Heat And Mass Transfer MCQ

Test your knowledge with important Heat And Mass Transfer MCQ and their applications. These MCQs are beneficial for competitive exams too. Explore 30 + more Heat And Mass Transfer MCQs at Bissoy

• The unit of Stefan-Boltzmann constant is
  ক

  watt/mK

  খ

  watt/m²K²

  গ

  watt/m²K⁴

  ঘ

  watt/mK²
• The unit of Stefan Boltzmann constant is
  ক

  watt/cm³K

  খ

  watt/cm⁴K

  গ

  watt²/cmK⁴

  ঘ

  watt/cm²K⁴
• When absorptivity (α) = 1, reflectivity (ρ) = 0 and transmissivity (τ) = 0, then the body is said to be a
  ক

  Black body

  খ

  Grey body

  গ

  Opaque body

  ঘ

  White body
• The energy distribution of an ideal reflector at higher temperatures is largely in the range of
  ক

  Shorter wavelength

  খ

  Longer wavelength

  গ

  Remain same at all wavelengths

  ঘ

  Wavelength has nothing to do with it
• In counter flow heat exchangers
  ক

  Both the fluids at inlet (of heat exchanger where hot fluid enters) are in their coldest state

  খ

  Both the fluids at inlet are in their hottest state

  গ

  Both the fluids at exit are in their hottest state

  ঘ

  One fluid is in hottest state and other in coldest state at inlet
• In counter current flow heat exchanger, the logarithmic temperature difference between the fluids is ________ as compared to parallel flow heat exchanger.
  ক

  Same

  খ

  Less

  গ

  Greater

  ঘ

  None of these
• Fourier's law of heat conduction is (where Q = Amount of heat flow through the body in unit time, A = Surface area of heat flow, taken at right angles to the direction of heat flow, dT = Temperature difference on the two faces of the body, dx = Thickness of the body, through which the heat flows, taken along the direction of heat flow and k = Thermal conductivity of the body)
  ক

  $${\text{kA}}\frac{{{\text{dT}}}}{{{\text{dx}}}}$$

  খ

  $${\text{kA}}\frac{{{\text{dx}}}}{{{\text{dT}}}}$$

  গ

  $${\text{k}}\frac{{{\text{dT}}}}{{{\text{dx}}}}$$

  ঘ

  $${\text{k}}\frac{{{\text{dx}}}}{{{\text{dT}}}}$$
• Upto the critical radius of insulation,
  ক

  Added insulation will increase heat loss

  খ

  Added insulation will decrease heat loss

  গ

  Convective heat loss will be less than conductive heat loss

  ঘ

  Heat flux will decrease
• The product of Reynolds number and Prandtl number is known as
  ক

  Stanton number

  খ

  Biot number

  গ

  Peclet number

  ঘ

  Grashoff number
• The ratio of Nusselt number and the product of Reynold's number and Prandtl number is equal to
  ক

  Stanton number

  খ

  Biot number

  গ

  Peclet number

  ঘ

  Grashoff number
• A steam pipe is to be lined with two layers of insulating materials of different thermal conductivities. For the minimum heat transfer,
  ক

  The better insulation must be put inside

  খ

  The better insulation must be put outside

  গ

  One could place either insulation on either side

  ঘ

  One should take into account the steam temperature before deciding as to which insulation is put where
• In a heat exchanger with one fluid evaporating or condensing, the surface area required is least in
  ক

  Parallel flow

  খ

  Counter flow

  গ

  Cross flow

  ঘ

  All of these
• Absorptivity of a body will be equal to its emissivity
  ক

  At all temperatures

  খ

  At one particular temperature

  গ

  When system is under thermal equilibrium

  ঘ

  At critical temperature
• According to Newton's law of cooling, the heat transfer from a hot body to a cold body is
  ক

  Directly proportional to the surface area

  খ

  Directly proportional to the difference of temperatures between the two bodies

  গ

  Either (A) or (B)

  ঘ

  Both (A) and (B)
• Fourier's law of heat conduction is valid for
  ক

  One dimensional cases only

  খ

  Two dimensional cases only

  গ

  Three dimensional cases only

  ঘ

  Regular surfaces having non-uniform temperature gradients
• The process of heat transfer from one particle of the body to another by the actual motion of the heated particles, is called
  ক

  Conduction

  খ

  Convection

  গ

  Radiation

  ঘ

  None of these
• The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles due to difference of density caused by temperature of the particle is known as
  ক

  Conduction

  খ

  Free convection

  গ

  Forced convection

  ঘ

  Radiation
• If the energy radiated per second per sq. cm. of the surface for wave lengths lying between λ and λ + dλ is represented by (eλ.dλ), then eλ is called
  ক

  Absorptive power

  খ

  Emissive power

  গ

  Emissivity

  ঘ

  None of these
• A designer chooses the values of fluid flow rates and specific heats in such a manner that the heat capacities of the two fluids are equal. A hot fluid enters the counter flow heat exchanger at 100°C and leaves at 60°C. A cold fluid enters the heat exchanger at 40°C. The mean temperature difference between the two fluids is
  ক

  20°C

  খ

  40°C

  গ

  60°C

  ঘ

  66.7°C
• In a shell and tube heat exchanger, baffles are provided on the shell side to
  ক

  Improve heat transfer

  খ

  Provide support for tubes

  গ

  Prevent stagnation of shell side fluid

  ঘ

  All of these
• Fourier's law of heat conduction gives the heat flow for
  ক

  Irregular surfaces

  খ

  Nonuniform temperature surfaces

  গ

  One dimensional cases only

  ঘ

  Two dimensional cases only
• Radiation is the process of heat transfer in which heat flows from a ________, in a straight line, without affecting the intervening medium.
  ক

  Cold body to hot body

  খ

  Hot body to cold body

  গ

  Smaller body to larger body

  ঘ

  Larger body to smaller body
• Which of the following is a case of steady state heat transfer?
  ক

  I.C. engine

  খ

  Air preheaters

  গ

  Heating of building in winter

  ঘ

  None of the above
• The ratio of surface convection resistance to the internal conduction resistance is known as
  ক

  Grashoff number

  খ

  Biot number

  গ

  Stanton number

  ঘ

  Prandtl number
• Moisture would find its way into insulation by vapour pressure unless it is prevented by
  ক

  High thickness of insulation

  খ

  High vapour pressure

  গ

  Less thermal conductivity insulator

  ঘ

  A vapour seal
• A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h₁, h₂ and h₃ respectively. The average heat transfer coefficient for the cube is
  ক

  $${{\text{h}}_1} + {{\text{h}}_2} + {{\text{h}}_3}$$

  খ

  $${\left( {{{\text{h}}_1}{{\text{h}}_2}{{\text{h}}_3}} \right)^{\frac{1}{3}}}$$

  গ

  $$\frac{1}{{{{\text{h}}_1}}} + \frac{1}{{{{\text{h}}_2}}} + \frac{1}{{{{\text{h}}_3}}}$$

  ঘ

  None of these
• An ordinary passenger aircraft requires a cooling system of capacity.
  ক

  2 TR

  খ

  4 TR

  গ

  8 TR

  ঘ

  10 TR
• Reynolds number (R_N) is given by (where h = Film coefficient, $$l$$ = Linear dimension, V = Velocity of fluid, k = Thermal conductivity, t = Temperature, $$\rho $$ = Density of fluid, c_p = Specific heat at constant pressure and $$\mu $$ = Coefficient of absolute viscosity)
  ক

  $${{\text{R}}_{\text{N}}} = \frac{{{\text{h}}l}}{{\text{k}}}$$

  খ

  $${{\text{R}}_{\text{N}}} = \frac{{\mu {{\text{c}}_{\text{p}}}}}{{\text{k}}}$$

  গ

  $${{\text{R}}_{\text{N}}} = \frac{{\rho {\text{V}}l}}{\mu }$$

  ঘ

  $${{\text{R}}_{\text{N}}} = \frac{{{{\text{V}}^2}}}{{{\text{t}}{{\text{c}}_{\text{p}}}}}$$
• Two long parallel surfaces each of emissivity 0.7 are maintained at different temperatures and accordingly have radiation heat exchange between them. It is desired to reduce 75% of the radiant heat transfer by inserting thin parallel shields of emissivity 1 on both sides. The number of shields should be
  ক

  One

  খ

  Two

  গ

  Three

  ঘ

  Four
• The thermal diffusivities for gases are generally
  ক

  More than those for liquids

  খ

  Less than those for liquids

  গ

  More than those for solids

  ঘ

  Dependent on the viscosity