Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Velocity variations in ventilated rooms as a method for creating comfort
Univ Gavle, Dept Technol & Built Environm.
2001 (English)In: Market Opportunities for Advanced Ventilation Technology: AIVC 22nd Conference Belgium, 2001Conference paper, Published paper (Refereed)
Abstract [en]

The aim is to develop a new method for comfort in settings with high thermal load in buildings that do not require continuous cooling but cooling only during shorter periods. Example of such buildings is schools. The present ventilation and control systems are designed for supply of air at a constant flowrate or to respond to relatively slow variations in load or step changes in load. The slow variations in load are mainly governed by the diurnal cycle and sudden step changes in load are mainly due to people entering or leaving a room. Systems of today are monotonous in the sense that the indoor climate is kept almost constant over long periods. However, there are indications that intermittent variations in velocities can be beneficial to people's perceived comfort. For example when people feel too warm the introduction of a short "breeze" of "high velocity" air may make them feel more comfortable. One example is window airing. The use of (non-turbulent) variations as a stimulus for creating comfort has not as yet been explored systematically or been technically implemented. The idea is to create velocity variations in the head region on people. Both momentum (mixing ventilation) and pure buoyancy driven (displacement system) ventilation are used for creating velocity variations. In addition to using the ventilation system for introducing velocity variations, stirring generated by propellers (ceiling fans) are used. The paper reports on the velocity field obtained in the occupied zone.

Place, publisher, year, edition, pages
2001.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-6602OAI: oai:DiVA.org:kth-6602DiVA: diva2:11356
Conference
AIVC 22nd Conference Belgium, Brussels, INIVE EEIG, 2001, 'Market Opportunities for Advanced Ventilation Technology'. held at Hilton Bath City Hotel, Bath, United Kingdom, 11th - 14th September 2001
Note

QC 20111220

Available from: 2005-09-20 Created: 2005-09-20 Last updated: 2012-10-23Bibliographically approved
In thesis
1. Technique and human perception of intermittent air velocity variation
Open this publication in new window or tab >>Technique and human perception of intermittent air velocity variation
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Objectives. The main objective of the present thesis was to evolve a controlled intermittent velocity field and to examine the impact of this type of dynamic indoor climate on human’s psychology and physiology. The prediction was that intermittent velocity variation could provide occupants with the desired cooling without causing draught and that this intermittent change of the indoor climate would influence peoples’ affect and cognitive performance.

Methods. All experiments were performed in a classroom-like environment where groups of subjects were exposed to a temperature increase and step changes in air velocity. The changes or intermittent variations in air velocity consisted of elevated speed during five minutes, which were repeated three times. To reduce the influence of individual thermal preferences all measures were collected twice and the statistical analyses were based on the change scores in these measures.

Results. The obtained results showed that, intermittent velocity variation may provide occupants with the desired cooling without causing draught. Subjects exposed to velocity variations were significantly less affected by the temperature rise in the room, compared to the control group. Moreover, the method reduced the expected increase of occupants who perceived the temperature condition as uncomfortable. The findings concerning air movements demonstrate that very few perceived the condition as draughty, after being exposed to the three high velocity pulses.

The results concerning affect showed a significant effect on high activation, in the temperature range 21 - 24oC when the velocity variations made the subjects rate the temperature as slightly lowered over time, they kept their level of activation. In the higher temperature interval, 25 - 27oC, unactivated unpleasantness increased and activated pleasantness decreased significantly more in subjects in the constant velocity condition than it did for subjects in the velocity variation condition. In sum, all results concerning affect, the significant ones and tendencies point in the same direction. Subjects exposed to velocity variation report changes, over time, indicating higher activation and more positive feelings.

No differences in cognitive performances were shown between the air velocity conditions. However, a tendency to a significant result (p = 0.10) in an attention task was shown, indicating that subjects in the velocity variation condition increased their speed in a short-term memory search, compared to subjects in the constant velocity condition.

In the temperature range 21- 24oC, where the perception of the room temperature was measured at 0, 5 and 10 minutes respectively after the last high velocity period, the difference in MTV scores between the two groups, did decrease over time. Ten minutes after the last pulse the difference in MTV scores between the two groups was not significant. This suggests that the high velocity period should be repeated every10 to 15 minutes to keep the expected rise in subjects who judged the thermal conditions as uncomfortable down.

The skin temperature was not affected neither by the rise in ambient temperature (from 21 to 24oC over 80 minutes) nor the periods (3 x 5 minutes) of high velocity. A consequence of this result is that the human temperature regulation system permitted an increased heat loss during the high velocity pulse, and hence a reduction of the body’s internal stored heat. For uncovered body parts the increase in heat loss was 20 % during the high velocity pulse. Summarised over the whole exposure time the three pulses produced a total energy loss that was only 2 % higher compared to constant low velocity.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2005
Keyword
indoor climate
National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:kth:diva-423 (URN)91-7178-137-4 (ISBN)
Public defence
2005-09-29, Sal 202, Hus 33, Högskolan i Gävle, Gävle, 10:30
Opponent
Supervisors
Note
QC 20111221Available from: 2005-09-20 Created: 2005-09-20 Last updated: 2011-12-21Bibliographically approved

Open Access in DiVA

No full text

Search in DiVA

By author/editor
Wigö, Hans
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 67 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf