Q1: Pick out the correct statement about the condensation.

ANS:B - Suitable coating or vapour additive is used to promote film wise condensation.

To promote filmwise condensation, a suitable coating or vapor additive is used to modify the surface properties of the condensing surface. The goal is to encourage the formation of a thin, continuous film of condensate on the surface rather than discrete droplets. This film enhances heat transfer by maximizing the surface area available for condensation and reducing the resistance to heat transfer compared to droplet-based condensation. Here's how suitable coatings or vapor additives can promote filmwise condensation:

1. Surface Modification: The coating or additive alters the surface properties of the condensing surface to promote wetting by the condensate. This can involve reducing surface tension, increasing surface energy, or modifying surface roughness to facilitate the spreading and continuity of the condensate film.
2. Enhanced Wetting: By promoting wetting, the coating or additive encourages the condensate to spread evenly across the surface rather than forming discrete droplets. This leads to the formation of a continuous condensate film, which maximizes the surface area available for heat transfer and minimizes the resistance to heat transfer.
3. Improved Heat Transfer: The continuous condensate film enhances heat transfer by providing a direct thermal pathway between the condensing vapor and the surface. This allows for efficient heat transfer across the condensate film, resulting in higher heat transfer rates compared to droplet-based condensation.
4. Applications: Filmwise condensation is particularly beneficial in applications where maximizing heat transfer efficiency is important, such as in heat exchangers, condensers, and HVAC systems. By promoting filmwise condensation, coatings or vapor additives can help optimize the performance of these systems and improve energy efficiency.