Heat Transfer in a heat exchanger.

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Discussion Overview

The discussion revolves around the design and calculations related to a heat exchanger, specifically focusing on the cooling of water from 150°F to 80°F using chilled water. Participants explore various parameters such as flow rates, pressure, material specifications, and the overall heat transfer coefficient, as well as structural considerations like hoop stress.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • Participants express confusion regarding the calculations needed for the heat exchanger design, including the overall heat transfer coefficient and hoop stress.
  • Some participants inquire about the specific calculations required to determine the heat transfer coefficient and the necessary surface area for cooling.
  • A participant suggests using the formula for overall heat transfer coefficient, indicating the relationship between inner and outer heat transfer coefficients.
  • There is a request for clarification on which specific questions are understood and which are confusing, indicating a need for targeted discussion.
  • Concerns are raised about the duplication of posts, emphasizing the need for concise communication.

Areas of Agreement / Disagreement

Participants generally agree on the need for calculations related to the heat exchanger design, but there is no consensus on the specific methods or formulas to be used. The discussion remains unresolved with multiple competing views on how to approach the calculations.

Contextual Notes

Participants have not fully clarified assumptions regarding the heat exchanger design, such as the specific type of heat exchanger or the conditions under which calculations are made. There are also unresolved mathematical steps related to the heat transfer coefficient and hoop stress calculations.

de312
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So this concept is confusing me.

You have a 20GPM, 150Degree F, 40PSIG water coming into a heat exchanger through a 1" diameter pipe.

Chilled water is available for cooling from a 6" diameter line at 40 Degrees F, With a pressure of 110PSIG and a flow of 270GPM.

The original solution needs to be cooled from 150 degrees to 80 degrees exiting in a 1.5" line.

  1. The external vessel of the exchanger needs to be 316 stainless steel, any piping or tubing may be of any appropiate material as long as it is schedule 40.
  2. What would be the overall heat transfer coefficient. What would be the hoop stress with a safety factor of 2.0.
  3. Estimate chilled water flow requirements.
  4. What would be the size of the shell, and how many tubes and their size would be required to properly cool the liquid.

This is confusing me ~.~
 
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So this concept is confusing me.

You have a 20GPM, 150Degree F, 40PSIG water coming into a heat exchanger through a 1" diameter pipe.

Chilled water is available for cooling from a 6" diameter line at 40 Degrees F, With a pressure of 110PSIG and a flow of 270GPM.

The original solution needs to be cooled from 150 degrees to 80 degrees exiting in a 1.5" line.

  1. The external vessel of the exchanger needs to be 316 stainless steel, any piping or tubing may be of any appropiate material as long as it is schedule 40.
  2. What would be the overall heat transfer coefficient. What would be the hoop stress with a safety factor of 2.0.
  3. Estimate chilled water flow requirements.
  4. What would be the size of the shell, and how many tubes and their size would be required to properly cool the liquid.

This is confusing me ~.~
 
So this concept is confusing me.

You have a 20GPM, 150Degree F, 40PSIG water coming into a heat exchanger through a 1" diameter pipe.

Chilled water is available for cooling from a 6" diameter line at 40 Degrees F, With a pressure of 110PSIG and a flow of 270GPM.

The original solution needs to be cooled from 150 degrees to 80 degrees exiting in a 1.5" line.

  1. The external vessel of the exchanger needs to be 316 stainless steel, any piping or tubing may be of any appropiate material as long as it is schedule 40.
  2. What would be the overall heat transfer coefficient. What would be the hoop stress with a safety factor of 2.0.
  3. Estimate chilled water flow requirements.
  4. What would be the size of the shell, and how many tubes and their size would be required to properly cool the liquid.

This is confusing me ~.~
 
I would first ask which questions do you understand and which ones are confusing?

Much can be said about these topics - good to know where to start.
 
I wanted to try and clarify this. If it is just a double tube simple heat exchanger like this shown here.

http://i56.tinypic.com/34znmti.png

*What is the calculation to calculate the heat transfer coefficient.
*How much surface area would be required between the two pipes for the solution to cool from 150 degrees to 80 degrees.
 
I wanted to try and clarify this. If it is just a double tube simple heat exchanger like this shown here.

http://i56.tinypic.com/34znmti.png

*What is the calculation to calculate the heat transfer coefficient.
*How much surface area would be required between the two pipes for the solution to cool from 150 degrees to 80 degrees.
 
I wanted to try and clarify this. If it is just a double tube simple heat exchanger like this shown here.

http://i56.tinypic.com/34znmti.png

*What is the calculation to calculate the heat transfer coefficient.
*How much surface area would be required between the two pipes for the solution to cool from 150 degrees to 80 degrees.
 
For the value of U, I believe you need to use the fact that

\frac{1}{U} = \frac{1}{h_o} + \frac{1}{h_i}

where ho is the outer heat transfer coefficient and hi is the inner heat transfer coefficient.

so essentially

\frac{1}{U} = \frac{1}{h_{cold}} + \frac{1}{h_{hot}}

yes it is just like that in your diagram. You would need to look up how pressure and diameter relates to stress for the hoop stress.

For the chilled water requirements, you will just need a simple heat balance on the system.
 
Please do not duplicate posts.
 
  • #10
de312 said:
So this concept is confusing me.

You have a 20GPM, 150Degree F, 40PSIG water coming into a heat exchanger through a 1" diameter pipe.

Chilled water is available for cooling from a 6" diameter line at 40 Degrees F, With a pressure of 110PSIG and a flow of 270GPM.

The original solution needs to be cooled from 150 degrees to 80 degrees exiting in a 1.5" line.

  1. The external vessel of the exchanger needs to be 316 stainless steel, any piping or tubing may be of any appropiate material as long as it is schedule 40.
  2. What would be the overall heat transfer coefficient. What would be the hoop stress with a safety factor of 2.0.
  3. Estimate chilled water flow requirements.
  4. What would be the size of the shell, and how many tubes and their size would be required to properly cool the liquid.

This is confusing me ~.~

Multiple threads merged. Please do not multiple/duplicate post again on the PF.
 

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