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| Mechanism of ultrasound-enhanced near-critical CO2 fluid extraction |
1. College of Food Engineering, Xuzhou Institute of Technology, Xuzhou, Jiangsu 221008, China; 2. College of Light Industry and Food Sciences, South China University of Technology, Guangzhou, Guangdong 510640, China）
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Abstract The theory of cavitation threshold of ultrasonic in near-critical CO2 fluid with original radius of cavitation bubble was firstly discussed by the basic calculation of cavitation threshold of ultrasonic in near-critical CO2 fluid. Then the theory was applied in judging the occurrence of cavitation in near-critical CO2 fluid. Thus, the mechanism of ultrasound-enhanced near-critical CO2 fluid extraction （UCCFE） was disclosed. The results show that cavitation threshold of ultrasonic increases with the rise of original radius of cavitation bubble in near-critical CO2 fluid, that is, under the condition that other factors are the same, the larger original radius of cavitation bubble is, the more cavitation appears in near-critical CO2 fluid. When temperature was 20 ℃ and pressure was 5.82 MPa, the cavitation existed in near-critical CO2 fluid, so the mechanism of UCCFE included cavitation effect and mechanical effect. When temperature was 20 ℃ and pressure was 8 MPa, the cavitation did not exist in near-critical CO2 fluid, so the mechanism of UCCFE only included mechanical effect.
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2009, Vol. 30 
