Practice Pakistan's most useful MCQs for competitive exams

Critical value of the _____________ number governs the transition from laminar to turbulent flow in free convection heat transfer?

• (A)  Grashoff
• (B)  Reynolds
• (C)  Both ‘a’ & ‘b’
• (D)  Prandtl & Grashoff

Answer

Submitted By :Ali Uppal

Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the_________________?

• (A)  Existence of thermal boundary layer
• (B)  Temperature gradient produced due to density difference
• (C)  Buoyancy of the bubbles produced at active nucleation site
• (D)  None of these

Answer

Submitted By :Ali Uppal

In a forward feed multiple effect evaporator, the pressure is ____________________?

• (A)  Highest in last effect
• (B)  Lowest in last effect
• (C)  Same in all effects
• (D)  Dependent on the number of effects

Answer

Submitted By :Ali Uppal

For a liquid in laminar flow through a very long tube, when the exit fluid temperature approaches the wall temperature, the equation to be used is______________?

• (A)  Nu = 0.023 Re0.8. Pr0.4
• (B)  Nu = (π/2) Gz
• (C)  Nu = (2/π) Gz
• (D)  Nu = 2Gz0.5

Answer

Submitted By :Ali Uppal

The non-dimensional temperature gradient in a liquid at the wall of a pipe is the ____________________?

• (A)  Heat flux
• (B)  Nusselt number
• (C)  Prandtl number
• (D)  Schmidt number

Answer

Submitted By :Ali Uppal

The film co-efficient between condensing vapour and metal wall increases with _____________________?

• (A)  Increasing temperature of the vapour
• (B)  Decreasing temperature of the vapour
• (C)  Increasing viscosity of the film of condensate
• (D)  Increasing temperature drop

Answer

Submitted By :Ali Uppal

With increase in temperature, the thermal conductivity of most liquids_________________?

• (A)  Increases
• (B)  Decreases
• (C)  Remain same
• (D)  First increases upto a certain temperature and then becomes constant

Answer

Submitted By :Ali Uppal

In a shell and tube heat exchanger, putting a longitudinal baffle across the shell, forces the shell side fluid to pass _____________ through the heat exchanger ?

• (A)  Once
• (B)  Twice
• (C)  Thrice
• (D)  Four times

Answer

Submitted By :Ali Uppal

The driving potential for the crystal growth during crystallisation is the _______________ of the solution?

• (A)  Concentration
• (B)  Viscosity
• (C)  Super-saturation
• (D)  Density

Answer

Submitted By :Ali Uppal

Heat flux, as defined in heat flow is analogous to _______________ in electricity flow?

• (A)  Current
• (B)  Voltage
• (C)  Resistance
• (D)  None of these

Answer

Submitted By :Ali Uppal