Impacts of liquid phase distribution on the effective thermal conductivity of closed-cell thermal insulation

• Published in: International journal of thermal sciences Vol. 190; p. 108280
• Main Authors: Cai, Shanshan, Liu, Zifan, Li, Xu, Xu, Hongyang, Xia, Lizhi, Cremaschi, Lorenzo
• Format: Journal Article
• Language: English
• Published: Elsevier Masson SAS 01.08.2023
• Subjects: Liquid phase distribution; Multiscale simulation; Phenolic foam; Thermal conductivity; Thermal insulation; Thermal conductivity; Multiscale simulation; Thermal insulation; Liquid phase distribution; Phenolic foam
• ISSN: 1290-0729; 1778-4166
• DOI: 10.1016/j.ijthermalsci.2023.108280

This paper proposes a multiscale effective thermal conductivity model combined with liquid phase distribution to explore in detail the influence of the internal structure of closed-cell thermal insulation on the thermal behavior in the presence of moisture. By simulating the liquid phase distribution in the cracks between the insulation cell skeleton and combining it with the representative elementary volume (REV) scale and macroscopic scale thermal conductivity models, the correlations between the structural parameters, saturation, and effective thermal conductivity of phenolic thermal insulation are analyzed. A critical saturation point is proposed for the first time, and the related impact factors are discussed. For the heat and moisture transfer in porous media, the larger the critical saturation, the better the insulation performance. Based on the newly developed improved effective thermal conductivity model, nine groups of phenolic samples with different structural parameters were investigated to compare the impact of porosity, closed-open pore volume ratio, relative deviation ratio, contact angle, and closed-pore diameter on the effective thermal conductivity. Simulation results indicate that the influence of the liquid phase distribution is mainly reflected at low saturation at the REV scale; at the macroscale, the influence of the liquid phase distribution is significantly reduced. •An improved multiscale model with liquid distribution is proposed for closed-cell thermal insulation.•A new concept of critical saturation is proposed with its impact on the thermal conductivity clarified.•The impacts of structural parameters on the effective thermal conductivity are systematically analyzed.•The influence of the liquid phase distribution is different in REV scale and macroscale.