Solar oil heater

[longwolf]

Hey Guys,

I've done a grease car conversion on my diesel van and built a centrifuge for cleaning the oil. The whole setup is mobile and goes with the van.

It's best if the oil is 160F to 200F before it goes into the centrifuge.
The flow rate is a max of seven gallons an hour.

So how small of a passive heater could be made to get the temps needed?
I plan to use it year round.

[Mike90250]

So how small of a passive heater could be made to get the temps needed?
I plan to use it year round.

How long do you want to wait, and how insulated is the storage tank ?

I had to melt a 5 gallon pail of honey, to make a batch of mead, I took and painted it black, set it in the sun, with reflective sun shades from my truck. rock hard, to melted in 4 hours.

[longwolf]

I'm not out to heat the whole barrel.
The idea is to make a box out of 3/4 foam with either a 1/2' or 3/8' copper coil in it.
Then pass the oil from the barrel strait through the heater and into the centrifuge.

I just played around with some of that foam, some scrap plexi and flat back paint. This box is only about 9x12. I was pleasantly surprised when it hit about 220F in just a few mins.

I'm looking to see if it'd be practical to make one for heating the oil. i.e. would there be room in the van for it

Seven gallons an hour is a pretty slow flow, so I think it might work out.

[longwolf]

Ouuh, I almost missed that, mead sounds great!
Have you ever made any apple jack?

[Sunking]

Seven gallons an hour is a pretty slow flow, so I think it might work out.

Well 7 gpm may not sound like a lot to you, but is a heck of a lot of BTU's depending on what temp the oil starts at to get to 200 degrees.

Vegetable oil weighs 7.7 pounds per gallon so 7 gallons weighs 54 pounds. It takes .46 BTU's to raise 1 pound of Veg oil 1 degree F. So if your oil starts at 70 and you want to go to 200 it will take (200 - 70) x 54 x .46 = 3230 BTU's. Well actually quite a bit more when you factor in efficiency and heat losses so educated guess is 4000 BTU's. In terms of electrical energy comes out around 1.2 Kwh

[dvhenry]

It would need to be carefully designed for safety reasons, but have you considered using the heat from the exhaust manifold?

[LucMan]

How about making a heat exchanger out of copper tubing and connecting it to your heater hose lines, that would give you between 170-200 degree water running through the HX while the truck is running depending on your thermostat.

[Naptown]

Well 7 gpm may not sound like a lot to you, but is a heck of a lot of BTU's depending on what temp the oil starts at to get to 200 degrees.

Vegetable oil weighs 7.7 pounds per gallon so 7 gallons weighs 54 pounds. It takes .46 BTU's to raise 1 pound of Veg oil 1 degree F. So if your oil starts at 70 and you want to go to 200 it will take (200 - 70) x 54 x .46 = 3230 BTU's. Well actually quite a bit more when you factor in efficiency and heat losses so educated guess is 4000 BTU's. In terms of electrical energy comes out around 1.2 Kwh

He said 7 gallons per hour not minute.

[longwolf]

He said 7 gallons per hour not minute.

Unfortunately, it looks like he got the formula right.

Sunking, thanks for the formula.

The ideal temp would be over 212 F to boil any water out.
But the centrifuge does a great job of removing it anyway.
The main thing is to get the viscosity down so that the CF is more efficient.
While the CF should be able to handle 250F, one guy says that 130F at a rate of 7 gallons an hour works great.

So that would bring it down to about 1500 BTUs per hour plus any heat losses.

Anyway, I guess I should have asked how long a piece of black painted copper tubing inside a 'hot box' would it take?

I have Tube-in-hose (TIH) heating on the waste oil fuel line. It's about seven feet long with a piece of 3/8th stainless tubing going through an 1 1/8 hot water line.
I haven't insulated those lines yet. I used a probe to measure the temps by touching the fittings while the engine was idling. The water temp was 130F and the fuel line read 110F and that's in just 7 feet!

So it still sounds like this can be done.

[longwolf]

dvhenry and LucMan,
Thanks for the ideas. I originally made a 12v electric heater for it. But the van's barely getting enough power back there to run the CF.
I'd rather not have to run the motor while I process the oil. The CF hangs right by the exhaust pipe.
Also I can't think of a clean, easy and safe way to use either of those methods with this mobile setup.

[Sunking]

He said 7 gallons per hour not minute.

Yeah a typo on my part. Anyway the point is the same with respect to BTU's

[longwolf]

Ok, let's try another angle.
I've read that there's 5KW per square meter of sunlight.
So how efficient is a hot box?

If it was 100%...
1 square meter = 10,000 square centimeters
5 / 1.2 = 4.17
10,000 / 4.17 = 2398
the square root of 2400 = about 49 centimeters per side
In american that's about 19.29 inches square.

[Naptown]

Ok, let's try another angle.
I've read that there's 5KW per square meter of sunlight.
So how efficient is a hot box?

If it was 100%...
1 square meter = 10,000 square centimeters
5 / 1.2 = 4.17
10,000 / 4.17 = 2398
the square root of 2400 = about 49 centimeters per side
In american that's about 19.29 inches square.

It's 1 KW per square meter under ideal conditions and best thermal conversion would be 50-60%

[russ]

Unless you live in a place like Arizona you will almost never see 1000 watts/m2.

Plan on 800 maybe.

Best to use PV Watts or a NASA site for the daily insolation - you should get about 85% of the daily insolation during usable time periods.

[longwolf]

Thanks guys, now I have something I can work with.
Ok, so year round may be out. (Get the idea that I don't give up easily)
And I'll lower expectations to see what it'd take.

I'm not in Arizona, I'm in Texas which is probably close.
Lets say 900 watts/m2.
We're headed for about 3 months where we'll have 100F days and 80F nights.
So figure 90F average starting oil temp.
Instead of 200F, I'll shoot for 130F.
7 gallons at 7.7 pounds per gallon = 54 pounds
(130 - 90) x 54 x .46 = 993.6, call it 1000 BTUs = 293.0711 Watts per hour, call it 300.
I'm an optimist, and I'm willing to go double paned, so say 60% efficient.
500 Watts should do it.

So..
900 / 500 = 1.8
10,000 / 1.8 = 5555.5555 cm squared
the square root of 5555.5555 = 74.535598877315 cm per side
Or 29.34472 inches per side minimum.

Do y'all see any major flaws here?