Heat Transfer Flashcards
Define: Infrared Radiation
Part of the electromagnetic spectrum with a longer wavelength than visible red light. The hotter an object the more infrared it emits.
Define: Dark materials
Absorb more infra-red than light materials
Define: Shiny materials
Poor absorbers and emitters of infra-red radiation
Define: Solid
Particles are in fixed positions and close together. Solids have a fixed volume and keep their shape. Solids cannot flow. Low kinetic energy.
Define: Liquid
Particles are not in fixed positions. Liquids can flow and have a fixed volume but can change their shape. More kinetic energy than solids, but less than gases.
Define: Gas
Particles are not in fixed positions. Gases can flow and do not have a fixed volume or shape. High kinetic energy.
Define: Conduction
Transfer of heat energy through a solid. Metals are good conductors because of free electrons.
Define: Convection
Convection currents form in fluids (liquids and gases) due to changes in density. The heated particles spread out lowering the density. The less dense material rises. As it moves away from the heat source it cools, becomes denser and sinks.
Define: Radiation
Radiation is the transfer of heat without a medium. It is infra-red radiation, part of the electromagnetic spectrum.
Define: Conductor
Conducts electricity. Usually a metal, with lots of free electrons
Define: Insulator
Does not conduct electricity
Define: Evaporation
When a liquid becomes a gas, it takes energy away from the surface giving a cooling effect.
Define: Temperature difference
The greater the temperature difference between an object and its surroundings, the faster the rate of heat energy transfer
Define: U-value
Measures how effective a material is as an insulator. The lower the u-value, the better the material is as an insulator.
Define: Solar panels
Contain water that is heated by radiation from the sun and used to heat buildings or provide domestic hot water.
Define: Specific heat capacity
The amount of energy required to change the temperature of one kilogram of a substance by one degree.
Define: Payback time
The time it takes for the savings you make to cover the cost of installing insulation or an energy source.
Define: Efficiency
Useful energy out divided by total energy in times 100%
Define: Energy types
There are 9: Light, sound, thermal, electrical, kinetic, gravitational potential, chemical, elastic potential, nuclear
Define: Power
The amount of energy (J) transferred by a device in one second. The unit is the Watt (W).
Define: Kilowatt-hour
This is a unit of energy. It is the amount of energy (kW) transferred per hour.
Define: Fossil fuels
Coal, oil and gas. Non-renewable.
Define: Nuclear fuel
Energy from nuclear fission of uranium used to generate electricity.
Define: Biofuel
Energy from animal/human waste used to generate electricity.
Define: Water power
From waves, hydroelectric or tidal
Define: Hydroelectric power
Where GPE stored behind a dam is transferred to kinetic energy of water flowing through pipes with turbines in them.
Define: Solar cell
Converts the sun’s light energy into electricity
Define: Solar panel
Uses the sun’s heat energy to heat water for domestic building heating or hot water.
Define: Geothermal energy
Energy from volcanic areas where hot water and steam rise to the surface.
Define: Small-scale electricity production
Locally useful production of electricity. Useful in remote areas, but sometimes uneconomical to connect to the National Grid.
Define: Carbon capture
Catching and storing of carbon dioxide released in some methods of electricity production. Depleted oil and gas fields are good areas for carbon capture storage.
Define: National Grid
System of cables and transformers which distributes electricity
Define: Step-up transformer
Increases the voltage and decreases the current in the cables of the National Grid to minimise energy wastage
Define: Step-down transformer
Decreases the voltage and increases the current of the electricity supply for business or domestic use
