Aluminum TiH versus rubber HoH heat transfer

For discussing the modifications needed for diesel vehicles to run with 2 tank veggie oil conversions.

Moderators: SunWizard, coachgeo

Aluminum TiH versus rubber HoH heat transfer

Postby SunWizard » Thu Apr 24, 2008 11:03 pm

I did some thermodynamics calculations comparing a TiH to HoH, and the results surprised me. TiH can make so much heat it could eliminate the need for FPHE and at much lower cost. (depending on your plumbing.)

8' of 3/8" alum. tube in hose (TiH), 100F delta temp between coolant and VO transfers 21,946,000 BTU/hr of heat.
8' of 3/8 alum. tube sandwiched between 2 rubber hoses (HoT), 100F delta, transfers 4592 BTU/hr of heat. Rubber HoH is about half this.

This is not taking into account flow in the hose/tube, its just the heat transfer across the rubber and alum., flow will increase the BTUs slightly, and thermal efficiency decreases it, and gets complex.

Formulas and numbers here:
http://www.marshall.k12.wi.us/mhs/teach ... alues.html
The key number to note is the U value, heat conductance:
1/16" of Alum.= 279571
1/8" of Rubber=117

Besides the thermodynamics above, I have done actual heat transfer tests with rubber hose on metal, and TiH, and the results agree with the expected numbers above, of 1000s of times more heat transfer with TiH.

HoH may be enough to keep your VO liquid in the hose, but its not much heat in comparison. Whether it is enough depends on how well you insulate the HoH, and how cold it is outside, and how you plumb your rig, and how much heat you need before your filter.

This also explains why when I did tests of my rubber hose wrapped filter, I got 20F gain after 30 minutes. This was less than I expected. Now I see its because the filter wrap is equal to only 300 watts of power. (1 watt=3.4 BTU.)

Edit: U calcs were off due to inches to meters conversion, calcs revised.
Last edited by SunWizard on Fri Apr 25, 2008 9:16 am, edited 1 time in total.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
SunWizard
Site Admin
 
Posts: 1723
Joined: Mon Dec 11, 2006 2:53 pm
Location: N. Colorado

Postby 240Volvo » Fri Apr 25, 2008 8:08 am

This is very interesting. The question then is, how is it to be plumbed? Does one plumb from fuel pick-up to filter (or the reverse)? Very interesting. Do you recall the FPHE btu output for comparison?

You are da man!
1984 Volvo 240 diesel with a single tank Elsbett conversion: electric fuel filter heater, FPHE, glow plugs, and injectors. Also injector line heaters and block heater, running 20%kero/80%WVO winter blend.
240Volvo
 
Posts: 127
Joined: Thu Mar 06, 2008 8:34 am
Location: New Jersey

Postby Jake Palmer » Fri Apr 25, 2008 8:24 am

Geat stuff!

Here's what I posted in all aluminum hoh or tot thread:

I have used HoH and TiH in the same car and had the same heat output. That was a VW 1.6 Jetta, with the lines run inside the car.

Was it an abberation? Perhaps. But it was enough to convince me that HiH was hard to justify for my needs... which was simply to deliver WARM oil to the final heat exchanger at the front of the car.

SunWizard wrote:8' of 3/8" alum. tube in hose (TiH), 100F delta temp between coolant and VO creates 558000 BTU/hr of heat, more than most FPHE.
8' of 3/8 alum. tube sandwiched between 2 rubber hoses (HoT), 100F delta, creates 98 BTU/hr of heat.


Hmmm
Just a couple observations when I compare your formula to what my setup was:
-Even in a Jetta, my HoH run is almost 20' by the time it makes it circuituous route in the trunk, around the strut tower, around the seat back, under the rocker, up behind the dash and through the firewall.
-I was able to get ~45-50*C fuel out of my HiH, and got the same out of the HoH.

A couple other considerations that make my experience a bit less than scientific:
-I'm positive my HiH was shorter than my HoH. Probably by 5' or so.
-My heated fuel pickup usually added ~15*C to the fuel temp... meaning the HoH/HiH was not the ONLY source of heat being measured
-At some point in there, I did change my thermostat because the car wasn't heating up enough. In retrospect, that alone would skew things a lot. But what are ya gonna do when it's winter and your daily driver has no heat? Momma don't care about science when her feet are cold.

SunWizard wrote:HoH may be enough to keep your VO liquid in the hose, but its not much heat in comparison. Whether it would be enough would mainly depend on how well you insulate the HoH, and how cold it is outside, and how you plumb your rig, and how much heat you need before your filter.
[snip]
I am glad your post inspired me to do those calculations, since it shows how useful a TiH can be, in some cases eliminating the need for FPHE and at much lower cost. I think I will start a new post about that issue.


I agree 100% with all of that. There is no question that stand-alone, HiH would give hotter temps than HoH. I guess the question is whether or not it needs to. In my experience, with a good heated fuel pickup to boost temps and well insulated lines, HoH works great... as long as you're happy with 50*C output. That's more than sufficient if you're just using the HoH to get the fuel to a final heat exchnager, be it an FPHE or a Vegtherm.

But if you want to eliminate an FPHE & Vegtherm, then HoH is not the way to go. A long length of HiH can probably supplant a final heat exchanger, if there's a need to do that. HoH can't
Jake Palmer
 
Posts: 69
Joined: Tue Mar 04, 2008 11:12 pm
Location: New Brunswick

Postby SunWizard » Fri Apr 25, 2008 9:38 am

240Volvo wrote:This is very interesting. The question then is, how is it to be plumbed? Does one plumb from fuel pick-up to filter (or the reverse)? Very interesting. Do you recall the FPHE btu output for comparison?

Plumbing depends on many other options, one being getting enough heat before your filter, other getting enough heat before your IP. FPHE are rated for actual BTU at various flows and Temp difference.

Here is a good comparison, a 2"x6" 16 plate will have a heat exchange area of ~8 square feet. An 8' TiH will have a heat exchange area of 0.785 sq. ft. Since aluminum is such a good conductor, either one will put out VO that nearly equals the coolant temps. I have verified this by measuring the VO temp right after my TiH.

Even a 16 plate FPHE is overkill on my truck, but I didn't know this at the time I bought my 26 plate. At least the price was almost the same between 16 and 26.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
SunWizard
Site Admin
 
Posts: 1723
Joined: Mon Dec 11, 2006 2:53 pm
Location: N. Colorado


Return to 2 Tank veggie oil conversion and General discussion

Who is online

Users browsing this forum: No registered users and 0 guests

cron