MCQOPTIONS
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MCQOPTIONS
This section includes 153 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Thermal conductivity of non-metallic amorphous solids with decrease in temperature |
| A. | increases |
| B. | decreases |
| C. | remains constant |
| D. | may increase or decrease depending on temperature |
| E. | unpredictable. |
| Answer» C. remains constant | |
| 2. |
When heat is transferred from one particle of hot body to another by actual motion of the heated particles, it is referred to as heat transfer by |
| A. | conduction |
| B. | convection |
| C. | radiation |
| D. | conduction and convection |
| E. | convection and radiation. |
| Answer» B. convection | |
| 3. |
When heat is transferred form hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by |
| A. | conduction |
| B. | convection |
| C. | radiation |
| D. | conduction and convection |
| E. | convection and radiation. |
| Answer» D. conduction and convection | |
| 4. |
When heat is Transferred by molecular collision, it is referred to as heat transfer by |
| A. | conduction |
| B. | convection |
| C. | radiation |
| D. | scattering |
| E. | convection and radiation. |
| Answer» C. radiation | |
| 5. |
Pick up the wrong case. Heat flowing from one side to other depends directly on |
| A. | face area |
| B. | time |
| C. | thickness |
| D. | temperature difference |
| E. | thermal conductivity. |
| Answer» D. temperature difference | |
| 6. |
Thermal conductivity of air at room temperature in kcal/m hr C is of the order of |
| A. | 0.002 |
| B. | 0.02 |
| C. | 0.01 |
| D. | 0.1 |
| E. | 0.5. |
| Answer» C. 0.01 | |
| 7. |
Heat produced when a steady state current, I passes through an electrical conductor having resistance, 'R' is |
| A. | IR |
| B. | I2R |
| C. | IR2 |
| D. | I2R2 |
| Answer» C. IR2 | |
| 8. |
For a fluid flowing in an annulus space, the wetted perimeter for heat transfer and pressure drop are |
| A. | Same |
| B. | Different |
| C. | Never different |
| D. | Linearly related |
| Answer» C. Never different | |
| 9. |
In case of surface condensers, a straight line is obtained on plotting 1/U vs. __________ on an ordinary graph paper. |
| A. | 1/V -0.8 |
| B. | V -0.8 |
| C. | V -2 |
| D. | 1/ V -2 |
| Answer» B. V -0.8 | |
| 10. |
When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids? |
| A. | At high fluid velocity |
| B. | At low velocity |
| C. | When fluid flows past a smooth surface |
| D. | None of these |
| Answer» B. At low velocity | |
| 11. |
For a liquid in laminar flow through a very long tube, when the exit fluid temperature approaches the wall temperature, the equation to be used is |
| A. | Nu = 0.023 Re0.8. Pr0.4 |
| B. | Nu = ( /2) Gz |
| C. | Nu = (2/ ) Gz |
| D. | Nu = 2Gz0.5 |
| Answer» D. Nu = 2Gz0.5 | |
| 12. |
For hot feed, forward feeding as compared to backward feeding results in __________ economy. |
| A. | Increased |
| B. | Decreased |
| C. | No effect on |
| D. | None of these |
| Answer» B. Decreased | |
| 13. |
Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling? |
| A. | Square pitch |
| B. | Triangular pitch |
| C. | Diagonal square pitch |
| D. | None of these |
| Answer» C. Diagonal square pitch | |
| 14. |
A multiple effect evaporator as compared to a single effect evaporator of the same capacity has |
| A. | Lower heat transfer area |
| B. | Lower steam economy |
| C. | Higher steam economy |
| D. | Higher solute concentration in the product |
| Answer» D. Higher solute concentration in the product | |
| 15. |
Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger? |
| A. | Corrosiveness |
| B. | Fouling characteristic |
| C. | Viscosity |
| D. | None of these |
| Answer» E. | |
| 16. |
In a shell and tube heat exchanger, the shell side fluid velocity can t be changed by changing the |
| A. | Tube layout |
| B. | Tube diameter |
| C. | Tube pitch |
| D. | Number of baffles |
| Answer» C. Tube pitch | |
| 17. |
The heat transfer co-efficient in film type condensation is __________ that for dropwise condensation. |
| A. | Greater than |
| B. | Lower than |
| C. | Is same as |
| D. | Half |
| Answer» C. Is same as | |
| 18. |
Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger? |
| A. | Corrosiveness & fouling characteristics |
| B. | Pressure |
| C. | Viscosity |
| D. | Density |
| Answer» E. | |
| 19. |
In a single evaporator system, the steam economy __________ by creating vacuum in the evaporator. |
| A. | Increases |
| B. | Decreases |
| C. | Remain constant |
| D. | May increase or decrease, depends on the vacuum |
| Answer» B. Decreases | |
| 20. |
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. | 10 |
| B. | > 10 |
| C. | < 10 |
| D. | Either (B) or (C), depends on the mass of the body |
| Answer» C. < 10 | |
| 21. |
Heat flux through several resistances in series in analogous to the current flowing through several |
| A. | Resistances in parallel |
| B. | Capacitors in series |
| C. | Resistances in series |
| D. | None of these |
| Answer» D. None of these | |
| 22. |
Overall thermal resistance for conductive heat transfer through a series of flat resistances is equal to the |
| A. | Maximum resistance in the series |
| B. | Sum of all resistances |
| C. | Average of all resistances |
| D. | Minimum resistance presents in the series |
| Answer» C. Average of all resistances | |
| 23. |
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 |
| Answer» D. Lower | |
| 24. |
Conductance is given by (where, x = thickness, A = heat flow area, K = thermal conductivity.) |
| A. | x/KA |
| B. | KA/x |
| C. | K/Ax |
| D. | A/Kx |
| Answer» C. K/Ax | |
| 25. |
The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is |
| A. | 2.36 |
| B. | 4.36 |
| C. | 120.36 |
| D. | Dependent on NRe only |
| Answer» C. 120.36 | |
| 26. |
The overall resistance for heat transfer through a series of flat resistance, is the __________ of the resistances. |
| A. | Average |
| B. | Geometric mean |
| C. | Product |
| D. | Sum |
| Answer» E. | |
| 27. |
The driving potential for the crystal growth during crystallisation is the __________ of the solution. |
| A. | Concentration |
| B. | Viscosity |
| C. | Super-saturation |
| D. | Density |
| Answer» D. Density | |
| 28. |
For flow over a flat plate, the ratio of thermal boundary layer thickness, 'xt' and hydrodynamic boundary layer thickness 'x' is equal to (where, NPr = Prandtl number) |
| A. | NPr |
| B. | NPr 1/3 |
| C. | NPr -1 |
| D. | NPr -1/3 |
| Answer» C. NPr -1 | |
| 29. |
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 |
| Answer» B. Lower capacity | |
| 30. |
For a cold dilute feed to produce thick viscous liquor, backward feeding as compared to forward feeding results in |
| A. | Increased economy |
| B. | Decreased economy |
| C. | Lower capacity |
| D. | No effect on economy |
| Answer» B. Decreased economy | |
| 31. |
A measure of the extent to which viscous heating is important relative to the heat flow resulting from the impressed temperature difference is represented by the __________ number. |
| A. | Condensation |
| B. | Grashoff |
| C. | Stanton |
| D. | Brinkman |
| Answer» E. | |
| 32. |
Choose the most important factor on which the heat conducted through a wall in a unit time will depend on? |
| A. | Thickness of the wall |
| B. | Area of the wall perpendicular to heat flow |
| C. | Material of the wall |
| D. | Temperature difference between the two surfaces of the wall |
| Answer» E. | |
| 33. |
Which of the following forced convection heat transfer equation accounts for the liquid viscosity effect for viscous liquids? |
| A. | Dittus-Boelter equation |
| B. | Sieder-Tate equation |
| C. | Nusselt equation |
| D. | None of these |
| Answer» C. Nusselt equation | |
| 34. |
Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator? |
| A. | Long vertical evaporator |
| B. | Horizontal tube evaporator |
| C. | Agitated film evaporator |
| D. | Calandria vertical tube evaporator |
| Answer» D. Calandria vertical tube evaporator | |
| 35. |
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. |
| A. | Boiling point |
| B. | Dynamic viscosity |
| C. | Kinematic viscosity |
| D. | Density |
| Answer» B. Dynamic viscosity | |
| 36. |
Steam consumption in kg/hr in case of an evaporator is given by (where, C & E are capacity the economy of the evaporator respectively). |
| A. | C/E |
| B. | E/C |
| C. | CE |
| D. | 1/CE |
| Answer» B. E/C | |
| 37. |
Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger? |
| A. | Tube side pressure drop and the heat transfer rate |
| B. | Convective heat transfer co-efficient |
| C. | Effective tube surface area for convective heat transfer |
| D. | All (A) (B) and (C) |
| Answer» E. | |
| 38. |
For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area |
| A. | Increases |
| B. | Decreases |
| C. | Remain constant |
| D. | Passes through a maxima |
| Answer» E. | |
| 39. |
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. | Counter flow with process stream on shell side |
| B. | Counter flow with process stream on tube side |
| C. | Parallel flow with process stream on shell side |
| D. | Parallel flow with process stream on tube side |
| Answer» B. Counter flow with process stream on tube side | |
| 40. |
For turbulent flow in a tube, the heat transfer co-efficient is obtained from the DittusBoelter 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 |
| Answer» D. 37 | |
| 41. |
In a shell and tube heat exchanger, the tube side heat transfer co-efficient just at the entrance of the tube is |
| A. | Infinity |
| B. | Zero |
| C. | Same as average heat transfer co-efficient for tube side |
| D. | None of these |
| Answer» B. Zero | |
| 42. |
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. | |
| Answer» B. > 1 | |
| 43. |
To reduce the tube side pressure drop for the same flow rate, the heat exchanger recommended is |
| A. | 1-2 heat exchanger |
| B. | 1-1 heat exchanger |
| C. | 3-2 heat exchanger |
| D. | 2-4 heat exchanger |
| Answer» C. 3-2 heat exchanger | |
| 44. |
Log mean temperature difference in case of counter flow compared to parallel flow will be |
| A. | same |
| B. | more |
| C. | less |
| D. | depends on other factors |
| E. | none of the above. |
| Answer» C. less | |
| 45. |
If a single tube pass heat exchanger is converted to two pass, then for the same flow rate, the pressure drop per unit length in tube side will |
| A. | Increase by 1.8 times |
| B. | Decrease by 22 |
| C. | Increase by 216 |
| D. | Remain unchanged |
| Answer» D. Remain unchanged | |
| 46. |
The local surface conductance for laminar film condensation on vertical surface is (where, t = film thickness) |
| A. | t |
| B. | 1/t |
| C. | t |
| D. | Independent of 't' |
| Answer» C. t | |
| 47. |
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 |
| Answer» B. Cumulatively decreases | |
| 48. |
The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe in laminar flow are |
| A. | Re.Gz |
| B. | Nu, Pr |
| C. | Nu, Pr, Re |
| D. | Nu, Gz |
| Answer» E. | |
| 49. |
In a 1-1 concurrent heat exchanger, if the tube side fluid outlet temperature is equal to the shell side fluid outlet temperature, then the LMTD is |
| A. | |
| B. | 0 |
| C. | Equal to the difference between hot and cold fluids inlet temperature |
| D. | Equal to the difference between hot fluid inlet temperature and cold fluid outlet temperature |
| Answer» C. Equal to the difference between hot and cold fluids inlet temperature | |
| 50. |
Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be |
| A. | 0.35 |
| B. | 0.45 |
| C. | 0.55 |
| D. | 0.85 |
| Answer» C. 0.55 | |