Practice Pakistan's most useful MCQs for competitive exams

The variation of thermal conductivity of a metal with temperature is often correlated using an expression of the form K = K0 + at, where, K is the thermal conductivity and T is the temperature (in °K). The units of ‘a’ in SI system will be________________?

• (A)  W/m.k
• (B)  W/m
• (C)  W/m.k2
• (D)  None, ‘a’ is just a number

Answer

Submitted By :Ali Uppal

Colburn analogy is applicable for the value of Prandtl number from_________________?

• (A)  0.001 to 1
• (B)  0.6 to 120
• (C)  0.5 to 5
• (D)  120 to 400

Answer

Submitted By :Ali Uppal

If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows ____________ law?

• (A)  Hyperbolic
• (B)  Parabolic
• (C)  Linear
• (D)  Logarithmic

Answer

Submitted By :Ali Uppal

Viscous & heat sensitive liquids are concentrated in _____________ evaporators?

• (A)  Open pan
• (B)  Long tube
• (C)  Agitated film
• (D)  None of these

Answer

Submitted By :Ali Uppal

In case of surface condensers, a straight line is obtained on plotting 1/U vs. ____________ on an ordinary graph paper?

• (A)  1/V̅ -0.8
• (B)  V̅ -0.8
• (C)  V̅ -2
• (D)  1/ V̅ -2

Answer

Submitted By :Ali Uppal

Viscosity of gases ______________ with increase in temperature?

• (A)  Increase very rapidly
• (B)  Increase slowly
• (C)  Decrease slowly
• (D)  Remain unaffected

Answer

Submitted By :Ali Uppal

During crystallisation, formation of crystal can occur in ______________ solution only?

• (A)  Saturated
• (B)  Supersaturated
• (C)  Under-saturated
• (D)  All

Answer

Submitted By :Ali Uppal

When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids ?

• (A)  At high fluid velocity
• (B)  At low velocity
• (C)  When fluid flows past a smooth surface
• (D)  None of these

Answer

Submitted By :Ali Uppal

Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m2.°C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the_________________?

• (A)  Higher condensing film co-efficient is desired
• (B)  Condensate is corrosive in nature
• (C)  Lower pressure drop through the exchanger is desired
• (D)  Temperature of the incoming vapor is very high

Answer

Submitted By :Ali Uppal

A cube, sphere & a thin circular plate (all having same mass and made of same material) are all heated to 300°C and allowed to cool in natural air. Which one will cool the slowest ?

• (A)  Cube
• (B)  Plate
• (C)  Sphere
• (D)  All will cool at the same rate

Answer

Submitted By :Ali Uppal