Heat and Human Comfort

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Heat and Human Comfort

• HVAC
• CNST 305
• Environmental Systems 1
• Dr. Berryman

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Heat

• Simple molecular motion
• All matter consist of molecules in constant
  motion at normal temps
• Colder matter has slower rate of motion
• Warmer has faster rate of motion
• Heat Exchange
• When swift moving particles (warm) come in
  contact with slow moving particles (cold), the
  fast molecules slow down and the slow molecules
  speed up

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Principles of Heat Transfer

• Heat energy cannot be destroyed
• Heat always flows from a higher temperature
  substance to a lower temperature substance
• Heat can be transferred from one substance to
  another

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Methods of Heat Transfer
convection
warm air
radiation
cool air
hot water
conduction
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Measuring Heat Quantity
1 lb water
1 Btu
61F
60F
1 kg water
1 kcal 4.19 kJ
16C
15C
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Sensible versus Latent Heat
sensible heat
60F 15.6C
212F 100C
latent heat
212F 100C
212F 100C
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Radiant Heat

• Infrared radiation
• Part of the electromagnetic spectrum
• Similar to light except w/ longer wave lengths
• Not affect by gravity
• Can move in any direction
• shines on surfaces
• Objects receive the radiate energy
• They absorb it
• They convert it to sensible heat (molecular
  activity)

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Examples of Heat Sources

• Computer
• Light fixtures
• Coffee pot
• Sun
• People

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Heat Generated by People
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Surrounding Air Conditions
What makes the body feel comfortable?
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Factors Affecting Human Comfort

• Dry-bulb temperature
• Humidity
• Air movement
• Fresh air
• Clean air
• Noise level
• Adequate lighting
• Proper furniture and work surfaces
• MRT

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Next Time

• The Study of Air/Water Mixtures
• Reading Assignment
• Chapter 2 (Toa)