Heat Transfer - Study Mode
[#491] The absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation.
Correct Answer
(D) May increase or decrease
depends on the material
[#492] With increase in porosity, the thermal conductivity of a solid substance
Correct Answer
(B) Decreases
[#493] With the increase of temperature, the Col-burn jH factor
Correct Answer
(A) Increases
[#494] Thermal conductivities of most of the liquids __________ with rise in temperature.
Correct Answer
(B) Decreases
[#495] The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP) R and the co-efficient of performance as a heat pump (COP) HP are
Correct Answer
(C) (COP) R = 1.5
(COP) HP = 2.5