Steam Fed Heat Exchanger 2

[TES59]

I have a steam fed heat exchanger that is used to heat a gas. Heat exchanger is pipe within a pipe with counter flow. Inner pipe which has fins carries the saturated steam. Outer pipe (shell) has natural gas that is heated before taking a pressure cut. I want to know how to determine (by calculation) if the steam can be replaced by hot water/glycol in this same exchanger and get the same shell side effect.

 

[Montemayor]

What you need to do has a name. It's called Rating an exchanger. You calculate what the fluids you are proposing will do when they are applied to the stated double pipe exchanger.

Your internal fins exposed to liquid on the "tube" side of this exchanger will lend little or probably nothing to the heat transfer taking place.

This type of exchanger is not only one of the cheapest made, but it is also limited to relatively very small sizes. It would not surprise me to discover that it is far cheaper to buy a new, custom-specified exchanger for the new service than try to modify this old one.

 

[25362]

Not that I can add to what Montemayor has said but it's not clear to me whether the fins are internal or external to the inner pipe.

 

[TES59]

The fins are on the outside of the inner pipe. Present case is that saturated steam (250 F) flows inside the inner pipe and the natural gas, which is being heated, flows on the outside of the inner pipe and is exposed to the fins. I'm simply, if it's possible, trying to find a way to calculate what the affect is if the steam is replaced by hot water/glycol (180 F and flow rate?)and how much natural gas can still be heated to the same 120 F temperature it is now being heated to.