Preheating Cold Supply Air to Mechanical Balanced Ventilation using Wastewater or Passive Geothermal Energy

This study investigated the thermal potential of two renewable heat sources, residential wastewater and geothermal energy, for preheating the incoming air to the air-handling unit (AHU) in a multi-family building. The main purpose of preheating the inlet air was to avoid the frost formation inside AHU due to low outdoor temperatures during winter. Wastewater extraction flowrate and temperature, as two design parameters, were studied in detail by employing two types of wastewater storage tanks.