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Abstract
A sufficient measurement time is key to the accurate determination of thermal resistance from in-situe heat flux and temperature data. Given some assumed thermal properties of the construction to be measured, this paper presents a means for prediciting an error that might result from anticipated temperature conditions or for estimating the erors that may be attributable to a temperature history. The error prediction procedure is useful for deciding in advance whether to make in-situ thermal resistance measurements, during expected temperature conditions of buildings and of structures that contain hot or cold media. This procedure estimates errors in the calculation of thermal resistance only, that result from obtaining non-steady-state temperature and heat flow data over a finite period of time. Random errors due to instrumentation techniques should be analyzed separately, using propagation of errors or other methods. Errors that result from changes in the apparent thermal conductivity of the constituent materials of the element studies are also beyond the scope of this paper. Such changes may be due to variation in internal temperatures, moisture migration or air movement.
A sufficient measurement time is key to the accurate determination of thermal resistance from in-situe heat flux and temperature data. Given some assumed thermal properties of the construction to be measured, this paper presents a means for prediciting an error that might result from anticipated temperature conditions or for estimating the erors that may be attributable to a temperature history. The error prediction procedure is useful for deciding in advance whether to make in-situ thermal resistance measurements, during expected temperature conditions of buildings and of structures that contain hot or cold media. This procedure estimates errors in the calculation of thermal resistance only, that result from obtaining non-steady-state temperature and heat flow data over a finite period of time. Random errors due to instrumentation techniques should be analyzed separately, using propagation of errors or other methods. Errors that result from changes in the apparent thermal conductivity of the constituent materials of the element studies are also beyond the scope of this paper. Such changes may be due to variation in internal temperatures, moisture migration or air movement.
Date
2/1991
2/1991
Author(s)
S Flanders; R Mack
S Flanders; R Mack
Page(s)
193-220
193-220
Keyword(s)
thermal resistance; heat flux; finite history; mathematical model;
thermal resistance; heat flux; finite history; mathematical model;