- (A) In case of heat transfer by purely forced convection, GR/Re 2 ≤ 1
- (B) The equivalent diameter of heat transfer for a duct of square cross-section (having each side as ‘x’) is equal to 4x
- (C) Distillation process is not the same as evaporation
- (D) The effectiveness of nucleate boiling depends basically on the ease with which the bubbles are formed and detached from the heating surface
Exam preparation MCQs with answers
Practice Pakistan's most useful MCQs for competitive exams
Prepare for NTS, PPSC, FPSC and subject-wise tests with fresh multiple choice questions, clear options and quick answer reveal.
Latest MCQs
- (A) Fluid movement under the influence of buoyant forces resulting from change in density takes place in case of natural convection
- (B) The ratio NNu/NRe . Npr is called the Stanton number
- (C) The Peclet number is a measure of the ratio of energy transport by convection to that by conduction
- (D) The Colburn jH factor for heat transfer is given by Nst Npr
- (A) Bubble size increases with the dynamic viscosity of the liquid in case of nucleate pool boiling
- (B) Thermal conductivity of a dry material is more than that of the damp material
- (C) Ratio of its capacity to economy equals the steam consumption in kg/hr in an evaporator
- (D) Vaporisation of organic substances in evaporator mostly causes foam formation
- (A) In drying a solid containing moisture above the critical moisture content the number of degrees of freedom is 2
- (B) Sherwood number in mass transfer corresponds to Nusselt number in heat transfer and Schmidt number to Prandtl number
- (C) Forced convection is relatively more effective in increasing the rate of mass transfer, if Schmidt number is larger
- (D) Hot gases at moderate pressure are usually in the shell side of shell and tube heat exchangers. At higher pressure, however, it is customary to put gas in the tube side
- (A) The emissivity of a surface decreases, if it gets corroded by atmospheric environment
- (B) The emissivity of a surface increases with increase in surface roughness
- (C) The emissivity of a polished surface is quite low
- (D) The emissivity of a non-metallic surface decreases with increase in the temperature
- (A) In process heat exchangers, saturated steam is preferred over the superheated steam
- (B) The maximum is the emissive power of a surface at a temperature T1 occurs at a wavelength of λ1. If the surface temperature is halved, the maximum in the emissive power would occur at a wavelength of 0.5 λ1
- (C) When a vertical plate is heated in infinite air environmental under natural convection conditions, the velocity profile in air, normal to the plate, exhibits a maximum
- (D) A body at 925 K emits an energy of 1.42 x 1011ζW/m2 (ζ is the Stefan-Boltzmann constant) in the wavelength band between 3 μm to 4 μm. The fraction of this energy in the total energy emitted over the entire wavelength range is equal to emissivity
- (A) jH = (St)(Pr)2/3 = f/2
- (B) jH = (St)(Pr)1/3 = f/2
- (C) jH = (St)2/3(Pr) = f/2
- (D) jH = (St)1/3(Pr) = f/2
- (A) Economy of a multiple effect evaporator is not influenced by the boiling point elevation
- (B) Two identical cubes of iron and copper will have the same heat content under the same conditions of temperature
- (C) Double pipe heat exchangers are mostly used in the field of refrigeration
- (D) Finned tube heat exchangers are suitable for heating air by steam
- (A) Higher is the temperature of the radiating body, higher is the wavelength of radiation
- (B) Logarithmic mean area is used for calculating the heat flow rate through a thick walled cylinder
- (C) The wavelength corresponding to maximum mono-chromatic emissive power increases with rise in temperature
- (D) Solid angle subtended by the finite surface at the radiating element is called the angle of incidence
- (A) ‘Solvates’ are chemical compounds formed by solute with their solvents. When water is the solvent, then it is called a ‘hydrate’
- (B) In heat exchanger calculations (Δt) weighted is used in place of Δt, when it involves more than one sequence of heating or cooling i.e., desuperheating & condensation or condensation & sub-cooling
- (C) Heat transfer co-efficient during nucleate boiling is not influenced by the agitation imparted
- (D) In case of short tube vertical evaporators, area of central downtake is about 50 to 100% of the total tube cross-sectional area
