Energy and defrosting contributions of preheating cold supply air in buildings with balanced ventilation. (5th January 2019)

• Record Type: Journal Article
• Authors: Nourozi, Behrouz; Wang, Qian; Ploskić, Adnan
• Is Part Of: Applied thermal engineering. Volume 146(2019)
• Page Start: 180
• Page End: 189
• Publication Date: 2019-01-05
• Subjects: Balanced ventilation -- Heat recovery efficiency -- Defrosting reduction -- Wastewater heat recovery -- Multi-family buildings -- Energy saving; Heat engineering -- Periodicals; Heating -- Equipment and supplies -- Periodicals; Periodicals; 621.40205
• DOI: 10.1016/j.applthermaleng.2018.09.118
• Languages: English
• ISSNs: 1359-4311

Abstract

Highlights: A ventilation air preheating system using residential wastewater is presented. A temperature dependent profile for heat recovery efficiency is utilized. The heat recovery efficiency of MVHR is the dominant factor. Preheating inlet air decreases defrosting need during coldest months by 30–50%. Abstract: Residential wastewater is a constant and available source for saving energy. This paper mainly investigated the possibility of utilizing wastewater heat to reduce ventilation heat load. Swedish residential buildings are to a significant extent served by mechanical ventilation with heat recovery (MVHR) systems. MVHR in airtight buildings has greatly reduced ventilation heat loads, especially in cold climate countries such as Sweden. However, cold outdoor air might lead to frost formation in heat recovery exchangers which increases the energy use. Therefore, this study focused on reducing the defrosting need by preheating the incoming cold outdoor air to MVHR during the coldest days. The effects of preheating the incoming air to MVHR on ventilation heat load and annual ventilation heating demand were also studied. It was found that the heat recovery efficiency of MVHR is the most decisive factor in rating the performance of the combined system with an air preheater. Contributions of the studied air preheater to annual energy savings were negligible. On the other hand, the reduction of the initial defrosting need was significant. The obtained results showed that the defrosting need in a building located in central Sweden in two cases of an MVHR system equipped with a rotary heat exchanger/plate heat exchanger was eliminated/reduced to one-third. The defrosting need was reduced by 50% in northern Sweden for both cases.