Chemical Heat Transfer Mcqs - Set 9

1)   The equivalent diameter for the annulus of a double pipe heat exchanger, whose inner pipe has fins on the outside is ______________ compared to the same size pipes without fins?

a. More
b. Less
c. Same
d. Unpredictable
Answer  Explanation 

ANSWER: Less

Explanation:
No explanation is available for this question!


2)   The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body)?

a. αT
b. α × 1/T
c. α T4
d. Independent of T
Answer  Explanation 

ANSWER: α × 1/T

Explanation:
No explanation is available for this question!


3)   According to Reynolds analogy, Stanton number is equal to (where, f = Fanning friction factor) ?

a. 2f
b. f
c. f/2
d. f/4
Answer  Explanation 

ANSWER: f/2

Explanation:
No explanation is available for this question!


4)   In forced circulation, the heating element is injected_________________?

a. Internally
b. Externally
c. Both A. and A.
d. Neither A. nor B.
Answer  Explanation 

ANSWER: Internally

Explanation:
No explanation is available for this question!


5)   For the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is_________________?

a. 3
b. 0.33
c. 1
d. 1.33
Answer  Explanation 

ANSWER: 1

Explanation:
No explanation is available for this question!


6)   The separation of liquid droplets from the vapor is done by a/an _____________ in the evaporators?

a. Steam ejector
b. Entrainment separator
c. Compressor
d. Vacuum pump
Answer  Explanation 

ANSWER: Entrainment separator

Explanation:
No explanation is available for this question!


7)   Nusselt number (for forced convection heat transfer) is a function of the _____________ number?

a. Prandtl
b. Reynolds
c. Both A. & B.
d. Neither A. nor B.
Answer  Explanation 

ANSWER: Reynolds

Explanation:
No explanation is available for this question!


8)   In case of _____________ boiling, the bubbles formed on a submerged hot surface get absorbed in the mass of the liquid?

a. Nucleate
b. Pool
c. Low pressure
d. None of these
Answer  Explanation 

ANSWER: Pool

Explanation:
No explanation is available for this question!


9)   In a boiling curve, the peak heat flux is called the _____________ point?

a. Nusselt
b. Leidenfrost
c. Boiling
d. Burnout
Answer  Explanation 

ANSWER: Leidenfrost

Explanation:
No explanation is available for this question!


10)   Film condensation is promoted on a/an _______________________ surface?

a. Oily
b. Coated
c. Clean & smooth
d. Dirty
Answer  Explanation 

ANSWER: Clean & smooth

Explanation:
No explanation is available for this question!


11)   In a multiple effect evaporator, the effect of boiling point elevation is to______________________?

a. Reduce the capacity
b. Reduce the economy
c. Increase the economy
d. None of these
Answer  Explanation 

ANSWER: Reduce the capacity

Explanation:
No explanation is available for this question!


12)   The heat flux in the nucleate boiling regimes is proportional to (where, ΔT = excess temperature) ?

a. (ΔT)2
b. (ΔT)4
c. (ΔT)3
d. √(ΔT)
Answer  Explanation 

ANSWER: (ΔT)3

Explanation:
No explanation is available for this question!


13)   In case of a vertical tube evaporator, with increase in the liquor level, the ____________ is increased?

a. Velocity of circulation
b. Liquor-film co-efficient
c. Both A. and B.
d. Neither A. and B.
Answer  Explanation 

ANSWER: Neither A. and B.

Explanation:
No explanation is available for this question!


14)   Sensible heat of hot industrial flue gases cannot be recovered by a/an________________?

a. Economiser
b. Regenerator
c. Ceramic recuperator
d. None of these
Answer  Explanation 

ANSWER: None of these

Explanation:
No explanation is available for this question!


15)   A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m2.°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be__________________?

a. Greater than that for un-insulated steam pipe
b. Less than that of the un-insulated steam pipe
c. Equal to that of the un-insulated steam pipe
d. Less than the steam pipe with 5 cms insulation
Answer  Explanation 

ANSWER: Less than that of the un-insulated steam pipe

Explanation:
No explanation is available for this question!


16)   In an interphase heat transfer process, the equilibrium state corresponds to equality of temperature in the two phases, while the condition for equilibrium in an interphase mass transfer process is equality of___________________?

a. Concentrations
b. Chemical potentials
c. Activity co-efficients
d. Mass transfer co-efficients
Answer  Explanation 

ANSWER: Concentrations

Explanation:
No explanation is available for this question!


17)   The critical radius ‘r’ of insulation on a pipe is given by____________________?

a. r = 2k/h
b. r = k/h
c. r = k/2h
d. r = h/k
Answer  Explanation 

ANSWER: r = k/h

Explanation:
No explanation is available for this question!


18)   In an extended surface heat exchanger, fluid having lower co-efficient________________?

a. Flows through the tube
b. Flows outside the tubes
c. Can flow either inside or outside the tubes
d. Should not be used as it gives very high pressure drop
Answer  Explanation 

ANSWER: Flows outside the tubes

Explanation:
No explanation is available for this question!


19)   If h1 = inner film co-efficient and /h2 = outer film co-efficient, then the overall heat transfer co-efficient is________________?

a. Always less than h1
b. Always between h1 and h2
c. Always higher than h2
d. Dependent on metal resistance
Answer  Explanation 

ANSWER: Always between h1 and h2

Explanation:
No explanation is available for this question!


20)   Convective heat transfer, in which heat is transferred by movement of warmed matter is described by___________________?

a. Fourier’s law
b. Newton’s law of cooling
c. Fick’s law
d. None of these
Answer  Explanation 

ANSWER: Newton’s law of cooling

Explanation:
No explanation is available for this question!


21)   Which of the following has the minimum absorptivity ?

a. Aluminium foil
b. Coal dust
c. Refractory bricks
d. Iron plates
Answer  Explanation 

ANSWER: Aluminium foil

Explanation:
No explanation is available for this question!


22)   In a forward feed multiple effect, the pressure build up will be____________________?

a. Least at the inlet of the first effect
b. Least at the outlet of the last effect
c. Highest at the inlet of the last effect
d. Highest at the outlet of the last effect
Answer  Explanation 

ANSWER: Least at the outlet of the last effect

Explanation:
No explanation is available for this question!


23)   Thermal diffusivity is given by__________________?

a. k/ρCp
b. ρCp/k
c. μCp/a
d. μ/hCp
Answer  Explanation 

ANSWER: k/ρCp

Explanation:
No explanation is available for this question!


24)   The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the___________________?

a. Heating volume
b. Heat transfer area
c. Nusselt number
d. None of these
Answer  Explanation 

ANSWER: Heat transfer area

Explanation:
No explanation is available for this question!


25)   In case of a vertical tube evaporator, with increase in the liquor level, the___________________?

a. Capacity of the evaporator is decreased
b. Capacity of the evaporator is increased
c. True temperature drop increases
d. Both B. and C.
Answer  Explanation 

ANSWER: Capacity of the evaporator is decreased

Explanation:
No explanation is available for this question!


26)   Low thermal conductivity of heat insulating materials is due to its_______________?

a. Dense structure
b. High proportion of air space
c. High specific heat
d. None of these
Answer  Explanation 

ANSWER: High proportion of air space

Explanation:
No explanation is available for this question!


27)   Low thermal conductivity of heat insulating materials is due to its_________________?

a. Dense structure
b. High proportion of air space
c. High specific heat
d. None of these
Answer  Explanation 

ANSWER: High proportion of air space

Explanation:
No explanation is available for this question!


28)   In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always__________________?

a. < 1
b. > 1
c. 1
d.
Answer  Explanation 

ANSWER: < 1

Explanation:
No explanation is available for this question!


29)   Small scale evaporation is done in a_________________?

a. Heat exchanger
b. Condenser
c. Multiple effect evaporator
d. Steam jacketed kettle
Answer  Explanation 

ANSWER: Steam jacketed kettle

Explanation:
No explanation is available for this question!


30)   In a single effect evaporator, the economy is________________?

a. 1
b. < 1
c. > 1
d. None of these
Answer  Explanation 

ANSWER: < 1

Explanation:
No explanation is available for this question!