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Other than power consumption, is DX chiller always better than flooded ?
Actually, I am in the process of finalising the specification of few nos of R134A screw chillers of 150 - 200 TR for immediate purchase. Not able to decide DX or flooded. In the case of DX, water being in shell side, mechanical cleaning of shell side is not possible. Water quality is not that good.
Kindly advice
Hi Nirmalya:)Quote:
Originally Posted by Nirmalya
in the range you are talking about I would advise Flooded:)
Better initial performance and better future performance due to being able to clean it.
Kind Regards Andy:)
Hi Andy:)
Thanks a lot. It is matching with my views.
But, DX is having unique advantage in the area of oil. Why removable tube bundle is not recommended in evaporator so that shell side can be cleaned ? And also, utmost care to be taken for avoiding any water ingress.
Regards
Nirmalya http://www.refrigeration-engineer.co...cons/icon7.gif
I am mostly a NH3 person. However having been invoved with flooded and DX systems both, the Flooded System has always been far better than the DX. Far fewer things to go wrong. TX valves are to be avoided at all costs in a system of any size. NH3 expansion valves are more troublesome than others but the same problems are inherent with all TX valves.
The initial cost MAY be higher flooded, but the benefits and operating costs make up fot that.
Proper oil reurn of course is essential.
I once had R-22 flooded Spiral Freeze system without any means of oil return. However since the Screw only lost about a Gallon a month or less. Once a month we would pump it out and drain the oil. No problem at all.
I prefer the flooded systems also. As long as you have some type of oil recovery system on the flooded evaporator I believe you can expect better results.
One thing to be aware of on flooded units is during start-up with hot systems. If the compressor is allowed to fully load in a hot start up condition, you might get a small amount of liquid back to the compressor. Unless the accumulator is sufficiently large of course.
Hi Iceman and NH3LVRn,
Thanks for shareing the experience.
At present, I am involved in operation of R11, flooded, centrifugal chiller. I would like to share some experience.
Waiting for rersponse
Hi Niramalya,
Flooded chiller is always better due to reasons listed below :
a) efficiency is better
b) since you will use R134a, oil can be recovered better in o/s
c) Since u have water quality problem
d) need to have precise thermostats to avoid water freezing in tubes
D.D.KORANNE
Hi Koranne,
Thanks for your valued opinion.
I would like to seek advice in one area - how to clean shell side of the chiller ?
Nirmalya
If the shell-side of the exchanger is the liquid being cooled and it is fouled, you have a major problem.
You can circulate a chemical to try to clean the tube bundle and baffles, but this may not produce very desirable results.
I've had to try this before because a client insisted it could be done! Debris will collect at the baffles and is very hard to remove, unless it can be dissolved by a chemical.
The tubes may clean up better, but the end result is at best questionable.
The only good way to clean this, is if the tube bundle can be removed. Unless the bundle is designed to be removable, you are facing a terrible project.
If the system application has to work with "dirty fluids" the fluid should be placed on the tube-side by using a flooded chiller design, or a removable tube bundle with a DX liquid feed. Filters/strainers are what I would consider a secondary consideration in this respect.
Hi,
I suggest flooded type shell&tube with water in tubes covered with removable covers for cleaning. Of course with some additional...
When your water temp start to rise you know ....it is time for cleaning ;)Quote:
Originally Posted by US Iceman
Best regards, Josip :)
Hi Iceman and Josip,
Thanks for your valued opinion and advice.
In the instant case, water being cooled is in tube side.
R11 is in shell side. It appears there is heavy sludge formation in shell side for number of reason. Just cleaning by R11 has not been successful. I am trying with TC ( Tricholoro Ethylyne ). Lot of mucks have come out. I will share the result and experience.
Any further advice ?
Regards
Nirmalya