Guide to Heat Exchanger Tubes: Types, Materials and Application

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The fundamental element of any heat exchanger system is the heat exchanger tubes, which absorb the heat and transfer it to two fluids without blending them. They play a crucial role in ensuring the control of temperature and the use of energy in different processes. They will be in industries such as power generation, oil and gas, HVAC, food processing, and chemical manufacturing, or anywhere they need heat transfer. These are some of the things that you should know about heat exchanger tubes in this guide: their type, material, design, and primary uses. Be it that you are creating a new system or upgrading the current equipment, this guide will assist in making a correct performance-oriented decision for your operation.

What Are Heat Exchanger Tubes?

Heat exchanger tubes are unique parts that are dedicated to the exchange of heat between two fluids one hot and the other cold, without them blending. They constitute the primary operational component of the heat exchangers, upon which the thermal energy passes through the tube walls in order to attain effective cooling or heating. These tubes are often crafted out of different alloys such as stainless steel, copper, titanium, and nickel, among others, which were selected due to their strength and corrosion resistance. HVAC systems, oil refining, chemical processing, and power generation industries are some of the industries where heat exchanger tubes are found.

How Heat Transfer Works

Heat exchange in a heat exchanger does not involve the direct contact of the fluids, as heat is transferred between one fluid to another via the walls of the tubes. This process occurs through three key mechanisms that collaborate in order to cause efficient energy transfer:

• Conduction: The hotter fluid transfers heat to the colder fluid through the solid metal wall of the tube.
• Convection: Heat exchange occurs between the moving fluid and the tube surface inside or outside or both.
• Radiation (in rare cases): Heat is carried in electromagnetic waves, which are predominant in high-temperature systems such as boilers or furnaces.

Types of Heat Exchanger Tubes

There are different types of heat exchanger tubes, and each one has been designed to suit various types of heat transfer requirements in various forms of operation. The choice will be based on the nature of fluids, temperature, pressure level, and maintenance needs. The most common ones used in industries are the following:

1. Smooth Bore Tubes : Smooth bore tubes have a plain cylindrical inner surface that allows fluid to flow freely. Generally, smooth-bore tubes are used in the systems where the fluid is clean and little fouling will occur. Their simple design also makes them easily cleanable and maintainable.
2. Finned Tubes : These are finned tubes with external fins that extend the surface area through which heat transfer can take place. The design aims to enhance efficiency, especially in applications with air or gas cooling, because of improved heat exchange between the fluid inside the tube and the surrounding air.
3. Rifled or Corrugated Tubes : These tubes have internal grooves or ridges that create turbulence as the fluid flows through them, which enhances the heat transfer because it doesn't allow insulating layers to be set up along the inner surface of the tube. They are often used where a high degree of efficiency is demanded in compact design applications.
4. U-Tube Heat Exchangers : U-tube designs have U-shaped bends in their tubes to accommodate thermal expansion without placing any stress on the tube sheet. This configuration also has benefits with regard to maintenance and cleaning; only one tube sheet is needed.
5. Floating Head Tubes : Floating head tubes have one end fixed, while the other end is free to move. Therefore, they can handle temperature fluctuations and thermal expansion effectively. They are normally applied to processes involving periodic cleaning.
6. Double-Pipe Tubes : Double-pipe tubes consist of one tube placed inside another, allowing the flow of two fluids separately and the exchange of heat between them through their inner wall. This design is simple, compact, and suitable for smaller heat exchange systems.
7. Microchannel Tubes : Microchannel tubes consist of many small-diameter channels or flat passages that provide great surface area for heat exchange. Their compact and lightweight design makes them ideal for modern HVAC systems, automotive cooling, and electronic equipment.

Materials Used in Heat Exchanger Tubes

To know about the different materials that are used to make heat exchanger tubes and what the key advantages and limitations of these tubes are given below.

Classification of Heat Exchangers by Design

Depending on the choice of materials, it is essential to understand the overall design of a heat exchanger, although the main attention is paid to tubes. The types of heat exchangers vary in their operational needs, compatibility of the fluids, as well as thermal loads, and it is based on this that the choice of materials depends on the need to be durable, resistant to corrosion, and efficient.

• Shell and Tube Heat Exchangers : The most common exchangers are shell and tube heat exchangers that are placed in a cylindrical shell. They are mostly used in power plants, refineries, and the process industry that need a heat exchanger that can handle high pressure and temperature.
• Plate and Frame Heat Exchangers : A plate and frame heat exchanger is commonly used in the fluid exchange frames that are used in the food, beverage, and pharmaceutical sectors. 
• Air-Cooled Heat Exchangers : The Air-Cooled heat exchanger is used to pass the heat from fluids into the air. They are located in compressor stations, refineries, and HVAC systems.
• Spiral and Plate Fin Heat Exchangers : Spiral and Flat fin heat exchangers are used mostly in refrigeration and cryogenic systems that do not have much space, and it’s suitable for good heat transfer, longevity, and resistance to corrosion.

The knowledge of the type of heat exchanger will enable engineers to choose the appropriate materials that will ensure their safe, efficient, and long operation.

Applications of Heat Exchanger Tubes

The heat exchanger tubes are vital in the industries that have a high demand of effective and consistent heat transfer. They are designed, made, and perform to a broad and responsibility of multiple and challenging uses.

1. Power Generation : The purpose is to keep thermal control constant and enhance efficiency of the plants, which are used in steam condensers, boilers, feedwater heaters, and turbine systems.
2. Chemical and Petrochemical Plants : Intended to deal with corrosive fluids and elevated temperature, which creates secure and consistent heat transfer in reactors, coolers, and process systems.
3. Oil & Gas Refineries : It is used in heat recovery units, process heaters, process coolers, and exchangers, which are used in extreme pressure and temperature environments.
4. Marine and Offshore : Seawater-cooled condensers, marine HVAC and desalination units and offshore platforms use titanium and copper-nickel and stainless steel tubes, owing to their high resistance to corrosion.
5. HVAC and Refrigeration : Increase the efficiency of the cooling of the residential, commercial, and industrial cooling systems in terms of energy consumption in the chillers, evaporators, condensers, or air handling units.
6. Food and Beverage Industry : Applied in pasteurization, sterilization, heating and cooling systems where hygiene, corrosion resistance and cleanability are important.
7. Steel and Fertilizer Plants : Power high temperature operations in heavy industrial settings, including heat recovery, gas cooling and thermal processing processes.

Conclusion

An appropriate selection of a heat exchanger tube is critical in enhancing the efficiency of the system, safety, and performance of the system in the long run. The knowledge of the various types, materials and designs aids in the enhancement of heat transfer and longevity of the service. Amardeep Steel Centre is highly diversified in the production of various high quality heat exchanger tubes that are produced to international standards like ASTM, ASME and TEMA as used in all industries with the confidence that they are of precision and longevity. In case you require professional advice or a tailor-made product, Amardeep Steel Centre staff is willing to assist you in locating the right tube to use.