In modern industrial production, plate heat exchangers, as highly efficient heat transfer equipment, are widely used in various process flows. They can quickly transfer heat from one fluid to another, thereby achieving energy savings and improving production efficiency. However, to ensure that plate heat exchangers operate efficiently, stably, and economically in complex industrial environments, material selection is a crucial step. This article will explore in depth how to make a wise choice among numerous materials to achieve the optimal balance between performance and cost.
During operation, plate heat exchangers come into contact with various fluids, whose properties vary widely, including temperature, pressure, pH, and corrosiveness. These properties directly determine the direction of material selection.
The temperature range of the fluid is a factor that must be considered when selecting materials. Different fluids may operate in low-temperature (such as refrigerants) or high-temperature (such as steam) environments. For example, when handling high-temperature steam, the material must withstand high temperatures, otherwise deformation or damage may occur, affecting heat exchange efficiency, and potentially causing safety accidents.
The pressure of the fluid is also a key factor. High-pressure fluids place higher demands on material strength. If the material strength is insufficient, leakage may occur under high pressure, not only wasting energy but also posing a threat to personnel and equipment.
The acidity, alkalinity, and corrosiveness of the fluid are critical aspects to consider when selecting materials. Strong acids, strong bases, and saline solutions are highly corrosive to materials, and ordinary metals may quickly be corroded or perforated in such environments. For example, when handling strong acidic fluids such as sulfuric acid or hydrochloric acid, the material must have good acid resistance; while handling alkaline solutions, alkali resistance is also crucial.
When facing various corrosive fluids, it is essential to select materials with good corrosion resistance. The selection depends on the fluid composition and properties.
In strong acid environments, nickel alloys are a very good choice. Nickel alloys can resist corrosion from various acids and maintain the integrity and performance of the material. For example, in chemical production handling strong acids like sulfuric acid or hydrochloric acid, plate heat exchangers made of nickel alloys can operate stably for long periods, greatly extending the service life of the equipment.
For strong alkaline fluids, stainless steel performs excellently. 304 and 316 stainless steels are common choices, as they have good alkali resistance and can maintain stable chemical properties in alkaline environments. 316 stainless steel has stronger chloride corrosion resistance than 304 stainless steel, making it especially suitable for food processing and chemical equipment.
When handling saline fluids, titanium alloys are ideal. Titanium alloys have excellent seawater corrosion resistance and can maintain good performance even in high-salinity seawater for long periods. This makes titanium alloys widely used in marine engineering and seawater desalination. For example, in seawater cooling systems, using titanium plate heat exchangers can effectively prevent corrosion from seawater and reduce equipment maintenance costs.
Plate heat exchangers operate over a wide temperature range, from low-temperature refrigeration systems to high-temperature industrial furnace waste heat recovery. Materials need to have good temperature adaptability.
In low-temperature environments, materials may become brittle, resulting in reduced strength. Therefore, it is essential to select materials with good low-temperature performance. For example, in some refrigeration systems, aluminum plate heat exchangers are widely used due to their good low-temperature performance. Aluminum maintains relatively high toughness and strength at low temperatures, enabling effective heat transfer without cracking.
In high-temperature environments, high-temperature resistance is even more critical. High-temperature alloys are the preferred choice under high-temperature conditions. These alloys can maintain stable structure and performance at high temperatures without deformation or softening. For example, in high-temperature cracking processes in the petrochemical industry, plate heat exchangers often need to withstand temperatures above 600℃. Plate heat exchangers made of high-temperature alloys can ensure stable operation under high temperatures, effectively recover high-temperature waste heat, and improve energy efficiency.
The gasket materials between plates in a plate heat exchanger are equally important. Sealing materials need to be resistant to high temperatures and corrosion, while also ensuring good sealing performance to prevent fluid leakage.
Graphite-reinforced rubber gaskets are common sealing materials. They combine the high-temperature and corrosion resistance of graphite with the elasticity of rubber, maintaining good sealing under various harsh conditions. For example, in some chemical production, using such gaskets can effectively prevent leakage of strong acids and alkalis.
PTFE composite gaskets are a new type of sealing material with superior chemical resistance and sealing performance, suitable for a wider range of operating conditions. They can maintain stable sealing in high-temperature and highly corrosive environments, making them one of the commonly used sealing materials in modern industry.
When selecting materials for plate heat exchangers, cost is a factor that cannot be ignored. Material costs vary greatly, from ordinary carbon steel to high-end titanium and nickel alloys. Therefore, it is crucial to select materials that balance performance and cost while meeting equipment performance requirements.
On one hand, materials should be chosen based on actual budget and performance requirements. If the operating environment does not demand high corrosion resistance, relatively low-cost carbon steel can be selected. Carbon steel has high strength and durability and is relatively inexpensive, suitable for many industrial applications. For example, in ordinary cooling water systems, using carbon steel plate heat exchangers can meet operational requirements while effectively controlling costs.
On the other hand, the material’s service life and maintenance costs should be considered comprehensively. Although some high-performance materials have a higher initial investment, they offer longer service life and lower maintenance costs. In the long run, they may be more economical. For example, titanium alloys are expensive, but in highly corrosive environments like seawater, their service life may be several times that of ordinary materials, and maintenance costs are extremely low. From a total lifecycle cost perspective, they may be more advantageous.
When selecting materials for plate heat exchangers, multiple factors need to be comprehensively considered, weighing all requirements to choose the most suitable material. When making the final selection, it is recommended to consult equipment manufacturers or engineering experts. Manufacturers can provide professional advice based on experience and actual conditions to ensure that the selected materials meet performance requirements and economic feasibility.
During heat exchanger design, the materials for various components should be selected based on operating pressure, temperature, fluid corrosion properties, and manufacturability. Generally, meeting operating pressure and temperature requirements is relatively straightforward from the perspective of strength and stiffness, but corrosion resistance can often be a complex issue. Improper consideration or selection may not only affect the service life of the heat exchanger but also significantly increase equipment cost.
Tube materials for heat exchangers include stainless steel, copper-nickel alloys, nickel-based alloys, titanium, and zirconium alloys. Except where welded tubes cannot be used industrially, welded tubes are generally employed, with corrosion-resistant materials only used on the tube side, while the shell is carbon steel. Carbon steel has high strength and durability, is relatively inexpensive, and is suitable for many industrial applications, especially in high-temperature and high-pressure conditions with alkaline media, but it is easily corroded by acids, making it reasonable for environments without corrosion resistance requirements.
Austenitic stainless steel, represented by 1Cr18Ni9Ti, is a standard 18-8 austenitic stainless steel with a stable austenite structure, good corrosion resistance, and cold working properties. Triangular tube arrangements are compact, square arrangements facilitate mechanical cleaning, concentric circular arrangements are used for small shell diameter exchangers, and outer circular tube layouts are more uniform and compact. In Chinese heat exchanger series, fixed tube plate types mostly use triangular arrangements, while floating head types often use staggered square arrangements, with some triangular arrangements as well.
Stainless steel has excellent corrosion resistance and strength, suitable for various media, particularly in food, pharmaceutical, and chemical industries. Copper has good thermal conductivity, suitable for applications requiring high heat transfer, such as air conditioning and refrigeration. Aluminum has good thermal conductivity and light weight, suitable for low-temperature or non-corrosive media. Titanium has extremely high corrosion resistance, suitable for special environments such as seawater treatment and chemical processing. Various alloy materials, such as nickel alloys or aluminum bronze, can be chosen according to specific requirements to meet particular working conditions.
Selecting the appropriate material for plate heat exchangers is a complex and important process. By thoroughly understanding fluid properties and selecting materials with good corrosion resistance, temperature adaptability, sealing performance, economic feasibility, and manufacturability, heat transfer efficiency can be effectively improved, equipment service life extended, and maintenance costs reduced. In practical applications, consulting equipment manufacturers or engineering experts is recommended to ensure that the selected materials meet both performance requirements and economic feasibility. Only in this way can an efficient, stable, and economical heat exchange process be achieved in modern industrial production.
