Thermal Comfort and Its Factors

Thermal Comfort

• Thermal comfort involves understanding various thermal conditions necessary for human well-being, including solar heat gain and psychrometric principles.
• Achieving thermal comfort contributes to overall health, well-being, mental health, and productivity by preventing heat-related illnesses.
• The human body maintains a constant temperature by balancing heat production and dissipation (radiation, convection, and evaporation).
• Environmental conditions (air temperature, humidity, air movement, surface temperature) affect thermal comfort and human ability to regulate body temperature.

Factors Affecting Thermal Comfort

• Personal Factors: Individual factors such as clothing, activity level, personal preferences, age, and body differences influence thermal comfort.
  • Heat emission increases with higher activity.
    • Sleeping: ~70 W
    • Office work: ~140 W
    • Factory assembly work: ~265 W
    • Heavy lifting work: ~440 W
• Physical Factors: Environmental factors impacting thermal comfort include air temperature, relative humidity, air movement, and surface temperatures.
  • Appropriate air temperature range and humidity is crucial for comfort.
  • Air movement should be between 0.05 and 0.2 m/s and humidity levels should be between 50%-70%.

Criteria for Ideal Thermal Comfort

• Ideal thermal comfort involves maintaining a constant air temperature of 24-26°C, relative humidity between 50-70%, and air movement not exceeding 0.2m/s or below 0.05m/s

Effects of Solar Radiation

• Solar radiation significantly impacts building thermal comfort, affecting the building's interior temperatures.
• Factors like geographic latitude, season, cloud conditions, solar angles, and window types influence solar heat gain.
• Singapore's location near the equator results in high solar radiation levels, significant heat transfer into buildings.

Principles of Psychrometry

• Basic Terms: Explains key concepts related to measuring and controlling humidity, temperature, and moisture content in the air.
  • Dry-bulb temperature (DBT): The temperature measured by a standard thermometer.
  • Relative humidity (RH): The amount of water vapor in the air as a percentage of the maximum amount the air can hold at that temperature.
  • Wet-bulb temperature (WBT): The temperature measured by a thermometer with a wet wick, used to measure the moisture content in the air.
  • Dew-point temperature: The temperature at which air will be saturated and condensation will occurs.

Psychrometric Chart

• A psychrometric chart is a graphical representation of the thermodynamic properties of humid air.
• It displays relationships between dry-bulb temperature, wet-bulb temperature, relative humidity, and moisture content (used for design projects).
• The chart can be used to determine various conditions and how they affect humidity.