Heat transfer analysis of rotational molding process heated directly with electricity

doi:10.19491/j.issn.1001-9278.2022.07.015

Abstract

Abstract:

The temperatures at the surface of a rotational mold and inside the mold heated directly by electricity along with the consumed electric energy were measured in the heating stage. Based on the experimental data， a thermal analysis was conducted for the heating phase of the rotational molding process， and effective heat energy and ineffective heat energy were calculated. The rotational molding process was evaluated by three indexes， including the utilization rate of heat energy， the electricity consumed for heating powder per unit mass， and the time needed for heating powder per unit mass. The results indicated that the temperature distribution at the rotational mold surface is inhomogeneous， resulting in a maximum temperature difference of 8 ℃ at different locations. The highest utilization rate of heat energy was determined to be 37.5 % in three experimental cases. The utilization rate of heat energy decreased with an increase in the mass of powders inside the mold at the same heating temperature inside the mold.

Key words: rotational molding, direct electric heating, heat transfer analysis, effective heat energy, ineffective heat energy, utilization rate of heat energy

CLC Number:

TQ320.66

LIU Xuejun. Heat transfer analysis of rotational molding process heated directly with electricity[J]. China Plastics, 2022, 36(7): 109-114.

Figures/Tables 10

Fig.1. Schematic of experimental plan

Fig.2. Rotational mold heated by electricity directly

Fig.3. Cross section and dimension of hydrogen tank

名称	氢气瓶的厚度/mm	模内粉料的质量/kg	加热温度/℃
情形1	5	1.505	200
情形2	10	2.906	180
情形3	15	4.205	180

Tab.1. Three experimental cases

Fig.4. Tested temperature at the outer surface of the mold in case one

Fig.5. Tested temperature inside the mold

名称	加热时间/min	熔融时间/min	保温时间/min
情形1	16	8	4
情形2	25	17	3
情形3	56	34	13

Tab.2. Heating time， melting time and holding time in three experimental cases

Fig.6. Variation of radiation heat flux at the outer surface of the mold with time in case one

E/kJ	Q_e/kJ	Q_r/kJ	Q_c/kJ	Q_r/E	Q_c/E
6 120	2 246	191	3 683	3.1 %	60.2 %

Tab.3. E， Qe， Qr， Qc and Qr/E and Qc/E in case one

名称	E/kJ	η/%	E_p/kJ•kg^-1	τ/min•kg^-1
情形1	6 120	36.7	4 066	10.6
情形2	7 200	37.5	2 478	8.6
情形3	11 880	28.5	2 825	13.3

Tab.4. E， η， Ep and τ in three experimental cases

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