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  • 101. Kobayashi, T
    et al.
    Sagara, K
    Yamanaka, T
    Kotani, H
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Prediction of Cross-Ventilation Rate based on stream Tube Analysis Part 2. Basic Characteristics of Stream Tube based on CFD Analysis2006In: Proceedings of Annual meeting of SHASEJ, Kinki Chapter, 2006, p. 143-146Conference paper (Other academic)
  • 102. Kobayashi, T.
    et al.
    Sagara, K.
    Yamanaka, T.
    Kotani, H.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Stream Tube Analysis for Prediction of Cross-ventilation Rate: Part 5 : Characteristics of Stream Tube Analysis on CFD Analysis2006In: Proceedings of Annual Meeting of AIJ, Kinki Chapter, 2006, p. 357-360Conference paper (Other academic)
  • 103. Kobayashi, T.
    et al.
    Sagara, K.
    Yamanaka, T.
    Kotani, H.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Stream Tube Analysis for Prediction of Cross-Ventilation Rate: Part 6 : Discharge Coefficient and Pressure Coefficient of Buildings based on Stream Tube Analysis2006In: Summary of Technical Papers of Annual Meeting of AIJ, 2006, p. 779-780Conference paper (Refereed)
  • 104. Kobayashi, T
    et al.
    Sagara, K
    Yamanaka, T
    Kotani, H
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Stream tube analysis of cross-ventilated simple-shaped model and detached house2007In: The 6th International Conference on Indoor Air Quality, Ventilation & Energy Conservation in Buildings, 2007Conference paper (Refereed)
  • 105.
    Kobayashi, T
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Sakara, K
    Yamanaka, T
    Kotani, H
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Wind driven flow through openings: analysis of the stream tube2006In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 4, no 4, p. 323-336Article in journal (Refereed)
    Abstract [en]

    Wind approaching a building provided with openings on the windward and leeward sides has a choice, either it flows through the openings or flows around and above the building. This choice gives rise to a dominant stream tube containing the fluid flowing through the openings. In this paper the stream tube is analysed based on wind tunnel measurements and CFD simulation. A house model with dimensions 120 mm (Width)×120 mm (Height)×180 mm (Length) was provided with rectangular openings of equal size located opposite each other. The end walls were thin giving rise to a sharp edged opening. The size of the openings expressed as the porosity (opening area divided by the façade area) was 1.3 %, 5.2 %, 11.6 %, 20.7 % and 46.5 %. In the wind tunnel, velocity including velocity fluctuations and pressure were measured along the centre line through the openings. In the CFD prediction it was possible to visualize the stream tube by the method of “flying particles”. This made it possible to explore the change in shape of the stream tube and to calculate the cross-sections of the stream tube at different positions and to know the total pressure distribution within the stream tube cross section. Finally, the discharge coefficient based on stream tube analysis was compared to that from a conventional chamber method.

  • 106.
    Kobayashi, Tomo
    et al.
    Department of Architectural Engineering, Osaka University, Division of Global Architecture, Osaka, Japan.
    Sagara, Kazunobu
    Department of Architectural Engineering, Osaka University, Division of Global Architecture, Osaka, Japan.
    Yamanaka, Toshio
    Department of Architectural Engineering, Osaka University, Division of Global Architecture, Osaka, Japan.
    Kotani, Hisahi
    Department of Architectural Engineering, Osaka University, Division of Global Architecture, Osaka, Japan.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Power transportation inside stream tube of cross-ventilated simple shaped model and pitched roof house2009In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 44, no 7, p. 1440-1451Article in journal (Refereed)
    Abstract [en]

    The ultimate goal of this work is to establish a prediction method based on Power Balance Model for prediction of flow rate through cross-ventilated building. For the establishment of Power Balance Model, the lost power across stream tube sections must be determined in advance. However, the loss of power in the stream tube was not well studied by other researchers but this concerned critical step forms the focus of the present CFD study in which transported power in stream tubes formed at two selected models: (i) a suspended rectangular model, and (ii) a pitched roof single-storey house model standing on a flat ground surface, was documented. For the development of a new method applying to predict the lost power, decrease of the transported power across the stream tubes through both types of models will finally be shown in this paper.

  • 107.
    Kobayashi, Tomohiro
    et al.
    Department of Architectural Engineering, Osaka University, Osaka, Japan.
    Sagara, Kazunobu
    Department of Architectural Engineering, Osaka University, Osaka, Japan.
    Yamanaka, Toshio
    Department of Architectural Engineering, Osaka University, Osaka, Japan.
    Kotani, Hisahi
    Department of Architectural Engineering, Osaka University, Osaka, Japan.
    Takeda, Shogo
    Department of Architectural Engineering, Osaka University, Osaka, Japan.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Stream Tube based Analysis of Problems in Prediction of Cross-Ventilation rate2009In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 7, no 4, p. 321-334Article in journal (Refereed)
    Abstract [en]

    The airflow rate of a building ventilated by wind is usually predicted by using the wind pressure coefficients obtained for a sealed building and discharge coefficients based on measuring the airflow characteristics through an opening in a sealed chamber (chamber method). This can result in the underestimation of wind driven flow through large openings located on opposite sides of a room. In this paper, the discharge coefficient, based on the chamber method, and the actual condition of cross-ventilation are calculated and compared with each other by means of stream tube analysis. The driving pressure based on wind pressure coefficients obtained from a sealed building are also compared with those based on pressures inside the stream tube of the actual flow field representing a porous rather than sealed building. A building model of dimensions 120 mm (width)×120 mm (height)×180 mm (length) was used for the analyses. The size of openings, expressed as the porosity (opening area divided by façade area), was 11.6 %, 20.7 % and 46.5 %. These models were analyzed by CFD simulation and the stream tubes caught by the opening were determined. From the analysis the errors in discharge coefficient and wind pressure coefficient were identified. Finally, the flow rate based on these discharge coefficients and driving pressures were calculated and compared. It is shown that the effect of the underestimation of the discharge coefficients by the chamber method is significant for all cases of porosity studied in this paper. Moreover, it is shown that the use of wind pressure coefficients is not appropriate for the case of extremely large openings.

  • 108. Kobayashi, Tomohiro
    et al.
    Sagara, Kazunobu
    Yamanaka, Toshio
    Kotani, Hisashi
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Prediction of cross-ventilation rate through large openings-problem of conventional method2007In: Roomvent 2007: 10th International Conference on Air Distribution In Roooms. Vol 3, 2007, p. 103-112Conference paper (Refereed)
  • 109.
    Landström, Ulf
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Buller: störningseffekter2007In: Nordisk lärobok i audiologi, Bromma: CA Tegnér , 2007, , p. 8Chapter in book (Other academic)
  • 110.
    Landström, Ulf
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Man and Noise2006In: Baltic-Nordic Acoustical Meeting, 2006Conference paper (Refereed)
  • 111.
    Leal, V
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Maldonado, E
    An analytical model for the outflow in a ventilated window with known surface temperatures2004In: Roomvent 2004 Coimbra Portugal, 2004Conference paper (Refereed)
  • 112. Li, Y
    et al.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Hui, S
    Robustness of Air Distribution in Plenum-Based Ductless Ventilation Systems2004In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 3, no 2, p. 105-118Article in journal (Other academic)
    Abstract [en]

    This paper introduces a concept of robustness of an air distribution method, which is defined as being capable of meeting the ventilation requirements during varying operational conditions. The robustness performance may be particularly important when the system allows individual control of the supply air parameters. As a preliminary example, plenum-based (ductless) air distribution methods are studied using computational fluid dynamics. Among the four basic air distribution methods in plenum-based systems, it is found that the floor supply and ceiling return system does not always produce the conventional displacement ventilation system performance when the heat sources are not concentrated. The ceiling supply with ceiling return produces the best robustness performance over a wide range of supply velocities.

  • 113. Lindberg, F
    et al.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Westerberg, Ulla
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för byggnadskvalitet.
    Claesson, Leif
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Windiness in an Urban Space described with different methods2004In: Cost Action C14-Impact of wind and Storm on City Life and Built Environment, 2004Conference paper (Other academic)
  • 114.
    Linden, Elisabet
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Broberg, Björn
    Olsson, Sören
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Towards making the indoor climate visible in practice2004In: The 9th International Conference on Air Distribution in Rooms, 2004, p. 168-169Conference paper (Other academic)
  • 115.
    Linden, Elisabet
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Cehlin, Mathias
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för energi- och maskinteknik.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Temperature and velocity measurements on a diffuser for displacement ventilation with whole field methods2000In: The 7th International Conference on Air Distribution in Rooms, 2000Conference paper (Other academic)
  • 116.
    Linden, Elisabet
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Elvsén, Per-Åke
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Whole field mapping of temperature pattern in the near zone of an elevated displacement diffuser2002In: The 8th International Conference on Air Distribution in Rooms, 2002, p. 765-768Conference paper (Other academic)
    Abstract [en]

    This paper deals with the effect of discharging the air from a diffuser elevated above the floor. The temperatures have been measured and the airflow patterns visualised close to a diffuser for displacement ventilation, results from the whole-field method (using infrared thermography) were images of different colours representing different temperatures of the air close to the diffuser.. The aim of the measurements was to see how the elevations of the diffuser above floor level and the thermal jet length of the supply could affect the near zone.

  • 117.
    Linden, Elisabet
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Hellström, Jennie
    Cehlin, Mathias
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för energi- och maskinteknik.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Virtual reality presentation of temperature measurements on a diffuser for displacement ventilation2001In: The 4th International Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings, 2001Conference paper (Other academic)
  • 118.
    Linden, Elisabet
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Westerberg, Ulla
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för byggnadskvalitet.
    Wind field in an urban space explored by different methods2006In: The 6th International Conference on Urban Climate (ICUC6), 2006Conference paper (Other academic)
  • 119.
    Linden, Elisabet
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Todde, Valentino
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Indoor Low Speed Air Jet Flow: Three-Dimensional Particle Streak Velocimetry1998In: The 6th International Conference on Air Distribution in Rooms, 1998Conference paper (Refereed)
  • 120.
    Ljung, Robert
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Kjellberg, Anders
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Long reverberation time decreases recall of spoken information2009In: Building Acoustics, ISSN 1351-010X, Vol. 16, no 4, p. 301-311Article in journal (Refereed)
    Abstract [en]

    The aim of the study was to explore if a long reverberation time has the same effect on recall of spoken words as background noise was shown to have in a previous study. A further aim was to study the influence of working memory capacity on performance in these conditions. Thirty-two subjects performed a word recall and a sentence recognition test. They repeated each word to ensure correct identification. A reading span test measured their working memory capacity. Performance of the word recall task was impaired by the long reverberation time. The effect was most evident in the primacy part of the word list. No correlation was found between reading span score and recall performance.

  • 121.
    Ljung, Robert
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Kjellberg, Anders
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Recall of spoken words presented with a prolonged reverberation time2008In: ICBEN 2008: Machantucket Connecticut, USA, July 21-25, 2008 : the 9th Congress of the International Commission on Biological Effects of Noise : Noise as a Public Health Problem : Proceedings (edited by Barbara Griefahn), Dortmund: IfADo , 2008, p. 403-409Conference paper (Refereed)
    Abstract [en]

    The aim of the study was to explore if a long reverberation has the same effect on recall of spoken words as background noise was shown to have in a previous study. A further aim was to study the role of working memory capacity for performance in these conditions. Thirty-two subjects performed a word recall and a sentence recog-nition test. They repeated each word to ensure correct identification. A reading span test measured their working memory capacity. Performance of the word recall task was impaired by the long reverberation time. The effect was most evident in the pri-macy part of the word list. The reading span score was unrelated to recall perform-ance.

  • 122.
    Ljung, Robert
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Kjellberg, Anders
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Green, Anne-Marie
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Memory of a text heard in noise2008In: ICBEN 2008: Machantucket Connecticut, USA, July 21-25, 2008 : the 9th Congress of the International Commission on Biological Effects of Noise : Noise as a Public Health Problem : Proceedings (edited by Barbara Griefahn), Dortmund: IfADo , 2008, p. 450-453Conference paper (Refereed)
    Abstract [en]

    When spoken information is presented in unfavourable listening conditions a larger part of the available and limited information processing resources must be allocated to the identification of the words spoken. This leaves fewer resources for the further processing of the speech (the interpretation and storing of the information). In such circumstances understanding and memory of speech might be impaired although each word has been correctly heard. This hypothesis was confirmed in two previous studies where memory of a word list was shown to be impaired when presented in unfavourable listening conditions: unfavourable signal/noise ratio (Kjellberg, Ljung & Hallman, 2008) and a too long reverberation time (Ljung & Kjellberg, in press). Kjellberg et al. also found that the noise effect was weaker the better the working memory capacity (as measured with a reading span task).

  • 123.
    Ljung, Robert
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Sörqvist, Patrik
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Hygge, Staffan
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Effects of Road Traffic Noise and Irrelevant Speech on Children’s Reading and Mathematical Performance2009In: Noise & Health, ISSN 1463-1741, E-ISSN 1998-4030, Vol. 11, no 45, p. 194-198Article in journal (Refereed)
    Abstract [en]

    Irrelevant speech in classrooms and road traffic noise adjacent to schools have a substantial impact on children's ability to learn. Comparing the effects of different noise sources on learning may help construct guidelines for noise abatement programs. Experimental studies are important to establish dose-response relationships and to expand our knowledge beyond correlation studies. This experiment examined effects of road traffic noise and irrelevant speech on children's reading speed, reading comprehension, basic mathematics, and mathematical reasoning. A total of 187 pupils (89 girls and 98 boys), 12-13 years old, were tested in their ordinary classrooms. Road traffic noise was found to impair reading speed (P < 0.01) and basic mathematics (P < 0.05). No effect was found on reading comprehension or on mathematical reasoning. Irrelevant speech did not disrupt performance on any task. These findings are related to previous research on noise in schools and the implications for noise abatement guidelines are discussed.

  • 124.
    Ljung, Robert
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Sörqvist, Patrik
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Kjellberg, Anders
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Green, Annemarie
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Poor Listening Conditions Impair Memory for Intelligible Lectures: Implications for Acoustic Classroom Standards2009In: Building Acoustics, ISSN 1351-010X, Vol. 16, no 3, p. 257-265Article in journal (Refereed)
    Abstract [en]

    This paper reports two experiments on the effects of degraded speech signals on memory for spoken lectures. Experiment 1 showed that broadband noise impairs university students’ memory for a spoken lecture, even though the participants heard what was said. Experiment 2 showed that reverberation has detrimental effects to school adolescents’ memory for spoken lectures, similar to broadband noise. The results suggest that poor listening conditions (resulting from background noise and/or long reverberation time) impair memory and learning, even if the conditions allow the listeners to hear what is said. Since the goal for students and pupils attending to lectures is to remember the lecture rather than just hearing what is said, the results presented here indicate that standards for acceptable signal-to-noise ratios and reverberation times in buildings designed for learning should consider the distinction between speech intelligibility and memory. Standards should be based on memory criteria instead of intelligibility criteria.

  • 125.
    Lundström, Hans
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Moshfegh, Bahram
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för energi- och maskinteknik.
    Temperature dependence of convective heat transfer from fine wires in air: a comprehensive experimental investigation with application to temperature compensation in hot-wire anemometry2007In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 32, no 2, p. 649-657Article in journal (Refereed)
    Abstract [en]

    Heat transfer from a fine wire to air has been experimentally investigated. High accuracy measurements, where both the air temperature and wire temperature have been varied systematically and independently have made it possible to map the behavior of the heat transfer process for different velocities, air temperatures, and wire temperatures. Based on these results a compensation method is proposed which makes it possible to temperature compensate hot wires of large aspect ratio and at low Reynolds numbers for anemometry measurements with velocity calibration only at one air temperature.

  • 126.
    Mattsson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    A Note on the Thermal Comfort in Displacement Ventilated Classrooms2000In: Air distribution in rooms (Roomvent 2000): Proceedings of the 7th international conference on air distribution in rooms, 2000, p. 1129-1134Conference paper (Refereed)
    Abstract [en]

    Nineteen university students were asked about their thermal comfort while attending ordinary lessons in a displacement ventilated test room of typical classroom size. Two different ceiling heights were tested. Both the general temperature level and the strength of the vertical temperature stratification in the room increased continuously during the lessons due to the presence of the students, however slower with the higher ceiling. The temperature stratification of the air eventually reached a strength of 3.1°C/m, which, according to international standards, should cause some complaints about the thermal comfort. There was however no indication of that the students could feel this stratification. The fact that the vertical radiative temperature asymmetry was comparatively small in the room – due to radiative heat exchange between the interior surfaces – is believed to be a major reason for this insensitivity of the students to the vertical air temperature stratification.

  • 127.
    Mattsson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Displacement Ventilation in a Classroom: Influence of Contaminant Position and Physical Activity1998In: Proc. 19th AIVC Conference, Oslo, Norway., 1998Conference paper (Refereed)
    Abstract [en]

    This study describes how the air quality in a displacement ventilated classroom can be influenced by the position of a contaminating person, and by the activity of a person who walks around in the room. Tracer gas measurements have been performed in a full scale mock-up of a classroom, with person simulators at the student’s desks.

    The spreading of contaminants from a person seems to be strongly dependent on the position of the person. The closer the contaminating person sits to the outlet terminal(s), the less of his/hers contaminants are spread in the room. Paradoxically, people sitting furthest away from the air supply were found to be provided with the least contaminated air. Physical activity, produced by a walking person, tends to increase the concentration of contaminants emitted from people in the room, whereas the air exchange efficiency actually can benefit from it. At all levels of activity tested in this study the displacement ventilation system provided significantly better air quality than a mixing system would. The temperature gradient in the occupied zone was rather high during these steady-state experiments, and it was only marginally affected by the movements of a person.

  • 128.
    Mattsson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Removal of airborne particles of different sizes in classrooms using portable air cleaners2007In: Roomvent 2007, 13-15 June 2007 Helsinki, Finland: Scanvac Conference : proceedings, abstract book, 2007Conference paper (Refereed)
    Abstract [en]

    Portable electrostatic air cleaners (precipitators) were tested in six different classrooms during ordinary lessons. The number concentration of airborne particles in the classrooms was measured using optical particle counters, which separated the particle recordings into six different size fractions in the range 0.3 μm to >25 μm. It was found that the effectiveness of the air cleaners in cleaning the classroom air was decreasing significantly with increasing particle size. For the smallest particles measured, 0.3-0.5 μm, the measured effectiveness was 76 %, whereas for the particle size fraction 10-25 μm it was only 33 %. This reduced effectiveness for the large particles can be explained by the removal process of particle deposition onto room surfaces. The removal rate due to deposition seems to be competitive with the removal rate of the air cleaners as regards large particles. It appears that the deposition effect often needs to be taken into account in effectiveness assessments for particulate air cleaners.

  • 129.
    Mattsson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Vertical distribution of occupant-generated particles in a room with displacement ventilation2002In: Indoor Air 2002: 9th international conference on indoor air quality and climate, 2002, p. 509-514Conference paper (Refereed)
    Abstract [en]

    The vertical distribution of airborne particles in a room ventilated according to the displacement principle was measured using a vertically conveyed particle counter. The supply air was absolute-filtered and the particles generated through office-like activity of people. In general, particle concentrations increased with height, indicating a displacement effect. This effect improved with ventilation rate. A threshold-size of the particles could be discerned, above which the displacement effect started declining. The measured threshold-size agreed well with calculations based on the settling velocity of the particles and the hypothetical vertical piston-flow velocity of the room air (ventilation rate divided by floor area). At the ventilation rates tested (normal to high), the threshold-size was in the range 5-10 µm. Slightly negative concentration gradients were observed for large particles at the lowest ventilation rate. Hence, if hazardous substances are known to be associated with fairly large particles, the use of displacement ventilation is questionable.

  • 130.
    Mattsson, Magnus
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Andersson, Lars T
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för naturvetenskap.
    Birch and grass pollen allergens in filtered office indoor air2008In: Indoor air 2008: proceedings of the 11. International Conference on Indoor Air Quality and Climate, Technical University of Denmark, Kgs.Lyngby 2008, Kgs Lyngby: Technical university of Denmark , 2008Conference paper (Refereed)
    Abstract [en]

    In an experimental field study, airborne particulate birch and grass pollen allergens were sampled with a cascade impactor on the roof of an office building in the centre of a middle-sized town in Sweden. The impactor separated particles into eight size fractions. Simultaneously, inhalable pollen allergens in the indoor air were sampled in offices of the building. Significant amounts of the outdoor pollen allergens were found on particles much smaller than the pollen grains. These small particles could penetrate the fine filters (quality F6) of the building’s ventilation system. By taking into account the effectiveness of the installed ventilation filters, the pollen allergen concentration indoors could be well predicted, thus pointing out the supply air as the main source of indoor pollen allergens. Comparison of data from workdays with those from weekends indicated that secondary emissions of pollen allergens brought indoors by people (on clothes, hair, shoes etc.) were insignificant.

  • 131.
    Mattsson, Magnus
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Andersson, Lars T
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för naturvetenskap.
    Jansson, Anders
    Stockholms Universitet, ITM.
    Holmquist, Leif
    Timanställd vid HiG.
    Vesterberg, Olof
    Timanställd vid HiG.
    Alm Kübler, Kerstin
    Naturhistoriska riksmuséet, Palynologiska laboratoriet.
    Ekebom, Agneta
    Naturhistoriska riksmuséet, Palynologiska laboratoriet.
    Ventilation filter efficiency for particles and grass pollen allergens2009In: Proceedings of the 9th International Healthy Buildings Conference and Exhibition: HEALTHY BUILDINGS 2009, Paper No: 460. / [ed] Santanam, S., Bogucz, E.A., Peters, C., Benson, T., 2009Conference paper (Refereed)
    Abstract [en]

    In an experimental study, commonly used ventilation fine filters were tested regarding their efficiency in collecting airborne particles and grass pollen allergens from outdoor air. Grass pollen allergen and particle number concentrations were measured before and after the filters, enabling collection efficiency calculations. Simultaneously, the size distribution of grass pollen allergens was measured in outdoor air using a cascade impactor. The study confirms previous indications that pollen allergens occur in the outdoor air as particles much smaller than pollen grains, and can penetrate ventilation filters to a larger extent than might be expected. The initially high collection efficiency of synthetic, electrostatically charged filters declined significantly with time of use (dust load), whereas glass fiber filters showed steady performance. A slight tendency for pollen allergenic matter to penetrate ventilation filters more than other airborne particles was noted, but no difference in the response to electrostatic charge of filters could be seen.

  • 132.
    Mattsson, Magnus
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Bjørn, Erik
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Nielsen, Peter
    Simulating People Moving in Displacement Ventilated Rooms1997In: Proc. Healthy Buildings/AIQ ‘97, Washington DC, USA. / [ed] Wood JE, Grimsrud DT, Boschi N, 1997Conference paper (Refereed)
    Abstract [en]

    A displacement ventilation system works better the more uni-directional the air flow through the ventilated room is: from floor to ceiling. Thus, from an air quality point of view, there should be as little vertical mixing of the room air as possible. It is therefore comprehensible that physical activity in the room – like peoples movements – in previous studies has been shown to influence the effectiveness of the ventilation. In this study we have compared results from previous tests, where a cylindrical person simulator was used, to results obtained when using a person simulator of more human-like shape. The main results verify previous findings: if the movements are not very slow, they have a detrimental effect on ventilation effectiveness and on the air quality in the breathing zone of the inhabitants. Some quantitative differences were found between using the simple and the detailed person simulator, although the qualitative results were about the same.

  • 133.
    Mattsson, Magnus
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Hygge, Staffan
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Effect of Particulate Air Cleaning on Perceived Health and Cognitive Performance in School Children During Pollen Season2005In: Indoor Air 2005: Proceedings of the 10th international conference on indoor air quality and climate, 2005, p. 1111-1115Conference paper (Refereed)
    Abstract [en]

    Cleaning of room air from particulate contaminants was performed using electrostatic air cleaners (precipitators) in four classrooms of 12-year old pupils. The air cleaners were active/inactive according to a cross-over design for 2 + 3 weeks during pollen season. Health questionnaires and cognitive tests were used to investigate the impact of air cleaning on perceived health and on cognitive skills that relate to schoolwork and learning (semantic and episodic memory, logical reasoning, attention, reading comprehension). Pupils stating themselves as being sensitive to airborne particulate contaminants, such as pollen and pet allergens, experienced somewhat less irritation in airways and eyes when the air cleaners were active (p=0.02). The most sensitive pupils also scored about 25% higher on the cognitive test relating to semantic memory when the air cleaners were active (p=0.015). No significant effects were however found for the four other cognitive skills.

  • 134.
    Mattsson, Magnus
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Smedje, Greta
    Holmquist, Leif
    Vesterberg, Olof
    Wålinder, Robert
    Mixing and displacement ventilation compared in classrooms; distribution of particles, cat allergen and CO22003In: Proceedings from Healthy Buildings 2003: 7th International conference, 2003, p. 458-464Conference paper (Refereed)
    Abstract [en]

    Mixing ventilation and displacement ventilation were compared in an intervention study in classrooms. Particles, cat allergen and CO2, were measured in classroom air at different levels above the floor, during regular lessons. With mixing ventilation, the particle concentration tended to decrease with height, with a stronger gradient occurring for larger particles. With displacement ventilation, the particle concentration increased with height, except for particles >25 µm. The displacement system thus tended to have a slight upward displacement effect on most of the particles. Significant correlations were found between concentrations of cat allergen and particles in the size fraction 1–10 µm. The particle and cat allergen concentration at breathing height did not, however, differ significantly between the two ventilation systems. CO2 was about 10% lower with displacement ventilation. A fairly high level of physical activity of the pupils is believed to have had significant dispersing effect on the airborne contaminants.

  • 135.
    Mattsson, Magnus
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Stojanovic, Bojan
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för byggnadskvalitet.
    Elfman, Lena
    Effect of Particulate Air Cleaners on the Content of airborne Dust and Cat Allergen in Classrooms2004In: Roomvent 2004: 9th international conference on air distribution in rooms, 2004Conference paper (Refereed)
    Abstract [en]

    Electrostatic air cleaners (precipitators) were tested in four classrooms during ordinary lessons for four weeks. Airborne dust in the classrooms was collected on filters using two different kinds of samplers: IOM-sampler and a new kind of ionizing sampler. The amount of collected dust was evaluated by visual inspection (“filter blackening”) and the content of cat allergen was measured using an amplified ELISA assay. It was found that the filter blackening was 64% lower when the air cleaners were active than when they where inactive (p<0.001). This suggests that the air cleaners were effective in reducing the content of airborne particulate matter. The reduction in cat allergen appeared however to be less substantial. The variance of the allergen data was unexpectedly large, presumably due to relatively few allergen-carrying particles in the sampled air. It is believed that larger sampling volumes are needed to get more reliable data of airborne cat allergen in spaces where the allergen is emitted indirectly.

  • 136.
    Nilsson, Håkan
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Landström, Ulf
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Kjellberg, Anders
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Exponering och upplevelser av trafikbuller på arbetsplatser2006Report (Other academic)
  • 137.
    Nilsson, Håkan O.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Comfort climate evaluation with thermal manikin methods and computer simulation models2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Increasing concern about energy consumption and the simultaneous need for an acceptable thermal environment makes it necessary to estimate in advance what effect different thermal factors will have on the occupants. Temperature measurements alone do not account for all climate effects on the human body and especially not for local effects of convection and radiation. People as well as thermal manikins can detect heat loss changes on local body parts. This fact makes it appropriate to develop measurement methods and computer models with the corresponding working principles and levels of resolution. One purpose of this thesis is to link together results from these various investigation techniques with the aim of assessing different effects of the thermal climate on people. The results can be used to facilitate detailed evaluations of thermal influences both in indoor environments in buildings and in different types of vehicles.

    This thesis presents a comprehensive and detailed description of the theories and methods behind full-scale measurements with thermal manikins. This is done with new, extended definitions of the concept of equivalent temperature, and new theories describing equivalent temperature as a vector-valued function. One specific advantage is that the locally measured or simulated results are presented with newly developed “comfort zone diagrams”. These diagrams provide new ways of taking into considera-tion both seat zone qualities as well as the influence of different clothing types on the climate assessment with “clothing-independent” comfort zone diagrams.

    Today, different types of computer programs such as CAD (Computer Aided Design) and CFD (Computational Fluid Dynamics) are used for product development, simulation and testing of, for instance, HVAC (Heating, Ventilation and Air Conditio-ning) systems, particularly in the building and vehicle industry. Three different climate evaluation methods are used and compared in this thesis: human subjective measure-ments, manikin measurements and computer modelling. A detailed description is presented of how developed simulation methods can be used to evaluate the influence of thermal climate in existing and planned environments. In different climate situations subjective human experiences are compared to heat loss measurements and simulations with thermal manikins. The calculation relationships developed in this research agree well with full-scale measurements and subject experiments in different thermal environments. The use of temperature and flow field data from CFD calculations as input produces acceptable results, especially in relatively homogeneous environments. In more heterogeneous environments the deviations are slightly larger. Possible reasons for this are presented along with suggestions for continued research, new relationships and computer codes.

  • 138.
    Nilsson, Håkan O.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Evaluation and visualisation of perceived thermal conditions2004In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 92, no 6, p. 714-716Article in journal (Refereed)
    Abstract [en]

    Investigations have been made on ways to evaluate and visualise the perceived thermal climate. Thermal interaction with windows, heating, ventilation and seating influence the occupant's thermal situation. When this information on the physical thermal climate is linked together with human thermal sensation in "comfort-zone diagrams", valuable knowledge about the thermal situation can be visualised. Thermal manikin measurements of local climate disturbances with two different thermal manikins are found to be well correlated with the thermal sensation experienced by panels of subjects exposed to the same conditions. Differences both in manikin shape and construction, as well as testing conditions and panel members, make limit lines differ at some points. Comfort diagrams can be defined by equivalent temperature (t(eq)) limit lines; however, a consequence of individual and experimental variations is that it is not an optimal solution to have diagrams with absolute limit lines, rather a range of t(eq) values, forming new "comfort-zone diagrams". This improvement provides a more appropriate base for assessment of a complex local thermal climate, and opens up the possibility of a general profile that can be used with different manikins, possibly also different methods, in a variety of environments. However, more data from validation experiments with subjects and different methods will contribute to the development of a more general evaluation concept.

  • 139.
    Nilsson, Håkan O.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Heta ämnen - mitt i vintern: rapport från Ashraes vintermöte 2006 i Chicago2006In: Energi & Miljö, ISSN 1101-0568, no 3, p. 48-49Article in journal (Other (popular science, discussion, etc.))
  • 140.
    Nilsson, Håkan O.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    How to Build and Use a Virtual Thermal Manikin Based on Real Manikin Methods2006In: Proceedings of the 6th International Thermal Manikin and Modeling Meeting, 2006Conference paper (Other academic)
    Abstract [en]

     It has always been valuable to be able to make early decisions in thermal climate investigations. The development of virtual thermal manikins (VTM) and computer simulated persons (CSP) has become an important complement to traditional evaluation of the thermal environment. This paper describes how to build a VTM within a commercial computational fluid dynamics code (CFD). The methods are based on human experiments and real thermal manikin measurements.

    Unfortunately, too few of the theories behind thermal manikin simulations are available in the public domain. Many researchers and companies still use several in-house codes for all or essential parts of their calculations. This paper provides information on how to build the geometry of the manikin in three different commercial CFD codes (CFX (R), Star-CD (R) and Fluent (R)). More information and descriptions are also given on how to connect the VTM to the CFD calculations and make the system interact in real time throughout the full iteration process.

  • 141.
    Nilsson, Håkan O.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Improved evaluation of the local thermal environment with clothing independent comfort zone diagrams2005In: Environmental ergonomics XI: proceedings of the 11th International Conference, 22-26 May, 2005, Ystad, Sweden, Lund: Lunds universitet , 2005Conference paper (Other (popular science, discussion, etc.))
  • 142.
    Nilsson, Håkan O.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö. European and International Standardisation, Sweden.
    Local evaluation of thermal comfort2006In: International Journal of Vehicle Design, ISSN 0143-3369, E-ISSN 1741-5314, Vol. 42, no 1-2, p. 8-21Article in journal (Refereed)
    Abstract [en]

    Increasing demand for a comfortable cabin environment makes it necessary, as early as the construction phase, to estimate what effect different factors will have on the driver and passenger. Full-scale measurements and numerical simulations have been carried out in order to investigate how well computational fluid dynamics (CFD) and thermal manikins are able to predict the perceived thermal climate. The heat loss from real or virtual manikins interacts with the environment around the body, as well as thermal interaction with windows; ventilation and seat are influencing the manikins. When manikin heat loss is linked to human thermal sensations in new comfort zone diagrams, the local as well as total thermal situation can be clearly presented. Simulations of this type will enable engineers to make better decisions and early predictions in the design and construction process, improving the thermal comfort in the vehicle environment.

  • 143.
    Nilsson, Håkan O.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Lokal bedömning av klimatpåverkan innebär förbättringar och förenklingar2005In: Energi & Miljö, ISSN 1101-0568, no 12, p. 57-59Article in journal (Other (popular science, discussion, etc.))
  • 144.
    Nilsson, Håkan O.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Med människan som kontrollpunkt2005In: VVS-Forum, ISSN 0346-4644, no Oktober 05, p. 18-20Article in journal (Other (popular science, discussion, etc.))
  • 145.
    Nilsson, Håkan O.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Teknisk beskrivning av termiska manikiner: mät- och simuleringsmetoder som utgår från människors klimatupplevelser2006In: Energi & Miljö, ISSN 1101-0568, no 3, p. 56-58Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    Det är nu aktuellt att göra simuleringar av energiförbrukning och inomhusmiljö för att snabbt ge de effektivaste förslagen på energisparåtgärder. Med verkliga och virtuella termiska manikiner kan man undersöka hur människor kommer att uppleva de olika klimatsituationerna redan innan de uppstår.

    Termiska manikiner är formade som människokroppen. De registrerar värmeförluster över hela sin yta i alla riktningar samtidigt, exakt som människor. Genom att bestämma storleken på värmeavgivningen kan en klimatbedömning göras för såväl enskilda kroppsdelar som för hela kroppen. Precis som för människor påverkar kläderna resultatet av mätningen. Med mindre och tunnare kläder blir mätdockan mer känslig för termisk påverkan från omgivningen. Det är därför viktigt att beskriva vilka kläder man använder och att använda komfortzondiagram vid utvärderingen av resultaten.

  • 146.
    Nilsson, Håkan O.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Thermal Comfort Evaluation with Virtual Manikin Methods2005In: Indoor air 2005: proceedings of the 10th International Conference on Indoor Air Quality and Climate, Beijing: Tsinghua University Press , 2005, p. 138-142Conference paper (Other (popular science, discussion, etc.))
  • 147.
    Nilsson, Håkan O.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Thermal comfort evaluation with virtual manikin methods2007In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 42, no 12, p. 4000-4005Article in journal (Refereed)
    Abstract [en]

    Computational fluid dynamics has become an important tool in the prediction of thermal comfort in occupied spaces. Despite its ability to predict temperature and velocity fields, it is more difficult to evaluate the degree of thermal comfort experienced by an occupant. This article describes the construction of a new numerical thermal manikin, with new comfort evaluation methods based on data from thermal manikin measurements as well as subjective results from several hundred experiments. The level of thermal comfort is highly dependent on the local environment. Human beings respond differently to local heat transfer in different parts of their bodies. It is suggested for that reason that local results from manikins should be presented in new clothing independent comfort zone diagrams. The research presented in here is intended to be used to evaluate system solutions that provide improved thermal climate in many different everyday situations, e.g. all types of buildings and vehicles.

  • 148.
    Nilsson, Håkan O.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Thermal manikin simulation using experimental correlations and clothing independent comfort zone diagrams2006In: ASHRAE Winter Meeting 2006, 2006Conference paper (Other (popular science, discussion, etc.))
  • 149.
    Nilsson, Håkan O.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Virtual mannequins make comfort a reality2004In: CD adapco Dynamics, no Fall 04, p. 31-32Article in journal (Other (popular science, discussion, etc.))
  • 150.
    Nilsson, Håkan O.
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Brohus, Henrik
    Aalborg University DK.
    Nielsen, Peter V.
    Aalborg University DK.
    Modeling of thermal manikin heat loss in a comfort evaluation benchmark test2007In: Roomvent 2007, 13-15 June 2007 Helsinki, Finland: Scanvac Conference : proceedings, abstract book, Helsinki: Finvac , 2007Conference paper (Refereed)
12345 101 - 150 of 214
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