer. The majority of this work has focused on the thermal conductivity of these nanofluids, which can be as much as 2.5 times higher than that of the plain base fluid. The present work moves beyond measurements of non-flowing liquids, to explore the role that nanofluids can play in enhancing convective heat transfer within microscale channels. A unique pseudo-turbulent flow regime is postulated, which simulates turbulent behavior at very low Reynolds numbers, in what are nominally laminar flows. The resulting fluid mixing has the potential to raise the average convective heat transfer coefficient within the channel. Numerical modeling, using the lattice Boltzmann method, confirms the existence of the pseudo-turbulent flow regime. Finally, experimental results are presented which demonstrate a significant heat transfer enhancement when using nanofluids in forced convection. The current results are especially relevant to microchannel heatsinks, where the low Reynolds numbers impose limitations on the maximum Nusselt number achievable.

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