Tubular heat exchanger

Structural Principles

Basic Structure

Shell: The outer shell of the heat exchanger, usually welded from steel plates, used to house the tube bundle and fluid.

Tube Bundle: Composed of multiple heat exchange tubes, it is the core component for heat transfer. Heat exchange tubes can be straight, U-shaped, or spiral, typically made of materials such as carbon steel, stainless steel, or copper.

Tube Sheet: Used to fix the tube bundle, connecting the heat exchange tubes to the shell and preventing the tube bundle from vibrating under fluid impact.

Ends: Installed at both ends of the shell, used to seal the shell and form fluid channels.

Baffles: Installed inside the shell, used to change the flow direction of the shell-side fluid, increasing the turbulence and improving heat exchange efficiency.

Working Principle

The working principle of a tubular heat exchanger is based on heat conduction. One fluid flows inside the tubes, and another fluid flows outside the tubes (shell side). Heat is transferred from the high-temperature fluid to the low-temperature fluid through the tube walls, achieving heat exchange.

To improve heat exchange efficiency, the shell-side fluid changes its flow direction multiple times through the baffles, creating turbulence and increasing the contact area between the fluid and the tube walls.

Features

Advantages

Simple Structure: Relatively simple to design and manufacture, resulting in lower costs.

High Reliability: Robust structure with strong pressure resistance, suitable for harsh conditions such as high pressure and high temperature.

Strong Adaptability: Can adapt to different fluid properties and operating conditions; by changing the tube bundle arrangement and tube diameter, different heat exchange requirements can be met.

Easy Maintenance: The tube bundle can be easily removed for cleaning and repair, facilitating maintenance.

Disadvantages

Relatively Low Heat Exchange Efficiency: Compared to plate heat exchangers, tube heat exchangers have a lower heat transfer coefficient, requiring a larger heat exchange area to achieve the same heat exchange effect.

Larger Size: Due to the larger heat exchange area, the equipment is relatively large, occupying more space.

Difficult Cleaning: Cleaning the inside of the tubes is relatively difficult, especially for fluids containing impurities, which easily form scale inside the tubes, affecting heat exchange efficiency.

Main Types

Fixed Tube Sheet Heat Exchanger

Structural Features: The tube bundle is fixed at both ends to the tube sheet, which is welded to the shell. This structure is simple and low-cost, but it cannot eliminate thermal stress and is suitable for applications with small temperature differences.

Applications: Suitable for applications where the temperature difference between the shell-side and tube-side fluids is small (generally less than 50℃).

Floating Head Heat Exchanger

Structural Features: One end of the tube sheet is fixed to the shell, while the other end can float freely within the shell, thus eliminating thermal stress. The floating head end can be easily disassembled for cleaning and maintenance.

Applications: Suitable for applications where the temperature difference between the shell-side and tube-side fluids is large (generally greater than 50℃).

U-Tube Heat Exchanger

Structural Features: The tube bundle is U-shaped, with both ends fixed to the same tube sheet. This structure allows for free expansion and contraction, eliminating thermal stress, but cleaning the inside of the tubes is difficult.

Applications: Suitable for high-temperature, high-pressure, and large-temperature-difference applications, especially suitable for fluids where the cleanliness requirements inside the tubes are not high.

Stuffed Gland Heat Exchanger

Structural Features: One end is fixed with a tube sheet, and the other end is sealed with a stuffing gland, facilitating disassembly and cleaning. However, the stuffing gland seal has relatively low reliability and is prone to leakage.

Applications: Suitable for applications where the tube-side fluid is clean and scale-free.

Application Areas

Industrial Sector

Petroleum and Chemical Industry: Used for preheating crude oil, cooling cracked gas, and heat recovery in various chemical reaction processes.

Power Industry: Used in power plant condensers, coolers, and other equipment to cool turbine exhaust steam and recover waste heat.

Metallurgical Industry: Used for cooling high-temperature melts and recovering waste heat, improving energy efficiency.

Food and Pharmaceutical Industry: Used in the heating, cooling, and sterilization processes of food and pharmaceuticals to ensure product quality and safety.

Civilian Sector

Heating Systems: Used for heat exchange in heating stations, transferring heat from the heating network's hot water to the user's hot water system.

Air Conditioning Systems: Used for heat exchange between cooling water and chilled water, ensuring the normal operation of the air conditioning system.

Selection and Maintenance

Selection Key Points

Heat Exchange Calculation: Determine the heat to be transferred based on process requirements and select an appropriate heat exchange area.

Fluid Properties: Consider factors such as fluid temperature, pressure, flow rate, and corrosivity to select suitable pipe and shell materials.

Installation Space: Select the appropriate heat exchanger model and size based on the available installation space.

Economy: Comprehensively consider the purchase cost, operating cost, and maintenance cost to select equipment with a high cost-performance ratio.

Maintenance Measures

Regular Inspection: Regularly inspect the tube bundle and shell for corrosion and promptly identify and address leaks.

Cleaning and Maintenance: Regularly clean the tube bundle and shell to remove dirt and ensure heat exchange efficiency. Use appropriate cleaning agents to avoid corrosion.

Overload Prevention: Avoid operating the equipment under conditions exceeding design pressure and temperature to prevent equipment damage.

Record Operating Parameters: Record the equipment's operating parameters, such as fluid temperature, pressure, and flow rate, to facilitate timely detection and handling of abnormalities.

Tube heat exchangers are widely used heat exchange equipment, characterized by simple structure, high reliability, and strong adaptability. In practical applications, appropriate models should be selected based on specific needs, and maintenance and management should be strengthened to ensure long-term stable operation.