electric oven for fun

[Francesco Negrini]

An 'off topic' just for 'fun' pourposes:

Would It be possible to simulate an electric oven in CFAST?

I would create a fire with an area as big as the electric coil, 

an HRR/time curve quite flat, with HRR peak equal to the electric power,  

almost zero soot and CO yields , 

Radiative fraction = 1

I have doubts about the heat of combustion value.

What do you think?

[dr_jfloyd]

You could define a box the size of an oven with walls that approximate the construction of the walls of an oven with ventilation representing those present on an oven. Inside that box you could place a fire with an extremely high heat of combustion (so it doesn't consume any significant amount of oxygen or make any significant amount of combustion products). It is not clear how well this would represent the actual behavior of an electric oven:

-Electric stoves are not purely radiative and setting a radiative fraction of 1 would mean no energy going into the plume. The entire concept of a zone model is built around the idea that the fire plume acts as a pump to move mass from the lower layer to the upper layer.  You would need some small fraction going to convective. 

-The plume equation in CFAST assumes the plume is not confined. The coils in an electric oven covers most of the floor. 

-Electric stoves are controlled by a thermostat and CFAST isn't going to support cycling of the coil based on the internal temperature.

-While radiant heat will heat the walls and those walls will convect heat back into the gas, CFAST will not model any enhancement of the air circulation in the oven that results from this.

[Giancarlo Rossi]

CFAST - Verification and Validation Guide  [Cfast manual Vol. 3 ‐ cap. 4]  recommends the verification of the field of application of the mathematical model.   

In V. V. Guide you read:

- min fire power = 33 kW

- min room height = 2.1 m.

So I think that you can not simulate an electric oven in CFAST.

[dr_jfloyd]

The values in Table 4.13 are the ranges in the various datasets used for model validation. CFAST doesn't suddenly stop working when the room height is 2.09 m. More important is to consider if your scenario is still compatible with the assumptions and equations in CFAST.  Looking at heat release rate and room height as absolute values is not the best approach. Better would be to consider things like the room aspect ratio, the flame height to room height ratio, or the fire area to floor area ratio.