nalysis and performance evaluation of oil-free chiller
As the technology growth and the mind of environmental protection become more
important, the topic of reducing electricity for existing equipment has been raised for
a long time, with the assistance of different countries policies, the company with
different industrial background started to study on new method on performing same
functioning equipment. In Building services industry, the most energy consuming
area is the part of air-conditioning, it host around 70%of the whole site energy
consumption, that means if the energy consuming of air-conditioning can be
decrease, the reduction of energy consumption will have the largest cut off and
greatly impact the whole building energy profile and contribute to the society.
Nowadays, the hot topic of most efficient and less using of energy for the division of
air-conditioning is the oil free chiller technology, the idea of this technology was first
introduce in the late 20th century in Australia and start producing prototypes call
Turbocor, and the founder soon established the company name Smardt and the
company aim to maximise the benefit of these technologies in chiller performance,
and moving the whole production line to Montreal of Canada. In the early 21st
century, they part with Danfoss, and provide their skills and technology on oil free
compressor to continuously benefits the society.
In Hong Kong, the first oil free chiller was installed in Government House, and the
contractor, CHIVAS, was soon completed the Certificate Scheme for Quality Chiller
Servicing requirement published by Architectural Service Department, until now,
Hong Kong has already installed over 200 units of different types oil free chiller. And
this move also leading other chiller leaders to research in oil free or somehow
frictionless chiller compressor design and continue to leading other company to
benefits the society together.
In below, Ill expand the topics by different point of view,
1. Comparison of traditional chiller, VSD and DOL, and Oil free chiller
2. Basic principle of oil free chiller
3. Initial cost of oil free chiller installation
4. Installation method for oil free chiller
5. Running and operating cost of oil free chiller
6. Life cycle cost of oil free chiller in compare with traditional chiller (20 years)
7. Maintenance cost
8. Comparing different kind of oil free technology
Comparison of OFC and traditional chiller
As to evaluate the performance of OFC, we should talk about the traditional chiller
for furthermore discussion, and the chiller has split in to two major difference,
Variable speed drive (VSD) chiller and Direct on-line (DOL) chiller. The major different
in between each other is the starting method of the machine, which the DOL chiller
is to immediately provide the rated power of the machine, which is leading to the
waste of energy, like harmonic distortion in machine starting current, approximately
3 to 9 times of machine rated current, rapidly start/ stop of machine due to
unloading of the chiller in variable building occupancy, etc. For VSD chiller, the
working mechanism is to change the machine frequency in order to meet the usage
or requirement of different scenario, which can significantly decrease the energy
waste due to the issue bring out from DOL chiller to perform better energy managing
and more accurate in loading control.
Working principle of OFC
Before the comparison of the traditional chiller, the working principle of oil free
chiller should be introduced to make a concept on how it works for better
explanation on the different between traditional chiller and oil free chiller.
The compression method of the oil free chiller compressor is same with the oil
lubricated centrifugal chiller compressor, but the difference is just the oil lubricated
bearing is being replaced by , which will eliminate the
highest friction lost produced by mechanical moving parts, greatly reduced the
mechanical wearing and high maintenance oil systems, which will greatly saving
about 35%, and ensuring long-term reliability compare with conventional chiller.
The only movable parts of the oil free compressor, rotor shaft and impellers is be
levitated when the compressor is being start up and rotate by digital controlled
magnetic bearing system. Each magnetic bearing is monitored by position sensor
which can provide real time feedback signal to bearing control system, about 120
times per each revolution, which can ensure the constantly centered rotation.
And the variable speed drive is also merged into the oil free compressor to operate in
high part load efficiency, also the technology of inlet guide vane assembly help the
oil free compressor trims in low load capacity, and those component is digitally
integrated together to optimize energy efficiency and performance of the
compressor to the full range of operation and temperature of the oil free chiller.
The digital controller is also proactively managing compressor operation with real
time external and web control enabled to monitor its performance and information.
Its also using refrigerant, e.g. HFC-134a, to cool down the electronics and
electromagnetic component to maximise the efficiency and safety operation.
Also, due to the working principal, the sound level and vibration level is greatly
reduced and significantly decreased the expenses for attenuation.
And the major advantages of oil free chiller can be introduced, the greatly reduced
friction loss can up to 20% in compare with conventional
chiller, those 20% energy is routinely lost in rusting of conventional bearing in result
of clogging of heat transfer surfaces.
Also refer to ASHRAE study, project 751, typical oil lubricating chiller reduce in design
heat transfer efficiency of 15 to 25 %, as lubricating oil stack on heat transfer surface,
denature and prevented normal thermodynamic transfer process. In basic logic, no
oil means no contaminate, design efficiency is being maintained with effortless.
Initial cost of OFC
For initial cost of oil free chiller, mostly is expensive than conventional chiller, as the
component of the oil free chiller include lots of high-end electronics component due
to the accuracy of the needs on operating the chiller, its around 15 20 % higher
than other conventional chiller.
Installation method and installation cost
When we talk about the installation method, one of the biggest advantages of oil
free chiller is that the chiller component can be break down into so many parts,
instead of conventional chiller, which can only break down into four parts, condenser
tube, evaporator tube, control panel and compressor, which makes the
transportation cost greatly reduced, all the parts can be reassemble on-site to suit
different condition, the chiller can be assemble on-site and reconducting the testing
and commissioning process to achieve the operating condition.
When talk about installation cost, its very flexible due to the installation method can
be discuss but the cost is similar due to the installation method and the
transportation method can be balanced in different situation.
As the above mentioned before, due to the and the
frictionless design of the compressor, the energy usage is being reduced, and the
operating labour can be reduced due to the web enabled function can alert operator
which the compressor is being fault down and deploying technician to conduct
inspection on defected oil free compressor.
By the effortless maintenance, the cost is greatly reduced, and the maintenance
method is simplified due to the help of , the
maintenance can be done by using computer to check if there has any defect and
check the magnetic bearing if its in normal operation, some general cleaning and
rusting prevention is done on the surface of compressor, which means not much
works should be done and thus the maintenance cost is greatly reduced.
Life cycle cost
By the above-mentioned cost combined together and the defect rate is greatly
reduced due to the assist of high-end electronic component with real time
monitoring of operator, and the cost saving on billing due the oil free chiller working
principal, the life cycle cost comparing with conventional chiller is in the next level,
approximately reduced by 30%.
Comparison with other types of oil free technology
As different manufacturer will start studying on more energy efficient way, many
kinds of oil free technology has been introduce, like the ceramic bearing, and using
refrigerant to be the lubricating media introduced by Trane and Carrier, those
technology also reduce the friction in between the shaft and the bearing itself to
perform the functionality of oil free, but those technology is new and no one can
guarantee the life cycle and the long term operating data.
By above mentioned point, Ill gathering information from web as the oil free chiller
technology is not a new thing in our life, this technology has be introduce in late 20th
century and start to grow up in early 21th century, the first oil free chiller is being
installed in Hong Kong in around the year of 2012.
For the comparison of conventional chiller and oil free chiller, many researching
paper can be found on the internet which can be used and quote with suitable
reference, please see the reference list.
For working principle, we could find it in the pioneer of the oil free compressor, the
website has detailly explained the working principal of the oil free chiller which is
For the cost comparison it can be find in some sales notes that is available in the
internet which can provided for our further usage.
For comparing different types of oil free compressor, the information is also
available in the manufacturer website, which will be quoted also in the reference list.
As this literature should be supported by large amount of practical data, the primary
data will be taken from a real site which is in operation already and some data of
chiller replacement which has been conducted for the comparison of the data
different in conventional chiller and oil free chiller, the Hong Kong Science Park is an
example on chiller replacement from conventional centrifugal chiller to magnetic
bearing, Oil free, chiller which can be the primary data of this researching paper.
The 2nd primary data will be suitable for manufacturer provide report for verified if
the 1st primary data have the same behavior with the manufacturer said and can be
further analysis on the issue whenever is the same or not.
The analysis of those data is on different kind of data, like the building behavior,
cooling load difference, chiller water in/ out temperature, condensing water in/ out
temperature, pump operating nos. and running status, cooling tower fan nos. and
running status, chiller loading status, occupancy rate, etc. This information can make
a clear comparison on before and after chiller replacement. And its also reflected the
real situation of the different of conventional chiller and oil free chiller.
Shortlist of key literature source
F.W. Yu, K.T. Chan, R.K.Y. Sit, J. Yang (2015) Performance evaluation of oil-free chiller
for building energy performance improvement
T.K.Ng, oil free magnetic bearing chiller energy advantage
Scott Moorhouse, Edward Rodriguez, Drew Turner (2020) Variable Speed Oil-Free
Magnetic Bearing Centrifugal Compressors
Jackson L. Ball, saving energy with oil free magnetic bearing centrifugal chiller
SA Parker, J Blanchard (2012), Variable-speed oil-free centrifugal chiller with
magnetic bearing assessment George Howard, Jr. Federal Building and U.S.
Courthouse, Pine Bluff, Arkansas
Carrier (2016) 19DV Back-to-Back Centrifugal Liquid Chiller with PUREtectm
Refrigerant and Greenspeedtm Intelligence
Trane (2013), Engineers Newsletter volume 42-4, The impact of VSDs on Chiller Plant
Trane (2013), Trane newsletter volume 21, Trane Series S CenTraVac Chiller An
Industrial-grade Oil-free Solution
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