[Greenbuilding] Solar Water Heater Veggie Oil

[Keith Winston]

(Veggie oil as heat transfer fluid)
> Certainly should improve pump life.
>
>   
You mean because of lubrication? Circulators don't rely on lubrication 
from their pumped fluid.

To determine if veggie oil was a good heat transfer fluid, you would 
need to know a number of things I don't right know offhand and don't 
have time to find righr now: the volumetric heat capacity (does it carry 
heat well? Water is great!), diffusivity (will it absorb/release heat 
well?), viscosity (how hard is it to pump? How does that change at 
different temperatures?). What happens as it ages, especially in the 
presence of hot/cold cycles and, like it or not, some oxygen (hint: the 
fatty ACID components of most oils can be problematic) -- you can't take 
for granted the "won't corrode the plumbing" piece. There are some 
high-temperature silicon heat transfer fluids that would be amazing in 
solar systems, they can operate at 700F, you could completely ignore 
stagnation, but they suck in certain of those other characteristics 
(though you could potentially get around some, by doubling the size of 
your heat exchangers, for example). Most plant oils consist of a range 
of components, I know soy oil has a whole slew of fatty acids with 
different freezing points and other characteristics.

But it could make for a fun experiment. Keep us posted!

Keith


> On Aug 14, 2006, at 12:49 AM, Chris Green wrote:
>
>   
>> wmdorsett at sbcglobal.net wrote:
>> And I was wondering if perhaps canola oil or some other vegetable oil
>> might work as the heat-transferring medium? It isn't quite as dense as
>> water, but it can withstand temps up to around 360F, and in a closed
>> loop system, it wouldn't be prone to going rancid for a long time. It's
>> also not toxic and won't corrode the plumbing. .
>>
>> Any thoughts on that?
>>
>> Chris Green.
>>     
>
>
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-- 
Keith Winston
Earth Sun Energy Systems
3927 Madison St.
Hyattsville, MD 20781
301-980-6325
keith at earthsunenergy.com
www.EarthSunEnergy.com