In pool fire source terms, the latent heat of vaporization primarily affects what aspect?

• A. The evaporation rate and vapor generation
• B. The wind speed
• C. The chemical reactivity of the fuel
• D. The color of the flame

Answer: (A)

The main idea being tested is how the energy required to turn liquid fuel into vapor controls how much fuel can feed the flame. The latent heat of vaporization is that energy per unit mass needed to vaporize the liquid at its boiling point. In pool-fire modeling, the rate at which liquid fuel becomes vapor (the evaporation rate and vapor generation) is governed by how much energy is available to the surface relative to this latent heat. For a given heat input to the liquid surface, a fuel with a higher latent heat requires more energy to vaporize each kilogram, so the vapor generation rate is lower. That’s why the evaporation rate—and thus the amount of fuel reaching the flame as vapor—depends on the latent heat of vaporization.

Wind speed is set by air flow and environmental conditions, not by how much energy is needed to vaporize the fuel. The chemical reactivity of the fuel is determined by its composition and temperature, not by latent heat of vaporization. The color of the flame relates to soot formation and combustion conditions, again not the latent heat value.