2 replies to this topic

[Sadananda Konchady]

This is about the pressure drop specification for a plate heat exchanger application required in our process. Would allowable pressure drop of 0.5 bar be appropriate or should it be 0.8 bar?

In Plate Heat Exchanger application as a user, what is the optimal pressure drop specification for a case with almost equal flow of good quality water on both sides and temperature change (only sensible heat transfer) on both sides. Relatively, there seems to be a substantial pressure drop used up in the inlet and outlet nozzles, besides the pressure drop effectively used through the channels used in actual heat transfer. The flow conditions are as follows --

Hot water / Cold water

Water flow, kg/s 600 600

Temperature In, deg. C 130 120

Temperature Out, deg. C 125 125

Fouling factor may be considered as practically zero.

Thank you for your comments.

[palusa]

Normally PHE's pressure drops are determined by the flow through plate channels.
Within the plate, the friction factors are in general much higher than those inside a tube for the same Reynolds number. However, nominal velocities are low and plate lengths limited, so that the term v²L/2g in the pressure drop equation is much smaller than those normally encountered in tubulars.
The friction factor is correlated with:
ΔP =f ρ v²L/2g ; f = B/Re^y
where y varies from 0.1 to 0.4 in turbulence and B is a constant characteristic of the plate.

In the specific, your PHE looks pretty big (duty ca. 12MW) ... I estimated 0.9 bar pressure drops (0.2 through ports + 0.7 through channels) so I suggest to verify if your system can allow for at least 1 bar pressure drops.

Hope this can help.

_Lf

[Sadananda Konchady]

Thanks, Palusa for the suggestion to increase the permissible pressure drop to 1 bar. There must be an optimum from the customer's view point since the pumping power required would also increase as the permissible pressure drop is increased.
I will check this further when floating enquiries to PHE vendors.

Regards,,

Escape

Normally PHE's pressure drops are determined by the flow through plate channels.
Within the plate, the friction factors are in general much higher than those inside a tube for the same Reynolds number. However, nominal velocities are low and plate lengths limited, so that the term v²L/2g in the pressure drop equation is much smaller than those normally encountered in tubulars.
The friction factor is correlated with:
ΔP =f ρ v²L/2g ; f = B/Re^y
where y varies from 0.1 to 0.4 in turbulence and B is a constant characteristic of the plate.

In the specific, your PHE looks pretty big (duty ca. 12MW) ... I estimated 0.9 bar pressure drops (0.2 through ports + 0.7 through channels) so I suggest to verify if your system can allow for at least 1 bar pressure drops.

Hope this can help.

_Lf