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1) Pick out the wrong statement? a. The capacity of an evaporator is reduced by the boiling point elevation b. Corrosive liquid is normally passed through the tubes in a shell and tube heat exchanger c. Steam jet ejector is used for vapor compression in a thermal recompression evaporator d. Heat sensitive materials should be concentrated in high pressure evaporators
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2) Pick out the wrong statement ? 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
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3) Pick out the wrong statement ? a. Superheated steam is preferably not used for process heating because of its low heat transfer film co-efficient b. In a shell and tube heat exchanger, the shell pressure drop is maximum for orifice baffles c. S.I. unit of fouling factor is Watt/m2.°K d. Longitudinal fins are used in extended surface heat exchangers, when the direction of fluid flow is parallel to the axis of the tube
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4) Which of the following is correct ? a. Rate = Driving force × Resistance b. Driving force = Rate × Resistance c. Resistance = Driving force × Rate d. Rate = Resistance/Driving force
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5) Pick out the wrong statement ? a. Heat transfer by radiation cannot occur across an absolute volume b. In case of a shell and tube heat exchanger, the pressure drop through the shell is proportional to the number of times the fluid crosses the bundle be c. Propagation velocity for travel of heat radiation through vacuum is equal to the velocity of the light d. The amount of heat involved in the condensation or vaporisation of 1 kg of a fluid is the same
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6) Pick out the wrong statement? a. Swenson-Walker crystalliser is a batch crystalliser b. Super saturation of the solution is the driving potential for a crystal growth c. The liquor left after the removal of crystals from a solution is called mother liquor d. The first stage of crystal formation is called nucleation
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7) Pick out the wrong statement? a. Reciprocal of the resistance to heat flow is called thermal conductance b. Unit of thermal conductance is W/°K c. Thermal conductance of a wall of thickness ‘L’, thermal conductivity ‘k’ and heat flow area ‘A’ is kL/A d. None of these
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8) Pick out the wrong statement? a. Orifice baffles are never used in a shell and tube heat exchanger b. Pressure drop on the shell side of a heat exchanger depends upon tube pitch also c. In a horizontal tube evaporator, surface blanketing by air is avoided d. Split ring type and pull through type floating heads are two commonly used floating heads is heat exchangers
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9) Pick out the wrong statement ? a. The controlling resistance in case of heating of air by condensing steam is in the air fil b. The log mean temperature difference (LMTD) for counter flow and parallel flow can be theoretically same when any one of the fluids (hot or cold fluid) c. In case of a 1 – 2 shell and tube heat exchanger, the LMTD correction factor value increases sharply, when a temperature cross occurs d. Phase change in case of a pure fluid at a given pressure from liquid to vapor or vice-versa occurs at saturation temperature
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10) Pick out the wrong statement ? a. The condensing film co-efficient is about 3 times lower for vertical condenser as compared to the equivalent horizontal condenser for identical situat b. Film co-efficient for vaporisation decreases as a result of vapor binding c. In industrial practice, sub-cooling of condensate is required, when the condensate is a volatile liquid and is to be transferred for storage d. Overall heat transfer co-efficient in a heat exchanger is controlled by the value of the film coefficient, which is higher
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11) Pick out the wrong statement ? a. With change in temperature, the radiant energy emitted by a black body remains unchanged b. Absorptivity of a body approaches unity in case of diffuse reflection c. Absorptivity of a perfectly black body is unity d. Value of Stefan-Boltzmann constant is 4.876 × 10-8 KCal/m2.hr.°K4
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12) Choose the correct equation ? a. Nu = (Re) (Pr) (Gz) b. Nu = (Re) (Pr) (St) c. Nu = (Re) (Pr) d. Nu = (Pr) (St)
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13) Pick out the wrong statement ? 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., desuperheat 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
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14) Pick out the correct statement ? 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
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15) Pick out the wrong statement ? 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
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16) Pick out the correct equation ? 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
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17) Pick out the wrong statement? 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 c. When a vertical plate is heated in infinite air environmental under natural convection conditions, the velocity profile in air, normal to the plate, e 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
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18) Pick out the wrong statement/ 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
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19) Pick out the wrong statement? 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
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20) Pick out the wrong statement? 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
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21) Pick out the wrong statement ? a. Heat transfer from a hot body to cold body by the emission of heat waves is called radiation b. Filmwise condensation takes place on non-wettable surfaces c. The boiling point of a solution is affected by liquid head as well as boiling point elevation d. None of these
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22) Pick out the correct statement ? a. 1 kcal/hr.m.°C is equal to 1 BTU/hr. ft.°F b. In steady state heat conduction, the only property of the substance which determines the temperature distribution, is the thermal conductivity c. In unsteady state heat conduction, heat flows in the direction of temperature rise d. In heat transfer by forced convection, Grashoff number is very important
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23) Baffles are provided in heat exchangers to____________? a. Remove dirt b. Increase heat transfer rate c. Reduce vibrations d. Reduce heat transfer rate
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24) Maximum heat transfer rate can be expected in case of_________? a. Laminar flow b. Co-current flow c. Turbulent flow d. Heat flow rate is independent of nature of flow
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