Study On The Mechanism Of Liquid Viscosity Changes Due To The Effect Of The Electromagnetic Field

Viscosity is an important physical parameter of liquid, and it should be taken into account in many engineering designs and calculations, especially in chemical engineering. Viscosity represents the internal friction among molecules, which is determined by the interactions between molecules and temperature mainly, and is also related to the structures, locations and movements of molecules in liquid. Because of the complexities of liquid molecular structures and interactions, there is no theoretical method which can accurately calculate liquid viscosity value so far. So the studies of viscosity mainly focused on experimental measurements, and establishment of some empirical or semi-empirical formulas based on the measurements. In most cases, those empirical formulas contain some adjustable parameters. Although experimental measurements can provide viscosity values, it is still difficult to obtain the accurate viscosity values at any temperature because of the complexities of measurement and the restrictions of operational conditions. Therefore, how to calculate viscosity value theoretically has been more concerned, theoretical calculation can not only provide supplements for the lack of experiment, but also help us to understand the mechanism of liquid viscosity. In addition, the theoretical study can also play an important guidance role in experimental operations and process designs.Eyring viscosity equation is a popular viscosity theory. Based on the Eyring's absolute reaction rate equation and Boltzmann statistics theory, and including the probabilities of creating a hole in liquid and the transmitting to the neighboring hole, a modified Eyring viscosity equation was proposed. According to the structural characteristics of short-range order, liquid is considered as quasi-lattice structure in a small region. The activation energy was analytical calculated from Lennard–Jones potential function and Stockmayer potential function between two liquid molecules, which is the minimum energy needed for the molecule to transmit to a neighboring hole, because of the restraint of other molecules around it. The viscosity values of 37 kinds of typical liquid in 25 Celsius and the changes in viscosity of three kinds of liquid with temperature were calculated with this modified viscosity equation, and the calculated results agree with the experimental values in some extent.Viscosity of liquid may be changed duo to the effects of the external field. Based on the modified Eyring viscosity equation and liquid quasi-lattice model, it is known that the liquid viscosity depends on the activation energy of liquid. According to the effects of electrostatic field and magneto static field, the work may be done on the molecules of liquid due to the field force acted on the target molecule. Because of the work, the activation energy of liquid is changed, and there are some changes for the viscosity of liquid. As the directions of electrostatic field and magneto static field are parallel to the direction of flow, the changes of liquid viscosity is related to the gradient of the field strength. As the directions of electrostatic field and magneto static field are perpendicular to the direction of liquid flow, liquid flows no longer orderly and turbulence induced immediately. Due to the result, the flow resistance increases and the viscosity of liquid become larger. The loss is induced in liquid based on the effect of alternating electric field and magnetic field. Because of the loss, the internal energy of liquid increases and the activation energy decreases slightly, and the viscosity of liquid reduced a little. This theory can explain the contradictory phenomena in experiments about viscosity changes of liquid due to the effect of electromagnetic field and play an important guidance for production practices.By comparing with the traditional extraction method, Microwave Assisted Extraction has many advantages, such as high extraction rate, time saving, low power consumption and so on. In the process of extraction, increasing the diffusion coefficient of the target molecule is the key to improve the extraction rate. Based on the effect of microwave field, the polarization loss of solvent molecules is produced, and the viscosity of solvent is reduced. According to Fick's law of diffusion and Stokes-Einstein equation, target molecular diffusion coefficient is inversely proportional to the viscosity of solvent. Therefore, the diffusion coefficient in the process of Microwave Assisted Extraction is greater than traditional extraction method. Based on the principle of viscosity reducing, the diffusion enhancement factor has been calculated, the calculated values agree with the experimental data well. The relationship between diffusion coefficient, nature of solvent molecule and microwave parameter is established in this work, and the work provides a theoretical guidance for improving the extraction rate.