Find Outlet Temp of Cold Stream of Counterflow in Double Pipe Heat Exchanger

In summary, to find the outlet temperature of the cold stream in a double pipe heat exchanger with a counterflow setting, given the mass flow, specific heat, and temperature of the inlet streams for both hot and cold streams, as well as the inner pipe diameter and a minimum temperature difference of 10C between the two liquids, you would use conservation principles (energy and mass) equations.
  • #1
kyta
3
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Given the mass flow, Cp, temp of the inlet streams of both hot and cold streams.
As well as being given the inner pipe diametre of the double pipe heat exchanger.
Also knowing the setting is at counterflow and that the overall heat transfer coefficient and that the temp difference between the two liquids is no less than 10C at any point in the exchanger.

How would you go about finding the outlet temp of the cold stream?

What equations would you use?
 
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  • #2
kyta said:
Given the mass flow, Cp, temp of the inlet streams of both hot and cold streams.
As well as being given the inner pipe diametre of the double pipe heat exchanger.
Also knowing the setting is at counterflow and that the overall heat transfer coefficient and that the temp difference between the two liquids is no less than 10C at any point in the exchanger.

How would you go about finding the outlet temp of the cold stream?

What equations would you use?

Conservation principles (energy and mass).

CS
 
  • #3


To find the outlet temperature of the cold stream in a counterflow double pipe heat exchanger, I would use the heat transfer equation:

Q = UAΔTlm

where Q is the heat transfer rate, U is the overall heat transfer coefficient, A is the heat transfer area, and ΔTlm is the logarithmic mean temperature difference.

First, I would calculate the logarithmic mean temperature difference using the equation:

ΔTlm = (ΔTh1 - ΔTc1) / ln(ΔTh1/ΔTc1)

where ΔTh1 is the temperature difference between the hot stream inlet and outlet, and ΔTc1 is the temperature difference between the cold stream inlet and outlet.

Next, I would use the heat transfer equation to solve for the unknown outlet temperature of the cold stream:

Q = mCpΔTc2

where m is the mass flow rate of the cold stream, Cp is the specific heat capacity of the cold stream, and ΔTc2 is the temperature difference between the cold stream inlet and outlet.

Finally, I would rearrange the equation to solve for ΔTc2 and then add this value to the inlet temperature of the cold stream to find the outlet temperature.

ΔTc2 = Q / (mCp)

Outlet temp of cold stream = Inlet temp of cold stream + ΔTc2

Overall, the equations used to find the outlet temperature of the cold stream in a counterflow double pipe heat exchanger are the heat transfer equation and the logarithmic mean temperature difference equation. It is important to ensure that the temperature difference between the two streams is no less than 10C at any point in the exchanger to maintain efficient heat transfer.
 

FAQ: Find Outlet Temp of Cold Stream of Counterflow in Double Pipe Heat Exchanger

1. How does a double pipe heat exchanger work?

A double pipe heat exchanger works by transferring heat from one fluid to another through a set of parallel pipes. The two fluids flow in opposite directions, allowing for efficient heat transfer through the walls of the pipes.

2. What factors affect the outlet temperature of the cold stream in a counterflow double pipe heat exchanger?

The outlet temperature of the cold stream in a counterflow double pipe heat exchanger is affected by the inlet temperatures of both the hot and cold streams, the flow rates of the two streams, and the overall heat transfer coefficient of the exchanger.

3. How do you calculate the outlet temperature of the cold stream in a double pipe heat exchanger?

The outlet temperature of the cold stream in a double pipe heat exchanger can be calculated using the logarithmic mean temperature difference (LMTD) method or the effectiveness-NTU method. Both methods involve using the inlet temperatures, flow rates, and heat transfer coefficients to determine the outlet temperature.

4. What is the difference between a parallel flow and a counterflow double pipe heat exchanger?

In a parallel flow double pipe heat exchanger, the two fluids flow in the same direction, while in a counterflow exchanger, the two fluids flow in opposite directions. This results in a higher overall heat transfer coefficient and a larger temperature difference between the two streams in a counterflow exchanger, making it more efficient.

5. How can the outlet temperature of the cold stream be optimized in a double pipe heat exchanger?

The outlet temperature of the cold stream can be optimized by adjusting the inlet temperatures and flow rates of the two streams, as well as the design and surface area of the heat exchanger. Regular maintenance and cleaning of the exchanger can also help improve its efficiency and the outlet temperature of the cold stream.

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