Practice Pakistan's most useful MCQs for competitive exams

Which type of heat exchanger is preferred for heavy heat loads ?

• (A)  Double pipe
• (B)  Plate fine
• (C)  Series and parallel set of shell and tube
• (D)  None of these

Answer

Submitted By :Ali Uppal

With increase in porosity, the thermal conductivity of a solid substance__________________?

• (A)  Increases
• (B)  Decreases
• (C)  Remains unchanged
• (D)  May increase or decrease; depends on the solid

Answer

Submitted By :Ali Uppal

Vacuum is generally maintained in the vapour space of an evaporator mainly to__________________?

• (A)  Get economical temperature difference by using moderate pressure steam
• (B)  Facilitate forward feeding in multiple effect evaporation
• (C)  Concentrate heat sensitive materials
• (D)  Achieve very high concentration of the final product

Answer

Submitted By :Ali Uppal

The number of kg vaporised per kg of steam fed to the evaporator is defined as____________?

• (A)  Capacity
• (B)  Rate of evaporation
• (C)  Economy
• (D)  Rate of vaporisation

Answer

Submitted By :Ali Uppal

Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the _____________ zone?

• (A)  Laminar
• (B)  Transition
• (C)  Both A & B
• (D)  Highly turbulent

Answer

Submitted By :Ali Uppal

Which of the following is unimportant in forced convection ?

• (A)  Reynolds number
• (B)  Prandtl number
• (C)  Grashoff number
• (D)  None of these

Answer

Submitted By :Ali Uppal

Steam consumption in kg/hr in case of an evaporator is given by (where, C & E are capacity the economy of the evaporator respectively) ?

• (A)  C/E
• (B)  E/C
• (C)  CE
• (D)  1/CE

Answer

Submitted By :Ali Uppal

Dittus-Boelter equation cannot be used for molten metals mainly due to its very low_____________________?

• (A)  Prandtl number
• (B)  Grashoff number
• (C)  Thermal conductivity
• (D)  Viscosity

Answer

Submitted By :Ali Uppal

The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K = 0.04 W/m.°K and thickness 0.16m is 10 W/m2. The temperature of the inside wall is – 5°C. The outside wall temperature is___________________?

• (A)  25°C
• (B)  30°C
• (C)  35°C
• (D)  40°C

Answer

Submitted By :Ali Uppal

In a multipass shell and tube heat exchanger, tube side return pressure loss is equal to _____________ the velocity head?

• (A)  Twice
• (B)  Four times
• (C)  Square root of
• (D)  Square of

Answer

Submitted By :Ali Uppal