Heat transfer from a tube into a solid

In summary: For example, if the water is coming out of the tubes at a high velocity, erosive wear and tear on the tubes will occur. Additionally, if the water is coming out of the tubes at a lower velocity, corrosion can set in and the tubes will need to be replaced more often.
  • #1
cgw
42
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What is the effect of different tube material (conductivity) on the heat transfer from water in an infinite tube to a surrounding infinite solid?

The actual practical application is transfer of heat from hot water (~180F) in 3/4" tubes into sand for heat storage (and then the transfer back). What is the difference between using type L copper tubbing and PEX tubing.
 
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  • #2
So you are trying to design a heat exchanger with the hot fluid being water and the cold material around the tubes being sand?

To answer your question about tube material from a pure heat transfer view point, the obvious answer is the material with the higher thermal conductivity will transfer the most heat.

But you need to consider effects such as, what is the maximum flow velocity you can have in the tubes before erossion becomes a problem. For copper the usually velocity range for water is about 4 - 8 ft/s depending on the quality of the water. You don't want to have to shutdown to repair/replace tubes every week.

You will also want to look at the effects of how tightly you pack the sand. Loosley packed sand vs tightly packed sand. That can effect your tube material and wall thickness. Since, for this design, you will want to use thin walled tubes so as to minimize wall losses and at the same have sufficient strength against buckling/collapse from the sand.

Thanks
Matt
 
  • #3
The only question is the difference between PEX and copper pipe. All else would remain equal. So the question is (I think) what effect would the difference in conductivity have on the over all resistance between the deep sand and the water (per foot).
 
  • #4
Allowing a higher heat flux with a more conductive material to enter the sand, the deeper the heat can penetrate. This can be modeled quite easily to obtain a ball park value with some assumptions placed on the sand packing density.

See "Introduction to Heat Transfer" by Incropera and Dewitt.

Thanks
Matt
 
  • #5
Effect on what? heat flux?, outlet temperature?

Pipe material with higher conductivity will have lower outlet temperature. About how much the temperature will go down at the outlet will depend upon the relative conductivites of sand & pipe material.

And as matt said, practical difficulties will kick in sooner or lator.
 

FAQ: Heat transfer from a tube into a solid

How does heat transfer occur from a tube into a solid?

Heat transfer from a tube into a solid can occur through three different mechanisms: conduction, convection, and radiation. Conduction is the transfer of heat through direct contact between the tube and the solid. Convection is the transfer of heat through the movement of fluids, such as air or water, across the surface of the solid. Radiation is the transfer of heat through electromagnetic waves.

What factors affect the rate of heat transfer from a tube into a solid?

The rate of heat transfer from a tube into a solid is affected by several factors, including the temperature difference between the two objects, the thermal conductivity of the materials, the surface area of contact, and the distance between the objects. Other factors such as the presence of insulating materials and the type of fluid in contact with the solid can also impact heat transfer.

Can the shape and size of the tube and solid affect heat transfer?

Yes, the shape and size of the tube and solid can affect heat transfer. For example, a larger surface area of contact between the tube and the solid can increase the rate of heat transfer. Similarly, a smaller distance between the objects can also lead to faster heat transfer. Additionally, the shape of the objects can impact the flow of fluids and thus, alter the rate of heat transfer through convection.

How is heat transfer from a tube into a solid quantified?

The rate of heat transfer from a tube into a solid is typically quantified using the heat transfer coefficient, which is a measure of the rate of heat transfer per unit area of contact. This coefficient takes into account the properties of the materials, the temperature difference between the objects, and other factors that affect heat transfer. It is often expressed in units of watts per square meter per Kelvin (W/m2K).

Can heat transfer from a tube into a solid be controlled or manipulated?

Yes, heat transfer from a tube into a solid can be controlled and manipulated through various methods. These can include using insulating materials to reduce heat transfer, adjusting the temperature difference between the objects, or altering the properties of the materials to increase or decrease thermal conductivity. Additionally, heat transfer can also be affected by external factors such as air flow or the presence of other objects in the surrounding environment.

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