Practice Pakistan's most useful MCQs for competitive exams

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

Submitted By :Ali Uppal

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

Submitted By :Ali Uppal

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

Submitted By :Ali Uppal

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

Submitted By :Ali Uppal

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

Submitted By :Ali Uppal

Film condensation is promoted on a/an _______________________ surface?

• (A)  Oily
• (B)  Coated
• (C)  Clean & smooth
• (D)  Dirty

Answer

Submitted By :Ali Uppal

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

• (A)  Nusselt
• (B)  Leidenfrost
• (C)  Boiling
• (D)  Burnout

Answer

Submitted By :Ali Uppal

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

Submitted By :Ali Uppal

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

Submitted By :Ali Uppal

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

Submitted By :Ali Uppal