Evaluation of heat transfer in humidification phenomena – Comparison between infrared thermography and numerical simulation

Abstract

Infrared thermography (IRT) is a non-destructive testing technology used to assess the performance of buildings. As a diagnosis tool for retrofit and conservation of buildings it helps understanding the anomalies by allowing “seeing” their causes in a non-invasive manner. However, in most cases, the interpretation of the results (thermal images) is mainly qualitative, restraining and, eventually, pointing to incorrect conclusions. Using numerical tools that contribute to the quantitative interpretation of IRT applications is therefore a step forward in this field. The main objective of this work is the evaluation of heat transfer in humidification phenomena by comparing the results of 2D hygrothermal simulation with thermal images. Thermal images were taken to a lightweight concrete specimen during a 24-hours partial immersion period. The humidification of the specimen was simulated using WUFI 2D. The best way to deal with the liquid water level in contact with the bottom of the specimen was deeply analysed. The comparison of the simulation with the results of IRT showed that the program tends to overestimate the phenomena of heat transfer (water rise and evaporation on the surface), as the water level reached in the simulation was consistently higher than the one obtained in the thermal images.