Kobe Symposium 2014: R&D efforts leading to improved performance of CO2 components and systems

By Klara Skačanová, Dec 05, 2014, 16:02 3 minute reading

At the 2014 Kobe Symposium in Japan leading companies and organisations presented their research in HVAC&R related technologies. Panasonic demonstrated 25% energy efficiency savings of CO2 refrigeration system and improved CO2 scroll compressor for Eco Cute. NEDO in collaboration with Daikin presented about a 2011-2015 project developing a CO2 multi AC system and Hitachi showed how to improve efficiency of CO2 scroll compressor up to 5% by changing

The International Symposium on New Refrigerants and Environmental Technology 2014 (Kobe Symposium), organised by the Japan Refrigeration and Air Conditioning Industry Association (JRAIA), took place on 20 and 21 October 2014 in Kobe, Japan. 489 attendees (includes 71 from abroad) attended to learn about the latest HVAC&R industry advancements from 38 presenters. R744.com was on the ground to report on new CO2 technology. In this second article we summarise papers from Panasonic, Hitachi and Daikin.

Development of non-freon refrigeration system using CO2 Refrigerant, Takashi Inoue, Panasonic Corporation

Takashi Inoue of Panasonic Corporation presented about development of CO2 system with 2-stage split type compressor and results of demonstration evaluation from 6 stores. In conclusion, Inoue stated that at freezer temperature range the CO2 unit proved to be on average 25.4% more efficient throughout the year than conventional inverter type R404A system. The data sample from Kansai area with average summer outdoor temperature of about 27°C indicated 19% energy savings. At the refrigerator temperature range the CO2 unit proved to be on average 16.2% more efficient throughout the year than conventional inverter type R404A system. The CO2 refrigeration system is currently installed in approximately 450 stores in Japan. The number of stores is estimated to grow to around 800 by the end of March 2015.

Development of high-efficient CO2 scroll compressor, Atsushi Sakuda, Panasonic Corporation

Commercial production of the CO2 scroll compressor, which is the heart of the CO2 HP water heater (Eco Cute), began in 2003. The development has continued in the direction of increasing energy efficiency and minimising the losses. There are four loss factors in the compressor:
  • motor loss,
  • mechanical loss generated at sliding portions of bearings,
  • compression loss through leaks via clearances and over-compression, and
  • suction loss due to suction heating and leaks from compression chamber to the suction chamber.

To improve motor efficiency and reduce suction heating in a CO2 scroll compressor the researchers at Panasonic renovated the path of discharged refrigerant gas. In addition, with respect to increased oil circulation ratio (OCR) associated with a change of the discharged path a rotation separation mechanism that centrifuges oil in the refrigerant was developed.

Ongoing NEDO projects - Technology development of high-efficient non-fluorinated air-conditioning systems

New Energy and Industrial Technology Development Organisation (NEDO) presented overview of low GWP research projects conducted in cooperation with industry. One of the projects is looking into applying CO2 refrigerants in the air-conditioning sector. In the 2011-2015 project with Daikin, NEDO is aiming at developing a specialised high efficiency multi-stage CO2 compressor, optimised air-to-CO2 heat exchanger and valves. Developed components and elementary techniques will now be tested and evaluated before the planned project completion in 2015.

High efficient technology of scroll compressor using the change of oiling, Isamu Tsubono, Hitachi, Ltd., Hitachi Research Laboratory

Researchers at Hitachi improved the efficiency of CO2 scroll compressor for domestic heat pump water heater by 2-5% on all operation conditions by changing the oiling system. The scroll compressor has a back-pressure chamber to be established on the back side of the orbiting scroll and has an oiling system delivering oil to bearings. The oiling system uses difference between discharge pressure and back-pressure. The scroll compressor with improved design has been used in the heat pump water heaters since autumn of 2012.


By Klara Skačanová

Dec 05, 2014, 16:02

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