Reply
 
Thread Tools Display Modes
 
Old 04-01-2007, 08:44 AM   #11
Bus Geek
 
lapeer20m's Avatar
 
Join Date: Nov 2003
Location: near flint michigan
Posts: 2,653
it seems to me that pex tubing, being plastic won't be very good at exchanging heat. This is good if you want to transport hot liquids over a distance ie: outdoor boiler, but is not so good if you want to use it as a heat exchanger.

why not use a heater core (small alluminum radiator) i have purchased several of them from the scrap yard for $10 each. I haven't done the math, but would estimate that they transfer heat 10x better than a 10 foot length of 1/2" copper tubing. Copper tubing must tranfer heat at least 10X better than pex tubing i would think.
__________________
Quis custodiet ipsos custodes (who will watch the watchmen?)
lapeer20m is offline   Reply With Quote
Old 04-03-2007, 04:38 PM   #12
Bus Nut
 
swinada's Avatar
 
Join Date: Mar 2007
Location: Northern BC Canada
Posts: 538
PEX is great for waterlines and infloor or radiant heating systems. But for heatexchangers copper is defenetly better. However I second lapeer20m with his idea of using an old small radiator, you will have way more transfer area thanks to the fins.

If you work with PEX pipes and you accidently kink one, just use a LP torch to heat it up and it will take up its regular shape again. No need of cutting out kinked pieces an joining them.

I'm not familier with Veggie oil setups so I dont know why you need this heat exchanger and where,but an other idea might be to have an external "FlatPlate Heatexchanger" http://www.flatplate.com/
I have one of those in my radiant heat system in my home, they dont take up much space and work great.
__________________
Proud owner of a: 1996 Thomas Safe-T-Liner,Cummins 6CTA 8.3Lt diesel, Allison AT.
http://picasaweb.google.com/swinada/BusPictures http://www.swinada.com/bus.htm
http://lh4.ggpht.com/swinada/SL91F-b...opbussmall.jpg
swinada is offline   Reply With Quote
Old 04-03-2007, 06:11 PM   #13
Bus Geek
 
the_experience03's Avatar
 
Join Date: Feb 2006
Location: Saint James, MN
Posts: 2,669
Send a message via MSN to the_experience03 Send a message via Yahoo to the_experience03
The reason for the heat exchanger is to heat up the oil so that it flows easier. At 160 degrees F it is still about 3 times more viscous than diesel fuel from what I've read, but is thinned out enough that you shouldn't have problems. Thicker stuff can hurt parts and won't inject well leading to injector damage and coking.

My bus uses a flatplate heat exchanger and they RAWK for getting the oil up to temp for injection. My issue is with getting the oil to the heat exchanger so I'm working on heating my lines and tank pickup enough to get adequate flow to that heat exchanger. Pound for pound and volume to volume you can't beat a crossflow flat plate heat exchanger for efficiency.
__________________
http://farm4.static.flickr.com/3024/...09f20d39_m.jpg
Skooling it...one state at a time...
the_experience03 is offline   Reply With Quote
Old 10-08-2007, 03:27 PM   #14
New Member
 
Join Date: Sep 2007
Location: Hillsboro ND
Posts: 4
Year: 1993
Coachwork: Thomas
Chassis: MPV
Engine: Cat 3116 250
Rated Cap: 90
Send a message via MSN to Grizzers Send a message via Yahoo to Grizzers
Re: Pex as heat exchanger?

I am wanting to make the conversion to WVO and am at the beginning of the entire bus conversion process. For heat in the living area I plan on a 6 gal water heater, circ pump and expansion tank with pex tubing and baseboard radiators. Now I also thought about doing a similar setup and run the lines to my WVO tank/s. The heaters are propane and the circ pump is 12VDC so I could start heating the fuel the night before and should have a tank that is nice and warm.

Instead of water, RV antifreeze (for winterizing RV tanks) since it will allow for higher temps if needed. I was planning on setting the temp at 140 to start and adjust from there. The heat exchanger will most likely be somesort of radiator inside the tank.

I figure that I can also run the pex next to the fuel line and insulate both of them to keep the fuel warm as it goes to the engine.

tom
__________________
Grizzers
1993 Thomas Safe T Liner MPVRE
Cat 3116-250
Grizzers is offline   Reply With Quote
Old 10-08-2007, 09:10 PM   #15
Skoolie
 
Join Date: Aug 2006
Location: Breckenridge, CO
Posts: 187
Re: Pex as heat exchanger?

Well I have used the pex for the past 10K miles and it seems to have put up well with no signs of wear or breaking down. We'll see.
__________________
1989 TC 2000; 235,000miles; 5.9 cummins with Alisson 545; Straight veggie burning with onboard filtration. Converting to a Toy Hauler for the summers racing motorcycles.
dlor1 is offline   Reply With Quote
Old 10-11-2007, 09:58 AM   #16
Bus Nut
 
KC10Chief's Avatar
 
Join Date: Jun 2006
Location: Edmond, OK
Posts: 529
Year: 1993
Coachwork: Carpenter
Chassis: International
Engine: 7.3 International diesel
Rated Cap: 60
Re: Pex as heat exchanger?

for my veggie heat exchanger, I was looking at using the one I took out of my rear floor heater in the bus. It's kind of big though and 14 years old. I'd hate for it to spring a leak in the tank. I thought about getting a new heater core from Auto Zone, but again, they sell those things because they spring leaks. I think the SAFEST thing to do would be to use coiled up copper line. I would NEVER EVER use Pex. A temp rating of 200 degrees? I'd be scared the whole time I was driving my bus. An engine at normal operating temperature runs about 195 degrees. Start climbing a hill or sit in traffic on a hot day and you've just exceeded your rating. Imagine that you spring a leak in your tank. Not only are you losing coolant, but you're pumping it into your engine. Now, you're on the side of the road with no coolant and jacked up injectors because you wanted to save a few bucks. In my opinion, this isn't an area where you want to save some money. Just buy the copper tubing.
__________________
Matt
1993 International Carpenter 10 Window bus
7.3L diesel w/AT545
http://i74.photobucket.com/albums/i2...DSC02426-1.jpg
KC10Chief is offline   Reply With Quote
Old 10-11-2007, 12:38 PM   #17
Bus Geek
 
the_experience03's Avatar
 
Join Date: Feb 2006
Location: Saint James, MN
Posts: 2,669
Send a message via MSN to the_experience03 Send a message via Yahoo to the_experience03
Re: Pex as heat exchanger?

The only saving grace I can think of when it comes to that 200 degree rating is that that is in ambient, uncirculating air. Basically what I'm saying is that hte oil is going to act as a much better means of conducting the heat away from the tubing.

For example...when cooling a computer fan blown air is the standard. For those running serious overclocks or otherwise needing to get rid of heat there is water cooling which runs FAR cooler, but still needs a radiator somewhere in the system. But what about those people that build computers in aquariums full of mineral oil? They have no heat sink other than the uncirculating oil and can run plenty cool (and quiet).

How about boiling water in a plastic bottle over a fire? Ever done that? I have. The plastic distorts, but it does not burn through as long as you do it properly and the #2 plastic used in a 20 ounce pop (soda or coke for you people in other regions) bottle is not nearly as tough or as thick as PEX.

I agree that it might be pushing the limits, but maybe that's what bus conversion is all about.
__________________
http://farm4.static.flickr.com/3024/...09f20d39_m.jpg
Skooling it...one state at a time...
the_experience03 is offline   Reply With Quote
Old 10-11-2007, 05:50 PM   #18
Bus Nut
 
KC10Chief's Avatar
 
Join Date: Jun 2006
Location: Edmond, OK
Posts: 529
Year: 1993
Coachwork: Carpenter
Chassis: International
Engine: 7.3 International diesel
Rated Cap: 60
Re: Pex as heat exchanger?

That's one limit I don't plan to test! If it had say a 450 degree rating, then I'd try it out. I'm sure that there is a margin of error built into that 200 degree rating, but when you're right at the materials limit, it's going to wear out pretty fast. I'd rather pay the extra $50 for some copper tubing than pay for a new engine.
__________________
Matt
1993 International Carpenter 10 Window bus
7.3L diesel w/AT545
http://i74.photobucket.com/albums/i2...DSC02426-1.jpg
KC10Chief is offline   Reply With Quote
Old 12-03-2007, 10:59 PM   #19
Skoolie
 
Join Date: Aug 2006
Location: Breckenridge, CO
Posts: 187
Re: Pex as heat exchanger?

Well 12,000 miles later the pex hasn't flinched. I agree that testing this material may be stupid, for my sake I hope not. I have fiddled with the pex when it is at it's hottest and it seems very rigid still. Not trying to advocate the use of pex just saying that mine is working......so far.
__________________
1989 TC 2000; 235,000miles; 5.9 cummins with Alisson 545; Straight veggie burning with onboard filtration. Converting to a Toy Hauler for the summers racing motorcycles.
dlor1 is offline   Reply With Quote
Old 12-24-2007, 04:44 PM   #20
New Member
 
Join Date: Dec 2006
Location: Central Coast, California
Posts: 8
Re: Pex as heat exchanger?

Might I suggest a length of stainless steel gas appliance connector hose inside your tank. Under $20 around here and a 5' length would I think give you plenty of heat in your veggie tank, installation not too difficult, they have regular 1/2" pipe fittings. Personally I worry about putting anything 'inside' the tank likewise HIH lines, one leak and you're pretty much gerfunked. I'm using a hotfox and a hose on hose bundle no chance of coolant in the veggie and with the hotfox you don't have to wait for the entire contents of the tank to heat up. Just my 2 cents.

Quote:
Originally Posted by dlor1
I was at Home Depot yesterday trying to get the last things I need for my veggie set up. I was gonna create a coiled copper heat exchanger and was flinching at the cost of copper. I saw this stuff called Pex which is a flexiable plastic compound made to substitute for copper. It's rated to 200 degrees and seems to bend well.

Unless there are any drawbacks I'm not aware of, it seems to be a good canidate for an in tank heat exchanger to move coolant. It costs $12 for 50ft of 1/2in oppossed to $55 for copper.

Any history or opinions?
__________________
1001 Chevy P30 Blue Bird Handy Bus
oilitright is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Vormax heat exchanger FlyingPig Veggie Oil | WVO | Biodiesel | SVO 2 09-25-2014 09:02 PM
heat vanpeoplx2 Heating, Cooling and Appliances 10 01-14-2011 08:34 AM
What should I use for heat? Diesel Dan Conversion General Discussions 2 10-10-2010 08:54 PM
no heat mfrederick Skoolie Conversion Projects 6 01-11-2010 10:05 PM
heat exchanger and two seats needed ! abdabbs Classifieds | Buy, Sell, Swap 8 01-27-2005 08:24 PM

» Virginia Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 10:19 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.