Numerical Comparison of Thermal Comfort and Air Age Between Two Combined Ventilation Systems with Chilled Ceiling Considering Occupant Density

Abstract

The ability of the chilled ceiling combined with mixing ventilation and personal ventilation system (CC/MVPV) to provide comfort and protect occupants from negative pollutants in an office room in Iraq City-Hilla climate (hot and dry climate) was studied considering the occupied density. A transient 3D computational fluid dynamics (CFD) model was used to evaluate the mean air life, temperature distribution, carbon dioxide concentration and thermal efficiency with the best flow rate of the proposed system and compared with the mixing ventilation and chilled ceiling (CCMV) by using AIRPAK software. Three tests were conducted for three different cooling load cases treated with (25, 50, and 80%) cooled ceiling with a total cooling load of (14.8, 29.6, 47.4) W/m 2 of floor area. The chilled ceiling surface temperature ranged between (23, 21.39, 19)℃ and the mixing ventilation supply air temperature (19, 21, 23)℃ at a constant supply air flow rate (46 L/s) with two PV air flow rate (5 l/s, 7.5 l/s), room air temperature (25℃). It was discovered that by using a (CC/MVPV) system with an air flow rate (7.5 L/sec), the air quality in the breathing area can be improved based on the values of air exchange efficiency (ɳa) and air distribution performance index (ADPI), which are (72%, 89.9) respectively, the efficiency of air exchange (ɳD) when the visiting person (the person standing) stays in the room for an one hour, one and half hour , two hours by (99%, 96%, 94%), so we notice the longer he stays, the less the air change for the passengers due to the low ventilation rate.