Abstract
The drying behavior at low temperatures has been studied with four different uniformly sized particles and three different binary mixtures at different dilutions ranging from 10 to 40 % with an interval of 10 % varying parameters such as air velocity, initial moisture content, initial bed height and temperature. Falling rate period one and two were observed and correlations were developed to predict the drying rate in falling rate periods one and two. Correlations were also developed to predict the average moisture content by considering the effect of various parameters for uniformly sized particles and binary mixture of solids. The heat and mass transfer coefficients have been found for different conditions and compared. Comparison of experimental and predicted average moisture contents for uniformly sized particles and for various binary mixtures has been made and the predicted average moisture content has been found to be in good agreement with experimental average moisture content.
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Abbreviations
- C in , C 0 :
-
Initial moisture content of solids (kg water/kg dry sand)
- C t :
-
Moisture content with respect to time (kg water/kg dry sand)
- C*:
-
Moisture content at the end of falling rate period one (kg water/kg dry sand)
- C eq :
-
Equilibrium moisture content (kg water/kg dry sand)
- \(\overline{C}\) :
-
Average moisture content (kg water/kg dry sand)
- \(\overline{C}_{U}\) :
-
Average moisture content of uniform particle sizes (kg water/kg dry sand)
- \(\overline{C}_{BM}\) :
-
Average moisture content of binary mixtures (kg water/kg dry sand)
- d p :
-
Diameter of the particle (m)
- \(\overline{{d_{p} }}\) :
-
Average diameter of particles (m)
- D v :
-
Diffusivity (m2/s)
- H :
-
Initial static bed height (cm)
- h :
-
Heat transfer coefficient (W/m2 K)
- k g,bed :
-
Mass transfer coefficient (1/s)
- K :
-
Thermal conductivity (W/m K)
- M :
-
Molecular weight
- Nu p :
-
Nusselt number of particles, \(Nu\, = \frac{{hd_{p} }}{{K_{g} }}\)
- Pr g :
-
Prandtl number of gas, \(\Pr \, = \,\frac{{C_{p} \mu }}{{K_{g} }}\)
- R :
-
Drying rate (kg water/kg dry sand s)
- R 1 :
-
Drying rate in falling rate period one (kg water/kg dry sand s)
- R 2 :
-
Drying rate in falling rate period two (kg water/kg dry sand s)
- \(\text{Re}_{p}\) :
-
Reynolds number of particles, \(\text{Re}_{p} \, = \,\frac{{\rho_{g} u_{0} d_{p} }}{{\mu_{g} }}\)
- Sh bed :
-
Sherwood number of bed, \(Sh\, = \frac{{k_{g} d_{p} }}{{D_{v} }}\)
- Sc :
-
Schmidt number, \(Sc\, = \,\frac{{\mu_{g} }}{{\rho_{g} D_{v} }}\)
- t :
-
Time (s)
- T :
-
Temperature (°C)
- u, u 0 :
-
Air velocity (m/s)
- V :
-
Critical molar volume (m3/g mol)
- W :
-
Weight of solids (kg)
- X :
-
Weight fraction
- y :
-
Mole fraction
- δ :
-
Bubble fraction in bed
- ρ :
-
Density (kg/m3)
- μ :
-
Viscosity of gas (kg/m s)
- ε :
-
Voidage
- ϕ :
-
Sphericity
- g :
-
Air
- p :
-
Particles
- s :
-
Solids
- mf :
-
Minimum fluidization
- f :
-
Fluidization
- A:
-
Air
- W:
-
Water
- CA:
-
Critical air
- CW:
-
Critical water
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Srinivas, G., Pydi Setty, Y. Heat and mass transfer studies in a batch fluidized bed dryer using Geldart group D particles. Heat Mass Transfer 50, 1535–1542 (2014). https://doi.org/10.1007/s00231-014-1364-7
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DOI: https://doi.org/10.1007/s00231-014-1364-7