Effects of Moisture Migration in Insulations under Hot and Humid Conditions

Abstract

The effects of moisture gain by fibre glass insulation slabs were investigated experimentally by exposing one face of the slabs to a hot and humid ambient while maintaining the other face at a constant cold temperature. The temperature ranges considered for the hot and cold sides of the slabs were 36°C to 41°C and 8.5°C to 20.8°C, respectively. The slab thicknesses ranged from 62 to 76 mm. The variation of the heat flux at the cold surface, the temperature distribution, the total moisture gain and the liquid content distribution were measured over a period of up to 600 hours. One-dimensional transport models with liquid content dependent physical properties were used to interpret the experimental data. The heat flux at the cold face increased gradually with time while the temperature distribution across the slabs showed a maximum fluctuation of about 2°C. The rate of total moisture gain was nearly constant initially, but decreased gradually with time. The measured liquid content distribution across the slabs was highly nonuniform. The computational model predicted the heat flux and the temperature distribution well but overestimated the total moisture gain at longer times. The model predicted a more uniform liquid distribution than that measured experimentally.