As it Embelin can be observed, heat flowrates estimated at both cold and hot sides of the heat exchanger (qc_us and qh_us respectively) are higher in the presence of ultrasound than those obtained under silent conditions (qc and qh respectively). A generic graph can be useful to illustrate the enhancement of heat flowrates by ultrasound as shown in Fig. 4.
Fig. 4. Energy balance in a generic chart bar form: illustration of heat transfer intensification with ultrasound.Figure optionsDownload full-size imageDownload as PowerPoint slide
As previously discussed and as shown by the bar chart diagram in Fig. 4, budding was demonstrated that heat transfer enhancement is not attributed only to ultrasonic power supplied to the heat exchanger and dissipated at the cold side but also to ultrasonically- induced effects resulting in heat transfer intensification . Enhancement of heat transfer by means of ultrasound can also be expressed by comparison of the overall heat transfer coefficients with and without ultrasound defining an enhancement factor EF as the ratio Uus/U . Experimental corresponding data are detailed in Table 2.