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Environmental Protection by Elevated Indoor Temperature of Air Conditioning System

Elevated indoor air temperatures in summer are required by East Asia government for reduction of carbon emission. Significant energy saving with good indoor air quality and thermal comfort within the breathing zone can be achieved by stratum ventilation system in buildings in previous studies. It can be applied for improving energy efficiency and building energy performance for new buildings, as well as existing medium size of air conditioning area. Improving energy efficiency in building is a cost- effective measure to address global warming and local air quality concern. This paper is to investigate the thermal comfort of college-age Chinese adolescents under conventional mixing and stratum ventilation operated in a confined environmental chamber during the summer of subtropical Hong Kong. Fortyeight subjects wearing 0.57 clo standard clothing were exposed to several different thermal conditions under sedentary activity for 3 hours. The neutral temperatures at conventional mixing and stratum ventilation mode were found to be 24.6°C and 27.1 °C respectively at supply air flow of 300 l/s (10 air change per hour, ACH) and 24.8 °C and 27.4 °C respectively at supply air flow of 450 l/s (15 ACH). In comparison with mixing ventilation, energy consumptions of stratum ventilation were found to be 11.2% less at 10 ACH and 11.8% less at 15 ACH. Therefore, stratum ventilation can achieve thermal comfort at elevated indoor temperature hence less energy use in the conditioned space. More energy saving in the refrigeration system was also discussed for this stratum ventilation installed in small-to-medium size classroom.