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Thermal Conductivity - Definition, Examples, Formula, Properties, FAQs

Thermal Conductivity - Definition, Examples, Formula, Properties, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:41 PM IST

What is Thermal conductivity?

Thermal conductivity definition refers to the power of an object given to conduct / transfer heat. It is usually indicated by the symbol 'k' but can also be indicated by'λ 'and' κ '. The repetition of this amount is known as the heat of opposition. High-temperature materials are used for heat sinks and materials with low λ values are used as heat insulators. Fourier's law of thermal conductivity meaning also known as thermal conduction law) states that the rate at which heat is transmitted by an object is equal to the gradient temperature and is equal to the area in which the heat flows. The separation form of this rule can be shown in the following equation:

This Story also Contains
  1. What is Thermal conductivity?
  2. Thermal Conductivity Formula
  3. SI unit of Thermal conductivity
  4. Instruments for Thermal conduction
  5. Factor Effects on Thermal conductivity
  6. Thermal properties of materials
  7. What are Thermal Properties of Objects
  8. What Is Heat Energy?
  9. Thermal Conductivity examples
  10. Thermal conductivity of glass

q = -k.∇T

When ∇T refers to the gradient of a temperature, q refers to the warmth or heat dissipation, and k refers to the continuous temperature of the object in question.

Temperature1 is a little greater than Temperature2. Therefore, thermal conductivity can be obtained by the following equation:

Flux Temperature = -k * (Temperature2 - Temperature1) / Size

Also read -

Background wave

Thermal Conductivity Formula

Everything has its own heat capacity. Thermal conduction of an object is defined by the following method:

K = (QL) / (AΔT)

Where,

K heat conduction W / mK

Q The amount of heat transferred by objects in Joules / second or Watts

L is the given distance between the given two isothermal planes

A square foot area

ΔT temperature difference in Kelvin

Evaluation

There are several ways to measure the heat conduction of objects. These methods are broadly divided into two types of strategies - temporary and robust strategies.

SI unit of Thermal conductivity

The temperature range is displayed according to the following sizes: Temperature, length, Mass, and time. The SI unit of this number is watts per meter - Kelvin or Wm-1K-1. It is usually expressed in terms of strength / (length * temperature). These units define the degree of high thermal conductivity using the unit size of the unit and each Kelvin temperature difference. Steady-State strategies These methods include measurements in which the temperature of the subject does not change over time.

The advantage of these methods is that the analysis is straightforward as the temperature is constant. Thermal conductivity of air with rise in temperature as the temperature of air increases the molecular diffusion also gets increases and in case of air. The main disadvantage of stability systems is that they often require very well-designed settings to perform tests. Examples of these methods are the Searle bar method for measuring the conductivity of a good driver and Lee's disk system.

Temporary Strategies

In these methods, measurements are taken during the heating process. An important advantage of these methods is that measurements can be taken very quickly. One of the shortcomings of short-term strategies is the difficulty of analyzing data mathematically. Other examples of these methods include the temporary flight source method, the transit line method, and the laser flash method. Therefore, there are various ways to measure the temperature of an object, each with its own advantages and disadvantages. It is important to know that it is easier to experiment with thermal properties of solids compared to liquids.

Effect of Temperature on Thermal conductivity

Temperature affects the thermal conductivity of metals and is not different.

Also, students can refer,

Instruments for Thermal conduction

Heat transfer of metals is caused by the availability of free electrons. It is somehow limited to the production of total temperature and energy efficiency, according to Wiedemann-Franz law. With increasing temperatures, the electric conduction of pure metal decreases. This means that the thermal conductivity of pure metal shows a slight variation with the increase in temperature. However, a significant decrease is observed when temperatures close to 0K. Steel alloys do not show significant changes in electrical performance when temperatures rise, which means that their temperature rises with increasing temperature. A high temperature range for most pure materials can be obtained at temperatures ranging from 2K to 10K.

Thermal conductivity for Non Metals

Non-metal thermal conductivity is mainly caused by lattice vibration. The free-range mode of the phones does not significantly reduce when temperatures are high, which means that non-metallic heat conduction does not show a significant change in high temperatures. When the temperature drops to a lower temperature than Debye, the thermal conductivity of the non-metal decreases with its thermal potential.

Other Factors Affecting Thermal conductivity

Temperature is not the only factor that causes a wide range of thermal conductivity. Other important factors that influence the temperature of the material are listed below.

Factor Effects on Thermal conductivity

Chemical phase of an object When the phase of an object changes, a sudden change in its thermal performance may occur. For example, the temperature of the ice temperature changes from 2.18 Wm-1K-1 to 0.56 Wm-1K-1 when it melts into a liquid phase.

Thermal Anisotropy Differences in the coupling of phones along a particular crystal axis cause some objects to show thermal conductivity values associated with various crystal axes. The presence of thermal anisotropy means that the direction in which the heat flows may not differ from the direction of temperature gradients. Electrical conduction of assets The Wiedemann-Franz Act which provides for the relationship between electrical conductivity and thermal conductivity applies only to metals.

Thermal properties of materials

A story has features or characteristics, by which it can be identified. Major building materials can be categorized below:

a)Mechanical features of building materials

b)Chemical properties of building materials

c)Physical properties of building materials

d)Elements of the size of building materials

e)Hot elements of building materials

What are Thermal Properties of Objects

Thermal structures are those structures of an object related to its thermal conductivity. In other words, these are the manifestations of an object through which heat passes through it. Thermal elements fall under the broad head of material materials.

The thermal properties of the material determine how it reacts in the face of temperature fluctuations (extreme temperatures or very low temperatures, for example). The main tropical areas are:

Heat power

Hot Extensions

Heat drive

Heat stress

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What Is Heat Energy?

The temperature of an object can be defined as the heat required to change the temperature of an object by one degree. The heat is usually expressed in joules or calories and the temperature in Celsius or Kelvin.

To calculate the thermal energy of objects of a given size, Molar thermal energy or specific thermal energy is used.

Temperature Volume Formula

Q = m c ΔT

Where,

Q heat capacity in J

m size in g

c some heat in JK-1

IsT temperature change in ° K

Large parts of tropical areas

Heat Expansion

When heat is transferred through an object, its structure changes. Usually, an object expands as it inflates. This material material is called thermal expansion. There may be changes in location, volume, and layout. For example, a railway line tends to stretch and, as a result, has received improper formation due to extreme heat. The result of a hot expansion of the railway line

Heat drive

It is the material of the heat exchanger itself. Items with high thermal conductivity will conduct more heat than those with low conductivity. For example, a metal rod will heat up more than a standard window glass. Some materials do not absorb heat at all due to the protective properties of the material.

Heat stress

The pressure the body receives as a result of an increase in temperature is called thermal stress. It can be as destructive to the environment as it could cause an object to explode. For example, cracks can be seen on roads when it is very hot. Fractures are the result of heat stress.

Thermal Conductivity examples

Thermal Conductivity of Diamond – 2200 W/m•K. …

Thermal Conductivity of Glass - 0.8 W//m•K. ….

Copper – 398 W/m•K. ...

Gold – 315 W/m•K. ...

Silicon carbide – 270 W/m•K. ...

Beryllium Oxide– 255 W/m•K. ...

Tungsten – 173 W/m•K.

Thermal conductivity of glass

ordinary glass : 0.8 W/m.K

Thermal conductivity of Diamond

Of ordinary diamond it is 2200 W/m.K

Also check-

NCERT Chemistry Notes :

Frequently Asked Questions (FAQs)

1. 1.What is the process of thermal conductivity?

Conducting is the process in which heat energy is transferred by some collision between neighboring atoms and molecules. ... The heat of the fire causes the molecules in the pan to move faster, making them hotter. These vibrating molecules collide with their neighboring molecules, causing them to vibrate rapidly.

2. 2.Where does the heat process depend?

The process of conducting heat basically depends on four basic factors and they are: temperature gradient,

     the cross section of the material    involved,

     the length of their path and

     the properties of those materials.

3. 3.Why is thermal performance important?

The increase in thermal conductivity allows the heat for a faster rate of heat transfer to the phase shifts that reduces the time required for the PCM to fully charge or discharge. By Aymara Albury, Ph.D. D. Thermal conductivity is the internal material of an object that reflects its thermal conductivity.

4. 4.What is a high temperature operation?

Thermal conductivity refers to the amount / speed of heat transmitted by an object. ... Instruments with high thermal conductivity, e.g. copper, show high electrical conductivity. Heat generated by high-temperature thermal materials is carried out rapidly away from the weld region

5. 5.Does plastic have a high thermal conductivity?

Why is plastic a good protection? Plastics are poor heat conductors, because they do not have the free electrons available for operating methods such as metals. The capacity of the plastic heat shield is measured by measuring the thermal conductivity

6. How does porosity affect thermal conductivity?
Increased porosity generally decreases thermal conductivity because air (which has low thermal conductivity) fills the pores, reducing the overall heat transfer through the material.
7. Can thermal conductivity change with temperature?
Yes, thermal conductivity can vary with temperature. For many materials, it tends to decrease as temperature increases, but this relationship isn't universal and can be complex for some substances.
8. How does alloying affect thermal conductivity?
Alloying generally decreases thermal conductivity compared to pure metals. This is because impurities and structural defects introduced by alloying interfere with the movement of electrons and phonons, reducing heat transfer efficiency.
9. How does anisotropy affect thermal conductivity?
In anisotropic materials, thermal conductivity can vary depending on the direction of heat flow. This is common in materials with layered or fibrous structures, where heat may conduct more easily along one axis than others.
10. What is the thermal conductivity of a vacuum?
A perfect vacuum has zero thermal conductivity as there are no particles to transfer heat. However, in practice, even high vacuums have some heat transfer due to radiation.
11. How is thermal conductivity measured experimentally?
Common methods include the guarded hot plate method, heat flow meter method, and transient plane source technique. These methods typically involve applying a heat source to a material and measuring the temperature gradient across it.
12. What is the role of thermal conductivity in the design of high-temperature superconductors?
Understanding thermal conductivity is crucial in superconductor design, as it affects how heat is managed in these materials, particularly during the transition between normal and superconducting states.
13. What is the significance of thermal conductivity in the food industry, particularly in food processing and packaging?
Thermal conductivity is crucial in food processing for efficient heating or cooling. In packaging, it affects how well the package insulates food products, impacting shelf life and quality.
14. How does thermal conductivity impact the efficiency of thermoelectric cooling devices?
In thermoelectric coolers, materials with low thermal conductivity but high electrical conductivity are desirable to maintain a temperature gradient while allowing electric current flow, improving cooling efficiency.
15. What are the units of thermal conductivity?
The SI unit for thermal conductivity is watts per meter-kelvin (W/m·K). In imperial units, it's often expressed as BTU/(hr·ft·°F).
16. What is the significance of thermal conductivity in the development of advanced nuclear reactor materials?
In nuclear reactors, materials with high thermal conductivity are crucial for efficient heat removal from the core, while low conductivity materials are used for insulation. Balancing these properties is essential for safe and efficient reactor design.
17. What is the relationship between thermal conductivity and sound propagation in materials?
While not directly related, both thermal conductivity and sound propagation depend on the material's atomic structure and bonding. Materials with high thermal conductivity often have high sound velocity due to their rigid atomic structures.
18. What is the formula for thermal conductivity?
The formula for thermal conductivity (k) is:
19. What is the significance of the Lorenz number in thermal conductivity?
The Lorenz number relates thermal conductivity to electrical conductivity in metals, as described by the Wiedemann-Franz law. It helps predict thermal properties based on electrical measurements.
20. How does thermal conductivity affect the performance of thermal barrier coatings in gas turbines?
Thermal barrier coatings with low thermal conductivity are used to protect turbine components from high temperatures, improving efficiency and longevity. The coating's thermal conductivity directly impacts its insulating effectiveness.
21. What is the significance of the phonon mean free path in nanoscale thermal conductivity?
At the nanoscale, when material dimensions approach or become smaller than the phonon mean free path, thermal conductivity can be significantly reduced due to increased phonon scattering at boundaries.
22. How does thermal conductivity influence the design of heat pipes?
Heat pipes rely on materials with high thermal conductivity to efficiently transfer heat from one end to the other. The choice of material significantly affects the heat pipe's performance and operating temperature range.
23. How does thermal conductivity relate to insulation?
Materials with low thermal conductivity make good insulators because they resist heat flow. Conversely, materials with high thermal conductivity are poor insulators as they allow heat to transfer easily.
24. How does thermal conductivity differ in solids, liquids, and gases?
Generally, solids have the highest thermal conductivity, followed by liquids, and then gases. This is due to the differences in particle spacing and molecular motion in these states of matter.
25. How does thermal conductivity impact heat sinks?
Heat sinks are designed with materials of high thermal conductivity to efficiently draw heat away from electronic components. The higher the thermal conductivity, the more effectively the heat sink can dissipate heat.
26. What is the Wiedemann-Franz law?
The Wiedemann-Franz law states that the ratio of thermal conductivity to electrical conductivity in metals is proportional to temperature. This relationship highlights the connection between thermal and electrical properties in metals.
27. Can thermal conductivity be negative?
In conventional materials, thermal conductivity is always positive. However, in certain engineered metamaterials or under specific conditions, negative thermal conductivity can theoretically exist, though it's a complex and debated topic in materials science.
28. What is the concept of effective thermal conductivity in composite materials?
Effective thermal conductivity is the overall heat transfer capability of a composite material, considering the thermal conductivities and volume fractions of its components. It's crucial in designing multi-layered insulation systems.
29. How does thermal conductivity relate to the greenhouse effect?
While not directly related to the greenhouse effect (which primarily involves radiation), thermal conductivity plays a role in heat transfer within the atmosphere and oceans, influencing global heat distribution and climate patterns.
30. How does thermal conductivity affect the formation of frost on surfaces?
Materials with high thermal conductivity can quickly transfer heat from warmer air to a cold surface, promoting faster frost formation. Conversely, low thermal conductivity materials slow this process.
31. How does thermal conductivity impact the design of spacecraft?
Spacecraft design must carefully consider thermal conductivity to manage heat in the extreme temperature variations of space. This includes using high conductivity materials for heat dissipation and low conductivity materials for insulation.
32. How does thermal conductivity impact the efficiency of heat exchangers?
Higher thermal conductivity in heat exchanger materials allows for more efficient heat transfer between fluids, improving overall system performance and energy efficiency.
33. Why do metals typically have high thermal conductivity?
Metals have high thermal conductivity because of their free electrons, which can easily transfer kinetic energy throughout the material, and their closely packed atomic structure, which facilitates vibration transfer between atoms.
34. What is the relationship between electrical conductivity and thermal conductivity?
There's often a correlation between electrical and thermal conductivity, especially in metals. Materials that are good electrical conductors tend to be good thermal conductors due to the presence of free electrons that can transfer both electrical charge and thermal energy.
35. What is the role of thermal conductivity in thermoelectric materials?
Efficient thermoelectric materials require a balance: high electrical conductivity but low thermal conductivity. This combination allows for the generation of electricity from temperature differences while minimizing heat loss.
36. What is the role of phonons in thermal conductivity?
Phonons, which are quantized lattice vibrations, play a crucial role in heat conduction in non-metallic solids. They carry thermal energy through the material by transferring vibrations between atoms.
37. How does thermal conductivity impact the choice of cookware materials?
Cookware often uses materials with high thermal conductivity (like copper or aluminum) to ensure even heat distribution. However, handles are made of materials with low thermal conductivity to prevent burns.
38. How does thermal conductivity influence the design of thermal management systems in electronics?
High thermal conductivity materials are crucial in electronics cooling, helping to dissipate heat from components efficiently. This impacts the design of heat sinks, thermal interface materials, and overall system layout.
39. How does thermal conductivity affect the performance of thermal insulation in cryogenic applications?
In cryogenic systems, materials with extremely low thermal conductivity are crucial to maintain very low temperatures. The thermal conductivity of many materials changes significantly at cryogenic temperatures, affecting insulation performance.
40. How does thermal conductivity impact the efficiency of solar thermal collectors?
High thermal conductivity materials are used in solar thermal collectors to efficiently transfer heat from the absorber to the working fluid, improving overall system efficiency.
41. What is the role of thermal conductivity in the design of fire-resistant materials?
Fire-resistant materials often have low thermal conductivity to slow heat transfer and protect underlying structures. However, some fire-resistant designs may incorporate high conductivity layers to dissipate heat.
42. How does thermal conductivity affect the performance of thermal energy storage systems?
In thermal energy storage, materials with high thermal conductivity can charge and discharge heat more quickly, while low conductivity materials can help retain stored heat for longer periods.
43. What is the difference between thermal conductivity and thermal diffusivity?
Thermal conductivity measures a material's ability to conduct heat, while thermal diffusivity measures how quickly a material can change its temperature when heat is applied. Thermal diffusivity is the ratio of thermal conductivity to the product of density and specific heat capacity.
44. What is the relationship between thermal conductivity and thermal resistance?
Thermal resistance is inversely proportional to thermal conductivity. Materials with high thermal conductivity have low thermal resistance, and vice versa.
45. How does thermal conductivity relate to specific heat capacity?
While both properties involve heat transfer, they are distinct. Thermal conductivity measures how well a material conducts heat, while specific heat capacity measures how much heat energy is required to raise the temperature of a unit mass of the material by one degree.
46. What is the Kapitza resistance?
Kapitza resistance, or thermal boundary resistance, is the resistance to heat flow at the interface between two materials. It can significantly affect the overall thermal conductivity of composite materials or layered structures.
47. What is the significance of the mean free path in thermal conductivity?
The mean free path, the average distance particles travel between collisions, is crucial in determining thermal conductivity. Longer mean free paths generally result in higher thermal conductivity.
48. What is thermal conductivity?
Thermal conductivity is a material property that measures its ability to conduct or transfer heat. It quantifies how well a substance allows heat to flow through it when exposed to a temperature difference.
49. How is thermal conductivity different from heat conduction?
Thermal conductivity is a material property, while heat conduction is the process of heat transfer. Thermal conductivity determines how efficiently a material conducts heat, whereas heat conduction refers to the actual transfer of thermal energy through a material.
50. What is the role of thermal conductivity in geothermal energy extraction?
The thermal conductivity of rock formations is crucial in geothermal energy systems. Higher thermal conductivity allows for more efficient heat extraction from the Earth's crust.
51. How does thermal conductivity affect the formation of thermal bridges in buildings?
Materials with high thermal conductivity can create thermal bridges, allowing heat to bypass insulation and escape from buildings. This is a significant concern in energy-efficient construction.
52. What is the role of thermal conductivity in phase change materials (PCMs)?
In PCMs, thermal conductivity affects how quickly the material can absorb or release heat during phase transitions, impacting their effectiveness in thermal management applications.
53. How does nanostructuring affect thermal conductivity?
Nanostructuring can significantly reduce thermal conductivity by increasing phonon scattering at material interfaces. This principle is used in designing advanced thermal insulation materials.
54. How does moisture content affect the thermal conductivity of materials?
Moisture generally increases thermal conductivity because water has a higher thermal conductivity than air. This is particularly important in building materials and soils.
55. What is the relationship between thermal conductivity and thermal expansion?
While not directly related, both properties are important in material selection for applications involving temperature changes. Materials with high thermal conductivity often have lower thermal expansion, which can be advantageous in certain applications.

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