Abstract: Laying insulation materials is an effective measure to mitigate the freezing damage to channels. However, the absorption of moisture by insulation materials can lead to a deterioration in their thermal insulation performance. To investigate the impact of moisture content on thermal conductivity of insulation materials, a model predicting thermal conductivity taking moisture content into account was established using the homogenization method based on the minimum thermal resistance law. Furthermore, the influence of porosity and moisture content on thermal conductivity was examined. The proposed model was then validated against experimental results and an existing model. The findings reveal that thermal conductivity decreases with the increase of porosity, but increases with the increase of moisture content. The error between the predicted and measured results is less than 5%, thereby confirming the feasibility of the proposed model in calculating the thermal conductivity of insulation materials. Additionally, moisture is identified as a significant factor in diminishing the thermal insulation performance of polyurethane rigid foam. Consequently, enhancing the hydrophobic properties of insulation materials holds great practical significance in improving its thermal insulation performance. Several suggestions are put forward to enhance the hydrophobicity of polyurethane insulation materials.

Key words: canal, insulation material, thermal conductivity, polyurethane, prediction model