Heat Flow in Building Components, Experiment and Analysis
(1998) In Report TABK 1016. Abstract
 Three building components exposed to natural climate were studied: a dynamic insulation in the ceiling of a house, an outer wall and one window in the same wall. The term dynamic insulation implies that part of the inlet or exhaust air passes through the insulation of a house. A house with dynamic insulation was continuously measured for approximately a year and a half. The performance of the dynamic insulation was estimated by using hourly values of the temperature distribution inside the insulation. The air flow through the insulation was calculated as the air flow that best matched the measured temperature distribution. For the calculations both the transient and steady state heat transfer equations were used. The dynamic Uvalue for... (More)
 Three building components exposed to natural climate were studied: a dynamic insulation in the ceiling of a house, an outer wall and one window in the same wall. The term dynamic insulation implies that part of the inlet or exhaust air passes through the insulation of a house. A house with dynamic insulation was continuously measured for approximately a year and a half. The performance of the dynamic insulation was estimated by using hourly values of the temperature distribution inside the insulation. The air flow through the insulation was calculated as the air flow that best matched the measured temperature distribution. For the calculations both the transient and steady state heat transfer equations were used. The dynamic Uvalue for the insulation was about 0.05 W/m2°C for the ceiling. This corresponds to a dynamic energy efficiency for the insulation of 35%. Taking into account that only 40% of the total supply air passed through the insulation, the total efficiency became 14%. A heat exchanger for ventilation air have an efficiency above 60%. The general conclusion from the measurements was that dynamic insulation requires a house constructed to much higher standards, as far as air leakage is concerned, in order to work properly.
An outer ambient wall with a window were studied with both theoretical analyses and measurements performed under conditions with natural climate. The method used was to estimate the heat flow through wall and window from measured temperatures and solar radiation. The longwave radiation was calculated from surface temperatures. The convective heat transfer was calculated as the difference between the heat flow through the building element and the longwave radiation. With the onedimensional dynamic heat transfer model for the window which included shortwave radiation it was possible to measure the continuous heat flow through a window from temperature sensors and solar radiation measurements. With the onedimensional finite difference model for the heat transfer through the wall it was possible to calculate the heat flow through a wall from temperature sensors. It was possible to continuously measure the convective heat transfer coefficient on the inner surface of a wall or a window. The accuracy was not very good: at best ±15% for the window and ± 20% for the wall. Even with this low accuracy the effect of different heating and ventilation strategies on the inside could clearly be detected. The results showed that the importance of the ventilation design and the position of the radiator is crucial. Local convective heat transfer coefficients may be more than 10 times the expected, due to ventilation or position of the radiator. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/record/18850
 author
 Wallentén, Petter ^{LU}
 opponent

 Ph D Tjelflaat, Per Olaf, Norway Institute of Technology
 organization
 publishing date
 1998
 type
 Thesis
 publication status
 published
 subject
 keywords
 radiation exchange, longwave, shortwave, transient, frequency analysis, finite difference, measurements, wall, window, heat transfer coefficient, convective, full scale, natural climate, in situ, counter flow insulation, heat transfer, dynamic insulation, temperature, building, solar radiation, window model, Building construction, Byggnadsteknik
 in
 Report TABK
 volume
 1016
 edition
 TABK 98/1016
 pages
 246 pages
 publisher
 Department of Building Science, Lund Institute of Technology
 defense location
 Auditorium B, School of Architecture
 defense date
 19980611 10:15
 external identifiers

 other:ISRN: LUTADL/TABK1016SE
 ISSN
 11034467
 ISBN
 ISSN 11034467
 language
 English
 LU publication?
 yes
 id
 cb3d4919b935494a81f3373cde34d736 (old id 18850)
 date added to LUP
 20070524 12:32:56
 date last changed
 20180529 09:55:43
@phdthesis{cb3d4919b935494a81f3373cde34d736, abstract = {Three building components exposed to natural climate were studied: a dynamic insulation in the ceiling of a house, an outer wall and one window in the same wall. The term dynamic insulation implies that part of the inlet or exhaust air passes through the insulation of a house. A house with dynamic insulation was continuously measured for approximately a year and a half. The performance of the dynamic insulation was estimated by using hourly values of the temperature distribution inside the insulation. The air flow through the insulation was calculated as the air flow that best matched the measured temperature distribution. For the calculations both the transient and steady state heat transfer equations were used. The dynamic Uvalue for the insulation was about 0.05 W/m2°C for the ceiling. This corresponds to a dynamic energy efficiency for the insulation of 35%. Taking into account that only 40% of the total supply air passed through the insulation, the total efficiency became 14%. A heat exchanger for ventilation air have an efficiency above 60%. The general conclusion from the measurements was that dynamic insulation requires a house constructed to much higher standards, as far as air leakage is concerned, in order to work properly.<br/><br> <br/><br> An outer ambient wall with a window were studied with both theoretical analyses and measurements performed under conditions with natural climate. The method used was to estimate the heat flow through wall and window from measured temperatures and solar radiation. The longwave radiation was calculated from surface temperatures. The convective heat transfer was calculated as the difference between the heat flow through the building element and the longwave radiation. With the onedimensional dynamic heat transfer model for the window which included shortwave radiation it was possible to measure the continuous heat flow through a window from temperature sensors and solar radiation measurements. With the onedimensional finite difference model for the heat transfer through the wall it was possible to calculate the heat flow through a wall from temperature sensors. It was possible to continuously measure the convective heat transfer coefficient on the inner surface of a wall or a window. The accuracy was not very good: at best ±15% for the window and ± 20% for the wall. Even with this low accuracy the effect of different heating and ventilation strategies on the inside could clearly be detected. The results showed that the importance of the ventilation design and the position of the radiator is crucial. Local convective heat transfer coefficients may be more than 10 times the expected, due to ventilation or position of the radiator.}, author = {Wallentén, Petter}, isbn = {ISSN 11034467}, issn = {11034467}, keyword = {radiation exchange,longwave,shortwave,transient,frequency analysis,finite difference,measurements,wall,window,heat transfer coefficient,convective,full scale,natural climate,in situ,counter flow insulation,heat transfer,dynamic insulation,temperature,building,solar radiation,window model,Building construction,Byggnadsteknik}, language = {eng}, pages = {246}, publisher = {Department of Building Science, Lund Institute of Technology}, school = {Lund University}, series = {Report TABK}, title = {Heat Flow in Building Components, Experiment and Analysis}, volume = {1016}, year = {1998}, }