Numerical simulation of heat transfer and phase change during freezing of potatoes with different shapes at the presence or absence of ultrasound irradiation
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As novel processes such as ultrasound assisted heat transfer are emerged, new models and simulations are needed to describe these processes. In this paper, a numerical model was developed to study the freezing process of potatoes. Different thermal conductivity models were investigated, and the effect of sonication was evaluated on the convective heat transfer in a fluid to the particle heat transfer system. Potato spheres and sticks were the geometries researched, and the effect of different processing parameters on the results were studied. The numerical model successfully predicted the ultrasound assisted freezing of various shapes in comparison with experimental data of the process. The model was sensitive to processing parameters variation (sound intensity, duty cycle, shape, etc.) and could accurately simulate the freezing process. Among the thermal conductivity correlations studied, de Vries and Maxwell models gave closer estimations. The maximum temperature difference was obtained for the series equation that underestimated the thermal conductivity. Both numerical and experimental data confirmed that an optimum condition of intensity and duty cycle is needed for reducing the freezing time, as increasing the intensity, increased the heat transfer rate and sonically heating rate, simultaneously, that acted against each other.
KeywordsHeat transfer Phase change Numerical modeling CFD
Surface area (m2).
Specific heat (J kg−1 K−1).
Apparent specific heat (J kg−1 K−1).
Fluid specific heat (J kg−1 K−1).
Convective heat transfer coefficient (W m−2 k−1).
Ultrasound intensity (W m-2).
Thermal conductivity (Wm−1 K−1).
Fluid thermal conductivity (Wm−1 K−1).
Latent heat of freezing (J kg−1).
Nusselt value when sonication is applied.
Source term caused by phase change (J m−3 s−1).
Source term caused by ultrasound irradiation (J m−3 s−1).
Heat generation rate caused by ultrasound irradiation (W kg−1).
Initial freezing temperature of potato (°C).
Potato freezing temperature (°C).
Freezing temperature of water (°C).
Initial product temperature (°C).
Free stream temperature (°C).
Bulk velocity (m s−1).
Mass fraction (kg kg−1).
Total water fraction.
Bond water fraction.
- x, y, z
- X, Y, Z
Boundary coordinate (m).
Density (kg m−3).
Fluid density (kg m−3).
Compliance with ethical standards
Conflict of interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
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