I need to know how to determine the heat transfer areas of a granulated solid in a dryer, the contact area between the solid and the cylinder wall, the area of solid that is in contact with the drying agent (air or gas) and the area of the inner wall of the cylinder that has contact with the gas
I don't think these parameters can be easily determined in an industrial field test. My guess is that a particle does not spend so much time in direct contact with the wall or the fresh drying gas. Rather, the particle will spent most of its lifetime in the bulk of the solids, surrounded by other particles.
You could consider performing an experiment, where you track the whereabouts of a single (colored) particle using a video camera. More advanced techniques like magnetic- (MPT) or positron emission particle tracking (PEPT) exist. Alternatively, you could resort to numerical simulations (Discrete particle models, DPM).
If you can assume that the granulated solids are small spheres and that the walls of the dryer are cylindrical, then some analytical models, which were originally developed for ball earings might be a decent approximation.
I've attached some literature that you can check out.
However, finding out the share of convective heat transfer may be the difficult part.
Good luck, Armin
Kindly refer book by B K Dutta
Principles of mass transfer and separation processes
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