I am considering fitting a feedwater preheater to a small marine type engine. The heater would be of the "concentric pipe" type whereby the feedwater will pass through a 3/32" copper tube which is jacketed by a larger bore tube.
What bore should I make the jacketing tube ?
What would be minimum length of jacket to be effective ?
How long & piece of string come to mind but if it is of any assistance the pump bore is 5/32" with 3/16" stroke.
Mick