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  • 1.
    Hang, Jian
    et al.
    University of Hong Kong.
    Li, Yuguo
    University of Hong Kong.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Wind Conditions and Ventilation in high rise long Street Models2010In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 45, no 6, p. 1353-1365Article in journal (Refereed)
    Abstract [en]

    We regarded high-rise cities as obstacles and channels to wind. We first studied wind conditions and ventilations in idealized high-rise long street models experimentally and numerically with a constant street width (W = 30 mm), variable street heights (H = 2 W, 2.5W, 3W, 4W), variable street lengths (L = 47.4W, 79W. 333W, 667W) and a parallel approaching wind. The flow rates penetrating into windward entries are a little larger than the reference flow rate in the far upstream free flow through the same area with windward entries in all models. The stream-wise velocity decreases along the street as some air leaves upwardly across street roofs. Near the leeward entry, there is a downward flow which brings some air into the street and results in an accelerating process. In the neighborhood scale long streets (L = 47.4W and 79W), wind in taller streets is stronger and the ventilation is better than a lower one. For the city scale long streets (L = 333W and 667W), a constant flow region exists where the vertical velocity is zero and the stream-wise velocity remains constant. In such regions, turbulent fluctuations across the street roof are more important to air exchange than vertical mean flows. In a taller street, the process to establish the constant flow conditions is longer and the normalized balanced horizontal flow rate is smaller than those in a lower street. In the city scale long streets, the turbulence exchange rate can be 5-10 times greater than the mean flow rate. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.

  • 2.
    Hang, Jian
    et al.
    Department of Mechanical Engineering, The University of Hong Kong, Hong Kong.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Li, Yugo
    Department of Mechanical Engineering, The University of Hong Kong, Hong Kong.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Flow mechanisms and flow capacity in idealized long-street models2010In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 45, no 4, p. 1042-1053Article in journal (Refereed)
    Abstract [en]

    It is an open question whether a street network of a city has a certain flow capacity characterizing the flow that can pass through the street network. It s our hypothesis that at least the simple street network has a certain flow capacity. With the purpose of exploring this we studied numerically and experimentally the flow capacity in some idealized long-street models continuously lined with buildings and exposed to a parallel approaching wind. The height of all the models is the same (H = 69 mm). Three groups of models were studied: models with the same uniform street width (W = H) but different lengths (L = 21.7H, 43.5H, 72.5H); models with the same length (L = 43.5H) but different uniform width (W = H, 2H, 4H); and models with a change of width at half distance, L/2. In the last of the three cases, the width of the upstream half was always the same (W1 = H), but there was a wider (W2 = 1.25H, 1.5H, 2H) or narrower (W2 = 0.75H, 0.5H) downstream half. We normalized flow rates by a reference flow rate equal to the flow rate through an opening far upstream with the same area as the windward entry. The normalized flow rate through the windward entry was about 1.0 in all cases. For a sufficiently long-street models, a flow balance is established, creating a fully developed region with a constant horizontal flow (flow capacity) and zero vertical mean velocity. The street length does not affect the flow capacity but as expected the width of the street affects the flow capacity.

  • 3.
    Hayati, Abolfazl
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Evaluation of two air infiltration models on a church2013In: Conference proceedings: Cultural heritage preservation – 3rd European Workshop on Cultural Heritage Preservation, 2013, p. 47-53Conference paper (Refereed)
    Abstract [en]

    Air infiltration in ancient churches and other historical and monumental buildings is of great importance considering moisture transfer, energy consumption, thermal comfort and indoor surface soiling. Two of the most established models for simulatingand predicting air infiltration in buildings are the Lawrence BerkeleyLaboratory (LBL) model and the Alberta air Infiltration Model (AIM-2). The applicability of these models in superimposing wind and buoyancy driven infiltration in large single zone buildings such as churches are evaluated in this study by comparing model predictions with field measurements in a 19thcentury stone church. Both tested air infiltration models yielded significant positive correlations between measured and predicted data, and it is concludedthat the AIM-2 model works better than the LBL model for the studied church. Both models tend however to over-predict the air infiltration rate significantly. The over‑predictions were larger in cases with high wind speed and it seems that the models are more fragile in wind dominating conditions. Inclusion of crawl space coefficients in the AIM-2 model improved however the predictions, especially at high wind speeds. It seems that models of the tested kind can be useful in predicting air infiltration in churches and similar buildings, but that some empirically attained model coefficients might need some adjustment to suit this kind of buildings better.

  • 4.
    Kobayashi, Tomohiro
    et al.
    Ritsumeikan University.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Kotani, Hisashi
    Osaka University.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Experimental investigation and CFD analysis of cross-ventilated flow through single room detached house model2010In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 45, no 12, p. 2723-2734Article in journal (Refereed)
    Abstract [en]

    Cross-ventilation is a complicated flow problem and difficult to control because wind exhibits a large degree of variation. The paper focuses on three items: a) to clarify and understand some of the basic characteristics of airflow as the influence of the opening size on the windward vortex and the leeward wake; b) to explore what information about the flow above the ground can be retrieved from pressure measurements on the ground; and c) to explore the accuracy of CFD. To meet these objectives, wind tunnel tests and CFD analyses were carried out. The studied object was a detached-house model provided with two openings. The size of these openings was changed in a wide range from narrow cracks to large openings. In the experiments, pressure measurements on the ground and PIV measurements were made. The internal flow was visualized with the sand erosion method. Pressure measurement on a floor surface is a relatively easy and an inexpensive method. In this experiment, the windward and leeward areas in particular were investigated to understand flow pattern and to confirm correspondence between flow pattern and recorded pressure on the ground. Those measurements show the difference in flow at different size openings in terms of the vortex on the windward side and the wake. When the size of the opening exceeded a certain value the near wake on the leeward side disappeared and on the windward side the vortex disappeared. The pressure distribution, flow pattern, and velocity profile are shown and compared between measurement and CFD.

  • 5.
    Linden, Elisabet
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Control of jets for ventilation by using different combinations of blowing and suction2011In: Proceedings Roomvent 2011 Trondheim Norway Juni 2011, Tapir Academic Press , 2011Conference paper (Refereed)
  • 6.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Broström, Tor
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Lindström, Svante
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Fan Convectors vs. Bench heaters in Churches – impact on air velocities2011In: EEHB 2011: Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström & Lisa Nilsen, Visby: Gotland University Press, 2011Conference paper (Refereed)
    Abstract [en]

    Air movements in churches affect the deposition rate of airborne particles on surfaces, and hence influence soiling of valuable artifacts of different kinds. Sooting from candles and the thermal comfort of people is also affected by indoor air velocities. In an experimental field study, two different heating systems were compared regarding their effect on room air velocities in a church: air-to-air heat pumps with indoor fan convectors vs. a combination of bench heaters and radiators. Hot-sphere and 3-D sonic anemometers were used to record air velocities in the church. Strong buoyant air flows were found both in the supply air flow path of the heat pumps and above the bench heaters, but the air velocities were rather low outside of these air currents. A ~25 cm thick downdraught air flow was found along walls and windows, with a magnitude that was similar at both heating systems and much larger than the outdoor air infiltration rate.

  • 7.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Broström, Tor
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Lindström, Svante
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Impact of heating system on air velocities in a medieval stone church2011In: Roomvent 2011: 12th International conference on air distribution in rooms, Trondheim, Norge: Tapir Akademisk Forlag , 2011Conference paper (Refereed)
    Abstract [en]

    The air flow pattern and magnitude of air velocities in churches and other historic buildings are of interest since they influence the deposition rate of airborne particles on surfaces, and hence affect soiling of valuable artifacts of different kinds. Increased air movements might also cause enhanced sooting from candles and it has an influence on the thermal comfort of people. The type of installed indoor heating units is likely to be important here since these usually induce substantial air movements through natural or forced convection. In an experimental field study, two different heating systems were compared regarding their effect on room air velocities in a medieval stone church: air-to-air heat pumps with indoor fan convectors vs. a combination of bench heaters and radiators. Hot-sphere anemometers were used to record air velocities in the near-zone of the heat pumps and their surroundings, and 3-D sonic anemometers were used to measure downdraught air velocities at the surfaces of a wall and a window. Smoke was used to visualize air flow patterns.

    It was found that the heat pumps caused strong buoyant air jets that rose to the ceiling, but that the air velocities were rather low outside of these jets. The bench heaters caused buoyant plumes, which also seemed to attain rather high air velocities and reach the ceiling. As regards downdraught along wall and window, no significant difference between the two heating systems could be seen, although there was a tendency towards slightly higher air velocities at these surfaces when the heat pumps were in use. Since the air flow pattern at the surfaces appeared similar, also the particle deposition mechanisms and soiling rate can be expected to be similar.

  • 8.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Lindström, Svante
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Methods to Identify Air Leakages in the Building Envelope of Churches2011In: EEHB 2011: Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström & Lisa Nilsen, Visby, Sweden, 2011Conference paper (Refereed)
    Abstract [en]

    Frequently there is a wish to reduce the natural ventilation rate in churches in order to save energy and/or improve the thermal comfort. It is then often difficult to ascertain exactly which the dominating leaks in the building envelope are, and where tightening measures would be most effective. A number of different methods to identify these leakages are discussed here. It appears that valuable help can be attained by a combination of several measuring techniques, including IR-thermography, tracer gas and pressure measurements. These techniques can also be useful in verifying the effect of tightening measures.

  • 9.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Lindström, Svante
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Tracer gas techniques for quantifying the air change rate in churches – field investigation experiences2011In: Proc. Roomvent 2011: 12th International conference on air distribution in rooms / [ed] Hans Martin Mathisen, Trondheim, Norge: Tapir Akademisk Forlag , 2011Conference paper (Refereed)
    Abstract [en]

    Two different tracer gas techniques for quantifying the air change rate were tested in three naturally ventilated churches. The techniques were the decay method (or tracer gas dilution method) and a passive tracer gas method. It appeared that the room air in the studied churches tended to be fairly well mixed when the churches are heated, presumably due to strong natural convection air currents occurring at heat sources and cooler outer building surfaces. This seems to entail that both the decay and the passive method are fairly easy to apply during times of heating. It then doesn’t seem to matter much were the tracer gas is injected or where it is sampled. During non-heating periods, however, spatial differences in tracer gas concentrations were observed, making tracer gas measurements more difficult to perform.

  • 10.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Lindström, Svante
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Hayati, Abolfazl
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Fan pressurization method for measuring air leakage in churches – wind and stack induced uncertainties2013In: Conference proceedings: Cultural heritage preservation – 3rd European Workshop on Cultural Heritage Preservation / [ed] A. Troi and E. Luchi., 2013, p. 63-68Conference paper (Refereed)
    Abstract [en]

    The air leakage of the building envelope of ancient churches and other historical and monumental buildings has impact on energy consumption, thermal comfort, humidity and indoor surface soiling. To measure the air leakage in such large and naturally ventilated single-zone buildings is however challenging, especially due to wind and buoyancy (stack) induced disturbances. This study describes experiences in this regard, attainedat field tests where the fan pressurization technique (“Blower door”) was employed. Reference is made to the European test standard EN 13829. Also results of wind-tunnel tests are utilized. It is shown that both buoyancy and wind at commonly occurring conditions can cause significant uncertainty in fan pressurization tests, and that some of the directions in the standard might need to be strengthened or amended. While the uncertainty in measured air leakage rate at the standard (high) pressure of 50 Pa may be small, the predictions of the air leakage rate occurring at realistically (low) indoor-outdoor pressures tend to suffer from significant uncertainty. That uncertainty is then conveyed to later utilizations of the test results, e.g. building energy modeling and prediction. It is also shown that the wind induced pressure at buildings like churches extends a considerable way out into the surroundings of the building; in the order of two times the building height. This has particular importance when choosing a reference point for outdoorpressure measurement.

  • 11.
    Sandberg, Mats
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Etheridge, David W
    University of Nottingham, UK.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Wind tunnel measurements of pressure distribution on  the facade of a church2011In: Proc. EEHB 2011: Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström & Lisa Nilsen, Visby: Gotland University Press, 2011Conference paper (Refereed)
    Abstract [en]

    Elderly churches have a unique shape with their high towers and long naves. There seems to be few if any reported measurement of pressure distribution on churches. Churches are naturally ventilated buildings and therefore when the wind speed is high  the  wind becomes an important driving force for ventilation. A model in scale 1: 200 was built of a 19th century Swedish church provided with a crawl space.The pressure on the façade of the model was recorded in 42 points. With the aim of studying the ventilation of the church, dedicated measuring points were located on windows, doors and in the positions corresponding to the location of the openings in the crawl space.  Some field trials were undertaken with the scope of measuring the time history of the static pressure on the façade in some positions corresponding to measuring points on the wind tunnel model. Examples of these measurements are  reported in the paper. With the aim of measuring the “region of influence” on the ground caused by the church, also the static pressure on the ground was recorded in the wind tunnel tests.  The static pressure on ground was recorded with a pressure plate provided with 400 pressure taps arranged in a quadratic pattern.

  • 12.
    Sandberg, Mats
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Etheridge, David W
    University of Nottingham, UK.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Wind tunnel measurements of pressure distribution on the façade and surrounding ground of a church2011In: Roomvent 2011: 12th International conference on air distribution in rooms / [ed] Hans Martin Mathisen, Trondheim, Norge: Tapir Akademisk Forlag , 2011Conference paper (Refereed)
    Abstract [en]

    Elderly churches have a unique shape with their high towers and long naves. There seems to be few if any reported measurement of pressure distribution on churches. Churches are naturally ventilated buildings and therefore when the wind speed is high  the  wind becomes an important driving force for ventilation.

    A model in scale 1:200 was built of a 19th century Swedish church provided with a crawl space. The pressure on the façade of the model was recorded in 42 points. With the aim of studying the ventilation of the church dedicated measuring points were located on windows, doors and in the positions corresponding to the location of the openings in the crawl space. 

    Some field trials were undertaken with the scope of measuring the time history of the static pressure on the façade in some positions corresponding to measuring points on the wind tunnel model. Examples of these measurements are  reported in the paper.

    With the aim of measuring the “region of influence” on the ground caused by the church, also the static pressure on the ground was recorded in the wind tunnel tests.  The static pressure on ground was recorded with a pressure plate provided with 400 pressure taps arranged in a quadratic pattern.

  • 13.
    Sandberg, Mats
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Neophytou, Marina
    University of Cyprus.
    Fokaides, Paris
    University of Cyprus.
    Panagiotou, I.
    Ioannou, I.
    University of Cyprus.
    Petrou, M.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Batchvarova, Ekaterina
    Bulgarian Academy of Science.
    Videnov, P.
    Dimitroff, B.
    Bulgarian Academy of Science.
    Ivanov, A.
    Towards optimization of urban planning and architectural parameters for energy use minimization in Mediterranean cities2011In: WREC 2011, 2011Conference paper (Refereed)
  • 14.
    Sandberg, Mats
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy engineering.
    A wind tunnel method for screening the interaction between wind turbines in planned wind farms2011In: Wrec 2011 Linköping Sweden 2011, 2011Conference paper (Refereed)
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