How many BTU's are needed...

Craig Bergman_2

I posted this last Friday, then had to go to Wisconsin for the weekend. When I checked back it had fallen off the bottom of the Wall.

In a 5000 Gal tank insulated to R-28 (top, bottom and side)how many BTU's are need to bring Soy Wax up 30 Deg. (over a about a ten hour period.) and maintain it at 140 Deg.
The heat transfer properties of the wax are nearly the same as water, a bit better says the manufacturer.

Thank You;
Craig

Einsiedler

my Guess

8.33gpm (5000gal/10hrs/60mintutes)x 30F rise x 500.72 = 125,130 btu

this would bring up & maintain temp, NOT taking into account the delta-T on the tank itself. tank sitting outside? how cold?, surface area of tank?.

also assumng the Soy is STARTING out @ 110F (30 F less than your 140F requirement)

Craig Bergman_2

The tank...

Will be inside (70 Deg year round). It is 9 Ft. in diameter and 9 Ft. tall.

Craig

Mike T., Swampeast MO

Previous reply

http://www.hvac-toolbox.com/38_286.html

Not the best table. No ambient temperature. Insulation listed in inches, not actual values.

ALWAYS VERIFY MY MATH! I do this quick and when I make a simple math error I tend to do it over and over and not see it...

But...assuming product is 8' deep in the tank:

64 sq.ft. surface looses about 64 * 160 = 10,240 btu/hr @ 140° via radiation. Water has emissivity of about 0.96. Couldn't find values for wax but did find reference that a crayon has extremely high emissivity... At least with the 0.96 value there's not much chance that the wax would loose more heat via radiation...

226 sq. ft. of wall surface (again product 8' deep) looses about 226 * 12 = 2,712 btu/hr. This using the 3" thick insulation column.

Since wax isn't evaporating at 140° I did not include evaporative loss. I'm presuming that the tank is filled with pure product--not scented or with other things that WOULD evaporate!

10,240 + 2,712 = 12,952 btu/hr STANDBY heat loss.

For the heat required to raise the product to usage temp you REALLY need to know the actual specific heat of the type of wax involved. Specific heat of paraffin wax is 0.69 but since you said "very similar to water" will use specific heat of water (1.0) to make the REALLY easy.

To raise each pound of product 20°F you need to add 20 btu. If done over a period of 10 hours you would need to add 2 btu/hr for each pound.

JudeNY

Your old thread is out there

There's a big history out there. I used the search feature and got treads going back to 2002. It's out there somewhere and you can get to it if you can remember some words you entered originally.

Uni R

Searching

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