thermal (heat) transfer

Heat transfer

Movement of thermal energy from a higher temperature area to a lower temperature area

Conduction

Heat transfer through direct contact between materials

Temperature gradient

Difference in temperature between two surfaces

Heat transfer through molecular interaction

Energy moves through materials without movement of the material itself

Example of conduction

Animal lying on a cold concrete floor

Factors affecting conduction

Temperature difference, surface area, material thickness, and thermal conductivity

Thermal conductivity

Ability of a material to transfer heat

Concrete conduction

Transfers heat quickly, increasing heat loss

Straw bedding conduction

Transfers heat slowly, reducing heat loss

Convection

Heat transfer between a surface and moving fluid (air or water)

Natural convection

Air movement caused by temperature differences

Warm air behavior

Warm air rises away from animals

Forced convection

Air movement caused by external forces such as fans or wind

Factors affecting convection

Air speed, surface area, and temperature difference

Effect of higher air velocity

Increases heat loss

Radiation

Heat transfer through electromagnetic waves without contact

Infrared radiation

Energy waves responsible for radiant heat transfer

Absolute zero rule

All objects above absolute zero emit radiant energy

Solar radiation example

Sun warming animals

Radiation heat loss example

Animals losing heat to cool barn walls

Emissivity

Ability of a surface to emit radiant energy

Color effect

Dark surfaces absorb more radiation

Wind-chill effect

Increased heat loss caused by moving air

Boundary layer

Thin layer of warm air surrounding the body

Wind-chill mechanism

Wind removes the warm air layer, increasing heat loss

Cold weather risk

Increased energy requirements and cold stress

Wind management

Windbreaks, insulation, reducing drafts