1) The equivalent diameter for the annulus of a double pipe heat exchanger, whose inner pipe has fins on the outside is ______________ compared to the same size pipes without fins? a. More b. Less c. Same d. Unpredictable
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2) The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body)? a. αT b. α × 1/T c. α T4 d. Independent of T
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3) According to Reynolds analogy, Stanton number is equal to (where, f = Fanning friction factor) ? a. 2f b. f c. f/2 d. f/4
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4) In forced circulation, the heating element is injected_________________? a. Internally b. Externally c. Both A. and A. d. Neither A. nor B.
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5) For the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is_________________? a. 3 b. 0.33 c. 1 d. 1.33
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6) The separation of liquid droplets from the vapor is done by a/an _____________ in the evaporators? a. Steam ejector b. Entrainment separator c. Compressor d. Vacuum pump
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7) Nusselt number (for forced convection heat transfer) is a function of the _____________ number? a. Prandtl b. Reynolds c. Both A. & B. d. Neither A. nor B.
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8) In case of _____________ boiling, the bubbles formed on a submerged hot surface get absorbed in the mass of the liquid? a. Nucleate b. Pool c. Low pressure d. None of these
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9) In a boiling curve, the peak heat flux is called the _____________ point? a. Nusselt b. Leidenfrost c. Boiling d. Burnout
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10) Film condensation is promoted on a/an _______________________ surface? a. Oily b. Coated c. Clean & smooth d. Dirty
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11) In a multiple effect evaporator, the effect of boiling point elevation is to______________________? a. Reduce the capacity b. Reduce the economy c. Increase the economy d. None of these
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12) The heat flux in the nucleate boiling regimes is proportional to (where, ΔT = excess temperature) ? a. (ΔT)2 b. (ΔT)4 c. (ΔT)3 d. √(ΔT)
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13) In case of a vertical tube evaporator, with increase in the liquor level, the ____________ is increased? a. Velocity of circulation b. Liquor-film co-efficient c. Both A. and B. d. Neither A. and B.
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14) Sensible heat of hot industrial flue gases cannot be recovered by a/an________________? a. Economiser b. Regenerator c. Ceramic recuperator d. None of these
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15) A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m2.°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be__________________? a. Greater than that for un-insulated steam pipe b. Less than that of the un-insulated steam pipe c. Equal to that of the un-insulated steam pipe d. Less than the steam pipe with 5 cms insulation
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16) In an interphase heat transfer process, the equilibrium state corresponds to equality of temperature in the two phases, while the condition for equilibrium in an interphase mass transfer process is equality of___________________? a. Concentrations b. Chemical potentials c. Activity co-efficients d. Mass transfer co-efficients
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17) The critical radius ‘r’ of insulation on a pipe is given by____________________? a. r = 2k/h b. r = k/h c. r = k/2h d. r = h/k
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18) In an extended surface heat exchanger, fluid having lower co-efficient________________? a. Flows through the tube b. Flows outside the tubes c. Can flow either inside or outside the tubes d. Should not be used as it gives very high pressure drop
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19) If h1 = inner film co-efficient and /h2 = outer film co-efficient, then the overall heat transfer co-efficient is________________? a. Always less than h1 b. Always between h1 and h2 c. Always higher than h2 d. Dependent on metal resistance
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20) Convective heat transfer, in which heat is transferred by movement of warmed matter is described by___________________? a. Fourier’s law b. Newton’s law of cooling c. Fick’s law d. None of these
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21) Which of the following has the minimum absorptivity ? a. Aluminium foil b. Coal dust c. Refractory bricks d. Iron plates
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22) In a forward feed multiple effect, the pressure build up will be____________________? a. Least at the inlet of the first effect b. Least at the outlet of the last effect c. Highest at the inlet of the last effect d. Highest at the outlet of the last effect
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23) Thermal diffusivity is given by__________________? a. k/ρCp b. ρCp/k c. μCp/a d. μ/hCp
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24) The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the___________________? a. Heating volume b. Heat transfer area c. Nusselt number d. None of these
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25) In case of a vertical tube evaporator, with increase in the liquor level, the___________________? a. Capacity of the evaporator is decreased b. Capacity of the evaporator is increased c. True temperature drop increases d. Both B. and C.
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26) Low thermal conductivity of heat insulating materials is due to its_______________? a. Dense structure b. High proportion of air space c. High specific heat d. None of these
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27) Low thermal conductivity of heat insulating materials is due to its_________________? a. Dense structure b. High proportion of air space c. High specific heat d. None of these
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28) In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always__________________? a. < 1 b. > 1 c. 1 d. ∞
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29) Small scale evaporation is done in a_________________? a. Heat exchanger b. Condenser c. Multiple effect evaporator d. Steam jacketed kettle
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30) In a single effect evaporator, the economy is________________? a. 1 b. < 1 c. > 1 d. None of these
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