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  • 1.
    Berggren, Karolina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Moghadas, Shahab
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Gustafsson, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Ashley, Richard
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Sensitivity of urban stormwater systems to runoff from green/pervious areas in a changing climate2013Conference paper (Refereed)
  • 2.
    Berggren, Karolina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Olofsson, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Svensson, Gilbert
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Gustafsson, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Hydraulic impacts on urban drainage systems due to changes in rainfall, caused by climatic change2012In: Journal of hydrologic engineering, ISSN 1084-0699, E-ISSN 1943-5584, Vol. 17, no 1, p. 92-98Article in journal (Refereed)
    Abstract [en]

    The changes in climate were of a growing concern in the last decade, and will be even more so in the coming years. When investigating impacts on urban drainage systems due to changes in the climate, two challenges are (1) what type of input rainfall data to use, and (2) what parameters to measure the impacts. The overall objective of this study is to investigate the hydraulic performances ofurban drainage systems related to changes in rainfall, and through these hydraulic parameters describe impacts of climate change. Input rainfall data represents today's climate, as well as three future time periods (2011-2040, 2041-2070, and 2071-2100). The hydraulic parameters used were water levels in nodes (e.g. as the number of floods, frequency and duration of floods), and pipe flow ratio. For the study area, the number of flooded nodes and the geographical distribution of floods will increase in the future, as will both the flooding frequency and the duration of floods.

  • 3.
    Borris, Matthias
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Gustafsson, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Marsalek, Jiri
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Continuous simulations of urban stormwater runoff and total suspended solids loads: influence of varying climatic inputs and catchment imperviousness2014In: Journal of Water and Climate, ISSN 2040-2244, Vol. 5, no 4, p. 593-609Article in journal (Refereed)
    Abstract [en]

    Potential implications of climate change for future stormwater management were addressed by undertaking continuous simulations of runoff and total suspended solids (TSS) loads for three urban catchments, with imperviousness varying from 23 to 63%, which were exposed to five rainfall regimes during the snow-free part of the year: the current climate and four climate change scenarios projecting higher rainfalls. Simulated runoff volumes increased in all the future scenarios, particularly in the sub-arctic climate and the fixed uplift scenario (plus20) indicating appreciable rainfall increases. Simulated runoff volumes increased depending on the projected increases in rainfall and increasing runoff contributions from pervious areas when more intense future rainfalls exceeded hydrologic abstractions. The increased runoff volumes then contributed higher TSS loads, which were highly variable for the rainfall regimes tested. In cold climate regions, residues of solids from winter road maintenance may contribute to high initial accumulations of TSS on the catchment surface and high washed off loads. In general, the study suggests that intermediate design-life stormwater management facilities require flexible design allowing for future step-wise adaptation by gradually increasing design capacities and modifying treatment trains.

  • 4.
    Borris, Matthias
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Gustafsson, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Marsalek, Jiri
    National Water Research Institute, Environment Canada.
    Modelling the effects of changes in rainfall event characteristics on TSS loads in urban runoff2014In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 28, no 4, p. 1787-1796Article in journal (Refereed)
    Abstract [en]

    The effect of changes in rainfall event characteristics on urban stormwater quality, which was described by total suspended solids (TSS), was studied by means of computer simulations conducted with the Storm Water Management Model for a climate change scenario for northern Sweden. The simulation results showed that TSS event loads depended mainly on rainfall depth and intensity, but not on antecedent conditions. Storms with low-to-intermediate depths and intensities showed the highest sensitivity to changes in rainfall input, both for percentage and absolute changes in TSS wash-off loads, which was explained by the contribution of pervious areas and supply limitations. This has significant implications for stormwater management, because those relatively frequent events generally carry a high percentage of the annual pollutant load

  • 5.
    Borris, Matthias
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Gustafsson, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Marsalek, Jiri
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Simulating future trends in urban stormwater quality for changing climate, urban land use and environmental controls2013In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 68, no 9, p. 2082-2089Article in journal (Refereed)
    Abstract [en]

    The effects of climatic changes, progressing urbanization and improved environmental controls on the simulated urban stormwater quality in a northern Sweden community were studied. Future scenarios accounting for those changes were developed and their effects simulated with the Storm Water Management Model (SWMM). It was observed that the simulated stormwater quality was highly sensitive to the scenarios, mimicking progressing urbanization with varying catchment imperviousness and area. Thus, land use change was identified as one of the most influential factors and in some scenarios, urban growth caused changes in runoff quantity and quality exceeding those caused by a changing climate. Adaptation measures, including the reduction of directly connected impervious surfaces (DCIS) through the integration of more green spaces into the urban landscape, or disconnection of DCIS were effective in reducing runoff volume and pollutant loads. Furthermore, pollutant source control measures, including material substitution, were effective in reducing pollutant loads and significantly improving stormwater quality

  • 6.
    Borris, Matthias
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Gustafsson, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Marsalek, Jiri
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Using urban runoff simulations for addressing climate change impacts on urban runoff quality in a Swedish town2012In: Urban Drainage Modelling: Proceedings of the Ninth International Conference on Urban Drainage Modelling, Belgrade, Serbia, 4-6 September 2012, Belgrade: Faculty of Civil Engineering, University of Belgrade , 2012Conference paper (Refereed)
    Abstract [en]

    The effect of climate change on urban stormwater quality was studied by means of computer simulations conducted with the Stormwater Management Model (SWMM) for common climate change scenarios developed for northern Sweden. The simulation results showed that stormwater quality depended on rainfall characteristics; a climate scenario implying increased rainfall depths and intensities produced higher pollutant loads carried by stormwater, but reduced concentrations, particularly for medium to high intensity storm events. This type of stormwater quality response was explained by pollutant supply limited transport processes and the resulting dilution of such pollutants. Medium intensity events showed the highest sensitivity to climatic changes, since such events strongly affected the contributions of pervious surfaces. This has significant implications for stormwater management, because those relatively frequent events generally carry a high percentage of the annual pollutant load.

  • 7.
    Gustafsson, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Multi injection rate: Thermal response test2009In: Abstract book and proceeding : Effstock 2009: 11th International conference on Thermal Energy Storage for Energy Efficiency and Sustainability, 2009Conference paper (Refereed)
  • 8.
    Gustafsson, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Thermal response test: numerical simulations and analyses2006Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    When constructing large borehole heat exchanger (BHE) systems, bedrock and borehole thermal properties are vital for a good design. Today's design programs presume conductive heat transfer in both borehole and bedrock. In groundwater-filled boreholes, however, convective flow will be induced in the groundwater due to the occurring temperature gradients. The resulting more efficient heat transfer lowers the borehole thermal resistance. A 3 m long borehole was numerically studied to investigate the effect of heat injection on natural convection in a groundwater-filled borehole heat exchanger in impermeable bedrock. A convective flow with rising water close to the U-pipe and descending water at the borehole wall was induced. The flow rates in the groundwater are determined by the temperature gradient in the borehole. A higher injection rate results in a larger convective heat transfer, lowering the borehole thermal resistance. An equivalent radius model was also constructed in order to examine possible model simplifications. Using an annulus instead of a more complex U-pipe geometry may radically decrease the required computer capacity and calculation time. The result shows that for a solid bedrock model, borehole mean heat transfer patterns are similar for both models. Therefore, it may be possible to use the simpler equivalent radius model to simulate the convective heat transfer in borehole heat exchangers. Thermal response tests in boreholes were also conducted to investigate the effect of different power and temperature levels on convective heat transfer. A decrease in borehole thermal resistance is seen for higher fluid temperatures. A cold injection test was also performed. The resulting lower temperatures in the borehole increase the borehole thermal resistance, and leading to the formation of ice in the borehole. These tests indicate the importance of using different borehole thermal resistances in BHE design calculations, if the system should operate under several power levels. Thermal response test while drilling was investigated as an alternative method to the standard thermal response test. With this new method, bedrock conductivity would be continuously determined along the borehole. Therefore, bedrock anomalies such as fractures may be detected. The method is investigated for water driven down-the-hole hammers. A numerical model was developed to investigate the thermal response to heat release during drilling. The results show that by providing measurements of high accuracy and precision, occurring small changes in conductivity may be detectable. This licentiate thesis is the first part of a PhD thesis. It summarises the results of the study on the effect of natural convection on BHEs, as well as theoretical investigation of a new thermal response test method. To fulfil the PhD, the influence of groundwater movement on thermal response tests will be further studied with numerical models and field tests. The goal is to implement the result in BHE design calculation programs and TRT analysis. This licentiate thesis includes two submitted journal articles and one conference paper.

  • 9.
    Gustafsson, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Thermal response tests: influence of convective flow in groundwater filled borehole heat exchanger2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The main objective of this doctorial thesis was to investigate how thermally induced movements in the groundwater (natural convective flow) may influence the heat transport in borehole and surrounding bedrock in a groundwater filled borehole heat exchanger system. The purpose was also to determine if thermal response tests could be used to detect the convective influence and the effect on evaluated heat transfer parameters, effective bedrock thermal conductivity and borehole thermal resistance. In order to increase the knowledge about the natural convective influence in groundwater filled borehole heat exchangers, numerical 3D simulations in the computer fluid dynamic (CFD) software Fluent were conducted. It was shown that the thermally induced convective flow influenced the borehole thermal resistance independently of bedrock characteristics (solid or fractured). A larger convective heat flow (dependent on density gradient) resulted in a lower resistance. The density gradient and thereby the convective flow are affected by the water temperature level and the used heat injection or extraction rate. At a water temperature around 4ºC (maximum density), the borehole thermal resistance had its maximum value resulting in values close to stagnant water. In other working conditions the heat transfer could be up to 2.5 times greater than that of stagnant water. This was further investigated and confirmed by in-situ thermal response tests in two boreholes at the campus of Luleå University of Technology. Several multi-injection rate thermal response tests were performed, which is a test protocol where several test periods are performed in a row using different heat injection rates. With this protocol it was shown that natural convective flow may be seen to affect both the borehole thermal resistance and effective bedrock thermal conductivity. For the bedrock thermal conductivity it was shown that the convective influence was seen only for fractured bedrock. A larger convective heat flow resulted in a higher effective bedrock thermal conductivity. The numerical 3D simulations were also used to study some common approximations when modelling grouted boreholes to see if these would also be suitable for groundwater filled boreholes. The purpose was to find approximations that would allow for a simpler model for evaluation of thermal response tests and design of borehole heat exchanger systems. It was shown that using an equivalent radius model (one single pipe in the middle of the borehole) instead of the more complex u-pipe geometry was a good approximation, if the appropriate equivalent radius was used. For the total heat transfer, including the convective heat flow, the total heat transfer area should be the same as for the u-pipes. Another approximation that was tested was to use a boundary condition at the outer pipe wall instead of simulating the fluid flow inside the pipe and the heat flow through the pipe wall. It was shown that the two common boundary conditions, constant temperature and constant heat flux, gave similar results for total heat transfer calculations but quite different results for only conductive heat transfer calculations. Performed investigations showed that the convective influence could give large differences in evaluated borehole thermal resistance and effective bedrock thermal conductivity. It is therefore strongly recommended that thermal response tests are performed using similar heating or cooling conditions as the planned borehole system. In Sweden, most systems use heat extraction during part of the year. For that reason, heat extraction thermal response tests in groundwater filled boreholes were studied. It was shown that ordinary evaluation methods did not work due to the large variations in the value of the borehole thermal resistance during the test. Instead a new evaluation method was proposed, where the measurement time was divided into intervals, where each new interval allowed for a new borehole thermal resistance. The same numerical model was used as in the ordinary parameter estimation evaluation used for the other tests. The model was run manually, and each new borehole thermal resistance was chosen so that the calculated mean fluid temperature for that period matched the measured values. The intervals were recommended to be chosen between 4 to 10 hours depending on how fast the mean fluid temperature changed.

  • 10.
    Gustafsson, Anna-Maria
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Gehlin, Signhild
    Swedish Society of HVAC Engineers, Stockholm.
    Influence of natural convection in water-filled boreholes for GCHP2008In: ASHRAE Transactions, ISSN 0001-2505, Vol. 114, no 1, p. 416-423Article in journal (Refereed)
    Abstract [en]

    In groundwater filled borehole heat exchangers (BHE), convective flow inside the borehole water will affect the heat transfer. Since the convective flow is dependent of the temperature gradient, different injection rates and ground temperatures will result in different borehole thermal resistance. This paper describes the influence of natural convection in water-filled boreholes in impermeable bedrock for ground-coupled heat pump (GCHP) systems. An overview of groundwater-filled boreholes and the influence of groundwater movements are presented followed by numerical simulations and field measurements to further investigate the influence. The results from the simulations of the three-dimensional, steady-state model of a 9.8 ft (3 m) deep BHE are compared to evaluated results from performed thermal response test (TRT). The results show that convective flow in groundwater-filled BHE results in 5-9 times more efficient heat transfer compared to stagnant water when heat carrier temperatures are in the range of 50-86°F (10-30°C). The size of the convective flow depends on the temperature gradients in the borehole. This shows the importance of on-site investigation of thermal properties using appropriate power injection rates similar to those in the system to be built. This research is part of an on-going project to find ways to estimate the heat transfer including convective flow and to incorporate the findings into the design of GCHP systems. TRT are today a common way to determine heat transfer properties for a BHE and its surroundings. Performing TRT measurements with several injection rates is a way to evaluate the dynamic thermal response including the change in convective flow due to changes in temperature levels. If this dynamic response would be included in design tools a more thorough design of the BHE system is performed. Here, the early result of this research is presented

  • 11.
    Gustafsson, Anna-Maria
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Gehlin, Signhild
    Thermal response test: power injection dependence2006In: Thermal energy storage: : 2006 EcoStock ; [10th International Conference on Thermal Energy Storage] ; May 31 - June 2, 2006, the Richard Stockton College of New Jersey ; proceedings, Pomona, NJ: Richard Stockton College of NJ , 2006Conference paper (Refereed)
  • 12. Gustafsson, Anna-Maria
    et al.
    Nordell, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Thermal response test while drilling2006In: Thermal energy storage: 2006 EcoStock ; [10th International Conference on Thermal Energy Storage] ; May 31 - June 2, 2006, the Richard Stockton College of New Jersey ; proceedings, Pomona, NJ: Richard Stockton College of NJ , 2006Conference paper (Refereed)
  • 13.
    Gustafsson, Anna-Maria
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Svensson, Gilbert
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Metoder för att undersöka extrema regnhändelsers påverkan på dagvattensystemet2014Report (Refereed)
    Abstract [sv]

    Detta projekt har genomförts av Luleå Tekniska Universitet i samarbete med 5 kommuner; Arvika, Skellefteå, Sundsvall, Trelleborg samt Växjö. Projektets syfte har varit att studera hur olika metoder kan användas för att utvärdera dagvattensystemets påverkan av extrema regnhändelser. Rapporten har skrivits i syfte att ge en övergripande bild av olika metoder och de osäkerheter som finns när de olika metoderna används. Materialet i rapporten är hämtat från aktuellt projekt samt från parallella studier vid forskningsgruppen Stadens vatten, LTU och från internationella och nationella studier för att ge ett så brett perspektiv på olika metoder som möjligt. De metoder som beskrivs i rapporten går från en väldigt enkel analys baserat på vanliga dimensioneringsekvationer som kan utföras i ett excelark eller för hand till analyser som kräver komplexa modeller som simulerar vattenföringen i ledningsnätet samt ytavrinning kopplat till infiltration. Alla metoder kräver någon form av nederbördsinformation och därför inkluderas i rapporten ett avsnitt om regn och framtida regn kopplat till klimatförändring. För att genomföra en analys krävs även parametrar att studera effekterna av olika körningar och i slutet presenteras ett kort avsnitt om indikationer som är lämpliga att använda vid utvärdering av dagvattensystemet. När en metod ska väljas är det viktigt att syfte med undersökning och resurser i form av tid, existerande data och pengar ställs mot varandra. En avancerad modell har ett större krav på indata, datakapacitet och på mätdata som den kan verifieras mot. I vissa fall är det bättre att använda en enklare modell med kontinuerligt, historiskt regndata medan i andra fall krävs en komplex modell som inkluderar t.ex. infiltration i permeabla ytor och att då använda sig av designregn för att klara av de begränsningar som ev. finns i datakapacitet och simuleringstid. Innan beslut tas om modell eller metod bör det noggrant funderas över varför modellen ska tas fram, hur den ska användas samt vilka data som finns tillgängliga eller kan tas fram med nya mätningar. Om metoderna beskrivna i rapporten används på korrekt sätt och verifieras med tillräckligt data kan dessa utvärderingar av dagvattensystemet ge en bra bild av hur systemet fungerar samt hur det påverkas av olika scenarier.

  • 14.
    Gustafsson, Anna-Maria
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Westerlund, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Heat extraction thermal response test in groundwater-filled borehole heat exchanger: Investigation of the borehole thermal resistance2011In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 36, no 9, p. 2388-2394Article in journal (Refereed)
    Abstract [en]

    In groundwater-filled borehole heat exchangers (BHEs) convective flow influences the heat transfer in the borehole. During heat extraction thermal response tests (TRTs) the effect of the changing convective flow is more dominant than during heat injection tests. Water is heaviest around 4 °C and when exceeding this temperature during the test, the convective flow is stopped and restarted in the opposite direction resulting in a higher borehole thermal resistance during that time. Just before 0 °C the convective flow is the largest resulting in a much lower borehole thermal resistance. Finally, during the freezing period phase change energy is released and material parameters change as water is transformed into ice, resulting in a slightly higher borehole resistance than at a borehole water temperature of 0 °C. The changes in borehole thermal resistance are too large for ordinary analysis methods of thermal response tests to work. Instead another method is introduced where the borehole thermal resistance is allowed to change between different time intervals. A simple 1D model of the borehole is used, which is matched to give a similar mean fluid temperature curve as the measured one while keeping the bedrock thermal conductivity constant during the whole test. This method is more time-consuming than ordinary TRT analyses but gives a good result in showing how the borehole thermal resistance changes. Also, a CFD-model with a section of a simplified borehole was used to further study the effect of convection and phase change while the temperature was decreased below freezing point. The test and the model show similar results with large variations in the borehole thermal resistance. If the knowledge of changing borehole thermal resistance was used together with a design program including the heat pump and its efficiency, a better BHE system design would be possible.

  • 15.
    Gustafsson, Anna-Maria
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Westerlund, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Multi-injection rate thermal response test in groundwater filled borehole heat exchanger2010In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 35, no 5, p. 1061-1070Article in journal (Refereed)
    Abstract [en]

    During a thermal response test (TRT) or during operation of a borehole heat exchanger (BHE) system, a temperature gradient in and around the borehole is achieved. This causes convective flow in the groundwater due to density differences. In groundwater filled BHE the convective heat flow influences the heat transport in the borehole system. The size of the influence depends on the injection rate used, which changes during the year for normal BHE systems. Multi-injection rate TRT (MIR TRT) may be used as a method to detect the convective heat influence and to examine the effect on the BHE thermal transport parameters. It was shown that MIR TRT constitutes a valuable method to detect fractured bedrock and to examine the effect of different heat injection rates. For boreholes located in solid bedrock only the borehole thermal resistance was influenced by the convective flow. An increase in heat injection rate resulted in a decrease in resistance. It was shown that the length of the collector did not affect the result. For the fractured bedrock the effective bedrock conductivity was also affected, an increase in heat injection rate resulted in a higher effective bedrock thermal conductivity.

  • 16.
    Gustafsson, Anna-Maria
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Westerlund, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Simulation of the thermal borehole resistance in groundwater filled borehole heat exchanger using CFD technique2010In: International Journal of Energy and Environment, ISSN 2076-2895, E-ISSN 2076-2909, Vol. 1, no 3, p. 399-410Article in journal (Refereed)
    Abstract [en]

    The thermal borehole resistance in a groundwater-filled borehole heat exchanger (BHE) is affected of both conductive and convective heat transfer through the borehole water. To calculate this heat transport, different models are required compared to calculation of only conductive heat transfer in a back-filled BHE. In this paper some modelling approximations for groundwater-filled, single U-pipe BHEs were investigated using a 3D CFD model. The purpose is to find approximations that enable to construct a fast, simple model including the convective heat transfer that may be used in thermal response test analyses and BHE design programs. Both total heat transfer calculations (including convective and conductive heat transport) and only conductive heat transfer calculations were performed for comparison purposes. The approximations that are investigated are the choice of boundary condition at the U-pipe wall and using a single pipe in the middle of the borehole instead of the U-pipe. For the total heat transfer case, it is shown that the choice of boundary condition hardly affects the calculated borehole thermal resistance. For the only conductive heat transfer case, the choice of boundary condition at the pipe wall gives large differences in the result. It is also shown that using an annulus model (single pipe in the middle of the borehole) results in similar heat transfer as the U-pipe model provided that the equivalent radius is chosen appropriately. This approximation can radically decrease the number of calculation cells needed.

  • 17.
    Gustafsson, Anna-Maria
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Westerlund, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hellström, Göran
    CFD-modelling of natural convection in a groundwater-filled borehole heat exchanger2010In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 30, no 6-7, p. 683-691Article in journal (Refereed)
    Abstract [en]

    In design of ground-source energy systems the thermal erformance of the borehole heat exchangers is important. In Scandinavia, boreholes are usually not grouted but left with groundwater to fill the space between heat exchanger pipes and borehole wall. The common U-pipe arrangement in a groundwater-filled BHE has been studied by a three-dimensional, steady-state CFD model. The model consists of a three meter long borehole containing a single U-pipe with surrounding bedrock. A constant temperature is imposed on the U-pipe wall and the outer bedrock wall is held at a lower constant temperature. The occurring temperature gradient induces a velocity flow in the groundwater-filled borehole due to density differences. This increases the heat transfer compared to stagnant water. The numerical model agrees well with theoretical studies and laboratory experiments. The result shows that the induced natural convective heat flow significantly decreases the thermal resistance in the borehole. The density gradient in the borehole is a result of the heat transfer rate and the mean temperature level in the borehole water. Therefore in calculations of the thermal resistance in groundwater filled boreholes convective heat flow should be included and the actual injection heat transfer rate and mean borehole temperature should be considered.

  • 18.
    Leonhardt, Günther
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Bacchin, Taneha K
    Department of Urbanism, Faculty of Architecture and the Built Environment, Delft University of Technology.
    Mair, Michael
    Unit of Environmental Engineering, Institute for Infrastructure Engineering, University of Innsbruck.
    Zischg, Jonathan
    Unit of Environmental Engineering, Institute for Infrastructure Engineering, University of Innsbruck.
    Ljung, Stina
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Rogers, Briony
    School of Social Sciences, Monash Water for Liveability Centre, Monash University.
    Goldkuhl, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Gustafsson, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Sitzenfrei, Robert
    Unit of Environmental Engineering, Institute for Infrastructure Engineering, University of Innsbruck.
    Blecken, Godecke-Tobias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Ashley, Richard
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Rauch, Wolfgang
    Unit of Environmental Engineering, Institute for Infrastructure Engineering, University of Innsbruck.
    Timmeren, Arjan van
    Department of Urbanism, Faculty of Architecture and the Built Environment, Delft University of Technology.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Relocating a city, challenges and opportunities for the transition of water infrastructure in Kiruna2015In: Urban Drainage Modelling 2015: Proceedings of the 10th International Conference of Urban Drainage Modelling, Mont-Sainte-Anne, Québec, Canada 20-23 Swptember 2015 / [ed] Thomas Maere; Sovanna Tik; Sophie Duchense; Peter A. Vanrolleghem, 2015, p. 77-84Conference paper (Refereed)
  • 19.
    Leonhardt, Günther
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Moghadas, Shahab
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Gustafsson, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Marsalek, Jiri
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Modelling the effects of the joint occurrence of rainfall and snowmelt in urban catchments2015Conference paper (Refereed)
  • 20.
    Leonhardt, Günther
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Moghadas, Shahab
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Gustafsson, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Marsalek, Jiri
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Modelling the effects of the joint occurrence of rainfall and snowmelt in urban catchments2015Conference paper (Refereed)
  • 21.
    Leonhardt, Günther
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Moghadas, Shahab
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Johansson, Lars
    Tekniska Verken i Kiruna AB.
    Gustafsson, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Marsalek, Jiri
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Modelling the effects of the joint occurrence of rainfall and snowmedlt in urban catchments2015In: Urban Drainage Modelling 2015: Proceedings of the 10th International Conference of Urban Drainage Modelling, Mont-Sainte-Anne, Québec, Canada 20-23 Swptember 2015 / [ed] Thomas Maere; Sovanna Tik; Sophie Duchense; Peter A. Vanrolleghem, 2015, p. 25-31Conference paper (Refereed)
  • 22.
    Moghadas, Shahab
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Berggren, Karolina
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Gustafsson, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Regional and seasonal variation in future climate: is green roof one solution?2011Conference paper (Refereed)
    Abstract [en]

    In this study, regional climate data was used to investigate the trend of changes for some climatic parameters, i.e. temperature, precipitation and maximum hourly precipitation in four different regions in Sweden. The general trend shows that Sweden will have warmer and wetter climatic conditions by 2100; however, the seasonal changes will affect the system differently, which makes them one of the main factors to be considered. The climatic data was used to determine the probable magnitude of changes by 2100 and to investigate the climate change impacts on urban drainage systems. The problems arising due to such changes were discussed regionally and seasonally and finally BMP methods, as an alternative way, to mitigate the climate change impacts were considered. As an example, green roof was applied to different urbanized conditions to estimate the approximate reduction of the extra water into the drainage system. As well as to investigate how much each of the BMP methods (green roof as an example for opening the further studies) could be useful for city planners towards more secure and sustainable cities in the future against the climate change.

  • 23.
    Moghadas, Shahab
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Gustafsson, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Muthanna, Tone Merete
    Norwegian University of Science and Technology, Department of Hydraulic and Environment Engineering, Trondheim, Norwegian Institute for Water Research (NIVA), Trondheim.
    Marsalek, Jiri
    National Water Research Institute, Environment Canada.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Review of models and procedures for modelling urban snowmelt2016In: Urban Water Journal, ISSN 1573-062X, Vol. 13, no 4, p. 396-411Article in journal (Refereed)
    Abstract [en]

    A literature review of selected snowmelt models or algorithms was undertaken to identify which of these tools could be readily used, or easily modified, for simulating urban snowmelt. In this context, the urban factors influencing snowmelt were classified into three categories: human activities, land use, and the origin of deposited snow; and served to develop a classification of urban snow covers with characteristic properties influencing snowmelt. Finally, the assessment of capabilities of the surveyed models or algorithms to simulate snowmelt for these covers indicated that: (i) only two of the tools addressed the critical characteristics of urban snow covers (for specific cases only), (ii) urban runoff models with snowmelt subroutines offered best operational flexibility, though modifications and/or guidance on input values would be required for satisfactory simulations, and (iii) the review findings should help modellers in choosing a snowmelt simulation tool best serving their task with respect to urban conditions.

  • 24.
    Moghadas, Shahab
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Perttu, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Marsalek, Jiri
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Laboratory study of infiltration into two frozen engineered (sandy) soils recommended for bioretention2016In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 30, no 8, p. 1251-1264Article in journal (Refereed)
    Abstract [en]

    Infiltration of water into two frozen engineered soils of different gradation was studied in laboratory soil columns 1.2 m long and 0.1 m in diameter. Prior to testing, the soil moisture was adjusted to two levels, described by the gravimetric water content of 5 or 10%, soils were compacted to about 80-90% of the maximum dry density, and refrigerated to temperatures ranging from −8 to −2 °C. Water with temperatures 8-9 °C was thereafter fed on the top of columns at a constant head and the times of water break through the column and reaching a steady percolation rate, as well as the percolation rate, were recorded. The soil water content was a critical factor affecting the thawing process; during freezing, soil moisture was converted into ice, which blocked pores, and its melting required high amounts of energy supplied by infiltrating water. Hence, the thawing of soils with higher initial water content was much slower than in lower moisture soils, and water breakthrough and the attainment of steady percolation required much longer times in higher moisture soils. Heat transfer between infiltrating water, soil ice and frozen soil particles was well described by the energy budget equations, which constitute a parsimonious model of the observed processes. The finer grained soil and more compacted soil columns exhibited reduced porosity and required longer times for soil thawing. Practical implications of study results for design of bioretention facilities (BFs) in cold climate include the use of coarse engineered soils and fitting BFs with a drain facilitating soil drainage before the onset of freezing weather. This article is protected by copyright. All rights reserved.

  • 25.
    Moghadas, Shahab
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Westerlund, Camilla
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Gustafsson, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Snowmelt modeling in urban areas: sensitivity analysis of the energy and mass balance method2012Conference paper (Refereed)
    Abstract [en]

    Flooding is one of the main concerns in seeking safe and sustainable urban areas. In many cases the design criteria are based on intense rainfall. It is, therefore, assumed that the peak flow in cities’ drainage systems is due to heavy and fast rainfalls. However snowmelt pattern could be more important for places with cold climate; therefore the need of a better snowmelt and runoff simulation becomes more important particularly when the effects of climate change needs to be considered. Two main methods are basically used for urban snowmelt simulation i.e. temperature index and energy budged methods. Studies done previously show that the energy balance method gives a better estimation for volume and time compare to the temperature index. For urban areas though, it is argued that the data demanding of the energy balance method can be a disadvantage and it could affect the model precision. However, the advances in geographical information systems (GIS) and the requirement for better time resolution than daily have increased the tendency of applying it for urban snow melt. There are couples of studies during recent years e.g. (Ho& Valeo 2005) applying energy budget method in urban areas, even though the efforts basically focused on developing routines and comparing it with the degree day method. There is still a gap in parameter sensitivity analysis especially with two main features of urban snowmelt modeling; firstly, the importance of input data along with difficulties in providing them; and secondly the classification of snow in urban areas based on snow properties. These two concerns were the motives to go one step ahead and to conduct a sensitivity analysis. The aim of the study is therefore to investigate the dependency of the simulation results to the different model parameters as built-in parameters and input data. Such analysis eventually can be used for snow classification which along with GIS technology can provide a reliable platform to simulate snowmelt over an urban catchment more precisely than what the current models are capable of today. Here in this study, a model namely Utah Energy Balance Snow Model (UEB) is used. The model uses a complete energy and mass balance routine to simulate snow accumulation and melt at a point scale. Except using the measured climatic values to run the model, the routines in this model has the capability of producing (simulating) solar radiation and albedo if the measured values are not available. The model has simulated the snow accumulation and melts in rural area with reasonable accuracy in previous studies i.e. (Tarboton et al. 1995). For this research, three snow deposits from 1991 and 1992 are taken to calibrate the model with. The pilot snow packs are identical to municipal snow deposit with density more than natural snow, around 700 Kg/m3. The snowmelt runoff has been measure between March and Jun 1991 and 1992. The necessary input values are collected from Meteorological and Hydrological Institute (SMHI) for the same periods. All input parameters are available on hourly and 3 hourly periods. The method is to run the model with real values collected from SMHI and calibrate it versus the measured data. The model is run using modified parameters to investigate the possible change in the simulation result. Eventually an analysis is done on each parameter and the dependency of the model. An analysis also is done by running the model with different time resolution, i.e. hourly, 3-hourly, and 6-hourly and to investigate the effect of time span in modeling snowmelt and simulation precision.

  • 26.
    Rujner, Hendrik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Leonhardt, Günther
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water. Unit of Environmental Engineering, University of Innsbruck.
    Perttu, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Marsalek, Jiri
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Viklander, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Advancing green infrastructure design: Field evaluation of grassed urban drainage swales2016In: Novatech proceedings 2016, 2016Conference paper (Refereed)
    Abstract [en]

    Grassed drainage swales, which represent common elements of urban green infrastructures, are designed for different soils, flow capacities, dimensions, slopes and vegetation. Their design is often based on local experience rather than technical guidelines, and consequently, the design and performance of grassed swales, with respect to flow capacity and stormwater management objectives may significantly vary from one jurisdiction to another. To improve this situation and reduce design uncertainties, a field study of grassed swales was conducted by assessing their hydrologic performance. A 30-m section of an urban grassed swale in sandy soils, located in the City of Luleå (Northern Sweden), was equipped with a mobile water supply system and instrumented for measuring swale flow characteristics. The water supply system comprised five containers (~ 1 m3 each) providing controlled longitudinal and lateral inflows into the tested swale section. These inflows were selected to mimic stormwater runoff from a typical drainage area. At the first test site, 14 rainfall events of 30- minute duration were simulated and the resulting swale flows and soil moisture conditions were measured. The experimental variables addressed included wet and dry antecedent conditions, and three inflow rates. The preliminary results indicate that the degree of swale inflow attenuation depended on the magnitude of runoff inflow, on the initial soil moisture conditions and that significant volumes of water can be stored and transmitted during the stormwater drainage process.

  • 27.
    Tuomas, Göran
    et al.
    Luleå tekniska universitet.
    Gustafsson, Anna-Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Evaluation of ground thermal conductivity from drilling data2004In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 41, no Suppl 1, p. 241-247Article in journal (Refereed)
    Abstract [en]

    In this paper a new method for evaluating ground thermal conductivity is suggested. The principle is based on ordinary drilling where energy is injected into the borehole in the form of pressurised fluid, mechanical torque, and mechanical feed force, which all dissipate into heat. Part of the heat leaves the borehole with the fluid while the rest is mainly transferred into the formation. By determining the energy flows, ground thermal conductivity can be estimated. This new measurement method would have many advantages. Ground conductivity values would be continuously estimated along the borehole, meaning that values are obtained through the formation. This quality could, for example, be used during production drilling in a mine to instantly detect lithological boundaries, resulting in increased ore extraction efficiency. Energy storage systems could be dynamically designed since the system capacity could be recognized and verified during drilling. Presented simulation results, where realistic drilling parameters were used, show that the method has the potential to be practically applied.

  • 28. Tuomas, Göran
    et al.
    Gustafsson, Anna-Maria
    Nordell, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Thermal response test integrated to drilling2003In: Proceedings: Futurestock 2003, 9th International Conference on Thermal Energy Storage : Warsaw, Poland, September 1 - 4, 2003, Warszawa: PW Publishing House , 2003, p. 411-415Conference paper (Refereed)
1 - 28 of 28
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