Discussion Forum

The system I am dealing with is heating a packed of bed of adsorbent material 17.7% by volume and having 7% by volume of metal fibers packed inside it. The axisymmetric bed of 0.1016 m radius and 0.4064 m height, can be homogeneously heated both from outside the wall of thickness 0.002 m on right boundary, and from the center by a heater rod of radius 0.003 m. There is a 1/2 inch insulation outside the wall. There is no flow going through the bed. The current COMSOL file attachment has the case of providing heat only from the center to achieve an average temperature of 443 K in 5 minutes i.e., delta T of 143 K (443K-300K). The parameters specific heat of metal = 0.385 (kJ/kg/K), density of metal = 8933 kg/m^3, specific heat of adsorbent = 1.1 (kJ/kg/K), density of adsorbent = 1093 kg/m^3, specific heat of wall = 0.477 (kJ/kg/K), density of wall =7900 kg/m^3, and the power required to heat the bed in 5 minutes upto 443 K is 3.8 kW as shown as parameter PP by calculation. Whereas with simulation we see with Powerin of 0.2 kW the same temperature (surface average) is achieved in 5 minutes. Please suggest what could be reason behind this discrepancy and whats the error ? Your help is much appreciated. Also does COMSOL account for cylindrical coordinate term of 1/r(r* dT/dr) in the flux term for axisymmetric model?