Question about heating a fluid through a wall

In summary, the conversation is about a problem involving heating a fluid in a pipe and determining the necessary length of the pipe for the fluid to reach a desired temperature. The fluid must also undergo a phase change from liquid to gas. The conversation also includes suggestions for finding the mass of fluid and the amount of heat needed for the process. It is noted that heating the gas after the phase change may be more difficult and may require the gas to be at high pressure.
  • #1
Green Zach
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Hello, I am working on a project this summer and I have run into a problem that I need a bit of help with. If I heat a fluid (water or some refrigerant) in a pipe with cross sectional area A and the fluid has a velocity V through the pipe then how long does the pipe need to be for a given heat source to heat the fluid to some desired temperature T? The fluid must also go through a phase change into a gas at some point in the heating process. No this is not a homework problem... I am going into my third year of aerospace engineering and I just don’t know much about this subject. Any help will be greatly appreciated.
 
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  • #2
Find the mass of fluid going throug the pipe in 1 second (volume x density).

Then find the amount of heat needed to raise the temperature of the fluid and change its phase.

That will tell you how muich power (heat energy / second) you need to put into the pipe.

Finding the temperature gradient through the pipe and into the fluid is a different question, and much harder to solve.

You might want to think about the fact that it will be relatively easy to heat the liquid but harder to heat the gas after the phase change, unless the gas is at high pressure to increase its density and reduce its flow velocity, so it stays in the heating pipe for longer.
 

1. How does heat transfer occur through a wall?

Heat transfer through a wall occurs through the process of conduction, where heat energy is transferred from one molecule to another through direct contact. In this case, the heat energy is transferred from the hot fluid on one side of the wall to the cooler fluid on the other side.

2. What factors affect the rate of heat transfer through a wall?

The rate of heat transfer through a wall is affected by several factors, including the temperature difference between the two fluids, the thickness and material of the wall, and the surface area of the wall.

3. How can the temperature of the fluid be controlled while heating it through a wall?

The temperature of the fluid can be controlled by adjusting the temperature of the heat source, the flow rate of the fluid, and the properties of the wall such as its thickness and material. Additionally, insulation can be used to reduce heat loss through the wall.

4. Is there a limit to how much heat can be transferred through a wall?

There is no limit to the amount of heat that can be transferred through a wall; it depends on the size and efficiency of the heat source, the properties of the wall, and the flow rate of the fluid. However, as the temperature difference between the two fluids increases, the heat transfer rate will eventually reach a steady state.

5. How does heating a fluid through a wall affect the overall energy efficiency?

Heating a fluid through a wall can have both positive and negative effects on energy efficiency. On one hand, it can save energy by reducing the need for an additional heating source. However, it can also result in heat loss through the wall, decreasing the overall efficiency. Proper insulation and choosing an efficient heating source can help mitigate this issue.

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