Tecnología de transferencia de calor mejorada para intercambiadores de calor

Heat exchangers play a crucial role in many industrial processes, primarily by improving energy utilization efficiency through effective heat exchange. To achieve this, enhanced heat transfer technologies have emerged, aimed at increasing the heat transfer efficiency of heat exchangers while reducing energy consumption. These technologies can be broadly categorized into active and passive enhancement methods based on their implementation.

Enhanced Heat Transfer Technology in Heat Exchangers

Enhanced heat transfer technology in heat exchangers can be categorized into active and passive methods. Active techniques rely on external energy sources, such as fluid stirring and vibration, to significantly improve heat transfer efficiency, but they require additional equipment and energy, which limits their use. In contrast, passive techniques enhance fluid flow by modifying the heat transfer surface or adjusting flow channel shapes without external energy. These methods are simple and cost-effective, making them widely applicable in industries such as chemical, petroleum, and HVAC.

1. Active Enhanced Heat Transfer Technologies

Active enhancement technologies rely on external energy inputs, such as fluid agitation, surface vibration, fluid oscillation, and the application of electrostatic or magnetic fields. While these methods can significantly improve heat transfer performance, their implementation is often complex and typically requires additional equipment and energy support, which limits their practical application. For example, although magnetic and electrostatic fields can theoretically improve fluid flow conditions, the associated equipment costs and maintenance requirements can hinder their widespread adoption.

2. Passive Enhanced Heat Transfer Technologies

In contrast, passive enhancement technologies do not require external energy. Instead, they enhance fluid flow characteristics by modifying the heat transfer surface, adjusting flow channel shapes, or adding flow-directing elements. This approach primarily involves altering the geometry of pipes or increasing surface roughness to induce disturbances in the fluid boundary layer, thereby improving heat transfer efficiency. Passive enhancement methods are simpler to operate, cost-effective, and widely applicable in heat exchange equipment across industries such as chemical processing, oil, and HVAC.

Development Stages of Enhanced Heat Transfer Technologies

The development of enhanced heat transfer technologies has progressed through five distinct stages, each characterized by unique technological innovations.

Smooth Surface Stage: Traditional heat exchangers feature smooth surface designs, resulting in lower heat transfer performance.

Roughened Surface Stage: By artificially increasing surface roughness, the contact area between the fluid and the heat transfer surface is enhanced, improving heat exchange capacity.

Insert Disturbance Stage: The introduction of inserts (such as baffles or flow dividers) within the heat exchanger changes the flow pattern, increases turbulence intensity, and enhances heat transfer efficiency.

Jet Disturbance Stage: Jet flow technology introduces fluids to create significant flow disturbances, further enhancing heat exchange effects.

Swirler Stage: Technologies such as swirlers are employed to improve fluid flow characteristics within the heat exchanger, promoting boundary layer disruption and increasing overall heat transfer efficiency.

Current research primarily focuses on passive enhancement technologies, especially in shell-and-tube heat exchangers, aiming to maximize the heat transfer rate per unit time and area under equivalent power consumption conditions. This optimization improves resource utilization efficiency, enhances heat exchanger structural design, reduces space occupancy, saves raw materials, and increases productivity.

Enhanced Heat Transfer Methods for Shell-and-Tube Heat Exchangers

For shell-and-tube heat exchangers, the main methods of enhancing heat transfer include:

1. Tube-side Enhanced Heat Transfer

Modifying the shape and surface structure of heat exchange tubes to improve heat transfer effects. Common types of enhanced heat exchange tubes include:
Corrugated Tubes: Achieve a heat transfer coefficient 2 to 4 times higher than smooth tubes, suitable for high-efficiency heat exchange.
Ribbed Tubes: Continuous rolling creates ribs that disturb the fluid, enhancing heat exchange capabilities.
Spiral Flat Tubes: Flattened and twisted smooth round tubes generate rotation in the fluid, increasing mixing and significantly improving heat transfer efficiency.
Converging Tubes: Constrictions along the tube length create vortices that enhance the heat transfer coefficient, though the manufacturing process is relatively complex.
Internal Finned Tubes: Increase internal surface area and promote vortex formation in the fluid, further enhancing heat transfer performance.

2. Shell-side Enhanced Heat Transfer

Introducing enhancement elements (such as baffles or flow disruptors) into the shell side to disturb fluid flow and improve heat exchange.

3. Fluid Property Optimization

Adjusting the physical properties of the fluid (such as viscosity and thermal conductivity) to enhance heat transfer performance by increasing heat capacity and thermal conductivity.

4. Composite Enhancement

Combining multiple enhancement methods to further increase heat transfer efficiency. For instance, integrating internal inserts with optimized flow channel designs can achieve more significant enhancement effects.

5. Use of Internal Inserts

Internal inserts are widely used in shell-and-tube heat exchangers to disturb fluid flow, creating vortices and secondary flows that enhance turbulence intensity and disrupt the laminar boundary layer, accelerating heat exchange between the fluid and the heat transfer tube. Key advantages include:
Simple Manufacturing: Using inserts has minimal impact on existing equipment and is easy to implement compared to altering the tube shape.
Strong Adaptability: Inserts can be directly added to existing heat exchangers and are suitable for various fluid types.
Improved Cleaning: The presence of inserts can effectively reduce sediment buildup, enhancing the overall cleanliness and maintainability of the heat exchanger.

Conclusion

Enhanced heat transfer technologies in heat exchangers play a vital role in improving heat exchange efficiency and reducing energy consumption. With advancements in new materials, the development of smart control systems, and the promotion of multifunctional designs, future heat exchangers will become more efficient and intelligent. Through continuous innovation, businesses can achieve higher production efficiency while minimizing energy consumption and environmental impacts, contributing to the green transformation of industries in the context of global sustainability efforts. Therefore, strengthening research and application of enhanced heat transfer technologies will have a profound impact on improving the overall competitiveness of the industry.