Practice Pakistan's most useful MCQs for competitive exams

Dropwise condensation is promoted on a/an ______________ surface?

• (A)  Glazed
• (B)  Oily
• (C)  Coated
• (D)  Smooth

Answer

Submitted By :Ali Uppal

Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger ?

• (A)  Corrosiveness & fouling characteristics
• (B)  Pressure
• (C)  Viscosity
• (D)  Density

Answer

Submitted By :Ali Uppal

It is desired to concentrate a 20% salt solution (20 kg of salt in 100 kg of solution) to a 30% salt solution in an evaporator. Consider a feed of 300 kg/min at 30°C. The boiling point of the solution is 110°C, the latent heat of vaporisation is 2100 kJ/kg and the specific heat of the solution is 4 kJ/kg.K. The rate at which the heat has to be supplied in (kJ/min) to the evaporator is____________________?

• (A)  3.06 × 105
• (B)  6.12 × 105
• (C)  7.24 × 105
• (D)  9.08 × 105

Answer

Submitted By :Ali Uppal

Fqra cold viscous feed, backward feed gives _____________ than forward feed?

• (A)  A higher capacity
• (B)  A lower capacity
• (C)  Lower economy
• (D)  None of these

Answer

Submitted By :Ali Uppal

The Graetz number is concerned with the___________________

• (A)  Mass transfer between a gas and a liquid
• (B)  Absorption with chemical reaction
• (C)  Heat transfer in turbulent flow
• (D)  Heat transfer in laminar flow

Answer

Submitted By :Ali Uppal

The unit of conductance in SI unit is_______________?

• (A)  W/m
• (B)  W/m2
• (C)  W/°K
• (D)  W/m°K

Answer

Submitted By :Ali Uppal

Which of the following has the lowest Prandtl number ?

• (A)  Molten sodium (a coolant used in fast breeder reactor)
• (B)  Water
• (C)  Transformer oil
• (D)  Dilute H2SO4

Answer

Submitted By :Ali Uppal

Peclet number (Pe) is given by____________________?

• (A)  Pe = Re.Pr
• (B)  Pe = Re/Pr
• (C)  Pe = Pr/Re
• (D)  Pe = Nu.Re

Answer

Submitted By :Ali Uppal

In Fourier’s law, the proportionality constant is called the______________________?

• (A)  Heat transfer co-efficient
• (B)  Thermal diffusivity
• (C)  Thermal conductivity
• (D)  Stefan-Boltzmann constant

Answer

Submitted By :Ali Uppal

When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is _______________?

• (A)  Free convection
• (B)  Entry length problem in laminar forced conduction (developing thermal boundary layer)
• (C)  Mixed convection (both free and forced)
• (D)  Forced convection

Answer

Submitted By :Ali Uppal