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ROCKY123
12-08-2015, 02:18 PM
Hi Everyone,
I have a system with pumped ammonia with over feed of 3:1 .The client would like to include one falling film chiller of gravity feed type. Do I need a surge drum for this? any other recommendations?.....temp=-30

RANGER1
12-08-2015, 09:05 PM
Hi Everyone,
I have a system with pumped ammonia with over feed of 3:1 .The client would like to include one falling film chiller of gravity feed type. Do I need a surge drum for this? any other recommendations?.....temp=-30

Rocky with the limited information you give I suspect if it was installed on liquid over feed set up, that evaporator pipe circuiting would have to be modified.
Surge drum could be used with pumped liquid to maintain level.
All depends what pipework is nearby, pumped liquid, high pressure liquid from liquid receiver etc.

Hot gas defrost also has to be considered for both, obviously surge drum more expensive to apply.

ROCKY123
13-08-2015, 01:55 PM
Hi Ranger,
The system is an ammonia pumped with evap temp of -40,-30 and -10. There is an evaporator In the -10 circuit which is 40kW. Client now wants to replace it with a falling film chller of same capacity which is gravity feed but the circuit available is overfeed with 3:1 . Can I install it directly to the circuit or do I need a knockout drum?

sterl
17-08-2015, 09:07 PM
Trouble is: your 40 KW chiller is only near that load when the water is at its warmest. If you have anything in terms of vertical pipe on the vapor side and the load reduces, your chiller is no generating refrigerant vapor and the liquid keeps coming at it. You will end up with a chiller and pipe riser full of liquid; and the liquid delivery side of each plate will collect a lump of hard ice due to the low incoming temperature....Additionally: If you connect it direct and overfeed you will have plates that cool well and plates that don't cool at all because if it was intended for gravity feed it will not have any restrictors to cause the flow to distribute from plate to plate.

You need a gravity vessel to feed it because thats how it was intended to be fed. What is left to figure out, is how to get liquid delivered to the drum. Has the Minus 10 got lots of net pump pressure?

ROCKY123
18-08-2015, 05:45 PM
Not much ...Because i am replacing an evaporator with this falling film chiller and the pump is selected for the existing system which is running 100%