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Unit 6 |
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Temperature and Heat |
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A transfer of energy usually associated with a
change in temperature. |
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Measured in Btu, calories, kilocalories or
joules |
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A measure of “hotness” or “coldness”. |
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A measure of the kinetic energy of the particles
in a substance. |
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Measured in Fahrenheit, Celsius or Kelvin |
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1 Btu is the energy to change the temperature of
1 lb of water 1 ºF |
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1 cal is the energy to change the temperature of
1 kg of water 1 ºC |
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1 kcal is the energy to change the temperature
of 1 kg of water 1 ºC |
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The amount of heat to change the temperature of
an object depends on: |
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mass |
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type of material (specific heat capacity) |
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temperature difference |
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The specific heat capacity is a property of the
material indicating the ability to maintain a temperature. |
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The heat per unit of mass to change the
temperature 1 degree. |
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cal/g·C |
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kcal/kg·C |
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Btu/lb·F |
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Fusion |
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change between solid and liquid |
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melting or freezing |
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Vaporization |
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change between liquid and gas |
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boiling or condensing |
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Conduction |
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heat transfer by direct contact |
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Convection |
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heat transfer by the movement of mass (fluids) |
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forced convection (fans, pumps) |
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natural convection (warm rises, cold sinks) |
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Radiation |
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heat transfer by electromagnetic radiation
(waves) |
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Assuming no losses or gains to surroundings… |
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Evaporation |
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Sublimation |
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Relative humidity |
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Absolute humidity |
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Diagnostics |
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body uses heat transfer (blood flow) to fight
disease |
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decreased blood flow may indicate blockage |
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Thermography - measures infrared radiation |
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advantage - non-invasive |
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disadvantage - not precise
- may be affected by other heat sources |
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Therapy |
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application of heat |
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conduction - heat pads |
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radiation - heat lamps |
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Notes