Quote Originally Posted by mad fridgie View Post
I suspect simulators now a days are a lot better than simple steady state calcs that we used in the past.
The trouble is - they're not.

A simulator generally gives a static snapshot of what is a thermodynamically-stable system i.e. one that has been stable & unchanging for a long, long time (infinite time). Coolpack, for instance works this way. In this sense, all they do is to automate the hand calculations that any good fridgie could do, anyway.

Things like dynamic response, mass charge & so forth, would be found in some academic research codes, but, they are not common in the public domain.

I agree with the folks who refer to the use of simulators to get through the initial design stage & then hands-on tuning to settle the real system. This is the strength of it. Sometimes, referring back to the simulator to assist analysis of the real operational data can be useful, but, in the end, where the rubber hits the road is whether the unit actually works as per original design, or not.

In many cases, if the original design is too tight, then real performance can suffer. On the other hand, if the spec is too loose, then system stability may suffer, as well as system costs. It's a balancing act all the way.