Coal Usage Per HDD Per 1000 Square Ft

dlj wrote:Have you ever had your coal actually analyzed for BTU content? Or do you just go with a general number? Looking through data sheets on BTU content of different anthracite coals, there is quite a range. But I don't have any handle on how big a range there actually exists in common usage for coal currently commercially available. Will the coal I'm using this winter be close enough to the coal I'll be using next winter? I just have no idea...

dj

I generate new lbs. of coal consumed per HDD figures each year for my new batch of coal. In 4 years this has ranged from 1.32 lbs per HDD to 1.5 lbs. per HDD. Mostly I've been in the range of roughly 1.4 to 1.5 (right now I'm at about 1.41). Only UAE Harmony coal gave me the outstanding 1.32. It is no longer available.

There is no actual need to know the true BTU's per pound, though for convenience I assume a nominal 12,250 for run of the mill typical anthracite "as received" (as opposed to lab dried).

Back when I was all electric (and using my "back-up" resistance boiler instead of my oil boiler for 10 straight years) I was hovering at around 3.45 to 3.5 KWH per HDD. I would say that anthracite has been nearly just as consistent for me, sans for the well renowned Harmony. But then I've only burned straight Blaschak (for one season), a 2 parts Blaschak to 1 part Stockton blend (for one season), Straight Stockton (presently), and straight Harmony (one season). From an energy perspective there is essentially no difference between Stockton and Blaschak. From an ease of burning perspective Blaschak is superior. Harmony was the easiest to burn, but it had some puff-back issues with its high volatiles. Stockton only wants to burn when it is colder outside and the boiler is firing more frequently. Harmony and Blaschak will burn year round. I burn coal year round. By spring my Stockton will be gone and I will be back to Blaschak.

dlj wrote:It's known that fuel consumption is not linear with temperature as you go up and down and I thought you might have done some testing to see. From what you say above, I'd guess you have done a small temperature range which would look linear as you are suggesting. I just don't know how far off linear that falls...

Actually the linear thing was brought up on another thread and it was deemed that it was very linear.

Heat Required as Outside Temp Falls

Liquid thermometers movement with air temperature change is linear. BTU's (by definition) are linear to water temperature for a fixed weight of it being heated (provided there is no phase change). If BTU's are linear to water why not also to air? (granting that air has both a variable moisture component and a varying density component that can alter its specific heat capacity to some degree)

The general BTUH equation for flowing water is:
BTUH = GPM x Delta-T x 500

The general BTUH equation for flowing air is:
BTUH = CFM x Delta-T x 1.08

Both are linear equations and both have the same format. You can even set both formulas as being equal to each other if you want to. I would imagine this is often done for water to air heat exchangers.

You guys familiar with the ASHRAE handbook?

Here's a link where you can down load the 2001 version:

http://systemssolution.net/cadtechno/0%20SAMPLE/S ... ndbook.pdf

I think you'll find it quite useful and informative.

Yes, you can use linear models for what you've been doing and it works rather well. But I think you may be intrigued with what you will find in the above reference.

I hope you enjoy!

dj

Wow! Thanks much for sharing the link! I just downloaded and saved a copy. Roughly 40 years ago (give and take a few) when complex equations (the likes of calculus, differential equations, and linear algebra) were part of my daily education regimen (until I dropped out, idiot that I was back when I was young) I'm sure I could have absorbed and used this reference material far more than my aging and feeble mind (that has not been pressed to use such mathematics much over the years) will do so today, but I'm confident that I will consult this tremendous resource often. I'm surprised that it is available for download.

lsayre wrote:Wow! Thanks much for sharing the link! I just downloaded and saved a copy. Roughly 40 years ago (give and take a few) when complex equations (the likes of calculus, differential equations, and linear algebra) were part of my daily education regimen (until I dropped out, idiot that I was back when I was young) I'm sure I could have absorbed and used this reference material far more than my aging and feeble mind (that has not been pressed to use such mathematics much over the years) will do so today, but I'm confident that I will consult this tremendous resource often. I'm surprised that it is available for download.

Larry,

I'm glad you liked it. You don't really have to "deal" with all the equations, there is plenty of info without having to go there. However, since you have had mathematics then you will be able to understand what is being talked about when the equations are being referenced. I highly doubt the "feeble" mind part... at least not from what I've read on this forum...

You do have to buy the current version (I think it's about $200), but the 2001 version is still quite good. It covers a lot of areas and is a pretty decent general reference book. I'm not aware of another one that covers as much relevant info as this one does with sufficient detail to actually be useful...

dj

dlj wrote:Larry,

I'm glad you liked it. You don't really have to "deal" with all the equations, there is plenty of info without having to go there. ...

That's true. Generally by the end of each section they have done most of the work for you and reduced the equations down to a more workable format. Thanks again!