MCQOPTIONS
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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.
| 251. |
Heat transfer and work transfer are |
| A. | boundary phenomena |
| B. | energy interactions |
| C. | energy in the transit |
| D. | all of the mentioned |
| Answer» E. | |
| 252. |
Latent heat is taken at |
| A. | constant temperature |
| B. | constant pressure |
| C. | both of the mentioned |
| D. | none of the mentioned |
| Answer» D. none of the mentioned | |
| 253. |
The specific heat of the substance is defined as the amount of heat required to raise a unit mass of the substance through a unit rise in temperature. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 254. |
For solids and liquids, specific heat |
| A. | depends on the process |
| B. | is independent of the process |
| C. | may or may not depend on the process |
| D. | none of the mentioned |
| Answer» C. may or may not depend on the process | |
| 255. |
The transfer of heat between a wall and a fluid system in motion is called |
| A. | radiation |
| B. | convection |
| C. | conduction |
| D. | none of the mentioned |
| Answer» C. conduction | |
| 256. |
In the equation, dQ=TdX |
| A. | dQ is an inexact differential |
| B. | dX is an exact differential |
| C. | X is an extensive property |
| D. | all of the mentioned |
| Answer» E. | |
| 257. |
Heat flow into a system is taken to be ____, and heat flow out of the system is taken as ____ |
| A. | positive, positive |
| B. | negative, negative |
| C. | negative, positive |
| D. | positive, negative |
| Answer» E. | |
| 258. |
The transfer of heat between two bodies in direct contact is called |
| A. | radiation |
| B. | convection |
| C. | conduction |
| D. | none of the mentioned |
| Answer» D. none of the mentioned | |
| 259. |
According to Dulong and Petit's law, the molar specific heat of solids at high-temperature range varies with the nth power of absolute temperature. Here the value of n is |
| A. | Zero |
| B. | 1 |
| C. | 2 |
| D. | 3 |
| Answer» C. 2 | |
| 260. |
Heat transfer occurs due to _________ difference. |
| A. | Thermal conductivity |
| B. | Temperature |
| C. | Specific heat |
| D. | Heat flux |
| Answer» C. Specific heat | |
| 261. |
In a pulverized fuel fired large power boiler, the heat transfer from the bringing fuel to the walls of the furnace is |
| A. | by conduction only |
| B. | by convection only |
| C. | by conduction and convection |
| D. | predominantly by radiation |
| Answer» E. | |
| 262. |
In which process, the rate of transfer of heat is maximum: |
| A. | conduction |
| B. | convection |
| C. | Radiation |
| D. | In all, heat is transferred with the same speed |
| Answer» D. In all, heat is transferred with the same speed | |
| 263. |
Conduction will not occur when bodies are |
| A. | At same temperature |
| B. | Kept in vacuum |
| C. | Immersed in water |
| D. | Kept in still air |
| Answer» B. Kept in vacuum | |
| 264. |
In an automobile radiator is used to cool the cooling water of the engine, the mode of heat transfer between radiator body and surrounding is_ |
| A. | Conduction |
| B. | Convection |
| C. | Radiation |
| D. | All of the above |
| Answer» C. Radiation | |
| 265. |
Match List 1 with List 2 and select the correct answer using the code given below the lists:List 1(Law)List 2(Effect)Fourier’s LawMass transferStefan Boltzmann LawConductionNewton’s Law of CoolingConvectionFick’s LawRadiation |
| A. | A – 3, B – 1, C – 2, D – 4 |
| B. | A – 2, B – 4, C – 3, D – 1 |
| C. | A – 3, B – 4, C – 2, D – 1 |
| D. | A – 2, B – 1, C – 3, D – 4 |
| Answer» C. A – 3, B – 4, C – 2, D – 1 | |
| 266. |
For turbulent flow, Reynolds number must be |
| A. | Less than 5000 |
| B. | Equal to 6000 |
| C. | Less than 6000 |
| D. | Greater than 6000 |
| Answer» E. | |
| 267. |
Which of the following is the most widely used heat insulating material for pipelines carrying steam ? |
| A. | Tar dolomite bricks followed by asbestos. |
| B. | Fireclay refractory followed by aluminium sheet. |
| C. | Cotton followed by aluminium foil. |
| D. | 85% magnesia cement and glass wool. |
| Answer» E. | |
| 268. |
A composite wall consists of two plates A and B placed in series normal to the flow of heat. The thermal conductivities are kA and kB and the specific heat capacities are CPA and CPB for plates A and B respectively. Plate B has twice the thickness of plate A. At steady state, the temperature difference across plate A is greater than that across plate B, when |
| A. | CPA > CPB |
| B. | CPA < CPB |
| C. | kA < 0.5kB |
| D. | kA>2 kB |
| Answer» D. kA>2 kB | |
| 269. |
jH factor for heat transfer depends upon the __________ number. |
| A. | Biot |
| B. | Nusselt |
| C. | Reynolds |
| D. | Prandtl |
| Answer» D. Prandtl | |
| 270. |
Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re^0.8 . Prⁿ, is not valid, if the value of |
| A. | n = 0.4 is used for heating. |
| B. | n = 0.3 is used for cooling. |
| C. | Reynolds number for the flow involved is > 10000. |
| D. | Reynolds number for the flow involved is < 2100. |
| Answer» E. | |
| 271. |
The thermal boundary layer at NPr > 1 |
| A. | is thicker than hydrodynamic boundary layer. |
| B. | is thinner than hydrodynamic boundary layer. |
| C. | and the hydrodynamic boundary layer are identical. |
| D. | disappears. |
| Answer» C. and the hydrodynamic boundary layer are identical. | |
| 272. |
Which of the following accessories is provided in the vapor line of an evaporator for removing the entrained liquid ? |
| A. | Bleed point |
| B. | Vent |
| C. | Catchall |
| D. | Baffle |
| Answer» D. Baffle | |
| 273. |
Multiple effect evaporators are used to |
| A. | increase the steam economy & decrease the capacity. |
| B. | increase the steam economy & the capacity. |
| C. | decrease the steam economy & the capacity. |
| D. | decrease the steam economy & increase the capacity. |
| Answer» C. decrease the steam economy & the capacity. | |
| 274. |
Water is normally used as a coolant in the heat exchange equipments mainly because of its |
| A. | abundance & high heat capacity |
| B. | low density |
| C. | low viscosity |
| D. | high fluidity |
| Answer» B. low density | |
| 275. |
The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m⁻¹.°C⁻¹ respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m⁻².°C⁻¹. The rate of heat loss from the outer surface in W.m⁻² is |
| A. | 165.4 |
| B. | 167.5 |
| C. | 172.5 |
| D. | 175 |
| Answer» B. 167.5 | |
| 276. |
"The ratio of the total emissive power to the absorptivity for all bodies is same at ther-mal equilibrium". This is __________ law. |
| A. | Kirchoffs |
| B. | Planck's |
| C. | Wien's displacement |
| D. | Stefan-Boltzman |
| Answer» B. Planck's | |
| 277. |
For condensation of pure vapors, if the heat transfer co-efficients in filmwise and drop-wise condensation are respectively hf and hd, then |
| A. | hf = hd |
| B. | hf > hd |
| C. | hf < hd |
| D. | hf could be greater or smaller than hd |
| Answer» D. hf could be greater or smaller than hd | |
| 278. |
Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger ? |
| A. | Corrosiveness |
| B. | Fouling characteristic |
| C. | Viscosity |
| D. | None of these |
| Answer» E. | |
| 279. |
Which type of heat exchanger is preferred for heavy heat loads ? |
| A. | Double pipe |
| B. | Plate fine |
| C. | Series and parallel set of shell and tube |
| D. | None of these |
| Answer» D. None of these | |
| 280. |
The critical radius of insulation for cylindrical pipe is (where, hi = heat transfer coefficient at inside of the pipe ) |
| A. | K/h0 |
| B. | 2K/h0 |
| C. | hi/K |
| D. | 2hi/K |
| Answer» B. 2K/h0 | |
| 281. |
The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m². The approximate surface temperature (K) is (Stefan-Boltzman constant = 5.67x10⁻⁸ W/m².K⁴) |
| A. | 1000 |
| B. | 727 |
| C. | 800 |
| D. | 1200 |
| Answer» B. 727 | |
| 282. |
Which of the following has maximum thermal conductivity ? |
| A. | Iron |
| B. | Coal |
| C. | Nitrogen |
| D. | Tar |
| Answer» B. Coal | |
| 283. |
At what value of Prandtl number, conduction is negligible in the turbulent core of a fluid flowing through a heated pipe ? |
| A. | 0.5 |
| B. | < 0.5 |
| C. | > 0.6 |
| D. | < 0.1 |
| Answer» D. < 0.1 | |
| 284. |
The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K= 0.04 W/m.°K and thickness 0.16m is 10 W/m². The temperature of the inside wall is - 5°C. The outside wall temperature is |
| A. | 25°C |
| B. | 30°C |
| C. | 35°C |
| D. | 40°C |
| Answer» D. 40°C | |
| 285. |
The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h₀ = heat transfer coefficient at the outer surface) |
| A. | K/h₀ |
| B. | 2K/h₀ |
| C. | h₀/K |
| D. | h₀/2K |
| Answer» C. h₀/K | |
| 286. |
At what value of Prandtl number, the hydrodynamic and thermal boundary layers are identical ? |
| A. | 0.5 |
| B. | 1 |
| C. | 1.5 |
| D. | 80 |
| Answer» C. 1.5 | |
| 287. |
The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are |
| A. | (COP)R = (COP)HP = 0.6 |
| B. | (COP)R = 2.5; (COP)HP = 1.5 |
| C. | (COP)R = 1.5; (COP)HP = 2.5 |
| D. | (COP)R = (COP)HP = 2.5 |
| Answer» D. (COP)R = (COP)HP = 2.5 | |
| 288. |
If average heat transfer co-efficient is ha and the local coefficient at the end of the plate is hl then in case of heat transfer to a fluid flowing over a flat plate, heated over its entire length |
| A. | ha = hl |
| B. | ha = 2hl |
| C. | ha = 0.5 hl |
| D. | ha = 0.75 hl |
| Answer» C. ha = 0.5 hl | |
| 289. |
Which has the lowest Prandtl number ? |
| A. | Liquid metal |
| B. | Aqueous solution |
| C. | Water |
| D. | Lube oil |
| Answer» B. Aqueous solution | |
| 290. |
Which of the following has the lowest Prandtl number ? |
| A. | Molten sodium (a coolant used in fast breeder reactor) |
| B. | Water |
| C. | Transformer oil |
| D. | Dilute H₂SO₄ |
| Answer» B. Water | |
| 291. |
For a laminar flow of fluid in a circular tube, 'h1' is the convective heat transfer co-efficient at velocity 'V1'. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is |
| A. | 1.26 h1 |
| B. | 0.794 h1 |
| C. | 0.574 h1 |
| D. | 1.741 h1 |
| Answer» C. 0.574 h1 | |
| 292. |
Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling ? |
| A. | Square pitch |
| B. | Triangular pitch |
| C. | Diagonal square pitch |
| D. | None of these |
| Answer» C. Diagonal square pitch | |
| 293. |
A tank painted with which of the following coloured paints, would heat up maximum by radiation from sun ? |
| A. | Yellow paint |
| B. | White paint |
| C. | Black paint |
| D. | Grey paint |
| Answer» D. Grey paint | |
| 294. |
Stefan-Boltzman law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in °C, T = absolute temperature in ° K ) |
| A. | t⁴ |
| B. | T⁴ |
| C. | 1/t⁴ |
| D. | 1/T⁴ |
| Answer» C. 1/t⁴ | |
| 295. |
Which of the following heat flow situations pertains to free or natural convection? |
| A. | Air conditioning installations and nuclear reactors |
| B. | Flow of water inside the condenser tubes |
| C. | Cooling of internal combustion engine |
| D. | Cooling of billets in atmosphere |
| Answer» E. | |
| 296. |
Mark the system where heat transfer is given by forced convection |
| A. | Chilling effect of cold wind on warm body |
| B. | Fluid passing through the tubes of a condenser and other heat exchange equipment |
| C. | Heat flow from a hot pavement to surrounding atmosphere |
| D. | Heat exchange on the outside of cold and warm pipes |
| Answer» C. Heat flow from a hot pavement to surrounding atmosphere | |
| 297. |
The fluid particles move in flat or curved un-mixing layers or streams and follow a smooth continuous path. This type of flow is known as |
| A. | Steady flow |
| B. | Stream flow |
| C. | Turbulent flow |
| D. | Laminar flow |
| Answer» E. | |
| 298. |
The free convection coefficient is given byh = C₁ d t m/l^(1 – 3m)The value of exponent for laminar flow is |
| A. | 0.5 |
| B. | 0.6 |
| C. | 0.7 |
| D. | 0.8 |
| Answer» B. 0.6 | |
| 299. |
What is the value of convective coefficient of air and superheated steam in case of forced convection? |
| A. | 30-900 W/m² K |
| B. | 30-700 W/m² K |
| C. | 30-300 W/m² K |
| D. | 30-400 W/m² K |
| Answer» D. 30-400 W/m² K | |
| 300. |
For a plate of length l, an average value of Nusselt number is given by |
| A. | Nu = 0.664 (Re)^0.5 (Pr)^0.54 |
| B. | Nu = 0.664 (Re)^0.5 (Pr)^0.74 |
| C. | Nu = 0.664 (Re)^0.5 (Pr)^0.27 |
| D. | Nu = 0.664 (Re)^0.5 (Pr)^0.33 |
| Answer» E. | |