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Energy Efficient Climatization for Rooms with Cooling Demand: -based on a Concept with Displacement Ventilation and Low Supply Air Temperature
Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, Department of Energy and Process Engineering.
2008 (English)MasteroppgaveStudent thesis
Abstract [en]

Abstract In relation to new building directives and regulations there is much focus on energy efficiency and reducing the use of electricity. There is therefore a need for ventilation systems with low Specific fan power (SFP) and to limit or avoid the need for mechanical cooling. At the same time questions are raised concerning whether increasingly complicated ventilation systems are the best way to achieve energy efficiency. They are more vulnerable for poor design and maintenance which especially school buildings have suffered from. This has led to the development of several natural and hybrid ventilation concepts. One of these which has had success in school buildings the last 15 years in Sweden and Norway is the so-called Swedish model. Characteristic of this solution is that sub terrain culverts are used for passive cooling and heating of the ventilation air which passes through double inner walls and is supplied to the room high on the inner wall. The supply air falls towards the floor mixing in the surrounding air and spreads along the floor as displacement flow with an outlet in the ceiling. This works particularly well in classrooms where the high occupation density creates a cooling demand large parts of the year. These schools therefore have a very low SFP factor and no mechanical cooling. In the following report a classroom model with the Swedish ventilation concept is studied with the aim of developing a method of dimensioning such air flow. CFD simulations are used to confirm expected behaviour and the resulting thermal comfort and air quality at typical winter, spring and summer scenarios. Finally a Guide for preliminary design and sizing for climatization of rooms with cooling needs using the Swedish model is presented. The most important results were that there was a good correspondence between the empirical calculations and CFD simulations. Adequate carbon dioxide levels and temperature can be achieved without use of primary energy for heating at for outdoor temperatures above 5 ºC. There was a substantial risk of draft unless a near zone of 2-3 m is used. However the CFD model was limited to a slice of the classroom and the accuracy of the results suffers somewhat from this. Guidelines are developed for preliminary design and sizing of supply air plumes based on empirical expressions of air flow by Eimund Skåret(2000) and can be found in the appendix.

Place, publisher, year, edition, pages
Institutt for energi- og prosessteknikk , 2008. , 125 p.
Keyword [no]
ntnudaim:4375, MTENERG energi og miljø, Energibruk og energiplanlegging
URN: urn:nbn:no:ntnu:diva-18329Local ID: ntnudaim:4375OAI: diva2:565824
Available from: 2012-11-08 Created: 2012-11-08

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