Spatial distribution and transient responses of the thermal environment in an office space equipped with a standing-type air conditioner

Air conditioner (AC) systems are important for maintaining indoor thermal comfort, but discrepancies can exist between setpoints and the actual room temperature. In the present study conducted in a typical Korean office during summer, we identified differences of up to 2.77 degrees C between the AC setpoint and the average room temperature. This variation may have originated from the oscillatory cooling pattern, leading to moments of discomfort even though the overall thermal balance was maintained. While consistent initial cooling rates were observed for various setpoints, oscillations at 20 degrees C lowered the efficiency of the AC system. A bi-exponential model applied to the cooling pattern confirmed a two-phase cooling process. Interestingly, the coefficient of performance was highest at the lowest temperature setpoint, even though this led to greater energy consumption and possible overcooling. The weather strongly affected AC performance, with rainy conditions requiring less power than sunny conditions at the same setpoint. Furthermore, our experiment comparing the predicted mean vote (PMV) with actual human comfort revealed that the PMV often recommends a cooler ambient temperature than what occupants actually prefer.