Thermal transfer improvement from adding fins

  • Thread starter leonhart88
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In summary, the conversation discusses the design of a heater for cylindrical tubes and the potential benefits of adding fins to improve thermal transfer. However, calculating the effectiveness of the fins is not straightforward and may require further experimentation. Suggestions are made for using copper fins and insulating the outside of the rack, as well as potentially replacing the top of the tubes with a less conductive material.
  • #1
leonhart88
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Hi All,

I'm designing a heater for some cylindrical tubes. In my original design, I simply had a flat plate contacting the bottom of the tube. Since the tubes are only conducting on the bottom, the temperature of the contents in the tube are somewhat off from the actual base temperature. I was curious if adding "fins" would help improve the thermal transfer to the tube contents. Please see the attached picture for the fin idea. Note that the tubes are in a rack and the entire tube/rack assembly sits on top of this plate (the rack is not shown). Therefore, the geometry of the fins cannot be changed, as this is the only way it will fit into the rack. The rack also provides some insulation between tubes. Lastly, I don't need to heat the top-half portion of the tube.

I am not sure how to calculate if the fins will be an improvement. In my experiments with the flat plate, the base temperature is set to 68C and then contents in the tube read 60C. I assume that if I can figure out how much extra heat the fins add to the tube via convection (there is a small clearance between the tube diameter and the fins), I can roughly determine what my steady state temperature would be (since I know that currently, losses are preventing the tube from reaching 68C).

Can anyone provide some advice/suggestions on calculating this out?


Thanks!
 

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  • #2
They will probably help but it's not easy to calculate how effective they will be. The reason the tubes aren't at the same temperature as the base is because there is an energy flow from the base through the tubes. There is an analogy with electricity... a current flowing through a resistance produces a voltage drop. If you reduce the resistance the voltage drop will be lower but unless you know the current you cannot calculate how much lower the voltage drop will be. Likewise unless you know how much power is flowing from the base through the path of interest you can't calculate the temperature drop.

Using copper fins and insulating the outside of the rack is likely to help. The top of the tubes are likely to conduct a lot of the heat away - can you replace the top of the tubes with a different material that doesn't conduct heat as well?
 

Related to Thermal transfer improvement from adding fins

1. How do fins improve thermal transfer?

Fins improve thermal transfer by increasing the surface area of an object, which allows for more heat to be transferred to or from the object. This is because heat transfer occurs at the surface of an object, so a larger surface area means more heat can be transferred.

2. What materials are commonly used for fins?

Commonly used materials for fins include aluminum, copper, and steel. These materials have high thermal conductivity, meaning they are able to transfer heat efficiently.

3. Can fins improve thermal transfer in all applications?

No, fins are most effective in applications where there is a significant temperature difference between the object and its surroundings. This allows for a greater heat transfer rate, making fins more beneficial in these situations.

4. How do the size and shape of fins impact thermal transfer?

The size and shape of fins can greatly impact thermal transfer. A larger fin surface area will result in a higher heat transfer rate, but may also increase air resistance. The shape of the fins can also affect heat transfer, with certain shapes (such as pin fins) being more efficient than others.

5. Are there any drawbacks to using fins for thermal transfer improvement?

While fins can greatly improve thermal transfer, there are some potential drawbacks to consider. These include increased cost and complexity in design and manufacturing, as well as potential issues with fouling or corrosion if not properly maintained. Additionally, in some cases, fins may not provide a significant improvement in thermal transfer and can actually impede airflow and decrease efficiency.

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