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Updated: August 1, 2013 15:00 IST

A -200° C refrigerator developed

R. PRASAD
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The department of Mechanical Engineering, IIT Madras, has developed refrigerators that works at very low temperatures. Picture shows one that works at -100 degree C.
Special Arrangement The department of Mechanical Engineering, IIT Madras, has developed refrigerators that works at very low temperatures. Picture shows one that works at -100 degree C.

IIT Madras operated the system non-stop at about -200 degree C for three months

IIT Madras has achieved temperature as low as -200 degree C by using a single stage vapour compression refrigerator using a compressor that is routinely used in domestic refrigerators and air-conditioners. The working pressure of the compressor is nearly the same as in air conditioners. “The system was operated non-stop at about -200 degree C for three months,” said Prof. G. Venkatarathnam, Refrigeration and Airconditioning Laboratory, Department of Mechanical Engineering. His team has developed many other prototypes too.

It is indeed possible to achieve temperatures as low as -110 degree C by using a conventional cascade refrigeration system. In this, three refrigerators are arranged in a series and together help in bringing down the temperature in steps. “The disadvantage is that one compressor and a few heat exchangers are required for each stage. So the circuit becomes more complex and hence more expensive,” he explained. “And it is difficult to achieve temperatures lower than -100 degree C.”

A conventional refrigeration system uses a single liquid coolant that absorbs heat and becomes vapour at a constant temperature. “Our technology uses a mixture of coolants where the conversion of liquid to vapour occurs over a range of temperatures — 100 degree C or more,” Prof. Venkatarathnam said. “All this happens in an internal heat exchanger.”

Similarly, unlike the conventional system where the heat exchanger predominantly works at one temperature, the heat exchangers used by the IIT Madras team can work at very large temperature difference of 200 degree C. Only such a heat exchanger can handle the mixture of coolants that get converted from a liquid to a vapour state over a range of temperatures.

The significance of his achievement becomes clear when the huge gap — from -110 degree C to -196 degree C — that exists between the vapour compression refrigeration system and those that use liquid nitrogen is considered. “For many applications we don’t need -196 degree C,” he said.

There are several applications where his system can be used. For instance, food preservation, preservation of biological tissues, long-term preservation of blood, in semiconductor industry to improve the vacuum levels, and finally, cooling of electronics — including telescopes and infrared sensors.

According to him, his system works based on four critical factors — thermodynamic process, the choice of coolant and concentration of each fluid in the coolant mixture, heat exchangers, and oil management.

Getting the right mixture of the coolants proved to be the biggest challenge. There are four to seven fluids mixed together in the coolant. “We pick and choose the fluids and their concentration from about 25 to 30 possible refrigerants to arrive at the right composition,” Prof. Venkatarathnam explained.

Oil management is also equally important and is quite challenging. Since the freezing temperature of oil used must be lower than the operating temperature, there is a compulsion to reduce or almost eliminate any trace of oil circulating in the system. Home refrigerators use oil that has a freezing temperature of just -50 degree C. The IIT team uses three approaches to prevent oil from circulating. One of the methods helps in removing oil “almost 100 per cent.” Another can decrease the freezing point of oil to -120 degree C.

“Our principles have been extended to develop a novel low cost nitrogen liquefier that can be used in veterinary hospitals for storing bull semen, in many scientific establishments and small industries that use liquid nitrogen to improve tool life,” said Prof. Venkatarathnam.

Being a mechanical engineer,i can understand how difficult it may be to
produce such a low temperature, so it is my heartiest congratulation to
all who contributed to it.thanks Prof. Venkatarathnam ,thanks IIT
Madras,thanks all other members who were part of this innovative team
for such a huge contribution to Indian Technology.

from:  NIRAJ SINHA
Posted on: Aug 3, 2013 at 19:27 IST

Hearty congratulations to Prof. Venkatarathnam and the team!

from:  RAJ SINGH
Posted on: Aug 2, 2013 at 22:57 IST

Congratulations for such a novel invovation Prof.Venkatarathnam. Wishing you many more inventions to be fruitfull towards society as a whole. Perhaps, having a technology to collect the waste from moving train will be more appreciated,as one could imagine the state of hygeinic conditions prevailing and it's quite appalling to see that involving fellow human being solely for cleaning purposes. We need more of collaborative research been undertaking between public & private institutions (industries). For example, consider NASA, most of the technologies whch they use in the orbit was developed by private sector, offcourse it's been conducted in a transparent manner, and also has common use in day to day life. I'm trying to find a weblink of IIT-M,which has contributed so far in terms of technology for common public, which will certainly encourage more budding kids to get involved research and development field. Dreaming one day we'll have the technology, say 2020!

from:  Easwaran
Posted on: Aug 2, 2013 at 19:48 IST

I hope it will be avaible in the market very soon.........
Congratulations to the team.

from:  Revathi
Posted on: Aug 2, 2013 at 11:34 IST

Congratulations to all the members!!
Way to go IITians!!
Hip Hip Hurray!!

from:  Pradeep Verma
Posted on: Aug 2, 2013 at 11:31 IST

Hearty congratulations to Prof. Venkatarathnam and the team! Having experience in the fishing industry which uses blast freeze, I can right away find usefulness in this research. The team should go ahead and patent it and try to implement in the refrigeration industry.
In India, we rarely we find educational institutions with an appetite for research with only the IITs and a hand full of others as exceptions. It would be great if the government establishes a way in which research is promoted or make it mandatory for institutes to contribute towards research as compared to what are now institutes/(deemed)universities whose ratings are solely based on 'job fair' after education.

from:  Fisher Fernando
Posted on: Aug 2, 2013 at 11:25 IST

Congratulations to you Prof. Sir and your Team.
Indeed a great milestone achieved. This will be welcomed in
industry for its wider application in various front including in
transportation of Natural gas in liquefied form to remote locations.

from:  S Panneer Selvam
Posted on: Aug 2, 2013 at 10:30 IST

The proof of the pudding is in the eating. I have a nephew who went to
an better known Engineering College in the North. He and his classmates
decided to "build" a "formula" racing car. It turns out they paid a
private engineer for doing so and entered then went all the way to the
UK to enter the design in a competition. The usefulness of this fridge
will be proved only when a working model is built that is popular in the
market

from:  Nripinder
Posted on: Aug 1, 2013 at 15:03 IST

Very refreshing to see articles such as these that embark on scientific innovation and technology advancement. Now a days most of news cover merely political mudslinging, entertainment gibberish and frivolous matters. The real strength and future of a society will its technological advancement and India needs to do a lot of catching up.

from:  Poovhenden
Posted on: Aug 1, 2013 at 14:21 IST

Congratulations Prof Sir !
At last, some of your excellent work in low temp refrigeration and use of refrigerant mixtures is getting public recognition.

from:  Ajay Disley
Posted on: Aug 1, 2013 at 14:19 IST

I am glad to see the news. I am really proud of being a student of my
Respected Prof. G. Venkatarathnam. We are delighted for his immense
contribution, knowledge and tireless guidance that he offer to his
students. I am happy to see my lab getting quoted in The Hindu. Thank
you Sir for guiding us in the field of Cryogenic Technology.
-N. Lakshmi Narasimhan

from:  Narasimhan
Posted on: Aug 1, 2013 at 12:55 IST

Congratulations to the Team.

from:  Satya
Posted on: Aug 1, 2013 at 12:50 IST

Dr Venkatarathnam,
Congrats for yr achievement
I am a cryogenics engineer and so I am elated at yr success
Keep it up May god bless you

from:  S.Bala
Posted on: Aug 1, 2013 at 04:36 IST
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