Abstract: In response to a steel outdoor protective enclosure for certain outdoor equipment, referencing the national military industry standard, a “fiberglass+polyurethane+fiberglass” composite sandwich structure enclosure is designed. This design takes into account the variations in ambient temperature and solar radiation over time, as well as the influence of natural convection due to wind speed on heat dissipation. Based on existing experimental data, the effectiveness of the transient analysis method is validated. Subsequently, a transient thermal analysis is conducted on the outdoor enclosure, followed by optimizing the enclosure’s wall thickness. Ultimately, compared to a metal enclosure, the maximum internal air temperature inside the composite enclosure is reduced from 78 ℃ to 45 ℃, resulting in a reduction of 41.6%. This reduction meets the thermal insulation design requirement of keeping the internal air temperature below 50 ℃. Additionally, a weight reduction of 10.6% is achieved.

Key words: steady-state heat, transient heat, glass fiber, thermal insulation performance, composites