[Bldg-sim] Accumulation stove

[Christian Kaltreider]

Karol,

 

I haven’t modeled such a stove myself, but here are my thoughts for what
they’re worth.  While explicit modeling of an accumulation stove would be
very complex, I think that approximating one in an energy model is
reasonable.  It is essentially just a radiant/convective source of direct
heat in the space, with some sort of fuel input and efficiency associated
with it.  For the discussion below, I’ll assume the fuel is biomass.  

 

If I were doing this I would model it as an electric resistance heater in
the room, with an efficiency applied to it that reflects the average
efficiency of the stove.  I don’t know about other programs, but in TRACE it
is possible to apply an efficiency to electric resistance heating.  Other
programs may assume 100% efficiency for resistance heat, in which case you
would have to do a little bit of additional calculation outside the program.
I would take the heating energy usage calculated by the program and convert
from kWh to lbs of wood or whatever measure of the biomass fuel you choose.
This would require some research on the energy density of the fuel.  

 

There are a few key factors to consider:

 

1.       Efficiency.  In a woodstove, this is a moving target, depending on
how dry the fuel is, how much combustion air is available, how hot the fire
is allowed to burn, and the inherent characteristics of the stove.  In
considering efficiency, you should consider combustion efficiency, latent
heat loss due to moisture in the fuel, and sensible losses up the flue.

2.       Combustion air.  The stove needs combustion air.  This will most
likely come in the form of infiltration into the space.  Wood needs about 12
ft³ of combustion air for each 1000 BTU of input fuel energy.  It is not
unreasonable to expect the stove to use around 100% excess air.  That means
that for every 1000 BTUs of input fuel used, you need to account for about
24 ft³ of infiltration into the space.  

3.       Stove operation.  Will the stove be operated to maintain a steady
indoor temperature 24 hours per day?  If so you can just give the room a
single set point temperature.  If the stove operation will be more
intermittent, you may need to create a temperature set point schedule which
reflects the actual temperature fluctuations in the space.  

4.       Thermal mass.  The mass of the stove serves to even out its heat
output over the course of several hours.  Without modeling the inner
workings of the stove explicitly, I think this effect can be
approximated/estimated using the set point temperature schedule mentioned
above.   

5.       Is there another heating system serving the same space?  If so,
then my suggestions don’t apply as cleanly, if at all.

 

I should say that I’m not a biomass expert.  I’m just interested in the
topic.  The information I provide about wood combustion are based on
documents I’ve read from the Masonry Heater Association and elsewhere.

 

I hope this helps,

Christian

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Karol Bandurski
Sent: Wednesday, October 23, 2013 6:28 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Accumulation stove

 

Dear All,

 

Dou you have some experience with modeling accumulation stove in buildings.

 

I think about stove which is driven by electricity or biomass, similar to
titled stove (attachment).

 

I think about two ways to simulate it:

1)      Zone heat gain,

2)      Walls with temperature as boundary condition (temperature of the
stove surface)

 

What do you think about this idea?

 

There is also issue, how can I model the  heat generation in stove to take
into account accumulation and dependence on biomass burning? 

 

Kind regards,

Karol

 

------------------------------------------------

Karol Bandurski MSc.

 <http://www.ee.put.poznan.pl/> Institute of Environmental Engineering

Poznan University of Technology

 <http://www.put.poznan.pl/~karol.bandurski>
www.put.poznan.pl/~karol.bandurski

www.ee.put.poznan.pl <http://www.ee.put.poznan.pl/> 

 

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