Thermal Conductivity of Seamless Pipe

The seamless pipe is widely used in boilers, heat exchangers, petrochemicals, power generation, and high-temperature, high-pressure systems. Their thermal conductivity is one of the key physical parameters for evaluating a material's heat transfer capacity. A proper understanding of the thermal conductivity of seamless pipes is helpful for engineering selection, energy-saving design, and safe system operation.

This article will introduce the numerical values of the thermal conductivity of seamless pipes, the reasons for differences, and the materials, characteristics, and applications of thermally conductive seamless pipes.

Thermal Conductivity of Seamless Pipes

The thermal conductivity (λ) of a seamless pipe refers to its ability to transfer heat per unit area per unit time under certain temperature and conditions; it is also called thermal conductivity.

According to the definition of the International System of Units (SI), the unit of thermal conductivity for seamless pipes is W/(m·K). The magnitude of the thermal conductivity of a seamless pipe is related to the material of the tube, temperature, and other factors.

The thermal conductivity of seamless pipes is generally between 20 and 40 W/(m·K), with the specific value also depending on the type of material.

For example, some materials with high thermal conductivity, such as magnesium, copper, and aluminum, have higher thermal conductivity than ordinary steel. In addition, temperature and pressure also affect the thermal conductivity of seamless pipes.

For seamless pipes, thermal conductivity directly affects: heat exchange efficiency (boiler tubes, heat exchanger tubes), thermal response speed (high-temperature pipelines), energy utilization and operating costs, and the risk of localized overheating and thermal fatigue.

Materials of Thermally Conductive Seamless Pipes

The materials used for thermally conductive seamless pipes are diverse, with common materials including carbon steel, stainless steel, and alloy steel. These materials possess good thermal conductivity, corrosion resistance, and high-temperature strength, enabling thermally conductive seamless pipes to maintain stable performance even in harsh working environments.

1. Carbon Steel

Carbon steel is the most common material for thermally conductive seamless pipes, possessing a high thermal conductivity and low cost. However, carbon steel has poor corrosion resistance and is suitable for general industrial applications.

2. Stainless Steel

Stainless steel thermally conductive seamless pipes have excellent corrosion resistance and high thermal conductivity, making them suitable for industries with high material requirements, such as chemical, pharmaceutical, and food industries.

3. Alloy Steel

Alloy steel seamless thermally conductive pipes, through the addition of alloying elements, improve the high-temperature resistance, corrosion resistance, and strength of the steel pipes, making them suitable for harsh working environments such as high temperature and high pressure.

Reasons for Differences in Thermal Conductivity of Seamless Pipes

1. Elemental Composition

Carbon Steel: Carbon atoms in the iron matrix form interstitial solid solutions, which have little impact on electron scattering, resulting in high thermal conductivity (e.g., 20# steel 46 W/(m·K)).

Alloy Steel: Alloying elements such as chromium and molybdenum form substitutional solid solutions, increasing electron scattering and decreasing thermal conductivity (e.g., 42CrMo only 32 W/(m·K)).

Stainless Steel: Nickel (content 8%-18%) significantly inhibits electron movement; 304 stainless steel has a thermal conductivity of only 16.3 W/(m·K), one-third that of carbon steel.

Copper-based Alloys: Copper atoms have high degrees of freedom in their outer electrons, forming an "electron sea," resulting in extremely high thermal conductivity (e.g., copper-nickel alloys reach 200 W/(m·K)).

2. Crystal Structure

Body-centered cubic (BCC): Carbon steel and alloy steel have a BCC structure, resulting in a longer electron scattering path and moderate thermal conductivity.

Face-centered cubic (FCC): Stainless steel and copper-based alloys have an FCC structure, resulting in more frequent electron scattering. However, copper-based alloys maintain high thermal conductivity due to their high electron density.

3. Temperature Effect

Carbon steel: Thermal conductivity is 46 W/(m·K) at 20℃, decreasing to 30 W/(m·K) at 500℃ (lattice vibrations intensify at high temperatures, increasing electron scattering).

Stainless steel: Thermal conductivity is 16.3 W/(m·K) at 20℃, decreasing to 12.5 W/(m·K) at 800℃ (nickel further inhibits heat conduction at high temperatures). Copper-based alloys: Thermal conductivity of 200 W/(m·K) at 20℃, and still 180 W/(m·K) at 200℃ (high-temperature stability superior to steel).

Comparison of Thermal Conductivity with Other Steel Pipe Types

1. Seam Pipe vs. Seamless Pipe

Both have similar thermal conductivity under the same material, but welded pipes may have microstructural differences in the weld seam, resulting in uneven local thermal conductivity. Seamless pipes have better overall uniformity.

2. Special Case of Galvanized Steel Pipes

The zinc coating (thermal conductivity approximately 110 W/(m·K)) can improve surface thermal conductivity, but the zinc layer thickness is only on the micrometer scale, having limited impact on overall performance. The base material still plays a dominant role.

How to Choose Seamless Pipes with Suitable Thermal Conductivity

When selecting seamless pipes, we need to choose materials with appropriate thermal conductivity based on the required application scenario.

Thermal Conductive Seamless Pipe Applications

Due to their unique materials and manufacturing processes, thermal conductive seamless pipes possess characteristics such as high thermal conductivity, good structural strength, and strong corrosion resistance.

This makes them play an important role in equipment such as heat exchangers, condensers, and generator sets, improving energy utilization efficiency and equipment lifespan.

Furthermore, thermal conductive seamless pipes are widely used in industries such as petroleum, chemical, power, and metallurgy.

For example, in the oil extraction process, thermal conductive seamless pipes can be used to transport high-temperature and high-pressure oil-gas mixtures;

In the chemical industry, thermal conductive seamless pipes can be used to manufacture equipment such as reaction vessels and evaporators to improve heat transfer efficiency;

In the power industry, thermal conductive seamless pipes can be used to manufacture key components such as boiler water-cooled walls and superheaters to ensure the safe and stable operation of generator sets.

FAQ

1. Is a seamless pipe with a higher thermal conductivity always better?

Not necessarily.

Thermal conductivity is only one factor in material selection. In engineering, a comprehensive consideration is usually needed for:

Strength and pressure resistance;

Corrosion resistance;

Operating temperature and lifespan;

Cost and standard requirements.

For example, although stainless steel has lower thermal conductivity, it is a better choice in highly corrosive environments.

2. Is the thermal conductivity of seamless pipes explicitly specified in relevant standards?

Most steel pipe standards (such as ASTM A106, EN 10216, GB/T 8163) do not directly specify a numerical value for thermal conductivity, but rather specify chemical composition, mechanical properties, and operating temperature.

Thermal conductivity is usually used as a physical property parameter of materials for reference in thermal calculations and engineering design.

Read more: Thermal conductivity of carbon steel pipe