1) Corrosiveness of steam condensate is due to the presence of________________? a. CO2 b. Dissolved O2 c. Both A. & B. d. Neither A. nor B.
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2) Solid angle subtended by the finite surface at the radiating element is_________________? a. Called the view factor b. Called the angle of vision c. Proportional to the square of the distance between surfaces d. Expressed in terms of radians
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3) A sphere of radius ‘R1’ is enclosed in a sphere of radius ‘R2’. The view (or shape) factor for radiative heat transfer of the outer sphere with respect to the inner sphere is ________________? a. 0 b. R2/(R1+R2) c. 1 d. (R1/R2)2
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4) One kilogram of water at 0°C is changed to superheated steam of one atm pressure and 300° C. The major heat consumption in the process will be to________________? a. Heat the water from 0°C to 100°C b. Evaporate the water c. To superheat the steam d. Data insufficient, can’t be predicted
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5) The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe in laminar flow are_______________? a. Re.Gz b. Nu, Pr c. Nu, Pr, Re d. Nu, Gz
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6) In case of heat transfer by conduction in a hollow cylinder, ______________ mean area is used to calculate the heat transfer rate? a. Geometric b. Arithmetic c. Logarithmic d. Either A., B. or C.
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7) The absorptivity of a grey body at a given temperature _____________ with increasing wavelength of radiation? a. Increases b. Decreases c. Remain constant d. May increase or decrease; depends on the material
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8) Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator ? a. Long vertical evaporator b. Horizontal tube evaporator c. Agitated film evaporator d. Calandria vertical tube evaporator
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9) Which of the following has the lowest overall heat transfer co-efficient ? a. Dowtherm b. Molten sodium c. Water d. Air
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10) Indirect contact heat exchangers are preferred over direct contact heat exchangers, because_________________? a. Heat transfer co-efficient are high b. There is no risk of contamination c. There is no mist formation d. Cost of equipment is lower
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11) Heat transfer by conduction in the turbulent core of a fluid flowing through a heated pipe is negligible, if the value of Prandtl number is_______________? a. 0.2 b. 0.4 c. 0.6 d. 0.8
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12) The actual temperature drop across the heating surface of an evaporator depends on the_______________? a. Liquid depth over the heating surface b. Solution being evaporated c. Pressure difference between the steam chest and the vapor space above the boiling liquid d. All A., B. and C.
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13) jH factor for heat transfer depends upon the ____________ number? a. Biot b. Nusselt c. Reynolds d. Prandtl
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14) A perfect black body is a perfect _____________ of radiation? a. Absorber b. Emitter c. Both A. & B. d. Neither A. nor B.
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15) The absorptivity of a body is equal to its emissivity _________________? a. At a particular temperature b. For circular bodies c. Under thermal equilibrium d. None of these
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16) The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C- 1 respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2.°C-1. The rate of heat loss from the outer surface in W.m-2is__________________? a. 165.4 b. 167.5 c. 172.5 d. 175
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17) If heat transfer rate varies with the time, it is termed as__________________? a. Forced convection b. Steady state conduction c. Monochromatic radiation d. None of these
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18) _____________ heat exchanger is used for chilling oil to be dewaxed? a. U-tube b. Double pipe c. Fixed tube d. Floating head
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19) It is not preferable to use superheated steam in evaporators, because of its very_________________? a. High temperature b. High pressure c. Low film co-efficient d. None of these
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20) A single pass air heater is connected to a two pass unit. For the air flow rate and other conditions remaining the same, the film heat transfer co-efficient for air will vary in the ratio of__________________? a. 2 b. 20.8 c. 20.2 d. 20.5
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21) At constant temperature, the thermal conductivities of gases _____________ with rise in pressure? a. Decrease b. Increase c. Remain unchanged d. May increase or decrease; depends on the pressure
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22) When warm and cold liquids are mixed, the heat transfer is mainly by_______________? a. Conduction b. Convection c. Radiation d. Both A. & C.
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23) Open pan evaporators are preferred to be used, when the solution to be concentrated is_________________? a. Scaling b. Highly viscous c. Corrosive d. Salty
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24) The equation, Nst = (f/2)/[1 + 5 (Npr – 1) √(f/2)], corresponds to ______________ analogy? a. Von-Karman b. Reynolds c. Colburn d. Prandtl
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25) The advantage of using a 1 – 2 shell and tube heat exchanger over a 1 – 1 shell and tube heat exchanger is_________________? a. Lower tube side pressure drop b. Lower shell side pressure drop c. Higher tube side heat transfer co-efficient d. Higher shell side heat transfer co-efficient
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26) Vent pipes are provided in a condenser to ________________? a. Remove non-condensable gases b. Purge the condenser c. Facilitate easy cleaning of tubes d. None of these
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27) LMTD for counter-flow and parallel flow heat exchanger will be the same, when the_________________? a. Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid) b. Outlet temperature of both the hot and cold fluid are same c. Outlet temperature of hot fluid is less than the outlet temperature of the cold fluid d. None of these
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28) Steam trap is used to_________________? a. Condense the steam flowing in the pipeline b. Remove water resulting from partial condensation of steam c. Stop the supply of steam d. None of these
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29) Planck’s distribution law is valid for _____________ bodies? a. Black b. White c. Coloured d. All A., B. & C.
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30) In a shell and tube heat exchanger, square pitch compared to triangular pitch__________________? a. Gives a higher shell side pressure drop b. Gives a lower shell side pressure drop c. Can pack more surface area into a shell of given diameter d. None of these
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