[MNWayne]

I'm trying to find one of these corrugated things that wrap around a brew pot, (https://www.msrgear.com/stoves/stove-accessories/heat-exchanger/321105.html), it must be large enough to fit a 20 gallon Spike brew kettle.  They call it a heat exchanger, but that term doesn't net the proper results on a web search. 

[brewthru]

Cajun cooker wind block.

[MNWayne]

I'm not finding anything under Cajun Cooker.  Could you send me a link?

[mabrungard]

I see that that collar is intended to be tightly fitted to the kettle and the corrugations help capture and transfer the heat to the kettle.  I'm not sure you really need to do that.  A wind-shield collar could provide much of what that collar does.

The purpose of a collar is to help channel the heat from the burner up the sides of the kettle.  A piece of sheet metal wrapped around the burner stand that helps form a 'chimney' that contains and channels the heat, could be a less-expensive option.

[MNWayne]

I believe the corrugated design which is in tight contact with the pot will add some conductive heat transfer.  MSR claims a 25% increase in efficiency.  If I can't find one of these I suppose I'll have to make something myself out of sheet metal.

[brewthru]

try turkey frier wind shield

[brewthru]

BYO has a DIY project. See the September 2020 issue.

Or, if having an online account
https://byo.com/project/heat-shield-retain-that-wasted-energy/