I recently visited a site where a competitor is installing a new NH3 freezing plant, it's going to be a beautiful plant, and I could see that a considerable amount of time had gone into planning the component placement and the pipe work and I can say that this is a system the plant owner is going to be very happy with.

I didn't take any pictures since the place was crawling with electricians and I didn't want any "oooh, your competitor was here, taking pictures of everything" when the supervisor came by.

As I was leaving, I met the supervisor and we ended up talking about the system for 30 minutes

I mentioned to him that I noticed something with the economizer vessel and how it was connected to the rest of the system and how it was different from how I would have connected it.

He said that this way was how they always connected it, and I didn't want to push the issue since we are competitors and that the place was crawling with electricians and to be honest, I wasn't sure if it would really matter for the efficiency of the economizer.


This is how it was connected:

eco.jpg

This is how I would have connected it:

eco2.jpg

Theoretical plant data (taken from thin air )

Condenser pressure: 20 - 25 C (70 - 77F)
Economizer pressure: -20 - -25C (-4 - - 7F)
Liquid sep. pressure: -38 C (-37F)

Temperature of liquid leaving the economizer: -20 C (-4F) (it's very efficient )


Arguments:

-My way:

Counterflow, warm liquid from the condenser enter the coil at the top of the liquid level in the vessel and gets cooled down as it travels downwards, which I think makes for a more stable level and less surging in the vessel.

My way injects "warm" liquid from the receiver to the economizer, all the diagrams I have seen does it this way, would this decrease the efficiency of the economizer by injecting 20C liquid and causing an effect more like an LRI?


Their way:

Same way flow, warm liquid enters the bottom of the coil where the liquid outside the coil will be marginally colder than the liquid outside the coil at the top. In my mind this will cause a lot of boiling in the liquid and as the liquid inside the coil is traveling upwards it will be followed by gas bubbles in the liquid outside the coil, and this in my mind will mean less and less contact between the coil and the liquid outside that is supposed to sub-cool the liquid inside.

Their way injects sub-cooled liquid into the economizer, again, in my mind, maybe this counteracts the excess boiling.


Conclusion?

Is either way better than the other?

Would a combination of both ways make for a more efficient econimizer?

My way with counterflow and their way with injecting sub-cooled liquid?


What do you guys think?