Experimental investigation of the ultrasonic wave effects on the viscosity and thermal behaviour of an asphaltenic crude oil

In this study, the influence of ultrasonic waves on the viscosity and thermal behaviour of a crude oil with high asphaltene content at different irradiation times and powers/frequencies was investigated. It was found that the ultrasonic radiation significantly reduced the oil viscosity before the oil cooled down. The viscosity was then remeasured after the irradiated oil cooled down to the ambient temperature to evaluate the reversibility in viscosity at various time intervals. For each ultrasonic frequency, an optimum irradiation time was found at which the cooled-down irradiated oil reached a minimum viscosity. For the ultrasonic radiation with a frequency of 46 kHz and an output power of 50 W, it was found that the permanent viscosity loss of the cooled-down oil irradiated for an optimum time of 8 min was 10 %. The effects of ultrasonic irradiation on thermal behaviour of the oil were analysed using thermogravimetric and differential thermal (TGA/DTA) methods to evaluate the relation between changes in viscosity and thermal properties of the oil. It was found that the weight loss of the irradiated-oil was more than that of the non-irradiated oil at the end of both the pyrolysis and oxidation stages.