Experimental Analysis of the Function of a Window with a Phase Change Heat Accumulator

Abstract

The article presents the results of long-term field tests and their mathematical analysis regarding the impacts of innovative phase change materials on the energy efficiency of composite windows with various glazing parameters. Research was conducted on six glazing combinations throughout the heating season in a temperate climate in Rzeszów (Poland). The empirical results obtained during the spring months showed an improvement in the monthly heat balance for windows with phase change materials compared to the reference window by as much as 34.09%. In addition, the empirical results allowed the development and verification of a mathematical model describing the transport and distribution of heat within a window with a phase change heat accumulator. The model was made using equations of non-stationary heat flow and an explicit finite difference method using calorimetric thermograms describing the phase change eutectic mixture used in the research. Carrying out the Snedecor–Fischer test proved the statistical adequacy of the developed model in 4 out of 6 tested combinations of glazing units. Good matching of the empirical and theoretical quantities was also confirmed using the quasi-Newton method. The article is a solution to the problem of the effective use of solar energy within transparent building partitions, while presenting a useful mathematical tool that determines potential thermal gains in various climatic conditions.

The Impact of a Mobile Shading System and a Phase-Change Heat Store on the Thermal Functioning of a Transparent Building Partition

“…The demand for sunlight, depending on the time of day and the lifestyle of the inhabitants, should be taken into account. Consideration of the use of mobile shading systems in windows with a phase change cushion is described in [ 24 , 26 ]. The daily profile of demand for sunlight for people working and studying in a 1-shift, 8-h system was taken into account.…”

“…Determination of the thermal gains of transparent building partitions modified with phase change materials, related to the use of a shading system, was determined by means of the heat balance in accordance with papers [ 16 , 24 , 26 , 42 ]. On the basis of empirical and theoretical data, the heat balance was determined as the integral of the density of the heat flux flowing through the window qt as a function of time, according to Equation (1): where A—surface, q t —heat flux density as a function of time and t—time.…”

“…The improvement of the energy efficiency of transparent building partitions containing a phase change material and provided with a shading system, in accordance with [ 24 , 26 , 42 ], can be determined as the temperature difference between the inside air and the inside of the glazing over time as the number of degree hours S th , according to Equation (2): …”

“…The parameters determining suitability are both the value of the enthalpy of the phase change and the temperature range in which it occurs. In the case of building elements, depending on the type of climate and the place of PCM application, the range is between 16–28 °C [ 15 , 16 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. The use of organic phase change materials to modify building partitions is associated with the need to ensure the necessary heat flow between PCM and the external environment [ 27 ].…”

Dynamics of Melting Process in Phase Change Material Windows Determined Based on Direct Light Transmission

“…This allows classifying such components as a dynamic envelope system [4] with changeable transmissivity. An alternative solution that does not suffer from periodic non-transparency is a PCM-window concept developed by Lichołai and Musiał [5] and Hu et al [6]. In any case of a transparent structure filled with a different kind of PCM (paraffins, fatty acids or hydrated salts) the component is non-translucent and low-transmittant when the material is in a solid state and highly transmittant when it is a liquid.…”