Introduction to Fire Dynamics

Introductory fire dynamics calculations and concepts.

Introduction to Fire Dynamics - Fundamental fire behavior calculations.

This module provides fundamental equations and calculations for understanding fire behavior, ignition processes, and compartment fire dynamics.

Chapter 6 - Ignition Processes

Chapter 6 - Ignition processes.

This chapter provides equations for analyzing ignition of materials under various thermal conditions.

Equation Modules

Equation 6.32 - Time to Ignition for Thermally Thick Materials

Equation 6.32 - Time to ignition for thermally thick materials.

Provides calculation for ignition time under constant radiative heat flux.

ofire.introduction_to_fire_dynamics.chapter_6_intro.equation_6_32.time_to_ignition_thermally_thick(k, rho, c, temp_ig, temp_o, q_r)

Calculate time to ignition for thermally thick materials (Equation 6.32).

This equation calculates the time required for ignition of a thermally thick material under constant radiative heat flux.

\[t_{ig} = \frac{\pi}{4} \cdot k \cdot \rho \cdot c \cdot \frac{(T_{ig} - T_0)^2}{q_r^2}\]

where:

  • \(t_{ig}\) is the time to ignition (s)

  • \(k\) is the thermal conductivity (W/m·K)

  • \(\rho\) is the density (kg/m³)

  • \(c\) is the specific heat capacity (J/kg·K)

  • \(T_{ig}\) is the ignition temperature (K)

  • \(T_0\) is the initial temperature (K)

  • \(q_r\) is the radiative heat flux (W/m²)

Parameters:

  • k (float) – Thermal conductivity (W/m·K)

  • rho (float) – Density (kg/m³)

  • c (float) – Specific heat capacity (J/kg·K)

  • temp_ig (float) – Ignition temperature (°C)

  • temp_o (float) – Initial temperature (°C)

  • q_r (float) – Radiative heat flux (W/m²)

Returns:

Time to ignition (s)

Return type:

float

Assumptions:

To be completed

Limitations:

To be completed

Equation 6.33 - Time to Ignition for Thermally Thin Materials

Equation 6.33 - Time to ignition for thermally thin materials.

Provides calculation for ignition time of thin materials under constant radiative heat flux.

ofire.introduction_to_fire_dynamics.chapter_6_intro.equation_6_33.time_to_ignition(rho, c, tau, temp_ig, temp_0, q_r)

Calculate time to ignition for thermally thin materials (Equation 6.33).

This equation calculates the time required for ignition of a thermally thin material under constant radiative heat flux.

\[t_{ig} = \rho \cdot c \cdot \tau \cdot (T_{ig} - T_0) \cdot \frac{1}{q_r}\]

where:

  • \(t_{ig}\) is the time to ignition (s)

  • \(\rho\) is the density (kg/m³)

  • \(c\) is the specific heat capacity (J/kg·K)

  • \(\tau\) is the thickness (m)

  • \(T_{ig}\) is the ignition temperature (K)

  • \(T_0\) is the initial temperature (K)

  • \(q_r\) is the radiative heat flux (W/m²)

Parameters:

  • rho (float) – Density (kg/m³)

  • c (float) – Specific heat capacity (J/kg·K)

  • tau (float) – Thickness (m)

  • temp_ig (float) – Ignition temperature (K)

  • temp_0 (float) – Initial temperature (K)

  • q_r (float) – Radiative heat flux (W/m²)

Returns:

Time to ignition (s)

Return type:

float

Assumptions:

To be completed

Limitations:

To be completed

Example

>>> import ofire
>>> result = ofire.introduction_to_fire_dynamics.chapter_6_intro.equation_6_33.time_to_ignition(1190.0, 1420.0, 0.001, 573.0, 298.0, 20000.0)
>>> print(f"{result:.5f} s")

Chapter 10 - Compartment Fire Dynamics

Chapter 10 - Compartment fire dynamics.

This chapter provides equations for analyzing compartment fire behavior and determining burning regimes.

Equation Modules

Equation 10.18 - Ventilation Parameter and Burning Regime

Equation 10.18 - Ventilation parameter and burning regime determination.

Provides calculations to determine compartment fire burning regimes.

ofire.introduction_to_fire_dynamics.chapter_10_intro.equation_10_18.calculate(rho, g, a_w, h, a_f)

Calculate the ventilation parameter for compartment fires (Equation 10.18).

This equation calculates a dimensionless parameter used to determine the burning regime of a compartment fire.

\[N = \frac{\rho \sqrt{g} A_w \sqrt{H}}{A_f}\]

where:

  • \(N\) is the ventilation parameter (dimensionless)

  • \(\rho\) is the density of air (kg/m³)

  • \(g\) is the acceleration due to gravity (m/s²)

  • \(A_w\) is the area of window/vent opening (m²)

  • \(H\) is the height of window/vent opening (m)

  • \(A_f\) is the floor area (m²)

Parameters:

  • rho (float) – Density of air (kg/m³)

  • g (float) – Acceleration due to gravity (m/s²)

  • a_w (float) – Area of window/vent opening (m²)

  • h (float) – Height of window/vent opening (m)

  • a_f (float) – Floor area (m²)

Returns:

Ventilation parameter (dimensionless)

Return type:

float

Assumptions:

To be completed

Limitations:

To be completed

ofire.introduction_to_fire_dynamics.chapter_10_intro.equation_10_18.heating_regime(number)

Determine the burning regime based on ventilation parameter (Equation 10.18).

This function determines whether a compartment fire is ventilation-controlled, fuel-controlled, or in a transition regime based on the calculated ventilation parameter.

Regime Classification:

  • Ventilation Controlled: N < 0.235

    Fire is limited by available air/oxygen supply

  • Transition/Crossover: 0.235 ≤ N ≤ 0.290

    Fire is in a transitional state between ventilation and fuel control

  • Fuel Controlled: N > 0.290

    Fire is limited by available fuel, adequate ventilation exists

Parameters:

number (float) – Ventilation parameter (dimensionless)

Returns:

Burning regime classification

Return type:

str

Assumptions:

To be completed

Limitations:

To be completed