Abstract:

First， temperatures at mold surface and inside mold， and heating time and consumed electricity were measured by means of experiments for electric⁃heating empty mold and rotational molding process to make liner of hydrogen cylinder with four different thicknesses， and the heating efficiency and magnification factor were calculated in the five cases based on these measurements. Then， a computational method for the design of electric⁃heating rotational molding process was proposed. After the material and mass of mold， physical properties and mass of the powders inside the mold， and process parameters were defined， the effective thermal energy was calculated at first， and then the thermal energy from heating wire required in heating phase was estimated according to the magnification factor. As a result， the full load heating power and length of heating wire were obtained. The model of static bed was applied to simulate the heating time and thermal energy actually required from heating wire with the aid of the FLUENT software. The application steps of the method were illustrated through an electric⁃heating rotational molding process to make a hollow plastic cube. The influence of the full load heating power and mold material on the heating efficiency and the heating time and thermal energy actually required from heating wire was investigated. The results indicated that the heating efficiency decreased with an increase in the thickness of the liner of hydrogen cylinders. The heating time decreased slowly with an increase in the full load power. In the application of the steel mold， the heating time became longer， and more thermal energy from heating wire was required compared to the application of an aluminum mold.

Key words: electric?heating mold, rotational molding process, heating efficiency, heating time, heating power, heat transfer computation