MCQOPTIONS
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MCQOPTIONS
This section includes 12 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 mercury thermometer with bulb idealized as a sphere of 1 mm radius is used for measuring the temperature of fluid whose temperature is varying at a fast rate. For mercury If the time for the temperature change of the fluid is 3 second, what should be the radius of thermocouple to read the temperature of the fluid?For the thermocouple materialk = 100 W/m Kα = 0.0012 m2/sh = 18 W/m2 K |
| A. | .864 mm |
| B. | .764 mm |
| C. | .664 mm |
| D. | .564 mmView Answer |
| Answer» B. .764 mm | |
| 2. |
An iron billet (k = 65 W/m K) measuring 20 * 15 * 80 cm is exposed to a convective flow resulting in convection coefficient of 11.5 W/m2 K. Determine the Biot number |
| A. | 0.02376 |
| B. | 0.008974 |
| C. | 0.004563 |
| D. | 0.006846 |
| Answer» E. | |
| 3. |
“Thermal radiation suffers no attenuation in a vacuum”. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 4. |
A low value of time constant can be achieved for a thermocouple by(i) Increasing the wire diameter(ii) Increasing the value heat transfer coefficient(iii) Use light metals of low density and low specific heat |
| A. | ii and iii |
| B. | i and iii |
| C. | i and ii |
| D. | i, ii and iii |
| Answer» B. i and iii | |
| 5. |
A thermocouple junction of spherical form is to be used to measure the temperature of the gas stream. The junction is at 20 degree Celsius and is placed in a gas stream which is at 200 degree Celsius. Make calculations for junction diameter needed for the thermocouple to have thermal time constant of one second. Assume the thermos-physical properties as given belowk = 20 W/ m Kh = 350 W/m2 Kc = 0.4 k J/kg Kp = 8000 kg/m3 |
| A. | 0.556 mm |
| B. | 0.656 mm |
| C. | 0.756 mm |
| D. | 0.856 mm |
| Answer» C. 0.756 mm | |
| 6. |
An iron billet (k = 65 W/m K) measuring 20 * 15 * 80 cm is exposed to a convective flow resulting in convection coefficient of 11.5 W/m2 K. Determine the Biot numbe? |
| A. | 0.02376 |
| B. | 0.008974 |
| C. | 0.004563 |
| D. | 0.006846 |
| Answer» E. | |
| 7. |
The lumped parameter solution for transient conduction can be conveniently stated as |
| A. | t – t <sub>a</sub>/t<sub> I</sub> – t<sub> a</sub> = 2 exponential (- B <sub>I</sub> F<sub> 0</sub>) |
| B. | t – t <sub>a</sub>/t<sub> I</sub> – t<sub> a</sub> = exponential (- B <sub>I</sub> F<sub> 0</sub>) |
| C. | t – t <sub>a</sub>/t<sub> I</sub> – t<sub> a</sub> = 3 exponential (- B <sub>I</sub> F<sub> 0</sub>) |
| D. | t – t <sub>a</sub>/t<sub> I</sub> – t<sub> a</sub> = 6 exponential (- B <sub>I</sub> F<sub> 0</sub>) |
| Answer» C. t ‚Äö√Ñ√∂‚àö√ë‚àö¬® t <sub>a</sub>/t<sub> I</sub> ‚Äö√Ñ√∂‚àö√ë‚àö¬® t<sub> a</sub> = 3 exponential (- B <sub>I</sub> F<sub> 0</sub>) | |
| 8. |
How does the body temperature falls or rises with time? |
| A. | Logarithmic |
| B. | Parabolic |
| C. | Linear |
| D. | Exponentially |
| Answer» E. | |
| 9. |
“Thermal radiation suffers no attenuation in a vacuum”.$ |
| A. | True |
| B. | False |
| Answer» B. False | |
| 10. |
Which of the following has units of time constant? (Where, P is density, A is area, c is specific heat and V is volume) |
| A. | p V/h A |
| B. | p c/h A |
| C. | p V c/h A |
| D. | V c/h A |
| Answer» D. V c/h A | |
| 11. |
A low value of time constant can be achieved for a thermocouple by |
| A. | Increasing the wire diameter |
| B. | Increasing the value heat transfer coefficient |
| C. | Use light metals of low density and low specific heat |
| D. | ii and iii |
| Answer» B. Increasing the value heat transfer coefficient | |
| 12. |
The time constant of a thermocouple is the time taken to |
| A. | Minimum time taken to record a temperature reading |
| B. | Attain 50% of initial temperature difference |
| C. | Attain the final value to be measured |
| D. | Attain 63.2% of the value of the initial temperature difference |
| Answer» E. | |