HEAT AND MASS TRANSFER QUIZ

Fourier's law of heat conduction is (where Q = Amount of heat flow through the body in unit time, A = Surface area of heat flow, taken at right angles to the direction of heat flow, dT = Temperature difference on the two faces of the body, dx = Thickness of the body, through which the heat flows, taken along the direction of heat flow, and k = Thermal conductivity of the body)

k. (dT/dx)

k. A. (dx/dT)

k. A. (dT/dx)

k. (dx/dT)

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Depending on the radiating properties, a body will be white when(Where a = absorptivity, p = reflectivity, x = transmissivity)

P=1, T = 0 and a = 0

P = 0, x = 0 and a = 1

X = 0, a + p = 1

P = 0, x = 1 and a = 0

TRUE ANSWER : ?
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Sensible heat factor is given by (where S.H. = Sensible heat, and L.H. = Latent heat)

S.H/(L.H - S.H)

S.H/(S.H + L.H)

(S.H + L.H) /S.H

(L.H - S.H)/S.H

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The insulation ability of an insulator with the presence of moisture would

Remain unaffected

May increase/decrease depending on temperature and thickness of insulation

Decrease

Increase

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The highest thermal diffusivity is of

Iron

Lead

Concrete

Wood

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According to Kirchoff's law, the ratio of emissive power to absorptivity for all bodies is equal to the emissive power of a

Brilliant white polished body

Grey body

Black body

Red hot body

TRUE ANSWER : ?
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Thermal conductivity of glass wool varies from sample to sample because of variation in

All of these

Density

Porosity

Composition

TRUE ANSWER : ?
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The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit

Time

Thickness

Temperature

Area

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A grey body is one whose absorptivity

Varies with wavelength of the incident ray

Does not vary with temperature and. wavelength of the incident ray

Varies with temperature

Is equal to its emissivity

TRUE ANSWER : ?
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Unit of thermal conductivity in M.K.S. units is

K calm/hr °C

K cal m/hr m² °C

K cal/hr m² °C

K cal/kg m² °C

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