NH3-water PHE chiller

[pradyumna]

hi all ,

i have recently come across the following case:

one PHE chiller of 133 TR ( ammonia to water ) was installed for getting the water chilled from 10 to 2 DEg C at the flow of 50 CMH and the chiller was meant for the wort cooling in the brewery some 1 and half years back.

now

the brewery wants me to convert the same PHE to generate the chilled water from 32 DEG C to 2 DEG C by reducing the flow rate proportionatly to above design parameters. ( the munufacturer of PHE 'alfa laval ' is saying it should work with changed parameters

but i am doubtful

so looking some comments from here ( and of course its appreciated )

and if more information is needed then let me know please

have a nice time

:)

pradyumna

[frank]

Hi Pradyumna

From your figures (sorry but I have to convert them in SI units,)The chiller rated at 133 tons or 465kw with a flow rate of 50CMH or 13.89kg/s gives a delta t of 8deg C which is spot on for your figures. Since Q = M x c x dt.

If you want to increase the delta t to 30 then you must reduce your mass water flow rate from 13.89kg/s to 3.7kg/s.

This is a large decrease that I hope your systems can accomodate.

Frank

[Andy]

Hi,:)
the plate will probably do that td but Iam guessing the fridge plant won't and even if you wer to go with the big td the plant would be about as ineffecient as you could conceive.
Look at the flow rate at these conditions, you are getting next to nothing in process flow, about useless I would say.
Would be better to add in another cooling sourse to buffer the water down to nearer design, probaby to high for deep water well cooling, you could find out what temp bore well water would come out of the ground at, here in the uk you could manage 12 deg c water.
Another option would be to add plates to you system and run your plant at a higher evaporation (provided you condenser is big enough) gradually bringing the temperature down in say a very large buffer tank.

Hope this helps Regards. Andy.

[david.findlay]

When you say water chiller I hope you mean Glycol @ 2 Deg C!:confused:

[Andy]

Hi, David:)
nope I mean water, a plate heat ex will acheive these temps if sized correctly. We would use a Low Pressure Receiver on such a package. Alternativly a High Flux Chiller will acheive these temps, the on shown in the attached Sabroe Recip post is working at a water leaving temp of 2.5 deg C.

Your right glycol or some other antifreeze solution would be better, but costly to maintain in a large system. hence the use of water.
Regards. Andy.

[maxim971]

What is the surface of this Alfa-Laval heat-exchanger?