How to Start Designing a Plate Heat Exchanger?

[Alfred0812]

I am currently working on my college project about the design and optimization of plate heat exchanger. However, i have no idea where to start the project. Here is my first thought:
- I set the hot and cold fluid to be water, 90 degC for the hot inlet and 30 degC for the cold inlet.
- 50mm inlet and outlet portholes.
- 500mm height and 300mm wide for the plate ( 500x300 is the full dimension of the plates).

I did some research about the plate and got that the plate have chevron corrugation which help in heat transfer, while the corrugation inclination angle has a range of 25 deg - 65 deg.

I also found that the design must consider the pressure, mass flow rate, fluid velocity and many other parameters. I am not sure how to begin the design and what parameters should I emphasize on. Besides, since the PHE is designed by myself, is that possible to further optimize it?

p/s: I have no idea about the difficulty when i choose this title. Need a lot of helps on my project.

 

[Baluncore]

Are you aware that you can get twice the heat exchange by using a counter current flow exchanger.
https://en.wikipedia.org/wiki/Countercurrent_exchange
How can you increase the time available for heat exchange, or reduce the distance heat must be conducted through the water or plate ?
Does it have to remain a flat plate or can it be rolled into two coaxial tubes, one inside the other ?

 

[Alfred0812]

Are you aware that you can get twice the heat exchange by using a counter current flow exchanger.
https://en.wikipedia.org/wiki/Countercurrent_exchange
How can you increase the time available for heat exchange, or reduce the distance heat must be conducted through the water or plate ?
Does it have to remain a flat plate or can it be rolled into two coaxial tubes, one inside the other ?

Hello Baluncore, as what i know the countercurrent flow is 2 fluids flow in opposite direction, the heat transfer efficiency is much more higher than that of concurrent flow. I am not sure whether the heat exchange by countercurrent can be 4 times(?) higher than that of concurrent.
For the time available for heat exchange, can i increase the distance from the inlet port to outlet port? Or reduce the fluid velocity? In this case, does the fluid pressure affect the time for heat exchange? Can I take the distance of heat conducts as the thickness of plate? Heat transfer occurs through hot fluid > plate wall > cold fluid, can i just emphasize on the heat transfer between fluid and wall and neglect the heat transfer within the fluid?
I think my thought of plate heat exchanger is fluid pass through the plates, no tubes involve.

 

[Baluncore]

I am not sure whether the heat exchange by countercurrent can be 4 times(?) higher than that of concurrent.

There is no 400%.
If two fluids counterflow then exchange between the two can be close to 100%.
If two fluids flow parallel then exchange between the two is limited to 50%.
See; https://en.wikipedia.org/wiki/Countercurrent_exchange#Cocurrent_flow.E2.80.94half_transfer

For the time available for heat exchange, can i increase the distance from the inlet port to outlet port? Or reduce the fluid velocity?

Yes. That must be considered. But is it better to use a wider channel or a longer channel? You must allocate the available volume by cost benefit analysis.

In this case, does the fluid pressure affect the time for heat exchange?

Pressure is not an important exchange parameter. But the pressure needed to push fluid through the exchanger will depend on design of the fluid path.

Can I take the distance of heat conducts as the thickness of plate?

Plate material thickness should be reduced for better transfer, but must withstand the pressure differential between the ports and fluids.

Heat transfer occurs through hot fluid > plate wall > cold fluid, can i just emphasize on the heat transfer between fluid and wall and neglect the heat transfer within the fluid?

Heat transfer within fluid is most important. That is why turbulence is sometimes encouraged to avoid laminar flow.
The plate surface is also important as scale deposits or oil may prevent heat flow on either side of a plate.

I think my thought of plate heat exchanger is fluid pass through the plates, no tubes involve.

Yes. Single plates separate alternate fluids A and B. Can you arrange for fluid A inlet at the same end as fluid B outlet. B inlet at A outlet. That will give you counterflow efficiency. But how do you arrange the holes and seals between plates to get the best flow path?

I set the hot and cold fluid to be water, 90 degC for the hot inlet and 30 degC for the cold inlet.

What is the flow rate of the fluids? Are the flow rates different?
What will final temperatures be? How much heat do you need to exchange?

Everything will have a cost and a benefit. You must establish the relationships between all parameters of the design. Then solve the system of relationships for a minimum cost and a maximum benefit. You will need to know the cost of energy and the time to pay off the investment in the exchanger.

 

[Nidum]

@Alfred0812 You need to do some basic research as preparation for this project .

Try putting the obvious keywords into a search engine :

Plate heat exchanger design or Plate heat exchanger calculations .

You will find lots of good information .