Quantitative relations between transfer processes deal with the transfer of heat and mass across two bodies. The transfer of heat and mass is driven by the non-equilibrium thermal state of bodies. It involves the generation, use, conversion, and exchange of thermal energy between physical systems through various mechanisms such as conduction, convection, and radiation.
Question 1: Which of the following occur during the mass transfer?
a) Difference in concentration b) Difference in pressure
c) Difference in temperature d) Difference in chemical potential
Answer: d) Difference in chemical potential
Explanation: Mass transfer occurs to achieve equilibrium or to minimize the energy of the system. Mass transfer can occur even if there is no difference in concentration, pressure, and temperature.
Question 2: ____________ velocity is used to calculate the mass average velocity of the mixture.
a) Bulk b) Mean
c) Instantaneous d) None of these
Answer: b) Mean
Explanation: Mean velocity is used to calculate the mass average velocity of the mixture.
Question 3: ______________ forms the connecting link between the velocity and temperature profiles.
a) Biot number b) Prandtl number
c) Stanton number d) Fourier number
Answer: b) Prandtl number
Explanation: The temperature and velocity profile becomes identical when the Prandtl number is equal to one.
Question 4: Which number forms the connecting link between the temperature and concentration profiles?
a) Prandtl number b) Schmidt number
c) Fourier number d) Lewis number
Answer: d) Lewis number
Explanation: The temperature and concentration profile are identical when lewis’s number is equal to unity.
Question 5: Which one of the following has the highest emissivity?
a) Aluminium b) Polished copper
c) Tarnished copper d) Marble
Answer: c) Tarnished copper
Explanation: The emissivity of tarnished copper is 0.75 while that of polished aluminum, aluminum foil, and copper are 0.03, 0.05, and 0.03 respectively.
Question 6: The concentration of the two phases in a closed system at the interphase _____________.
a) continuously changes b) never changes
c) becomes zero d) increases
Answer: b) never changes
Explanation: The concentration changes only if the component of the two phases is added or removed. Generally, Interphase occurs at equilibrium. Once the additional component is added to a system at equilibrium, the concentration changes until it becomes uniform but differs from the previous.
Question 7: In steady-state conditions, concentration at any point never ________.
a) becomes zero b) decreases
c) increases d) changes
Answer: d) changes
Explanation: Generally, the net transfer remains the same at a steady-state condition as the concentration will be the same at every point.
Question 8: According to Lewis and Whitman theory, the departure from concentration equilibrium at the Interphase is due to __________
a) low mass transfer rates b) high mass transfer rates
c) moderate mass transfer rate d) None of these
Answer: b) high mass transfer rates
Explanation: Theoretically proved by Lewis and Whitman, that if the mass transfer rates are higher the concentration deviates from equilibrium.
Question 9: The equilibrium concentrations in the gas and the liquid phases, in mole fraction, give rise to a curve known as
a) Differential distribution curve
b) Differential concentration curve
c) Equilibrium distribution curve
d) Equilibrium concentration curve
Answer: c) Equilibrium distribution curve
Explanation: The equilibrium distribution curve represents the phase-phase equilibrium curve with the coordinates of mole fractions in both phases.
Question 10: The operation where enthalpy remains constant throughout the initial and final condition is ___________.
a) adiabatic b) isothermal
c) non-adiabatic d) non-isothermal
Answer: a) adiabatic
Explanation: In an adiabatic condition, there is no addition or removal of heat. Therefore, the enthalpy remains constant.