Results and discussions
The symmetrical distribution of ultrasonic pressure and acoustic intensity inside the melt is illustrated in Fig. 4. Positive and negative pressure appears alternately in the field, due to the fountain effect, the pressure near the center is apparently higher than that near the two sides. In Fig. 4(a), there is a zero-pressure region at half height of the field, while the amplitude of sonic pressure above and under it dihydrofolate reductase is a non-zero value, as a result, two vortices appear in the upper part and lower part of the flow field, respectively, as shown in Fig. 5(a). The acoustic intensity distributes in a similar way with the sonic pressure, there is a large area where the acoustic intensity is nearly zero, it reaches the lowest value at zero-pressure region.
The temperature distribution in the melting procedure with and without ultrasonic processing is shown in Fig. 5, from which it can be seen that ultrasonic processing makes the temperature distribution more uniform. The temperature gradient in Fig. 5(a) is obviously smaller than that in Fig. 5(b), the area of large temperature gradient region near the wall in Fig. 5(a) is smaller than that in Fig. 3(b) as well. When processed with ultrasound, two low-temperature peaks appear near the booster due to the symmetrical vortices induced by ultrasonic streaming, the motion of fluid in that region is restricted, its temperature becomes lower than that of other regions at the same height. The flow in the melt is just natural convection without ultrasound introduction, as a result, there is only one low-temperature peak, whose location is the farthest from the heating surface. As shown in Fig. 5, when processed with ultrasound, the temperature of the melt at the bottom of the field is slightly lower than that without ultrasonic treatment. In Fig. 5(a), the motion area of the fluid is restricted by the symmetrical vortices at the lower part, which prevent the effective heat transfer between the bottom and other regions. However, in the melt without ultrasonic processing, the heat transfer between the bottom and other regions is much better as the fluid is not restricted at the bottom but driven to the whole field by natural convection.
Fig. 6(a) illustrates the temperature in the melt with and without ultrasonic processing at the location of 1/2 height. It can be seen that the melt temperature at the same location is apparently higher under ultrasonic treatment, moreover, the melt temperature rises with the increase of ultrasonic power. Fig. 6(b) shows the temperature distribution along the vertical direction (x=0, −0.015m
Results and discussions