Zusammenfassung der Ressource
P.16-19
- Rate of Heat Transfer
- The rate of heat energy transfer depends on many things
- Surface area
- The larger the surface area the faster the rate of heat transfer
- Volume
- The larger the volume the slower the rate of heat transfer
- Type of material
- Objects made from good conductors
transfer heat away quicker
- Some devices are designed to limit heat transfer
- Humans and animals have ways
of controlling heat transfer too
- In the cold, the hairs on
your skin stand up to trap a
layer of air around your body
- This prevents convection
- When you're too warm, your body diverts
blood to flow nearer to the surface of your
skin
- This causes more radiation
- Energy Transfer
- There are nine types of energy:
- Electrical Energy
- Light Energy
- Sound Energy
- Kinetic Energy
- Nuclear Energy
- Thermal Energy
- Gravitational Potential Energy
- Elastic Potential Energy
- Chemical Energy
- These are forms of stored energy
- Energy can be transferred usefully from
one form to another stored or dissipated-
but it can never be created or destroyed
- Energy is only useful when it can be
converted from on form to another
- Specific Heat Capacity
- Specific Heat Capacity tells you how much energy materials can store
- It takes more heat energy to
increase the temperature of
some materials than others
- E = m x c x ϑ
- Energy transferred = Mass x specific heat capacity x temperature change
- J = kg x J/kg°C x °C
- Heaters are designed to have high heat capacities to store lots of energy
- Energy efficiency in the home
- Effectiveness and cost-effectiveness are not the same thing
- The most effective methods of insulation give you the biggest annual saving
- The money you've saved on heating bills will equal the initial cost
- This is the payback time
- The most cost-effectiveness methods tend to be the cheapest
- They have a short payback time
- Cavity wall insulation,
Loft insulation,
Draught-Proofing, Hot
water tank jacket, and
Thick curtains
- U-Values show how fast heat can transfer through a material
- By Stephen Thompson