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.
| 451. |
For evaporation of viscous solution in a multiple effect evaporator, the prefered feeding scheme is |
| A. | Forward |
| B. | Backward |
| C. | Parallel |
| D. | None of these |
| Answer» C. Parallel | |
| 452. |
When warm and cold liquids are mixed, the heat transfer is mainly by |
| A. | Conduction |
| B. | Convection |
| C. | Radiation |
| D. | Both A & C |
| Answer» C. Radiation | |
| 453. |
In which mode of heat transfer, the Biot number is important? |
| A. | Transient heat conduction |
| B. | Natural convection |
| C. | Forced convection |
| D. | Radiation |
| Answer» B. Natural convection | |
| 454. |
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 | |
| 455. |
In case of parallel flow heat exchanger, the lowest temperature theoretically attainable by the hot fluid is __________ the outlet temperature of the cold fluid. |
| A. | Equal to |
| B. | More than |
| C. | Less than |
| D. | Either more or less than (depending upon the fluid) |
| Answer» B. More than | |
| 456. |
The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body) |
| A. | αT |
| B. | α 1/T |
| C. | α T⁴ |
| D. | Independent of T |
| Answer» C. α T⁴ | |
| 457. |
Heat sensitive materials can be concentrated in an evaporator employing |
| A. | Vacuum |
| B. | High pressure |
| C. | High residence time |
| D. | None of these |
| Answer» B. High pressure | |
| 458. |
Viscous & heat sensitive liquids are concentrated in __________ evaporators. |
| A. | Open pan |
| B. | Long tube |
| C. | Agitated film |
| D. | None of these |
| Answer» D. None of these | |
| 459. |
The energy radiated from a surface Q at absolute temperature T is related as |
| A. | Q ∝ T² |
| B. | Q ∝ T⁴ |
| C. | Q ∝ T³ |
| D. | None of these |
| Answer» C. Q ∝ T³ | |
| 460. |
For a multipass shell and tube heat exchanger, the LMTD correction factor is always |
| A. | 1 |
| B. | > 1 |
| C. | < 1 |
| D. | Between 1 & 2 |
| Answer» D. Between 1 & 2 | |
| 461. |
Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the |
| A. | Existence of thermal boundary layer |
| B. | Temperature gradient produced due to density difference |
| C. | Buoyancy of the bubbles produced at active nucleation site |
| D. | None of these |
| Answer» E. | |
| 462. |
With increase in the distance between the heat source and the object receiving the heat, the radiation heat transfer |
| A. | Decreases |
| B. | Increases |
| C. | Increases exponentially |
| D. | Remains unaffected |
| Answer» B. Increases | |
| 463. |
The unit of conductance in SI unit is |
| A. | W/m |
| B. | W/m² |
| C. | W/°K |
| D. | W/m°K |
| Answer» D. W/m°K | |
| 464. |
Leidenfrost point is a term concerned with the |
| A. | Condensation of the saturated vapor on a cold surface |
| B. | Concentration of a corrosive solution by evaporation |
| C. | Heat transfer between two highly viscous liquids |
| D. | Boiling of a liquid on a hot surface |
| Answer» E. | |
| 465. |
Which of the following is the most controlling factor for the rate of bubble detachment from the hot solid surface? |
| A. | Liquid density |
| B. | Liquid viscosity |
| C. | Hot surface temperature |
| D. | Interfacial tension |
| Answer» E. | |
| 466. |
Heat transfer efficiency leading of energy conservation in a heat exchanger can be achieved by |
| A. | Keeping the heat transfer surface clean |
| B. | Enhancing the fluid pumping rate |
| C. | Increasing the tube length |
| D. | None of these |
| Answer» B. Enhancing the fluid pumping rate | |
| 467. |
The critical radius 'r' of insulation on a pipe is given by |
| A. | r = 2k/h |
| B. | r = k/h |
| C. | r = k/2h |
| D. | r = h/k |
| Answer» C. r = k/2h | |
| 468. |
For flow over a flat plate, the ratio of thermal boundary layer thickness, 'xt' and hydrodynamic boundary layer thickness 'x' is equal to (where, NPr = Prandtl number) |
| A. | NPr |
| B. | NPr1/3 |
| C. | NPr-1 |
| D. | NPr-1/3 |
| Answer» C. NPr-1 | |
| 469. |
Steam trap is used to |
| A. | Condense the steam flowing in the pipeline |
| B. | Remove water resulting from partial condensation of steam |
| C. | Stop the supply of steam |
| D. | None of these |
| Answer» C. Stop the supply of steam | |
| 470. |
For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area |
| A. | Increases |
| B. | Decreases |
| C. | Remains constant |
| D. | Passes through a maxima |
| Answer» E. | |
| 471. |
Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be |
| A. | 0.35 |
| B. | 0.45 |
| C. | 0.55 |
| D. | 0.85 |
| Answer» C. 0.55 | |
| 472. |
In thermal radiation for a black body (where, ε is emissivity and α is absorptivity) |
| A. | α = 1; ε ≠ 1 |
| B. | α ≠ 1, ε = 1 |
| C. | α ≠ 1, ε ≠ 1 |
| D. | α = 1; ε = 1 |
| Answer» E. | |
| 473. |
Open pan evaporators are preferred to be used, when the solution to be concentrated is |
| A. | Scaling |
| B. | Highly viscous |
| C. | Corrosive |
| D. | Salty |
| Answer» C. Corrosive | |
| 474. |
In evaporators, lowering the feed temperature |
| A. | Increases the heating area required |
| B. | Reduces the economy |
| C. | Both A and B |
| D. | Decreases the heating area required |
| Answer» D. Decreases the heating area required | |
| 475. |
LMTD for evaporators & condensers for a given terminal parameters & set of conditions for counterflow is equal to that for parallel flow. In such heat exchangers, with one of the fluids condensing or evaporating, the surface area required is the least in the __________ flow. |
| A. | Parallel |
| B. | Mixed |
| C. | Counterflow |
| D. | Same in either A, B or C |
| Answer» E. | |
| 476. |
Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re0.8 . 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. | |
| 477. |
Economy of a multiple effect evaporator is not influenced much by the |
| A. | Boiling point elevations |
| B. | Temperature of the feed |
| C. | Rate of heat transfer |
| D. | Ratio of the weight of the thin liquor to thick liquor |
| Answer» B. Temperature of the feed | |
| 478. |
Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger? |
| A. | Corrosiveness & fouling characteristics |
| B. | Pressure |
| C. | Viscosity |
| D. | Density |
| Answer» E. | |
| 479. |
In a shell and tube heat exchanger, |
| A. | The temperature drops in the two fluids and the wall are proportional to individual resistances |
| B. | The temperature drop is inversely proportional to the resistance across which the drop occurs |
| C. | There is no relationship between temperature drop and resistance |
| D. | The relationship is not generalised |
| Answer» B. The temperature drop is inversely proportional to the resistance across which the drop occurs | |
| 480. |
Steam is routed through the tube in case of a __________ evaporator. |
| A. | Basket type |
| B. | Horizontal tube |
| C. | Short tube vertical |
| D. | Long tube vertical |
| Answer» C. Short tube vertical | |
| 481. |
Intermittant tube cleaning is possible to be done in case of a __________ evaporator. |
| A. | Basket type |
| B. | Horizontal tube |
| C. | Calendria |
| D. | None of these |
| Answer» B. Horizontal tube | |
| 482. |
The thickness of condensate layer in filmwise condensation depends on the |
| A. | Condensation rate |
| B. | Surface configuration |
| C. | Liquid flow rate from the surface |
| D. | All of the above |
| Answer» E. | |
| 483. |
Small scale evaporation is done in a |
| A. | Heat exchanger |
| B. | Condenser |
| C. | Multiple effect evaporator |
| D. | Steam jacketed kettle |
| Answer» E. | |
| 484. |
An equipment which converts the latent or sensible heat of one fluid into the latent heat of vaporisation of another, is called a |
| A. | Boiler |
| B. | Heat exchanger |
| C. | Recuperator |
| D. | Regenerator |
| Answer» C. Recuperator | |
| 485. |
Corrosiveness of steam condensate is due to the presence of |
| A. | CO₂ |
| B. | Dissolved O₂ |
| C. | Both A & B |
| D. | Neither A nor B |
| Answer» D. Neither A nor B | |
| 486. |
Planck's distribution law is valid for __________ bodies. |
| A. | Black |
| B. | White |
| C. | Coloured |
| D. | All of the above |
| Answer» D. All of the above | |
| 487. |
A composite flat wall of a furnace is made of two materials 'A' and 'B'. The thermal conductivity of 'A' is twice of that of material 'B', while the thickness of layer of 'A' is half that of B. If the temperature at the two sides of the wall are 400 and 1200°K, then the temperature drop (in °K) across the layer of material 'A' is |
| A. | 125 |
| B. | 133 |
| C. | 150 |
| D. | 160 |
| Answer» E. | |
| 488. |
For the same heat load and mass flow rate in the tube side of a shell and tube heat exchanger, one may use multipass on the tube side, because it |
| A. | Decreases the pressure drop |
| B. | Decreases the outlet temperature of cooling medium |
| C. | Increases the overall heat transfer coefficient |
| D. | None of these |
| Answer» D. None of these | |
| 489. |
1000 kg of wet solids are to be dried from 60% to 20% moisture (by weight). The mass of moisture removed in kg is |
| A. | 520 |
| B. | 200 |
| C. | 400 |
| D. | 500 |
| Answer» D. 500 | |
| 490. |
Maximum heat transfer rate is obtained in __________ flow. |
| A. | Laminar |
| B. | Turbulent |
| C. | Creeping |
| D. | Transition region |
| Answer» C. Creeping | |
| 491. |
LMTD correction factor which is to be applied for a cross-flow heat exchanger increases with increase in the number of shell passes. Its value for a single pass cross flow heat exchanger is |
| A. | 0 |
| B. | 1 |
| C. | >1 |
| D. | <1 |
| Answer» E. | |
| 492. |
Sensible heat of hot industrial flue gases can not be recovered by a/an |
| A. | Economiser |
| B. | Regenerator |
| C. | Ceramic recuperator |
| D. | None of these |
| Answer» E. | |
| 493. |
In a boiling curve, the peak heat flux is called the __________ point. |
| A. | Nusselt |
| B. | Leidenfrost |
| C. | Boiling |
| D. | Burnout |
| Answer» E. | |
| 494. |
(NRe.NPr)(D/L) is called the __________ number |
| A. | Peclet |
| B. | Stanton |
| C. | Graetz |
| D. | None of these |
| Answer» D. None of these | |
| 495. |
Maximum heat transfer rate is achieved in __________ flow. |
| A. | Co-current |
| B. | Counter-current |
| C. | Turbulent |
| D. | Laminar |
| Answer» D. Laminar | |
| 496. |
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 | |
| 497. |
Tubes are held between top and bottom tube sheets in Calenderia type evaporator by keeping |
| A. | Both the tube sheets fixed |
| B. | Both the tube sheets floating |
| C. | The top tube sheet floating and bottom tube sheet fixed |
| D. | The top tube sheet fixed and the bottom tube-sheet floating |
| Answer» B. Both the tube sheets floating | |
| 498. |
A perfect black body is a perfect __________ of radiation. |
| A. | Absorber |
| B. | Emitter |
| C. | Both A & B |
| D. | Neither A nor B |
| Answer» D. Neither A nor B | |
| 499. |
Reynold's analogy states that |
| A. | Nst α f |
| B. | Nst α NRe |
| C. | NNu α f |
| D. | NRe α f |
| Answer» B. Nst α NRe | |
| 500. |
For hot feed, forward feeding as compared to backward feeding results in __________ economy. |
| A. | Increased |
| B. | Decreased |
| C. | No effect on |
| D. | None of these |
| Answer» B. Decreased | |