## 3 Results and Discussion
### Passive Cooling of the New System and Base Case  
#### 3.2.1 Comparison of Passive Cooling of the New System with That of the Base Case  
After setting up the new system for the case study, the situation without considering WHR is analyzed in detail. Figure 12 shows the passive cooling process of the base case and that of the new system without the WHR. At 4 min, the base case uses the pati entrance as the main air inlet of the building to transport airflow into the building. In contrast, in the new system, there are two air inlets for the building: the patio entrance and the opening connected to the cold alley. The air temperature at the entrance of the patio was 34 \({}^{\circ}\)C, and the air temperature in the cold alley was 28 \({}^{\circ}\)C. When the time reached 50 min, it can be seen that in the basic case, the outdoor air entered the building through the courtyard, which initially reduced the courtyard temperature. When the courtyard temperature stabilized, it exchanged heat with each room through the doors and windows. By contrast, at the same time of 50 min, when the passive cooling was conducted based on the cold alley ventilation,  
Figure 11: Comparative analysis with and without the air insulation wall.  
the cold air in the cold alley avoided the pati and directly introduced cold air into the room, significantly improving the cooling efficiency. Moreover, the second-floor rooms on both sides of the pati are connected by air ducts; therefore, when the temperature of the second-floor room on the side of the cold alley reached the thermal equilibrium point, part of the cold air passed through the stairwell to reach the first floor, and another part of the cold air passed through the air duct entering the opposite room. The air wall surrounding the outside of the building also introduced cold air from the cold alley into the room on the other side; thus, the interactive cooling method can also increase the cooling rate of the room far away from the cold alley. In the ideal state without WHR, all rooms in the base case reached the thermal equilibrium temperature after 6 h. Because the courtyard is used to cool the room, the courtyard temperature is equal to the indoor temperature. The building mainly relies on the normal outdoor temperature for cooling, and the temperature drops by approximately 1 \({}^{\circ}\)C. The final room thermal equilibrium temperature was 34 \({}^{\circ}\)C, and the cooling rate was 0.166 \({}^{\circ}\)C/h. In contrast, when using the new system for passive cooling, the utilization rate of the cold air was improved, as the heat exchange with the courtyard air was avoided. The entire room reached the thermal equilibrium temperature after 1.66 h. The courtyard and indoor temperatures were quite different. The temperature of the courtyard was 32 \({}^{\circ}\)C. The indoor temperature was 28 \({}^{\circ}\)C, and the indoor cooling rate was 3.61 \({}^{\circ}\)C/h. However, the temperature of the room near the entrance of the pati was affected by the normal outdoor temperature, and thus, its temperature was higher than that of other rooms, at approximately 33 \({}^{\circ}\)C.  
Figure 12: _Cont._