Fluid MechanicsHard
Question
Assume that a drop of liquid evaporates by decrease in its surface energy, so that its temperature remains unchanged. What should be the minimum radius of the drop for this to be possible? The surface tension is T, density of liquid is ρ and L is its latent heat of vaporization.
Options
A.
B.
C.
D.
Solution
If a layer of thickness dr is evaporates then change in surface energy
= (change in surface area) T
= (d(4πr 2))T = 8πrdrT
energy required to evaporate layer of thickness
dr = (4pr2dr)ρ .L
The process of evaporation only starts only if change in surface energy is just sufficient to evaporate the water layer
⇒ (4πr2dr)Lρ = (8πrdr) T
⇒
= (change in surface area) T
= (d(4πr 2))T = 8πrdrT
energy required to evaporate layer of thickness
dr = (4pr2dr)ρ .L
The process of evaporation only starts only if change in surface energy is just sufficient to evaporate the water layer
⇒ (4πr2dr)Lρ = (8πrdr) T
⇒
Create a free account to view solution
View Solution FreeMore Fluid Mechanics Questions
In CGS system, the Young′s modulus of a steel wire is 2 × 1012 dyne/cm2.To double the length of a wire of uni...A cubical block of wood 10 cm on a side, floats at the interface of oil and water as shown in figure. The density of oil...When a force is applied on a wire of uniform cross-sectional area 3 × 10-6 m2 and length 4 m, the increase in lengt...If the density of a metal is 7.8 g/cc its relative density is...The velocity of the liquid coming out of a small hole of a large vessel containing two different liquids of densities 2&...