Performance evaluation of an oil free chiller

nalysis and performance evaluation of oil-free chiller

Introduction

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.

Objective

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

Literature review

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.

Running cost

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.

Maintenance cost

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.

Methodology

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

useful.

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

https://coolingbestpractices.com/technology/chillers/saving-energy-oil-free-

magnetic-bearing-centrifugal-chillers

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

Performance

Trane (2013), Trane newsletter volume 21, Trane Series S CenTraVac Chiller An

Industrial-grade Oil-free Solution