Dropwise condensation of low surface tension fluids on lubricant-infused surfaces: Droplet size distribution and heat transfer

AbstractThis paper presents experimental results on rapid freezing of water droplets injected into a low temperature environment. A heat balance method was applied to determine the ratio of the water droplets frozen at the collection after the airborne time. The experimental results show that rapid freezing of water droplets could be achieved within three seconds of airborne time. Droplet size distribution of the frozen water droplets after collection was estimated. Heat transfer during the airborne time was calculated with consideration of the droplet size distribution. At attempt was taken to compare the heat transfer obtained with some previous studies on heat transfer of spherical objects in air. The research results show that droplet size distribution is important for the prediction of heat transfer of water droplets traveling in air. The results presented in this study contribute to the understanding of heat transfer of water droplets injected into a low temperature air.

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Condensate droplet size distribution and heat transfer on hierarchical slippery lubricant infused porous surfaces

Applied Thermal Engineering ◽

10.1016/j.applthermaleng.2020.115386 ◽

2020 ◽

Vol 176 ◽

pp. 115386 ◽

Cited By ~ 3

Author(s):

Yota Maeda ◽

Fengyong Lv ◽

Peng Zhang ◽

Yasuyuki Takata ◽

Daniel Orejon

Keyword(s):

Heat Transfer ◽

Size Distribution ◽

Droplet Size ◽

Droplet Size Distribution ◽

Porous Surfaces ◽

Condensate Droplet

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Time Evolution of the Droplet Size Distribution in Dropwise Condensation

Journal of Heat Transfer ◽

10.1115/1.4047488 ◽

2020 ◽

Author(s):

Maofei Mei ◽

Feng Hu ◽

Chong Han ◽

Yan Sun ◽

Dongdong Liu

Keyword(s):

Size Distribution ◽

Droplet Size ◽

Power Law ◽

Droplet Size Distribution ◽

Droplet Growth ◽

Size Distributions ◽

Dropwise Condensation ◽

Dominant Feature ◽

Droplet Size Distributions ◽

Instantaneous Distribution

Abstract Droplet growth processes during dropwise condensation are simulated with a help of computer. We focus on instantaneous and time-averaged characteristics of droplet size distributions. Based on simulation results, shift of a single peak from small to large size is a significant characteristic for the instantaneous distribution before the first departure. Once condensing surface was refreshed time and again by shedding droplets, then coexistence, shift and combination of multiple peaks is the dominant feature. This indicates that the instantaneous droplet size distribution highly depends on growth time and target area. The findings can explain why different distribution characteristics were reported in experiments. Different from the instantaneous distribution, time-averaged size distributions for coalesced droplets follow a power-law style due to a collaboration of coalescence events and re-nucleation behaviors. However, the size range for the power-law distributions were affected by nucleation density. This requires an appropriate usage of the empirical or fractal model to predict theoretically heat transfer rate of dropwise condensation. The present work provides a comprehensive understanding of the instantaneous and time-averaged characteristics of droplet size distributions.

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The Effect of Heat Transfer Coefficient, Local Wet Bulb Temperature and Droplet Size Distribution Function on the Thermal Performance of Sprays

Journal of Heat Transfer ◽

10.1115/1.3450706 ◽

1977 ◽

Vol 99 (3) ◽

pp. 381-385 ◽

Cited By ~ 5

Author(s):

K. H. Chen ◽

G. J. Trezek

Keyword(s):

Heat Transfer ◽

Distribution Function ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Size Distribution ◽

Droplet Size ◽

Thermal Performance ◽

Correction Term ◽

Droplet Size Distribution ◽

Size Distribution Function

Energy balance considerations indicate that the droplet heat transfer coefficient, local wet bulb temperature, and droplet size distribution function are the basic parameters affecting spray system thermal performance. Within the range of available experimental data, results indicate that the Ranz-Marshall correlation gives an agreement to within ±5.0 percent of measured droplet temperatures at the pond surface for a medium wind range of between 2.5 and 5 m/s. The local wet bulb temperature is taken as the arithmetic mean of the initial and final wet bulb temperatures. For wind speeds greater than 3.5 m/s, the local wet bulb can be taken as the ambient. The modified log normal distribution of Mugele and Evans provides the best description of the droplet size distribution. Further, through the introduction of a correction term, the Spray Energy Release (SER) can be deduced from single droplet information.

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