Thermal conductivity measurement based on phase change materials

Patent metadata

Field	Value
Publication number	US-2025085242-A1
Application number	US-202318466225-A
Country	US
Kind code	A1
Filing date	Sep 13, 2023
Priority date	Sep 13, 2023
Publication date	Mar 13, 2025
Grant date	—

Abstract

The disclosed technology can be implemented to provide a method of determining a thermal conductivity of a sample. The method includes controlling a thermal source to increase a temperature of the thermal source to an elevated temperature above a phase change temperature of a phase change material, placing the sample between and in thermal contact with the phase change material below the phase change temperature and the thermal source to allow a thermal conduction from the thermal source to the phase change material through the sample to increase an initial temperature of the phase change material to the phase change temperature to cause the phase change material to transition from a first phase to a second phase, performing a measurement on at least one of the sample or the phase change material, and determining the thermal conductivity of the sample based on the measurement.

First claim

What is claimed is:

1 . A method of determining a thermal conductivity of a sample, comprising:
controlling a thermal source to increase a temperature of the thermal source to an elevated temperature above a phase change temperature of a phase change material; placing the sample between and in thermal contact with the phase change material at an initial temperature below the phase change temperature and the thermal source at the elevated temperature to allow a thermal conduction from the thermal source to the phase change material through the sample to increase the initial temperature of the phase change material to the phase change temperature to cause the phase change material to transition from a first phase to a second phase at the phase change temperature; performing a measurement on at least one of the sample or the phase change material; and determining the thermal conductivity of the sample based on the measurement.

2 . The method of claim 1 , wherein the phase change material maintains the phase change temperature for a first phase transition period to transition from the first phase to the second phase.

3 . The method of claim 2 , wherein the thermal source is at a constant temperature that is equal to or below the elevated temperature during the first phase transition period and for at least a second phase transition period longer than the first phase transition period.

4 . The method of claim 1 , further comprising shaping the phase change material to conform to a shape of the sample to ensure good thermal contact with the sample and accuracy in determining the thermal conductivity of the sample.

5 . The method of claim 1 , wherein the phase change material has a curved shape to conform to a curved shape of the sample to ensure good thermal contact with the sample and accuracy in determining the thermal conductivity of the sample.

6 . The method of claim 5 , wherein the thermal conductivity of the sample is determined by:

k
=

ρ
⁢

r
i
2

⁢

Hln
⁡
(

r
o

r
i

)

2
⁢

(

T
2

-

T
1

)

⁢
t

,

where k is the thermal conductivity of the sample, ρ is a density of the phase change material, H is a latent heat of the phase change material, r 1 is an inner radius of the curved shape of the sample, r 0 is an outer radius of the curved shape the sample, T 1 is the phase change temperature of the phase change material, T 2 is a constant temperature of the thermal source when the phase change material transitions from the first phase to the second phase at the phase change temperature, and t is the first phase transition period for the phase change material to transition from the first phase to the second phase.

7 . The method of claim 6 , wherein the sample is a solid material sample having a tube shape and the phase change material is shaped to include a portion that is in contact with and conforms to the tube shape at a contact location of the solid material sample.

8 . The method of claim 1 , wherein the sample is a liquid or gas and is directed to flow in a fluid conduit between and in thermal contact with the thermal source and the phase change material.

9 . The method of claim 2 , wherein the step of performing the measurement on the at least one of the sample or the phase change material comprises measuring the first phase transition period for the phase change material between a first time when at least a portion of the phase change material transitions from the first phase to the second phase, and a second time when substantially all the phase change material transitions to the second phase, and wherein the thermal conductivity of the sample is determined by:

k
=

m
1

⁢

H
1

⁢
h

A
⁡
(

T
2

-

T
1

)

⁢
t

,

where k is the thermal conductivity of the sample, m 1 is a mass of the phase change material, H 1 is a latent heat of the phase change material, h is a thickness of the sample, A is an area of the sample, T 1 is the phase change temperature of the phase change material, T 2 is a constant temperature of the thermal source when the phase change material transitions from the first phase to the second phase at the phase change temperature, and t is the first phase transition period for the phase change material to transition from the first phase to the second phase.

10 . The method of claim 3 , wherein the thermal source includes a second phase change material having a second phase change temperature.

11 . The method of claim 3 , further comprising:
placing a reference structure between the sample and one of the thermal source and the phase change material in a way that the reference structure is in thermal contact with the sample and the one of the thermal source and the phase change material; and measuring a reference temperature of the reference structure during the first phase transition period to determine a thermal conductivity of the sample between the reference temperature of the reference structure and either the phase change temperature of the phase change material or the constant temperature the thermal source during the first phase transition period of the phase change material.

12 . The method of claim 1 , further comprising:
placing a first reference structure in thermal contact with the sample and between the sample and the phase change material; placing a second reference structure between the sample and the thermal source to b

Assignees

• General Atomics

Inventors

• Zhang Jiping
• Blacklock Arthur

Classifications

• G01N25/18 Primary

  by investigating thermal conductivity (by calorimetry G01N25/20; by measuring change of resistance of an electrically-heated body G01N27/18) · CPC title

• G01N25/04 Primary

  of melting point; of freezing point; of softening point · CPC title