Thanks for your reply!

I also checked the units. The heat transfer here is defined for solid particles as the following equation.  So, the unit is W.

mc(dT/dt)p=qreaction + qradiation

Where did you set the heat transfer rate?

As you may know, Rocky has ready-to-use costume modules that can be added to the software. Inside the source code of the particle combustion module, I just corrected the radiation heat transfer to 1 W.