Materials used in industrial heat exchangers

Industrial heat exchangers play a key role in ensuring a given level of heat transfer between media. The basic design of this product was developed long ago, but modern technologies allow us to improve its parts and components, making it more efficient, economical and maintainable. To achieve these goals, the latest advances in heat engineering and hydrodynamics are used, and the properties of various metals are studied.

In this article, we will consider which heat exchanger is better, copper or steel, or made of another material.

Criteria for selecting materials for heat exchangers

To make a decision on which option is most suitable, it is not enough to know what metal the heat exchangers are made of, but you should understand the basic selection conditions. When choosing materials for a heat exchanger, it is important to consider the following:

• Materials for heat exchangers must have a high coefficient of thermal conductivity for efficient heat transfer.
• An important property is resistance to the aggressive environment in which the device will operate.
• The materials must be able to withstand loads and mechanical stress during operation.
• The manufacturing price should be competitive compared to other materials.

Most often, heat exchange plates are made of AISI 316 and AISI 304 stainless steels, sometimes titanium, and in some cases, hastelloy. Plate heat exchanger plates do not come into contact with the medium, so they are usually made of carbon steels, and for food production – of food grade stainless steel sheets of AISI304 material.

Steel as the main material for heat exchangers

In addition to the pipes, important elements are the pipe boards, casing, chambers, and spigots. If the cooling water is fresh and clean, they can be made of carbon steel (steel 3, steel 20) and alloy steel (09G2S). If seawater is used, then corrosion-resistant metals are used, such as SMO 254 stainless steel or titanium.

Carbon steel is often used in the manufacture of heat exchangers due to its high strength and good thermal conductivity. It is excellent for use in environments where high corrosion resistance is not required. However, in aggressive environments, carbon steel can corrode, which limits its use in certain conditions.

A stainless steel heat exchanger is a better choice for aggressive environments. The corrosion resistance of the metal allows for the effective use of such heat exchangers in the chemical, petrochemical, and food industries. In addition, a stainless steel heat exchanger retains its mechanical properties even at elevated temperatures.

Titanium and its alloys

Titanium and its alloys are a sought-after metal for heat exchangers, especially in aggressive environments. One of the main reasons for this choice is their outstanding resistance to corrosion, making them ideal for use in the chemical, oil and gas, and marine industries.

Corrosion resistance in aggressive environments

Titanium is a lightweight material with high corrosion resistance. It prevents further corrosion, which makes it the best choice for use in aggressive chemical environments, including acids, salts, and alkalis. However, since titanium is a brittle metal, water hammer should be avoided in the heat exchanger.

Main types of alloys

AISI 316: склад: 16-18% хрому, 10-14% нікелю, 2-3% молібдену

Advantages:

• Excellent corrosion resistance, especially in chloride environments.
• Good mechanical properties at high temperatures.
• Suitable for use in seawater and other aggressive environments.

Disadvantages:

• Lowest corrosion resistance compared to titanium in some conditions.
• High density and weight.

AISI 304: склад: 18-20% хрому, 8-10.5% нікелю

Advantages:

• Good corrosion resistance in most environments.
• Low cost compared to AISI 316.
• Suitable for most processes in the food industry.

Disadvantages:

• Less resistant to corrosion than AISI 316, especially in aggressive environments.
• May corrode in environments with a high chloride content.

Examples of titanium use in the chemical and oil and gas industries

Titanium and its alloys are widely used in a variety of industries, especially in manufacturing and process equipment. Due to its exceptional corrosion resistance and high strength-to-weight ratio, it is also used for environments containing large amounts of chlorides (seawater, NaCl and CaCl solutions, cooling tower recycling water). Let’s look at some specific examples of their use.

Heat exchangers

Application area: chemical and petrochemical industries.

Titanium heat exchangers are used to cool and heat corrosive liquids and gases. They effectively cope with high temperature and pressure. Titanium heat exchange equipment is resistant to corrosion in the presence of acids, alkalis, and seawater. If you use titanium heat exchangers, know that this material reduces the risk of damage and extends the service life of the equipment.

Reactors

Application area: chemical industry.

Titanium steel and alloys are often used in reactors for the synthesis of various chemicals. This equipment must withstand aggressive chemical environments and high temperatures. Titanium provides the necessary corrosion resistance and mechanical strength.

Pumps

Application area: oil and gas industry.

Titanium pumps are ideal for pumping corrosive liquids such as acids and brine. Their light weight and high strength reduce energy costs and serve a wide range of applications, including oil and gas lifting and transportation.

Nickel alloys

Nickel alloys are a group of materials characterized by high corrosion resistance and resistance to extreme temperatures. Due to these properties, they are widely used in industrial heat exchangers operating at high temperatures and aggressive chemical environments. The main characteristics that make nickel alloys popular in the manufacture of heat exchange equipment include their chemical inertness, resistance to oxidation, and ability to withstand high loads.

Nickel alloys can operate at temperatures that are well beyond the limits of other metal materials such as stainless steel. This property is particularly important for heat exchangers used in high-temperature processes, such as in the power generation and metallurgy industries.

Application in heat exchangers for high-temperature processes

The main industries in which nickel alloys are used:

• Energy – in heat exchangers for turbines, boilers and condensers.
• Metallurgy – for high temperature processes such as melting and heat treatment.
• Chemical and petrochemical industry – for contact with aggressive substances, including sulfuric acid.

An example is Hastelloy, one of the most famous nickel alloys with outstanding anti-corrosion characteristics. It is resistant to many chemicals, including sulfuric and hydrochloric acids. Due to these properties, Hastelloy is often used in chemical and petrochemical production, where materials are exposed to extremely aggressive environments.

Advantages of nickel alloys over other materials:

Selection of material for heat exchangers depending on operating conditions

Which heat exchanger, copper or stainless steel, is better? The choice of material should be based on the operating conditions. In industry, heat exchangers are subject to particularly stringent requirements when operating in aggressive environments and at high temperatures and pressures. The use of unsuitable materials can lead to reduced service life, frequent breakdowns and a high risk of accidents.

For chemical environments such as acids, alkalis, and seawater, materials must have high corrosion resistance. In the operating environment, it is recommended to choose alloys and metals that react with the substances in the working environment. The most suitable materials for aggressive environments:

• Titanium and its alloys – Resistance to seawater, acids and alkalis makes it an optimal choice for marine and chemical industries.
• Nickel alloys, such as Hastelloy, are widely used in the chemical and petrochemical industries due to their high corrosion resistance even when exposed to aggressive acids, including sulfuric and hydrochloric.
• Stainless steels have improved corrosion resistance compared to conventional steels, but may be inferior to titanium and nickel alloys in particularly aggressive environments.

When working with high temperatures and pressures, the key characteristics of the material should be thermal resistance and mechanical strength.

The most suitable materials for such conditions include:

• Nickel alloys are highly resistant to temperature changes and retain their properties even at extremely high temperatures. For example, Hastelloy and Inconel alloys are used in the energy and metallurgy industries, where equipment is exposed to extreme temperature changes.
• High-alloy stainless steels are resistant to elevated temperatures but less resistant to aggressive chemicals than nickel and titanium alloys.
• Heat-resistant steels with the addition of molybdenum or vanadium – used in heat exchangers operating at high pressure due to their ability to maintain strength at high temperatures.

The selection of material for heat exchangers must take into account both the chemical composition of the medium and the mechanical conditions of operation. With the right choice, the equipment can operate for a long time.

Effect of material selection on heat exchanger efficiency

The right material for heat exchangers has a significant impact on their efficiency and durability. Materials with high resistance to aggressive influences and mechanical damage can not only extend the service life of the equipment, but also significantly reduce the cost of its maintenance and repair.

A heat exchanger made of a resistant material does not require frequent repairs and replacement of elements, for example, in the chemical, petrochemical, and energy industries. For example, nickel and titanium alloys avoid destruction by chemicals, and heat-resistant alloys ensure stable operation at high temperatures.

Copper alloys in heat exchangers

It is also worth understanding why the heat exchanger is made of copper. This material is widely used due to a number of unique properties, such as high thermal conductivity, ease of processing, and antimicrobial properties. These qualities make copper alloys ideal for use in HVAC applications, such as air conditioners, refrigeration and heating systems.

The manufacture of copper heat exchangers is popular because the metal has a high thermal conductivity that is twice that of aluminum and almost ten times that of stainless steel. If you decide to buy a copper heat exchanger, you should know that it can transfer heat much faster than devices made of other metals.

Advantages and disadvantages of using copper

Before you buy a copper heat exchanger, you need to understand the advantages and disadvantages of this material.
Advantages:

• High thermal conductivity.
• Anti-corrosion properties.
• Plasticity and ease of processing.

Disadvantages of copper:

Copper is a more expensive material compared to aluminum or steel, which increases the cost of heat exchanger production.
It is also prone to corrosion in the presence of aggressive chemicals, such as ammonia or sulfur compounds.

Examples of copper use in industrial heat exchangers

Copper heat exchangers are widely used in climate control systems such as air conditioners and refrigerators. Copper allows for rapid heat transfer, ensuring the efficiency of the equipment. In heating systems, a copper heat exchanger is also often used due to its ability to distribute heat evenly, creating comfortable conditions. In addition, copper is used in medical and pharmaceutical facilities, where its antimicrobial properties help reduce the risk of bacteria on the surface of equipment.

Economic component

The choice of material for a heat exchanger has a direct impact on the costs of both equipment purchase and maintenance. Depending on the properties and durability, the cost of materials varies, and this must be taken into account when designing and purchasing equipment for different industrial sectors.

Comparison of the cost of materials

Materials for heat exchangers have significant price differences. Copper has a high cost, which is justified for climate control and heating applications where high heat transfer is a key factor. Stainless steel heat exchangers are a less expensive alternative for medium corrosive environments. Nickel and titanium alloys are the most expensive, but are indispensable in aggressive chemical environments and extreme temperatures.

The use of more durable materials, while increasing initial costs, can reduce repair and replacement costs. Heat exchangers made of such materials have a longer service life and are less susceptible to corrosion and deformation. However, for less aggressive applications, materials with lower cost and moderate resistance, such as stainless steel, can be chosen, thereby optimizing the budget.

To choose the most accurate heat exchangers for the needs of a particular industry, it is worth contacting professionals. Teplo-Polis offers the possibility of ordering industrial heat exchangers directly from the manufacturer, taking into account all the features and specifics of production.