Conductive Heat Transfer
Definition
Transfer of thermal energy through a solid material by molecular vibration. Rate depends on thermal conductivity, temperature gradient, cross-sectional area, and path length.
- Mechanism
- Molecular vibration through a solid
- Depends on
- Thermal conductivity, temperature gradient, area, path length
- Medium
- Solid materials
- Field
- Fire chemistry and combustion
Common questions
How does conductive heat transfer factor into a fire investigator's reconstruction of a fire's spread?+
Conduction explains how heat moves through a wall, pipe, or structural member to ignite material on the far side or in an adjoining space without direct flame contact, which is relevant when investigators find a secondary ignition point that cannot be explained by radiant or convective heat alone and needs a conductive pathway through a connecting material.
Why is conduction usually considered less significant than convection or radiation in open fire spread within a room?+
Air and combustion gases are poor conductors, so within open space convection (moving hot gases) and radiation (direct heat transfer through space) dominate fire spread, while conduction becomes the controlling mechanism mainly at material interfaces and through continuous solid elements like structural steel or metal ducting.
Related terms
- Arrhenius Equation
- Mathematical expression relating reaction rate to temperature: k = A × exp(-Ea/RT). The exponential dependence explains the self-accelerating nature of combustion as...
- Auto-Ignition Temperature
- The minimum temperature at which a material ignites spontaneously without a pilot flame or spark. Relevant to the assessment of ignition scenarios...
- Carboxyhaemoglobin (COHb)
- The compound formed when carbon monoxide binds to haemoglobin at the oxygen-binding site, with an affinity 200-250 times greater than oxygen. Produces...
- Convective Heat Transfer
- Transfer of heat by bulk movement of a fluid (gas or liquid). In compartment fires, the buoyant hot gas plume carries most...
- Fire Tetrahedron
- The model of sustained combustion requiring four concurrent elements: fuel, oxidiser, heat, and an uninhibited radical chain reaction. Replacing the older fire...
- Flaming Combustion
- Gas-phase oxidation of volatile pyrolysis products above the fuel surface, producing a visible flame at 800-1200°C. Produces less CO than smouldering under...
- Flash Point
- Lowest temperature at which a liquid gives off enough vapour to form an ignitable mixture in air, but the vapour does not...
- Glowing (Smouldering) Combustion
- Surface-phase oxidation of solid char without a gas-phase flame, typically at 400-700°C. Produces large amounts of CO and can persist at lower...
- Radiative Heat Transfer
- Transfer of heat by electromagnetic waves (infrared). Scales as the fourth power of absolute temperature; at near-flashover temperatures it can simultaneously ignite...