Iranian Journal of Chemical Engineering (IJChE)

Abstract This study investigates the thermal performance optimization of double-glazed window systems in Tehran climate conditions with the aim of minimizing building energy consumption. Four key design parameters were considered, including glass thickness (2, 4, 6, and 8 mm), glass type (ordinary, reflective, spectrally-selective, and blue-tinted glass), air-gap thickness between glazing layers (3, 6, 8, and 13 mm), and the type of filling gas (air, argon, krypton, and xenon). The modeling and optimization process was carried out using Response Surface Methodology (RSM) in Design-Expert software. The results demonstrated that increasing the air-gap thickness between the glazing layers significantly reduced the building energy consumption. Similarly, increasing the glass thickness improved the thermal insulation performance and decreased energy usage. Among the investigated gases, xenon exhibited the best thermal performance and resulted in the lowest energy consumption. In addition, reflective glass showed superior performance compared with the other glass types in terms of reducing energy demand. The optimization results indicated that the optimum configuration for achieving minimum energy consumption consists of reflective glass, xenon gas filling, an air-gap thickness of 12.75 mm, and a glass thickness of 2.825 mm. Under these optimal conditions, the minimum building energy consumption was obtained as 161.46 kWh/m². The findings of this study provide useful insights for the design and optimization of energy-efficient double-glazed window systems in a high-rise office building located in climates similar to Tehran.

Abstract Given the high share of energy consumption in the building sector and the need to enhance thermal performance in cold climates, this study investigates the effect of the paraffin-based phase change material RT22HC on improving the thermal efficiency of a double-skin building facade. This material has a melting temperature in the range of 20–23°C (peak 22°C) and a latent heat storage capacity of about 190 kJ/kg, which enables storing and releasing heat at an approximately constant temperature. The aim of the study is to analyze the impact of removing thermal insulation and replacing it with an air cavity containing PCM on heating and cooling loads during cold periods in the city of Tabriz. Energy modeling was performed using DB software, and the heat transfer analysis was conducted with the Finite Difference algorithm. Three scenarios were examined: a base facade; a double-skin facade with PCM and thermal insulation; and a double-skin facade with PCM and an air cavity. The results showed that in the third case, the melting and solidification mechanism of RT22HC reduced heat flux and increased temperature stability; such that the annual sensible heat load decreased from 27276.61 kWh to 9985.8 kWh (equivalent to 63%). Moreover, indoor temperature fluctuations and mean radiant temperature differences decreased, improving thermal comfort conditions. Overall, the low thermal conductivity (0.2 W/m·K) and high heat capacity of PCM led to proposing this material as an effective substitute for conventional thermal insulations in DSF facades in cold climates.