Pressure drop due to friction and condensation

In summary: So the heat exchanger will end up with more deposits and will not be as efficient. In summary, the contact person is calculating the pressure drop in the heat exchanger based on a high flow rate of vapour, which is why the pressure drop is excessive.
  • #1
Meteorrain
1
0
Hello,

I'm struggling with the following problem. We have a dryer in our plant which evaporates acetone and with a blower the vapour is driven to a scrubber. However the efficiency of the scrubber is not sufficient and that is why I want to place a plate heat exchanger in the vapour line to cool the gas (a portion of the vapour will be condensated).

The blower is almost at its limits and we don't want more pressure loss to prevent a too low flowrate. Now the company of the plate heat exchangers calculated a pressure drop of 50 mbar which is too much.

However a pressure drop due to condensation in the heat exchanger will increase the flowrate. But a pressure drop in the heat exchanger due to friction of the plates will decrease the flow. I tried to explain this to the contact person, but the pressure drop is calculated with their software and all he knows is that it is the pressure drop from inlet to outlet.

So I am wondering if this 50mbar pressure loss should be considered as total energy loss and thus the blower needs to deliver an additional 50mbar pressure to cover this. Or doesn't my point of view makes sense?
 
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  • #2
Im not sure if I understand your problem fully but I have a bit of experience in condensation pressure drop. For your case, you are going to have pressure losses due to a combination of 3 effects; frictional losses, momentum losses and static/gravitational losses. If your hex is mounted horizontally, you can neglect the gravitational losses. In addition, as your flow is condensing, you will have momentum recovery (not loss) although if you say only a small amount of vapour is condensing, this may not matter much. It depends on your dryness fraction leaving the hex. My guess, is the 50mbar given to you is solely based on frictional losses, although to calculate this, it must be based on some flow rate of vapour? Obviously 50mbar is goning to seem excessive if the calculation was based on a high flow rate of vapour
 
  • #3
I'm afraid condensation will even increase the pressure lost, due to droplets forming inside heat exchanger
 

1. What causes pressure drop due to friction and condensation?

Pressure drop due to friction and condensation is caused by the resistance encountered by a fluid as it flows through a pipe or channel. This resistance is due to the friction between the fluid and the walls of the pipe, as well as the formation of a thin layer of liquid on the walls due to condensation.

2. How does pressure drop due to friction and condensation affect fluid flow?

The pressure drop caused by friction and condensation can significantly impact the flow rate of a fluid. As the pressure decreases, the fluid's velocity increases, resulting in a higher flow rate. However, if the pressure drop is too large, it can lead to flow instabilities and even flow reversal.

3. What factors affect pressure drop due to friction and condensation?

The amount of pressure drop due to friction and condensation is influenced by several factors, including the fluid's viscosity, the pipe's diameter, the surface roughness of the pipe, and the flow rate of the fluid. Additionally, the presence of any obstructions or changes in the pipe's direction can also impact the pressure drop.

4. How is pressure drop due to friction and condensation calculated?

The pressure drop due to friction and condensation can be calculated using various equations, such as the Darcy-Weisbach equation or the Colebrook-White equation. These equations take into account factors such as the fluid properties, pipe characteristics, and flow rate to determine the pressure drop.

5. How can pressure drop due to friction and condensation be minimized?

To reduce the pressure drop caused by friction and condensation, engineers often use methods such as increasing the pipe diameter, smoothing the inner surface of the pipe, and using fluids with lower viscosities. Additionally, improving the design and layout of the piping system can also help minimize pressure drop.

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