Heat Transfer Operations Multiple Choice Questions on “Evaporators – Enthalpy Concentration Diagram”.
1. The straight line in the enthalpy concentration diagram is known as ___________
a) Dew line
b) Azeotropic line
c) Auxiliary line
d) Boiling line
Answer: a
2. What is the name of the line that joins the Dew line to the Boiling line in an enthalpy concentration diagram?
a) Azeotropic line
b) Isothermal line
c) Auxiliary line
d) Freezing line
Answer: b
Clarification: The given line in red defines the isothermal line which loves left with increasing temperature.
3. The _________ represents the line of 100% secondary liquid concentration in an enthalpy concentration diagram.
a) Top horizontal axis
b) Left vertical axis
c) Right vertical axis
d) Bottom horizontal axis
Answer: c
4. The auxiliary line value ____________ as we move towards higher concentrations in an enthalpy concentration diagram.
a) Increases
b) Decreases
c) Remains same
d) Exponentially increases
Answer: b
Clarification: The auxiliary line connects the boiling line and dew line by acting as a vertex of a right angle triangle with the hypotenuse as the isothermal line.
5. In an enthalpy concentration diagram, the point of intersection of a particular isothermal line to the Dew line is used to calculate _____________
a) Vapour phase composition
b) Liquid phase composition
c) Water mole fraction
d) Liquid phase weight fraction
Answer: a
Clarification: If we move along the isothermal line to the Dew Line and pin the intersection point, now we move vertically down to the composition value which is the required mole fraction in the vapour phase.
6. When we take a point between the Boiling line and the dew line in an enthalpy concentration diagram, then the mixture can exist in _______ in that particular point.
a) Liquid phase
b) Solid state
c) Gaseous state
d) Liquid and gas both
Answer: d
Clarification: The region of space between the Boiling line and the Dew line in an enthalpy concentration diagram exists in two phases which is the liquid phase and the gas phase. The liquid is dominant in the boiling line and gas in the dew line.
7. When we take a point between the Boiling line and the freezing line in an enthalpy concentration diagram, then the mixture can exist in _______ in that particular point.
a) Liquid phase
b) Solid state
c) Gaseous state
d) Liquid and gas both
Answer: a
Clarification: The region of space between the Boiling line and the freezing line in an enthalpy concentration diagram exists in single phase which is the liquid phase.