3.2.1. The Thermal Environment Analysis

Figure 7 shows the thermal energy transfer for the cabin. External heat enters the cabin through three ways including heat conduction, heat convection and thermal radiation. When the vehicle is parked under the sunlight for a soaking period, some solar radiation enters the passenger compartment passing through the windows, some is reflected by the solid envelope, the rest is absorbed. Solar radiation leads to a considerable thermal load through heating the envelope and interiors. In addition, the cabin exchanges the heat with the external environment through the coupled convection and radiation. Due to the uniform temperature distribution, the airflow cycles are driven by buoyant force, creating the natural convection in the cabin. The scorching air is trapped inside the cabin due to the lack of openings, resulting in the greenhouse effect [56]. In this study, the simulation was based on the city of Hangzhou (118◦21 –120◦30 E, 29◦11 –30◦33 N), the capital of Zhejiang Province located along Southeast coast of China, characterized by long and hot summers. The ambient conditions were chosen on June 21 (summer solstice). The windshield orientation was to the south.

**Figure 7.** Heat transfer between the surface and its surroundings in the cabin.
