MCQOPTIONS
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MCQOPTIONS
This section includes 12 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. |
A fin will be necessary and effective only when _____ |
| A. | k is small and h is large |
| B. | k is large and h is also large |
| C. | k is small and h is also small |
| D. | k is large and h is small |
| Answer» E. | |
| 2. |
Which one of the following configuration has the highest fin effectiveness? |
| A. | Thin, closely spaced fins |
| B. | Thin, widely spaced fins |
| C. | Thick, widely spaced fins |
| D. | Thick, closely spaced fins |
| Answer» B. Thin, widely spaced fins | |
| 3. |
An increase in pin fin effectiveness is caused by high value of _________ |
| A. | Convective coefficient |
| B. | Change in temperature |
| C. | Thermal conductivity |
| D. | Sectional Area |
| Answer» D. Sectional Area | |
| 4. |
Three fins of equal length and diameter but made of aluminum, brass and cast iron are heated to 2000C at one end. If the fins dissipate heat to the surrounding air is 250C the temperature at the end will be least in case of ______ |
| A. | Aluminum fin |
| B. | Brass fin |
| C. | Cast-iron fin |
| D. | Each fin have the same temperature at the free end |
| Answer» D. Each fin have the same temperature at the free end | |
| 5. |
Extended surface are used to increase the rate of heat transfer. When the convective heat transfer coefficient h=mk, the addition of extended surface will: |
| A. | Increase the rate of heat transfer |
| B. | Decrease the rate of heat transfer |
| C. | Not increase the rate of heat transfer |
| D. | Increase the rate of heat transfer when the length of the fin is very large |
| Answer» D. Increase the rate of heat transfer when the length of the fin is very large | |
| 6. |
On heat transfer surface, fins are provided? |
| A. | To increase temperature gradient so as to enhance heat transfer |
| B. | To increase turbulence in flow for enhancing |
| C. | To increase surface area to promote the rate of heat transfer |
| D. | To decrease the pressure drop of the fluid |
| Answer» D. To decrease the pressure drop of the fluid | |
| 7. |
A fin length l, protrudes from a surface held at temperature T0; it being higher than the ambient temperature Ta. The heat dissipation from the free end of the fin is stated to be negligibly small. What is the temperature gradient (dT/dx)x=l at the tip of the fin? |
| A. | Zero |
| B. | (T<sub>0</sub>-T<sub>l</sub>)/l |
| C. | h(T<sub>0</sub>-T<sub>a</sub>) |
| D. | (T<sub>l</sub>-T<sub>a</sub>)/(T<sub>0</sub>-T<sub>a</sub>) |
| Answer» B. (T<sub>0</sub>-T<sub>l</sub>)/l | |
| 8. |
The insulated tip temperature of a rectangular longitudinal fin having an excess (over ambient) root temperature of 0is _____ |
| A. | <sub>0</sub>tanh(ml) |
| B. | <sub>0</sub>/sinh(ml) |
| C. | <sub>0</sub> tanh(ml)/(ml) |
| D. | <sub>0</sub>/cosh(ml) |
| Answer» E. | |
| 9. |
Addition of fin to the surface increases the heat transfer if ( sqrt{hA/kP} ) is __________ |
| A. | Equal to one |
| B. | Greater than one |
| C. | Less than one |
| D. | Greater than one but less than two |
| Answer» D. Greater than one but less than two | |
| 10. |
Which the following statements pertaining to heat transfer through fins? |
| A. | Fins are equally effective irrespective of whether they are on the hot side or cold side of the fluid |
| B. | The temperature along the fin is variable and hence the rate of heat transfer varies along the elements of the fin |
| C. | The fins may be made of materials that have a lower conductivity than the material of the wall |
| D. | Fins must be arranged at right angles to the direction of the flow of the working fluid |
| Answer» C. The fins may be made of materials that have a lower conductivity than the material of the wall | |
| 11. |
Heat pipe is widely used nowadays because _________ |
| A. | It acts as an insulator |
| B. | It acts as conductor and insulator |
| C. | It acts as a superconductor |
| D. | It acts as a fin |
| Answer» D. It acts as a fin | |
| 12. |
A finned surface consists of root or base area of 1m2 and fin surface area of 2m2. The average heat transfer coefficient for finned surface is 20W/m2K effectiveness of fins provided is 0.75. If finned surface with surface with root or base temperature of 50 C is transferring heat to fluid of 30 C, then the rate of heat transfer without using fin is _______ |
| A. | 400W |
| B. | 800W |
| C. | 1000W |
| D. | 1200W |
| Answer» C. 1000W | |