MCQOPTIONS
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MCQOPTIONS
This section includes 14 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 1.0 mm diameter and 300 mm long nickel wire is submerged horizontal in water at atmospheric pressure. At burnout, the wire has a current of 195 A. Calculate the voltage at burnout. The relevant thermos-physical properties arep f (fluid) = 959.52 kg/m3p g (vapor) = 0.597 kg/m3h f g = 2257000 J/kgσ = 0.0533 N/m |
| A. | 6.15 V |
| B. | 7.15 V |
| C. | 8.15 V |
| D. | = 959.52 kg/m3p g (vapor) = 0.597 kg/m3h f g = 2257000 J/kgσ = 0.0533 N/ma) 6.15 Vb) 7.15 Vc) 8.15 Vd) 9.15 V |
| Answer» C. 8.15 V | |
| 2. |
Estimate the peak heat flux for water boiling at normal atmospheric pressure. The relevant thermo-physical properties arep f (liquid) = 958.45 kg/m3p g (vapor) = 0.61 kg/m3h f g = 2.25 * 10 6 J/kgσ = 0.0585 N/m |
| A. | 1.53 * 10 8 W/m2 |
| B. | 1.53 * 10 7 W/m2 |
| C. | 1.53 * 10 6 W/m2 |
| D. | = 958.45 kg/m3p g (vapor) = 0.61 kg/m3h f g = 2.25 * 10 6 J/kgσ = 0.0585 N/ma) 1.53 * 10 8 W/m2b) 1.53 * 10 7 W/m2c) 1.53 * 10 6 W/m2d) 1.53 * 10 5 W/m2 |
| Answer» D. = 958.45 kg/m3p g (vapor) = 0.61 kg/m3h f g = 2.25 * 10 6 J/kgσ = 0.0585 N/ma) 1.53 * 10 8 W/m2b) 1.53 * 10 7 W/m2c) 1.53 * 10 6 W/m2d) 1.53 * 10 5 W/m2 | |
| 3. |
Natural convection heat transfer coefficients over surface of a vertical pipe and a vertical flat plate for same height. What is/are the possible reasons for this?(i) Same height(ii) Both vertical(iii) Same fluid(iv) Same fluid flow patternSelect the correct answer |
| A. | iv |
| B. | i and ii |
| C. | i |
| D. | iii and iv |
| Answer» E. | |
| 4. |
A 0.10 cm diameter and 15 cm long wire has been laid horizontally and submerged in water at atmospheric pressure. The wire has a steady state voltage drop of 14.5 V and a current of 42.5 A. Determine the heat flux of the wire.The following equation applies for water boiling on a horizontal submerged surfaceH = 1.54 (Q/A) 0.75 = 5.58 (d t) 3 W/m2 K where Q/A is the heat flux rate in W/m2 and d t is the temperature difference between surface and saturation |
| A. | 0.75 = 5.58 (d t) 3 W/m2 K where Q/A is the heat flux rate in W/m2 and d t is the temperature difference between surface and saturationa) 1.308 * 10 8 W/m2 |
| B. | 1.308 * 10 7 W/m2 |
| C. | 1.308 * 10 6 W/m2 |
| D. | 1.308 * 10 5 W/m2 |
| Answer» D. 1.308 * 10 5 W/m2 | |
| 5. |
Fritz criterion is given bya) h = 1.973 (Q/A) 0.45b) h = 1.973 (Q/A) 0.55c) h = 1.973 (Q/A) 0.65d) h = 1.973 (Q/ |
| A. | h = 1.973 (Q/A) 0.45 |
| B. | h = 1.973 (Q/A) 0.55 |
| C. | h = 1.973 (Q/A) 0.65 |
| D. | h = 1.973 (Q/A) 0.75 |
| Answer» E. | |
| 6. |
A_1.0_mm_diameter_and_300_mm_long_nickel_wire_is_submerged_horizontal_in_water_at_atmospheric_pressure._At_burnout,_the_wire_has_a_current_of_195_A._Calculate_the_voltage_at_burnout._The_relevant_thermos-physical_properties_are$ |
| A. | = 959.52 kg/m<sup>3</sup> |
| B. | = 0.597 kg/m<sup>3</sup> |
| Answer» C. | |
| 7. |
Identify the wrong statement with respect to boiling heat transfer? |
| A. | The steam boilers employing natural convection have steam raised through pool boiling |
| B. | Boiling occurs when a heated surface is exposed to a liquid and maintained at a temperature lower than the saturation temperature of the liquid |
| C. | Leiden-frost effect refers to the phenomenon of stable film boiling |
| D. | The nucleation boiling is characterized by the formation of bubbles at the nucleation sites and the resulting liquid agitation |
| Answer» C. Leiden-frost effect refers to the phenomenon of stable film boiling | |
| 8. |
In nucleate pool boiling, the heat flux depends on |
| A. | Liquid properties, material and condition of the surface |
| B. | Material of the surface only |
| C. | Material and roughness of the surface |
| D. | Liquid properties and material of the surface |
| Answer» B. Material of the surface only | |
| 9. |
The heat flux in nucleate boiling varies in accordance with |
| A. | h <sub>f g</sub> |
| B. | (h <sub>f g</sub>)<sup> 0.5</sup> |
| C. | 1/(h <sub>f g</sub>) <sup>2</sup> |
| D. | (h <sub>f g</sub>)<sup> 3</sup> |
| Answer» D. (h <sub>f g</sub>)<sup> 3</sup> | |
| 10. |
Natural convection heat transfer coefficients over surface of a vertical pipe and a vertical flat plate for same height. What is/are the possible reasons for this? |
| A. | Same height |
| B. | Both vertical |
| C. | Same fluid |
| D. | Same fluid flow pattern |
| Answer» E. | |
| 11. |
Consider the above problem, find the excess temperature of the wire |
| A. | 18.01 degree Celsius |
| B. | 19.01 degree Celsius |
| C. | 20.01 degree Celsius |
| D. | 21.01 degree Celsius |
| Answer» C. 20.01 degree Celsius | |
| 12. |
A 0.10 cm diameter and 15 cm long wire has been laid horizontally and submerged in water at atmospheric pressure. The wire has a steady state voltage drop of 14.5 V and a current of 42.5 A. Determine the heat flux of the wire. |
| A. | |
| B. | <sup>0.75</sup> = 5.58 (d t)<sup> 3</sup> W/m<sup>2 </sup>K where Q/A is the heat flux rate in W/m<sup>2</sup> and d t is the temperature difference between surface and saturation |
| C. | 1.308 * 10 <sup>8 </sup>W/m<sup>2</sup> |
| Answer» D. | |
| 13. |
Fritz criterion is given by |
| A. | h = 1.973 (Q/A) <sup>0.45</sup> |
| B. | h = 1.973 (Q/A) <sup>0.55</sup> |
| C. | h = 1.973 (Q/A) <sup>0.65</sup> |
| D. | h = 1.973 (Q/A) <sup>0.75</sup> |
| Answer» E. | |
| 14. |
When evaporation takes place at the liquid-vapor interface, the heat transfer is solely due to free convection and the film coefficient follows the relation |
| A. | Nu = f <sub>1</sub> (G r) f<sub> 2 </sub>(P r) |
| B. | Nu = 2 f <sub>1</sub> (G r) f<sub> 2 </sub>(P r) |
| C. | Nu = 3 f <sub>1</sub> (G r) f<sub> 2 </sub>(P r) |
| D. | Nu = 4 f <sub>1</sub> (G r) f<sub> 2 </sub>(P r) |
| Answer» B. Nu = 2 f <sub>1</sub> (G r) f<sub> 2 </sub>(P r) | |