Rixen Heat Exchanger size

[clark]

I don't know about the calcs but people seem to be happy with the Rixen output.

[i3enhamin]

Yeah, I see that that is true... it just confuses me.

I'm thinking that their coolant is cooling down, it's just that their 2-3 gallons of coolant in their expansion tank IS enough capacity to act as a buffer for awhile.

So, I expect the 7-gallon tank IS way overkill.

I want to play around with energy storage / getting heat without running the D5 for a couple of hours at a time... so, I would not actively advocate that anybody mimic me. I expect the Rixen numbers do work out a-ok in practice.

[i3enhamin]

And perhaps the propane heaters have much higher ratings due to the decreased efficiency associated with gas -> water hexes as compared to water -> water hexes.

[i3enhamin]

If one assumes 100% efficiency between furnace and the tap... I get that one can have continuous showers if the domestic water tank was at least 68F. With the Rixen 1500w element running, that number goes down to 58F. I expect the 2-3 gallon buffer pushes that down even further. This is probably why people are fine... their domestic probably is not frigidly cold to start with.

[i3enhamin]

I got a response from Duda... they say something like B3-12A 10 Plate Heat Exchanger with M5-.08 Mounting Studs [HX1210] | DudaDiesel Biodiesel Supplies for ~ 1-gpm showers and something like B3-23A 20 Plate Heat Exchanger with M8-1.25 Mounting Studs [HX2320] | DudaDiesel Biodiesel Supplies for ~ 2-gpm. I hope that bounds the problem for you. I'm not sure how much area to add if going with double-wall as compared to those recommendations.

This is with 2-gpm 170F coolant on one side.

[clark]

The 30 plate is cheaper on Amazon than the 20. I'm gonna go with that. Should have plenty of hot water.