Compressor suggestion?

[nathanpmonty]

Hi, We are trying to build the highest efficiency (highest COP) vapor compression cycle custom refrigeration unit possible. We use finite element heat transfer to design our custom evaporator and condenser, but I am not sure what refrigerant and compressor to use. Our evaporator temp will be about 7 to 8C (45F) with a 10C (50F) differential temperature between the evaporator and condenser. We would like to use water as the refrigerant because it is harmless. Additional cost for the compressor is not as important as high COP. This for an industrial vapor compression cycle application = 25 to 50 Tons.

Is there any new compressors on the market that might be more expensive but more efficient? Who manufacturers the best water vapor compressors?

[Brian_UK]

Hi, We are trying to build the highest efficiency (highest COP) vapor compression cycle custom refrigeration unit possible. We use finite element heat transfer to design our custom evaporator and condenser, but I am not sure what refrigerant and compressor to use. Our evaporator temp will be about 7 to 8C (45F) with a 10C (50F) differential temperature between the evaporator and condenser. We would like to use water as the refrigerant because it is harmless. Additional cost for the compressor is not as important as high COP. This for an industrial vapor compression cycle application = 25 to 50 Tons.

Is there any new compressors on the market that might be more expensive but more efficient? Who manufacturers the best water vapor compressors?

Which temperature scale are you using?
A 10°C differential means it is 18°F whereas a 50°F figure equates to 27.7°C.

[mad fridgie]

had a play with this one many years ago, water as a refrigerant (theory) is fantastic.
You need very high voulme and high compression ratios. The best best practical advice i can give you is to use an aircraft multistage turbine.
I would be very interested in how you go with tis project

[nathanpmonty]

Sorry about that a delta of 10C = a delta of 18F. 10C absolute = 50F absolute - sorry about that. It is a 10C swing which is a 18F swing from evap to cond.

[monkey spanners]

All refrigerants are harmless if they stay in the system

[nathanpmonty]

The Latent Heat is much higher so you need less specific volume with water. I think the technical problem is that the pressure of water at 5C for example is so low that the vapor density is too low and the intake pressure to the compressor is too low. A 1PSI the compressor has to process a lot of vapor because there is essentially no water in the vapor.

Any suggestions on the highest efficinecy compressor company? I read about Grasso. Are they the best or should I call someone else?

[michaelm]

had a play with this one many years ago, water as a refrigerant (theory) is fantastic.
You need very high voulme and high compression ratios. The best best practical advice i can give you is to use an aircraft multistage turbine.
I would be very interested in how you go with tis project

B”H

York International invested a few mils. to developed the compressor using aircraft turbine without positive outcome.

[desA]

Hi, We are trying to build the highest efficiency (highest COP) vapor compression cycle custom refrigeration unit possible. We use finite element heat transfer to design our custom evaporator and condenser, but I am not sure what refrigerant and compressor to use.

How were you able, then, to simulate 2-phase heat-transfer in your FEM model, if you did not have the refrigerant properties on hand?

I'd be interested in seeing which FEM software you use - it must be fairly advanced to manage boiling & condensation. To my knowledge, this aspect is still not well understood theoretically, unless you add in boundary condition empirical correlations.

I'd also say that you may have the cart-before-the-horse, so to speak. It is most often advisable to first select the refrigerant of choice, then the compressor, then balance the evap / cond duties around your design operating point...

[mad fridgie]

B”H

York International invested a few mils. to developed the compressor using aircraft turbine without positive outcome.

Did not know at what stage they were at, Jon Paul in Germany I believe. (prof or doctor)
Last I heard they needed to achive an additional 2% efficiency per stage to make this a winner.
They were using this to produce vacuum ice (very large vapor voulmes and compression ratios)
I wonder for this application it would more suitable?
If magnetic bearings were introduced, then frictional losses would just be reduced. how to achive the electrical and mechanical couple becomes the problem (deep vacuum) with out the loss of efficiency. (example canned rotor)

[nathanpmonty]

If you look at the COPs for a 10C (18F) TD there is very little difference in the performance of the refrigerants. The small Delta T (and corresponding delta P) leads to a small compression ratio which leads to a high COP. The actual refrigerant is not that important. We are just trying to keep water at ambient as we isothermally compress. Don't think about a normal refrigerator, ice maker, or A/C unit. The evaporator will be at 10C and the condenser will be at 20C.

Just seeing if there is anyway to do this more efficiently since it is not your normal A/C application.

mad fridgie is right - deep vacuum with water that compressors struggle with - not sure why, I am not a compressor design guy.

Any suggestions for a compressor company? I now have the names Grasso, Danfoss and Emerson/Copeland. Any others? Any suggestions?

[mad fridgie]

I think that you need to choose your refrigerant first.
I would widen your field, you are compressing a gas/vapor, no point looking at refrigeration only (off the top of my head can not think of any company gives standard data for these conditions) An oil free compressor would be good as this would reduce other issues.
Water in deep vacuum,comp struggles becaue of high compression ratios (comp ratio is based upon absolute pressure, not gauge pressure.)

[nathanpmonty]

Why chose a refrigerant without a compressor? Why not look at various refrigerants and various compressors and make a matrix to find the best combination for my operating conditions?

I can look at the enthalpy or entropy of various refrigerants and see which one provides the highest COP, but the answer would be water. But water is not appropriate because of the compressor does not pump vacuum well.

For example from 10C to 20C water's pressure difference is 0.16 psia and Ammonia's is 35.15 psia, so it is reasonable to think that the compressor for water would be smaller (the compression ratio is 58 times less). But compressors do not work well compressing at 1 to 3 psia, so water is ruled out but only by looking at the refrigerant and compressor in combination, not by picking one or other intially and potentially accepting the compromise of the other.

Any suggestions for a compressor company? I now have the names Grasso, Danfoss and Emerson/Copeland. Any others? Any suggestions?

[Gary]

Seems to me that the best pump to run in a vacuum would be a vacuum pump.

[mad fridgie]

Why chose a refrigerant without a compressor? Why not look at various refrigerants and various compressors and make a matrix to find the best combination for my operating conditions?

I can look at the enthalpy or entropy of various refrigerants and see which one provides the highest COP, but the answer would be water. But water is not appropriate because of the compressor does not pump vacuum well.

For example from 10C to 20C water's pressure difference is 0.16 psia and Ammonia's is 35.15 psia, so it is reasonable to think that the compressor for water would be smaller (the compression ratio is 58 times less). But compressors do not work well compressing at 1 to 3 psia, so water is ruled out but only by looking at the refrigerant and compressor in combination, not by picking one or other intially and potentially accepting the compromise of the other.

Any suggestions for a compressor company? I now have the names Grasso, Danfoss and Emerson/Copeland. Any others? Any suggestions?

I do not want to be rude, but if you do not understand the difference between compression ratio and pressure difference how are you going to design this system.

[nathanpmonty]

Sorry I was typing too fast because I had to run out the door for my kid.

[HallsEngineer]

J&E Halls, Mc Quay, Daikin we need to know size and turn down. Sabroe, Hitatchi, Mitsubishi. All good compressors.

[mianrizwan]

this is a intersting job

[almichieuk]

I suggest that you look at the Turbocor compressor, I would say that its one of the highest efficiency compressors on the market right now. The only problem with it it that its a centrifugal compressor so suffers with surge. but if you can work with that and design controls to suit it I would go with it.

It runs on magnetic bearings meaning zero friction internally. Starts on less than one amp. We are running equipment where the fans are pulling more on 200kw Cooling capacity...