| I'm very happy to see that the author has included more than one factor in their analysis: > "The main goal of climate controls is to make the passengers comfortable. PO Fanger defines thermal comfort as being influenced by six factors: air temperature, heat radiation, air flow, humidity, activity level, and clothing. The car can control the first four factors." I would like to point out that direct conduction is also extremely important, and that radiation is generally more important than air temperature in daily life. However, it is difficult to directly control conduction and radiation - those are generally changed by changing air temperature. In fact, liquid water is a bigger factor than any of the named factors, but we generally do not try to control how wet a person is with our HVAC systems. Here's one tiny case study: A person is cold, because it is wintertime, and it is cold and overcast outside. Their windows are cold, but do not leak much air. After they pull the curtains closed, they feel warmer because their body is no longer radiating as much heat toward the window (you feel the relative difference in heat radiation). They turn on their home heating system, which increases the temperature, but does not add total humidity. Thus the relative humidity and vapor pressure of water decrease and they perceive that the air has dried out. The home heater raises the air temperature relatively quickly, but their outside walls are cold-soaked and do not heat up quickly - they still feel a chill. They turn on an oil-filled electric radiator. The radiator consumes 1400 Watts, much less than the home heating system (over 5,000 Watts), so it does not change air temperature much; but it does give the person some comfort. They turn on a heating pad on the couch. It only consumes a few hundred Watts, but all of the heat is transmitted directly into the person and they warm up quickly. The person also consumes a hot drink and dries off from the drizzle they walked through. As they dry off, they feel much warmer as their skin is no longer losing heat to water phase change (evaporation). ---- Now, do I expect a car climate system to handle all of that? Not a bit. But we are always telling ourselves simplified stories. The actual story of comfort is very complicated. |