How the supply air temperature is calculated in OpenStudio?

asked 2020-04-13 03:33:40 -0500

krwr gravatar image

I'm trying to simulate a simple HVAC system for one thermal zone (office). It consists of DX cooling coil and constant air volume fan. I set a constant air flow to 0.377 m3/s based on cooling load 2.6 kW (gain from people, electric equipment, lights, and solar gain) and temperature difference 6 K.

It looks like the difference between supply air temperature and exhaust air temperature from the thermal zone is calculated based on "Zone Air System Sensible Cooling Rate". I expected the calculation based on the sum of heat gain (people, lights, solar gains, electric equipment, infiltration). What is the difference between "Zone Air System Sensible Cooling Rate" and a simple sum of all heat gains? "Zone Air System Sensible Cooling Rate" is always lower than obtained heat gains so the system sizing seems to be incorrect.

Where am I mistaken in my approach? Link to data plot

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