Q.1
Free convection flow depends on
Q.2
The critical thickness of insulation for a sphere is
Q.3
Unit of thermal conductivity in M.K.S. units is
Q.4
In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by
Q.5
Wien’s law states that the wave length corresponding to ________ is proportional to the absolute temperature.
Q.6
The amount of radiation mainly depends on
Q.7
The heat transfer by conduction through a thick cylinder (Q) is given by (where T₁ = Higher temperature, T₂ = Lower temperature, r₁ = Inside radius, r₂ = Outside radius, l = Length of cylinder, and k = Thermal conductivity)
Q.8
Thermal diffusivity of a substance is given by (where h = Thermal diffusivity, ρ = Density of substance, S = Specific heat, and k = Thermal conductivity)
Q.9
40% of incident radiant energy on the surface of a thermally transparent body is reflected back. If the transmissivity of the body be 0.15, then the emissivity of surface is
Q.10
The heat transfer takes place according to
Q.11
In case of liquids and gases, the heat transfer takes place according to
Q.12
Depending on the radiating properties, a body will be opaque when
Q.13
The process of heat transfer from one particle of the body to another is called conduction, when the particles of the body
Q.14
The thermal diffusivities for solids are generally
Q.15
Log mean temperature difference in case of counter flow compared to parallel flow will be
Q.16
Heat transfer by radiation mainly depends upon
Q.17
The transfer of heat by molecular collision is known as
Q.18
According to Kirchoff's law, the ratio of emissive power to absorptivity for all bodies is equal to the emissive power of a
Q.19
Sensible heat factor is given by (where S.H. = Sensible heat, and L.H. = Latent heat)
Q.20
LMTD in case of counter flow heat exchanger as compared to parallel flow heat exchanger is
Q.21
The automobile radiator is a heat exchanger of
Q.22
A grey body is one whose absorptivity
Q.23
In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the
Q.24
According of Kirchhoff's law
Q.25
Thermal conductivity of wood depends on
Q.26
The rate of energy emission from unit surface area through unit solid angle, along a normal to the surface, is known as
Q.27
Which of the following is the case of heat transfer by radiation?
Q.28
The ratio of the energy absorbed by the body to total energy falling on it is called
Q.29
Absorptivity of a body will be equal to its emissivity
Q.30
In a heat exchanger with one fluid evaporating or condensing, the surface area required is least in
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