0% 1 Chemical Heat Transfer Quiz 2 1 / 50 Conduction occurs in the buffer zone for a fluid flowing through a heated pipe, only when Prandtl number is_________? 1 > 1 0.1 < 1 2 / 50 At constant temperature, the thermal conductivities of gases ______ with rise in pressure? Increase May increase or decrease; depends on the pressure Remain unchanged Decrease 3 / 50 Crystallisation of solids from a homogeneous solution is a/an _______ process? Highly endothermic None of these Exothermic Mildly endothermic 4 / 50 Dropwise condensation is promoted on a/an _______ surface? Glazed Oily Smooth Coated 5 / 50 Baffles are provided in heat exchangers to_____? Reduce heat transfer rate Submitted by:?Faheem Zaman Dhaunroo Remove dirt Increase heat transfer rate Reduce vibrations 6 / 50 Boiling of milk in an open vessel is an example of _______ boiling? Film Saturated nucleate Sub-cooled None of these 7 / 50 Duhring?s rule is important in solving problems on___________? Humidification Crystallisation Evaporation Distillation 8 / 50 Economy of a multiple effect evaporator depends upon the _______? Both A. and B. Rate of heat transfer Neither A. nor B. Heat balance consideration 9 / 50 Colburn analogy is applicable for the value of Prandtl number from__________? 0.001 to 1 0.5 to 5 120 to 400 0.6 to 120 10 / 50 Boiling point elevation of a solution of NaOH _______? Both B. and C Increases rapidly with temperature rise Is almost independent of pressure Is almost independent of temperature 11 / 50 Electromagnetic radiations propagate in vacuum with a velocity of ________ metre/second? 3 ? 1010 3 ? 1012 3 ? 105 3 ? 108 12 / 50 Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the_________? Average temperature of the fin Surrounding temperature Constant temperature equal to that of the base Temperature of the fin end 13 / 50 Correction is applied to LMTD for __________ flow? Cross Counter None of these Parallel 14 / 50 Evaporation by thermo compression results in the ___________? Saving of steam Both A. and B. Realisation of multiple effect economy in a single effect None of these 15 / 50 Cp?/K is termed as the _______ number? Nusselt Grashoff Prandtl Stanton 16 / 50 Evaporation of 1kg of water from a solution in a single effect evaporator requires about _________ kg of steam? 1.8-2 0.4 ? 0.6 2 ? 2.4 1-1.3 17 / 50 Economy of a multiple effect evaporator is not influenced much by the_________? Boiling point elevations Temperature of the feed Rate of heat transfer Ratio of the weight of the thin liquor to thick liquor 18 / 50 Electro-magnetic spectrum range, which is important for radiation varies from ______ microns? 100 to 1000 1 to 100 0.5 to 50 10 to 100 19 / 50 Choose the most important factor on which the heat conducted through a wall in a unit time will depend on ? Temperature difference between the two surfaces of the wall Thickness of the wall Area of the wall perpendicular to heat flow Material of the wall 20 / 50 Convective heat transfer, in which heat is transferred by movement of warmed matter is described by_____? Newton?s law of cooling Fick?s law Fourier?s law None of these 21 / 50 During crystallisation, formation of crystal can occur in _______ solution only? Saturated Supersaturated All A., B. and C. Under-saturated 22 / 50 Evaporator tubes are generally_______? Horizontal Inclined Vertical Random 23 / 50 Black liquor generated during paper manufacture is concentrated in a_____? Multiple effect evaporator Single effect evaporator followed by a crystalliser Multiple effect evaporators followed by a crystalliser Single effect evaporator 24 / 50 At what value of Prandtl number, conduction is negligible in the turbulent core of a fluid flowing through a heated pipe ? < 0.5 0.5 < 0.1 > 0.6 25 / 50 At Pr > 1, conduction in an ordinary fluid flowing through a heated pipe is limited to the_____? Both A. and B. Buffer zone Turbulent core Viscous sub-layer 26 / 50 Arithmetic mean area can be used in heat transfer problem to calculate the heat flow by conduction through a cylinder which is ______? Thick walled Having the value of Ao/Ai > 2 Both B. and C. Thin walled having the value of Ao Ai/< 2 27 / 50 Circulation pump is located below the evaporator to_____? Create more suction head None of these Avoid cavitation Avoid frequent priming 28 / 50 Baffles are provided in heat exchangers to increase the_________? Heat transfer area Heat transfer co-efficient Fouling factor Heat transfer rate 29 / 50 As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient ? Continues to decrease Continues to increase Goes through a maximum Goes through a minimum 30 / 50 Crystal size in a continuous crystalliser depends upon the_____? Degree of turbulence All A., B. and C Rate of heat transfer Degree of super-saturation 31 / 50 Bulk of the convective heat transfer resistance from a hot tube surface to the fluid flowing in it, is ___________? In the central core of the fluid Uniformly distributed throughout the fluid Mainly confined to a thin film of fluid near the surface None of these 32 / 50 Critical value of the ______ number governs the transition from laminar to turbulent flow in free convection heat transfer? Both ?a? & ?b? Prandtl & Grashoff Grashoff Reynolds 33 / 50 Boiling point elevation for a strong and concentrated solution is found by Duhring?s rule, which states that at the same pressure, the boiling point of a solution is a linear function of the ________ of pure water? Boiling point Dynamic viscosity Kinematic viscosity Density 34 / 50 Choose the correct equation ? Nu = (Re) (Pr) Nu = (Re) (Pr) (St) Nu = (Pr) (St) Nu = (Re) (Pr) (Gz) 35 / 50 Double pipe heat exchangers are used___________? Because it occupies less floor area When heat transfer area required is very low, i.e. (100-200 ft2). Because it is less costly When heat transfer area required is very high 36 / 50 Conductance is given by (where, x = thickness, A = heat flow area, K = thermal conductivity.)? x/KA KA/x K/Ax A/Kx 37 / 50 Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a long tube_____? Exit-fluid temperature > wall temperature Exit fluid temperature < wall temperature Graetz number > 100 Exit fluid temperature = wall temperature 38 / 50 Double pipe heat exchangers are preferably useful, when______? A corrosive liquid is to be heated High viscosity liquid is to be cooled Requirement of heat transfer area is low Overall heat transfer co-efficient is very high 39 / 50 Baffles in the shell side of a shell and tube heat exchanger ? Increase the cross-section of the shell side liquid Increase the shell side heat transfer co-efficient Decrease the shell side heat transfer co-efficient Force the liquid to flow parallel to the bank 40 / 50 Dittus-Boelter equation cannot be used for molten metals mainly due to its very low_______? Viscosity Thermal conductivity Prandtl number Grashoff number 41 / 50 Economy of an evaporator is influenced by the_______? Feed temperature Steam pressure Number of effect Both B. & C. 42 / 50 Dittus-Boelter equation used for the determination of heat transfer co-efficient is valid _____? When Grashoff number is very important For fluids in laminar flow For liquid metals For fluids in turbulent flow 43 / 50 Dropwise condensation occurs on _______ surfaces? Smooth clean Contaminated cooling Clean and dirt free Polished 44 / 50 Baffle spacing ______? Should be less than the inside diameter of the shell Is not the same as baffle pitch Should be less than one fifth the diameter of the shell None of these 45 / 50 Boiling point of a solution according to Duhring?s rule is a linear function of the ______ of water? Density Thermal conductivity Viscosity Boiling point (at the same pressure) 46 / 50 Corrosiveness of steam condensate is due to the presence of_________? CO2 Dissolved O2 Both A. & B. Neither A. nor B. 47 / 50 As per Kirchoff?s law, the ratio of the total radiating power to the absorptivity of a body depends on the________? Wavelength of monochromatic radiation Temperature of the body only Nature of material of body Both A. and B. 48 / 50 Controlling heat transfer film co-efficient is the one, which offers _______ resistance to heat transfer? No The largest The least Lower 49 / 50 Boiling point elevation of an ideal solution________? In independent of pressure Increases rapidly with temperature rise Both B. and C. Decreases rapidly with temperature rise 50 / 50 Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the ______ zone? Transition Both A & B Highly turbulent Laminar Provide Your Information Your score is The average score is 86% LinkedIn Facebook Twitter 0% Restart quiz Send feedback Share on facebook Facebook Share on twitter Twitter Share on whatsapp WhatsApp PrevChemical Heat Transfer Quiz 1 Chemical Heat Transfer Quiz 3Next
