Danfoss Technology Centre features only transcritical CO2 presentation at AHR EXPO 2014

By Silvia Scaldaferri, Jan 29, 2014, 10:54 2 minute reading

At the 2014 AHR EXPO in New York, leading component supplier Danfoss, which has almost 4000 trancritical CO2 installations in Europe alone, shared their extensive knowledge and expertise of R744 technology in a one-of-a-kind presentation at their booth. With working pressures over 2000 psi, CO2 transcritical installations experience no phase change, and have a unique set of characteristics that require a complex management system. Danfoss offers a simplified solution.

The Danfoss Technology Centre presentation, provided a comprehensive overview of the equipment needed to manage a CO2 transcritical installation, including electronic expansion valves, a compressor, gas cooler and receiver controls, oil management and heat reclaim. Whilst Danfoss says that the design costs for a CO2 installation remains higher than for competing technologies, these costs are dropping, and when taken into consideration with the 20% energy savings being reported, and the lower cost of the refrigerant, there are strong arguments for investing in this climate friendly technology.

All-important receiver maintains correct pressure; mechanical valves not needed

According to the presentation by Jae Chon the receiver is the most important part of any CO2 transcritical system, mixing liquid and vapour. Thanks to the gas bypass valve and compressor, the receiver maintains the precise pressure required for the system to work efficiently: higher than suction pressure but lower than gas cooler pressure.

Another important feature of transcritical CO2 systems highlighted in the presentation, is the fact that mechanical oil valves are not used, with the oil level instead managed by solonoids, low level sensors at the compressors and reservoir, and high level sensors at the separator.

What is more, due to the pressure differential and response time, Danfoss recommends the use of electronic expansion valves because of their fast reaction time.

Danfoss all-in-one transcritical control solution

Danfoss has greatly reduced the complexities of working with CO2 transcritical installations thanks to the AK PC 781 controller that features all-in-one functionality.

The AK-PC 781 does all of the following:

  • Compressor Control
  • Gas Cooler Control: based on pressure and temperature at the gas cooler outlet the gas cooler control optimises COP
  • Oil management
  • Receiver Control: based on pressure in the receiver, the receiver control bypasses gas in the receiver to improve cooling capacity. It works with the high press valve to prevent high or low pressures in the receiver
  • High Pressure EEV (electronic expansion valve)
  • Heat Reclaim: CO2 transcritical system efficiency is improved with CO2 heat reclaim, becoming up to 150% more efficient than R134a systems and up to 55% more efficient than HFC systems

Danfoss case controllers

In addition to the above, Danfoss offers the AK-CC 550a and AK-CC 750 case controllers that take into account the specific liquid vapour density ratio of CO2, which is 29, compared to 188 for R407A. The controllers also feature adaptive superheat and defrost, and can lead to over 20% energy savings.

Other products in the Danfoss CO2 portfolio include leak detection. Danfoss recommends the use of single zone sensors in walk-in and service areas, to prevent high concentrations of CO2 developing in confined spaces.

About Danfoss

The Danish company Danfoss is a global leader in the research, development and production of high efficiency electronic and mechanical components and controls for refrigeration, air conditioning, heating and motion control systems. The company is dedicated to providing technologies and solutions that combine innovative engineering with energy efficiency and environmental sustainability.


By Silvia Scaldaferri

Jan 29, 2014, 10:54

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