MCQOPTIONS
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MCQOPTIONS
This section includes 640 Mcqs, each offering curated multiple-choice questions to sharpen your Chemical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m. The approximate surface temperature (K) is (Stefan-Boltzman constant = 5.67xl0 W/m.K) |
| A. | 1000 |
| B. | 727 |
| C. | 800 |
| D. | 1200 |
| Answer» B. 727 | |
| 52. |
Reynold's analogy states that (where, = Stanton number = friction factor) |
| A. | = 4 |
| B. | = f |
| Answer» B. = f | |
| 53. |
The equation, = /2, is the __________ analogy. |
| A. | Colburn |
| B. | Reynolds |
| C. | Prandtl |
| D. | none of these |
| Answer» C. Prandtl | |
| 54. |
Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m .°C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the |
| A. | higher condensing film co-efficient is desired. |
| B. | condensate is corrosive in nature. |
| C. | lower pressure drop through the exchanger is desired. |
| D. | temperature of the incoming vapor is very high. |
| Answer» C. lower pressure drop through the exchanger is desired. | |
| 55. |
Latent heat absorbed by 1 lb of water at 212°F, when it is changed to steam at 212°F, may be around __________ BTU. |
| A. | 180 |
| B. | 970 |
| C. | 3.97 |
| D. | none of these |
| Answer» B. 970 | |
| 56. |
Multiple effect evaporators are commonly used in the manufacture of P. Paper Q. Superphosphate R. Sugar S. Fats |
| A. | P and Q |
| B. | P and R |
| C. | P and S |
| D. | R and S |
| Answer» D. R and S | |
| 57. |
The variation of thermal conductivity of a metal with temperature is often correlated using an expression of the form = + . where, is the thermal conductivity and is the temperature (in °K). The units of 'a' in SI system will be |
| A. | W/m.k |
| B. | W/m |
| C. | W/m.k |
| D. | none, ' |
| E. | ' is just a number |
| Answer» D. none, ' | |
| 58. |
The thermal boundary layer at > 1 |
| A. | is thicker than hydrodynamic boundary layer. |
| B. | is thinner than hydrodynamic boundary layer. |
| C. | and the hydrodynamic boundary layer are identical. |
| D. | disappears. |
| Answer» C. and the hydrodynamic boundary layer are identical. | |
| 59. |
The Dietus-Boelter equation for convective leat transfercannot be used for |
| A. | low Reynold's number |
| B. | very low Grashoff number |
| C. | molten metals |
| D. | all (a), (b) and (c) |
| Answer» E. | |
| 60. |
The energy radiated from a surface at absolute temperature is related as |
| A. | ∝ |
| B. | ∝ |
| C. | ∝ |
| D. | none of these |
| Answer» C. ∝ | |
| 61. |
Grashoff number, which is defined as . β(T - T) ρ. L/μ, is proportional to the ratio of buoyancy force to __________ force. |
| A. | viscous |
| B. | elastic |
| C. | inertial |
| D. | none of these |
| Answer» B. elastic | |
| 62. |
1 BTU/hr.ft.°F is equal to __________ kcal/hr. m.°C. |
| A. | 1.49 |
| B. | 1 |
| C. | 4.88 |
| D. | none of these |
| Answer» B. 1 | |
| 63. |
Heat transfer by radiation between two bodies at & and in an ambient temperature of °C depends on |
| A. | - |
| B. | - |
| C. | - |
| D. | none of these |
| Answer» E. | |
| 64. |
According to Reynolds analogy, Stanton number is equal to (where, = Fanning friction factor) |
| A. | 2 |
| B. | /2 |
| C. | /4 |
| Answer» D. | |
| 65. |
The critical radius of insulation for cylindrical pipe is (where, = heat transfer coefficient at inside of the pipe ) |
| A. | / |
| B. | / |
| C. | / |
| D. | / |
| Answer» B. / | |
| 66. |
Which of the following situations can be approximated to a steady state heat transfer system? |
| A. | red hot steel slab (having outside surface temperature as 1300°C) exposed to the atmosheric air at 35°C |
| B. | 0 kg of dry saturated steam at 8 kgf/cm² flowing through a short length of stainless steel pipe exposed to atmospheric air at 35°C |
| C. | oiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180°C |
| D. | sub-cooled refrigerant liquid at 8°C flowing at the rate of 6 Kg/minute through a copper pipe exposed to atmospheric air at 35°C |
| Answer» C. oiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180°C | |
| 67. |
Which of the following forced convection heat transfer equation accounts for the liquid viscosity effect for viscous liquids? |
| A. | ittus-Boeltier equation |
| B. | ieder-Tate equation |
| C. | usselt equation |
| D. | one of these |
| Answer» C. usselt equation | |
| 68. |
Which one gives the monochromatic emissive power for black body radiation? |
| A. | lanck's law |
| B. | irchhoffs law |
| C. | ien's law |
| D. | tefan-Boltzman law |
| Answer» B. irchhoffs law | |
| 69. |
The left face of a one dimensional slab of thickness 0.2 m is maintained at 80°C and the right face is exposed to air at 30°C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the right face is 10 W/m².K. At steady state, the temperature of the right face in °C is |
| A. | 7.2 |
| B. | 1.2 |
| C. | 3.8 |
| D. | 8.7 |
| Answer» E. | |
| 70. |
Multiple effect evaporators are commonly used in the manufacture of P. Paper Q. Superphosphate R. Sugar S. Fats |
| A. | and Q |
| B. | and R |
| C. | and S |
| D. | and S |
| Answer» D. and S | |
| 71. |
The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body) |
| A. | T |
| B. | 1/T |
| C. | T⁴ |
| D. | ndependent of T |
| Answer» C. T⁴ | |
| 72. |
In thermal radiation for a black body (where, ε is emissivity and α is absorptivity) |
| A. | = 1; ε ≠ 1 |
| B. | ≠ 1, ε = 1 |
| C. | ≠ 1, ε ≠ 1 |
| D. | = 1; ε = 1 |
| Answer» E. | |
| 73. |
Which of the following is the most controlling factor for the rate of bubble detachment from the hot solid surface? |
| A. | iquid density |
| B. | iquid viscosity |
| C. | ot surface temperature |
| D. | nterfacial tension |
| Answer» E. | |
| 74. |
A composite flat wall of a furnace is made of two materials 'A' and 'B'. The thermal conductivity of 'A' is twice of that of material 'B', while the thickness of layer of 'A' is half that of B. If the temperature at the two sides of the wall are 400 and 1200°K, then the temperature drop (in °K) across the layer of material 'A' is |
| A. | 25 |
| B. | 33 |
| C. | 50 |
| D. | 60 |
| Answer» E. | |
| 75. |
(NRe.NPr)(D/L) is called the __________ number |
| A. | eclet |
| B. | tanton |
| C. | raetz |
| D. | one of these |
| Answer» D. one of these | |
| 76. |
The variation of thermal conductivity of a metal with temperature is often correlated using an expression of the form K = K₀ + at. where, K is the thermal conductivity and T is the temperature (in °K). The units of 'a' in SI system will be |
| A. | /m.k |
| B. | /m |
| C. | /m.k² |
| D. | one, A is just a number |
| Answer» D. one, A is just a number | |
| 77. |
The outlet temperature of cooling water in a heat exchanger is generally not allowed to exceed above 50°C in industrial practice mainly to avoid |
| A. | ts evaporation loss |
| B. | xcessive corrosion |
| C. | neconomic LMTD |
| D. | ecrease in heat exchanger efficiency |
| Answer» C. neconomic LMTD | |
| 78. |
(Cp . μ)/K is termed as the __________ number. |
| A. | rashoff |
| B. | usselt |
| C. | randtl |
| D. | tanton |
| Answer» D. tanton | |
| 79. |
A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. The density and the specific heat of the metal are 3000 kg/m³ and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m².K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60°C is |
| A. | 55 |
| B. | 5.5 |
| C. | 0.55 |
| D. | 0.15 |
| Answer» E. | |
| 80. |
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. | reater than that for uninsulated steam pipe |
| B. | ess than that of the uninsulated steam pipe |
| C. | qual to that of the uninsulated steam pipe |
| D. | ess than the steam pipe with 5 cms insulation |
| Answer» C. qual to that of the uninsulated steam pipe | |
| 81. |
For concentrating an aqueous solution of a material like anhydrous Na₂SO₄, whose solubility decreases with rise in temperature, the most suitable evaporator is a __________ evaporator. |
| A. | igh pressure |
| B. | acuum |
| C. | ackward feed |
| D. | one of these |
| Answer» C. ackward feed | |
| 82. |
A body cools down from 75°C to 70°C in 10 minutes. It will cool down from 70° C to 65° C in __________ minutes. |
| A. | 0 |
| B. | 10 |
| C. | 10 |
| D. | ither B or C, depends on the mass of the body |
| Answer» C. 10 | |
| 83. |
The overall heat transfer co-efficient for a shell and tube heat exchanger for clean surfaces is U0 = 400 W/m².K. The fouling factor after one year of operation is found to be hd0 = 2000 W/m².K. The overall heat transfer co-efficient at this time is |
| A. | 200W/m².K |
| B. | 94W/m².K |
| C. | 33W/m².K |
| D. | 87 W/m².K |
| Answer» D. 87 W/m².K | |
| 84. |
The Fourier number (defined as a.t/L²) is used in the analysis of problem involving heat transfer by |
| A. | orced convection |
| B. | atural convection |
| C. | ransient conduction |
| D. | teady state conduction |
| Answer» D. teady state conduction | |
| 85. |
A process stream of dilute aqueous solution flowing at the rate of10 Kg.s⁻¹ is to be heated. Steam condensate at 95°C is available for heating purpose, also at a rate of 10 Kg.s⁻¹. A 1 - 1 shell and tube heat exchanger is available. The best arrangement is |
| A. | ounter flow with process stream on shell side |
| B. | ounter flow with process stream on tube side |
| C. | arallel flow with process stream on shell side |
| D. | arallel flow with process stream on tube side |
| Answer» B. ounter flow with process stream on tube side | |
| 86. |
Which of the following has the lowest overall heat transfer co-efficient? |
| A. | owtherm |
| B. | olten sodium |
| C. | ater |
| D. | ir |
| Answer» E. | |
| 87. |
The critical radius of insulation for cylindrical pipe is (where, hi = heat transfer coefficient at inside of the pipe ) |
| A. | /h0 |
| B. | K/h0 |
| C. | i/K |
| D. | hi/K |
| Answer» B. K/h0 | |
| 88. |
Grashoff number, which is defined as g . β(Ts - T∞) ρ². L³/μ², is proportional to the ratio of buoyancy force to __________ force. |
| A. | iscous |
| B. | lastic |
| C. | nertial |
| D. | one of these |
| Answer» B. lastic | |
| 89. |
A long iron rod initially at a temperature of 20°C has one end dipped in boiling water (100°C) at time, t = 0. The curved surface of the rod is insulated so that heat conduction is one dimensional in the axial direction. The temperature at a distance 100 mm from the dipped end becomes 40°C at time, t = 200 s. The same temperature is achieved at a distance of 200 mm from the dipped end at time |
| A. | = 283 s |
| B. | = 356 s |
| C. | = 400 s |
| D. | = 800 s |
| Answer» E. | |
| 90. |
Which of the following has the minimum thermal conductivity? |
| A. | itrogen |
| B. | teel |
| C. | arbon black |
| D. | ar |
| Answer» B. teel | |
| 91. |
For small temperature difference, the heat transfer rate as per Newton's law of cooling is proportional to (where, Δt = excess temperature) |
| A. | t |
| B. | t² |
| C. | t³ |
| D. | Δt |
| Answer» B. t² | |
| 92. |
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) |
| Answer» D. (ΔT) | |
| 93. |
Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger? |
| A. | orrosiveness |
| B. | ouling characteristic |
| C. | iscosity |
| D. | one of these |
| Answer» E. | |
| 94. |
Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger? |
| A. | ube side pressure drop and the heat transfer rate |
| B. | onvective heat transfer co-efficient |
| C. | ffective tube surface area for convective heat transfer |
| D. | ll of the above |
| Answer» E. | |
| 95. |
In a laboratory test run, the rate of drying was found to be 0.5 x 10-3 kg/m².s, when the moisture content reduced from 0.4 to 0.1 on dry basis. The critical moisture content of the material is 0.08 on a dry basis. A tray dryer is used to dry 100 kg (dry basis) of the same material under identical conditions. The surface area of the material is 0.04 m²/kg of dry solid. The time required (in seconds) to reduce the moisture content of the solids from 0.3 to 0.2 (dry basis) is |
| A. | 000 |
| B. | 000 |
| C. | 000 |
| D. | 000 |
| Answer» D. 000 | |
| 96. |
Which of the following is not used as a medium for high temperature heating? |
| A. | owtherm |
| B. | ercury |
| C. | iquid metal (e.g. molten sodium) |
| D. | used salts (e.g., an eutectic mixture of 53% KNO₃, 40% NaNO₂and 7% NaNO₃) |
| Answer» C. iquid metal (e.g. molten sodium) | |
| 97. |
Which of the following is the most widely used heat insulating material for pipelines carrying steam? |
| A. | ar dolomite bricks followed by asbestos |
| B. | ireclay refractory followed by aluminium sheet |
| C. | otton followed by aluminium foil |
| D. | 5% magnesia cement and glass wool |
| Answer» E. | |
| 98. |
Hot water (0.01 m³ /min) enters the tube side of a counter current shell and tube heat exchanger at 80°C and leaves at 50°C. Cold oil (0.05 m³/min) of density 800 kg/m³ and specific heat of 2 kJ/kg.K enters at 20°C. The log mean temperature difference in °C is approximately |
| A. | 2 |
| B. | 7 |
| C. | 5 |
| D. | 0 |
| Answer» B. 7 | |
| 99. |
For a counter current heat exchanger with Tih = 80°C, T°c = 60°C, T°h = 50°C and Tic = 30°C, and the temperature difference between the two streams being the same everywhere along Z, the direction of flow of hot fluid. The temperature profile should satisfy |
| A. | ²T/dZ² > 0 |
| B. | ²T/dZ² = 0 |
| C. | ²T/dZ² < 0 |
| D. | T/dZ = 0 |
| Answer» C. ²T/dZ² < 0 | |
| 100. |
Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100°C and the inside heat transfer co-efficient is 3k/l. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade? |
| A. | 5.5 |
| B. | 3.75 |
| C. | 1.25 |
| D. | 8.25 |
| Answer» D. 8.25 | |