Energy and exergy analysis of an experimental ventilated façade

Abstract

This work, analyzes ventilated façades through the first and second law of thermodynamics. In addition to the energy-balances, it presents the exergy-balances on the interior and exterior surface of a façade, taking into account the different mechanisms of heat exchange. It proposes two new indexes (EQC and ExQC) to characterize the behavior of ventilated façades, by comparing their behavior with a reference façade and considering the energy balance in one case and the exergy balance in the other. An experimental test of a forced ventilated façade serves as the case study, using the test-methodology based on Paslink cells. The test data serve to characterize the behavior of the façade, both from an energy and exergy point of view. Overall, 53.05 kWh of heat is lost to the outside through the façade during 6 days of November, which corresponds to 0.31 kWh of exergy-loss. The internal energy change of the façade is decomposed according to its layers, showing that in terms of energy the sandwich insulation layer influences the most (99.45 % of the total change) but in terms of exergy, on the contrary, the metal sheet affects the most (83.66 %). The values obtained for the two indexes show that, under the test conditions, although the ventilated façade and the reference façade present similar values from the energy point of view, when the exergy is used, it is clearly seen that the behavior of the ventilated façade is 44 % better.