Case studies of four installed wastewater heat recovery systems in Sweden

The energy demand for tap water heating is significant in the developed world and significant to buildings energy performance. However, little attention is given to this untapped potential of heat recovery from wastewater. The purpose of this investigation is to investigate performance of different wastewater heat recovery systems to obtain more knowledge on how these systems perform in reality. Four systems were investigated showing that the annual heat recovery ratios between 17 and 43% and annual heat recovery per heat transfer areas between 1586 and 13 108 kWh/m2.The paper also proposes a design equation with a validated accuracy of ±15% for sizing horizontal wastewater heat exchangers in wastewater heat recovery systems