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.
| 51. |
A cold fluid (specific heat 2.95 k J/kg K) at 10 kg/min is to be heated from 25 degree Celsius to 55 degree Celsius in a heat exchanger. The task is accomplished by extracting heat from hot water (specific heat 4.186 k J /kg K) available at mass flow rate 5 kg/min and inlet temperature 85 degree Celsius. Identify the type of arrangement of the heat exchanger |
| A. | Concentric tubes |
| B. | Parallel flow |
| C. | Counter flow |
| D. | Shell and tubes |
| Answer» D. Shell and tubes | |
| 52. |
A cross flow type air heater has an area of 50 cm². The overall heat transfer coefficient is 100 W/m² K and heat capacity of both hot and cold stream is 1000 W/m K. The value of NTU is |
| A. | 1000 |
| B. | 500 |
| C. | 5 |
| D. | 0.2 |
| Answer» C. 5 | |
| 53. |
When two fluids of the heat exchanger are separated by a plane wall, the thermal resistance comprises(i) Convection resistance due to the fluid film at the inside surface(ii) Conduction resistance(iii) Convection resistance due to the fluid film at the outside surfaceIdentify the correct option |
| A. | 1 and 2 |
| B. | 1, 2 and 3 |
| C. | 2 and 3 |
| D. | 1 and 3 |
| Answer» C. 2 and 3 | |
| 54. |
In how many categories heat exchangers are classified on the basis of direction of flow of fluids? |
| A. | 4 categories |
| B. | 3 categories |
| C. | 2 categories |
| D. | 1 categories |
| Answer» C. 2 categories | |
| 55. |
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 counter flow arrangement? |
| A. | 2.758 m² |
| B. | 3.758 m² |
| C. | 4.758 m² |
| D. | 5.758 m² |
| Answer» C. 4.758 m² | |
| 56. |
A company is heating a gas by passing it through a pipe with steam condensing on the outside. What percentage change in length would be needed if it is proposed to triple the heating capacity? |
| A. | 200% |
| B. | 400% |
| C. | 600% |
| D. | 800% |
| Answer» B. 400% | |
| 57. |
What is the value of specific heat for coal in J/kg K? |
| A. | 1260 |
| B. | 1360 |
| C. | 1460 |
| D. | 1560 |
| Answer» B. 1360 | |
| 58. |
A heat exchanger to preheat oil for a furnace was designed without considering the possibility of scale formation, and the overall heat transfer coefficient based on the fuel oil side was 3200 k J/m² hr degree. What would be the corrected coefficient of heat transfer if a fouling factor of 0.00025 m² hr degree/k J for the fuel oil is taken into account? |
| A. | 1777.78 k J/m² hr degree |
| B. | 1666.78 k J/m² hr degree |
| C. | 1555.78 k J/m² hr degree |
| D. | 1444.78 k J/m² hr degree |
| Answer» B. 1666.78 k J/m² hr degree | |
| 59. |
Which of the following is not associated with heat exchanger? |
| A. | Fouling |
| B. | NTU |
| C. | Capacity ratio |
| D. | Mc Adam’s correction factor |
| Answer» E. | |
| 60. |
What is the value of fouling factor for industrial liquids? |
| A. | 0.0004 m² K/W |
| B. | 0.0003 m² K/W |
| C. | 0.0002 m² K/W |
| D. | 0.0001 m² K/W |
| Answer» D. 0.0001 m² K/W | |
| 61. |
Identify the correct expression for effectiveness |
| A. | 4 – exponential (- NTU) |
| B. | 3 – exponential (- NTU) |
| C. | 2 – exponential (- NTU) |
| D. | 1 – exponential (- NTU) |
| Answer» E. | |
| 62. |
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. Calculate the log mean temperature difference |
| A. | 28.25 degree Celsius |
| B. | 29.25 degree Celsius |
| C. | 30.25 degree Celsius |
| D. | 31.25 degree Celsius |
| Answer» B. 29.25 degree Celsius | |
| 63. |
The heat loss from unpainted aluminum side of a house has been calculated on the presumption that overall coefficient of heat transfer is 5 W/m² K. Later, it was discovered that the air pollution levels are such that fouling factor on this side is of the order of 0.0005 m² K/W. Find overall heat transfer coefficient of dirty side |
| A. | 2.9875 W/m² K |
| B. | 3.9875 W/m² K |
| C. | 4.9875 W/m² K |
| D. | 5.9875 W/m² K |
| Answer» D. 5.9875 W/m² K | |
| 64. |
In how many categories heat exchangers are classified on the basis of physical state of heat exchanging fluids? |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» C. 3 | |
| 65. |
The energy transfer between the hot fluid and cold fluids is brought about by their complete physical mixing in |
| A. | Direct contact heat exchanger |
| B. | Regenerators |
| C. | Recuperators |
| D. | Boilers |
| Answer» B. Regenerators | |
| 66. |
Which of the following is not an example of recuperators type heat exchanger? |
| A. | Automobile radiators |
| B. | Condensers |
| C. | Chemical factories |
| D. | Oil heaters for an aero plane |
| Answer» D. Oil heaters for an aero plane | |
| 67. |
Based upon the nature of heat exchange process, the heat exchangers are classified into how many categories |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» D. 4 | |
| 68. |
Heat exchangers are classified into how many categories? |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» E. | |
| 69. |
Some examples of heat exchanger are(i) Condensers and evaporators in refrigeration units(ii) Evaporator of an ice plant and milk chiller of a pasteurizing plant(iii) Automobile radiators and oil coolers of heat enginesIdentify the correct answer |
| A. | 1 only |
| B. | 2 and 3 |
| C. | 1, 2 and 3 |
| D. | 1 and 2 |
| Answer» D. 1 and 2 | |
| 70. |
The heat transfer from a hot body to a cold body is directly proportional to the surface area and difference of temperatures between the two bodies. This statement is called |
| A. | First law of thermodynamics |
| B. | Newton's law of cooling |
| C. | Newton's law of heating |
| D. | Stefan's law |
| Answer» C. Newton's law of heating | |
| 71. |
The use of heat exchangers is made in |
| A. | Radiators in automobile |
| B. | Condensers and boilers in steam plants |
| C. | Condensers and evaporators in refrigeration and air conditioning units |
| D. | All of the above |
| Answer» E. | |
| 72. |
The total radiation from a black body per second per unit area is ________ fourth power of the absolute temperature. This statement is known as Stefan Boltzmann law. |
| A. | Equal to |
| B. | Directly proportional to |
| C. | Inversely proportional to |
| D. | None of these |
| Answer» C. Inversely proportional to | |
| 73. |
Temperature of steam at around 540°C can be measured by |
| A. | Thermometer |
| B. | Thermistor |
| C. | Thermocouple |
| D. | None of these |
| Answer» D. None of these | |
| 74. |
Thermal diffusivity is |
| A. | A dimensionless parameter |
| B. | Function of temperature |
| C. | Used as mathematical model |
| D. | A physical property of the material |
| Answer» E. | |
| 75. |
Heat transfer takes place as per |
| A. | Zeroth law of thermodynamics |
| B. | First law of thermodynamic |
| C. | Second law of the thermodynamics |
| D. | Kirchoff's law |
| Answer» D. Kirchoff's law | |
| 76. |
The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit |
| A. | Temperature |
| B. | Thickness |
| C. | Area |
| D. | Time |
| Answer» E. | |
| 77. |
The time constant of a thermocouple is |
| A. | The time taken to attain the final temperature to be measured |
| B. | The time taken to attain 50% of the value of initial temperature difference |
| C. | The time taken to attain 63.2% of the value of initial temperature difference |
| D. | Determined by the time taken to reach 100°C from 0°C |
| Answer» D. Determined by the time taken to reach 100°C from 0°C | |
| 78. |
In heat transfer, conductance equals conductivity (kcal/hr/sq.m/°C/cm) divided by |
| A. | Hr (time) |
| B. | Sq. m (area) |
| C. | °C (temperature) |
| D. | K.cal (heat) |
| Answer» E. | |
| 79. |
The expression Q = ρ AT4 is called |
| A. | Fourier equation |
| B. | Stefan-Boltzmann equation |
| C. | Newton Reichmann equation |
| D. | Joseph-Stefan equation |
| Answer» C. Newton Reichmann equation | |
| 80. |
Depending on the radiating properties, body will be transparent when(Where a = absorptivity, p = reflectivity, x = transmissivity) |
| A. | P = 0, x = 0 and a = 1 |
| B. | P=1, x = 0, and a = 0 |
| C. | P = 0, x= 1, and a = 0 |
| D. | X = 0, a + p = 1 |
| Answer» D. X = 0, a + p = 1 | |
| 81. |
Depending on the radiating properties, a body will be white when(Where a = absorptivity, p = reflectivity, x = transmissivity) |
| A. | P = 0, x = 0 and a = 1 |
| B. | P=1, T = 0 and a = 0 |
| C. | P = 0, x = 1 and a = 0 |
| D. | X = 0, a + p = 1 |
| Answer» C. P = 0, x = 1 and a = 0 | |
| 82. |
The rate of heat flow through a body is Q = [kA (T₁ - T₂)]/x. The term x/kA is known as |
| A. | Thermal coefficient |
| B. | Thermal resistance |
| C. | Thermal conductivity |
| D. | None of these |
| Answer» C. Thermal conductivity | |
| 83. |
Depending on the radiating properties, a body will be black when(Where a = absorptivity, p = reflectivity, X = transmissivity.) |
| A. | P = 0, x = 0 and a = 1 |
| B. | P= 1, T = 0 and a = 0 |
| C. | P = 0, x = 1 and a = 0 |
| D. | X = 0, a + p = 0 |
| Answer» B. P= 1, T = 0 and a = 0 | |
| 84. |
Total emissivity of polished silver compared to black body is |
| A. | Same |
| B. | Higher |
| C. | More or less same |
| D. | Very much lower |
| Answer» E. | |
| 85. |
A composite slab has two layers of different materials with thermal conductivities k₁ and k₂. If each layer has the same thickness, then the equivalent thermal conductivity of the slab will be |
| A. | k₁ k₂ |
| B. | (k₁ + k₂) |
| C. | (k₁ + k₂)/ k₁ k₂ |
| D. | 2 k₁ k₂/ (k₁ + k₂) |
| Answer» E. | |
| 86. |
The product of Reynolds number and Prandtl number is known as |
| A. | Stanton number |
| B. | Biot number |
| C. | Peclet number |
| D. | Grashoff number |
| Answer» D. Grashoff number | |
| 87. |
The ratio of Nusselt number and the product of Reynold's number and Prandtl number is equal to |
| A. | Stanton number |
| B. | Biot number |
| C. | Peclet number |
| D. | Grashoff number |
| Answer» B. Biot number | |
| 88. |
A steam pipe is to be lined with two layers of insulating materials of different thermal conductivities. For the minimum heat transfer, |
| A. | The better insulation must be put inside |
| B. | The better insulation must be put outside |
| C. | One could place either insulation on either side |
| D. | One should take into account the steam temperature before deciding as to which insulation is put where |
| Answer» B. The better insulation must be put outside | |
| 89. |
A non-dimensional number generally associated with natural convection heat transfer is |
| A. | Grashoff number |
| B. | Nusselt number |
| C. | Weber number |
| D. | Prandtl number |
| Answer» B. Nusselt number | |
| 90. |
Stefan Boltzmann law is applicable for heat transfer by |
| A. | Conduction |
| B. | Convection |
| C. | Radiation |
| D. | Conduction and radiation combined |
| Answer» D. Conduction and radiation combined | |
| 91. |
When heat is transferred by molecular collision, it is referred to as heat transfer by |
| A. | Conduction |
| B. | Convection |
| C. | Radiation |
| D. | Scattering |
| Answer» C. Radiation | |
| 92. |
According to Prevost theory of heat exchange |
| A. | It is impossible to transfer heat from low temperature source to t high temperature source |
| B. | Heat transfer by radiation requires no medium |
| C. | All bodies above absolute zero emit radiation |
| D. | Heat transfer in most of the cases takes place by combination of conduction, convection and radiation |
| Answer» D. Heat transfer in most of the cases takes place by combination of conduction, convection and radiation | |
| 93. |
Which of the following has least value of conductivity? |
| A. | Glass |
| B. | Water |
| C. | Plastic |
| D. | Air |
| Answer» E. | |
| 94. |
According to Wien's law, the wavelength corresponding to maximum energy is proportion to |
| A. | Absolute temperature (T) |
| B. | I² |
| C. | F |
| D. | T |
| Answer» B. I² | |
| 95. |
The unit of Stefan-Boltzmann constant is |
| A. | Watt/mK |
| B. | Watt/m2K2 |
| C. | Watt/m2K4 |
| D. | Watt/mK2 |
| Answer» D. Watt/mK2 | |
| 96. |
The unit of Stefan Boltzmann constant is |
| A. | watt/cm3 °K |
| B. | watt/cm4 °K |
| C. | watt2/cm °K⁴ |
| D. | watt/cm2 °K⁴ |
| Answer» E. | |
| 97. |
When absorptivity (α) = 1, reflectivity (ρ) = 0 and transmissivity (τ) = 0, then the body is said to be a |
| A. | Black body |
| B. | Grey body |
| C. | Opaque body |
| D. | White body |
| Answer» B. Grey body | |
| 98. |
The energy distribution of an ideal reflector at higher temperatures is largely in the range of |
| A. | Shorter wavelength |
| B. | Longer wavelength |
| C. | Remain same at all wavelengths |
| D. | Wavelength has nothing to do with it |
| Answer» B. Longer wavelength | |
| 99. |
In counter flow heat exchangers |
| A. | Both the fluids at inlet (of heat exchanger where hot fluid enters) are in their coldest state |
| B. | Both the fluids at inlet are in their hottest state |
| C. | Both the fluids at exit are in their hottest state |
| D. | One fluid is in hottest state and other in coldest state at inlet |
| Answer» C. Both the fluids at exit are in their hottest state | |
| 100. |
According to Newton's law of cooling, the heat transfer from a hot body to a cold body is |
| A. | Directly proportional to the surface area |
| B. | Directly proportional to the difference of temperatures between the two bodies |
| C. | Either (A) or (B) |
| D. | Both (A) and (B) |
| Answer» E. | |