A pneumatic conveying duct of 0.2 m diameter and 1 m height has been chosen for simulation (Fig. 1). Similar duct diameter has been reported in the literature for single gas inlet [4,7]. The duct is provided with a main hot air supply before the solid feeding point and hot air entry at three other axial locations of 0.25, 0.5 and 0.75 m in the duct. Distribution of hot air to these entry points was 1 during the simulations. PVC particles of size 1 mm, density 1116 kg/m3 and specific heat 980 J/kg K were chosen for simulation. Inlet air temperature was fixed for all simulations at 126 °C. Physical properties of solids and gas inlet temperature were obtained from literature [2]. Inlet solid temperature and solid mass flow rate were 25 °C and 0.1853 kg/s, respectively. The governing equations were solved by first-order finite difference scheme, with a step size of 0.0005. Inlet conditions were set for gas velocity, pressure, temperature of gas and solid. Inlet solid velocity was taken as a fraction of inlet gas velocity and, accordingly, the volume fractions were calculated at the inlet. The detailed simulation algorithm is available [9]. Four types of simulations were performed: (i)
total gas supply at the bottom, near the solid feeder, (ii) gas supply at bottom and at one axial location, (iii) gas supply at bottom and at two axial locations, and (iv) gas supply at bottom and at three axial locations. Simulations were normally performed from the bottom to the next axial air entry location. At the point of auxiliary air entry at various points in the duct, hot air enters at a temperature of 126 °C at a fixed mass flow rate. The average flow parameters and temperature of the gas at the computational point next to this axial location were determined by making momentum, mass and energy balance for the gas in the computational domain around this gas inlet. Normal simulations were performed from this point till the next location for gas entry. Table 1 shows details of various simulation experiments performed. The ability of model and simulation algorithm to simulate gas–solid heat transfer in pneumatic conveying and predict temperature profiles has been demonstrated [9].
A pneumatic conveying duct of 0.2 m diameter and 1 m height has been chosen for simulation (Fig. 1). Similar duct diameter has been reported in the literature for single gas inlet [4,7]. The duct is provided with a main hot air supply before the solid feeding point and hot air entry at three other axial locations of 0.25, 0.5 and 0.75 m in the duct. Distribution of hot air to these entry points was 1 during the simulations. PVC particles of size 1 mm, density 1116 kg/m3 and specific heat 980 J/kg K were chosen for simulation. Inlet air temperature was fixed for all simulations at 126 °C. Physical properties of solids and gas inlet temperature were obtained from literature [2]. Inlet solid temperature and solid mass flow rate were 25 °C and 0.1853 kg/s, respectively. The governing equations were solved by first-order finite difference scheme, with a step size of 0.0005. Inlet conditions were set for gas velocity, pressure, temperature of gas and solid. Inlet solid velocity was taken as a fraction of inlet gas velocity and, accordingly, the volume fractions were calculated at the inlet. The detailed simulation algorithm is available [9]. Four types of simulations were performed: (i)
total gas supply at the bottom, near the solid feeder, (ii) gas supply at bottom and at one axial location, (iii) gas supply at bottom and at two axial locations, and (iv) gas supply at bottom and at three axial locations. Simulations were normally performed from the bottom to the next axial air entry location. At the point of auxiliary air entry at various points in the duct, hot air enters at a temperature of 126 °C at a fixed mass flow rate. The average flow parameters and temperature of the gas at the computational point next to this axial location were determined by making momentum, mass and energy balance for the gas in the computational domain around this gas inlet. Normal simulations were performed from this point till the next location for gas entry. Table 1 shows details of various simulation experiments performed. The ability of model and simulation algorithm to simulate gas–solid heat transfer in pneumatic conveying and predict temperature profiles has been demonstrated [9].
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