In industrial production, heat exchangers are indispensable equipment that transfer heat between different fluids, thereby meeting the needs of various process workflows. Shell-and-tube heat exchangers and plate heat exchangers are two common types, each with unique structural features, performance advantages, and suitable application scenarios. This article will provide an in-depth discussion of the structure, working principles, advantages, and applications of these two types of heat exchangers, helping readers better understand their importance in modern industry.
As a traditional heat exchange device, shell-and-tube heat exchangers are widely used in industrial production due to their mature technology and reliable performance. Their classic design and high heat transfer capability make them the preferred equipment in many industrial processes. Shell-and-tube heat exchangers not only meet diverse process requirements but also, due to their durability and ease of maintenance, have become trusted solutions for many engineers and enterprises.
A shell-and-tube heat exchanger is a traditional device primarily composed of a shell, tube bundle, tube sheets, baffles (deflectors), and tube boxes. The shell is usually cylindrical, containing a tube bundle, with both ends of the tubes fixed to the tube sheets. This structural design allows the shell-and-tube heat exchanger to effectively transfer heat between two fluids. In the shell-and-tube heat exchanger, the hot fluid and cold fluid flow inside and outside the tubes, respectively. The fluid inside the tubes is called the tube-side fluid, while the fluid outside the tubes is called the shell-side fluid. To improve the heat transfer coefficient of the shell-side fluid, multiple baffles are usually installed inside the shell. These baffles not only increase the velocity of the shell-side fluid but also force the fluid to pass through the tube bundle multiple times at specified distances, enhancing turbulence and thereby improving heat transfer efficiency. In addition, the heat transfer tubes can be arranged on the tube sheets in equilateral triangular or square patterns. Triangular arrangements are more compact and can create higher turbulence, achieving greater heat transfer coefficients; square arrangements facilitate cleaning of the tube surfaces, particularly suitable for fluids prone to scaling.
Shell-and-tube heat exchangers have multiple types, each with unique structures and suitable scenarios:
Fixed Tube Sheet Heat Exchanger: The tube sheets and the tube bundle at both ends of the shell are integrated, making the structure relatively simple. However, it is only suitable when the temperature difference between the hot and cold fluids is not large and mechanical cleaning of the shell side is not required. When the temperature difference is slightly larger and the shell-side pressure is not too high, elastic compensating rings can be installed on the shell to reduce thermal stress.
Floating Head Heat Exchanger: One end of the tube bundle’s tube sheet can float freely, completely eliminating thermal stress. Additionally, the entire tube bundle can be pulled out of the shell, making mechanical cleaning and maintenance very convenient. Therefore, floating head heat exchangers are widely used in industrial applications, but due to their complex structure, their cost is relatively high.
U-Tube Heat Exchanger: Each tube is bent into a U-shape, with both ends fixed to the same tube sheet at the top and bottom sections. With the help of tube box partitions, the heat exchanger is divided into inlet and outlet chambers. This design completely eliminates thermal stress, and its structure is simpler than the floating head type. However, the tube-side is difficult to clean, which limits its range of applications to some extent.
Shell-and-tube heat exchangers are widely used for their high efficiency and energy-saving characteristics. Their main performance advantages are as follows:
High Heat Transfer Efficiency: The heat transfer coefficient can reach 6000–8000 W/(m²·K), allowing excellent performance in heat exchange processes. By converting laminar flow to turbulent flow, shell-and-tube heat exchangers improve heat transfer efficiency and reduce thermal resistance.
Material and Durability: Typically made of full stainless steel, which is not only strong and durable but also has a long service life, generally up to 20 years.
High Temperature and Pressure Adaptability: Can withstand high temperatures (up to 400°C) and pressures (up to 2.5 MPa), making it suitable for complex industrial environments.
Compact Structure and Convenient Installation: Shell-and-tube heat exchangers are compact, occupy little space, are lightweight, and easy to install. This saves space and reduces civil construction investment.
Flexible Design and Application: Available in full specifications, highly practical, and capable of meeting various process requirements, saving costs. It is applicable across a wide range of media pressures, temperatures, and heat exchange conditions.
Low Maintenance Cost: Easy to operate, long cleaning intervals, and convenient cleaning. Using nano thermal film technology can significantly improve the heat transfer coefficient and further enhance performance.
Special Designs and Optimization: Some designs feature copper tubes with fins on the outer surface, improving thermal conductivity and increasing heat transfer area. Guide plates direct shell-side fluid flow continuously through the heat exchanger, with adjustable distances for optimal flow. This robust structure can handle high or ultra-high shell-side flow rates and high pulsation frequency. When the shell-side fluid is oil, the exchanger is suitable for low-viscosity, clean heat transfer oil.
Shell-and-tube heat exchangers are widely applied in thermoelectric, mining, petrochemical, urban district heating, food and pharmaceuticals, energy electronics, machinery, and light industries. Their reliable performance and broad applicability make them key equipment for heat exchange processes.
Plate heat exchangers, with their compact design and excellent heat transfer performance, have gradually become a preferred choice in many industrial applications. What unique advantages make them stand out in a competitive market? Next, we will discuss their structure, types and features, performance advantages, and applications.
Plate heat exchangers are relatively new devices, consisting of many corrugated thin plates arranged at intervals, sealed on the edges with gaskets, and clamped together with a frame and compression bolts. The four corner holes of the plates form fluid distributors and collectors. This design allows hot and cold fluids to flow separately on opposite sides of each plate, enabling heat exchange. This structure not only improves heat transfer efficiency but also makes the device compact and highly efficient.
Plate heat exchangers can be classified in several ways:
By Process Use: Different names exist depending on the application, such as plate heaters, plate coolers, plate condensers, and plate preheaters, reflecting their specific use in different processes.
By Process Combination: Can be single-pass or multi-pass depending on internal structure and fluid flow direction.
By Medium Flow Direction: Parallel flow, counterflow, or crossflow. Counterflow and crossflow are more common due to superior heat transfer.
By Gap Size: Standard gap or wide gap to accommodate internal fluid space requirements.
By Completeness: Individual plate or assembled plate heat exchanger units, reflecting assembly and usage methods.
High Heat Transfer Efficiency: Corrugated plates create three-dimensional rotational flow, inducing turbulence even at low Reynolds numbers (Re=50–200), with heat transfer coefficients 3–5 times higher than shell-and-tube exchangers. Temperature differences at the outlet can be less than 1°C for water-to-water heat exchange, compared to 5°C in shell-and-tube units.
Compact Structure: Heat transfer area per unit volume is 2–5 times greater than shell-and-tube, reducing footprint to 1/5–1/10 for the same capacity. Plate thickness is 0.4–0.8mm versus 2–2.5mm for tubes, with frame weight only about 1/5 of shell-and-tube.
Cost-Effectiveness: 40–60% lower price for the same heat transfer area due to stamped plates and high standardization, enabling mass production. Compact design reduces installation and maintenance costs.
Ease of Maintenance: Frames allow plates to be removed easily by loosening bolts for mechanical cleaning. Minimal heat loss occurs, requiring no insulation, unlike shell-and-tube units.
High Flexibility: Adding or removing plates adjusts heat transfer area; changing or replacing plates can adapt to new process requirements. Shell-and-tube areas cannot be adjusted once designed.
Low Heat Loss: Negligible heat loss, requiring no insulation.
Low Fouling: Turbulent flow reduces scaling; fouling coefficient is 1/3–1/10 that of shell-and-tube, extending lifespan and reducing maintenance frequency.
Plate heat exchangers are widely used in areas with high space constraints, frequent cleaning requirements, and high heat transfer efficiency demands. For example, in food processing, they heat or cool raw materials; in chemical industries, they manage heat exchange for chemicals; in pharmaceuticals, they meet strict hygiene standards for drug production processes.
To help everyone better weigh the pros and cons of these two types of heat exchangers, we will now provide a comprehensive and detailed comparison of shell-and-tube and plate heat exchangers.
Plate heat exchangers typically outperform shell-and-tube exchangers, with 3–5 times higher heat transfer coefficients due to induced turbulence even at low Reynolds numbers.
Plate exchangers offer 2–5 times the heat transfer area per unit volume, with significant advantages in footprint and weight. Space-limited industrial sites benefit greatly. No clearance is needed for tube bundle removal, further reducing space requirements.
For the same heat transfer area, plate heat exchangers are 40–60% cheaper. Frames allow easy plate removal for cleaning, ideal for frequent maintenance. Shell-and-tube units require more complex cleaning and specialized equipment.
Shell-and-tube exchangers suit cases with small temperature differences and infrequent shell-side cleaning. Plate heat exchangers are suitable for high efficiency, space-limited, frequently cleaned operations but are generally limited to ≤2.5 MPa and ≤250°C, and narrow channels can be blocked by large particles or fibers.
Both shell-and-tube and plate heat exchangers are commonly used in industrial production, each with unique structural features, performance advantages, and application scenarios. Shell-and-tube exchangers offer classic, reliable performance and are widely used in traditional industries, while plate heat exchangers, with their compact and efficient design, are emerging in modern industrial applications. Selecting the right heat exchanger requires comprehensive consideration of process needs, space constraints, budget, and maintenance requirements. Only by choosing the appropriate heat exchanger can industrial production proceed smoothly, energy efficiency improve, and production costs decrease.
