Which is better Filmwise or dropwise condensation?

The balance of evidence suggests that dropwise condensation is a more effective method of heat transfer than filmwise condensa- tion, and the presence of air insteam vapour significantly reduces the heat transfer..

What is the difference between film and dropwise condensation?

The rate of condensation is higher. The filmwise condensation occurs on less polished and uncontaminated surfaces. The dropwise condensation requires a highly polished surface or the surface with promoters coating. The size of the equipment for filmwise condensation is larger for the unit rate of condensation.

Is dropwise condensation feasible?

Despite years of research and numerous surface design possibilities, dropwise condensation cannot be maintained: coating deterioration and fluctuating process conditions commonly lead to surface flooding within hours or weeks.

Is dropwise condensation stable?

The good dropwise condensation stability made it the most stable lubricant for hexane dropwise condensation heat transfer, resulting in U̅dropwise ≈ 6.9 ± 0.9 kW/m2 K and hc,dropwise ≈ 9.6 ± 1.5 kW/m2 K.

Which type of condensation is more effective?

Dropwise condensation is one of the most effective mechanism of heat transfer and extremely large heat transfer coefficients can be achieved with this mechanism.

What is the meaning of dropwise?

Adverb. dropwise (not comparable) In drops; one drop at a time.

Why is dropwise condensation preferred?

Implications for Heat Transfer Under certain conditions, dropwise condensation provides for much higher heat transfer rates than filmwise condensation. Although a drop has a larger surface area than a film occupying the same surface area, this difference is relatively small.

What is meant by dropwise condensation?

In dropwise condensation the condensate liquid collects in the form of countless droplets of varying diameters on the condensing surface, instead of forming a continuous film, and does not wet the solid cooling surface.

How do I increase dropwise condensation?

Thus, the heat transferred per unit substrate area is expected to be especially large for the smallest drops, which helps explain the high heat transfer rates observed for dropwise condensation. This suggests that heat transfer rates can be increased by maximizing the surface coverage by very small drops.

How can dropwise condensation be achieved?

Dropwise condensation is achieved by adding a promoter chemical into the vapor, and/or roughened surfaces and surface and surface coated with hydrophobic impurities like fatty acids and organic compounds, known as dropwise promoters.

How is dropwise condensation achieved?

What is film type condensation?

Film condensation occurs when the temperature of a vertical, impermeable, and wettable wall next to a porous medium saturated with vapor falls below saturation temperature (Fig. 8.29). In addition to gravity-driven downward liquid flow, the liquid also infiltrates the vapor region due to capillary force.