Building-scale experimental validation of a new model for walls with phase change materials

Abstract

The current article presents the building-scale experimental validation of a new model for walls equipped with phase change materials. The one-dimensional conduction heat transfer equation is solved using an explicit finite-difference method coupled with an enthalpy method to consider the variable phase change materials thermal capacity. The model is implemented in the transient system simulation tool simulation tool and referred to as Type 3258, and the method used to couple this component to the multi-zone building (known as Type 56) is discussed. The experimental investigation is performed in two identical full-scale test-cells (only one with phase change materials) exposed to the ambient environment. Experimental data are first used to benchmark a transient system simulation tool simulation model of the test-cell without phase change materials. After calibration, the phase change materials model is experimentally validated with data from the phase change materials-equipped test-cell. Compared to the benchmarking procedure (without phase change materials), the root mean square deviation values between the experiments and the simulations (with phase change materials) are lower or in the same order of magnitude. Simulation accurately reproduces the impact of adding phase change materials to the test-cell as observed in the experiments, such as mitigation and time-shift effects. A discussion about computation time concludes the present study.

Nomenclature

Bi	=	= Biot number [–]
Cp	=	= specific heat [J g−1 K−1]
Fo	=	= Fourier number [–]
H	=	= enthalpy [J kg−1]
h	=	= coefficient of convection [W m−2 K−1]
k	=	= thermal conductivity [W m−1 K−1]
m	=	= mass [g]
n	=	= number of nodes [–]
	=	= heat flow [W]
T	=	= temperature [°C]
t	=	= time [s]
U	=	= heat transfer coefficient [W m−² K−1]
α	=	= thermal diffusivity [m² s−1] or coefficient of absorption [–]
Δt	=	= time-step [s]
Δx	=	= half-interval between 2 nodes [m]
ρ	=	= density [kg m−³]

Subscripts

cw	=	= center of the wall
i	=	= i-node
l	=	= left
r	=	= right
si	=	= inside surface
so	=	= outside surface

Abbreviations

NW	=	= north-west
SW	=	= south-west

Acknowledgments

The authors also would like to thank the energy technology laboratory (Hydro-Québec Research Institute) where the experiments were performed.

Funding

The research work presented in the present article was financially supported by Fonds de Recherche du Québec en Nature et Technologies Hydro-Québec (FRQNT) and Natural Sciences and Engineering Research Council of Canada (NSERC).