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Simulation and Measurement of Energetic Performance in Decentralized Regenerative Ventilation Systems

: Carbonare, N.; Fugmann, H.; Asadov, N.; Pflug, T.; Schnabel, L.; Bongs, C.

Fulltext ()

Energies 13 (2020), No.22, Art. 6010, 25 pp.
ISSN: 1996-1073
Journal Article, Electronic Publication
Fraunhofer ISE ()
Thermische Systeme und Gebäudetechnik; decentralized ventilation; heat recovery; honeycomb heat exchanger; computational fluid dynamics; Modelica; Energieeffiziente Gebäude; Lüftungs- und Klimatechnik

Decentralized regenerative mechanical ventilation systems have acquired relevance in recent years for the retrofit of residential buildings. While manufacturers report heat recovery efficiencies over 90%, research has shown that the efficiencies often vary between 60% and 80%. In order to better understand this mismatch, a test facility is designed and constructed for the experimental characterization and validation of regenerative heat exchanger simulation models. A ceramic honeycomb heat exchanger, typical for decentralized regenerative ventilation devices, is measured in this test facility. The experimental data are used to validate two modeling approaches: a one-dimensional model in Modelica and a computational fluid dynamics (CFD) model built in COMSOL Multiphysics®. The results show an overall acceptable thermal performance of both models, the 1D model having a much lower simulation time and, thus, being suitable for integration in building performance simulations. A test case is designed, where the importance of an appropriate thermal and hydraulic modeling of decentralized ventilation systems is investigated. Therefore, the device is integrated into a multizone building simulation case. The results show that including component-based heat recovery and fan modeling leads to 30% higher heat losses due to ventilation and 10% more fan energy consumption than when assuming constant air exchange rates with ideal heat recovery. These findings contribute to a better understanding of the behavior of a growing technology such as decentralized ventilation and confirm the need for further research on these systems.