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Westerlund, Lars
Publications (10 of 48) Show all publications
Lundqvist, P., Risberg, M. & Westerlund, L. (2019). Air heating system design for a sub-Arctic climate using a CFD technique. Building and Environment, 160, Article ID 106164.
Open this publication in new window or tab >>Air heating system design for a sub-Arctic climate using a CFD technique
2019 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 160, article id 106164Article in journal (Refereed) Published
Abstract [en]

The thermal comfort in a residential building equipped with an air heating system and located in a sub-Arctic region was investigated with computational fluid dynamics (CFD) software. The predicted percentage of dissatisfied (PPD) was used to identify flaws with the heating system during winter conditions. New scenarios were simulated and compared to each other to see potential improvements of the thermal indoor climate. Comparison was done by combining the discomfort spaces inside rooms, the level of the discomfort and the time spent in these spaces. The discomfort covered 8–38% of the interior volume depending on the test case. The results provide the necessary means to create a satisfactory thermal indoor climate if an air heating system is to be utilized in sub-Arctic regions during the winter. The correct heat demand for each floor and appropriate placement of the supply devices are required. Adding air transfer units or grilles in rooms from which exhaust air is removed further improves the comfort. The results also show the strength of using CFD technique when investigating the indoor discomfort with PPD, and how a fair assessment can be done by combining the PPD with time.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Air heating, CFD, Cold climate, PPD, Sub-Arctic climate, Thermal comfort
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-75062 (URN)10.1016/j.buildenv.2019.106164 (DOI)000474204100002 ()2-s2.0-85066465960 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-06-27 (johcin)

Available from: 2019-06-27 Created: 2019-06-27 Last updated: 2019-08-16Bibliographically approved
Risberg, D., Risberg, M. & Westerlund, L. (2019). Investigation of thermal indoor climate for a passive house in a sub-Arctic region using computational fluid dynamics. Indoor + Built Environment, 28(5), 677-692
Open this publication in new window or tab >>Investigation of thermal indoor climate for a passive house in a sub-Arctic region using computational fluid dynamics
2019 (English)In: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 28, no 5, p. 677-692Article in journal (Refereed) Published
Abstract [en]

There is currently an increasing trend in Europe to build passive houses. In order to reduce the cost of installation, an air-heating system may be an interesting alternative. Heat supplied through ventilation ducts located at the ceiling was studied with computational fluid dynamics technique. The purpose was to illustrate the thermal indoor climate of the building. To validate the performed simulations, measurements were carried out in several rooms of the building. Furthermore, this study investigated if a designed passive house located above the Arctic Circle could fulfil heat requirements for a Swedish passive house standard. Our results show a heat loss factor of 18.8 W/m2 floor area and an annual specific energy use of 67.9 kWh/m2 floor area, would fulfils the criteria. Validation of simulations through measurements shows good agreement with simulations if the thermal inertia of the building was considered. Calculation of heat losses from a building with a backward weighted moving average outdoor temperature produced correct prediction of the heat losses. To describe the indoor thermal climate correctly, the entire volume needs to be considered, not only one point, which normally is obtained with building simulation software. The supply airflow must carefully be considered to fulfil a good indoor climate.

Place, publisher, year, edition, pages
Sage Publications, 2019
Keywords
CFD simulations, Indoor climate, Passive houses, Sub-Arctic climate, Validation
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-67697 (URN)10.1177/1420326X17753707 (DOI)000469879100008 ()2-s2.0-85042533660 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-06-24 (johcin)

Available from: 2018-02-20 Created: 2018-02-20 Last updated: 2019-06-24Bibliographically approved
Mattsson, J., Hedström, A., Westerlund, L., Dahl, J., Ashley, R. & Viklander, M. (2018). Impacts on rural wastewater systems in subarctic regions due to changes in inputs from households (ed.). Journal of cold regions engineering, 32(1), Article ID 04017019.
Open this publication in new window or tab >>Impacts on rural wastewater systems in subarctic regions due to changes in inputs from households
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2018 (English)In: Journal of cold regions engineering, ISSN 0887-381X, E-ISSN 1943-5495, Vol. 32, no 1, article id 04017019Article in journal (Refereed) Published
Abstract [en]

The use of water-saving appliances and heat exchangers is becoming increasingly popular to decrease water consumption and recover energy from preheated water. However, such in-household changes can bring particular implications for subarctic rural areas, in terms of solids deposition in sewers and drops in performance of wastewater treatment plants (WWTPs), because these are already experiencing diminishing wastewater flows due to depopulation and seasonal dips in wastewater temperature resulting from infiltration into sewers. Hence, this study has considered two communities in Sweden, postulating three different cases with various scales of retrofitting and usage. The results indicate that the decrease in in-pipe velocities when all households are retrofitted with water-saving appliances could be counteracted by sewer relining, but not by the inclusion of a conventional estimate of infiltration. However, for the case in which retrofitting was combined with decreased usage of the appliances, the decrease in self-cleansing capacity could not be counteracted. The retrofitting of heat exchangers under shower trays in all households did not have a significant effect on treatment processes at the WWTP.

Place, publisher, year, edition, pages
American Society of Civil Engineers (ASCE), 2018
National Category
Water Engineering Energy Engineering
Research subject
Urban Water Engineering; Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-14539 (URN)10.1061/(ASCE)CR.1943-5495.0000145 (DOI)000428257200005 ()2-s2.0-85030121882 (Scopus ID)de948167-31d8-4bac-a3d7-ca6af781096b (Local ID)de948167-31d8-4bac-a3d7-ca6af781096b (Archive number)de948167-31d8-4bac-a3d7-ca6af781096b (OAI)
Note

Validerad;2017;Nivå 2;2017-09-25 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-04-20Bibliographically approved
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., 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
Andersson, J.-O., Elfgren, E. & Westerlund, L. (2014). Improved energy efficiency in juice production through waste heat recycling (ed.). Paper presented at International Conference on Applied Energy : Energy Solution for a Sustainable World 01/07/2013 - 05/07/2013. Applied Energy, 130(S1), 757-763
Open this publication in new window or tab >>Improved energy efficiency in juice production through waste heat recycling
2014 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 130, no S1, p. 757-763Article in journal (Refereed) Published
Abstract [en]

Berry juice concentrate is produced by pressing berries and heating up the juice. The by-products are berry skins and seeds in a press cake. Traditionally, these by-products have been composted, but due to their valuable nutrients, it could be profitable to sell them instead. The skins and seeds need to be separated and dried to a moisture content of less than 10 %wt (on dry basis) in order to avoid fermentation. A berry juice plant in the north of Sweden has been studied in order to increase the energy and resource efficiency, with special focus on the drying system. This was done by means of process integration with mass and energy balance, theory from thermodynamics and psychrometry along with measurements of the juice plant. Our study indicates that the drying system could be operated at full capacity without any external heat supply using waste heat supplied from the juice plant. This would be achieved by increasing the efficiency of the dryer by recirculation of the drying air and by heat supply from the flue gases of the industrial boiler. The recirculation would decrease the need of heat in the dryer with about 52%. The total heat use for the plant could thereby be decreased from 1262 kW to 1145 kW. The improvements could be done without compromising the production quality.

National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-33065 (URN)10.1016/j.apenergy.2014.01.092 (DOI)000340311500076 ()2-s2.0-84904819243 (Scopus ID)7d43cecf-6d02-4fbb-bb80-e13b44ce5f5d (Local ID)7d43cecf-6d02-4fbb-bb80-e13b44ce5f5d (Archive number)7d43cecf-6d02-4fbb-bb80-e13b44ce5f5d (OAI)
Conference
International Conference on Applied Energy : Energy Solution for a Sustainable World 01/07/2013 - 05/07/2013
Note
Validerad; 2014; 20140310 (andbra); Konferensartikel i tidskriftAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-07-10Bibliographically approved
Andersson, J.-O. & Westerlund, L. (2014). Improved energy efficiency in sawmill drying system (ed.). Paper presented at . Applied Energy, 113, 891-901
Open this publication in new window or tab >>Improved energy efficiency in sawmill drying system
2014 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 113, p. 891-901Article in journal (Refereed) Published
Abstract [en]

The worldwide use of biomass has increased drastically during the last decade. At Swedish sawmills about half of the entering timber becomes lumber, with the remainder considered as by-product (biomass). A significant part of this biomass is used for internal heat production, mainly for forced drying of lumber in drying kilns. Large heat losses in kilns arise due to difficulties in recovering evaporative heat in moist air at low temperatures. This paper addresses the impact of available state-of-the-art technologies of heat recycling on the most common drying schemes used in Swedish sawmills. Simulations of different technologies were performed on an hourly basis to compare the heat and electricity demand with the different technologies. This was executed for a total sawmill and finally to the national level to assess the potential effects upon energy efficiency and biomass consumption. Since some techniques produce a surplus of heat the comparison has to include the whole sawmill. The impact on a national level shows the potential of the different investigated techniques. The results show that if air heat exchangers were introduced across all sawmills in Sweden, the heat demand would decrease by 0.3 TWh/year. The mechanical heat pump technology would decrease the heat demand by 5.6 TWh/year and would also produce a surplus for external heat sinks, though electricity demand would increase by 1 TWh/year. The open absorption system decreases the heat demand by 3.4 TWh/year on a national level, though at the same time there is a moderate increase in electricity demand of 0.05 TWh/year. Introducing actual energy prices in Sweden gives an annual profit (investment cost excluded) on national level for the open absorption system of almost 580 million SEK. For the mechanical heat pump technology the profit is 204 million SEK and for the traditional heat exchanger the profit is significant lower. It has been found that a widespread implementation of available energy recovery technologies across Swedish sawmills would result in substantial savings of biomass for other purposes in the society

National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-15547 (URN)10.1016/j.apenergy.2013.08.041 (DOI)000329952500087 ()2-s2.0-84883722827 (Scopus ID)f15453d1-86cf-416d-9585-318e6d239750 (Local ID)f15453d1-86cf-416d-9585-318e6d239750 (Archive number)f15453d1-86cf-416d-9585-318e6d239750 (OAI)
Note
Validerad; 2014; 20130910 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
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