Total heat transfer = metabolic heat production; ~1kcal/kg/hour
It occurs by
- Radiation (60%)
- Convection (20%)
- Evaporation (20%)
- Conduction (minimal)
Radiation
- Emission of energy as blackbody EM radiation
- Depends only on skin SA and temp gradient with surroundings
Convection
- Conduction to moving fluid (e.g. air or water).
- Depends on surface area, temp gradient, flow rate of fluid, and conductivity / specific heat capacity of fluid (e.g. more heat transfer to water than air)
Evaporation
- Heat loss to latent heat of vaporization of water
- From respiratory tract or sweating
- Determine by rate of sweating, minute ventilation, humidity
Conduction to solids
- Minor role
- Determined by surface area, temp gradient, thermal conductivity / specific heat capacity of solid