Mechanical Engineering - Heat Transfer, Refrigeration and Air Conditioning - Discussion
Discussion Forum : Heat Transfer, Refrigeration and Air Conditioning - Section 1 (Q.No. 3)
3.
Which of the following statement is wrong?
Discussion:
31 comments Page 1 of 4.
RS RAJPUT said:
1 decade ago
Heat transfer in metal can be,
1. By lattice vibration.
2. By free electron transfer(free electron provide the heat flux in the direction of decreasing temperature).
(Factor two is more dominating to factor one but both act simultaneously).
According to second point. If we increase the temperature of metal these decrease the tendency free moving electron.
These may be reason for decreasing conductivity of metal.
1. By lattice vibration.
2. By free electron transfer(free electron provide the heat flux in the direction of decreasing temperature).
(Factor two is more dominating to factor one but both act simultaneously).
According to second point. If we increase the temperature of metal these decrease the tendency free moving electron.
These may be reason for decreasing conductivity of metal.
Sujit said:
8 years ago
For solids, Thermal Conductivity is dependent on lattice vibrations and movement of free electrons, as temp increases movement of free electrons is hampered by lattice vibrations. So that free electrons provide more resistance to heat flow.
according to Fourier's law of conduction
Q= -k*A*(dT/dx).
k=thermal conductivity of material
A=c/s area
dT= temp. difference
dx=thickness
So, k inversely proportional to dT.
according to Fourier's law of conduction
Q= -k*A*(dT/dx).
k=thermal conductivity of material
A=c/s area
dT= temp. difference
dx=thickness
So, k inversely proportional to dT.
(2)
Ks37 said:
7 years ago
For metals, the thermal conductivity is mainly a function of the motion of free electrons. As the temperature increases, the molecular vibrations increase (in turn decreasing the mean free path of molecules). So, they obstruct the flow of free electrons, thus reducing the conductivity.
(2)
Atif said:
9 years ago
For metals, the thermal conductivity is mainly a function of the motion of free electrons. As the temperature increases, the molecular vibrations increase (in turn decreasing the mean free path of molecules). So, they obstruct the flow of free electrons, thus reducing the conductivity.
Amrit said:
9 years ago
Actually, thermal conductivity varies differently in the different physical state of matter. In solid if temperature increases then thermal conductivity decreases (for). In gas if temperature increases thermal conductivity increases. And for liquid, it depends on upon the temperature.
Friend said:
10 years ago
Just remember that perfect conduction can be achieved at sub zero temperature state called superconducting that means as the temperature decreases conductivity increases. Hence it would be easy to remember that as temperature increases conductivity decreases.
Friend said:
10 years ago
Just remember that perfect conduction can be achieved at sub zero temperature state called superconducting that means as the temperature decreases conductivity increases. Hence it would be easy to remember that as temperature increases conductivity decreases.
Jaya krishna said:
1 decade ago
For solids Thermal Conductivity is dependent on lattice vibrations and movement of free electrons, as temp increases movement of free electrons is hampered by lattice vibrations.
SAIKUMAR said:
1 decade ago
In solids the molecules are closely packed. The heat transfer more because this arrangement. Hence the conductivity increases with increases with increase in temperature.
Rahul raja said:
9 years ago
As the resistance is more in the path of a solid body there will be more collision due to which thermal conductivity of solid decreases.
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