Does The Surface Roughness of The Bent Fin Tube Affect Heat Transfer?

‌Effects of Surface Roughness on Heat Transfer in Serpentine Finned Tubes‌

1. Theoretical Basis of Surface Roughness Impact

• ‌Enhanced Fluid Disturbance‌: Surface roughness disrupts the fluid boundary layer along serpentine finned tubes. While a smooth surface maintains a stable boundary layer, roughness generates vortices and turbulence near the wall. This intensifies fluid mixing, accelerating heat transfer between high- and low-temperature fluid regions.
• ‌Increased Heat Transfer Area‌: Microscopic surface irregularities enlarge the effective contact area between the fluid and tube wall. Although the macroscopic geometry remains unchanged, the augmented surface area facilitates greater heat exchange per unit time.

2. Impact Under Different Flow States

3. Challenges and Mitigation Strategies

• ‌Increased Flow Resistance‌: Rough surfaces elevate frictional resistance, raising energy consumption. Excessive resistance may offset heat transfer gains.
• ‌Fouling Accumulation‌: Rough textures trap particulate matter, forming insulating fouling layers that degrade thermal efficiency. Regular cleaning is essential.
• ‌Optimization Approach‌: Balance roughness to maximize heat transfer while minimizing resistance. Ideal surface roughness (e.g., Ra ≤ 0.8 μm) must be determined via simulations and experiments.

4. Production Processes for Serpentine Finned Tubes

Concluzie

Surface roughness significantly enhances heat transfer in serpentine finned tubes by disrupting boundary layers and enlarging effective surface area, particularly in turbulent flow. Însă, excessive roughness increases flow resistance and fouling risks. Optimized roughness parameters (Ra ≈ 0.4–0.8 μm) and regular maintenance are critical for efficiency. Production processes prioritize precision fin welding and controlled roughness to achieve performance targets.

Does the surface roughness of the bent fin tube affect heat transfer?

1. Theoretical basis for the influence of the surface roughness of the bent fin tube on heat transfer

Enhance fluid disturbance: When the fluid flows through the bent fin tube, the surface roughness will destroy the boundary layer of the fluid.

The boundary layer of the fluid on the smooth surface is relatively stable, while the rough surface will cause more vortices and turbulence in the fluid near the tube wall. These vortices and turbulence increase the mixing degree of the fluid, so that the high-temperature part of the hot fluid and the low-temperature part of the cold fluid are more fully in contact, thereby accelerating the heat transfer rate.

Increase the heat transfer area: The surface roughness will increase the actual heat transfer area of ​​the serpentine fin tube at the microscopic level. Although the size of the fin tube remains unchanged from a macroscopic point of view, the unevenness of the rough surface increases the contact area between the fluid and the tube wall. This means that in the same time and space, more heat can be transferred through this increased area.

2. Differences in the influence of different fluid states on bent fin tubes

Laminar flow state: In the laminar flow state, the flow of the fluid is relatively stable, and the stratified flow characteristics are obvious. At this time, the effect of the surface roughness of the serpentine fin tube on heat transfer is relatively small. Because the main flow direction of the fluid in laminar flow is relatively regular, the local disturbance caused by roughness is difficult to spread to the entire fluid layer. Însă, when the roughness reaches a certain degree, tiny vortices may still be generated locally, and these vortices will enhance heat transfer within a certain range.

Turbulent state: When the fluid is in a turbulent state, the effect of the surface roughness of the serpentine fin tube on heat transfer is more significant. Turbulence itself has a strong mixing characteristic, and the roughness further aggravates this mixing. The vortices and turbulence caused by the roughness interact to make the heat transfer faster.

3. Adverse effects and countermeasures of the surface roughness of serpentine bent fin tubes

Increase flow resistance: While surface roughness enhances heat transfer, it also increases the flow resistance of the fluid. The rough surface will increase the friction between the fluid and the tube wall, resulting in the fluid needing to overcome greater resistance during the flow process. This will not only increase the energy required to transport the fluid, but may also limit the flow rate of the fluid, thereby affecting the heat transfer effect.

In some systems that are sensitive to energy consumption, excessive flow resistance may significantly increase the operating cost of the system. In order to balance the relationship between heat transfer enhancement and increased flow resistance, the surface roughness needs to be optimized.

Through experiments and numerical simulations, an optimal roughness value that can effectively enhance heat transfer and control flow resistance within an acceptable range is found.

Dirt deposition and cleaning: Rough surfaces are more likely to adsorb and deposit dirt. Impurities, particles and other substances in the fluid are more likely to adhere to rough surfaces. Over time, these dirt will form a layer of thermal resistance, hindering heat transfer. In cooling systems with poor water quality, the roughness of the serpentine fin tube surface may cause scale and other dirt to accumulate rapidly, reducing heat transfer efficiency.

The bent fin tube needs to be cleaned and maintained regularly to ensure its surface cleanliness and maintain good heat transfer performance.