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Risberg, D., Risberg, M. & Westerlund, L. (2018). The impact of snow and soil freezing for commonly used foundation types in a subarctic climate. Energy and Buildings, 173, 268-280
Open this publication in new window or tab >>The impact of snow and soil freezing for commonly used foundation types in a subarctic climate
2018 (English)In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 173, p. 268-280Article in journal (Refereed) Published
Abstract [en]

Heat losses from a building foundation are affected by both the surrounding conditions and the surrounding soil properties. These include many factors that complicate the analysis of heat loss, such as thermal storage, snow and soil freezing. The effect of snow and soil freezing was studied with a 3D simulation model in a subarctic climate.

The heat losses from the most commonly used foundation types in Sweden were studied. This paper shows that it is possible to achieve a good thermal estimation of the air temperatures in a crawl space, with an average difference of 0.4°C compared with the validation data over a year. Snow and soil freezing reduce the annual heat losses through the different foundation types by 7-10% and the maximum heat loss rate by 13-25%. In order to describe the heat transfer correctly, snow must be included in the calculations, while soil freezing has only a minor impact. The 3D model implemented in this study shows a significant impact on the soil temperatures when these parameters are included.

For a subarctic climate, the commonly used calculation methods based on the European standard ISO 13370 are not thorough enough to calculate the heat transfer through a foundation accurately.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-69125 (URN)10.1016/j.enbuild.2018.05.049 (DOI)2-s2.0-85048552095 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-06-26 (andbra)

Available from: 2018-06-05 Created: 2018-06-05 Last updated: 2018-06-26Bibliographically approved
Risberg, D., Westerlund, L. & Hellström, J. G. (2017). Computational fluid dynamics simulation of indoor climate in low energy buildings computational set up. Thermal Science, 21(5), 1985-1998
Open this publication in new window or tab >>Computational fluid dynamics simulation of indoor climate in low energy buildings computational set up
2017 (English)In: Thermal Science, ISSN 0354-9836, E-ISSN 2334-7163, Vol. 21, no 5, p. 1985-1998Article in journal (Refereed) Published
Abstract [en]

In this paper CFD was used for simulation of the indoor climate in a part of a low energy building. The focus of the work was on investigating the computational set up, such as grid size and boundary conditions in order to solve the indoor climate problems in an accurate way. Future work is to model a complete building, with reasonable calculation time and accuracy. A limited number of grid elements and knowledge of boundary settings are therefore essential. An accurate grid edge size of around 0.1 m was enough to predict the climate according to a grid independency study. Different turbulence models were compared with only small differences in the indoor air velocities and temperatures. The models show that radiation between building surfaces has a large impact on the temperature field inside the building, with the largest differences at the floor level. Simpling the simulations by modelling the radiator as a surface in the outer wall of the room is appropriate for the calculations. The overall indoor climate is finally compared between three different cases for the outdoor air temperature. The results show a good indoor climate for a low energy building all around the year.

Place, publisher, year, edition, pages
VINČA Institute of Nuclear Sciences, 2017
National Category
Energy Engineering Fluid Mechanics and Acoustics
Research subject
Energy Engineering; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-66606 (URN)10.2298/TSCI150604167R (DOI)000414237000010 ()2-s2.0-85032913950 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-11-17(inah)

Available from: 2017-11-17 Created: 2017-11-17 Last updated: 2018-11-19Bibliographically approved
Risberg, D., Risberg, M. & Westerlund, L. (2016). CFD modelling of radiators in buildings with user defined wall functions (ed.). Paper presented at . Applied Thermal Engineering, 64, 266-273
Open this publication in new window or tab >>CFD modelling of radiators in buildings with user defined wall functions
2016 (English)In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 64, p. 266-273Article in journal (Refereed) Published
Abstract [en]

The most widely used turbulence model for indoor CFD simulations, the k-ε model, has exhibited problems with treating natural convective heat transfer, while other turbulence models have shown to be too computationally demanding. This paper studies how to deal with natural convective heat transfer for a radiator in order to simplify the simulations, reduce the numbers of cells and the simulation time. By adding user-defined wall functions the number of cells can be reduced considerably compared with the k-ω SST turbulence model. The user-defined wall function proposed can also be used with a correction factor for different radiator types without the need to resolve the radiator surface in detail. Compared to manufacturer data the error is less than 0.2% for the investigated radiator height and temperature.

National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-9742 (URN)10.1016/j.applthermaleng.2015.10.134 (DOI)000370770300028 ()2-s2.0-84947125521 (Scopus ID)868ebecd-4ce7-46ad-9b29-ded1785ffaeb (Local ID)868ebecd-4ce7-46ad-9b29-ded1785ffaeb (Archive number)868ebecd-4ce7-46ad-9b29-ded1785ffaeb (OAI)
Note
Validerad; 2015; Nivå 2; 20151105 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Risberg, D., Vesterlund, M., Westerlund, L. & Dahl, J. (2015). CFD simulation and evaluation of different heating systems installed in low energy building located in sub-arctic climate (ed.). Paper presented at . Building and Environment, 89, 160-169
Open this publication in new window or tab >>CFD simulation and evaluation of different heating systems installed in low energy building located in sub-arctic climate
2015 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 89, p. 160-169Article in journal (Refereed) Published
Abstract [en]

Computational Fluid Dynamics (CFD) simulations were used to study the indoor climate in a low energy building in northern Sweden. The building’s low heat requirement raise the prospect of using a relatively simple and inexpensive heating system to maintain an acceptable indoor environment, even in the face of extremely low outdoor temperature. To explore the viability of this approach, the indoor climate in the building was studied considering three different heating systems: a floor heating system, air heating through the ventilation system and an air heat pump installation with one fan coil unit. The floor heating system provided the most uniform operative temperature distribution and was the only heating system that fully satisfied the recommendations to achieve tolerable indoor climate set by the Swedish authorities. On the contrary, air heating and the air heat pump created a relatively uneven distribution of air velocities and temperatures, and none of them fulfills the specified recommendations. From the economic point of view, the air heat pump system was cheaper to be installed but produced a less pleasant indoor environment than the other investigated heating systems.

National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-11144 (URN)10.1016/j.buildenv.2015.02.024 (DOI)000364440600014 ()2-s2.0-84924737867 (Scopus ID)a0dde22a-a36f-4f00-a108-d848722aa479 (Local ID)a0dde22a-a36f-4f00-a108-d848722aa479 (Archive number)a0dde22a-a36f-4f00-a108-d848722aa479 (OAI)
Note
Validerad; 2015; Nivå 2; 20150305 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Risberg, D. (2015). CFD simulation of indoor climate in low energy buildings (ed.). (Licentiate dissertation). Paper presented at . : Luleå tekniska universitet
Open this publication in new window or tab >>CFD simulation of indoor climate in low energy buildings
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis computational fluid dynamics (CFD) was used for simulation of the indoor climate of low-energy buildings in cold climate. The heat consumption in newly built houses was reduced drastically. Along with the different classification systems for low-energy buildings the demand for the indoor climate has increased, which causes a need to investigate buildings even before they are built. Than CFD is of importance in studies of different heating systems and how new construction solutions can affect the indoor environment. The work focus was on investigating the computational setup, such as grid size and boundary conditions in order to solve the indoor climate problems in an accurate way and compare different heating systems. A limited number of grid elements and knowledge of boundary settings is therefore essential in order to obtain reasonable calculation time.The models show that radiation between building surfaces has a large impact on the temperature field inside the building, with the largest differences at the floor level. An accurate grid edge size of around 0.1 m was enough to predict the climate. Different turbulence models were compared with only small differences in the indoor air velocities and temperatures. To explore the viability of this approach, the indoor climate in a building was studied considering three different heating systems: an underfloor heating system, air heating through the ventilation system and an air heat pump installation. The underfloor heating system provided the most uniform operative temperature distribution and was the only heating system that fully satisfies the recommendations to achieve tolerable indoor climate set by the Swedish authorities. On the contrary, air heating and the air heat pump created a relatively uneven distribution of air velocities and temperatures, and none of them fulfils the specified recommendations. From an economic point of view, the air heat pump system is cheaper to be installed but produces a less pleasant indoor environment then distributed heating systems. The most widely used turbulence model for indoor CFD simulations, the k-ε model, has exhibited problems with treating natural convective heat transfer, while other turbulence models have shown to be too computationally demanding. One paper therefore studies how to deal with natural convective heat transfer for a radiator in order to simplify the simulations, reduce the numbers of cells and the simulation time. By adding user-defined wall functions, to the k-ε model the number of cells can be reduced considerably compared with the k-ω SST turbulence model. The user-defined wall function proposed can also be used with a correction factor for different radiator types without the need to resolve the radiator surface in detail. Compared to manufacturer data the error was less than 0.2% for the investigated radiator height and temperature.

Place, publisher, year, edition, pages
Luleå tekniska universitet, 2015
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-18432 (URN)898b3350-b158-4ca4-af13-c072694ecb47 (Local ID)978-91-7583-413-9 (ISBN)978-91-7583-414-6 (ISBN)898b3350-b158-4ca4-af13-c072694ecb47 (Archive number)898b3350-b158-4ca4-af13-c072694ecb47 (OAI)
Note
Godkänd; 2015; 20150915 (danris); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Daniel Risberg Ämne: Energiteknik/Energy Engineering Uppsats: CFD Simulation of Indoor Climate in Low Energy Buildings Examinator: Professor Lars Westerlund, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Professor Thomas Olofsson, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Tid: Måndag 2 november 2015 kl 10.00 Plats: E632, Luleå tekniska universitetAvailable from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-02-21Bibliographically approved
Risberg, D., Vesterlund, M., Risberg, M., Hedström, A., Dahl, J. & Westerlund, L. (2014). Hållbara, integrerade energi- och VA-system (ed.). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Hållbara, integrerade energi- och VA-system
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2014 (Swedish)Report (Other academic)
Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2014. p. 30
Series
Rapportserie Attract ; 2014:04
National Category
Energy Engineering Water Engineering
Research subject
Energy Engineering; Urban Water Engineering
Identifiers
urn:nbn:se:ltu:diva-23505 (URN)73e3908f-5847-4f04-af09-6f9adbcefebe (Local ID)978-91-7583-284-5 (ISBN)978-91-7583-285-2 (ISBN)73e3908f-5847-4f04-af09-6f9adbcefebe (Archive number)73e3908f-5847-4f04-af09-6f9adbcefebe (OAI)
Note
Godkänd; 2014; 20150326 (danris)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-02-21Bibliographically approved
Risberg, D., Vesterlund, M., Westerlund, L. & Dahl, J. (2013). CFD simulations of the indoor climate of a low energy building in a sub-Arctic climate: an evaluation of different heating systems (ed.). Paper presented at International Conference on Sustainable Energy Technologies : 26/08/2013 - 29/08/2013. Paper presented at International Conference on Sustainable Energy Technologies : 26/08/2013 - 29/08/2013.
Open this publication in new window or tab >>CFD simulations of the indoor climate of a low energy building in a sub-Arctic climate: an evaluation of different heating systems
2013 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

Computational Fluid Dynamics (CFD) simulations were used to study the indoor climate in a low energy building in northern Sweden. The building’s low heat requirements raise the prospect of using relatively simple and inexpensive heating systems to maintain an acceptable indoor environment, even in the face of extremely low outdoor temperatures. To explore the viability of this approach, the indoor temperature and air velocity distribution inside the building were studied assuming that it was fitted with one of four different heating systems: radiators, an underfloor heating system, a pellet stove, and an air/air heat pump. The radiators produced a relatively uniform horizontal temperature distribution throughout the house. The underfloor system provided an even more uniform temperature distribution. In contrast, the heat pump created a relatively uneven internal temperature distribution. Several locations for the pump were considered, all of which had significant drawbacks. The pellet stove produced a more even temperature distribution than the pump but not to the same extent as the underfloor system or the radiators. Overall, point source heating systems cost less to fit and operate over a given period of time but produce a less clement indoor environment than distributed heating systems.

Keywords
Engineering mechanics - Mechanical and thermal engineering, CFD-simulation, Indoor climate, Low energy building, Sub-artic climate, Teknisk mekanik - Mekanisk och termisk energiteknik
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-31056 (URN)519b97f3-875d-4606-bfd9-ad3fbd2eb8ed (Local ID)519b97f3-875d-4606-bfd9-ad3fbd2eb8ed (Archive number)519b97f3-875d-4606-bfd9-ad3fbd2eb8ed (OAI)
Conference
International Conference on Sustainable Energy Technologies : 26/08/2013 - 29/08/2013
Note
Godkänd; 2013; 20140305 (matves)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-02-21Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0225-711x

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