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Flashcards in Environment 1 Deck (15):
1

Heat

  • The heating, cooling or lighting of a building is done by adding or removing heat energy
  • Heat is the energy transferred between 2 materials as a result of the temperature differences between them
  • In the UK, 47% of all GHG Emissions come from buildings
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2

Sensible Heat

  • Sensible Heat is a function of temperature, eat capacity and mass
  • Sensible Heat affects the temperature of a material, but not its volume or pressure
  • Its measured in degrees celsuis

3

Latent Heat

  • Latent Heat is the energy needed to cause a phase change in material e.g. freezing, melting, vapourising or condensing
  • It is measured in Kilo Joules per Kilogram (KJ/Kg)

4

Radiant Heat

  • Radiant Heat is the transfer of energy rom an emitting heat source to an object
  • Warmth from the Sun is the most common example
  • The amaount of radiation is inversely proportional to its wavelength
  • The shorter the wavelength, the greater the energy content

5

Thermal Transfer

There are 3 key methods of Thermal Transfer:

 1.  Conduction:

  • If one object has a greater amount of molecular movement than the other, this more intense motion will be transferred to the cooler object

 2.  Convection:

  • Convection is the form of heat transfer in liquids and gases
  • As the volume of the gas increases with temperature, warmer areas have less mass than cooler areas- thus forcing the heat to rise

 3.  Radiation:

  • Radiation is heat energy in transit as electromagnetic waves
  • A Thermogram measures infrared radiation emitted by objects an is exceptionally useful in identifying heat loss

 

6

Thermal Transfer:

Energy Matter Transmission

  • Transmittance: When radiation passesthrough a building material
  • Absorptance: When the radiation is absorbed and heats up the material
  • Reflectance: When radiation reflects off of a surface
  • Emittance: When radiation is given off by a surface

7

Thermal Transfer:

Heat Capacity

  • Definition: The amount of heat required to raise the temperature of a material by 1°C 
  • Generally, heavier materials have higher Heat Capacities
  • The greater the Heat Capacity of a building, the better suited it is to storing energy in the building envelope

8

Thermal Transfer:

Thermal Mass and Insulating Mass

Thermal Mass:

Materials with good Thermal Mass are those that can absorb heat, store it and then release it at a later time.

Insulating Mass:

Mass can be used to regulate heat; in hot, arid regions, thick walls are often used to insulate against heat.

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9

Passive Solar Design:

The Greenhouse Effect

  • Solar Radiation has a short wavelength, so it is easily transmitted through glass
  • When it is reflected off of the internal surfaces it because Longwave Thermal Radiation
  • Glass obstructs Longwave radiation so the heat becomes trapped

10

Passive Solar Design:

Principles

All passive solar heating systems have at least two elements:

  1. Collector (Usually South-Facing)
  2. An Energy Storage or Temperature Mediating Element usually comprising of layers of thermal mass and insulation

 

 

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11

Sun Spaces

Definition: A space intended to capture passive olar energy

Day Time Use: During the day, the Sun Space collects Solar Radiation and distributes heat to the rest of the building

Night Time Use: At night, the Sun Space must be sealed from the rest of the building. Heat is released by Thermal Mass and retained by Thermal Insulation

12

Passive Cooling

  • Arid Zones: often exhibit high diurnal temperature swings prompting the use of thermal mass as a temperature regulator
  • Tropical Zones: are much more reliant on ventilation for mitigation of heat 
  • Temperate Zones: sometimes require cooling in the summer months and also to mitigate solar gain from south glazing and internal gains

13

Passive Cooling:

Venturi Effect

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14

Passive Cooling:

Bernoulli Effect

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15

Passive Cooling:

Cooling Tower

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