7. Air Distribution and Ventilation Effectiveness in a Room with Floor/Ceiling Heating and Mixing/Displacement Ventilation

The present study investigated different combinations of floor/ceiling heating with mixing/displacement ventilation and their impacts on the indoor air distribution and ventilation effectiveness. Measurements were performed in a room during heating season in December. The results show that indoor vertical air temperature differences and air velocities for different hybrid systems are less than 3 °C and 0.2 m/s when supply air temperature is 19 °C, air change rate is 4.2 h⁻¹, and heated surface temperature of floor/ceiling heating system is 25 °C. Ventilation effectiveness of mixing ventilation system combined with floor/ceiling heating systems is approximately equal to 1.0, and ventilation effectiveness of displacement ventilation system combined with floor/ceiling heating systems ranges from 1.0 to 1.2. The floor/ceiling heating systems combined with mixing ventilation system have more uniform indoor air distribution but smaller ventilation effectiveness compared with the floor/ceiling heating systems combined with displacement ventilation system. With regard to the building heat loss increased by non-uniform indoor air distribution and small ventilation effectiveness, there should be an optimal combination of floor/ceiling heating with mixing/displacement ventilation to have the minimal building heat loss.