Hi @Rob

Effectively the delta t = 0.1 s is the time step, which can be estimated in the case of heat conduct as L^2/ nu with L being the width of the plate (the solid) and nu being the heat transfer diffusivity (lambda / (rho*Cp) ) . 

I guess the physical time is equivalent to the transient state time before the solution becomes stationary.

The exponential heat transfer curve can estimate it 

The delta t = 5 s is the global time step, and the number of iterations is 5/ 0.1 

Thank you a lot