GUIDE North America Case Study: Mayekawa ammonia/CO2 supermarket installation

Supporter Case Studies form an integral part of shecco’s GUIDEs to Natural Refrigerants publication series, providing real-life examples of successfully implemented natural refrigerant installations. In the recently released North American GUIDE, MYCOM Mayekawa, a leading provider of energy efficient compressors and thermal systems, presented their Low Refrigerant Charge Ammonia/CO₂ Chiller in a Supermarket Application.

MYCOM Mayekawa was approached by SUPERVALU to develop a low charge ammonia/CO2 chiller that would be part of a CO₂ cascade refrigeration system for an Albertsons test store in Carpinteria, California. Bringing together the most trusted names in supermarket refrigeration, the pioneering project shows the strength of an all-natural refrigerant store, particularly in terms of energy efficiency.

High efficiency ammonia chiller shows preliminary advantage of over 30%

For the first all-natural store in the USA, MYCOM designed and built an ammonia chiller unit consisting of the compressors, condensers, and a CO₂ heat exchanger. Thanks to the system’s combination of a flooded heat exchanger, energy efficient compressor, ammonia as a refrigerant, and water-cooled condensing, a preliminary energy advantage of over 30%, compared to a conventional Freon type system has been shown. This is a significant leap forward in efficiency.

In designing the unit a skid was developed that was bulletproof and could be used to prove the concept of using ammonia in a supermarket application. Easily available industrial components were used for ease of replacement and familiarity to the service base in the area.

About the MYCOM Mayekawa system

To supply the store with a refrigeration capacity of 860 kbtu/ hr (~71tr) a MYCOM M Series reciprocating compressor was used. The M series is MYCOM’s next generation reciprocating compressor, specially designed for use with natural refrigerants with high efficiency. The compressor is coupled to a 125 hp motor with variable frequency drive (VFD). The VFD can match load conditions in the store to make sure the system is always operating most efficiently.

Many design elements were included in the skid to reduce energy consumption and ensure safety, such as:

Flooded plate/shell heat exchanger: this is used to condense the CO₂ vapour returning from the store back to a liquid, increasing efficiency over a direct expansion system.
Low charge: the charge of the unit kept low so that the risk of an ammonia release was mitigated by the small amount of ammonia in the system. This unit, even with a flooded design, has a charge during start up of 250 lbs (113 kg).
Ammonia sensors: provide early warnings of a release and shut down the compressors to mitigate a release, a critical design element since this unit was placed in a retail location.
High powered fans: blow the ammonia up and away from the unit in the event of a release.
Prevention of over pressurisation: by enabling pressure to be blown down from high points in the system to the low side.
Unit base pan fully welded: to prevent ammonia from spilling onto the roof and into the store in an ammonia loss situation.

About Mayekawa

Mayekawa MYCOM is the market leader for natural refrigerant industrial heating and cooling installations including heat pumps. More than 25,000 MYCOM compressors are running in over 100 countries.