Abstract
Recent primary concern for the design of high performance heat exchanger and highly integrated electronic equipments is to develop an active and creative technologies which enhance the heat transfer without obstructing the coolant flows. In this study, we found through the LDV measurement that the gaseous cavitation induced by ultrasonic vibration applied to the CO2 saturated water in the square cross-sectioned straight duct flow enhances the turbulence much more than the case of non-ultrasonic or normal ultrasonic conditions without gaseous cavitation does. We also found that gaseous cavitation can enhance effectively the turbulent heat transfer between the heating surfaces and coolants by destructing the viscous sublayer.
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Abbreviations
- c :
-
Specific heat
- D h :
-
Hydraulic diameter
- D ij :
-
Viscous diffusion rate of Reynolds stresses
- f :
-
Ultrasonic wave frequency
- k :
-
Boltzmann constant
- \(\dot m\) :
-
Mass flow rate
- Pa :
-
Ambient pressure
- P 0 :
-
Hydraulic pressure
- P ij :
-
Shear generation rate of Reynolds stress
- P v :
-
Vapor pressure of liquid
- r :
-
Distance from bubble center
- R :
-
Bubble radius
- R 0 :
-
Critical bubble radius
- Re :
-
Reynolds number
- T :
-
Temperature
- Ui :
-
Velocity components
- Ub :
-
Streamwise bulk velocity
- u :
-
Streamwise turbulent velocity
- \(\sqrt {u^2 } \) :
-
Streamwise RMS (root mean square) value of turbulent velocity
- \(\overline {u_i u_j } \) :
-
Reynolds stress components
- v :
-
Normal turbulent velocity
- \(\sqrt {v^2 } \) :
-
Normal RMS (root mean square) value of turbulent velocity
- V :
-
Volume
- Vf :
-
Radial velocity at a distance ofr
- Vg :
-
Radial velocity at a bubble surface
- \(\dot W\) :
-
Ultrasonic energy emission rate
- x i :
-
Coordinate components
- γ:
-
Ratio of specific heats of the gas in bubble
- σ:
-
Surface tension of liquid
- φ ij :
-
Pressure diffusion rate of Reynolds stress
- δ 0 :
-
Local amplitude of ultrasonic vibration
- ε ij :
-
Dissipation rate of Reynolds stresses
- λ:
-
Wave length
- ρ:
-
Density of liquid
References
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Lee, S.Y., Choi, Y.D. Turbulence enhancement by ultrasonically induced gaseous cavitation in the CO2 saturated water. KSME International Journal 16, 246–254 (2002). https://doi.org/10.1007/BF03185176
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DOI: https://doi.org/10.1007/BF03185176