目的 研究传热过程中不同结构尺寸EPP保温箱的保温性能，以及EPP保温箱内相变材料的相变过程及融化时间。方法 运用有限元软件构建EPP保温箱热传导模型和相变材料的相变传热模型，将相变材料完全融化所经历的时间作为有效保温时间，并以有效保温时间的长短评价保温箱的保温性能。结果 传热过程中，在保温箱内容积、箱体厚度和箱盖厚度均相同的条件下，内外表面积几何平均值越小，保温时间越长，且长宽比值在1.8～2.0之间时，内外表面积的几何平均值最小。结论 进行保温箱结构设计时，适当控制长宽比可减小内外表面积的几何平均值，从而有效提高保温箱的保温能力。

The work aims to study the thermal insulation performance of EPP insulating box with different structure sizes in the process of heat transfer, and the phase change process and melting time of the phase change material in the EPP insulating box. The finite element software was used to construct the heat transfer model of EPP insulating box and the phase change heat transfer model of phase change materials. The time in which the phase change material was completely melted was taken as the effective holding time, and the length of the effective holding time was used to evaluate the insulation performance of the insulating box. In the heat transfer process, when the inner volume, insulating box thickness and lid thickness were the same, the smaller the geometric mean of the internal and external surface areas, the longer the holding time. When the length-width ratio was between 1.8 and 2.0, the geometric mean of internal and external surface areas was the smallest. In the process of structure design of insulating box, the appropriately controlled length-width ratio can reduce the geometric mean of the internal and external surface areas, thus effectively improving the insulation performance of the insulating box.