Download Aptitude Crack
img not found img not found

Heat Transfer - Engineering

Q1:

The film co-efficient between condensing vapour and metal wall increases with

A increasing temperature of the vapour.

B decreasing temperature of the vapour.

C increasing viscosity of the film of condensate.

D increasing temperature drop.

ANS:A - increasing temperature of the vapour.

The film coefficient between condensing vapor and a metal wall typically increases with increasing temperature of the vapor. Here's why:

  1. Temperature Difference: The film coefficient represents the effectiveness of heat transfer between the condensing vapor and the metal wall. A higher temperature difference between the vapor and the wall results in greater driving force for heat transfer, leading to higher heat transfer rates and thus a higher film coefficient.
  2. Increased Heat Flux: As the temperature of the vapor increases, the vapor becomes more energetic, which can lead to higher heat flux at the surface. This higher heat flux requires a higher film coefficient to transfer the increased heat efficiently to the metal wall.
  3. Enhanced Turbulence: Higher vapor temperatures can promote turbulence in the boundary layer near the surface, which can increase the mixing and enhance heat transfer. This increased mixing results in a higher film coefficient.
Therefore, the film coefficient typically increases with increasing temperature of the vapor, as it indicates more efficient heat transfer between the condensing vapor and the metal wall.