Instant water chillers - ammonia recirculation systems

[lraja]

Hi all

Falling film evaporators, usually operated in association with ammonia recirculation systems, claims to drop water temperature within 1 oF of freezing point of water (e.g. Instant chillier by Chester-Jensen). These instant chillers (evaporators) are made of short gas flow corrugated plate heat exchangers arranged in a series to obtain required surface area that correspond to the dT and flow rate of chill water required.

Could the experienced members point out the pros and cons of these instant chillers when used in applications for obtaining chill water (at about 33 oF) for process applications.

More importantly, in the case of dropping water temperature within very close limits to freezing I am wondering how ice build up on the plates, if any due to some reason or other, are avoided under all running conditions including steady full load or not so steady part load etc?

raja

[US Iceman]

If you are trying to chill water down to +/- 33F, then you should consider the use of a back pressure regulator to maintain a constant evaporating pressure within the plates & surge drum.

[bruceboldy]

I agree with Iceman on the regulator for suction control.

But if you want to have 33 degree instant water check out the Spray chiller designs on the market.
With the spray chiller (my old company was very good at these units) the suction pressure and a temp sensor can almost guarantee that you will never freeze up.

The spray design will totally wet the surface for high transfer rates but can be stopped instantanously so that even if the water begins to freeze it can be easily defrosted. The units can vary the flow rates if need be.
The tubes are totally wetted surfaces for high transfer but can be totally dry or void of liquid with the controller.
The flooded plate will still have a mass of liquid near the cold water surface, even if the reg is shut down.
.
The units are used for many applications, easy to set up and very reliable. Only have one moving part, a liquid pump.
Let me know if I can help you out on this

Bruce