MCQOPTIONS
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MCQOPTIONS
This section includes 75 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. |
Which one is true regarding parabolic fin? |
| A. | It dissipates the minimum amount of heat at minimum material cost |
| B. | It dissipates the minimum amount of heat at maximum material cost |
| C. | It dissipates the maximum amount of heat at maximum material cost |
| D. | It dissipates the maximum amount of heat at minimum material cost |
| Answer» E. | |
| 2. |
For what purpose we use thermometric well? |
| A. | To measure current |
| B. | To measure resistance |
| C. | To measure temperature of gas |
| D. | To stop heat dissipation |
| Answer» D. To stop heat dissipation | |
| 3. |
Which fin yields the maximum heat flow per unit weight? |
| A. | Straight triangular fin |
| B. | Curved triangular fin |
| C. | Parabolic fin |
| D. | Hyperbolic fin |
| Answer» B. Curved triangular fin | |
| 4. |
A heating unit is made in the form of a vertical tube of 50 mm outside diameter and 1.2 m height. The tube is fitted with 20 steel fins of rectangular section with height 40 mm and thickness 2.5 mm. The temperature at the base of fin is 75 degree Celsius, the surrounding air temperature is 20 degree Celsius and the heat transfer coefficient between the fin as well as the tube surface and the surrounding air is 9.5 W/m² K. If thermal conductivity of the fin material is 55 W/m K, find the amount of heat transferred from the tube without fin |
| A. | 98.44 W |
| B. | 88.44 W |
| C. | 78.44 W |
| D. | 68.44 W |
| Answer» B. 88.44 W | |
| 5. |
Suppose there are two reservoirs A and B. Let TA and TB be the temperatures of respective reservoirs. At any instant say TA = TB. In this case maximum temperature occurs at |
| A. | Middle |
| B. | Left |
| C. | Right |
| D. | All over the rod |
| Answer» B. Left | |
| 6. |
Heat dissipation by every segment of the fin is |
| A. | Sometimes same |
| B. | Same |
| C. | Not same |
| D. | Sometimes same or sometimes not same |
| Answer» D. Sometimes same or sometimes not same | |
| 7. |
“If a fin of a constant cross section is used, there would be wastage of material”. Chose the correct option. |
| A. | True |
| B. | False |
| C. | May be |
| D. | Can't say |
| Answer» B. False | |
| 8. |
“The diameter of well does not have any effect on temperature measurement by the thermometer”. Choose the correct option |
| A. | True |
| B. | False |
| C. | May be |
| D. | Can't say |
| Answer» B. False | |
| 9. |
For parabolic fin, the curve follows which law? |
| A. | y = C/x^2 |
| B. | y = C x^4 |
| C. | y = C x^2 |
| D. | y = C x^(1/2) |
| Answer» D. y = C x^(1/2) | |
| 10. |
If heat conducted into the element at plane x is Q X = – k A C (d t/d x) X. Then heat conducted out of the element at plane (x + d x) is |
| A. | – 2k A C d/d x (t + d t/d x (d x)) |
| B. | – k A C d/d x (t + d t/d x (d x)) |
| C. | – 3k A C d/d x (t + d t/d x (d x)) |
| D. | – 4k A C d/d x (t + d t/d x (d x)) |
| Answer» C. – 3k A C d/d x (t + d t/d x (d x)) | |
| 11. |
The heat dissipation at any section of parabolic fin is given by |
| A. | (t2 – t1) (b) (δ) |
| B. | k (t2 – t1) (b) (δ) |
| C. | k (t2 – t1) (δ) |
| D. | k (t2 – t1) (b) |
| Answer» C. k (t2 – t1) (δ) | |
| 12. |
For steady flow of heat along a rod, the general equation isd²α/dx² – m² α = 0The value of constant m is |
| A. | (h P/k A C) |
| B. | (h P/k A C)^3/2 |
| C. | (h P/k A C)^1/2 |
| D. | (h P/k A C)^2 |
| Answer» D. (h P/k A C)^2 | |
| 13. |
Provision of fins on a given heat transfer surface will be more effective if there is |
| A. | Fewer but thick fins |
| B. | Large number of thick fins |
| C. | Fewer but thin fins |
| D. | Large number of thin fins |
| Answer» E. | |
| 14. |
The relevant boundary conditions in case of heat transfer from a bar connected to two heat sources at different temperatures are |
| A. | α = α 1 at x = 0 and α = α 2 at x = infinity |
| B. | α = α 1 at x = 1 and α = α 2 at x = 2L |
| C. | α = α 1 at x = infinity and α = α 2 at x = 1 |
| D. | α = α 1 at x = 0 and α = α 2 at x = L |
| Answer» E. | |
| 15. |
“The tube that is used in thermometric well is considered as a hollow fin and the temperature distribution is obtained by using the relation applicable to infinitely long fin”. Choose the correct option |
| A. | True |
| B. | False |
| C. | May be |
| D. | Can't say |
| Answer» C. May be | |
| 16. |
Which one is true regarding rectangular fin? |
| A. | A C = b δ and P = 2(b + δ) |
| B. | A C = 2 b δ and P = 2(b + δ) |
| C. | A C = 3 b δ and P = 2(b + δ) |
| D. | A C = 4 b δ and P = 2(b + δ) |
| Answer» B. A C = 2 b δ and P = 2(b + δ) | |
| 17. |
The correction length for cylindrical fin is(Where, d is the diameter) |
| A. | L C = L + d/4 |
| B. | L C = 2 L + d/4 |
| C. | L C = 3 L + d/4 |
| D. | L C = 4 L + d/4 |
| Answer» B. L C = 2 L + d/4 | |
| 18. |
Analysis of heat flow from the finned surface is made with the following assumptions(i) Uniform heat transfer coefficient, h over the entire fin surface(ii) No heat generation within the fin generation(iii) Homogenous materialIdentify the correct option |
| A. | i only |
| B. | i and ii only |
| C. | i, ii and iii |
| D. | ii only |
| Answer» D. ii only | |
| 19. |
Let us assume a square section fin split longitudinally and used as two fins. This will result in |
| A. | Increase or decrease in heat transfer depending on material of fin |
| B. | Heat flow remains constant |
| C. | Decrease in heat transfer |
| D. | Increase in heat transfer |
| Answer» E. | |
| 20. |
In convection from the tip, we introduced a factor known as |
| A. | Fin length |
| B. | Correction length |
| C. | No fin length |
| D. | Radial length |
| Answer» C. No fin length | |
| 21. |
In thermometric well, the error can be minimized by(i) The value of parameter ml slows down by some quantity.(ii) Lagging of the tube so that conduction of heat along its length is arrestedIdentify the correct option |
| A. | True |
| B. | False |
| C. | May be |
| D. | Can't say |
| Answer» C. May be | |
| 22. |
Choose the correct option regarding fin efficiency and fin effectiveness |
| A. | 2 Fin effectiveness = A FIN/A B (Efficiency of fin) |
| B. | 3 Fin effectiveness = A FIN/A B (Efficiency of fin) |
| C. | Fin effectiveness = A FIN/A B (Efficiency of fin) |
| D. | ½ Fin effectiveness = A FIN/A B (Efficiency of fin) |
| Answer» D. ½ Fin effectiveness = A FIN/A B (Efficiency of fin) | |
| 23. |
The handle of a saucepan, 30 cm long and 2 cm in diameter, is subjected to 100 degree Celsius temperature during a certain cooking operation. The average unit surface conductance over the handle surface is 7.35 W/m² degree in the kitchen air at 24 degree Celsius. The cook is likely to grasp the last 10 cm of the handle and hence the temperature in this region should not exceed 38 degree Celsius. What should be the thermal conductivity of the handle material to accomplish it? The handle may be treated as a fin insulated at the tip |
| A. | 18.36 W/m degree |
| B. | 17.36 W/m degree |
| C. | 16.36 W/m degree |
| D. | 15.36 W/m degree |
| Answer» C. 16.36 W/m degree | |
| 24. |
An increase in fin effectiveness is caused by high value of(i) Convective coefficient(ii) Thermal conductivity(iii) Circumference(iv) AreaIdentify the correct statement |
| A. | 1 and 3 |
| B. | 3 and 4 |
| C. | 2 and 4 |
| D. | 2 and 3 |
| Answer» D. 2 and 3 | |
| 25. |
Let us assume there are two pieces of copper wire 0.1625 cm in diameter with a device that melts it at 195 degree Celsius. The wires are positioned vertically in air at 24 degree Celsius and the heat transfer coefficient of the wire is 17 W/ square m K. Let us say k = 335W/m K i.e. of wire. Find out the energy input? |
| A. | 1.234W |
| B. | 2.652W |
| C. | 4.562W |
| D. | 9.435W |
| Answer» C. 4.562W | |
| 26. |
Consider the following statements pertaining to heat transfer through fins(i) They must be arranged at right angles to the direction of flow of working fluid(ii) The temperature along the fin is variable and accordingly heat transfer rate varies along the fin elements(iii) Fins are equally effective irrespective whether they are on the hot side or cold side of the fluid(iv) Fins are made of materials that have thermal conductivity higher than that of wallIdentify the correct statements |
| A. | 3 and 4 |
| B. | 1 and 3 |
| C. | 2 and 3 |
| D. | 1 and 2 |
| Answer» E. | |
| 27. |
The figure shows a 5 cm diameter rod, 90 cm long, which is having its lower face grinded smooth. The remainder of the rod is exposed to 32 degree Celsius room air and a surface coefficient heat transfer equal to 6.8 W/m² degree exists between the rod surface and the room air. The grinder dissipates mechanical energy at the rate of 35 W. If thermal conductivity of rod material is 41.5 W/m degree, find the temperature of the rod at the point where the grinding is taking place |
| A. | 161.45 degree celsius |
| B. | 151.45 degree celsius |
| C. | 141.45 degree celsius |
| D. | 131.45 degree celsius |
| Answer» C. 141.45 degree celsius | |
| 28. |
Find the value of corrected length for rectangular fin?Where, b is width and t is length of the fin |
| A. | L C = L + b t/2 (b + t) |
| B. | L C = L + b t/ (b + t) |
| C. | L C = L + 2 (b + t) |
| D. | L C = L + b t |
| Answer» B. L C = L + b t/ (b + t) | |
| 29. |
In convection from the tip what is the value of correction length? |
| A. | L C = A C/P |
| B. | L C = L + A C |
| C. | L C = L + P |
| D. | L C = L + A C/P |
| Answer» E. | |
| 30. |
Which one is true for the spine? |
| A. | A C = π d²/4 and P = 4 π d |
| B. | A C = π d²/4 and P = 3 π d |
| C. | A C = π d²/4 and P = π d |
| D. | A C = π d²/4 and P = 2 π d |
| Answer» D. A C = π d²/4 and P = 2 π d | |
| 31. |
The convective coefficient in boilers and condenser is |
| A. | Low |
| B. | High |
| C. | Moderate |
| D. | Depends on time and temperature |
| Answer» C. Moderate | |
| 32. |
In thermometer heat is dissipated from which end? |
| A. | Back side |
| B. | Front side |
| C. | Middle |
| D. | No heat is dissipated |
| Answer» B. Front side | |
| 33. |
Mark the false statement regarding effectiveness of fin |
| A. | A high value of film coefficient adversely affects the fin effectiveness |
| B. | Fin effectiveness is improved if fin is made from a material of low conductivity |
| C. | Fin effectiveness is improved by having thin fins |
| D. | It can also be improved by having closely spaced fins |
| Answer» C. Fin effectiveness is improved by having thin fins | |
| 34. |
The thermometric well is treated as a fin of |
| A. | It is not treated as a fin |
| B. | Infinite length |
| C. | Finite length |
| D. | It depends on the amount of heat dissipation |
| Answer» D. It depends on the amount of heat dissipation | |
| 35. |
Thermometric well apparatus doesn’t consists of |
| A. | Thermometer |
| B. | Pipe line |
| C. | Oil |
| D. | Ammeter |
| Answer» E. | |
| 36. |
In order to achieve maximum heat dissipation the fin should be designed in such a way that has a |
| A. | Maximum lateral surface towards the tip side of fin |
| B. | Minimum lateral surface near the center line |
| C. | Maximum lateral surface at the root side of fin |
| D. | Maximum lateral surface near the center of fin |
| Answer» D. Maximum lateral surface near the center of fin | |
| 37. |
If heat dissipation for one fin is given by 377.45 k J/hour, then what is the heat dissipation for 12 fins? |
| A. | 7529.4 k J/hour |
| B. | 6529.4 k J/hour |
| C. | 5529.4 k J/hour |
| D. | 4529.4 k J/hour |
| Answer» E. | |
| 38. |
If fin is sufficiently thin, so heat flows pertains to |
| A. | One dimensional heat conduction |
| B. | Two dimensional heat conduction |
| C. | Three dimensional heat conduction |
| D. | No heat flow is there |
| Answer» B. Two dimensional heat conduction | |
| 39. |
A steel rod (k = 30 W/m degree) 1 cm in diameter and 5 cm long protrudes from a wall which is maintained at 10 degree Celsius. The rod is insulated at its tip and is exposed to an environment with h = 50 W/m² degree and t a = 30 degree Celsius. Calculate the rate of heat dissipation |
| A. | 2.658 W |
| B. | 3.658 W |
| C. | 4.658 W |
| D. | 5.658 W |
| Answer» C. 4.658 W | |
| 40. |
On a heat transfer surface, fins are provided to |
| A. | Increase turbulence in flow for enhancing heat transfer |
| B. | Increase temperature gradient so as to enhance heat transfer |
| C. | Pressure drop of the fluid should be minimized |
| D. | Surface area is maximum to promote the rate of heat transfer |
| Answer» E. | |
| 41. |
Let us say there are two rods having same dimensions, one made of brass (k = 85W/m K) and the other of copper (k = 375W/m K), having one of their ends inserted into a furnace. At a section 10.5 cm away from the furnace, the temperature of brass rod is 120 degree Celsius. Find the distance at which the same temperature would be reached in the copper rod? Both ends are exposed to the same environment |
| A. | 12.54 cm |
| B. | 45.87 cm |
| C. | 12.34 cm |
| D. | 22.05 cm |
| Answer» E. | |
| 42. |
Three rods, one made of silver (l = 420W/m K), second made of aluminum (k = 210W/m K) and the third made of iron (k = 70W/m K) are coated with a uniform layer of wax all around. The rods are placed vertically in a boiling water bath with 250 mm length of each rod projecting outside. If all the rods are having following dimensions i.e. diameter = 15 mm and length = 300 mm and have identical surface coefficient 12.5W/ m² K, work out the ratio of lengths up to which wax will melt on each rod |
| A. | 2.45:1:1.732 |
| B. | 1.732:1:2.45 |
| C. | 2.45:1.732:1 |
| D. | 1.732:1:2.45 |
| Answer» D. 1.732:1:2.45 | |
| 43. |
The temperature distribution in case of infinitely long fin is |
| A. | t – t a/t₀ – t a = mx |
| B. | t – t a/t₀ – t a = -mx |
| C. | t – t a/t₀ – t a = e-m x |
| D. | t – t a/t₀ – t a = log (m x) |
| Answer» D. t – t a/t₀ – t a = log (m x) | |
| 44. |
The rate of heat transfer in case of infinitely long fin is given by |
| A. | (h P k A)^1/2 (t₀ – t a) |
| B. | (h P A)^1/2 (t₀ – t a) |
| C. | (P k A)^1/2 (t₀ – t a) |
| D. | (h k A)^1/2 (t₀ – t a) |
| Answer» B. (h P A)^1/2 (t₀ – t a) | |
| 45. |
In heat dissipation from an infinitely long fin, the boundary conditions are |
| A. | t = t0 at x = infinity and t = ta at x = 0 |
| B. | t = t0 at x = 0 and t = ta at x = infinity |
| C. | t = t0 at x = 0 and t = ta at x = 0 |
| D. | t = t0 at x = infinity and t = ta at x = infinity |
| Answer» C. t = t0 at x = 0 and t = ta at x = 0 | |
| 46. |
A rod of 10 mm diameter and 80 mm length with thermal conductivity 16W/ m K protrudes from a surface at 160 degree Celsius. The rod is exposed to air at 30 degree Celsius with a convective coefficient of 25W/square m K. How does the heat flow from this rod get affected if the same material volume is used for two fins of the same length? Assume short fin with insulated end |
| A. | 12.25 % |
| B. | 25.6 % |
| C. | 23.4 % |
| D. | 21.2 % |
| Answer» E. | |
| 47. |
The utility of fin in dissipating a given quantity of heat is generally assessed on the basic of how many parameters? |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» C. 3 | |
| 48. |
An centrifugal pump which circulates a hot liquid metal at 500 degree Celsius is driven by a 3600 rpm electric motor. The motor is coupled to the pump impeller by a horizontal steel shaft of dia 25 mm. Let us assume the motor temperature as 60 degree Celsius with the ambient air at 25 degree Celsius, what length of shaft should be specified between the motor and the pump? It may be presumed that the thermal conductivity of the shaft material is 35W/m K, and that the convective film coefficient between the steel shaft and the ambient air is 15.7W/square m K |
| A. | 38.96 cm |
| B. | 54.76 cm |
| C. | 23.76 cm |
| D. | 87.43 cm |
| Answer» B. 54.76 cm | |
| 49. |
Two rods A and B of the same length and diameter protrude from a surface at 120 degree Celsius and are exposed at air at 25 degree Celsius. The temperatures measured at the end of the rods are 50 degree Celsius and 75 degree Celsius. If thermal conductivity of material A is 20W/ m K, calculate it for B. |
| A. | 31.13W/m K |
| B. | 41.13W/m K |
| C. | 51.13W/m K |
| D. | 61.13W/m K |
| Answer» D. 61.13W/m K | |
| 50. |
A copper steel rod (k = 55 W/m degree) has been attached to a plane wall which is maintained at a temperature of 350 degree Celsius. The rod is 8 cm long and has the cross-section of an equilateral triangle with each side 5 mm. Determine the heat dissipation from the rod if it is exposed to a convection environment at 25 degree Celsius with unit surface conductance 100 W/m² degree. Consider end surface loss to be negligible |
| A. | 10.26 W |
| B. | 9.26 W |
| C. | 8.26 W |
| D. | 7.26 W |
| Answer» C. 8.26 W | |