I am working on a problem involving spray dryers. The material to be dryed would be injected through a rotating nozzle with multiple openings from the top. Hot air would be blown from the dryer's bottom part. I was wondering how can I approach the problem to find out the particle's terminal velocity and how is terminal velocity related to reynolds number.any help will be appreciated.

thanks

An interesting problem, indeed.

I would suggest considering the dynamics of the spray-head first. You will have a flowrate of liquid material into the head & so can determine an average exit distribution from the nozzles (assuming 100% distribution). I would imagine that the liquid would break up at some point away from the nozzle exit & travel on as slugs/prills of material. After that point, the prill dynamics would be reasonably straightforward.

The areas that could be of interest:

(1) Fluid distribution within the head - is it 100%, or biased?

(2) The fluid exit dynamics from the nozzle, before prill formation.

(3) The prill dynamics.

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This kind of technology is well represented in the chemical industry & you may very well be able to answer some of your questions from Chemical-Engineering papers - before even moving into cfd simulation.

For example, fertiliser manufacture uses such atomising heads.

Sounds like a nice project. Enjoy...

Des Aubery