Session: 11-09-02: Phase-Change Processes: Fundamentals and Applications

Paper Number: 144775

144775 - Enhancement of Pool Boiling Heat Transfer Through Induced Vibrations- a Cascaded Lattice Boltzmann Study 

A numerical study on enhancement of pool boiling heat transfer by vertical heater vibration is conducted using cascaded lattice Boltzmann method (CLBM), where the collision of particles takes place in the central moment space with respect to the bulk fluid velocity. The lower-order moment information is then cascaded to execute the higher-order moment of the particle distribution function. The fluid chosen for the study is water at a bulk temperature of 0.86 times the critical temperature and bulk pressure at 0.306 times the critical pressure. A wide range of frequencies from 0-1000Hz was chosen for the study. While the amplitude was varied from 0 to 3mm. The effect of variation of frequency, amplitude, and vibrational Reynold’s number () on the bubble dynamics and pool boiling heat transfer performance was studied. At a constant amplitude, it was observed that for a lower frequency range (f<100Hz), there exists an optimum frequency for which the non-dimensional surface superheat or the Jacob number (Ja) is the lowest for a given space-time-averaged heat flux (q”) and the Nusselt number (Nu) are the highest when compared to baseline scenario (non-vibrating heater). For the higher frequency range (f≥100Hz), the trend is monotonous where Ja decreases or, q” and Nu increases with increase in the frequency, at a constant amplitude. The effect of amplitude variation on boiling heat transfer performance at a given frequency, also differed for different frequency ranges. For the lower frequency range, Nusselt number decreased with an increase in amplitude, while for the higher frequency range, Nu increased with an increase in amplitude. The heater surface temperature increased with an increase in amplitude for a constant lower frequency, while it decreased with an increase in amplitude for a constant higher frequency. A maximum of 20.5% increment in q” or a 20% reduction in Ja compared to a non-vibrating heater were observed. A closer look at the effect of vibration on the bubble dynamics revealed that vibration, in general, leads to faster bubble nucleation and enhanced bubble departure frequency, though the level of impact depends on the combination of amplitude and frequency. The bubble dynamics could be correlated to the trends observed in Ja and q”. A high amplitude and higher frequency promoted the continuous formation of vapour film, leading to transition to film boiling. In contrast, there was no continuous vapour film formation for low-amplitude and high-frequency combinations.

Presenting Author: Sonali Priyadarshini Das IIT Kharagpur

Presenting Author Biography: Sonali Priyadarshini Das is a Ph.D. student in the department of Mechanical Engineering at IIT Kharagpur, India, where she joined in 2020. Her Ph.D. research involves numerical and experimental investigation of enhancement techniques in pool boiling heat transfer. Prior to joining IIT Kharagpur, Sonali completed her Masters from NIT, Silchar, India.

Authors:

Sonali Priyadarshini Das IIT Kharagpur
Anandaroop Bhattacharya IIT Kharagpur