MCQOPTIONS
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MCQOPTIONS
This section includes 362 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. |
The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body. This statement is known as |
| A. | ien's law |
| B. | tefan's law |
| C. | irchhoff's law |
| D. | lanck's law |
| Answer» D. lanck's law | |
| 2. |
Two long parallel surfaces each of emissivity 0.7 are maintained at different temperatures and accordingly have radiation heat exchange between them. It is desired to reduce 75% of the radiant heat transfer by inserting thin parallel shields of emissivity 1 on both sides. The number of shields should be |
| A. | ne |
| B. | wo |
| C. | hree |
| D. | our |
| Answer» D. our | |
| 3. |
According to Stefan Boltzmann law, the total radiation from a black body per second per unit area is directly proportional to the |
| A. | bsolute temperature |
| B. | quare of the absolute temperature |
| C. | ube of the absolute temperature |
| D. | ourth power of the absolute temperature |
| Answer» E. | |
| 4. |
In counter current flow heat exchanger, the logarithmic temperature difference between the fluids is ________ as compared to parallel flow heat exchanger. |
| A. | ame |
| B. | ess |
| C. | reater |
| D. | one of these |
| Answer» D. one of these | |
| 5. |
The engine oil at 150 degree Celsius is cooled to 80 degree Celsius in a parallel flow heat exchanger by water entering at 25 degree Celsius and leaving at 60 degree Celsius. Estimate the number of transfer units |
| A. | 1.221 |
| B. | 2.221 |
| C. | 3.221 |
| D. | 4.221 |
| Answer» B. 2.221 | |
| 6. |
After being in service for a period of six months, a heat exchanger transforms 10% less heat than it does what new. Determine the effective fouling factor in terms of its clean overall heat transfer coefficient. It may be presumed that the heat exchanger operates between the same temperature differentials and that there is no change in the effective surface area due to scale build up |
| A. | 0.13/ U CLEAN |
| B. | 0.11/ U CLEAN |
| C. | 0.09/ U CLEAN |
| D. | 0.07/ U CLEAN |
| Answer» C. 0.09/ U CLEAN | |
| 7. |
What is the value of specific heat for Bakelite in J/kg K? |
| A. | 1665 |
| B. | 1565 |
| C. | 1465 |
| D. | 1365 |
| Answer» D. 1365 | |
| 8. |
In a food processing plant, a brine solution is heated from – 12 degree Celsius to – 65 degree Celsius in a double pipe parallel flow heat exchanger by water entering at 35 degree Celsius and leaving at 20.5 degree Celsius. Let the rate of flow is 9 kg/min. Estimate the area of heat exchanger for an overall heat transfer coefficient of 860 W/m² K. For water c P = 4.186 * 10³ J/kg K |
| A. | 293 m² |
| B. | 0.293 m² |
| C. | 7. 293 m² |
| D. | 8. 293 m² |
| Answer» C. 7. 293 m² | |
| 9. |
What is the value of specific heat for brick in J/kg K? |
| A. | 835 |
| B. | 735 |
| C. | 635 |
| D. | 535 |
| Answer» B. 735 | |
| 10. |
A counter flow heat exchanger is used to col 2000 kg/hr of oil (c p = 2.5 k J/kg K) from 105 degree Celsius to 30 degree Celsius by the use of water entering at 15 degree Celsius. If the overall heat transfer coefficient is expected to be 1.5 k W/m² K, find out the water flow rate. Presume that the exit temperature of the water is not to exceed 80 degree Celsius |
| A. | 1680.2 kg/hr |
| B. | 1580.2 kg/hr |
| C. | 1480.2 kg/hr |
| D. | 1380.2 kg/hr |
| Answer» E. | |
| 11. |
In a gas turbine recuperator, the expression for effectiveness for the parallel flow configuration reduces to |
| A. | 1 – exponential (- NTU)/3 |
| B. | 1 – exponential (- NTU)/4 |
| C. | 1 – exponential (- 2 NTU)/2 |
| D. | 1 – exponential (- NTU)/6 |
| Answer» D. 1 – exponential (- NTU)/6 | |
| 12. |
How many fluids remain at constant temperature during the process of boiling and condensation? |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» B. 2 | |
| 13. |
In a counter flow heat exchanger, water flowing through a tube of 10 cm inner diameter is heated by steam condensing on the outside of the tube. The convective film coefficient on the water and steam side are estimated to be 12000 and 20000 k J/m² hr degree. Neglecting tube thickness and its resistance to heat flow, workout the overall heat transfer coefficient for the heat exchanger |
| A. | 4500 k J/m² hr degree |
| B. | 5500 k J/m² hr degree |
| C. | 6500 k J/m² hr degree |
| D. | 7500 k J/m² hr degree |
| Answer» E. | |
| 14. |
For what value of end temperature difference ratio, is the arithmetic mean temperature difference 5% higher than the log-mean temperature difference? |
| A. | 2.4 |
| B. | 2.3 |
| C. | 2.2 |
| D. | 2.1 |
| Answer» D. 2.1 | |
| 15. |
For evaporators and condensers, for the given conditions, the logarithmic mean temperature difference for parallel flow is |
| A. | Does not depend on counter flow |
| B. | Smaller than counter flow |
| C. | Greater than counter flow |
| D. | Equal to counter flow |
| Answer» E. | |
| 16. |
Exhaust gases (c P = 1.12 k J/kg K) flowing through a tubular heat exchanger at the rate of 1200 kg/hr are cooled from 400 degree Celsius to 120 degree Celsius. This cooling is affected by water (c P = 4.18 k J/kg K) that enters the system at 10 degree Celsius at the rate of 1500 kg/hr. If the overall heat transfer coefficient is 500 k J/m² hr degree, what heat exchanger area is required to handle the load for parallel flow arrangement? |
| A. | 7.547 m² |
| B. | 6.547 m² |
| C. | 5.547 m² |
| D. | 4.547 m² |
| Answer» E. | |
| 17. |
What is the maximum efficiency for parallel flow heat exchanger? |
| A. | 5% |
| B. | 10% |
| C. | 20% |
| D. | 50% |
| Answer» B. 10% | |
| 18. |
Water (specific heat = 4 k J/kg K) enters a cross flow exchanger (both fluids unmixed) at 15 degree Celsius and flows at the rate of 7.5 kg/s. It cools air (C P = 1 k J/kg K) flowing at the rate of 10 kg/s from an inlet temperature of 120 degree Celsius. For an overall heat transfer coefficient of 780 k J/m² hr degree and the surface area is 240 m², determine the NTU |
| A. | 4.2 |
| B. | 5.2 |
| C. | 6.2 |
| D. | 7.2 |
| Answer» C. 6.2 | |
| 19. |
Pick the odd one out. |
| A. | Open feed water heaters |
| B. | Jet condensers |
| C. | De-super heaters |
| D. | Surface condensers |
| Answer» E. | |
| 20. |
Which one is having lowest value of overall heat transfer coefficient? |
| A. | Steam |
| B. | Air condensers |
| C. | Air to heavy tars |
| D. | Ammonia condensers |
| Answer» D. Ammonia condensers | |
| 21. |
What is the value of overall heat transfer coefficient for air condensers? |
| A. | 350-780 W/m² K |
| B. | 250 -900 W/m² K |
| C. | 200-350 W/m² K |
| D. | 200-1950 W/m² K |
| Answer» B. 250 -900 W/m² K | |
| 22. |
What is the value of overall heat transfer coefficient for air to heavy tars and liquid? |
| A. | As low as 45 W/m² K |
| B. | As low as 40 W/m² K |
| C. | As low as 35 W/m² K |
| D. | As low as 30 W/m² K |
| Answer» B. As low as 40 W/m² K | |
| 23. |
Hot water having specific heat 4200 J/kg K flows through a heat exchanger at the rate of 4 kg/min with an inlet temperature of 100 degree Celsius. A cold fluid having a specific heat 2400 J/kg K flows in at a rate of 8 kg/min and with inlet temperature 20 degree Celsius. Make calculations for maximum possible effectiveness if the fluid flow conforms to parallel flow arrangement |
| A. | 0.533 |
| B. | 0.633 |
| C. | 0.733 |
| D. | 1 |
| Answer» B. 0.633 | |
| 24. |
The rear window of an automobile is made of thick glass i.e. AB = 5 mm and thermal conductivity is 0.8 W/m degree. To defrost this window, a thin transparent film type heating element has been fixed to its inner surface. For the conditions given below, determine the electric power that must be provided per unit area of window if a temperature 5 degree Celsius is maintained at its outer surface. Interior air temperature and the corresponding surface coefficient are 20 degree Celsius and 12 W/m² degree. Surrounding air temperature and the corresponding surface coefficient are – 15 degree Celsius and 70 W/m² degree. Electric heater provides uniform heat flux |
| A. | 232.5 /m² |
| B. | 1232.5 /m² |
| C. | 2232.5 /m² |
| D. | 3232.5 /m² |
| Answer» C. 2232.5 /m² | |
| 25. |
A copper pipe (k = 350 W/m K) having inner diameter of 1.75 cm and 2.0 cm outside diameter conveys water and the oil flows through the annular passage between this pipe and a steel pipe. On the water side, the film coefficient is 4600 W/m² K and the fouling factor is 0.00034 m² K/W. The corresponding values for the oil side are 1200 W/m² K and 0.00086 m² K/W. Estimate the overall heat transfer coefficient between the oil and water |
| A. | 235.16 W/m² K |
| B. | 335.16 W/m² K |
| C. | 435.16 W/m² K |
| D. | 535.16 W/m² K |
| Answer» D. 535.16 W/m² K | |
| 26. |
NTU is a number of transfer units, dimensionless parameter defined as |
| A. | U A/C MIN |
| B. | 2 U A/C MIN |
| C. | 3 U A/C MIN |
| D. | 4 U A/C MIN |
| Answer» B. 2 U A/C MIN | |
| 27. |
In a gas turbine recuperator, the capacity ratio becomes |
| A. | 2 |
| B. | 1 |
| C. | 4 |
| D. | 3 |
| Answer» C. 4 | |
| 28. |
In how many categories heat exchangers are classified on the basis of mechanical design of heat exchanger surface? |
| A. | 2 |
| B. | 4 |
| C. | 1 |
| D. | 3 |
| Answer» E. | |
| 29. |
Figure represents the block diagram of a heat exchanger. There were some aspects in the design and performance analysis of a heat exchanger. Identify the correct one |
| A. | The coolant picks up heat = m h c c (t c1 – t c2) |
| B. | The hot fluid gives up heat = m h c h (t h1 – t c2) |
| C. | The coolant picks up heat = m c c h (t h1 – t c2) |
| D. | The hot fluid gives up heat = m h c h (t h1 – t h2) |
| Answer» E. | |
| 30. |
After expansion from a gas turbine, the hot exhaust gases are used to heat the compressed air from a compressor with the help of a cross flow heat exchanger of 0.8 effectiveness. What is the number of transfer units of the heat exchanger? |
| A. | 2 |
| B. | 4 |
| C. | 8 |
| D. | 16 |
| Answer» C. 8 | |
| 31. |
Which one is having highest value of specific heat? |
| A. | Asphalt |
| B. | Bakelite |
| C. | Chrome brick |
| D. | Fire clay |
| Answer» C. Chrome brick | |
| 32. |
A steam condenser is transferring 250 k W of thermal energy at a condensing temperature of 65 degree Celsius. The cooling water enters the condenser at 20 degree Celsius with a flow rate of 7500 kg/hr. If overall heat transfer coefficient for the condenser surface is 1250 W/m² K, what surface area is required to handle this load? |
| A. | 4.08 m² |
| B. | 5.08 m² |
| C. | 6.08 m² |
| D. | 7.08 m² |
| Answer» E. | |
| 33. |
The curve of effectiveness versus NTU parameters indicates the relationship between(i) Effectivenes(ii) NTU MAX(iii) C MIN/C MAXIdentify the correct statements |
| A. | 1 and 2 |
| B. | 1, 2 and 3 |
| C. | 2 only |
| D. | 3 only |
| Answer» C. 2 only | |
| 34. |
What is the value of overall heat transfer coefficient for air to low viscosity liquid? |
| A. | As high as 900 W/m² K |
| B. | As high as 800 W/m² K |
| C. | As high as 700 W/m² K |
| D. | As high as 600 W/m² K |
| Answer» E. | |
| 35. |
Unit of fouling factor is |
| A. | m² K/kcal |
| B. | m² hr K/kcal |
| C. | m² hr/kcal |
| D. | m² hr K |
| Answer» C. m² hr/kcal | |
| 36. |
In a surface condenser, the water flowing through a series of tubes at the rate of 200 kg/hr is heated from 15 degree Celsius to 75 degree Celsius. The steam condenses on the outside surface of tubes at atmospheric pressure and the overall heat transfer coefficient is estimated at 860 k J/m² hr degree. Find the number of transfer units of the heat exchanger. At the condensing pressure, stream has saturation temperature 0f 100 degree Celsius and the latent heat of vaporization is 2160 k J/kg. Further, the steam is initially just saturated and the condensate leaves the exchanger without sub-cooling i.e. only latent heat of condensing steam is transferred to water. Take specific heat of water as 4 k J/kg K |
| A. | 3.224 |
| B. | 2.224 |
| C. | 1.224 |
| D. | 0.224 |
| Answer» D. 0.224 | |
| 37. |
Many types of heat exchangers have been developed to meet the widely varying applications. Based upon their(i) Operating principle(ii) Arrangement of flow path(iii) DesignIdentify the correct statements |
| A. | 1, 2 and 3 |
| B. | 1 and 2 |
| C. | 2 and 3 |
| D. | 1 and 3 |
| Answer» B. 1 and 2 | |
| 38. |
What is the value of fouling factor for engine exhaust? |
| A. | 0.002 m² K/W |
| B. | 0.003 m² K/W |
| C. | 0.004 m² K/W |
| D. | 0.005 m² K/W |
| Answer» B. 0.003 m² K/W | |
| 39. |
What is the value of overall heat transfer coefficient for steam condensers? |
| A. | 200-9000 W/m² K |
| B. | 3000-5500 W/m² K |
| C. | 2000-9500 W/m² K |
| D. | 1500-5000 W/m² K |
| Answer» E. | |
| 40. |
In a surface condenser, the water flowing through a series of tubes at the rate of 200 kg/hr is heated from 15 degree Celsius to 75 degree Celsius. The steam condenses on the outside surface of tubes at atmospheric pressure and the overall heat transfer coefficient is estimated at 860 k J/m² hr degree. Find the effectiveness of the heat exchanger. At the condensing pressure, stream has saturation temperature 0f 100 degree Celsius and the latent heat of vaporization is 2160 k J/kg. Further, the steam is initially just saturated and the condensate leaves the exchanger without sub-cooling i.e. only latent heat of condensing steam is transferred to water. Take specific heat of water as 4 k J/kg K |
| A. | 0.224 |
| B. | 0.706 |
| C. | 2.224 |
| D. | 3.224 |
| Answer» C. 2.224 | |
| 41. |
The engine oil at 150 degree Celsius is cooled to 80 degree Celsius in a parallel flow heat exchanger by water entering at 25 degree Celsius and leaving at 60 degree Celsius. Estimate the exchanger effectiveness |
| A. | 0.56 |
| B. | 0.66 |
| C. | 0.76 |
| D. | 0.86 |
| Answer» B. 0.66 | |
| 42. |
Capacity ratio is defined as the product of |
| A. | Mass and temperature |
| B. | Mass and specific heat |
| C. | Specific heat and temperature |
| D. | Time and temperature |
| Answer» C. Specific heat and temperature | |
| 43. |
Which one is having lowest value of specific heat? |
| A. | Coal |
| B. | Clay |
| C. | Banana |
| D. | Concrete |
| Answer» E. | |
| 44. |
What is the value of specific heat for sand in J/kg K? |
| A. | 800 |
| B. | 700 |
| C. | 600 |
| D. | 500 |
| Answer» B. 700 | |
| 45. |
Which one is having highest value of overall heat transfer coefficient? |
| A. | Steam condensers |
| B. | Feed water heaters |
| C. | Alcohol condensers |
| D. | Steam |
| Answer» C. Alcohol condensers | |
| 46. |
What is the value of specific heat for cotton in J/kg K? |
| A. | 1600 |
| B. | 1500 |
| C. | 1400 |
| D. | 1300 |
| Answer» E. | |
| 47. |
What is the value of overall heat transfer coefficient ammonia condensers? |
| A. | 800-1400 W/m² K |
| B. | 200-750 W/m² K |
| C. | 250-2500 W/m² K |
| D. | 1500-1750 W/m² K |
| Answer» B. 200-750 W/m² K | |
| 48. |
What is the value of specific heat for asphalt in J/kg K? |
| A. | 920 |
| B. | 820 |
| C. | 720 |
| D. | 620 |
| Answer» B. 820 | |
| 49. |
Assumptions made for calculation of logarithmic mean temperature difference are(i) Constant overall heat transfer coefficient(ii) The kinetic and potential energy changes are negligible(iii) There is no conduction of heat along the tubes of heat exchangerIdentify the correct statements |
| A. | 1, 2 and 3 |
| B. | 1 and 3 |
| C. | 1 and 2 |
| D. | 2 and 3 |
| Answer» B. 1 and 3 | |
| 50. |
E – NTU method is particularly useful in thermal design of heat exchangers when |
| A. | Inlet temperature of the fluid streams are not known as a priori |
| B. | The outlet temperatures of the hot fluid streams is known but that of cold fluid stream is not known as a priori |
| C. | The outlet temperatures of the fluid streams is known as a priori |
| D. | The outlet temperatures of the fluid streams are not known as a priori |
| Answer» E. | |