The effect of south wall's outdoor absorption coefficient on time lag, decrement factor and temperature variations

Measurement of Heat-Flux of New Type Façade Walls

“…The adequate placement and location of insulation has a positive influence on unsteady heat transfer in the external walls and roofs. The results of the analysis of Kontoleon & Bikas [1] showed that the placement of three equal layers of insulation is the optimal solution for external walls and roofs. Usually, the best performances can be obtained if the insulation layer is near the entrance point of the heat flux.…”

A thermo-activated wall for load reduction and supplementary cooling with free to low-cost thermal water

“…A sinusoidal variation is used to represent the outdoor temperature. The assumption approximates very well the exact meteorological data, and the ambient-air temperature is expressed by Reference [28]:…”

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

“…1 illustrates the simplified physical problem for a wall construction, with n layers of different materials. The physical model adopted considers onedimensional heat flux, similarly to the models that have been used by other authors [6,[11][12][13][14][15]17]. The most important assumptions are: (i) heat conduction takes place along the x direction with no internal heat sources or sinks present, (ii) the properties of building materials are constant, (iii) the superficial temperatures of other elements such as walls, floors, ceiling, furniture are assumed to be equal to the constant indoor air temperature, (iv) the combined surface heat transfer coefficients that account for both convection with the ambient air and radiation with the surrounding surfaces are constant, (v) the thermal contact resistance between adjacent material layers is negligible, (vi) the mass transfer through the material layers is negligible, (vii) the external surface of the envelope is completely dry and in contact with outdoor air, (viii) A c c e p t e d M a n u s c r i p t 9 there is no water vapour condensation on the inner surface of the envelope, (ix) the daily evolutions of outdoor air temperature and solar radiation do not change during the period of simulation.…”

“…Other research found that both parameters depend on the thickness and position of the insulation layer [14] and on the absorptivity of the outer surface of the envelope [15].…”

“…In spite of the significant number of works carried out [11][12][13][14][15], some misleading concepts [11,12] and doubts [13,14] Moreover, according to the best knowledge of the authors, no research was conducted to inspect in detail the validity of these simplified methods, for the actual cases in which the temperature of the outer side of the wall does not perfectly follow a sinusoidal evolution, since it is imposed by the combined effect of the outdoor air and incident radiation flux evolutions. These are the cases that an engineer finds in practice when performing cooling load calculations.…”