The heat of sum reaches to us according to
A.radiation
B.conduction
C.convection
D.None of the above
Category: Heat Transfer Mcqs
A wall has two layers A and B, each made of a different material. Both the layers have the same thickness. The thermal conductivity of material of A is twice that of B. Under the thermal equilibrium the temperature difference across the wall is 30?C. The temperature drops in layers A and B will be respectively
A.20?C and 10?C
B.10?C and 20?C
C.15?C and 15?C
D.cannot be predicated
In an air-conditioning plant a cooling tower is used to cool
A.air
B.refrigerant
C.condenser water
D.None of the above
Identity the correct statement
A.Bodies black in colour are known as black bodies
B.Only some substances emit radiation
C.Quality and quantity of radiation depends on the properties of the material only
D.A substance will emit radiation at a particular wavelength only
E.All substances emit radiation the quality and quantity depends on the absolute temperature and the properties of the material composing the radiating body
A constant gas thermometer is based on
A.Avogadro’s law
B.Graham’s law
C.Boyle’s law
D.Charle’s law
The propose of using multiple pass heat exchangers is to
A.Reduce fluid flow friction losses
B.Reduce pressure drop
C.Increase pressure drop
D.Increase the rate of heat transfer
E.Neutralise viscous friction
Grashoff number has significant role in heat transfer by
A.conduction
B.natural connection
C.Forced convection
D.radiation
Prandtl number for liquid metals is generally in the range
A.1000 to 10,000
B.100 to 1000
C.10 to 100
D.0.003 to 0.01
The reflectance of a black body is
A.infinite
B.one
C.less than 1.0
D.zero
Which of the following property of air does not increase with rise in temperature?
A.Specific gravity
B.Specific volume
C.Thermal conductivity
D.Thermal diffusivity
E.Kinematic viscosity
