MCQOPTIONS
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MCQOPTIONS
This section includes 30 Mcqs, each offering curated multiple-choice questions to sharpen your Heat Transfer knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
A solid sphere of 8 cm radius has a uniform heat generation of 4000000 W/m³. The outside surface is exposed to a fluid at 150 degree Celsius with convective heat transfer coefficient of 750 W/m² K. If thermal conductivity of the solid material is 30 W/m K, determine maximum temperature |
| A. | 444.45 degree Celsius |
| B. | 434.45 degree Celsius |
| C. | 424.45 degree Celsius |
| D. | 414.45 degree Celsius |
| Answer» C. 424.45 degree Celsius | |
| 2. |
An 8 cm diameter orange, approximately spherical in shape, undergoes ripening process and generates 18000 k J/m³ hr of energy. If external surface of the orange is at 6.5 degree Celsius, find out the temperature at the center of the orange. Take thermal conductivity = 0.8 k J/ m hr degree for the orange material |
| A. | 13.5 degree Celsius |
| B. | 12.5 degree Celsius |
| C. | 11.5 degree Celsius |
| D. | 10.5 degree Celsius |
| Answer» C. 11.5 degree Celsius | |
| 3. |
Identify the correct boundary condition for a hollow sphere with inside surface insulated. |
| A. | At r = r 1, the conduction region is perfectly insulated |
| B. | At r = r 1, the conduction region is partially insulated |
| C. | Heat flow is infinity |
| D. | Heat flow is negative |
| Answer» B. At r = r 1, the conduction region is partially insulated | |
| 4. |
A hollow sphere (k = 30 W/m K) of inner radius 6 cm and outside radius 8 cm has a heat generation rate of 4000000 W/m³. The inside surface is insulated and heat is removed by convection over the outside surface by a fluid at 100 degree Celsius with surface conductance 300 W/m² K. Make calculations for the temperature at the outside surfaces of the sphere |
| A. | 105.6 degree Celsius |
| B. | 205.6 degree Celsius |
| C. | 305.6 degree Celsius |
| D. | 405.6 degree Celsius |
| Answer» D. 405.6 degree Celsius | |
| 5. |
A composite slab consists of 5 cm thick layer of steel (k = 146 kJ/m hr degree) on the left side and a 6 cm thick layer of brass (k = 276 kJ/m hr degree) on the right hand side. The outer surfaces of the steel and brass are maintained at 100 degree Celsius and 50 degree Celsius. The contact between the two slabs is perfect and heat is generated at the rate of 4.2 * 10⁵ k J/m² hr at the plane of contact. The heat thus generated is dissipated from both sides of composite slab for steady state conditions. Calculate the temperature at the interface |
| A. | 115.26 degree celsius |
| B. | 125.26 degree celsius |
| C. | 135.26 degree celsius |
| D. | 145.26 degree celsius |
| Answer» C. 135.26 degree celsius | |
| 6. |
Consider a slab of thickness δ with one side (x = 0) insulated and other side (x = δ) maintained at constant temperature. The rate of uniform heat generation within the slab is q g W/m³. Presuming that the heat conduction is in steady state and one dimensional along x direction, the maximum temperature in the slab would occur at x equal |
| A. | δ/2 |
| B. | Zero |
| C. | δ/4 |
| D. | δ |
| Answer» C. δ/4 | |
| 7. |
There occurs heat conduction and internal heat generation at uniform rate within the conduction medium itself in the following cases(i) Drying of concrete(ii) Chemical processes(iii) Fuel elements in a nuclear reactionChoose the correct option |
| A. | 1 only |
| B. | 2 only |
| C. | 1 and 3 |
| D. | 1, 2 and 3 |
| Answer» E. | |
| 8. |
In case when both the surfaces of plane wall are at different temperature, we get an expression i.e.T MAX – T W2 /T W1 – TW2 = (B + 1)²/4BWhat is the value of B? |
| A. | (q g) (δ)²/2k (T W1 – TW2) |
| B. | (q g) (δ)³/3k (T W1 – TW2) |
| C. | (q g) (δ)⁴/4k (T W1 – TW2) |
| D. | (q g) (δ)⁵/5k (T W1 – TW2) |
| Answer» B. (q g) (δ)³/3k (T W1 – TW2) | |
| 9. |
Suppose heat is conducted due to electronsWhere, i = I/A and p is the resistivity, then |
| A. | q g = 2i² p |
| B. | q g = 3i² p |
| C. | q g = i² p |
| D. | q g = 4i² p |
| Answer» D. q g = 4i² p | |
| 10. |
Which one of the following materials are quickly heated by applying high frequency? |
| A. | Textiles |
| B. | Engines |
| C. | Rubber |
| D. | Coal |
| Answer» B. Engines | |
| 11. |
The insulating material used in dielectric heating is |
| A. | Coal |
| B. | Silver |
| C. | Coin |
| D. | Wool |
| Answer» E. | |
| 12. |
Consider a 1.2 m thick slab of poured concrete (k = 1.148 W/m degree) with both of side surfaces maintained at a temperature of 20 degree Celsius. During its curing, chemical energy is released at the rate of 80 W/m³. Workout the maximum temperature of concrete |
| A. | 30.73 degree celsius |
| B. | 29.73 degree celsius |
| C. | 28.73 degree celsius |
| D. | 27.73 degree celsius |
| Answer» C. 28.73 degree celsius | |
| 13. |
Unit of specific resistance is |
| A. | Ohm mm²/m |
| B. | Ohm mm |
| C. | Ohm/m |
| D. | Ohm mm/m |
| Answer» B. Ohm mm | |
| 14. |
What maximum thickness of concrete can be poured without causing the temperature gradient to exceed 98.5 degree Celsius per meter anywhere in the slab? Consider a 1.2 m thick slab of poured concrete (k = 1.148 W/m degree) with both of side surfaces maintained at a temperature of 20 degree Celsius. During its curing, chemical energy is released at the rate of 80 W/m³. Workout the maximum temperature of concrete |
| A. | 2.64 m |
| B. | 3.64 m |
| C. | 4.64 m |
| D. | 5.64 m |
| Answer» C. 4.64 m | |
| 15. |
Generally heat generated depends on some parameters. It is directly proportional to |
| A. | Time |
| B. | Conductivity |
| C. | Voltage |
| D. | Distance between plates |
| Answer» D. Distance between plates | |
| 16. |
Dielectric heating apparatus consists of |
| A. | 4 electrodes |
| B. | Elemental strip |
| C. | No Insulating material |
| D. | 4 plates |
| Answer» C. No Insulating material | |
| 17. |
A 25 mm diameter egg roll (k = 1 W/m degree) is roasted with the help of microwave heating. For good quality roasting, it is desired that temperature at the center of roll is maintained at 100 degree Celsius when the surrounding temperature is 25 degree Celsius. What should be the heating capacity in W/m³ of the microwave if the heat transfer coefficient on the surface of egg roll is 20 W/m² degree? |
| A. | 113.31 k W/m³ |
| B. | 213.31 k W/m³ |
| C. | 313.31 k W/m³ |
| D. | 413.31 k W/m³ |
| Answer» C. 313.31 k W/m³ | |
| 18. |
The constants of integration are to be determined from the relevant boundary conditions which are(i) t = t w at r = R(ii) q g (π L R²) = -k (2 π R L) (d t/d r)(iii) Increasing temperature gradientChoose the correct option? |
| A. | Only i |
| B. | Only ii |
| C. | i and iii |
| D. | i and ii |
| Answer» E. | |
| 19. |
A concrete column used in bridge construction is cylindrical in shape with a diameter of 1 meter. The column is completely poured in a short interval of time and the hydration of concrete results in the equivalent of a uniform source strength of 0.7 W/kg. Determine the temperature at the center of the cylinder at a time when the outside surface temperature is 75 degree Celsius. The column is sufficiently long so that temperature variation along its length may be neglected. For concreteAverage thermal conductivity = 0.95 W/m KAverage density = 2300 kg/m³ |
| A. | 190.92 degree Celsius |
| B. | 180.92 degree Celsius |
| C. | 170.92 degree Celsius |
| D. | 160.92 degree Celsius |
| Answer» C. 170.92 degree Celsius | |
| 20. |
A slab of insulating material of thickness 6 cm and thermal conductivity 1.4kJ/m hr deg is placed between and is in contact with two parallel electrodes, and is then subjected to high frequency dielectric heating at a uniform rate of 140,000kJ/m³ hr. At steady state coefficients of combined radiation and convection are 42 and 48 kJ/m² hr deg. If atmospheric temperature is 25 degree Celsius, find surface temperatures? |
| A. | 144.10 degree Celsius and 134.47 degree Celsius |
| B. | 123.50 degree Celsius and 154.34 degree Celsius |
| C. | 121.60 degree Celsius and 115.45 degree Celsius |
| D. | 165.40 degree Celsius and 165.45 degree Celsius |
| Answer» D. 165.40 degree Celsius and 165.45 degree Celsius | |
| 21. |
A slab of 12 cm thickness and generating heat uniformly at 10⁶ W/m³ has thermal conductivity of 200 W/m degree. Both surfaces of the slab are maintained at 150 degree Celsius. Determine the heat flow rate at the quarter planes |
| A. | 30000 W/m² |
| B. | 40000 W/m² |
| C. | 50000 W/m² |
| D. | 60000 W/m² |
| Answer» B. 40000 W/m² | |
| 22. |
For a cylindrical rod with uniformly distributed heat sources, the thermal gradient at half the radius location will be |
| A. | Four times |
| B. | Twice |
| C. | One fourth |
| D. | One half |
| Answer» E. | |
| 23. |
Consider a convective heat flow to water at 75 degree Celsius from a cylindrical nuclear reactor fuel rod of 50 mm diameter. The rate of heat generation is 50000000 W/m³ and convective heat transfer coefficient is I kW/m² K. The outer surface temperature of the fuel element would be |
| A. | 625 degree Celsius |
| B. | 700 degree Celsius |
| C. | 550 degree Celsius |
| D. | 400 degree Celsius |
| Answer» C. 550 degree Celsius | |
| 24. |
Consider heat conduction through a solid sphere of radius R. There are certain assumptions(i) Unsteady state conditions(ii) One-dimensional radial conduction(iii) Constant thermal conductivityIdentify the correct statements |
| A. | i and iii |
| B. | ii and iii |
| C. | i, ii and iii |
| D. | i and ii |
| Answer» C. i, ii and iii | |
| 25. |
The temperature distribution profile for a solid cylinder is |
| A. | Parabolic |
| B. | Linear |
| C. | Ellipse |
| D. | Hyperbolic |
| Answer» B. Linear | |
| 26. |
If Q X is heat generated in at distance ‘x’, then heat conducted out at a distance (x + d x) will be |
| A. | Q X + 3d (Q X) d x /d x |
| B. | 2Q X + d (Q X) d x /d x |
| C. | d (Q X) d x /d x |
| D. | Q X + d (Q X) d x /d x |
| Answer» E. | |
| 27. |
In case of heat conduction through plane wall, which one of the following is not a correct assumption? |
| A. | Steady state |
| B. | Three dimensional heat flow |
| C. | Volumetric heat generation must be constant |
| D. | K must be constant |
| Answer» C. Volumetric heat generation must be constant | |
| 28. |
For a plane wall of thickness l with uniformly distributed heat generation q g per unit volume, the temperature t₀ at mid plane is given by |
| A. | t₀ = q g l²/2k +t w |
| B. | t₀ = q g l²/4k +t w |
| C. | t₀ = q g l²/8k +t w |
| D. | t₀ = q g l²/16k +t w |
| Answer» D. t₀ = q g l²/16k +t w | |
| 29. |
Notable example of uniform generation of heat within the conducting medium are(i) Energy of a nuclear reactor(ii) Liberation of energy due to some exothermic chemical reactions(iii) Resistance heating in electrical appliancesWhich of the statements made above are correct? |
| A. | 1, 2 and 3 |
| B. | 1 and 2 |
| C. | 1 and 3 |
| D. | Only 2 |
| Answer» B. 1 and 2 | |
| 30. |
The temperature drop in a plane wall with uniformly distributed heat generation can be decreased by reducing |
| A. | Wall thickness |
| B. | Heat generation rate |
| C. | Thermal conductivity |
| D. | Surface area |
| Answer» B. Heat generation rate | |