Virtual and physical experiments of encapsulated phase change material embedded in building envelopes

Abstract

This paper investigates the temperature and heat flux fields of composite materials containing phase change materials (PCM) for energy efficient buildings. A novel numerical method validated by accurately controlled laboratory experiments is presented for virtual experiments of more complex applications. Considering a finite bounded domain containing one inclusion, the Green’s function technique has been applied to obtain the transient heat transfer response caused by sources on inclusion domains and prescribed boundaries. Based on the Eshelby’s equivalent inclusion method (EIM), the thermal property mismatch between the PCM particle and matrix phases is simulated with a uniformly distributed eigen-temperature gradient field and a fictitious heat source on the particle. Through the combination of EIM and boundary element method, namely the iBEM, the temperature field can be written in terms of the temperature and heat flux on the boundary and the distributed eigen-temperature gradient and heat source on the particle. By using the equivalent heat flux conditions and the specific heat-temperature relationship, the eigen-temperature gradient and fictitious heat source can be solved and the temperature field of the bounded domain can be calculated. This new numerical method has been verified by the finite element simulation and validated with the laboratory measurements of the transient heat transfer within a building block containing a PCM capsule. Parametric studies have also been conducted to study the influences of the PCM location and volume fraction on the temperature field of composites with multiple particles. The virtual experiments demonstrate the energy saving and phase delay by using the PCM-concrete wall panel. This method will be very useful for the design and thermal analysis of building envelopes.