Abstract
Dynamic experiments in a nonadiabatic packed bed were carried out to evaluate the response to disturbances in wall temperature and inlet airflow rate and temperature. A two-dimensional, pseudo-homogeneous, axially dispersed plug-flow model was numerically solved and used to interpret the results. The model parameters were fitted in distinct stages: effective radial thermal conductivity (K r) and wall heat transfer coefficient (h w) were estimated from steady-state data and the characteristic packed bed time constant (τ) from transient data. A new correlation for the K r in packed beds of cylindrical particles was proposed. It was experimentally proved that temperature measurements using radially inserted thermocouples and a ring-shaped sensor were not distorted by heat conduction across the thermocouple or by the thermal inertia effect of the temperature sensors.
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Abbreviations
- Bi :
-
Biot number (dimensionless)
- Bi s :
-
Solid-wall Biot number (dimensionless)
- Cp f :
-
Fluid heat capacity (J/kg °C)
- Cp s :
-
Solid heat capacity (J/kg °C)
- d p :
-
Sphere-equivalent particle diameter (m)
- d t :
-
Tube diameter (m)
- G :
-
Superficial mass flow rate (kg/m2 s)
- h w :
-
Wall heat transfer coefficient (W/m2 °C)
- \( h_{w}^{o} \) :
-
Wall heat transfer coefficient with a stagnant fluid (W/m2 °C)
- J o :
-
Zeroth-order Bessel function, first kind
- J 1 :
-
First-order Bessel function, first kind
- K a :
-
Effective axial thermal conductivity (W/m °C)
- K r :
-
Effective radial thermal conductivity (W/m °C)
- \( K_{r}^{o} \) :
-
Effective radial thermal conductivity of the bed with a stagnant fluid (W/m °C)
- k f :
-
Fluid conductivity (W/m °C)
- k p :
-
Pellet conductivity (W/m °C)
- k s :
-
Solid conductivity (W/m °C)
- L :
-
Fixed bed length (m)
- N S :
-
Interphase heat transfer group (dimensionless)
- Pe a :
-
Axial Peclet number (dimensionless)
- Pe af :
-
Axial fluid Peclet number (dimensionless)
- Pe r :
-
Radial Peclet number (dimensionless)
- Pr :
-
Prandtl number (dimensionless)
- R :
-
Tube radius (m)
- r :
-
Radial position (m)
- r * :
-
Radial position (dimensionless)
- Re :
-
Reynolds number (G d p /μ)
- t :
-
Time (s)
- T :
-
Temperature (°C)
- T o :
-
Inlet air temperature (°C)
- T w :
-
Wall temperature (°C)
- T ini :
-
Fixed bed initial temperature (°C)
- \( T_{ij}^{calc} \) :
-
Calculated temperature (°C)
- \( T_{ij}^{\exp } \) :
-
Experimental temperature (°C)
- T*:
-
Temperature (dimensionless)
- u c :
-
Superficial velocity in the core of the bed (m/s)
- \( \bar{u}_{o} \) :
-
Average superficial velocity (m/s)
- z :
-
Axial position (m)
- z * :
-
Axial position (dimensionless)
- α:
-
Significance level (dimensionless)
- ε b :
-
Bed porosity (dimensionless)
- ε p :
-
Particle porosity (dimensionless)
- μ :
-
Fluid viscosity (kg/m s)
- θ :
-
Time (s)
- ρ s :
-
Solid density (kg/m3)
- τ :
-
Packed bed time constant (s)
- τ T :
-
Temperature sensor time constant (s)
- Φ:
-
Objective function (°C2)
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Acknowledgments
The authors gratefully acknowledge financial support from CAPES—Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Brasília, Brazil) and FAPESP—Fundação de Amparo à Pesquisa do Estado de São Paulo (São Paulo, Brazil).
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Jorge, L.M.M., Jorge, R.M.M. & Giudici, R. Experimental and numerical investigation of dynamic heat transfer parameters in packed bed. Heat Mass Transfer 46, 1355–1365 (2010). https://doi.org/10.1007/s00231-010-0659-6
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DOI: https://doi.org/10.1007/s00231-010-0659-6