Conjugate Heat Transfer Transient Issues

I am new to Simscale and are currently doing a Conjugate heat transfer problem looking at a basic heating system comprising of two heatsinks within a duct system. (Screenshot below). I am interested in looking at a Transient problem in finding when the airflow out of the duct reaches a certain temperature. I think I have set up my problem okay (steady state analysis seemed to work) however I am having some problems setting up the transient problem. The modelling time seems to be excessive(>90 mins) and the current setup seems to be taking many time steps ( I only need 1 second time steps up to 30-40 secs). Any advice on how to set up the problem better? Screenshots showing the simulation control and divergence plots are shown below

Hey there, and welcome to the forum!

It is perfectly normal for a transient simulation to take much more time to compute than a steady state one.

One thing that could help with convergence is to ramp up the inlet velocities and thermal loads at the beginning of the analysis, from zero to the maximum value, for a few seconds, then allow it to run for your needed time.

But this won’t cut on computational time, which I think is inevitable.

Maybe someone from the community has something to add?