Acoustically enhanced heat transport.

Area of Science:

• Heat Transfer
• Fluid Dynamics
• Acoustics

Background:

• Nucleate boiling is a critical heat transfer regime.
• Enhancing heat transfer efficiency is crucial for many industrial applications.
• Acoustic wave excitation offers a novel approach to manipulate boiling phenomena.

Purpose of the Study:

• To investigate the effect of high-frequency acoustic waves on heat transfer during nucleate boiling.
• To explore the mechanisms responsible for heat transfer enhancement under acoustic excitation.
• To quantify the improvements in heat transfer and surface temperature reduction.

Main Methods:

• Experiments were conducted using liquid droplets (deionized water) on a heated, vibrating substrate.
• High-frequency acoustic waves (f ~ 10^6 Hz) were induced on the heated surface.
• Vibration amplitudes were varied (ξs ~ 10^-9 m to 10^-8 m) to observe their impact on heat transfer.

Main Results:

• Improved heat transfer was observed at lower vibration amplitudes due to vapor bubble detachment and thermal mixing.
• At higher amplitudes (ξs ~ 10^-8 m), heat transfer enhancement increased due to rapid vapor bubble bursting at the liquid-air interface.
• Further increases in amplitude led to atomization, further boosting heat transfer.
• Acoustic wave displacement amplitude of ~10^-8 m and frequencies of ~10^6 Hz reduced surface temperature by up to 50%.

Conclusions:

• High-frequency acoustic waves are effective in enhancing heat transfer in the nucleate boiling regime.
• The enhancement mechanisms involve bubble dynamics, thermal mixing, and atomization.
• Acoustic excitation presents a promising method for efficient thermal management, achieving significant surface temperature reductions.