MCQOPTIONS
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MCQOPTIONS
This section includes 10 Mcqs, each offering curated multiple-choice questions to sharpen your Thermal Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
If qw =2500x where x is in m and in the direction of flow (x=0 at the inlet), the bulk mean temperature of the water leaving the pipe in C is ________ |
| A. | 71 |
| B. | 76 |
| C. | 79 |
| D. | 81 |
| Answer» E. | |
| 2. |
Water (Prandtl number 6) flows over a flat plate which is heated over the entire length. Which one of the following relationship between the hydrodynamic boundary layer thickness ( ) and the thermal boundary layer thickness ( )t is true? |
| A. | ( )t > |
| B. | ( )t < |
| C. | ( )t = |
| D. | Cannot be predicted |
| Answer» C. ( )t = | |
| 3. |
For a fluid with Prandtl number Pr>1, momentum boundary layer thickness? |
| A. | Decreases rapidly compared to the thermal boundary layer thickness |
| B. | And thermal boundary layer thickness increase at the same rate |
| C. | Increases rapidly as compared to thermal boundary layer thickness |
| D. | And thermal boundary layer thickness decrease at the same rate |
| Answer» D. And thermal boundary layer thickness decrease at the same rate | |
| 4. |
In laminar developing flow through a pipe with constant wall temperature, the magnitude of the pipe wall inner surface convective heat transfer coefficient shall be maximum at the: |
| A. | Middle length of flow |
| B. | Beginning of flow |
| C. | End of flow |
| D. | One third of the length of flow |
| Answer» E. | |
| 5. |
The characteristic length for computing Grashoff number of horizontal cylinder is ___________ |
| A. | The length of the cylinder |
| B. | The diameter of the cylinder |
| C. | The perimeter of the cylinder |
| D. | The radius of the cylinder |
| Answer» C. The perimeter of the cylinder | |
| 6. |
The laminar boundary layer occurs when a cold fluid over a hot plate. In which of the following positions, the temperature gradient assumes zero value? |
| A. | At bottom of boundary layer |
| B. | In mid free stream of fluid |
| C. | At top of boundary layer |
| D. | At the junction of laminar and turbulent boundary layer |
| Answer» D. At the junction of laminar and turbulent boundary layer | |
| 7. |
Which non-dimensional numbers relates the thermal boundary layer and hydrodynamic boundary layer? |
| A. | Rayleigh number |
| B. | Peclet number |
| C. | Grashoff number |
| D. | Prandtl number |
| Answer» E. | |
| 8. |
Which of the following non-dimensional numbers is used for transition from laminar flow to turbulent flow in the free convection? |
| A. | Reynolds number |
| B. | Grashoff number |
| C. | Peclet number |
| D. | Rayleigh number |
| Answer» C. Peclet number | |
| 9. |
Nusselt number for fully developed turbulent flow in a pipe is given by Nu=C Rea Prb. the values of a and b are? |
| A. | a=0.5 and b=0.33 for heating and cooling |
| B. | a=0.5 and b=0.4 for heating and b=0.3 for cooling |
| C. | a=0.8 and b=0.4 for heating and b=0.3 for cooling |
| D. | a=0.8 and b=0.3 for heating and b=0.4 for cooling |
| Answer» D. a=0.8 and b=0.3 for heating and b=0.4 for cooling | |
| 10. |
Hot air at 50 C. If the forced heat transfer convection is 75 W/m2K, the heat gain rate gain rate by the plate through an area of 2m2 will be _____ |
| A. | 15KW |
| B. | 22.5KJ/sec |
| C. | 7.5KJ/sec |
| D. | 25KJ/sec |
| Answer» B. 22.5KJ/sec | |