Material Selection in Plate Heat Exchangers: Balancing Performance, Safety, and Economy
1. Introduction
Plate heat exchangers (PHE - Plate Heat Exchangers) are indispensable equipment for thermal energy transfer in many sectors such as energy, food, chemical, pharmaceutical, HVAC, and maritime industries today. The performance of these systems, distinguished by providing a high heat transfer surface, compact size, and easy maintenance, is largely dependent on the correct material selection.
The longevity and optimum performance of a plate heat exchanger is not only determined by its design but also by the correct selection of materials used. When selecting materials, working conditions, fluid properties, cost-effectiveness, and legal requirements should be carefully evaluated in a balanced manner. Otherwise, early failures, production losses, and high maintenance costs may arise in the system. This article comprehensively covers the fundamental criteria for material selection in plate heat exchangers, the commonly used material types, and application-based selection strategies.
2. Primary Criteria Affecting Material Selection
Material selection should be carried out based on multidimensional criteria such as not only mechanical suitability but also chemical resistance, thermal performance, economic sustainability, and operational safety. The critical selection criteria can be listed as follows:
2.1 Corrosion Resistance
Since the operating environments of heat exchangers generally contain aggressive fluids, plate and gasket materials must be corrosion-resistant. Parameters such as fluid pH, chloride concentration, and oxidizing agent content directly impact the type of material to be selected. For example, when the chloride content exceeds 0.1%, high-resistance materials like Titanium should be preferred over 316L.
2.2 Thermal Conductivity
The thermal conductivity coefficient of the material (in W/m·K), directly affects the thermal efficiency of the exchanger. High conductivity optimizes both space utilization and investment costs by providing the same heat transfer with smaller exchanger sizes.
2.3 Mechanical Strength
Heat exchangers operate continuously under mechanical loads against operating pressure and temperature fluctuations. Especially cyclical temperature changes can cause fatigue and cracking in the plates. Therefore, it is crucial for the selected material to have sufficient yield strength and fracture toughness.
2.4 Cleanliness, Maintenance, and CIP Compatibility
In sectors where hygiene is critical such as food and pharmaceuticals, plates and gaskets must be compatible with Clean-In-Place (CIP) systems. This necessitates special designs in terms of surface roughness (Ra value) and chemical resistance.
2.5 Economy and Logistics
The balance between investment and operating costs must be considered. In some cases, a material with a high initial investment cost can reduce the total cost of ownership (TCO) through its long life and low maintenance costs.
2.6 Legal and Sectoral Regulations
In sectors such as food and pharmaceuticals, full compliance with standards such as FDA, 3-A Sanitary Standards, EN1935/2004 is required. Therefore, material selection should be done not only technically but also meticulously in terms of regulatory compliance.
3. Plate Materials and Properties
Plate materials are surfaces that come into direct contact with the fluid and where the heat transfer occurs, so making a mistake in the selection directly affects the system's longevity and efficiency.
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Material
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Properties
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Applications
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Advantages
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Limitations
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AISI 304 Stainless Steel
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Moderate corrosion resistance, good formability
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Food, HVAC, water treatment
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Economical, easily available
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Not suitable for high chlorine environments
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AISI 316L Stainless Steel
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With molybdenum addition, high corrosion resistance
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Pharmaceuticals, food, seawater systems
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Wide process range
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Limited use in strong acidic environments
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Titanium (Ti Gr 1/2)
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Excellent chlorine and seawater resistance
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Saline water, maritime, brine waste
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Very high corrosion resistance
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High initial investment cost
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Hastelloy C-276
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Superior acid and oxidation resistance
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Chemical processes, metal coating facilities
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Ideal for highly aggressive environments
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Very high cost
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SMO 254 (6Mo)
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High pitting and crevice corrosion resistance
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Chemical, power plants
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Higher level of protection than 316L
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Relatively high cost
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Especially in high-risk applications such as seawater and chemical fluids, wrong material selection can lead to complete equipment failure within a few years.
4. Gasket Materials and Selection Criteria
Gaskets provide sealing to prevent the mixing of fluids and keep the plates together. Gasket selection depends on factors such as temperature, chemical compatibility, and mechanical strength.
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Gasket Material
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Properties
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Applications
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NBR (Nitrile Rubber)
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Resistant to mineral oils, light chemicals
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HVAC, low-temperature systems
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EPDM
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Resistant to hot water, light acids and alkalis
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Food, drinking water, HVAC
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Viton (FKM)
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Resistant to high temperature and aggressive chemical environments
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Chemical, petrochemical
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HNBR
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