ASHRAE ASHRAE Thermal Comfort and Heat Transfer 1 — Questions and Answers
Question 1: According to ASHRAE Standard 55, what is the primary metric used to define thermal comfort?
- Predicted Mean Vote (PMV) (Correct answer)
- Dry-bulb temperature only
- Relative humidity only
- Mean Radiant Temperature (MRT) only
Correct answer: Predicted Mean Vote (PMV)
ASHRAE Standard 55 uses Predicted Mean Vote (PMV) as the primary index to predict the mean thermal sensation of occupants on a seven-point scale.
Question 2: Which of the following is NOT one of the six personal and environmental factors in ASHRAE's thermal comfort model?
- Outdoor ambient temperature (Correct answer)
- Metabolic rate
- Clothing insulation
- Air speed
Correct answer: Outdoor ambient temperature
ASHRAE's thermal comfort model uses metabolic rate, clothing insulation, air temperature, radiant temperature, air speed, and humidity—not outdoor ambient temperature.
Question 3: What does the term 'operative temperature' represent in ASHRAE thermal analysis?
- Average of air temperature and mean radiant temperature (Correct answer)
- Dew point temperature of the supply air
- Effective temperature including humidity effects
- Dry-bulb temperature at the thermostat sensor
Correct answer: Average of air temperature and mean radiant temperature
Operative temperature is the uniform temperature of an enclosure that would result in the same heat exchange by radiation and convection as the actual non-uniform environment.
Question 4: In ASHRAE conduction heat transfer calculations, what does the R-value of a building assembly represent?
- Thermal resistance per unit area (Correct answer)
- Thermal conductance per unit area
- Heat flux through the assembly
- Overall heat transfer coefficient
Correct answer: Thermal resistance per unit area
R-value is the thermal resistance per unit area (ft²·°F·h/Btu in IP units) and indicates how strongly a material resists conductive heat flow.
Question 5: Which ASHRAE Handbook volume is the primary reference for fundamental heat and mass transfer principles?
- ASHRAE Handbook – Fundamentals (Correct answer)
- ASHRAE Handbook – HVAC Systems and Equipment
- ASHRAE Handbook – Refrigeration
- ASHRAE Handbook – HVAC Applications
Correct answer: ASHRAE Handbook – Fundamentals
The ASHRAE Handbook – Fundamentals covers thermodynamics, heat transfer, psychrometrics, and fluid mechanics that underpin all HVAC&R design.
Question 6: What is the purpose of the ASHRAE 'adaptive comfort model' in Standard 55?
- To allow higher temperature ranges in naturally ventilated buildings based on outdoor conditions (Correct answer)
- To reduce mechanical cooling energy in all commercial buildings
- To set stricter comfort limits for spaces with high occupant density
- To define minimum ventilation rates for acceptable indoor air quality
Correct answer: To allow higher temperature ranges in naturally ventilated buildings based on outdoor conditions
The adaptive comfort model in ASHRAE 55 allows a wider acceptable temperature range in naturally conditioned spaces because occupants adapt behaviorally to outdoor climate variations.
ASHRAE ASHRAE Thermal Comfort and Heat Transfer 1
According to ASHRAE Standard 55, what is the primary metric used to define thermal comfort?