Question

why thermal conductivity decreases when the temperature difference increases

Answer #1

Ans :

The thermal conductivity of substances is dependent on various factors such as : chemical composition , phase change , temperature etc.

When the temperature of a metal is increased , the mean free path of the molecules decreases. The thermal conductivity directly relates with the mean free path and absolute temperature.

This causes a decrease in the conduction of heat , so the the thermal conductivity decreases when the temperature difference increases.

Why does the conductivity of a semiconductor increase with
increased temperature, but a metal’s conductivity decreases?

Why viscosity of gasses increases with temperature where as
viscosity of liquid decreases with temperature?
Please
Explain

To determine the effect of the temperature dependence of the
thermal conductivity on the temperature distribution in a solid,
consider a material for which this dependence may be represented
by: k = k0 + a T, where “k0“ is a positive constant and “a” is a
coefficient that may be positive or negative. Starting with a
steady-state energy balance, derive a relationship for temperature
(T) as a function of distance (x) from the lower temperature wall.
You may assume that...

Rod 1, with a thermal conductivity of 373 W/m·K, rod 2, with a
thermal conductivity of 292 W/m·K, and rod 3, with a thermal
conductivity of 112 W/m·K, are placed end to end with rod 2 between
the other two. The rods have the same length and the same diameter.
The free end of rod 1 is maintained at water's boiling point, and
the free end of rod 3 is maintained at water's freezing point. What
is the steady-state temperature...

Explain why gases experience more ideal behavior as temperature
increases and pressure decreases.

Determination of Thermal Conductivity. In
determining the thermal conductivity of an insulating material, the
temperatures were measured on both sides of a flat slab of 25 mm of
the material and were 318.4 and 303.2 K. The heat flux was measured
as 35.1 W/m^2. Calculate the thermal conductivity in
btu/h*ft*Fahrenheit and in W/m*Kelvins

The thermal conductivity of a sheet of rigid,extruded insulation
is k = 0.020 W/(m*K). The measured temperature difference across a
30-mm-thick sheet of the material is T1-T2=10 C.
a.) Assuming 1-D, steady state conditions withouth thermal
energy generation in the material, what is the heat flux through a
2 m x 3 m sheet of the insulation?
b.) What would be the effect on the rate of heat transfer
through the sheet if a material with a relatively higher thermal...

As materials heat the thermal influences increase. What are the
implications of thermal conductivity of the skin of an aircraft
that flies supersonically?

A certain material has a thermal conductivity of 0.90 W/(m
oC). If the area of a wall made of the material is 20
m2, the thickness of the wall is 0.6 m, and the heat
transfer through that wall by conduction is 400 W, what is the
temperature difference between the surfaces of the wall? Give your
answer in terms of oC . (Enter the number only -- do not
include the units in your answer.)

A stainless steel pipe [thermal conductivity = 17 W/(m.C)] is
being used to convey heated oil. The inside surface temperature is
13 degrees C. The pipe is 2 cm thick with an inside diameter of 8
cm. The pipe is insulated with 0.04m thick insulation [thermal
conductivity = 0.035 W/(m.C)]. The outer insulation temperature is
25 degrees C. Calculate the temperature of the interface between
steel and insulation, assume steady-state conditions.

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