Absorption Chiller VS Mech. Chiller

Hi everybody,
I'm an Intern for process engineering and had never worked with refrigeration divisions before.
On my research for chillers I found this nice forum and thought I can ask you guys some questions about my problem...
The company I work for have right now an old (16 years) mechanical chiller ( Frick RWB2) . The chiller is working fine but the maintenance costs and operation costs are a litle bit high (100.000 $/year):rolleyes:.
My questions is now is an absorption chiller way better than this unit we got right now? Would there be a lot of savings potential with a new absorption chiller?
The chiller is running 24/7 and we just need about 100ton/hr of refrigerant.
Steam with 150psig is at the plant side available.

Thx

Kind Regards
Leo

No, Absorption chiller is in no way better or more efficient than reciprocating. It only is useful when you happen to have lots of heat or steam that would otherwise need to be dissipated.
In this case, heat can be used for activating the absoption cycle and later wasted. In any other case, mech cooling is more efficient.
The best saving would just be to update that old chiller to a more modern and power efficient one.

I thought there is more saving potential with an absorption chiller, good to know that its not.

Thx

Quote:

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Originally Posted by Intern

I thought there is more saving potential with an absorption chiller, good to know that its not.

Thx

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NoNickName is right! Typical COP for absorption is 1:1 while for mechanical is 3:1 (get 3 watts cool per watt of work).

Absorption is good only if you have enough free heat at the correct temperature, then you get almost free cooling.

Hi Leo
Under certan conditions there is more savings potential with absorption chillers. For a start the plant has to be enough and there needs to be a source of waste heat like a co-gen plant. Or with new tecnologies like the solar heat tubes being used for domestic and commercial heating. I was on a new building last week where the 16 story roof was covered in hundreds of solar heat tubes. Massy University Palmerstonnorth NZ used to run a course design and sizing commercial industrial plants including absorption chillers, professors Clevland and Dr White were the guys running the course.

Further
You could invite 3 chiller companies to quote replacement of absorption and thier reccomendations on chiller type, additionally ask for chiller cop's and system cop's and annual running costs. Then add them up with life cycle costs including maintenance cost. Check out the Danfos turbo cor chiller for application.

Is the steam, waste steam or are you generating it for your processes? Is it a constant 100 ton load or does it vary?

If you have to generate steam to run the absorber then you should look at the cost to produce the steam to run the chiller versus the electricity cost to operate the mechanical version.

If the steam is waste steam and available in sufficient quantities that might benefit you.

Hi,
we dont generate the steam, we purchase it from another plant next door. The steam is available in sufficient quantities.
The load of 100 ton doesnt vary.

The chiller unit consume the most energy in our plant thats the reason for my research.

Thx for your answers

Leo

Hi Guys,
we will have on tuesday somebody from the chiller comp. York come to our company and give us information about mech. and absorption chiller.
I want to be prepared for this meeting, so I ask you guys, if you can give me some points (infos, links) that I should know when this guy is here.

Thx
Leo

Hello Intern,

As i look at your costs for operation and maintenance, how can you devide them.
I'm curious where these costs come from?
Is it regular maintenance or is it because of system / compressor failure?

Greetings.

Quote:

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Originally Posted by Intern

Hi Guys,
we will have on tuesday somebody from the chiller comp. York come to our company and give us information about mech. and absorption chiller.
I want to be prepared for this meeting, so I ask you guys, if you can give me some points (infos, links) that I should know when this guy is here.

Thx
Leo

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I would point to the door if any York rep walked in :-(

Multisync
London

I would second that. without libeling my self, York locally dont know a hell of a lot about the YIA's they are selling. Just a question though, what are you using the steam for, is there any scope for using the condensate line for heat recovery, and thereby utilising heat that is normally lost or sent back for re- use next door where the steam is generated?Alternatively, the plant next door may have the ability to provide lower grade heat in large quantities to run your chiller vis a vis a PHE, again on the condensate line, steam plants generally as a rule have plenty of scope for utilising heat at different qualities as a function of heir operation. I can give you a few pointers if you wish, also, the running cost of your frick seems high, you should have the overall set up checked for efficiency, and perhaps recommissioning to ensure efficient running. Let me know if you need any further info or have any questions.

By the way, the guys are right, efficiency of Abbos is very low, it is very old technology, not a runner unless you have waste heat.

Have you looked at your chillers loading trend, i.e. is it fully loaded all the time? if not and it is partially loaded there may be some scope for reductions in power consumption there, with a little know how and some capex.

down to about 42 dF LWT, you can use a commerical Lithium-Bromide absorber. Below that you will need a custom designed aqua ammonia absorption unit. Th LI-BR will cost more to run and generally less efficient than a good mechanical unit, plus requiring more floor space.

An Aqua Ammonia system will cost 5 to 8 times a mechanical system and is less efficient and much more plot area.

Ken

work out the cost per KW of steam. C O P 1:1 against Mechanical 3:1 Maintenance is much cheaper (only two small pumps) BUT absorbtion is much more interesting!!!!!!

vapor absorption machine(VAM) uses heat energy heat source can be steam fired, direct fired(diesel, LPG/LNG, LSHS, Kerosene).
But it is predominantly used where heat energy is used for process like Paper mill, Cogen power plant where steam is available.Otherwise VAM is not economical where the heat source has to be produced and needs higher capacity cooling tower and water quality as the heat rejection factor is 1.8 as against 1.24 for mechanical refrigeartion.

What temps do you want? If you want big efficiency go with ammonia water chiller 4 to 1 cop min, Or go with new smaller centrif system for around 6 - 1 cop for a/c

Disclaimer: Like OP I am not a refrigeration professional.

I have been looking at absorption chillers(Yazaki) as well. Setting aside efficiency for a moment, it seems to me that absorption chillers would have less maintenance due to fewer moving parts than compressor driven chillers? I know this is simplistic, but is there any truth to my reasoning? Also, what type of maintenance (recharging Li?) and life can one expect from an absorption chiller?

Many have mentioned that absorption chillers are not economically viable unless you have waste heat to use an an energy source. I have been looking at a solar thermal application and my reasoning is this: I would have a large array of solar thermal collectors already in place for solar thermal heating during winter. Thus, my heat source is very low cost. During summer months, the majority of the load (commercial application) is during the middle of the day when peak electrical rates are their highest and the solar energy is most abundant. Any comments are appreciated.

savman

With low quality heat as from solar collectors, the COP is even lower than with steam. The hotter the heat source, the more efficient the absorber.

As for maintenance, it is still there. You have semihermetic pumps that can fail, you have to keep the system tight as it operates in a vacuum and you have to maintain the chemical balance to prevent corrosion from the inside.

They are not happy with fast load or tower water changes and can crystallize. The newer units have much better controls and are not as prone to crystallization issues.

Ken

Maintenance for moving parts are less but the heat rejection factor is more i.e 1.8 as against the heatrejcetion factor for water cooled compression system is 1.24.
Thus the cooling tower capacity is high consequently water quality and water requirement are high. As the temperature handled is high scaling is also faster.
another important factor operation of purge (vacuum Pomp) very boften and oil need to be chnaged frequently in vacuum pump.
With all this VAM is useful when you have steam or heat source is available at lower cost it is used extensively.
Almost all Paper mills & Sugar mills use the VAM for refrigeration

Thanks for the replies guys. I most likely will have to find another use for excess heat produced in summer months.

savman