Thermal conductivity of non-metallic amorphous solid with decrease in temperature
(a) Increase
(b) Decrease
(c) Remain constant
(d) May increase or decrease
Heat transfer takes place as per
(a) Zeroth law of thermodynamics
(b) first law of thermodynamics
(c) Second law of thermodynamics
(d) Kirchoff’s law
Sensible heat is the heat required to
(a) change the vapour into liquid
(b) change the liquid into vapour
(c) increase in temperature of a liquid and vapour
(d) convert the water into steam and super heated vapour
Heat transfer in liquids and gases takes place by
(a) conduction
(b) convection
(c) radiation
(d) conduction and convection
Which of the following is case of steady state heat transfer ?
(a) I.C. Engine
(b) Air pre heater
(c) Heating of building in winter
(d) None of the above
Thermal diffusivity of substance is
(a) proportional to thermal conductivity
(b) inversely proportional to thermal conductivity
(c) Proportional to the square of thermal conductity
(d) Inversely proportional to the squre of thermal conductivity
Film coefficient is defined as
(a) Inside diamter of tube/ Equivalent thickness of film
(b) Thermal conductivity/ Equivalent thickness of film
(c) Specific heat x viscosity/ Thermal conductivity
(d) Film coefficient x inside diameter/ Thermal conductivity
Emissivity of a whtie polished body in comparison to black body is
(a) higher
(b) lower
(c) same
(d) None of the above
LMTD in case of counter flow heat exchanger in comparison to parallel flow heat exchanger is
(a) higher
(b) lower
(c) same
(d) depends on the area of heat exchanger
The numerical value of prandtl number is about
(a) 0.1
(b) 0.3
(c) 0.7
(d) 1.7
All raditions coming on black body
(a) All are reflected
(b) All are transmitted
(c) All are absorbed
(d) All of the above
Which of the following property of air does not increase with rise in temperature ?
(a) Thermal conductivity
(b) Thermal diffusivity
(c) Density
(d) Dynamic viscosity
In free convection heat transfer, Nusselt number is function of
(a) Grashoff no. and Reynold no.
(b) Grashoff’s no. and Prandtl no.
(c) Prandtl no. & Reynold no.
(d) None of the above
The thermal diffusivities for gases are generally
(a) more than liquid
(b) less than liquid
(c) more than solid
(d) depends on viscosity
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