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Risberg, Mikael
Publications (10 of 17) 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
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
Sandberg, M., Risberg, M., Ljung, A.-L., Varagnolo, D., Xiong, D. & Nilsson, M. (2017). A modelling methodology for assessing use of datacenter waste heat in greenhouses. In: : . Paper presented at Third International Conference on Environmental Science and Technology, ICOEST, Budapest, 19-23 October 2017.
Open this publication in new window or tab >>A modelling methodology for assessing use of datacenter waste heat in greenhouses
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2017 (English)Conference paper, Published paper (Refereed)
Abstract [en]

In Sweden, the number of datacenters establishments are steadily increasing thanks to green, stable and affordable electricity, free air cooling, advantageous energy taxes and well-developed Internet fiber infrastructures. Even though datacenters use a lot of energy, the waste heat that they create is seldom reused. A possible cause is that this waste heat is often low grade and airborne: it is therefore hard to directly inject it into a district heating system without upgrades, which require additional energy and equipment that generate extra costs. One option for reusing this heat without needs for upgrades is to employ it for heating up greenhouses. But assessing the feasibility of this approach by building physical prototypes can be costly, therefore using computer models to simulate real world conditions is an opportunity. However, there is a lack of computer modelling methodologies that can assess the possibility of using waste heat from datacenters in greenhouses in cold climates.

The objective of this paper is therefore to propose such a methodology and discuss its benefits and drawbacks in comparison with other research studies. This methodology combines computational fluid dynamics, process modelling and control engineering principles into a computer model that constitutes a decision support system to study different waste heat and greenhouse or mushroom house scenarios.

The paper validates the strategy through a case study in northern Sweden, where we assess the amount of produced waste heat by collecting temperature, relative humidity, and fan speed data for the air discharged from the datacenter.

The resulting methodology, composed by conducting measurements and computer models, calculations can then be used for other datacenter operators or greenhouse developers to judge whether it is possible or not to build greenhouses using datacenter waste heat.

National Category
Energy Engineering Other Civil Engineering Fluid Mechanics and Acoustics Control Engineering Other Biological Topics
Research subject
Construction Engineering and Management; Control Engineering; Energy Engineering; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-66466 (URN)
Conference
Third International Conference on Environmental Science and Technology, ICOEST, Budapest, 19-23 October 2017
Funder
Swedish Energy Agency, 41845-1
Available from: 2017-11-08 Created: 2017-11-08 Last updated: 2019-08-29Bibliographically approved
Pericault, Y., Risberg, M., Vesterlund, M., Viklander, M. & Hedström, A. (2017). A novel freeze protection strategy for shallow buried sewer pipes: temperature modelling and field investigation. Water Science and Technology, 76(2), 294-301
Open this publication in new window or tab >>A novel freeze protection strategy for shallow buried sewer pipes: temperature modelling and field investigation
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2017 (English)In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 76, no 2, p. 294-301Article in journal (Refereed) Published
Abstract [en]

The burial of sewer and water pipes below the maximum ground frost depth can be very costly and laborious in regions with cold winters. If a freeze protection measure is applied, the utility lines can be installed in a shallower trench to reduce the excavation needs. One freeze protection measure, so called heat tracing, consists in supplying heat along the pipes. In this work, the use of 4th generation district heating as a heat tracing solution was investigated at a pilot site in Kiruna, Sweden. The influence of the system on sewer and water pipe temperatures was studied at a snow-free and snow-covered cross section. To this end, five heat tracing temperatures were tested and the corresponding sewer and water pipe temperatures were measured. The field experiment was also simulated with a two dimensional finite volume model. The study showed that, under the climatic conditions of the experiment, a heat tracing temperature of 25 °C allowed to prevent freezing of the pipes while keeping drinking water pipes in a safe temperature range at both cross sections. The other main result was that the developed finite volume model of the sections showed a good fitting to the experimental data

Place, publisher, year, edition, pages
IWA Publishing, 2017
Keywords
District heating, heat tracing, low temperature, pipe insulation, temperature modelling, utilidor
National Category
Water Engineering Energy Engineering
Research subject
Urban Water Engineering; Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-63285 (URN)10.2166/wst.2017.174 (DOI)000406789800006 ()28726696 (PubMedID)2-s2.0-85026329219 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-08-15 (rokbeg)

Available from: 2017-05-09 Created: 2017-05-09 Last updated: 2019-03-08Bibliographically approved
Pericault, Y., Risberg, M., Vesterlund, M., Hedström, A. & Viklander, M. (2016). A novel freeze protection strategy for shallow buried sewer pipes: temperature modelling and field investigation. In: Proceedings of the 8th International Conference on Sewer Processes & Networks: . Paper presented at 8th International Conference on Sewer Processes & Networks, 31/8-2/9 2016, Rotterdam..
Open this publication in new window or tab >>A novel freeze protection strategy for shallow buried sewer pipes: temperature modelling and field investigation
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2016 (English)In: Proceedings of the 8th International Conference on Sewer Processes & Networks, 2016Conference paper, Published paper (Other academic)
Abstract [en]

The burial of sewer and water pipes below the maximum ground frost depth can be very costly and laborious in regions with cold winters. If a freeze protection measure is applied, the utility lines can be installed in a shallower trench to reduce the excavation needs during construction and maintenance works. One freeze protection measure, so called heat tracing, consist in supplying heat along the pipes. In this work, the use of 4th generation district heating as a heat tracing solution was investigated at a pilot site in Kiruna, Sweden. The influence of the system on sewer and water pipes temperatures was studied experimentally and numerically at a snow-free and snow-covered cross section. The study showed that, under the climatic conditions of the experiment, a heat tracing temperature of 25 ˚C allowed to prevent freezing of the pipes while keeping drinking water pipes in safe temperature range at both cross sections. The other main result was that a finite volume model of the sections was developed and showed a good fitting to the experimental data.

National Category
Water Engineering Energy Engineering
Research subject
Urban Water Engineering; Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-59899 (URN)
Conference
8th International Conference on Sewer Processes & Networks, 31/8-2/9 2016, Rotterdam.
Available from: 2016-10-24 Created: 2016-10-24 Last updated: 2017-11-24Bibliographically 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, M., Carlsson, P. & Gebart, R. (2015). Numerical modeling of a 500 kW air-blown cyclone gasifier (ed.). Paper presented at . Applied Thermal Engineering, 90, 694-702
Open this publication in new window or tab >>Numerical modeling of a 500 kW air-blown cyclone gasifier
2015 (English)In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 90, p. 694-702Article in journal (Refereed) Published
Abstract [en]

Cyclone gasification of biomass in combination with a gas engine has been considered as a process for combined heat and power production. In this work a numerical model of the cyclone gasification process of wood powder was developed intended to be used as a tool for future engineering design of cyclone gasifiers. The model is based on an Euler-Lagrange formulation for the multiphase flow where the biomass powder was treated as a dispersed phase and the gas as a continuous phase. The results from the simulation are compared with experimental measurement in a 500 kWth cyclone gasifier that uses wood powder as fuel. The model was able to predict the gas composition change with increasing equivalence ratio. The relative error for the main gas component was between 2.5-4.4%, 2.8-5.4%, and 2.6-17.3% for CO2, CO and H2. CH4 was predicted with a relative error of between 3.8-19.2%. Also the model was able to predict the char amount out from the gasifier with reasonable accuracy. The obtained lower heating value from the model was between 3.5 – 5.2 MJ/Nm3 whereas the calculated based on measurement was 4.0-5.3 MJ/Nm3.

National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-14624 (URN)10.1016/j.applthermaleng.2015.06.056 (DOI)000364246500073 ()2-s2.0-84938822201 (Scopus ID)e06ddbca-cf60-4d01-82b7-0c3142c95e08 (Local ID)e06ddbca-cf60-4d01-82b7-0c3142c95e08 (Archive number)e06ddbca-cf60-4d01-82b7-0c3142c95e08 (OAI)
Note
Validerad; 2015; Nivå 2; 20150701 (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
Risberg, M., Öhrman, O., Gebart, R., Nilsson, P., Gudmundsson, A. & Sanati, M. (2014). Influence from fuel type on the performance of an air-blown cyclone gasifier (ed.). Paper presented at . Fuel, 116, 751-759
Open this publication in new window or tab >>Influence from fuel type on the performance of an air-blown cyclone gasifier
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2014 (English)In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 116, p. 751-759Article in journal (Refereed) Published
Abstract [en]

Entrained flow gasification of biomass using the cyclone principle has been proposed in combination with a gas engine as a method for combined heat and power production in small to medium scale (<20 MW). This type of gasifier also has the potential to operate using ash rich fuels since the reactor temperature is lower than the ash melting temperature and the ash can be separated after being collected at the bottom of the cyclone. The purpose of this work was to assess the fuel flexibility of cyclone gasification by performing tests with five different types of fuels; torrefied spruce, peat, rice husk, bark and wood. All of the fuels were dried to below 15% moisture content and milled to a powder with a maximum particle size of around 1 mm. The experiments were carried out in a 500 kWth pilot gasifier with a 3-step gas cleaning process consisting of a multi-cyclone for removal of coarse particles, a bio-scrubber for tar removal and a wet electrostatic precipitator for removal of fine particles and droplets from the oil scrubber (aerosols). The lower heating value (LHV) of the clean producer gas was 4.09, 4.54, 4.84 and 4.57 MJ/N m3 for peat, rice husk, bark and wood, respectively, at a fuel load of 400 kW and an equivalence ratio of 0.27. Torrefied fuel was gasified at an equivalence ratio of 0.2 which resulted in a LHV of 5.75 MJ/N m3 which can be compared to 5.50 MJ/N m3 for wood powder that was gasified at the same equivalence ratio. A particle sampling system was designed in order to collect ultrafine particles upstream and downstream the gasifier cleaning device. The results revealed that the gas cleaning successfully removed >99.9% of the particulate matter smaller than 1 μm.

National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-4473 (URN)10.1016/j.fuel.2013.08.008 (DOI)000326943400095 ()2-s2.0-84884801889 (Scopus ID)2691e4a6-1b23-4e4b-a666-227791bb12fb (Local ID)2691e4a6-1b23-4e4b-a666-227791bb12fb (Archive number)2691e4a6-1b23-4e4b-a666-227791bb12fb (OAI)
Note
Validerad; 2014; 20130809 (mikris)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
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