Experimental investigation of frosting characteristics on cold surfaces vibrating at various frequencies

Frost formation on equipment surfaces restricts the efficient use of energy in refrigeration and air conditioning. However, the frosting features on common cold vibrating surfaces are not fully known. This study sets up an experiment platform and conducts frosting experiments on cold vibrating surfaces to investigate the impact of vibration frequencies on droplet solidification and frost layer growth characteristics. The results show that as the vibration frequency increases, the starting time for droplet solidification generally increases while the freezing wave propagation rate first increases and then decreases. Compared to the stationary condition, the average freezing wave propagation rate at 50 Hz increases by 6.00 μm²/s while it only increases by 0.73 μm²/s at 100 Hz. This non-monotonic changing trend of freezing wave propagation rate with the increase of vibration frequency is caused by the combined effect of vibration-enhanced coalescence of condensate droplets and heat and mass transfer during the evaporation of frozen droplets. Besides, with the increase of vibration frequency, both the frost layer height and growth rate first increase and then decrease while the average frost layer surface roughness basically decreases. The highest and lowest frost layer growth rates of 0.62 and 0.37 μm/s appear at 25 and 100 Hz. These are the competitive results of enhanced heat and mass water vapor, increasing surface temperature, and enlarged inertial force for the growth, meltback, and collapse of the frost layer. The findings contribute to optimizing the accuracy of frost prediction and provide a reference for anti-frosting and de-frosting applications in various fields.