Q = [2πlk (T₁ - T₂)]/2.3 log (r₂/r₁)
Q = 2.3 log (r₂/r₁)/[2πlk (T₁ - T₂)]
Q = [2π (T₁ - T₂)]/2.3 lk log (r₂/r₁)
Q = = 2πlk/2.3 (T₁ - T₂) log (r₂/r₁)
A. Q = [2πlk (T₁ - T₂)]/2.3 log (r₂/r₁)
Thermal conductivity
Thermal diffusivity
Density
Dynamic viscosity
Glass
Water
Plastic
Air
Below which a gas does not obey gas laws
Above which a gas may explode
Below which a gas is always liquefied
Above which a gas will never liquefied
Both the fluids at inlet (of heat exchanger where hot fluid enters) are in their coldest state
Both the fluids at inlet are in their hottest state
Both the fluids at exit are in their hottest state
One fluid is in hottest state and other in coldest state at inlet
h₁ + h₂ + h₃
(h₁.h₂.h₃)1/3
1/h₁ + 1/h₂ + 1/h₃
None of these
Varies with temperature
Varies with the wave length of incident ray
Varies with both
Does not vary with temperature and wave length of the incident ray
Maximum
Minimum
Zero
None of these
Equal to one
Greater than one
Less than one
Equal to Nusselt number
Directly proportional to the surface area of the body
Directly proportional to the temperature difference on the two faces of the body
Dependent upon the material of the body
All of the above
Kirchhoff's law
Stefan's law
Wines law
Planck's law
0
0.5
0.75
1
0.002
0.02
0.01
0.1
Zeroth law of thermodynamics
First law of thermodynamic
Second law of the thermodynamics
Kirchoff's law
In heat exchanger design as a safety factor
In case of Newtonian fluids
When a liquid exchanges heat with a gas
None of the above
Is black in colour
Reflects all heat
Transmits all heat radiations
Absorbs heat radiations of all wave lengths falling on it
Electric heater
Steam condenser
Boiler
Refrigerator condenser coils
Change vapour into liquid
Change liquid into vapour
Increase the temperature of a liquid of vapour
Convert water into steam and superheat it
One
Two
Three
Four
Steam
Solid ice
Melting ice
Water
Irregular surfaces
Nonuniform temperature surfaces
One dimensional cases only
Two dimensional cases only
Conduction
Free convection
Forced convection
Radiation
Absolute temperature
T²
T⁵
T
P = 0, x = 0 and a = 1
P=1, x = 0 and a = 0
P = 0, x = 1 and a = 0
X = 0, a + p = 1 Where a = absorptivity, p = reflectivity, X = transmissivity.
Temperature
Wave length
Physical nature
All of the above
Increases
Decreases
Remain constant
May increase or decrease depending on temperature
Radiators in automobile
Condensers and boilers in steam plants
Condensers and evaporators in refrigeration and air conditioning units
All of the above
0.45
0.55
0.40
0.75
6
9
27
81
Moisture
Density
Temperature
All of the above
Higher
Lower
Same
Depends upon the shape of body