MCQOPTIONS
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MCQOPTIONS
This section includes 8 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. |
Water pipes are to be buried underground in a wet soil (thermal diffusivity = 2.78 * 10 -3 m2/s) which is initially at 4.5 degree Celsius. The soil surface temperature suddenly drops to -5 degree Celsius and remains at this value for 10 hours. Calculate the minimum depth at which the pipe be laid if the surrounding soil temperature is to remain above 0 degree Celsius. The soil may be considered as semi-infinite solid |
| A. | 0.467 m |
| B. | 0.367 m |
| C. | 0.267 m |
| D. | 0.167 m |
| Answer» E. | |
| 2. |
Consider the above problem, find the temperature at the center of the slab one minute after the change in surface temperature |
| A. | 66 degree Celsius |
| B. | 76 degree Celsius |
| C. | 86 degree Celsius |
| D. | 96 degree Celsius |
| Answer» B. 76 degree Celsius | |
| 3. |
A mild steel plate 5 cm thick and initially at 40 degree Celsius temperature is suddenly exposed on one side to a fluid which causes the surface temperature to increase to and remain at 90 degree Celsius. Calculate maximum time that the slab be treated as a semi-infinitely body
|
| A. | 100 seconds |
| B. | 200 seconds |
| C. | 300 seconds |
| D. | 400 seconds |
| Answer» C. 300 seconds | |
| 4. |
A large steel ingot, which has been uniformly heated to 750 degree Celsius, is hardened by quenching it in an oil bath that is maintained at 25 degree Celsius. What length of time is required for the temperature to reach 600 degree Celsius at a depth of 1 cm? Thermal diffusivity for the steel ingot is 1.21 * 10 -5 m2/s. The ingot may be approximated as a flat plate |
| A. | 4.55 seconds |
| B. | 3.55 seconds |
| C. | 2.55 seconds |
| D. | 1.55 seconds |
| Answer» D. 1.55 seconds | |
| 5. |
At the penetration depth d, there will be 1% perturbation at a time given by |
| A. | 4 d <sup>2</sup>/13 |
| B. | 3 d <sup>2</sup>/13 |
| C. | 2 d <sup>2</sup>/13 |
| D. | d <sup>2</sup>/13 |
| Answer» E. | |
| 6. |
The temperature perturbation at all the surface has penetrated to the depth |
| A. | 1.6 ( T)<sup> 1/2</sup> |
| B. | 2.6 ( T)<sup> 1/2</sup> |
| C. | 3.6 ( T)<sup> 1/2</sup> |
| D. | 4.6 ( T)<sup> </sup> |
| Answer» D. 4.6 ( T)<sup> </sup> | |
| 7. |
The perturbation time varies as |
| A. | d <sup>2</sup>/ |
| B. | 2 d <sup>2</sup>/ |
| C. | 3 d <sup>2</sup>/ |
| D. | 4 d <sup>2</sup>/ |
| Answer» B. 2 d <sup>2</sup>/ | |
| 8. |
An infinite solid is one which extends itself infinitely in all directions of space . Identify the correct option |
| A. | True |
| B. | False |
| Answer» B. False | |