Test: Radiation - 1 - Mechanical Engineering MCQ
20 Questions MCQ Test - Test: Radiation - 1
Common Data for Questions
Radiative heat transfer is intended between the inner surfaces of two very large isothermal parallel metal plates. While the upper plate (designated as plate 1) is a black surface and is the warmer one being maintained at 727°C, the lower plate (plate 2) is a diffuse and gray surface with an emissivity of 0.7 and is kept at 227°C.
Assume that the surfaces are sufficiently large to form a two-surface enclosure and steady-state conditions to exist. Stefan-Boltzmann constant is given as 5.67 × 10-8 W/m2K4.
Q. If plate 1 is also a diffuse and gray surface with an emissivity value of 0.8, the net radiation heat exchange (in kW/m2) between plate 1 and plate 2 is:
Radiative heat transfer is intended between the inner surfaces of two very large isothermal parallel metal plates. While the upper plate (designated as plate 1) is a black surface and is the warmer one being maintained at 727°C, the lower plate (plate 2) is a diffuse and gray surface with an emissivity of 0.7 and is kept at 227°C.
Assume that the surfaces are sufficiently large to form a two-surface enclosure and steady-state conditions to exist. Stefan-Boltzmann constant is given as 5.67 × 10-8 W/m2K4.
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Fraction of radiative energy leaving one surface that strikes the othersurface is called
Which one of the following modes of heat transfer would take placepredominantly, from boiler furnace to water wall?
When α is absorbtivity, ρ is reflectivity and τ is transmisivity, then for diathermanous body, which of the following relation is valid?
Consider the diagram given above. Which one of the following is correct?
Assertion (A): The nose of aeroplane is painted black. Reason (R) Black body absorbs maximum heat which is generated byaerodynamic heating when the plane is flying.
Match List-I with List-II and select the correct answer using the code given below the lists:
Two long parallel plates of same emissivity 0.75 are maintained at different temperatures and have radiation heat exchange between them. The radiation shield of emissivity 0.5 placed in the middle will reduce radiation heat exchange to:
Which of the following would lead to a reduction in thermal resistance?
1. In conduction; reduction in the thickness of the material and an increase in the thermal conductivity.
2. In convection, stirring of the fluid and cleaning the heating surface.
3. In radiation, increasing the temperature and reducing theemissivity.
Codes:
Solar radiation of 1200 W/m2 falls perpendicularly on a grey opaquesurface of emissivity 0.5. If the surface temperature is 50°C and surfaceemissive power 600 W/m2, the radiosity of that surface will be:
For an opaque plane surface the irradiation, radiosity and emissive power are respectively 20, 12 and 10 W/m2.What is the emissivity of the surface?
Two large parallel grey plates with a small gap, exchange radiation atthe rate of 1000 W/m2 when their emissivities are 0.5 each. By coatingone plate, its emissivity is reduced to 0.25. Temperature remains unchanged. The new rate of heat exchange shall become:
Match List-I with List-II and select the correct answer using the code given below the Lists:
The shape factor of a hemispherical body placed on a flat surface withrespect to itself is:
What is the value of the shape factor for two infinite parallel surface separated by a distance d?
Intensity of radiation at a surface in perpendicular direction is equalto: [IES-2005; 2007]
Sun's surface at 5800 K emits radiation at a wave-length of 0.5 μm. Afurnace at 300°C will emit through a small opening, radiation at awavelength of nearlyb
Match List-I with List-II and select the correct answer using the code given below the lists:
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