"Feels Like"

Discussions related to psychrometric calculations, humidity and enthalpy, "feels like" temperature, HVAC control strategies, and so on.
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Joined: Tue May 22, 2018 4:17 pm

"Feels Like"

Post by whadmin »

Curious to learn how to model the "feels like" temperature and how it relates to the thermodynamics.

The "edge" cases are where this matters most. For instance, consider the the scenario where it's late spring and the furnace is being used most days. The indoor air is 65°F (the thermostat setting) and dry, say 30%RH. The enthalpy of this indoor air is 19.86 BTU/lb dry air.

Outside, the air is muggy but cool. Let's say it's 58°F and 90%RH. The enthalpy of this air is 23.94 BTU/lb dry air. Since you are paying for energy to heat the air, you should prefer the air with more energy in it. But this would mean opening the windows to let 58°F air in to replace your 65°F air. If you did so, you'd obviously need to run your furnace to warm it up.

Once you'd done so, the new moist air at 65°F would feel warmer than the old dry air.

So the problem is that the set point for the thermostat is a proxy for a "feels like" preference. The thermostat set point really should change based on the humidity level of the air, to achieve and equal perceived comfort. If you like 65°F an 30%, then 65°F and 70% will feel too warm.

So, perhaps the preferences set in AirCompare should assume a reference humidity level such as 50%, and self-adjust for the indoor humidity.

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