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.
| 701. |
The actual temperature drop across the heating surface of an evaporator depends on the |
| A. | Liquid depth over the heating surface |
| B. | Solution being evaporated |
| C. | Pressure difference between the steam chest and the vapor space above the boiling liquid |
| D. | All of the above |
| Answer» E. | |
| 702. |
Boiling of milk in an open vessel is an example of __________ boiling. |
| A. | Film |
| B. | Sub-cooled |
| C. | Saturated nucleate |
| D. | None of these |
| Answer» B. Sub-cooled | |
| 703. |
Evaporator tubes are generally |
| A. | Horizontal |
| B. | Vertical |
| C. | Inclined |
| D. | Random |
| Answer» C. Inclined | |
| 704. |
Which of the following is directly concerned with the heat transfer? |
| A. | Strouhal number |
| B. | Sherwood number |
| C. | Euler number |
| D. | Grashoff number |
| Answer» E. | |
| 705. |
Evaporation by thermocompression results in the |
| A. | Saving of steam |
| B. | Realisation of multiple effect economy in a single effect |
| C. | Both A and B |
| D. | None of these |
| Answer» D. None of these | |
| 706. |
Among liquids, water has a comparatively high value of thermal conductivity, due to its |
| A. | Low density |
| B. | High viscosity |
| C. | Partial ionisation |
| D. | Dense structure |
| Answer» D. Dense structure | |
| 707. |
For a counter current heat exchanger with Tih = 80°C, T°c = 60°C, T°h = 50°C and Tic = 30°C, and the temperature difference between the two streams being the same everywhere along Z, the direction of flow of hot fluid. The temperature profile should satisfy |
| A. | d²T/dZ² > 0 |
| B. | d²T/dZ² = 0 |
| C. | d²T/dZ² < 0 |
| D. | dT/dZ = 0 |
| Answer» C. d²T/dZ² < 0 | |
| 708. |
Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100°C and the inside heat transfer co-efficient is 3k/l. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade? |
| A. | 35.5 |
| B. | 43.75 |
| C. | 81.25 |
| D. | 48.25 |
| Answer» D. 48.25 | |
| 709. |
Harmonic mean temperature difference is given by |
| A. | √(ΔT₁ . ΔT₂) |
| B. | 2.(ΔT₁ . ΔT₂)/(ΔT₁ + ΔT₂) |
| C. | 2.(ΔT₁ . ΔT₂)(ΔT₁ - ΔT₂) |
| D. | (ΔT₁ - ΔT₂)/(ΔT₁ . ΔT₂) |
| Answer» C. 2.(ΔT₁ . ΔT₂)(ΔT₁ - ΔT₂) | |
| 710. |
A multiple effect evaporator has a capacity to process 4000 kg of solid caustic soda per day, when it is concentrating from 10% to 25% solids. The water evaporated in kg per day is |
| A. | 6000 |
| B. | 24000 |
| C. | 60000 |
| D. | 48000 |
| Answer» C. 60000 | |
| 711. |
For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus-Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of |
| A. | 1 |
| B. | 1.74 |
| C. | 6.1 |
| D. | 37 |
| Answer» D. 37 | |
| 712. |
Multiple effect evaporation is generally recommended, when the |
| A. | Large scale evaporation of liquor is needed |
| B. | Corrosive liquids are to be concentrated |
| C. | Fuel is cheaply available |
| D. | Evaporation on small scale is to be done |
| Answer» B. Corrosive liquids are to be concentrated | |
| 713. |
Log mean temperature difference (LMTD) cannot be used, if |
| A. | Heat transfer co-efficient over the entire heat exchanger is not constant |
| B. | There exists an unsteady state |
| C. | The heat capacity is not constant and there is a phase change |
| D. | None of these |
| Answer» E. | |
| 714. |
The statement that "maximum wavelength of radiation is inversly proportional to the temperature" is __________ law. |
| A. | Stefan-Boltzman's |
| B. | Planck's |
| C. | Wien's displacement |
| D. | None of these |
| Answer» D. None of these | |
| 715. |
The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is |
| A. | 1.66 |
| B. | 88.66 |
| C. | 3.66 |
| D. | Dependent on NRe only |
| Answer» D. Dependent on NRe only | |
| 716. |
In Joule's experiment, an insulated container contains 20 kg of water initially at 25°C. It is stirred by an agitator, which is made to turn by a slowly falling body weighing 40 kg through a height of 4 m. The process is repeated 500 times. The acceleration due to gravity is 9.8 ms⁻². Neglecting the heat capacity of agitator, the temperature of water (in °C) is |
| A. | 40.5 |
| B. | 34.4 |
| C. | 26.8 |
| D. | 25 |
| Answer» C. 26.8 | |
| 717. |
Three solid objects of the same material and of equal mass-a sphere, a cylinder (length = diameter) and a cube are at 500°C initially. These are dropped in a quenching bath containing a large volume of cooling oil each attaining the bath temperature eventually. The time required for 90% change in temperature is the smallest for |
| A. | Cube |
| B. | Cylinder |
| C. | Sphere |
| D. | Equal for all the three |
| Answer» B. Cylinder | |
| 718. |
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 | |
| 719. |
Nusselt number is the ratio of the |
| A. | Temperature gradient of the wall to that across the entire pipe |
| B. | Temperature difference to the temperature gradient at the wall |
| C. | Heat flux at the wall to that across the entire pipe |
| D. | None of these |
| Answer» D. None of these | |
| 720. |
The purpose of providing expansion bellows in the shell of tubular exchanger is to |
| A. | Increase the heating load |
| B. | Impart structural strength |
| C. | Account for the uneven expansion of shell and tube bundles |
| D. | Facilitate increase of shell length, if needed |
| Answer» D. Facilitate increase of shell length, if needed | |
| 721. |
The advantage of using a 1 - 2 shell and tube heat exchanger over a 1 - 1 shell and tube heat exchanger is |
| A. | Lower tube side pressure drop |
| B. | Lower shell side pressure drop |
| C. | Higher tube side heat transfer co-efficient |
| D. | Higher shell side heat transfer co-efficient |
| Answer» D. Higher shell side heat transfer co-efficient | |
| 722. |
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 = 5.67xl0⁻⁸ W/m².K⁴) |
| A. | 1000 |
| B. | 727 |
| C. | 800 |
| D. | 1200 |
| Answer» B. 727 | |
| 723. |
A fluid is flowing inside the inner tube of a double pipe heat exchanger with diameter 'd'. For a fixed mass flow rate, the tube side heat transfer co-efficient for turbulent flow conditions is proportional to |
| A. | D0.8 |
| B. | D-0.2 |
| C. | D-1 |
| D. | D-1.8 |
| Answer» C. D-1 | |
| 724. |
h.D/K is called the __________ number. |
| A. | Nusselt |
| B. | Peclet |
| C. | Rayleigh |
| D. | Grashoff |
| Answer» B. Peclet | |
| 725. |
(NGr x NPr) is called the __________ number. |
| A. | Graetz |
| B. | Reyleigh |
| C. | Nusselt |
| D. | Stanton |
| Answer» C. Nusselt | |
| 726. |
The ratio of kinematic viscosity to thermal diffusivity is called the __________ number. |
| A. | Peclet |
| B. | Prandtl |
| C. | Stanton |
| D. | Nusselt |
| Answer» C. Stanton | |
| 727. |
The ratio of velocity head to tube side return loss in case of a multipass shell and tube heat exchanger is |
| A. | 2 |
| B. | 1/2 |
| C. | 4 |
| D. | 1/4 |
| Answer» E. | |
| 728. |
Boiling point elevation of an ideal solution |
| A. | Increases rapidly with temperature rise |
| B. | Decreases rapidly with temperature rise |
| C. | In independent of pressure |
| D. | Both B and C |
| Answer» B. Decreases rapidly with temperature rise | |
| 729. |
A steel sphere of radius 0.1 m at 400°K is immersed in an oil at 300°K. If the centre of the sphere reaches 350°K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions ? Assume that the conductive heat transfer co-efficient is infinitely large. |
| A. | 5 minutes |
| B. | 10 minutes |
| C. | 20 minutes |
| D. | 40 minutes |
| Answer» B. 10 minutes | |
| 730. |
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 | |
| 731. |
In a backward feed multiple effect evaporator |
| A. | Feed is introduced in the first effect |
| B. | Feed flows from low pressure to high pressure |
| C. | No pumps are required between successive effects |
| D. | None of these |
| Answer» C. No pumps are required between successive effects | |
| 732. |
Dropwise condensation is promoted on a/an __________ surface. |
| A. | Glazed |
| B. | Oily |
| C. | Coated |
| D. | Smooth |
| Answer» C. Coated | |
| 733. |
Film condensation is promoted on a/an __________ surface. |
| A. | Oily |
| B. | Coated |
| C. | Clean & smooth |
| D. | Dirty |
| Answer» D. Dirty | |
| 734. |
Fruit juice (a heat sensitive material) can be concentrated in a __________ evaporator. |
| A. | Long tube |
| B. | Falling film |
| C. | High pressure |
| D. | None of these |
| Answer» C. High pressure | |
| 735. |
In a single effect evaporator, the economy is |
| A. | 1 |
| B. | < 1 |
| C. | > 1 |
| D. | None of these |
| Answer» C. > 1 | |
| 736. |
If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface tempeature follows __________ law. |
| A. | Parabolic |
| B. | Hyperbolic |
| C. | Linear |
| D. | Logarithmic |
| Answer» B. Hyperbolic | |
| 737. |
What is the geometric mean of two heat transfer areas A₁ and A₂ ? |
| A. | √(A₁ . A₂) |
| B. | √(A₁ + A₂) |
| C. | 1/2 √(A₁ . A₂) |
| D. | 2 √(A₁ . A₂) |
| Answer» B. √(A₁ + A₂) | |
| 738. |
Baffles are provided in heat exchangers to increase the |
| A. | Fouling factor |
| B. | Heat transfer area |
| C. | Heat transfer co-efficient |
| D. | Heat transfer rate |
| Answer» D. Heat transfer rate | |
| 739. |
Conductance is given by(where, x = thickness, A = heat flow area, K = thermal conductivity.) |
| A. | X/KA |
| B. | KA/x |
| C. | K/Ax |
| D. | A/Kx |
| Answer» C. K/Ax | |
| 740. |
Conduction occurs in the buffer zone for a fluid flowing through a heated pipe, only when Prandtl number is |
| A. | 0.1 |
| B. | >1 |
| C. | < 1 |
| D. | L |
| Answer» B. >1 | |
| 741. |
Calburn analogy is applicable for the value of Prandtl number from |
| A. | 0.001 to 1 |
| B. | 0.6 to 120 |
| C. | 0.5 to 5 |
| D. | 120 to 400 |
| Answer» C. 0.5 to 5 | |
| 742. |
Prandtl and Reynolds analogy are same, when Prandtl number is |
| A. | 0.5 |
| B. | 1 |
| C. | > 2 |
| D. | 1.5 |
| Answer» C. > 2 | |
| 743. |
For what value of Prandtl number, St = f/2? |
| A. | 1.5 |
| B. | 1 |
| C. | > 1 |
| D. | < 1 |
| Answer» C. > 1 | |
| 744. |
The average heat transfer co-efficient over the entire length of the plate (ha) and the local heat transfer co-efficient (hL), in case of heat transfer over a flat plate in lminar zone is related as |
| A. | Ha = 0.8hL |
| B. | Ha = 2hL |
| C. | Ha = hL |
| D. | Ha= 5hL |
| Answer» C. Ha = hL | |
| 745. |
In the free convection regime of pool boiling, the heat flux is proportional to |
| A. | Δt1/2 |
| B. | Δt2 |
| C. | Δt5/4 |
| D. | Δt |
| Answer» D. Δt | |
| 746. |
To reduce the tube side pressure drop for the same flow rate, the heat exchanger recomended is |
| A. | 1-2 heat exchanger |
| B. | 1-1 heat exchanger |
| C. | 3-2 heat exchanger |
| D. | 2-4 heat exchanger |
| Answer» C. 3-2 heat exchanger | |
| 747. |
Unsteady state heat conduction occurs, when |
| A. | Temperature distribution is independent of time |
| B. | Temperature distribution is dependent on time |
| C. | Heat flows in one direction only |
| D. | Three dimensional heat flow is concerned |
| Answer» C. Heat flows in one direction only | |
| 748. |
What is the emissivity of a black body? |
| A. | 1 |
| B. | 0 |
| C. | 0.90 |
| D. | 0.5 |
| Answer» B. 0 | |
| 749. |
Stefen's block body radiation law can also be derived from __________ law. |
| A. | Kirchoffs |
| B. | Planck's |
| C. | Fourier's |
| D. | None of these |
| Answer» C. Fourier's | |
| 750. |
In natural convection heat transfer, the correlating parameter is the |
| A. | Graetz number |
| B. | Eckert number |
| C. | Grashoff number |
| D. | Bond number |
| Answer» D. Bond number | |