Strategic optimisation of the regulation of air moisture through ventilation systems to reduce energy demand for humidifiers and dehumidifiers

Status

completed

Summary

The use of ventilation systems is very common nowadays. In museums and exhibition rooms, they are used to guarantee the optimal temperature and humidity conditions for valuable and irreplaceable objects. Ventilation systems are increasingly used even in residential and office buildings. In Austria and other similar climates, winter outdoor air is very dry. Because of the constant air exchange using a ventilation system, the relative humidity of indoor air is often lower than the comfort limit, so that air humidification is necessary. In the same rooms, air must be dehumidified during the summer months. Humidification and dehumidification should be minimized as they are processes that consume a large amount of energy.

Three approaches have been examined in a research project to reduce humidification/dehumidification energy consumption:

1. moisture storage (absorption and emission of moisture-peaks),
2. air flow control optimization and
3. moisture recovery by the ventilation system.

A model was developed to illustrate both the microscopic and macroscopic hysteresis of moisture storage, and transport capacities of fibrous materials. The necessary parameters for the model have been obtained using measurements from a number of different materials that were used as humidity buffers. Precise equipment to measure humidity was constructed, tested, and used over a very long measurement period, during which detailed measurements of moisture absorption and emission were measured from different types of fibreboard sheets. The simulations generated by the model showed very good agreement with the measured results.

In addition the details about performance of individual components (material characteristics), it is necessary to know the properties the whole room/building, taking into account different uses. For the validation of coupled room and building component simulations, an analytical solution of this unsteady problem was developed. Finally, a simplified method for determining the humidification and dehumidification demands considering a room’s effective moisture capacity was developed. The developed model will be used for the calculation of the energy balance and will be integrated into the program for energy certification in Austria.

Project management

Ao.Univ.Prof. DI Dr. Thomas Bednar
TU Wien, Institut für Hochbau und Technologie, Forschungsbereich für Bauphysik und Schallschutz

Project collaborator

• Dipl.-Ing. Radoslav Hanic
• Dipl.-Ing. (FH) MSc Tamara Holzer
• Dipl.-Ing. Manfred Grüner
• Dipl.-Ing. Dr. Azra Korjenic

TU Wien, Institut für Hochbau und Technologie, Forschungsbereich für Bauphysik und Schallschutz

Ao.Univ.Prof. DI Dr. Thomas Bednar
TU Wien, Institut für Hochbau und Technologie, Forschungsbereich für Bauphysik und Schallschutz
Adolf Blamauerg. 1-3
1030 Wien
Tel.: +43 (1) 58801 - 206 50
E-Mail: thomas.bednar@tuwien.ac.at
Web: http://www.bph.tuwien.ac.at