3 replies to this topic

[Ranga v]

We have air to water exchanger 2 passes with extended fins,Due to poor MOC of tubes tube failure is frequent and about 20 tubes out of total 189 had been pluged.
As a result what will be the net loss of heat transfer & other changes in fluid dynmaics.Shell side v=2.5m/s and tube side is 4.5m/s .

[wojtar]

We have air to water exchanger 2 passes with extended fins,Due to poor MOC of tubes tube failure is frequent and about 20 tubes out of total 189 had been pluged.
As a result what will be the net loss of heat transfer & other changes in fluid dynmaics.Shell side v=2.5m/s and tube side is 4.5m/s .

It's hard to say anything basing on your short description. I think such exchanger should be recalulated again to see its capability. You have lost ~10% of heat transfer area but velocity in tubes has increased leading to higher heat transfer coefficient. The result is somewhere in between ...

[Zauberberg]

We have to assume that CW flows through the tubes and one of possible reasons for frequent failures could be excessive outlet temperature of cooling water (should not be more than 45 degC). The velocity is quite substantial as well, so it might be an erosion issue caused by precipitation of salts from cooling water.

Unfortunately there is so little data in your post and we would need a crystal ball to get the answer for you.

[Padmakar Katre]

Hello Ranga,
Unless you don't come with some specific inputs like the water quality and tube MOC it's really hard to comment on the issue. 10 % tubes plugged means reduction in the heat transfer area and incresed tube side velocity even with same flow. Now if the same flow is through tube side (water), the water outlet temperature is more than the design case which could cause to precipitate the salts as pointed out by Zauberbergand if the water flow is manipulated in order to control the process side(air) outlet temperature, then the tubes will observe increased water flow. As you stated earlier that the tubeside velocity is 4.5 m/s which is already higher, will subsequenctly go up leading to erosion and tube failure. Further inputs will help us to access the situation better. Hope to hear from you.