Abstract
This study investigated thin layer drying of squash seeds under semi fluidized and fluidized bed conditions with initial moisture content about 83.99% (d.b.). An experimental fluidized bed dryer was also used in this study. Air temperature levels of 50, 60, 70 and 80 °C were applied in drying samples. To estimate the drying kinetic of squash seed, seven mathematical models were used to fit the experimental data of thin layer drying. Among the applied models, Two-term model has the best performance to estimate the thin layer drying behavior of the squash seeds. Fick’s second law in diffusion was used to determine the effective moisture diffusivity of squash seeds. The range of calculated values of effective moisture diffusivity for drying experiments were between 0.160 × 10−9 and 0.551 × 10−10 m2/s. Moisture diffusivity values decreased as the input air temperature decreased. Activation energy values were found to be between 31.94 and 34.49 kJ/mol for 50 °C to 80 °C, respectively. The specific energy consumption for squash seeds was calculated at the boundary of 0.783 × 106 and 2.303 × 106 kJ/kg. Increasing in drying air temperature in different bed conditions led to decrease in specific energy value. Results showed that applying the semi fluidized bed condition is more effective for convective drying of squash seeds. The aforesaid drying characteristics are useful to select the best operational point of fluidized bed dryer and to precise design of system.
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Abbreviations
- C Pv :
-
Specific heat capacity of vapor (1004.16 J/kg °C)
- C Pa :
-
Specific heat capacity of air (1828.8 J/kg °C)
- D 0 :
-
Pre-exponential factor of the Arrhenius equation (m2/s)
- D eff :
-
Effective moisture diffusivity (m2/s)
- E a :
-
Activation Energy (kJ/mol)
- h a :
-
Absolute air humidity (kgvapor/kgdry air)
- i:
-
Data number
- L :
-
Thickness, m
- m v :
-
Mass of removal water (kg)
- M :
-
Moisture content (% d.b.)
- M 0 :
-
Initial moisture content (% d.b.)
- M e :
-
Equilibrium moisture content (% d.b.)
- MR :
-
Moisture ratio (decimal)
- MR exp,i :
-
Experimental moisture ratio of ith data (decimal)
- MR pre,i :
-
Predicted moisture ratio of ith data (decimal)
- n:
-
Number of terms taken into consideration
- N :
-
Number of observations
- Q :
-
Inlet air to drying chamber (m3/s)
- R :
-
Universal gas constant (8.3143 kJ/mol K)
- RMSE :
-
Root mean square error
- R 2 :
-
Correlation coefficient
- SEC :
-
Specific energy consumption (kJ/kg)
- t:
-
Drying time (s)
- T :
-
Absolute air temperature (K)
- T in :
-
Inlet air temperature to drying chamber (°C)
- T am :
-
Ambient air temperatures (°C)
- V h :
-
Specific air volume (m3/kg)
- z :
-
Number of drying constants
- χ 2 :
-
Chi-square
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Chayjan, R.A., Salari, K., Abedi, Q. et al. Modeling moisture diffusivity, activation energy and specific energy consumption of squash seeds in a semi fluidized and fluidized bed drying. J Food Sci Technol 50, 667–677 (2013). https://doi.org/10.1007/s13197-011-0399-8
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DOI: https://doi.org/10.1007/s13197-011-0399-8