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Blomqvist, Claes
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Publications (10 of 14) Show all publications
Blomqvist, C. (2009). Distribution of Ventilation Air and Heat by Buoyancy Forces inside Buildings: an Experimental Study. (Doctoral dissertation). Stockholm: KTH
Open this publication in new window or tab >>Distribution of Ventilation Air and Heat by Buoyancy Forces inside Buildings: an Experimental Study
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The main task of the ventilation system in a building is to maintain the air quality and (together with the heating or cooling system) the thermal climate at an acceptable level within the building. This means that a sufficient amount of ventilation air at the appropriate temperature and quality must be supplied to satisfy thermal comfort and air quality demands and that this air is distributed to the parts of the building where people reside. Air movements caused by buoyancy forces can determine the distribution of ventilation air within buildings. The purpose of this thesis is to advance the state of knowledge of buoyancy-driven air movements within buildings and to determine their importance both for ventilation air distribution and the maintenance of thermal comfort and air quality in buildings. The work is focused on studying thermally-driven air movements through large openings, both horizontal and vertical (i.e. doorways). The properties of a special type of thermally-driven currents, so called gravity currents, have also been explored. Large vertical openings like doorways are important for air exchange between rooms within a building. Air movements through doorways separating rooms with different air temperatures are often bidirectional and the buoyancy-driven flow rates are often greater than those caused by the mechanical ventilation system alone. Bidirectional flows through doorways can effectively spread contaminants, for example, from a kitchen or a hospital rooms, yet the results of this study indicate that the conversion of a thermally-driven bidirectional flow to a unidirectional flow via an increase of the mechanically forced flow rate requires forced flows that are more than three times greater than the thermally-driven flows. Experiments conducted in this project indicate that the resistance to buoyancy-driven flows in horizontal openings is significantly greater than that in vertical openings. Model tests have shown, however, that this problem may be mitigated if a simple model of a staircase located in the centre of the room (being ventilated) is linked to the horizontal ventilation opening. Gravity currents in rooms occur in connection with so called displacement ventilation as cool gravity currents propagate along the floor that are driven by the density difference of the ventilation air and the ambient, warmer air within the room. As these gravity currents easily pass obstacles and to a certain extent are self-controlling, they can effectively distribute the cool air within rooms in a building. Likewise, warm gravity currents occur when warmer air introduced in a room rises and spreads along the ceiling plane. One application where warm gravity currents may be used to advantage is when converting buildings from electric heating to district hot water heating thus, avoiding the introduction of an expensive hydronic heating system. This report includes a full-scale laboratory study of the basic properties of thermally-driven warm air gravity currents in a residential building and examines the possibilities of using the resulting air movements for the distribution of ventilation air as well as heat. Results from laboratory tests show that this conversion method may prove effective if certain conditions on the layout of the building are fulfilled.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. p. xi, 56
Keywords
building ventilation, thermal forces, buoyancy, gravity currents, large openings, heating, air quality, forced convection, free convection
National Category
Building Technologies
Identifiers
urn:nbn:se:hig:diva-4550 (URN)978-91-7415-322-4 (ISBN)
Public defence
2009-06-09, 33:202, Kungsbäcksvägen 47, Gävle, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2009-06-14 Created: 2009-06-05 Last updated: 2018-03-13Bibliographically approved
Blomqvist, C. (2009). Kan man styra luftfördelningen i en byggnad med hjälp av ventilationssystemet?. Forskning (4), 46-46
Open this publication in new window or tab >>Kan man styra luftfördelningen i en byggnad med hjälp av ventilationssystemet?
2009 (Swedish)In: Forskning, ISSN 1654-8876, no 4, p. 46-46Article, review/survey (Other (popular science, discussion, etc.)) Published
Keywords
temperaturdifferens, luftströmmar
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:hig:diva-7711 (URN)
Available from: 2010-10-05 Created: 2010-10-05 Last updated: 2018-03-13Bibliographically approved
Blomqvist, C. (2008). Conversion of Electric Heating in Buildings: an Unconventional Alternative. Energy and Buildings, 40(12), 2188-2195
Open this publication in new window or tab >>Conversion of Electric Heating in Buildings: an Unconventional Alternative
2008 (English)In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 40, no 12, p. 2188-2195Article in journal (Refereed) Published
Abstract [en]

To decrease the electric energy used for heating buildings it has become desirable to convert direct electrical heating to other heat sources. This paper reports on a study of the possibility of using an unconventional method for conversion to avoid installing an expensive hydronic system. The conversion method combines the ventilation and heating systems and uses air instead of water for distribution of heat within the building, taking advantage of thermal forces and the special properties of gravity currents. Full-scale tests have been carried out in a test apartment inside a laboratory hall where the conditions could be controlled. Temperatures and efficiency of ventilation have been measured to ensure that the demands with respect to thermal climate and air exchange were fulfilled. The results show that it is possible to use the method for heating and ventilation when converting the heating system, but further work has to be done to develop a detailed solution that works in practice.

Keywords
thermal forces, large openings, gravity currents, electrical heating, conversion, heat transfer, district heating
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-2006 (URN)10.1016/j.enbuild.2008.06.012 (DOI)000260276200010 ()2-s2.0-52149112514 (Scopus ID)
Available from: 2008-09-26 Created: 2008-09-26 Last updated: 2018-03-13Bibliographically approved
Stymne, H., Emenius, G., Boman, C. & Blomqvist, C. (2007). Comparison between measured and simulated long term variation of ventilation in an extract ventilated house. In: Proceedings of IAQVEC 2007: The 6th international conference on indoor air quality, ventilation & energy conservation in buildings. Vol. 3 (pp. 161-168).
Open this publication in new window or tab >>Comparison between measured and simulated long term variation of ventilation in an extract ventilated house
2007 (English)In: Proceedings of IAQVEC 2007: The 6th international conference on indoor air quality, ventilation & energy conservation in buildings. Vol. 3, 2007, p. 161-168Conference paper, Published paper (Refereed)
Abstract [en]

Using a passive tracer gas technique, 1 and 2 week averages of local mean ages of air have been estimated in an occupied detached single family house in mid-Sweden during one year. In this paper the measurement result is compared with the result of transient simulation of ventilation using the CONTAM program. The simulation shows that the whole-house air change rate is dominated by the infiltration due to mechanically created pressure difference as long as the outdoor temperature difference exceeds approx. 10 °C. At lower outdoor temperature, the natural driving force becomes increasingly more important increasing the local air change rate (local ACH) in the basement. However, the local ACH on the ground floor is almost independent of indoor-outdoor temperature difference and completely dominated by the mechanical extract. The result from the simulation can reproduce the result of the measurement in satisfactory detail without using wind pressure data.

Keywords
Ventilation, Passive tracer gas, Local mean age of air, Simulation, CONTAM
Identifiers
urn:nbn:se:hig:diva-909 (URN)978-4-86163-069-9 (ISBN)
Available from: 2007-12-04 Created: 2007-12-04 Last updated: 2018-03-13Bibliographically approved
Karimipanah, T., Awbi, H., Sandberg, M. & Blomqvist, C. (2007). Investigation of air quality, comfort parameters and effectiveness for two floor-level air supply systems in classrooms. Building and Environment, 42(2), 647-655
Open this publication in new window or tab >>Investigation of air quality, comfort parameters and effectiveness for two floor-level air supply systems in classrooms
2007 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 42, no 2, p. 647-655Article in journal (Refereed) Published
Abstract [en]

The method of distributing the outdoor air in classrooms has a major impact on indoor air quality and thermal comfort of pupils. In a previous study, ([11] Karimipanah T, Sandberg M, Awbi HB. A comparative study of different air distribution systems in a classroom. In: Proceedings of Roomvent 2000, vol. II, Reading, UK, 2000. p. 1013-18; [13] Karimipanah T, Sandberg M, Awbi HB, Blomqvist C. Effectiveness of confluent jets ventilation system for classrooms. In: Idoor Air 2005, Beijing, China, 2005 (to be presented).) presented results for four and two types of air distribution systems tested in a purpose built classroom with simulated occupancy as well as computational fluid dynamics (CFD) modelling. In this paper, the same experimental setup has been used to investigate the indoor environment in the classroom using confluent jet ventilation, see also ([12] Cho YJ, Awbi HB, Karimipanah T. The characteristics of wall confluent jets for ventilated enclosures. In: Proceedings of Roomvent 2004, Coimbra, Portugal, 2004.) Measurements of air speed, air temperature and tracer gas concentrations have been carried out for different thermal conditions. In addition, 56 cases of CFD simulations have been carried to provide additional information on the indoor air quality and comfort conditions throughout the classroom, such as ventilation effectiveness, air exchange effectiveness, effect of flow rate, effect of radiation, effect of supply temperature, etc., and these are compared with measured data.

Keywords
air distribution index; school ventilation; full-scale measurements; CFD; displacement system; wall confluent jets system; ventilation effectiveness
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:hig:diva-17828 (URN)10.1016/j.buildenv.2005.10.016 (DOI)000245165700015 ()2-s2.0-33748939765 (Scopus ID)
Available from: 2014-11-09 Created: 2014-11-09 Last updated: 2018-03-13Bibliographically approved
Björling, M., Stymne, H., Mattsson, M. & Blomqvist, C. (2007). Ventilation measurements combined with pollutant concentration measurements discriminates between high emission rates and insufficient ventilation. In: IAQVEC 2007 Indoor Air Quality Ventilation and Energy Conservation: sustainable Buildings. P. 2. Paper presented at 6th International Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings: Sustainable Built Environment, IAQVEC 2007, 28-31 October 2007, Sendai, Japan (pp. 393-400). , 2
Open this publication in new window or tab >>Ventilation measurements combined with pollutant concentration measurements discriminates between high emission rates and insufficient ventilation
2007 (English)In: IAQVEC 2007 Indoor Air Quality Ventilation and Energy Conservation: sustainable Buildings. P. 2, 2007, Vol. 2, p. 393-400Conference paper, Published paper (Refereed)
Abstract [en]

High local concentrations of a pollutant can be the result of high local emission rates of the pollutant or insufficient ventilation. Using tracer gases to map the ventilation in multi-zone buildings combined with measurements of the local pollutant concentration provide the means to discriminate between these causes. In a similar manner, the propagation rate of pollutants from a source to a target zone and the emission rate of the pollutants at the source may be determined quantitatively.

The paper presents both the theoretical framework for the techniques and experimental examples of the proposed methods.

National Category
Building Technologies
Identifiers
urn:nbn:se:hig:diva-984 (URN)
Conference
6th International Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings: Sustainable Built Environment, IAQVEC 2007, 28-31 October 2007, Sendai, Japan
Available from: 2009-10-13 Created: 2007-12-05 Last updated: 2018-03-13Bibliographically approved
Blomqvist, C. & Sandberg, M. (2004). Air Movements through Horizontal Openings in Buildings: A Model Study. The International Journal of Ventilation, 3(1), 1-10
Open this publication in new window or tab >>Air Movements through Horizontal Openings in Buildings: A Model Study
2004 (English)In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 3, no 1, p. 1-10Article in journal (Refereed) Published
Abstract [en]

A building contains a number of large openings like doors and staircases. When the temperature of the spaces connected by these openings differs, the difference in density will cause air movements through them. Horizontal air movements through vertical openings in buildings like doors and windows are well investigated while studies of air movements through horizontal openings like stairwells are less frequent and therefore this work is focusing on this case.

The paper reports on an experimental study of the possibility of using buoyancy forces to distribute air and heat through horizontal openings. The experiments have been carried out in a scale model with water as the operating fluid.

The result of the study shows that the flow rate through a horizontal opening is roughly half of the flow rate through a vertical opening for the same conditions, probably caused by the more complex flow pattern in the horizontal opening. A staircase below the horizontal opening will guide the flow somewhat and will cause a small increase of the fluid exchange through the opening.

Keywords
air movement, staircase, horizontal openings, salt bath method
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-1622 (URN)10.1080/14733315.2004.11683898 (DOI)
Available from: 2007-10-04 Created: 2007-10-04 Last updated: 2018-04-03Bibliographically approved
Blomqvist, C. & Sandberg, M. (2002). A Note on Air Movements through Horizontal Openings in Buildings. In: The 8th International Conference on Air Distribution in Rooms: Inividual Controlled Environment. Paper presented at ROOMVENT 2002, 8-11 September 2002, Copenhagen, Denmark.
Open this publication in new window or tab >>A Note on Air Movements through Horizontal Openings in Buildings
2002 (English)In: The 8th International Conference on Air Distribution in Rooms: Inividual Controlled Environment, 2002Conference paper, Published paper (Refereed)
Identifiers
urn:nbn:se:hig:diva-2810 (URN)87-989117-0-8 (ISBN)
Conference
ROOMVENT 2002, 8-11 September 2002, Copenhagen, Denmark
Available from: 2007-10-31 Created: 2007-10-31 Last updated: 2018-03-13Bibliographically approved
Blomqvist, C. & Sandberg, M. (2000). Spread of Gravity Currents in Multi Room Buildings. In: The 7th International Conference on Air Distribution in Rooms: Ventilation for Health and Sustainable Environment. Paper presented at ROOMVENT 2000, Reading, UK, 9-12 July 2000.
Open this publication in new window or tab >>Spread of Gravity Currents in Multi Room Buildings
2000 (English)In: The 7th International Conference on Air Distribution in Rooms: Ventilation for Health and Sustainable Environment, 2000Conference paper, Published paper (Refereed)
Identifiers
urn:nbn:se:hig:diva-2806 (URN)0 080 43017 1 (ISBN)
Conference
ROOMVENT 2000, Reading, UK, 9-12 July 2000
Available from: 2007-10-31 Created: 2007-10-31 Last updated: 2018-03-13Bibliographically approved
Blomqvist, C. & Sandberg, M. (1998). Transition from Bi-directional to Unidirectional Flow in a Doorway. In: Elisabeth Mundt, Tor-Göran Malmström (Ed.), ROOMVENT '98 : proceedings: 6th International Conference on Air Distribution in Rooms. Paper presented at ROOMVENT '98 (pp. vol 2, 539-546). Stockholm
Open this publication in new window or tab >>Transition from Bi-directional to Unidirectional Flow in a Doorway
1998 (English)In: ROOMVENT '98 : proceedings: 6th International Conference on Air Distribution in Rooms / [ed] Elisabeth Mundt, Tor-Göran Malmström, Stockholm, 1998, p. vol 2, 539-546Conference paper, Published paper (Refereed)
Abstract [en]

The air flow in a doorway is governed by density difference caused by temperature difference and pressure difference caused by mechanical ventilation. Tests have been carried out in a unique indoor test house where the room to room to temperature difference could be controlled very accurately with a new control system. In addition to these tests some tests were carried out in a scale model with water as the operating fluid. Two main criteria of unidirectional flow in a doorway have been explored:

 

1a.     The recorded mean velocity is unidirectional

1b.     The neutral height is equal to the height of the door

2.       Unidirectional flow in the sense that

 

there is no transfer of contaminant from one room to another. To explore condition one the velocity profile in the doorway have been recorded by transversing the door opening. Condition two has been explored by using tracer gas technique.

Place, publisher, year, edition, pages
Stockholm: , 1998
Series
Meddelande / Installationsteknik, Kungl. Tekniska högskolan, ISSN 0284-141X ; 45
Keywords
Air flow pattern, Air velocity, Convection flows, Full-scale experiments, Tracer gas
Identifiers
urn:nbn:se:hig:diva-4545 (URN)
Conference
ROOMVENT '98
Available from: 2009-06-05 Created: 2009-06-05 Last updated: 2018-03-13Bibliographically approved

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