Smoke ventilation from parking lots

[sahar.rubin]

Hi!

I have a problem with setting transient solver for the expansion of fire in a parking lot.

I reviewed I think any smoke tutorial and guidelines you have and still have some questions:

1. How do I set the transient solver correct and how can I know how much time passes?

For this example lets assume I need to see what happens in 10 minutes after the "car" catches fire.

2. What is the correct wattage needed for the boundary condition of the "car" volume?
Assuming the "car" is a cubic volume as shown at the file attached, who catches fire.

3. Whatever you can add to smoke ventilation and visualization

4. Can you please check the other inputs and give your opinion on the design.

The details for the design (for others also 🙂 ) :

General details:
2000 m^2 parking lot, avrage. Height 3.2m, total volume: 6400 m^3.

For 8 air changes needed -> 2 outlet of 15000 cfm each, one free vent inlet.

Materials:

Ducts, Volume = Air (variable)

"Car" = Resistance (Fire):

     Through Flow K = 0.85

     Normal Direction 1 K = 0.85

     Normal Direction 2 K = 0.85

     Conductivity = 200 W/m*k

     (all constant)

   Flow direction of Fire material picked towards up (Z vector)

Jet Fan Case = Metal (Suppressed)

Jet Fan "Fan" = Custom Internal Fan ("Typhoon"), by sizes and preferences as manufactured:
     Flow = 2.7 m3/s

     Rotational Speed = 0 RPM

     Slip Factor = 1

     (all constant)

   Flow direction towards the front of the jetfan (x and y vectors depend on location in the parking lot)

Boundary Conditions:

"Car" =

     (Volume) Total heat generation 5000 W

        Steady state

        Temp dependent - Disabled (What does it mean???)

     (Surface) Scalar 1, Steady state.

Ducts outlets:

     (Surface) Volume Flow rate 15000 ft3/min each.

     Steady state.

     direction - towards the outside of the volume.

Free Inlet:

     Scalar = 0.

     Pressure = 1.01325e+06 dyne/cm2 (As Environment)

     Temperature = 30 Celsius

Initial Conditions:
Air Volume = Scalar 0

Mesh Size

Auto with adjustments in the fans and ducts (0.6 with uniform and spread)

Solver:

Control:

Main = need your help 🙂
Result Quantities =

    Scalar = on

    Smoke Visibility = On; Parameters:

        Extinction Coefficient = 37000 ft2/lb

        Sign Visibility Constant = 3

        Combustion Particulate Yield: 0.008.

Physics:

Flow = on

     Incompressible.

Heat Transfer = on

Auto forced convection = off

Gravity Direction = 0,0,-1 (-Z here)

Radiation = off

Advanced:

     General Scalar:

            Diffusion coefficient: 0.12 cm2/s.

Sorry for the long question, I just thought others would appreciate it , I looked in many furors and no one really solve this problem...

Thank you SOOOO MUCHH!!!!!!

Sahar Rubin,

Mechanical Engineer.

[Jon.Wilde]

Quick summary of results:

You can use the spreadsheet attached previously to work out the rough visibility. Check your smoke parameters also: