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MCQOPTIONS
This section includes 968 Mcqs, each offering curated multiple-choice questions to sharpen your GATE (Mechanical Engineering) knowledge and support exam preparation. Choose a topic below to get started.
| 301. |
Velocity within the given fields would be similar in magnitude, direction and turbulence pattern when |
| A. | Nusselt number are different |
| B. | Nusselt number are same |
| C. | Reynolds number are different |
| D. | Reynolds number are same |
| Answer» E. | |
| 302. |
The free convection coefficient is given byh = C₁ d t m/l^(1 – 3m)The value of exponent for turbulent flow is |
| A. | 0.43 |
| B. | 0.33 |
| C. | 0.23 |
| D. | 0.13 |
| Answer» C. 0.23 | |
| 303. |
A region of fluid motion near a plate in which temperature gradient exist is |
| A. | Thermal boundary layer |
| B. | Diathermia boundary layer |
| C. | Turbulent flow |
| D. | Laminar flow |
| Answer» B. Diathermia boundary layer | |
| 304. |
The ratio of inertia force to viscous force is known as |
| A. | Grashof number |
| B. | Reynolds number |
| C. | Fourier number |
| D. | Nusselt number |
| Answer» C. Fourier number | |
| 305. |
The convection coefficients for boiling and condensation lie in the range |
| A. | 5000-12500 W/m 2 K |
| B. | 2500-100000 W/m 2 K |
| C. | 2500-5000 W/m 2 K |
| D. | 2500-12500 W/m 2 K |
| Answer» C. 2500-5000 W/m 2 K | |
| 306. |
A sphere, a cube and a thin circular plate, all made of the same material and having the same mass are initially heated to the temperature of 250 degree Celsius. When left in air at room temperature, what will be their response to cooling? |
| A. | Cube will cool faster than sphere but slower than the circular plate |
| B. | They will cool at the same rate |
| C. | Sphere will cool faster |
| D. | Circular plate will cool at the slower rate |
| Answer» B. They will cool at the same rate | |
| 307. |
For a duct of rectangular cross-section with length l and breadth b, the value of d e is |
| A. | l b / l + b |
| B. | 2 l b |
| C. | 2 l b / l + b |
| D. | 4 l b / l + b |
| Answer» D. 4 l b / l + b | |
| 308. |
Air flows through a 10 cm internal diameter tube at the rate of 75 kg/hr. Measurements indicate that at a particular point in the tube, the pressure and temperature of air are 1.5 bar and 325 K whilst the tube wall temperature is 375 K. Find heat transfer rate from one meter length in the region of this pointThe general non-dimensional correlation for turbulent flow in the tube isNu = 0.023 (Re)^0.8 (Pr)^0.4Where the fluid properties are evaluated at the bulk temperature |
| A. | 147.35 W |
| B. | 157.35 W |
| C. | 167.35 W |
| D. | 177.35 W |
| Answer» E. | |
| 309. |
Newton-Rikhman law is given by |
| A. | Q = h A (t s – t f) |
| B. | Q = 2 h A (t s – t f) |
| C. | Q = 3 h A (t s – t f) |
| D. | Q = 4 h A (t s – t f) |
| Answer» B. Q = 2 h A (t s – t f) | |
| 310. |
On a summer day, a scooter rider feels more comfortable while on the move than while at a stop light because |
| A. | An object in motion captures less radiation |
| B. | Air has a low specific heat and hence it is cooler |
| C. | More heat is loss by convection and radiation while in motion |
| D. | Air is transparent to radiation and hence it is cooler than the body |
| Answer» E. | |
| 311. |
Forced air flows over a convection heat exchanger in a room heater, resulting in a convective heat transfer coefficient 1.136 k W/m² K. The surface temperature of heat exchanger may be considered constant at 65 degree Celsius, and the air is at 20 degree Celsius. Determine the heat exchanger surface area required for 8.8 k W of heating |
| A. | 0.272 m² |
| B. | 0.472 m² |
| C. | 0.172 m² |
| D. | 0.672 m² |
| Answer» D. 0.672 m² | |
| 312. |
For laminar flow, Reynolds number must not be less than |
| A. | 1000 |
| B. | 2000 |
| C. | 20000 |
| D. | 40000 |
| Answer» E. | |
| 313. |
Air at 20 degree Celsius flows over a flat surface maintained at 80 degree Celsius. The local heat flow at a point was measured as 1250 W/m² .Take thermal conductivity of air as 0.028 W/m K, calculate the temperature at a distance 0.5 mm from the surface |
| A. | 57.682 degree celsius |
| B. | 67.682 degree celsius |
| C. | 77.682 degree celsius |
| D. | 87.682 degree celsius |
| Answer» B. 67.682 degree celsius | |
| 314. |
A finned tube hot water radiator with a fan blowing air over it is kept in rooms during winter. The major portion of the heat transfer from the radiation is due to |
| A. | Combined conduction and radiation |
| B. | Radiation to the surroundings |
| C. | Better conduction |
| D. | Convection to the air |
| Answer» E. | |
| 315. |
For inclined plates we multiply Grashoff number with |
| A. | Cos 2 α |
| B. | Sin 2 α |
| C. | Sin α |
| D. | Cos α |
| Answer» E. | |
| 316. |
Air enters a rectangular duct measuring 30 cm by 40 cm with a velocity of 8.5 m/s and a temperature of 40 degree Celsius. The flowing air has a thermal conductivity 0.028 W/m K, kinematic viscosity 16.95 * 10¯⁶ m²/s and from empirical correlations the Nusselt number has been approximated to be 425. Find out the flow Reynolds number |
| A. | 1.1719 * 10⁶ |
| B. | 2.1719 * 10⁶ |
| C. | 0.1719 * 10⁶ |
| D. | 4.1719 * 10⁶ |
| Answer» D. 4.1719 * 10⁶ | |
| 317. |
How many types of convection are there? |
| A. | 4 |
| B. | 3 |
| C. | 2 |
| D. | 1 |
| Answer» C. 2 | |
| 318. |
A hot plate of 15 cm² area maintained at 200 degree celsius is exposed to still air at 30 degree Celsius temperature. When the smaller side of the plate is held vertical, convective heat transfer rate is 15 per cent higher than bigger side of the plate is held vertical. Find size of the plate. The appropriate correlation for the convection coefficient isNu = 0.60 (Gr Pr)^0.25 |
| A. | l = 5.123 cm and b = 2.928 cm |
| B. | l = 6.123 cm and b = 3.928 cm |
| C. | l = 7.123 cm and b = 4.928 cm |
| D. | l = 8.123 cm and b = 5.928 cm |
| Answer» B. l = 6.123 cm and b = 3.928 cm | |
| 319. |
Heat is being transferred by convection from water at 48 degree Celsius to glass plate whose surface is exposed to water at 40 degree Celsius. The thermal conductivity of water is 0.6 W/m K and the thermal conductivity of glass is 1.2 W/m K. The spectral gradient of temperature in the water at the water glass interface is 10¯⁴ K/m. The heat transfer coefficient in W/m² K is |
| A. | 0.0 |
| B. | 750 |
| C. | 6.0 |
| D. | 4.8 |
| Answer» C. 6.0 | |
| 320. |
What is the value of convective coefficient of oil in case of forced convection? |
| A. | 1460-3000 W/m² K |
| B. | 460-3000 W/m² K |
| C. | 60-3000 W/m² K |
| D. | 160-3000 W/m² K |
| Answer» D. 160-3000 W/m² K | |
| 321. |
Thermo-physical properties of the fluid are represented by(i) Density(ii) Viscosity(iii) Specific heat(iv) Thermal conductivityIdentify the correct option |
| A. | 1 and 2 |
| B. | 1, 2, 3 and 4 |
| C. | 2, 3 and 4 |
| D. | 1, 2 and 3 |
| Answer» C. 2, 3 and 4 | |
| 322. |
For laminar flow, Prandtl number must be more than |
| A. | 0.05 |
| B. | 0.2 |
| C. | 0.6 |
| D. | 0.3 |
| Answer» D. 0.3 | |
| 323. |
For transient flow, the value of Reynolds number may vary between |
| A. | 1450-9870 |
| B. | 1200-4500 |
| C. | 2300-6000 |
| D. | 6000-9000 |
| Answer» D. 6000-9000 | |
| 324. |
Forced convection in a liquid bath is caused by |
| A. | Intense stirring by an external agency |
| B. | Molecular energy interactions |
| C. | Density difference brought about by temperature gradients |
| D. | Flow of electrons in a random fashion |
| Answer» B. Molecular energy interactions | |
| 325. |
For laminar flow, Reynolds number should be |
| A. | Less than 2300 |
| B. | Equal to 2300 |
| C. | Greater than 2300 |
| D. | Less than 4300 |
| Answer» B. Equal to 2300 | |
| 326. |
For turbulent flow over a flat plate, the average value of Nusselt number is prescribed by the relationNu = 0.664 (Re)^0.5 (Pr)^0.33Which of the following is then a false statement?The average heat transfer coefficient increases as |
| A. | 1/5 power of plate length |
| B. | 2/3 power of thermal conductivity |
| C. | 1/3 power of specific heat |
| D. | 4/5 power of a free stream velocity |
| Answer» B. 2/3 power of thermal conductivity | |
| 327. |
A thin walled duct of 0.5 m diameter has been laid in an atmosphere of quiescent air at 15 degree Celsius and conveys a particular gas at 205 degree Celsius. Base your calculations on one meter length of the duct, estimate the convective coefficient of heat transfer |
| A. | 5.086 W/m² K |
| B. | 6.086 W/m² K |
| C. | 7.086 W/m² K |
| D. | 8.086 W/m² K |
| Answer» B. 6.086 W/m² K | |
| 328. |
A heat treat steel plate measures 3 m by 1 m and is initially at 30 degree Celsius. It is cooled by blowing air parallel to 1 m edge at 9 km/hr. If the air is at 10 degree Celsius. Estimate the convection heat transfer from both sides of the plate |
| A. | 477.7 W |
| B. | 547.7 W |
| C. | 647.7 W |
| D. | 747.6 W |
| Answer» E. | |
| 329. |
Calculate the rate of heat loss from a human body which may be considered as a vertical cylinder 30 cm in diameter, and 175 cm high while standing in a 30 km/hr wind at 15 degree Celsius. Human has a surface temperature of 35 degree Celsius |
| A. | 588.86 W |
| B. | 688.86 W |
| C. | 788.86 W |
| D. | 888.86 W |
| Answer» C. 788.86 W | |
| 330. |
Which of the following is true for turbulent flow? |
| A. | GrPr > 10⁸ |
| B. | GrPr > 10⁹ |
| C. | GrPr > 10⁵ |
| D. | GrPr > 10⁷ |
| Answer» C. GrPr > 10⁵ | |
| 331. |
Investigate the effect of following condition on the average value of heat transfer coefficient in flow through a tubeTwo fold increases in flow velocity by varying mass flow rateIt may be presumed that there is no change in the temperature of the liquid and the tube wall, and that the flow through the tube is turbulent in character |
| A. | 64.1% decrease |
| B. | 64.1% increase |
| C. | 74.1%decrease |
| D. | 74.1% increases |
| Answer» E. | |
| 332. |
The convective heat transfer coefficient in laminar flow over a flat plate |
| A. | Increases with distance |
| B. | Increases if a higher viscosity fluid is used |
| C. | Increases if a denser fluid is used |
| D. | Decreases with increase in free stream velocity |
| Answer» D. Decreases with increase in free stream velocity | |
| 333. |
The local film coefficient for laminar flow past a flat plate may be obtained from the correlation |
| A. | Nu = 0.332 (Re)^0.5 (Pr)^0.33 |
| B. | Nu = 0.332 (Re)^0.5 (Pr)^0.43 |
| C. | Nu = 0.332 (Re)^0.5 (Pr)^0.53 |
| D. | Nu = 0.332 (Re)^0.5 (Pr)^0.63 |
| Answer» B. Nu = 0.332 (Re)^0.5 (Pr)^0.43 | |
| 334. |
Air at atmospheric pressure and 20 degree Celsius flows with 6 m/s velocity through main trunck duct of air conditioning system. The duct is rectangular in cross-section and measures 40 cm by 80 cm. Determine heat loss per meter length of duct corresponding to unit temperature difference. The relevant thermos-physical properties of air arev = 15 * 10¯⁶ m²/sα = 7.7 * 10¯² m²/hrk = 0.026 W/m degree |
| A. | 32.768 W |
| B. | 42.768 W |
| C. | 52.768 W |
| D. | 62.768 W |
| Answer» C. 52.768 W | |
| 335. |
The correlation for liquid metal is given by |
| A. | Nu = 0.465 (Re) (Pr) |
| B. | Nu = 0.565 (Re) (Pr) |
| C. | Nu = 0.665 (Re) (Pr) |
| D. | Nu = 0.765 (Re) (Pr) |
| Answer» C. Nu = 0.665 (Re) (Pr) | |
| 336. |
Reynolds number is given by the quantity(Where,p is densityδ is viscosityV is volumel is length) |
| A. | p V l/δ |
| B. | 2 p V l/δ |
| C. | 3 p V l/δ |
| D. | 4 p V l/δ |
| Answer» B. 2 p V l/δ | |
| 337. |
In many flow situations, the duct can be(i) Circular(ii) Rectangle(iii) Trapezoidal(iv) AnnulusIdentify the correct option |
| A. | 1 and 2 |
| B. | 1, 2, 3 and 4 |
| C. | 1, 2 and 3 |
| D. | 3 and 4 |
| Answer» C. 1, 2 and 3 | |
| 338. |
A horizontal heated plate at 200 degree Celsius and facing upwards has been placed in still air at 20 degree Celsius. If the plate measures 1.25 m by 1 m, make calculations for the heat loss by natural convection. The convective film coefficient for free convection is given by the following empirical relationh = 0.32 (α)^0.25 W/m² KWhere α is the mean film temperature in degrees kelvin |
| A. | 6006 W |
| B. | 5006 W |
| C. | 4006 W |
| D. | 3006 W |
| Answer» B. 5006 W | |
| 339. |
Which of the following is true for laminar flow? |
| A. | 10^4 < Gr Pr < 10^7 |
| B. | 10^4 < Gr Pr < 10^8 |
| C. | 10^4 < Gr Pr < 10^9 |
| D. | 10^4 < Gr Pr < 10^10 |
| Answer» D. 10^4 < Gr Pr < 10^10 | |
| 340. |
The value of film coefficient is dependent upon(i) Boundary layer configuration(ii) Geometry and orientation of the surface(iii) Surface conditions |
| A. | 1 and 2 |
| B. | 2 and 3 |
| C. | 1 and 2 |
| D. | 1, 2 and 3 |
| Answer» E. | |
| 341. |
Conduction plus fluid flow in motion is known as |
| A. | Radiation |
| B. | Conduction |
| C. | Convection |
| D. | Heat exchanger |
| Answer» D. Heat exchanger | |
| 342. |
If an annulus has an inner diameter of d₁ and an outer diameter of d₂ then the equivalent diameter is |
| A. | 2 d₂ – d₁ |
| B. | d₂ – 2 d₁ |
| C. | d₁ – d₂ |
| D. | d₂ – d₁ |
| Answer» E. | |
| 343. |
The oil pan of 1.6 engine approximates a flat plate 0.3 m wide by 0.45 m long and protrudes below the framework of the automobile. The engine oil is at 95 degree Celsius and the ambient air temperature is 35 degree Celsius. If the automobile runs at 36 km/hr, make calculations for the rate of heat transfer from the oil-pan surface. Assume negligible resistance to conduction through the oil pan |
| A. | 190.37 W |
| B. | 180.37 W |
| C. | 170.37 W |
| D. | 160.37 W |
| Answer» D. 160.37 W | |
| 344. |
A motor cycle cylinder consists of ten fins, each 150 mm outside diameter and 75 mm inside diameter. The average fin temperature is 500 degree Celsius and the surrounding air is at 20 degree Celsius temperature. Make calculations for the rate of heat dissipation from the cylinder fins by convection when motor cycle is stationary and convective coefficient is 6 W/m² K |
| A. | 432.2 W |
| B. | 532.2 W |
| C. | 632.2 W |
| D. | 763.2 W |
| Answer» E. | |
| 345. |
Free correction modulus is given by |
| A. | p² β g c P/µ |
| B. | p² β g c P/k |
| C. | p² β g c P/µ k |
| D. | p² β g c P |
| Answer» D. p² β g c P | |
| 346. |
A body cooling from 80 degree Celsius to 70 degree Celsius takes 10 minutes when left exposed to environmental conditions. If the body is to cool further from 70 degree Celsius to 60 degree Celsius under the same external conditions, it will take |
| A. | Same time of 10 minutes |
| B. | More than 10 minutes |
| C. | Less than 10 minutes |
| D. | Time will depend upon the environmental conditions |
| Answer» C. Less than 10 minutes | |
| 347. |
The characteristic dimension d in the relation R E = V d p/δ is the equivalent diameter and is defined as how many times the cross-sectional flow area divided by wetted perimeter |
| A. | 7 |
| B. | 4 |
| C. | 1 |
| D. | 6 |
| Answer» C. 1 | |
| 348. |
Choose the most important factor on which the heat conducted through a wall in a unit time will depend on ? |
| A. | Thickness of the wall. |
| B. | Area of the wall perpendicular to heat flow. |
| C. | Material of the wall. |
| D. | Temperature difference between the two surfaces of the wall. |
| Answer» E. | |
| 349. |
The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re^0.8, where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter (D) as |
| A. | (D)^-1.8 |
| B. | (D)^-0.2 |
| C. | (D)^0.2 |
| D. | (D)^1.8 |
| Answer» C. (D)^0.2 | |
| 350. |
What is the emissivity of a black body ? |
| A. | 1 |
| B. | 0 |
| C. | 0.90 |
| D. | 0.5 |
| Answer» B. 0 | |