Copper Stream:
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Copper Stream Volume 14
Zoom Up Copper:

The length of the copper tubes
used in the indoor unit of theseparate type air-con can be
2.2 times longer!

Room-type air-conditioners are now the integral part of Japanesehousing, rather than one of the home appliances and considered essential
for our living, therefore, every single room in our households is equippedwith a room air-con. It had been said the market would be saturated, yet,the number of shipping-out units steadily grows over 8 million per year
since 2010, and it reached over 9.4 million in 2013.
The challenge for the industry is now to deliver “Comfortableness andEnergy Saving” at the same time. It is copper tubes for refrigerant usedin the heat exchanger that address the issue. The more the copper tubes
are in the units, the greater the saving will be. So the manufacturers hadvarious efforts of their own to increase the volume of the copper tubes.
But the Japanese housing environment does not allow a large indoor unit,
then the space for copper tubes in it is quite limited. Somemanufacturers tried to increase the size of outdoor unit so that the larger
amount of copper tubes can be used, but again, the size of the balcony inthe apartment complexes where the outdoor unit is normally installed islimited. So everybody more or less gave up on the idea of increasing theamount of copper tubes.

But in 2015, Shizuoka Works, Living Environment Group, Mitsubishi
Electric Corp., developed an indoor unit with copper tubes about 2.2 times
longer than the conventional ones. Here is the story about how they
made the ‘impossible’ possible.

Shizuoka Works of Mitsubishi Electric Corp.
was established in ’54 to manufacture fridges
and HVAC equipment as well as to serve as
an R&D Center for those. About 1.2 million
air-cons are annually shipped out of thisplant, which is fully automated with the
cutting-edge technologies.

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The new structure that pushed the envelope of the concept of‘energy saving’ - this has set the next generation standard for thesplit-type air-consTotal length of the copper tube used 2.2 times greater.
Total energy saving 5.1 times improved.

(blue bar - existing) (yellow bar - new)Succeeded in making the total length of the copper tubes used greater!
Innovative to change the method that had been used for almost half acentury.
Mitsubishi Electric Corp. developed the wall-type room air-conditioner nearly 50years ago. They have branded the air-con as “Kirigamine”, and been so proudof the technologies used in their invention that had awed the industry; thetechnology is called “Line-flow fan”, or a cross-flow / tangential fan, thecompactness of which made the product very successful in the Japanese housing
environment.
Even 50 years after the launch, the line-flow fan still is the standard technologyof the room air-con in Japan. Yet, Mitsubishi have now come up with the newmodel of “Kirigamine” that would not use the line-flow fan. The reason of moving
away from the technology they have been so proud of, is that they concluded theywould need to use more copper tubes as the refrigerant container in the heatexchanger if they pursue for further energy saving. In that way, the heatexchange between the air and refrigerant can effectively occur. Up until 2000,
the effectiveness of heat exchange had continued to improve by making thecopper tube diameter smaller, from 7 mm to 5 mm, improvement of the motor
performance, or changing the shape of the fans, etc. But there had no room ofimprovement after that, therefore, they had to think of the innovative way to savethe energy, such as structure design change.
That is how the new propeller structured “Personal Twin Flow” system wasdeveloped. Like in the case for the line-flow fan, this “Personal Twin Flow” hasbeen used first in the world for the split-type room air-cons. In this new system,
new model of Kirigamine uses total 88.2m length of copper tubes, from 38.7m of
the previous model. Previous model has done only 2.6% of the annual energy
saving, and the new model can achieve about 13.3% or more than 5 times greaterthan the previous model.

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It is not just the replacement of the fans to propeller type, but involves
reengineering of every single part of the device.
Bold design change in the indoor unit for new Kirigamine - what is the biggest
difference / improvement?
The biggest difference is the position of the fan in the unit; previously the rollshaped fans were situated in the middle of the unit. When the fans rotate, theair from the copper tubes of the heat exchanger which surrounds the fans can besucked into the fan-side [fig.1]. Due to this design, the space allocated forcopper tubes are quite limited.
The new Kirigamine has the propeller structured fans are situated on the upper
part of the unit, and the air blows down on the copper tubes of the Heatexchanger[fig.2]. So, there can be more room for the heat exchanger, in theother words, more space for the copper tubes.
Needless to say, this structure change cannot be achieved only by replacing theconventional fans to propeller ones.
It requires the redesigning andreengineering the whole unit, such as to have the propeller fans compact enoughto fit into the space above the tubes, as well as having the heat exchanger shapedin the way to exchange the heat efficiently.
The outdoor unit also had to be redesigned to balance out the performances of
the heat exchangers for both units. After the numerous trials and errors, theycame up with the optimum design of the indoor unit.
For this renewal, the motor has been reengineered to enhance the performance,
which required the redesigning for every single part. Then, the total energy
saving has become the level of ‘miracle’.

The new heat exchanger has W-shaped to accommodate longer copper tubes.
Previous model - Line Flow Fans (fig.1)
Air sucked outside of HEX to blow on
the fans

New model - Personal Twin-Flow Fans(fig.2) Air flow generated by the fanspushed into the HEX, then blown down

(blown – Heat Exchanger)
Excellent
thermalconductivity,workability
andantimicrobial
property…many reasons for copper to be the standard material for therefrigerant tubes in air-cons.
Approximately 10K tons of copper are used every year for tube in indoor andoutdoor units of room-type air-cons in Shizuoka Works of Mitsubishi Electric.
Additionally, the plant here produces industrial packaged type air-cons which areused in the commercial buildings such as the offices and stores, as well as
refrigerators. Copper tubes are used for all of these products/
The main reason for keep using copper tubes is the high thermal conductivity.
Also its malleability is great to work on the tubes for room air-cons, because it
can be designed with sharp curbs to fit in the limited spaces. Engineers also
point out its corrosion resistant and antimicrobial properties, too. The air blown
into the room should not contain lots of germs and bacteria. Especially theJapanese condominiums today tend to have a joint kitchen-living room, so thetube should better be strong against both grease and dusts.
Apart from the use for the tubes, air-cons also use copper for its compressor andcoils of fan-motors. Continuous effort to improve its efficiency is being madehere, and various types of compressors need to be developed. The key for
improvement largely depends of the thickness of the copper wire: Its diameter
would range between 0.8 and 1.1mmφ, but in principal, the thicker the copper
wire is, the greater the energy saving is. Currently average thickness of the wire
diameter is 1.4 times larger than the one used in the past.

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vol.13-Page.4
Succeeded to deliver further comfort by this innovative design change.
Another reason to motivate the engineers at Mitsubishi Electric is the ‘pursuit for
the ultimate comfort’ for the users.
Kirigamine is equipped with a function called “Move-eye”, which is the sensor todetect the body temperature of each individual person in the room while analyzing
the room temperature - even under the same environment, some people would
feel chilly and some too warm. Personal Twin-flow system has 2 propeller-type
fans, so individual person in the room can get the most comfortable air flow for
their own need. Also, when the room temperature reaches to the level desired,cooling operation automatically changes to ventilation only. They name it as“Hybrid Operation” and can drastically improve energy saving rate.
At Shizuoka Works cite, there is a show-room where people can experience thenew Kirigamine’s cutting-edge technology. There are also displays of various
kinds of their products; room-type air-cons, packaged type air-cons for offices andstores, compressors, etc. Every display has detailed explanation and thevisitors can see how copper is used in those products as tubes and wires.
Some manufacturers are shifting from copper to other materials due to thematerial’s price volatility, but Mitsubishi people believe in copper. “When I thinkof corrosion, copper is the most reliable material and have no plan to move awayfrom copper for a while” says one of the engineers at Shizuoka Works.
Utilizing copper’s properties to deliver the comfortableness and energy saving,Kirigamine has been awarded with “Energy Saving Prize” by the Minister ofEconomy, Trade and Industry in 2015, which is considered in Japan the highest
prize for a commodity item. Also, Shizuoka Works of Mitsubishi was awarded
Energy Saving Grand-Prix by President of Energy Conservation Center.

Display at Shizuoka Works, Mitsubishi Electric - “Hybrid Kirigamine” with ‘moveeye’; how the sensor works and analyzes the individual body temperature andseparate ventilation system can be experienced; visitors can also learn thehistory of the product / brand. Inside of the units are exhibited in the cut-out
model so where the copper is used and how the material can improve theefficiency can be seen

The weight of copper tube is 25% ofoutdoor unit regarding industrial
package type air-con.

Copper wire and tube are used as
main parts in the compressor.