Under-ventilation and high energy consumption are some of the problems associated with school classrooms. Thus, it is necessary to develop a ventilation strategy that is characterized by high energy-saving and ventilation efficiency. To this end, this study aims to investigate natural ventilation as a possible strategy to improve the indoor environment while reducing ventilation loads and maintaining energy costs during intermediate seasons. Ventilation and cooling load reductions based on the opening and closing of several windows were analyzed. Window flow coefficients and ventilation rates were measured and used for computational fluid dynamics (CFD) simulation to obtain pressure coefficients for 16 wind directions. The results obtained showed that the improved natural ventilation strategy could be used to effectively establish required indoor conditions (26 °C, 60% RH). Additionally, compared with the mechanical ventilation system with variable refrigerant flow, this natural strategy resulted in a decrease in energy consumption of approximately 30%. However, its application requires that internal heat gain and CO₂ emissions, which depend on human population density, as well as the room usage schedule should be considered.

The purpose of this study is to accurately evaluate the effect of vane angle on the effectiveness of air conditioning of wall-mounted split-type air conditioners. First, to determine the detailed characteristics of airflow from an air conditioner opening, airflow rate, turbulence characteristics, and air distribution were measured according to the vane angle. Then, the detailed characteristics were calculated using a simplified opening model with boundary conditions obtained from the calculated results of a cross-flow fan model using the overset mesh technique to validate the computational fluid dynamics simulation. Finally, to evaluate the effectiveness of air conditioning, the effectiveness of air change was calculated under isothermal conditions by varying the vane angle and the setting position of the air conditioner by using the validated computational fluid dynamics model. The measurement results showed that when the vane was set at the middle position (rather than at the left or right positions), the airflow rate increased by 19.0%–20.9% in the high airflow rate mode. The simulation results verified that the simplified opening model was consistent with actual findings, and only a slight difference was observed between actual measurements and the computational fluid dynamics simulation results. Furthermore, installing the air conditioner at the center of a wall and setting the vane at the middle position improved the effectiveness of indoor air conditioning.

There is a lack of scientific understanding of adding an oyster shell powder (OSP) to geopolymer concrete. The purpose of this study is: (1) to evaluate the high-temperature resistance of the alkali-activated slag ceramic powder (CP) mixture added with OSP at different temperatures, (2) to address the lack of application of environmentally friendly building materials, and (3) to reduce solid waste of OSP pollution and protect the environment. OSP replaces granulated blast furnace slag (GBFS) and CP at 10% and 20% (based on binder), respectively. The mixture was heated to 400.0, 600.0, and 800.0 °C after curing for 180 days. The results of the experiment are summarized as follows: (1) The thermogravimetric (TG) results indicated that the OSP20 samples produced more CASH gels than the control OSP0. (2) As the temperature increased, the compressive strength and ultrasonic pulse velocity (UPV) both decreased. (3) Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) results reveal that the mixture undergoes a phase transition at 800.0 °C, and compared with the control OSP0, OSP20 undergoes a different phase transition. (4) The size change and appearance image results indicate that the mixture with added OSP inhibits shrinkage, and calcium carbonate decomposes to produce off-white CaO. To sum up, adding OSP can effectively reduce the damage of high temperatures (800.0 °C) on the properties of alkali-activated binders.