Heat Transfer and Conduction

Study Notes

Heat transfer is the transfer of thermal energy from one body or system to another due to a difference in temperature.

Definition: Conduction is the transfer of heat between objects in physical contact with each other.
Mechanism: Heat energy is transferred through the vibration of particles, with faster-moving particles colliding with slower-moving particles, transferring their energy.
Factors affecting conduction:
- Temperature difference
- Surface area in contact
- Material properties (thermal conductivity)
Examples:
- Holding a hot cup of coffee and feeling the heat transfer to your hands
- Metal spoon in a hot soup

Definition: Convection is the transfer of heat through the movement of fluids.
Mechanism: When a fluid is heated, it expands and becomes less dense, causing it to rise. Cooler, denser fluid then moves in to take its place, creating a circulation of fluid known as a convective cell.
Factors affecting convection:
- Temperature difference
- Fluid properties (density, viscosity)
- Gravity
Examples:
- Boiling water, where hot water rises and cooler water sinks
- Ocean currents and atmospheric circulation patterns

Definition: Radiation is the transfer of heat through electromagnetic waves.
Mechanism: All objects emit and absorb radiation, with hotter objects emitting more radiation than cooler objects.
Factors affecting radiation:
- Temperature difference
- Emissivity of objects (ability to emit radiation)
Examples:
- Feeling the warmth of the sun on your skin
- Heating a room with a radiant heater

Definition: Insulation is the reduction of heat transfer between objects.
Purpose: To reduce heat loss or gain, and maintain a consistent temperature.
Types of insulation:
- Material insulation (e.g. fiberglass, foam)
- Air gap insulation (e.g. double glazing)
- Vacuum insulation (e.g. thermoses)
Importance: Energy efficiency, cost savings, and environmental sustainability.

Heat transfer occurs due to a temperature difference between two bodies or systems, resulting in the transfer of thermal energy.

Conduction is the transfer of heat between objects in physical contact with each other.
Heat energy is transferred through the vibration of particles, with faster-moving particles colliding with slower-moving particles, transferring their energy.
Temperature difference, surface area in contact, and material properties (thermal conductivity) affect conduction.
Examples: holding a hot cup of coffee and feeling the heat transfer to your hands, and a metal spoon in a hot soup.

Convection is the transfer of heat through the movement of fluids.
When a fluid is heated, it expands and becomes less dense, causing it to rise, and cooler, denser fluid then moves in to take its place, creating a circulation of fluid known as a convective cell.
Temperature difference, fluid properties (density, viscosity), and gravity affect convection.
Examples: boiling water, where hot water rises and cooler water sinks, and ocean currents and atmospheric circulation patterns.

Radiation is the transfer of heat through electromagnetic waves.
All objects emit and absorb radiation, with hotter objects emitting more radiation than cooler objects.
Temperature difference and emissivity of objects (ability to emit radiation) affect radiation.
Examples: feeling the warmth of the sun on your skin and heating a room with a radiant heater.

Insulation is the reduction of heat transfer between objects.
The purpose of insulation is to reduce heat loss or gain, and maintain a consistent temperature.
Material insulation (e.g., fiberglass, foam), air gap insulation (e.g., double glazing), and vacuum insulation (e.g., thermoses) are types of insulation.
Insulation is important for energy efficiency, cost savings, and environmental sustainability.