[Stoves] Comparable heat outputs of stoves

[Paul S. Anderson]

Stovers    (sorry for the accidential earlier incomplete sending)

The topic is how much heat is output by stoves, especially "institutional"
stoves.

1.  The unit equivalents:  kcal and BTU and KWthemal and kjoules.  I am at a
loss for comparing them.  I would really like to have a look-up table for quick
comparisons.  Just having formulas of equvalents is not so easy.

Also, I see residential cookstoves called 3 to 5 KWt when at high-heat setting,
and can "visualize" that amount of heat.  Likewise, the large barbeque grills
in the USA have tags saying 30,000 and 40,000 BTU, so I can approximate that
amount of heat (but only in the BTU measurement).

On the institutional size of heat, a baker friend mentioned to me an oven
"heated by an oil burner and the most common size of this [oven] uses close to
max of 5 ltrs per hour., which would be approx 50,000 kcal per hour or 200,000
Btu's."    That would mean 1 liter of fuel oil yields about 10,000 kcal or
40,000 BTUs.  But how does that relate to the KWt that we use for small
cookstoves, and then there is the issue of fuels (below).

Any suggestions for how I (and all non-stover public) can grasp these
measurements?

2.  Now, what about the dry biomass fuels needed to get such heat.  I recall
reading that MOST biomass yields about 8,000 BTU per (was it pound or kilo??). 
And if that is combusted in one hour, then you would need 5 times that much fuel
in one hour to equal the 40,000 BTU barbeque unit.  Can someone help me clarify
this AND give similar (comparable) statements relating to kcal and kjoules and
KWt and BTU, in BOTH pounds and kilos systems???   Personally, I like the
metric system, but I live in America and must confront and understand the
Imperial system also.

Note that we are discussing heat output when combustion is occurring nicely, NOT
discussing the efficiency of a stove/oven to capture that heat.

3.  For simplicity, I hope that we can also have a few solid "benchmarks" about
heat-creating devices that we can use to better classify the heat output of our
stoves.  For example:

1 KWt (which is too weak for a cookstove but can be multiplied by 3 to 5 to then
represent a good cookstove).

1 KWt = ____ BTU  = _____ kcal =  _____ kjoules, results from ____ kilos (0r
_____ pounds) of ________ typical woody biomass or _______ other fuel type and
weight.

OR

50,000 kcal (bakery oven) = _____ (other units), requiring ________ of woody
fuel or ______ (whatever is relevant)

OR

1 kilo of normally dry woody biomass yields .................

********
I hope that someone can point me to where all of this is found.

Part of it is in Alexis Belonio's "Handbook", bottom page 136, says

Heat Flow (or Power):   1 BTU/hr = 0.2931 W,

so I calculate that the 40,000 BTU barbeque would be about 1.2 x 10,000 or 12
KWt, or about the combination of three of the 4 KWt cookstoves.

Heat Flow:   1 watt  = 3.411 BTU/hr

so I calculate that the 4 KWt cookstove would be 14,000 BTU/hr, and would need
about ______ kg or _______ pounds of woody biomass.

But if such a summary is not already available, I hope we can build up something
that is useful.  Ideally, one typed page should be enough for all the needed
info for anyone to consult.

People complain about comparing apples and oranges.  Well, I like both, plus
bananas.  And sometimes I need to compare KWt (apples) and kcal (bananas), and
they come in bushels and bunches as well as pounds, kilos, and tons.

Thanks for listening.  Thanks for helping.

Paul

-- 
Paul S. Anderson, Ph.D., Geography professor - Emeritus
Telephone:  USA-309-452-7072 (residence and office)
Internet site:  www.ilstu.edu/~psanders
For my gasifier stoves info, go to (below) and click on my name:
http://www.repp.org/discussiongroups/resources/stoves/contributions.html

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