Development and numerical validation of a new model for walls with phase change materials implemented in TRNSYS

Abstract

This paper presents a model of a wall with variable properties dedicated to modelling phase change materials (PCMs) in building envelopes. The model is implemented in the TRNSYS simulation tool and referred to as Type 3258. The 1-D conduction heat transfer equation is solved using an explicit finite-difference method coupled with an enthalpy method to consider the variable PCM thermal capacity. This model includes temperature-dependent thermal conductivity and PCM-specific effects like hysteresis and supercooling. The stability conditions are discussed and the algorithm implemented in TRNSYS is described. A numerical validation performed on wall test cases proposed by the International Energy Agency is presented, showing that the developed model is in agreement with reference models. The paper also discusses the impact of temporal and spatial discretization on the model performance. Modelling problems encountered when using an effective heat capacity method (compared to an enthalpy method) and when representing supercooling are also discussed.

Keywords:

• explicit finite-difference method
• phase change material
• enthalpy method
• numerical validation
• supercooling

ORCID

Michaël Kummert http://orcid.org/0000-0003-1606-8344

Additional information

Funding

This work was supported by Fonds de Recherche du Québec Nature et Technologies [grant number 164532], Hydro-Québec [grant number 164532], and Natural Sciences and Engineering Research Council of Canada [grant number 164532].