Just made sense to me, the aluminum tube picks up heat faster, holds a bend, cheaper, makes the whole bundle smaller...I was going to try to use 5/8" aluminum line for the coolant, but it was WAY harder to bend, and aluminum to aluminum (unless welded) barely touches so almost zero heat transfer.

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My other components (HE, SVO filter, SVO pump, Valves and vegie tank) will all be bolted down securely to the frame, so I'm thinking they will likely be okay.

I agree; you and I are saying the same thing I just didn't make it clear enough. I simply copied what Toyota did; wherever the fuel line goes from being secured along the frame to a component like the body, tank, lift pump, or sedimenter, there's a section of flexible hose.

When I added the FPHE to the system, I cut into the fuel circuit between the lift pump and the filter to keep all the connections on the pressure side and used Parker push lock hose with #6 hose clamps to connect to the FPHE.

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Originally posted by B.K. Hosken:
Just made sense to me, the aluminum tube picks up heat faster, holds a bend, cheaper, makes the whole bundle smaller...I was going to try to use 5/8" aluminum line for the coolant, but it was WAY harder to bend, and aluminum to aluminum (unless welded) barely touches so almost zero heat transfer.

Actually I use 1/2" aluminum on 1/2'aluminum and it does heat up, very well in fact. I have the hot coolant pipe in insulation tube with the oil pipe and the return pipe outside on its own. Other designs may be hotter but mine is plenty hot enough to get things flowing well and was so simple to put together
Johnno

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I was going to try to use 5/8" aluminum line for the coolant, but it was WAY harder to bend, and aluminum to aluminum (unless welded) barely touches so almost zero heat transfer.

Interesting that you should say that B.K.

I dug up an old post of Danas' from waaaaay back where he mentioned testing 3 pieces of copper tubing soldered together lengthwise (parallel to each other).

I still like that idea actually. Goop enough solder into the long crack where they touch and it should be even better than a HOT, but still not as efficient as a TIH.

My concern with that design would be that the coolant tubes would expand somewhat sharply and put significantstresses on the smaller dia copper veggie tube sandwitched between the two larger dia coolant tubes.

Maybe I just worry too much...

John, your a hydronics guy, right?

Do you think that a soldered together bundle of 3 soft alloy copper tubes (two 5/8 dia, one 3/8 dia) would be able to handle stresses related to thermal cycling?

It's only maybe 220 F degrees max anyway, right?

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Actually I use 1/2" aluminum on 1/2'aluminum

Wow, another variation!

I guess yours is a TOT (Tube On Tube).

Are there any Tube In Tube systems out there?

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John, your a hydronics guy, right?

yup, I guess it shows?

Actually, I remember you telling me that over a year ago.

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Do you think that a soldered together bundle of 3 soft alloy copper tubes (two 5/8 dia, one 3/8 dia) would be able to handle stresses related to thermal cycling?

What's your opinion?

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My concern with that design would be that the coolant tubes would expand somewhat sharply and put significantstresses on the smaller dia copper veggie tube sandwitched between the two larger dia coolant tubes.
...
Do you think that a soldered together bundle of 3 soft alloy copper tubes (two 5/8 dia, one 3/8 dia) would be able to handle stresses related to thermal cycling?

It's only maybe 220 F degrees max anyway, right?

It would no longer be a bundle of soft alloy copper but a rigid piece of metal. So yes it would be subject to stress fracture.
Why go to the trouble of soldering it? With no solder it will still do the job. Remember what it needs to do. Get the oil hot enough to flow to the HEAT EXCHANGER where it is heated properly.
Johnno

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So yes it would be subject to stress fracture.
Why go to the trouble of soldering it? With no solder it will still do the job.

Didn't you epoxy your veggie tank heater circuit to the bottom of your veggie tank?

Wasn't that done both to secure the tubing and also help transfer heat? Unless the epoxy eventually cracked off of the bottom of the tank, wouldn't that also be imparting thermal expansion/contraction force against the tank bottom and the tanks resistance imparting force back against the tubing?

Wouldn't it also work to epoxying the TOT bundle?