The effect of different pre-treatments on the rate of changes in the thermal properties of rosemary leaves

This study examines the rosemary thermal properties, including thermal conductivity, specific heat capacity, and thermal diffusion coefficient in the microwave, blanching, and oven pretreatments. To test the microwave pretreatment for three-time levels of ۶۰, ۹۰, and ۱۲۰ seconds, the samples were placed in the microwave, and their weight changes were recorded. The samples were pre-treated for blanching pretreatment at three-time levels of ۱۸۰, ۳۶۰, and ۵۴۰ seconds. Finally, in the oven treatment, the rosemary leaf samples were placed at three temperature levels of ۳۰, ۴۵, and ۶۰ °C for ۱۵ minutes. Then, in three voltages of ۴, ۷, and ۱۰ volts, the thermal properties were obtained separately for each of the pretreatments, and for all cases, a control treatment was considered. The results were analyzed using a completely randomized design and a factorial experiment. According to the results obtained for microwave and blanching pretreatment, increasing the pretreatment time and pretreatment of the oven with decreasing pretreatment temperature resulted in a decreasing trend for thermal conductivity coefficient, exceptional heat capacity, and thermal diffusion coefficient. The increase in voltage also occurred in the thermal properties of the rosemary leaf of all three pretreatments. The pretreatment levels were significantly higher than the process voltage for the thermal conductivity and diffusion coefficient, which indicates that pretreatment has a more significant impact on the thermal properties of the process. The maximum value of the electrical conductivity coefficient is ۰.۴۲۵۶, ۰.۵۸۵۱, and ۰.۵۱۰ Wm-۱ ° C-۱, and for the specific heat capacity of ۲.۵۸, ۲.۶۸, and ۲.۶۵ kJ kg-۱ ° C-۱, and also for the thermal diffusion coefficient of ۲.۴۸×۶-۱۰, ۲.۸۱× ۶-۱۰and ۲.۵۰×۶.-۱۰ m۲s-۱ for microwave, blanching, and oven pretreatments, respectively. Among the three pretreatments, microwave pretreatment significantly reduced the thermal conductivity, specific heat capacity, and thermal diffusion coefficient of rosemary leaves.

کلیدواژه ها:

Thermal conductivity ، specific heat ، thermal diffusion ، Microwave