Expanding ammonia’s application range through low charge systems

By Elke Milner, May 08, 2014, 17:34 5 minute reading

ammonia21.com reporters attended a series of presentations on low charge ammonia refrigeration systems during the Nashville IIAR research panels. Presentations from Creative Thermal Solutions, Azane and Mayekawa highlighted new opportunities for expanding ammonia’s application range, thanks to the changing legislative environment. However, a change in perception is necessary for this to become reality, which could be achieved thanks to lower charge systems.

The current political and regulatory climate with regard to HCFC/HFC phase-outs and the increase in research and development into alternative refrigerants offers an opportunity for the replacement of current cooling fluids with future-proof, natural solutions that will not face a phase out schedule.
Until now history has been repeating itself when it comes to refrigerant phase out. Illustrating this fact, Derek Hamilton quoted the founder of Star Refrigeration Forbes Pearson, who in 1995 correctly stated, “CFC refrigerants are now no longer in production. HCFC refrigerants have been allocated phase out dates. Few people believe that the phase out dates for HCFC refrigerants will no be brought forward.” Almost the same thing could be said today, ”HCFC refrigerants are no longer in production. HFC refrigerants are now being phased out, and no one believes that the phase out dates for HFCs will not be brought forward”.
Low charge ammonia systems have future beyond industrial refrigeration 
Within this context, Pega Hrjnak, of Creative Thermal Solutions, believes that ammonia has a future in applications other than industrial refrigeration. As such industry should consider new applications for ammonia, such as chillers or industrial commercial cooling units.
According to Hrjnak the negative perception of ammonia by the general public goes hand in hand with the amount of charge in ammonia systems, and it is these two obstacles that are blocking ammonia use in applications other than industrial refrigeration. ,Cost is another an obstacle. However, there are numerous examples of environmentally friendly, efficient low charge ammonia systems already developed as prototypes, technology which could expand the application range of ammonia as a refrigerant. 
What is more, the public’s perception of ammonia , which has been coloured by accidents involving ammonia leaks and its foul smell, has left a stigma attached to the use of ammonia that is not shared by those working in the industry.  Thus, although  questions concerning corrosion and pressure drop, among others, are clear to experts within the industry, Hrjnak argues that the industry needs to clarify these questions to those who have not been exposed to the technology. 
The industry also needs regulatory clarification and support. Currently, there is no set limit for ammonia charge. Only once this is set, says Hrnjak, can the industry really begin to understand how to move forward. Furthermore, he urged regulatory bodies to identify incentives for lowering the system charge, as it incurs higher costs.
Low charge packaged ammonia systems
As of the first of January 2015, the use of HCFC refrigerants such as R22 will be completely prohibited in the European Union. Those end users that have not taken any measures to address this phase out now find themselves facing a challenging situation. The revised European F-Gas Regulation is also placing a number of restrictions on the use of HFCs, effectively phasing out those high refrigerants with a GWP above 2500, by 2020. 
This refrigerant phase down and phase out has created a growing demand for low charge packaged ammonia systems. Derek Hamilton from Azane (subsidiary of Star Refrigeration), which has a long history of supplying low charge ammonia systems in Europe, therefore, like Hrnjak, sees a big opportunity to start using ammonia in new applications. Ammonia is not going to be phased out, and is a long-proven high efficiency refrigerant.
To illustrate the size of Star’s low charge ammonia packaged systems Hamilton talked about an installation at a relatively small freezer warehouse requiring temperatures of -10°C. The 74-ton refrigeration load was serviced by a small condensing unit connected to 2 enhanced aluminium evaporators, with an ammonia charge of 360lbs (163 kg). In addition to the system’s simple installation, the system’s reverse cycle defrost can also be run at a much lower head pressure than a traditional hot gas defrost system.
Mayekawa calls on industry to work together to find viable solutions for the future 
During his presentation, Mark Tomooka of Mayekawa also mentioned the pressure from government and other institutions to move away from HCFC R22. He placed an emphasis on the importance of alternative solutions developed, to be designed to address the industry in which it will most often operate. Alternatives to R22 must also be cost effective, and safe, and must take into consideration maintenance burden and environmental impact . Tomooka noted that one aspect cannot be traded for the sake of another because “they are all trump cards within themselves.” 
When looking toward the future of ammonia in refrigeration, Tomooka also spoke of the importance of improving the public’s perception of ammonia, so that it is seen in a more positive light.
With regards to new solutions, Tomooka drew attention to Mayekawa’s semi-hermetic ammonia internal permanent magnet (IPM) motor. The semi-hermetic compressor reduces the possibility of a refrigerant leak, and the isolated shaft leads to a maintenance payoff and reduction of compressor motor install length and results in more compact equipment. Furthermore, if the motor burns out, it does not lead to acid formation or contaminate the refrigerant. The system uses water jacket cooling on the motor, which minimises heat generation. The internal permanent magnet allows for size reduction and more flexibility in application. 
The main strength of the semi-hermetic ammonia IPM motor is that the permanent magnets are used on the rotor to induce magnetism which results in roughly 5-10% increase in efficiency over a standard induction-type motor. Because there is not a large rotor, the size is also smaller. There are currently 500 of these in operation. In addition, they come in a packaged system that allows for remote monitoring. Mayekawa is confident that this technology solution has the potential to grow, particularly with regard to compact modules. 
Tomooka concluded with a call to the refrigeration industry to find new ways around challenges, rather than retreating to what is known and what has always been done. He called on the industry to work together to find solutions the industry can implement and use to move forward. 


By Elke Milner

May 08, 2014, 17:34

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