I recall sometime back in the days of the 1970's oil embargo that
open fireplaces are actually a net negative on a house's air
temperature because all the hot air goes up through the chimney as
well as sucking out air from the space (to be made up by outdoor
air entering through infiltration and opened windows). This is
why a small industry developed in the US to retrofit open
fireplaces with enclosed inserts that are actually stoves.
I would think the main benefit of an open fireplace is not in
heating the space, but the radiant heat provided to the people
sitting around the fire, so I would model a fireplace as a radiant
heater, and heavily discount the heating of the indoor air. But
how then would you model its operations and the benefit on
occupant comfort? Assume they're all clustered around the
fireplace?
But before doing anything, I would do a literature search, as I can't believe that nobody had done a thermodynamic model of an old-fashioned fireplace!
Joe
Joe Huang White Box Technologies, Inc. 346 Rheem Blvd., Suite 205A Moraga CA 94556 yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx http://weather.whiteboxtechnologies.com for simulation-ready weather data (o) (925)388-0265 (c) (510)928-2683 "building energy simulations at your fingertips"
Dear Florence,That strikes me as something the EnergyPlus developers never envisioned and it won't be a simple modeling procedure!
If I were to attempt it, I would do something like:
- Determine the schedule for fireplace operation, including frequency and duration of use.
- Determine how to represent the intensity of the fire (e.g., starts slowly, builds and then tapers)
- Determine the predominant type of wood (hardwoods like oak have more energy content than softwoods like pine, but burn more slowly)
- If it's an open fireplace, determine whether there is a flue damper and if it gets closed in between fires - that will affect infiltration.
- Infiltration probably increases during a fire, so consider how to represent that in your model
- Determine the portion of the fire's energy which reaches the occupied space. This is often very small (perhaps 15-20% for an open fireplace), but is dependent on the design of the fireplace. The remainder of the heat goes up the chimney.
I wish you success!
On Tue, Mar 21, 2017 at 6:43 AM, flotimothy@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
I am trying to evaluate the energy performance of an 18th century country house and having difficulty simulating the fireplaces. Just wondering if anyone has done something similar or having information about the way to go about doing that. I will be grateful if i can get feed backs. Thank you Florence
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