In a pinch I have done it the opposite way - wort chiller in hlt and run wort through the inside. I don't normally do HERMS (I would like to get there) but I was so far off on my mash temp I had to do something to increase quickly and I was too full to add enough hot water to get there. Still not sure what my mix up was but it worked very well and the beer turned out great.
Well it will work great idea! In the industrial environment we use large "wort chillers", e.g. heat exchangers, to heat product. We run hot oil (330F-350F) to heat stearic acid mixtures to about 250F-280F.
So yes! Good idea, now you just have to find out what your F/min is. Just make sure to keep the "wort chiller" (heat exchanger) well insulated!
I had been hard at work researching brewing rigs and trying to come up with a system that is both simplistic, yet everything I would need. The 3 pump system from JonW inspired this idea, though his system is NG, I was trying the figure out the best way to run it with electric but still keep it streamlined. Anything thanks for the input!
What kind of wort chiller are you talking about? Using an immersion chiller is essentially the same as a standard HERMS setup, and while a plate chiller is very efficient it can clog. Are you thinking counterflow?
I've used a wort immersion chiller as HERMS in the past but my results varied quite a bit. I have now moved onto a full HERMS keg sent up which works much better.
Give it a shot for yourself I wish you much success.