Condenser Tubing 1

If you use a tube of the same wall thickness as previously installed, the difference in the heat transfer will be in the tube wall conduction. Values for the calculation of overall heat transfer coefficient and the necessary conduction coefficients should be available in any heat transfer text. Should you require a specific reference, I would be more than happy to provide one.

You can use the method in the HEI Standard for Steam Surface Condensers.
This will let you correct for the change in flow (you need the pump curves) and then estimate the new heat transfer values. We do this for customers all of the time.
Don't try to go back to heat transfer fundamentals, you will not be able to model what is happening in a real condenser.

You didn't say but I presume that they have have bronze tube sheets.
Is this water VERY clean? If not then 304 will not stand up. The tubes in the air removal section may have survived because the rest of the condenser is providing galvanic protection.
You should consider coating the tube sheets to suppress dealloying of them. A high build, 100% solid epoxy system is typically used for this (Plasticor is the very best).

Typically the limit for tube wall when moving from a Cu alloy to a SS is based on vibration. considering the differences in modulus 0.028"aw SS tubes will be stiffer than 0.049"aw brass tubes. It is a safe move that has been done in hundreds of condensers.

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P.E. Metallurgy, Plymouth Tube

As lways, EdStainless gives solid advice..... I assume that this is the first major retubing that you have been involved with

The tube change that you desire has been done on steam surface condensers many times. You may want to try to contact another power plant owner who has made these changes for advice

As stated above, there are also some major decisions (expensive) to be made about the tubesheet surface.

You should benchmark the flow and pressure drop, both before and after the retube.

BEWARE OF CHLORIDES ! You should purchase the few available books about condenser design on AMAZON and try to get some of the fine EPRI guidelines published regarding condenser repair.

Purchase the HEI standard also....

MJCronin
Sr. Process Engineer

Wow,

Thanks to you all for your responses. We are not new to this business and actually re-tubed this identical unit in 1997 and many more since 1980. This unit, like almost all of the condensers and HEX we have re-tubed have following OEM designs. This change is something new here in Alaska. I am familiar with almost every Boiler system and HEX here and none have done this retrofit yet. I appreciate the cautions and will proceed accordingly.

While it try to stay away from comments like this, there really are only two re-tubers in the US, RETUBECO and The Atlantic Group (now part of Day and Zimmer).
Hire one of them. They are both technically competent and excellent project managers.

But to MJCs comment, if your chlorides ever go above 100ppm or there is any risk of any biofouling 304 will not survive. Trust me on this.

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P.E. Metallurgy, Plymouth Tube

I should add that there are a lot of reasons to switch from Cu to SS.
1. You eliminate cooling water side erosion risk
2. you become fully resistant to sulfides (and H2S) in the cooling water
3. the steam side will be fully resistant to ammonia attack and grooving
4. Significantly greater steam impingement erosion resistance
5. No Cu in you cycle water (or cooling water for that matter) (as long as your feedwater heaters are also steel or SS)
Once your cycle side is all ferrous then you can move to Oxygenated treatment systems for boiler corrosion control.

Welcome to the modern world.
Feel free to ask me any condenser tube questions that you have.

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P.E. Metallurgy, Plymouth Tube

My only comment is that SS is not the cure all, especially when MIC is a real possibility with cleaner rivers, canals and lakes. We had several large SS condensers that we had to replace with Seacure because of MIC concerns.

Well, that is just moving to a better stainless grade. With over 50 common SS alloys there are a lot to choose from, though only about 5 different alloys are used in condenser service.
SeaCure is a superferritic that was designed for use in seawater cooling applications.
However as metengr points out MIC in fresh water is often a very serious issue. This has destroyed dozens of 304 and 316 condensers over the years, along with Mn related pitting.

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P.E. Metallurgy, Plymouth Tube