Operating mechanism of pulsating heat pipe with different wettability from the perspective of thermo-hydrodynamic characteristics of vapor–liquid interface region

Abstract

Pulsating heat pipe (PHP) is considered to be one of the most promising efficient heat sinks in electronic thermal management for good cooling capacity and compact structure. Understanding the complex operating mechanism of PHP from various angles is crucial for advancing its large-scale application. Among various factors, the thermo-hydrodynamic characteristics of the vapor–liquid interface region have a critical impact on the operation of PHP. Based on this, the transient numerical simulations were conducted in this work on PHPs with 20° and 150° contact angles (hydrophilic and hydrophobic, respectively), and the influence of different thermo-hydrodynamic characteristics of the vapor–liquid interface region on the operating mechanism of PHPs was analyzed. The results found that the presence of a widely spreading liquid film at the interface of hydrophilic PHP significantly changed its thermo-hydrodynamic characteristics compared to hydrophobic PHP. As a consequence, the hydrophilic PHP and hydrophobic PHP presented better heat transfer performance in the evaporation section and condensation section, respectively. Under low heat inputs, with regular vapor–liquid distribution in the interface region, the hydrophobic PHP presented better startup and heat transfer performance due to better hydrodynamic behavior caused by more easily formed pressure gradients. Under high heat inputs, the hydrophilic PHP showed significantly better heat transfer performance due to the intense evaporation and continuous spreading of new liquid film in the interface region, which also played a key role in stronger anti-dry-out performance.

Keywords:

• Heat transfer
• operating mechanism
• pulsating heat pipe
• vapor–liquid interface
• wettability

Disclosure statement

The authors report there are no competing interests to declare.

Additional information

Funding

This work has been supported by the National Natural Science Foundation of China (No. 52076185), the Natural Science Foundation of Zhejiang Province (No. LZ19E060001) and the Open Project of Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering (No. KF2019-02).