×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Mag Lev Chiller Part Load Efficiency

Mag Lev Chiller Part Load Efficiency

Mag Lev Chiller Part Load Efficiency

(OP)
Lately I have seen quite a big deal made about the magnetic levitation chillers and there excellent part load capability. I am wondering if anyone can explain how they generate such efficiency at part load.

As I am sure everyone is familiar with by now, a high pressure centrifugal with a VFD and standard oil lubricated bearing (1 compressor per chiller) is usually in the range of .55 KW/ton and around .375 KW/ton at part load with some condenser water relief to 65F. Going down past there chillers tend to be inefficient and increase in KW/Ton. I have always attributed this to closing of inlet guide vanes as the load decreases without the ability to further reduce VFD speed.

Mag lev compressors seem to pretty much level off at part load and can maintain as low as .32 KW/ton. I assume in comparison, to an oil bearing electric chiller is that the bearing friction power becomes a greater percentage of the total power.

Multistack in particular has a chiller with 2 compressors on it that can run at below .3 KW / ton from 50% load down.

Does anyone have any experience with these chillers or can explain why they would operate so much more efficiently when operating at low load? Any insight is appreciated.



RE: Mag Lev Chiller Part Load Efficiency

I'd assume Multistack is only running one of the two compressors below 50% rated load, which is then back up near its sweet spot efficiency-wise. To be a fair comparison, you have to compare to other multi-compressor units of similar capacity.

RE: Mag Lev Chiller Part Load Efficiency

To properly compare the efficiency you have to compare centrifugal oil and mag bearing at the same operating point. We must consider that the mag bearing is capable of a much lower turndown than oil lubricated. Simply because the mag bearing is not constrained by oil starvation. Inherently the mag bearing chiller IPLV kW/ton will be less. At the same operating point mag bearing will require less power as stated because of the no friction losses, and also important to consider the improved heat transfer from being oil-less.

RE: Mag Lev Chiller Part Load Efficiency

I think mcoul098 hit the answer to the question.

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources