Re: [EnergyPlus_Support] RE: Fireplace and wood-burning stove

[Adil SMH <smhadil78@xxxxxxxxx>]

Dear Pascalis,

In the given modeling circumstances, I would have done the following things.

Since the model involves heat rates for both kind of fire equipment, spatial distribution of temperature, convective mixing and material heat capacities, fire intensity regulation and may be some burning material lapse rates etc. I would have solved this situation in CFD first (NIST FDS6 with Large Eddy simulation techniques may model bouncy driven flow very well and can be used for this situation). This would have allowed me to find out an equilibrium situation of internal temperature and ventilation parameters such as exhaust air rates and chimney ventilation due to both kinds of the heat sources in the room.

Now, once the model is set up, it can be solved for minimum time required to reach equilibrium situation in the room for a give outside weather conditions. This equilibrium situation depicts a condition when the zone temperature is neither reducing nor increasing, therefore steady state natural ventilation through chimney and zone temperatures are realized. If your location minimum temperature is -20 C and you are designing for 20 C comfort temperature, then you solve the CFD model for total of eight outside weather conditions. Such as -20,-15, -10,-5,0,5,10 and 15 (C). Thereafter for each of this outside temperature you may like to note down the steady state ACH of the space and exhaust air temperature, inlet air temperature you ready know. (The wood burning rate you have already adjusted to reach comfort temperatures)

The above analysis will lead to development of correlation or you may call hypothetical curves representing the transient performance of each fire model for wood requirement, zone ventilation, zone equilibrium temperature and wood burning energy production rates.

Now, there are many way you can fit it to energy plus existing equipment curves like radiant panels, baseboard heater, or a look-up table matrix etc. But the best way in my opinion is creating an EMS function.

For EMS usage you may have to provide zone temperature sensors and store it in one of your declared variable. Now, use that variable temperature output to regulate you fire place and stove output, which you would have already either fitted in some equations or a kind of Look up table for EMS usage. There after your EMS function must give you things like wood charging rate and total ACH at any particular time.

Remember your Energy plus model will have everything like occupancy, internal heat gains, infiltration etc. like a normal model. But you will be solving this without any other space heating equipment like fan coils or baseboard etc. The concept is to reach equivalent natural internal temperature and use that temperature in the EMS function to find out how your Wood model behaves. You may aggregate and plot it to find out total wood usage in both the cases.

The above illustration is just a hypothesis written only to open new way to evaluate the problem. The credibility and the effectiveness is not guaranteed. You may require further refining of the ideas and logics explained above. 

 

 

SMH Adil 

Simulation Specialist - Built Environment

Certified Energy Manager, Founding Member IBPSA, INDIA

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On Monday, 25 November 2013 3:28 PM, "p_vavalos@xxxxxxxx" <p_vavalos@xxxxxxxx> wrote:

 

Really thank you for sharing your ideas with me ! If anything more comes to mind, i would be glad to hear it.

Kind Regards,

Paschalis Vavalos

---In energyplus_support@xxxxxxxxxxxxxxx, <eglyon@...> wrote:

To simulate the wood burning, you are going to have to construct a detailed pattern of heat output from the wood device.  Some of the heat will be radiant and some will be convective.  Recommended cast iron stove temperature is 400F to 500F maximum.  You may be able to start a fire, but have limited control over adjusting the heat output (my airtight stove does have a draft regulator that responds to the stove temperature), so the space may be over or under heated depending on exterior conditions and fire status.  An important consideration can be heat storage in mass masonry elements and radiation from stove pipes in the occupied space.  For an open fireplace, you will need to have infiltration sufficient to satisfy the chimney draft, but some stoves fireplaces include combustion air connections to outside.

 

I suggest that you research wood heat sources more before attempting a model.  Many manufacturers have detailed information about heat output from their products.  You will likely need EMS logic or a highly detailed schedule to complete your analysis?.

 

Ned Lyon, P.E. (MA, WV)
Staff Consultant

SIMPSON GUMPERTZ & HEGER
781.907.9000 main
781.907.9350 direct 
617.285.2162 mobile 
781.907.9009 fax
www.sgh.com

 

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Oscar Hernandez
Sent: Thursday, November 21, 2013 11:00 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: RE: Re: [EnergyPlus_Support] Fireplace and wood-burning stove

 

 

Hi Pascalis

I simulated one time a wood boiler as a radiant system. In practice is the same. The results that I had were not so bad compared with another software. My advise is try to simulate as a radiant system. Take only count the radiant distribution over the walls.

Good luck

Oscar

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