McqMate
| 601. |
Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m2.°C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the |
| A. | Higher condensing film co-efficient is desired |
| B. | Condensate is corrosive in nature |
| C. | Lower pressure drop through the exchanger is desired |
| D. | Temperature of the incoming vapor is very high |
| Answer» B. Condensate is corrosive in nature | |
| 602. |
Viscosity of gases __________ with increase in temperature. |
| A. | Increase very rapidly |
| B. | Increase slowly |
| C. | Decrease slowly |
| D. | Remain unaffected |
| Answer» B. Increase slowly | |
| 603. |
In case of surface condensers, a straight line is obtained on plotting 1/U vs. __________ on an ordinary graph paper. |
| A. | 1/V̅-0.8 |
| B. | V̅-0.8 |
| C. | V̅-2 |
| D. | 1/ V̅-2 |
| Answer» A. 1/V̅-0.8 | |
| 604. |
A cube, sphere & a thin circular plate (all having same mass and made of same material) are all heated to 300°C and allowed to cool in natural air. Which one will cool the slowest? |
| A. | Cube |
| B. | Plate |
| C. | Sphere |
| D. | All will cool at the same rate |
| Answer» C. Sphere | |
| 605. |
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» A. 5 minutes | |
| 606. |
Which of the following material has lest value of thermal diffusivity? |
| A. | Aluminium |
| B. | Rubber |
| C. | Lead |
| D. | Mercury |
| E. | Iron |
| Answer» B. Rubber | |
| 607. |
For a opaque body |
| A. | reflectivity = 0 |
| B. | absorptivity = reflectivity = 1 |
| C. | 37,500 kg |
| D. | absorptivity + reflectivity = 1 |
| E. | absorptivity = 0 |
| Answer» D. absorptivity + reflectivity = 1 | |
| 608. |
In which case the value of thermal conductivity drops with rising temperature |
| A. | Methane |
| B. | Benzene |
| C. | Carbondioxide |
| D. | Ammonia |
| E. | None of the above |
| Answer» E. None of the above | |
| 609. |
Which of the following is used as entrainer in acetic acid - water separation? |
| A. | Butyl acetate |
| B. | Methyl alcohol |
| C. | Benzene. |
| D. | Phosphorous |
| E. | Hexane |
| Answer» A. Butyl acetate | |
| 610. |
Which of the following provides maximum contact surface for a liquid vapour system? |
| A. | Wetted wall column |
| B. | Packed tower |
| C. | Sieve plant column |
| D. | Benzene. |
| E. | Bubble cap tower |
| Answer» A. Wetted wall column | |
| 611. |
The lower temperature limit for mercury thermometer is |
| A. | Absolute zero |
| B. | 0?F |
| C. | ? 39?F |
| D. | 0?C |
| E. | 100?C |
| Answer» C. ? 39?F | |
| 612. |
Cork is a good insulator because |
| A. | It is porous |
| B. | Its density is low |
| C. | It is flexible |
| D. | It can be powdered |
| E. | It can be cast into rolls |
| Answer» A. It is porous | |
| 613. |
The value of thermal conductivity of water at room temperature is expected to be |
| A. | 0.05 kcal/m-hr-?C |
| B. | 0.5 kcal/m-hr-?C |
| C. | 0.001 kcal/m-hr-?C |
| D. | 1.0 kcal/m-hr-?C |
| E. | 1.5 kcal/m-hr-?C |
| Answer» B. 0.5 kcal/m-hr-?C | |
| 614. |
The coefficient of linear expansion of a solid is L. The volume V of a cube of this solid on being heated by 1?C will change by |
| A. | VL |
| B. | VL/3 |
| C. | 3 VL |
| D. | 37,500 kg |
| E. | 3L |
| Answer» C. 3 VL | |
| 615. |
The unit of thermal conductivity in S.I. units is |
| A. | KJ/m-hr-?K |
| B. | KJ/m-hr?C |
| C. | W/m?K |
| D. | W/m-hr?C |
| E. | W/m-hr-?K |
| Answer» C. W/m?K | |
| 616. |
Two rods one of copper and the other of mild steel, both of diameter 20 mm and length 250 mm are coated with a uniform layer of wax all around. These rods are placed vertically in a boiling water bath with 200 mm, length of each rod projecting outside. If the melting point of wax is 10?C, then |
| A. | equal quantity of wax will meet on the two rods |
| B. | more wax will melt on copper rod as compared to mild steel rod |
| C. | 37,500 kg |
| D. | nothing can be predioted as the data is insufficient |
| E. | more wax will melt on mild steel rod as compared to copper rod |
| Answer» B. more wax will melt on copper rod as compared to mild steel rod | |
| 617. |
Oxygen boils at -183?C, this temperature is |
| A. | ? 215?F |
| B. | ? 361?F |
| C. | ? 227?F |
| D. | ? 329?F |
| E. | ? 398?F |
| Answer» C. ? 227?F | |
| 618. |
Heat is transferred from an electric bulb mainly by |
| A. | Conduction, convection and radiation. |
| B. | Radiation |
| C. | Convection and conduction |
| D. | Convection |
| E. | Conduction |
| Answer» B. Radiation | |
| 619. |
The average value of thermal conductivity for air at 20?C is about |
| A. | 0.11 |
| B. | 0.011 |
| C. | 0.022 |
| D. | None of the above |
| E. | Nichrome |
| Answer» C. 0.022 | |
| 620. |
A vapour containing liquid particles to the extent of 50% by the volume is known as |
| A. | Saturate vapour |
| B. | Superheated vapour |
| C. | Super saturated liwuid |
| D. | Wet vapour |
| E. | Saturated liquid |
| Answer» D. Wet vapour | |
| 621. |
Ice is slippery when a man walks on it for |
| A. | There is no friction |
| B. | Increase of pressure causes it to melt |
| C. | It is very chill |
| D. | Its surface is smooth |
| E. | It has lubricating qualities |
| Answer» B. Increase of pressure causes it to melt | |
| 622. |
The total solar radiation incident on a body is 1000 kcal/min. The body reflects 400 kcal/min. If the transmissivity of the surface will be |
| A. | 0.85 |
| B. | 0.3 |
| C. | 0.45 |
| D. | 0.15 |
| E. | 0.4 |
| Answer» C. 0.45 | |
| 623. |
The nature of flow of a fluid inside a tube i.e., whether it is turbulent or laminar, is ascertained by |
| A. | Viscosity of fluid |
| B. | Flow velocity |
| C. | Surface conditions |
| D. | Tube size |
| E. | Reynolds number |
| Answer» E. Reynolds number | |
| 624. |
When metallic surfaces are oxidized the emissivity |
| A. | Depends on the temperature |
| B. | Depends on other factors |
| C. | Decreases |
| D. | Does not change |
| E. | Increases |
| Answer» E. Increases | |
| 625. |
For which fluid combination the value of overall heat transfer coefficient will be least? |
| A. | Alcohol condensers |
| B. | Air to heavy tars |
| C. | Feed water heaters |
| D. | 37,500 kg |
| E. | Air condensers |
| Answer» B. Air to heavy tars | |
| 626. |
The rate of heat flow between a solid wall and a fluid (in contact with a solid wall) is given by |
| A. | Wein's Law |
| B. | Kirchhoff's law |
| C. | Newton-Rikhman's Law |
| D. | None of the above |
| E. | Nichrome |
| Answer» C. Newton-Rikhman's Law | |
| 627. |
Radio active nuclear waste is treated in |
| A. | Pulsed column extractor |
| B. | Mixer settler extractor |
| C. | Sieve plate extraction column |
| D. | Bollman extractor |
| E. | None of the above |
| Answer» A. Pulsed column extractor | |
| 628. |
In which case does the thermal conductivity increase from left to right? |
| A. | Aluminium, silver, copper |
| B. | 37,500 kg |
| C. | Aluminium, copper, silver |
| D. | Silver, copper, aluminium |
| E. | Copper, silver, aluminium |
| Answer» C. Aluminium, copper, silver | |
| 629. |
If two systems are being compared on the basis of temperature and heat flux, the similarity being considered is |
| A. | 37,500 kg |
| B. | thermal similarity |
| C. | dynamic similarity |
| D. | geometrical similarity |
| E. | kinematic similarity |
| Answer» B. thermal similarity | |
| 630. |
Thermal conductivity of air at room temperature in kcal/m-hr-?C is nearly |
| A. | 0.1 |
| B. | 0.001 |
| C. | 0.005 |
| D. | 0.05 |
| E. | 0.01 |
| Answer» A. 0.1 | |
| 631. |
Steam traps are used to |
| A. | Heat steam |
| B. | Remove condensate |
| C. | Balance the pressure |
| D. | Regulate the flow |
| E. | Add moisture |
| Answer» B. Remove condensate | |
| 632. |
?40?C is equivalent to |
| A. | ? 40?K |
| B. | 172?R |
| C. | ? 40?F |
| D. | 273?K |
| E. | 500?R |
| Answer» C. ? 40?F | |
| 633. |
The temperature inside a furnace is generally measured by |
| A. | Mercury thermometer |
| B. | Alcohol thermometer |
| C. | Gas thermometer |
| D. | Optical pyrometer |
| E. | Any of the above |
| Answer» D. Optical pyrometer | |
| 634. |
At all wavelengths and temperatures the monochromatic emissivity of a white body is equal to |
| A. | Zero |
| B. | Unity |
| C. | 0.1 to 0.5 |
| D. | 0.5 |
| E. | 0.5 to 1 |
| Answer» A. Zero | |
| 635. |
If the bubbles formed on a submerged hot surface get absorbed in the mass of liquid, the process of boiling is termed as |
| A. | Nucleate boiling |
| B. | Film boiling |
| C. | Pool boiling |
| D. | Any of the above |
| E. | None of the above |
| Answer» C. Pool boiling | |
| 636. |
The rate of radiant energy, which is emitted by a surface at any temperature and in small wavelength is found from the known rate of energy, which under the same condition would be emitted from a black surface by multiplying with the absorptivity. Above enunciation is known as |
| A. | Planck's law |
| B. | Kirchhoff's law |
| C. | Stefan Boltzman law |
| D. | Lambert rule |
| E. | None of the above |
| Answer» E. None of the above | |
| 637. |
A radiation shield should have |
| A. | low reflectivity |
| B. | high reflectivity |
| C. | high emissivity |
| D. | None of the above |
| E. | 37,500 kg |
| Answer» B. high reflectivity | |
| 638. |
In heat exchanger design, one transfer unit means |
| A. | Condition when the change in temperature of 1?C numerically equals the average driving force. |
| B. | The equivalent length of tubes in case the heat exchange was for a temperature difference of 1?C |
| C. | One fluid exchanging with another fluid of the same chemical composition |
| D. | The section of heat exchanger where heat transfer surface area is one square metre |
| E. | The section of heat exchanger which will cause temperature drop of one degree centigrade |
| Answer» A. Condition when the change in temperature of 1?C numerically equals the average driving force. | |
| 639. |
A 1-2 heat exchanger means |
| A. | Single pass on shell side and double pass on tube side |
| B. | Single pass on tube side and double pass on shell side |
| C. | Two tubes of hot fluid pass through one tube of cold tube |
| D. | Single liquid cools two liwuids at different temperatures |
| E. | Two tubes of cold fluid pass through one tube of hot fluid |
| Answer» A. Single pass on shell side and double pass on tube side | |
| 640. |
When a body is in thermal equilibrium with its surroundings, the absorptivity and the emissivity of the body are same. This Law is known as |
| A. | Wein's Law |
| B. | Kirchhoff's law |
| C. | Stefan Boltzmann's law |
| D. | None of the above |
| E. | Nichrome |
| Answer» B. Kirchhoff's law | |
| 641. |
The process of separation of solutes of different molecular sizes in a liquid solution by use of a sutable membrane is known as |
| A. | Hyper sorption |
| B. | Leaching |
| C. | Adsorption |
| D. | Dialysis |
| E. | Distillation |
| Answer» D. Dialysis | |
| 642. |
The propose of using multiple pass heat exchangers is to |
| A. | Increase pressure drop |
| B. | Increase the rate of heat transfer |
| C. | Neutralise viscous friction |
| D. | Reduce pressure drop |
| E. | Reduce fluid flow friction losses |
| Answer» B. Increase the rate of heat transfer | |
| 643. |
The range of diffusivity of gases in cm2/sec at atmospheric pressure is |
| A. | 10 to 5 |
| B. | More than 10 |
| C. | 5 to 1 |
| D. | Less than 1 |
| E. | 1 |
| Answer» D. Less than 1 | |
| 644. |
Four identical copper cubes are painted with different paints. Now if all the cubes are heated to the same temperature and are left in vacuum, which cube will lose heat more rapidly? The colours of the cubes are |
| A. | Pale blue |
| B. | 37,500 kg |
| C. | Shiny black |
| D. | Dull red |
| E. | shiny white |
| Answer» C. Shiny black | |
| 645. |
In case of ideal mono-atomic gas, the ratio of specific heats would be |
| A. | 1.4 |
| B. | 1.33 |
| C. | 1.41 |
| D. | 1.67 |
| E. | 1 |
| Answer» D. 1.67 | |
| 646. |
Thermal conductivity of glass wool depends on |
| A. | Composition |
| B. | Density |
| C. | Porosity |
| D. | Structure |
| E. | All of the above |
| Answer» E. All of the above | |
| 647. |
The average value of thermal conductivity for water at 20?C is about |
| A. | 0.13 |
| B. | 0.32 |
| C. | 0.51 |
| D. | None of the above |
| E. | Nichrome |
| Answer» C. 0.51 | |
| 648. |
Which one of the following is a very good insulator? |
| A. | A hard wood board |
| B. | A porcelain sheet |
| C. | An asbestos sheet |
| D. | Saw dust |
| E. | None of the above |
| Answer» D. Saw dust | |
| 649. |
A device for transferring heat from one fluid to another is known as |
| A. | Lead |
| B. | Heat exchanger |
| C. | Radiation |
| D. | Condenser |
| E. | Evaporator |
| Answer» B. Heat exchanger | |
| 650. |
Which insulating material is suitable for low temperature applications? |
| A. | 85% magnesia |
| B. | Diatomaceous earth |
| C. | Fused alumina bricks |
| D. | Cork |
| E. | Asbestos paper |
| Answer» B. Diatomaceous earth | |
| 651. |
Steady state heat transfer occurs when |
| A. | The flow of heat is uniform |
| B. | The flow of heat is uniformly increasing |
| C. | The flow of heat is uniformly decreasing |
| D. | The flow of heat is negligible |
| E. | The flow of heat is independent of time |
| Answer» C. The flow of heat is uniformly decreasing | |
| 652. |
Which of the following material has thermal conductivity closest to silver? |
| A. | Steel |
| B. | 37,500 kg |
| C. | Aluminium |
| D. | Brass |
| E. | Copper |
| Answer» E. Copper | |
| 653. |
A constant gas thermometer is based on |
| A. | Avogadro's law |
| B. | Graham's law |
| C. | Charle's law |
| D. | Boyle's law |
| E. | 37,500 kg |
| Answer» C. Charle's law | |
| 654. |
Thermal conductivity of liquids can be determined by |
| A. | Guarded plate method |
| B. | Searles method |
| C. | Laby and Hercus method |
| D. | Any of the above |
| E. | None of the above |
| Answer» A. Guarded plate method | |
| 655. |
The temperature of sun can be measured using a |
| A. | radiation pyrometer |
| B. | platinum resistance thermometer |
| C. | standard thermometer |
| D. | mercury thermometer |
| E. | 37,500 kg |
| Answer» A. radiation pyrometer | |
| 656. |
Any of the following could be the unit for Stefan Boltzmann constant EXCEPT |
| A. | cal / cm2-sec-k4 |
| B. | BTU/ft2-hr-R4 |
| C. | W / m2k4 |
| D. | 37,500 kg |
| E. | erg / cm-k4 |
| Answer» E. erg / cm-k4 | |
| 657. |
Which one of the following approximates to the black body condition? |
| A. | Ice |
| B. | Water |
| C. | Lamp black |
| D. | All of the above |
| E. | None of the above |
| Answer» D. All of the above | |
| 658. |
Heat is shown to be closely related to |
| A. | Energy |
| B. | Momentum |
| C. | Temperature |
| D. | Waveform |
| E. | A fluid |
| Answer» C. Temperature | |
| 659. |
Which of the following method is used for finding the thermal conductivity of rubber? |
| A. | Lec's disc method |
| B. | Searles method |
| C. | Cylindrical shell method |
| D. | Laby and Hercus method |
| E. | Any of the above |
| Answer» A. Lec's disc method | |
| 660. |
The ratio of thermal conductivity of copper to that of brass is nearly |
| A. | 37,500 kg |
| B. | 8 |
| D. | 4 |
| E. | 2 |
| Answer» D. 4 | |
| 661. |
The relation between the emissive and absorptive power of a surface is developed under |
| A. | Electrical analogy |
| B. | Stefan-Baltzmann's law |
| C. | Planck's law |
| D. | Kirchhoff's law |
| E. | Law of radiations |
| Answer» D. Kirchhoff's law | |
| 662. |
In air prelieater for boiler heat is least transferred by |
| A. | Convection |
| B. | Conduction, convection and radiation. |
| C. | Conduction and convection |
| D. | Conduction |
| E. | Radiation |
| Answer» E. Radiation | |
| 663. |
The rate of heat loss through a furnace wall is 1000 kcal per hour when inside temperature is 1000?C and outside wall temperature is 500?C. What should be the wall thickness in case the thermal conductivity of wall material is 0.5 kcal/m-hr?C |
| A. | 25 cm |
| B. | 12.5 cm |
| C. | 50 cm |
| D. | 60 cm |
| E. | 40 cm |
| Answer» A. 25 cm | |
| 664. |
Non-isotropic conductivity is exhibited in case of |
| A. | Steel |
| B. | Wood |
| C. | Copper |
| D. | Lead |
| E. | Brass |
| Answer» B. Wood | |
| 665. |
What energy transformation takes place when ice and salt mixture is converted into water |
| A. | Heat energy to sensible heat |
| B. | Kinetic energy to heat energy |
| C. | Heat energy to latent heat |
| D. | Heat energy to potential energy |
| E. | Heat energy to kinetic energy |
| Answer» C. Heat energy to latent heat | |
| 666. |
The rate of energy stored in the wall will be |
| A. | 50 kcal/sec |
| B. | 50 kcal/min |
| C. | 200 kcal/min |
| D. | 50 kcal/hr |
| E. | 200 kcal/hr |
| Answer» C. 200 kcal/min | |
| 667. |
Pyrometer which react to all wavelengths of incident radiant energy are known as |
| A. | Multicolour pyrometers |
| B. | Total radiation pyrometers |
| C. | Polarising pyrometers |
| D. | Optical pyrometers |
| E. | Ddisappearing filament type pyrometers |
| Answer» B. Total radiation pyrometers | |
| 668. |
A relationship between the temperature of a black body and the wavelength at which the maximum value of monochromatic emission power occurs, is established under |
| A. | D' lambert's rule |
| B. | Stefan-Bolzmann's law |
| C. | Planck's law |
| D. | Wein's displacement law |
| E. | Kirchhoff's law |
| Answer» D. Wein's displacement law | |
| 669. |
In case of white body, absorptivity is |
| A. | Between 0 to 0.5 |
| B. | 1 |
| C. | Zero |
| D. | More than 0.5 |
| E. | 37,500 kg |
| Answer» C. Zero | |
| 670. |
Two parallel opposed, infinite black planes are maintained at 300?C and 400?C respectively. If the temperature difference is doubled by increasing the temperature from 400?C to 500?C, the heat exchange rate will increase by a factor of about |
| A. | 2.5 |
| B. | 5.5 |
| C. | 8.75 |
| D. | 6.25 |
| E. | 4.5 |
| Answer» A. 2.5 | |
| 671. |
The overall co-efficients of heat transfer is used in the problems of |
| A. | convection |
| B. | conduction |
| C. | radiation |
| D. | conduction and convection |
| E. | Nichrome |
| Answer» D. conduction and convection | |
| 672. |
Identity the correct statement |
| A. | Only some substances emit radiation |
| B. | A substance will emit radiation at a particular wavelength only |
| C. | Quality and quantity of radiation depends on the properties of the material only |
| D. | All substances emit radiation the quality and quantity depends on the absolute temperature and the properties of the material composing the radiating body |
| E. | Bodies black in colour are known as black bodies |
| Answer» D. All substances emit radiation the quality and quantity depends on the absolute temperature and the properties of the material composing the radiating body | |
| 673. |
Baffles are provided in heat exchangers to |
| A. | Provide better mechanical strength |
| B. | Reduce heat transfer rate |
| C. | Reduce vibrations |
| D. | Increase heat transfer rate |
| E. | Remove dirt |
| Answer» D. Increase heat transfer rate | |
| 674. |
Heat sensitive liquids are connected |
| A. | By using insulated vessels |
| B. | By using low intensity heating |
| C. | By using deoxidisers |
| D. | By using small quantities |
| E. | By using vacuum |
| Answer» E. By using vacuum | |
| 675. |
Which sample of concrete may be expected to have highest value of thermal conductivity |
| A. | Dry concrete having 0.4% rein-forcement |
| B. | Concrete having 10% moisture by volume |
| C. | Concrete having 10% meisture by volume and 0.4% reinforcement |
| D. | Dry concrete |
| E. | Concrete having 10% moisture by volume and 0.6% reinforcement |
| Answer» E. Concrete having 10% moisture by volume and 0.6% reinforcement | |
| 676. |
Which rays have the least wavelength? |
| A. | Ultraviolet |
| B. | Cosmic rays |
| C. | Irifrared |
| D. | X-rays |
| E. | Radio |
| Answer» B. Cosmic rays | |
| 677. |
Ditus Boelter equation is applicable in case of fluids flowing in |
| A. | Laminar region |
| B. | Turbulent region |
| C. | Transition region |
| D. | Any of the above |
| E. | None of the above |
| Answer» B. Turbulent region | |
| 678. |
Transmission of heat by molecular collision is |
| A. | Scattering |
| B. | Transmission |
| C. | Radiation |
| D. | Convection |
| E. | Conduction |
| Answer» D. Convection | |
| 679. |
The emissive power of a body depends on |
| A. | Nature of body |
| B. | Temperature of body |
| C. | Physical nature |
| D. | All of the above |
| E. | None of the above |
| Answer» D. All of the above | |
| 680. |
Floating heads are provided in heat exchangers to |
| A. | Facilitate maintenance |
| B. | Regulate the flow |
| C. | Increase the pressure drop |
| D. | Avoid deformation of tubes due to thermal expansion |
| E. | Reduce the pressure drop |
| Answer» D. Avoid deformation of tubes due to thermal expansion | |
| 681. |
The transfer of heat in case of radiation takes place by means of |
| A. | Heated particles of the medium |
| B. | Electromagnetic waves |
| C. | Thermal energy of the source |
| D. | None of the above |
| E. | 37,500 kg |
| Answer» A. Heated particles of the medium | |
| 682. |
In case of liquids and gases, the heat transfer takes place according to |
| A. | radiation |
| B. | conduction |
| C. | convection |
| D. | Both (A) and (C) |
| E. | Nichrome |
| Answer» C. convection | |
| 683. |
Which of the following has the highest value of the thermal conductivity |
| A. | Wood |
| B. | Asbestos |
| C. | Nichrome |
| D. | Clay |
| E. | Refractory brick |
| Answer» C. Nichrome | |
| 684. |
Which of the following is wrong |
| A. | Black surfaces are better absorbers than white ones |
| B. | Black surfaces are better radiators than white ones |
| C. | Rough surfaces are better radiators than smooth surfaces |
| D. | 37,500 kg |
| E. | Highly polished mirror like surfaces are very good radiators |
| Answer» E. Highly polished mirror like surfaces are very good radiators | |
| 685. |
Which of the following are generally diathermanous? |
| A. | Solids |
| B. | Liquids |
| C. | Gases |
| D. | All of the above |
| E. | 37,500 kg |
| Answer» C. Gases | |
| 686. |
Longest wavelength |
| A. | Ultraviolet rays |
| B. | Infrared rays |
| C. | Gamma rays |
| D. | X-rays |
| E. | Radio waves |
| Answer» C. Gamma rays | |
| 687. |
All bodies above absolute zero temperature emit radiation". Above statement is based on |
| A. | D'Alambert's rule |
| B. | Wein's law |
| C. | Stefan law |
| D. | Planck's law |
| E. | Prevost theory |
| Answer» E. Prevost theory | |
| 688. |
Which one of the following will radiate heat to a large extent? |
| A. | White polished surface |
| B. | White rough surface |
| C. | Black rough surface |
| D. | Black polished surface |
| E. | None of the above |
| Answer» A. White polished surface | |
| 689. |
In a cooling tower which mode of heat transfer plays insignificant role? |
| A. | Evaporative cooling |
| B. | Convective cooling |
| C. | Radiaion |
| D. | All of the above |
| E. | 37,500 kg |
| Answer» C. Radiaion | |
| 690. |
A dimensionless number which is the ratio of kinematic viscosity to thermal diffusivity is known as |
| A. | Grashoff number |
| B. | Reynolds number |
| C. | Prandtl number |
| D. | Pacelet number |
| E. | Nusselt number |
| Answer» C. Prandtl number | |
| 691. |
There metal walls of same cross-sectional area having thermal conductivity in the ratio 1 : 2 : 4 transfer heat at the rate of 15000 kcal/hr. For same thickness of wall, the temperature deop will be in the ratio |
| A. | 1 ; 2 ; 4 |
| B. | 1 : |
| D. | 4 ; 2 ; 1 |
| E. | 1 ; 1 ; 1 |
| Answer» B. 1 : | |
| 692. |
Formation of fog is due to |
| A. | High pressure |
| B. | Humidity |
| C. | Temperature fall of atmosphere |
| D. | Low pressure |
| E. | Night showers |
| Answer» C. Temperature fall of atmosphere | |
| 693. |
The radiation from flames consists of |
| A. | Continuous radiation from burning soot particles of microscopic and submicroscopic dimensions |
| B. | Radiation from suspended larger particles of coal, coke or ash contributing to flame luminosity |
| C. | Infrared radiation from water vapour and carboundioxide |
| D. | Non-equilibrium radiation associated with the combustion process |
| E. | All of the above |
| Answer» E. All of the above | |
| 694. |
In a shell and tube heat exchanger, the corrosive liquid is normally passed through |
| A. | Shell side |
| B. | Tube side |
| C. | Either of (A) and (B) above |
| D. | None of the above |
| E. | None of the above |
| Answer» B. Tube side | |
| 695. |
DBA = DAB, in case of |
| A. | Stagnet diffusion |
| B. | Equimolar counter diffusion |
| C. | Either of (A) and (B) above |
| D. | None of the above |
| E. | 2.6 cm2/sec |
| Answer» B. Equimolar counter diffusion | |
| 696. |
Unsaturated vapours |
| A. | Do not obey gas laws |
| B. | Fully obey gas laws |
| C. | Obey Boyle's law but not Charle's law |
| D. | Partly obey gas laws depending upon the degree of unsaturations |
| E. | None of the above |
| Answer» A. Do not obey gas laws | |
| 697. |
A substance above critical temperature exists as |
| A. | Solid |
| B. | Liquid |
| C. | Wet vapour |
| D. | Gas |
| E. | Dry vapour |
| Answer» D. Gas | |
| 698. |
Which dimensionless number indicates the relative strength of the buoyant to viscous forces? |
| A. | Froude's number |
| B. | 37,500 kg |
| C. | Prandtl number |
| D. | Weber number |
| E. | Grashoff number |
| Answer» C. Prandtl number | |
| 699. |
In case the hydrodynamic and thermal boundary layers are identical for a fluid flowing over a heated plate |
| A. | The value of Prandtl number must be 0.5 |
| B. | The plate surface must be smooth |
| C. | The plate must be of low thermal conductivity |
| D. | The value of Prandtl number thust be 1 |
| E. | The value of Prandtl number must be zero |
| Answer» D. The value of Prandtl number thust be 1 | |
| 700. |
A high value of Prandtl number indicates |
| A. | rapid diffusion of momentum by viscous action compared to diffusion of energy |
| B. | relative heat transfer by conduction to convection |
| C. | rapid heat transfer by forced convection to natural convection |
| D. | None of the above |
| E. | 37,500 kg |
| Answer» A. rapid diffusion of momentum by viscous action compared to diffusion of energy | |
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