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1) LMTD correction factor which is to be applied for a cross-flow heat exchanger increases with increase in the number of shell passes. Its value for a single pass cross flow heat exchanger is __________________? a. 0 b. 1 c. > 1 d. < 1
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2) Thermal diffusivity is the most important in heat transfer by__________________? a. Conduction b. Radiation c. Condensation d. Natural convection
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3) If Prandtl number is greater than the Schmidt number, then the____________________? a. Thermal boundary layer lies inside the concentration boundary layer b. Concentration boundary layer lies inside the thermal boundary layer c. Thermal & concentration boundary layers are of equal thickness d. Hydrodynamic (i.e., momentum) boundary layer is thicker than the other two
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4) Bulk of the convective heat transfer resistance from a hot tube surface to the fluid flowing in it, is __________________? a. In the central core of the fluid b. Uniformly distributed throughout the fluid c. Mainly confined to a thin film of fluid near the surface d. None of these
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5) In a parallel flow heat exchanger, if the outlet temperature of hot and cold fluids are the same, then the log mean temperature difference (LMTD) is_________________? a. Minimum b. Maximum c. Zero d. Infinity
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6) Log mean temperature difference (LMTD) cannot be used, if ___________________? a. Heat transfer co-efficient over the entire heat exchanger is not constant b. There exists an unsteady state c. The heat capacity is not constant and there is a phase change d. None of these
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7) Kirchoff‟s law applies to _____________ radiation? a. Total b. Monochromatic c. Both A. & B. d. Neither A. nor B.
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8) Steam traps are provided in steam carrying pipelines to_________________? a. Condense steam b. Release excess steam pressure by bleeding steam c. Remove condensate and inert gases d. None of these
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9) Mode of heat transfer in which the fluid moves under the influence of changes in fluid pressure produced by external work is called_______________? a. Radiation b. Natural convection c. Forced convection d. Conduction
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10) For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area___________________? a. Increases b. DecreasesDecreasesDecreases c. Remain constant d. Passes through a maxima
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11) _____________ paint has the minimum absorption co-efficient? a. Black b. White lead c. Grey d. Light cream
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12) The film thickness for laminar film condensation on vertical surface _____________ from top to bottom? a. Cumulatively increases b. Cumulatively decreases c. Remain constant d. And the surface conductance increase
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13) Heat transfer by radiation between two bodies at T1 & T2 and in an ambient temperature of Ta°C depends on_____________? a. T1 – T2 b. T1 – Ta c. T2 – Ta d. None of these
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14) Duhring‟s rule is important in solving problems on__________________? a. Distillation b. Crystallisation c. Evaporation d. Humidification
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15) Which of the following is concerned with both heat and mass transfer ? a. Lewis relationship b. Nusselt number c. Kutateladze number d. Froude number
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16) Controlling heat transfer film co-efficient is the one, which offers ______________ resistance to heat transfer? a. No b. The least c. The largest d. Lower
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17) ____________ chart is known as transient heat conduction chart? a. Dirhing’s b. Heisler’s c. Mollier’s d. Cox
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18) Baffles in the shell side of a shell and tube heat exchanger ? a. Increase the cross-section of the shell side liquid b. Force the liquid to flow parallel to the bank c. Increase the shell side heat transfer co-efficient d. Decrease the shell side heat transfer co-efficient
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19) For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus- Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of________________? a. 1 b. 1.74 c. 6.1 d. 37
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20) What is the steam economy in case of a single effect evaporator system ? a. 1 b. > 1 c. < 1 d. 0.1
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21) Vibrations in the tubes of a shell and tube heat exchanger is induced due to the _________________? a. Flow of fluid on the tube and shell sides b. Oscillations in the flow of shell/tube sides fluid c. Vibrations transmitted through piping and/or supports due to external reasons d. All A., B. and C.
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22) The ratio of kinematic viscosity to thermal diffusivity is called the _______________ number? a. Peclet b. Prandtl c. Stanton d. Nusselt
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23) Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by h = 0.023 (K/D) (DVρ/μ)0.8 (CP.μ/k)0.4. This is valid for the value of NRe equal to_______________? a. 4000 b. > 10000
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24) A fluid is flowing inside the inner tube of a double pipe heat exchanger with diameter ‘d’. For a fixed mass flow rate, the tube side heat transfer co-efficient for turbulent flow conditions is proportional to_____________________? a. d0.8 b. d-0.2 c. d-1 d. d-1.8
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25) For a perfectly transparent surface (like gases), the____________________? a. Absorptivity = 0 b. Transmissivity = 1 c. Reflectivity = 0 d. All A., B. & C.
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26) If air (a non-condensing gas) is present in a condensing vapor stream, it will ______________ the condensation rate of vapor? a. Increase b. Decrease c. Not affect d. Increase the condensing film co-efficient as well as
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27) Heat waves_____________________? a. Cannot pass through vacuum b. Travel in straight line c. Can be reflected by a mirror d. Both B. and C.
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28) 1000 Kg of liquid at 30°C in a well stirred vessel has to be heated to 120°C, using immersed coils carrying condensing steam at 150°C. The area of the steam coils is 1.2 m2 and the overall heat transfer co-efficient to the liquid is 1500 W/m2.°C. Assuming negligible heat loss to the surrounding and specific heat capacity of the liquid to be 4 kJ/kg.°C, the time taken for the liquid to reach desired temperature will be__________________? a. 15 min b. 22 min c. 44 min d. 51 min
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29) For evaporation of viscous solution in a multiple effect evaporator, the preferred feeding scheme is _________________? a. Forward b. Backward c. Parallel d. None of these
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30) A backward feed multiple effect evaporator is better than forward feed for concentrating cold feed, because it provides __________________? a. Higher economy b. Lower capacity c. Both A. & B. d. Lower economy
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