On the error of calculation of heat gains through walls by methods using constant decrement factor and time lag values

Abstract

Please cite this article as: C.R. Ruivo, P.M. Ferreira, D.C. Vaz, On the error of calculation of heat gains through walls by methods using constant decrement factor and time lag values, Energy and Buildings (2010), doi:10.1016/j.enbuild.2013 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Prediction of the heat gain of external walls: An innovative approach for full-featured excitations based on the simplified method of Mackey-and-Wright

“…However, this is not strictly true since thermal comfort is also influenced by the radiant temperature of the room, which is influenced by the temperature of the envelope's interior surface. In their work [28], Jin and co-workers do not present the formulation of the simplified method they used based on both the heat flux time lag and heat flux decrement factor, nor do they compare results obtained with their «heat-flux» approach against those obtained with «temperature» approaches, like the two investigated by Ruivo et al [25]. Ruivo and co-workers found that the decrement factors determined by the two methods they studied could be related by a multiplicative factor given by the ratio between the interior and overall heat transfer coefficients.…”

“…[6][7][8]. Ruivo et al [25] found that the wall azimuth has but a small influence on the decrement factor but an appreciable influence on the time lag, at least for the simulated wall. They also mention the need for improving the simplified methods in order to extend their use to a large range of wall constructions at arbitrary orientations.…”

“…Both methods tested by Ruivo et al [25] predict the heat flux at the interior surface of the envelop. The results can also be expressed in terms of a temperature difference, which is named total equivalent temperature difference (TETD) in several works [25,27].…”

“…Ruivo et al [25] have tested two such simplified methods, found in the literature, valid for constant indoor temperature and cyclic operation, with daily periodicity, dictated by the external excitation. The two methods differ in the temperature evolution used to evaluate the decrement factor and the time lag: the wall's outer surface or the sol-air temperatures.…”

“…The results can also be expressed in terms of a temperature difference, which is named total equivalent temperature difference (TETD) in several works [25,27].…”