Energy Systems Laboratory (http://esl.eslwin.tamu.edu)
Abstract
In hot, humid climates, the internal surfaces of windows in air-conditioned buildings are in contact with relatively colder air. Meanwhile, the external surfaces are exposed to hot humid atmospheric air. This hygro-thermal condition may cause frequent atmospheric condensation on external surfaces of windows when their surface temperature drops below the dew point temperature of the hot humid air. To date, external surface condensation on windows has been given relatively much less importance than their internal surface condensation. In addition, the thermal analysis of windows in hot humid climates has always been performed in the absence of condensation. Under moderate air temperature and humidity conditions, such practice is acceplable. However, when windows experience atmospheric condensation on their external surfaces, the effect of condensation on window energy loss needs to be examined. In this paper, the external condensation process is analyzed and the atmospheric water vapor mass condensation rate has been obtained by utilizing a simplified transient uni-dimensional finite difference model. The results show that this model has enhanced the assessment of the potential for atmospheric condensation on windows in hot, humid climates and in predicting the amount of condensation expected, as well as the associated energy loss for given thermal and moisture conditions. The numerical computation of the model is able to account for condensation and its impact on the temperature gradient across the window. Thermal analysis of both single and insulated double-glazed windows under condensation conditions is presented. The work also includes the computational procedure used and the results or a case study demonstrating the model's capabilities
