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1. Thermal conductivity measurement at Cryogenics
Temperature
Prepared by : Sunilkumar Prajapati

2. Research papers
I. Effects of Cryogenic treatment on Thermal conductivity of OFHC
Copper
II. Test of appartus for the Thermal conductivity of superconducting Coils
and material at Cryogenics temperature
III. Thermal conductivity measurement at low temperatures
IV. Cryogenic thermal conductivity measurements on candidate materials
for space missions

3. Effect of cryogenic trearment on OFHC copper
D.S.Nadig et al.
 different machining process causes stress, strain
and dislocation
 which causes the resistance to heat transfer
 thermal conductivity decreases at room
temperature
 as temperature decreases phonon scattering
decreases which increases the thermal
conductivity
 cryotreatment of material in the system shown in
figure
 cryotreated material has reduced stress, strain
and refined atomaic structure
 tempered to reduce strains further

4. Contd.
 system is occupied with solenoid valve
which causes the LN2 to be filled in system
 K = 395 W/mK at room temperature
figure shows laser flash method
absolute method to measure thermal
diffusivity
measures specific heat measured by relative
measurment method in this appartus
sample is insulated from both sides and a
high-intensity short-duration light pulse is
absorbed by the front surface of the sample.

5. Contd.
 Thermal conductivity of OFHC copper
increases with decreasing temperature
 untreated OFHC copper has very low
relative thermal conductivy
 cryotreated copper has better thermal
conductivity
 cryotreated and tempered copper shows
better results at even room temperature
 Difficulty arrived in cryotreatment is
insulation, data accusition system and
leak proof joints.

6. Test of an appartus for Th. conductivity of superconducting
materials ( F. broggi et al.)
 measurement of superconducting coil in temp.
range 4.2 K to 350 K
 Steady state heat axial flow method
 system is maintained about 10^-6 mbar
 immersed in cryogenic fluid
 sealings on flanges are indium rings
 gold plated SS radiation shields are provided to
reduce the radiation loss and gain.
 thermocouples are placed in sample at different
locations.
 temperature gradient is measured
 conductivity calculated using Fourier's law

7. Contd.
 test of appartus done by comparing results
with mathematical models
 TCI - Thermal conductivity integral method
 DAM - Derivative approximation method
 results are compared with model and
polynomial fitted
 appartus shows a good results with
mathematical model
 DAM method can be used if temp.
difference is very low

8. Thermal conductivity measurements at low temperatures
P.Balaya et al.
 Both steady state and laser pulse method is used
 Uses two heaters, one to heat sample and other to
achieve one dimension flow
 Heat losses by gas convection and conduction are
reduced by maintaining a vacuum of 10^-5 torr
 SS304 is used to measure th. conductivity in both
methods
 measured along temp. range of 77K to 300K