Experimental and numerical investigations of the optical and thermal aspects of a PCM-glazed unit

Abstract

This paper reports on the experimental and numerical analysis of the optical and thermal aspects of PCM (Phase Change Material) RT27 when subjected to an irradiation source of energy. The analysis is separated into the thermal and optical characterisation of the PCM using the T-history method and spectrophotometry principles, respectively, and the experimental and numerical performance evaluation of a PCM-Glazed unit. Various relationships describing the variations in the extinction, scattering and absorption coefficients with respect to the liquid fraction/ temperature within the phase change region were developed from the experimental setup, and were validated in a numerical CFD model. The results show that: i) during rapid phase changes, the transmittance spectra from the PCM are unstable, while under stable conditions a visible transmittance value of 90% and 40% are obtained for the liquid and phases, respectively; ii) the radiation scattering effects are more prominent in the solid phase of the PCM, while radiation absorption dominates in the liquid phase; iii) the optical/ radiation performance of PCM can be successfully modelled using the liquid fraction term as the main variable, in a similar way that the enthalpy porosity method is employed for phase change processes; iv) relative to a standard double glazed unit, the addition of PCM improves the thermal mass of the unit during phase change, but depending on specific

Phase Change Materials in Transparent Building Envelopes: A Strengths, Weakness, Opportunities and Threats (SWOT) Analysis

“…So far, the literature has presented different experimental studies on the integration of PCM in glazing units [13,23,24,30,[32][33][34]41,43,44]. Real-scale prototypes of the technology (DGU + PCM) were used to collect data during measurements [25,26,28], and the assembly and the construction of these prototypes were carried out in house laboratories.…”

“…• the geographical distribution of the studies, which also provides an indication of the climatic conditions of the study; • the climatic/seasonal distribution of the studies: winter season (37%) [12][13][14][15][16][17][18][19][20][21][22], mid-season (10%) [14,15,20] and summer (50%) [13][14][15][16][17]20,[23][24][25][26][27][28][29][30][31] season periods; • the most investigated PCM typologies, that have been found to be paraffin wax (60%) [14][15][16]18,19,22,23,[25][26][27][28][29][30][31][32][33][34][35] and salt hydrates (20%) [12,13,…”

“…• in all the papers, the PCM had been macro-encapsulated in containers, that is, glass containers (70%) [12][13][14][15][20][21][22][23][24][25]27,[30][31][32][33][34][35][38][39][40][41], polycarbonate containers (20%) [16,17,19,28,36,42] and aluminium containers (10%) [18,26,29]; • the technologies had predominantly been characterised in outdoor test cells (57%) [14,15,17-22, 24-27,29,31,35] and through laboratory analysis (53%) [12,13,17,20,23,[32][33][34][35][36][37][38][39][40][41][42], while some other studies had been carried out by coupling a modelling activity with an experimental activity (37%) …”

Responsive glazing systems: Characterisation methods, summer performance and implications on thermal comfort

“…Another way to achieve dynamic behaviour of glazing systems is by introducing a phase change material (PCM) within the gap of a double (Goia et al, 2014b;Gowreesunker et al, 2013) or triple glazing unit (S. , or within more-complex glazing components (Grynning et al, 2015(Grynning et al, , 2013. PCMs in glazing systems notably increase their inertial behaviour, smoothing the indoor surface temperature and providing peak load shifting.…”

“…The performance of PCM-enhanced glazing components was investigated by several experimental (Goia et al, 2014bGowreesunker et al, 2013;S. Li et al, 2016) and numerical (Goia, 2012;Ismail et al, 2008;Zhong et al, 2015) studies.…”