Ultra-low charge ammonia chillers for energy efficiency in industrial applications

Panel: 4. Technology, products and systems

This is a peer-reviewed paper.

Authors:
Ammi Amarnath, Electric Power Research Institute, USA
Sara Beaini, Electric Power Research Institute, USA
Mukesh Khattar, Electric Power Research Institute, USA
Aaron Tam, Electric Power Research Institute, USA
Chris Holmes, Electric Power Research Institute, USA
Colin Lee, Electric Power Research Institute, USA

Abstract

Ultra-low charge air-cooled ammonia (R-717) chillers offer versatility for industrial applications with both energy efficiency and water saving capabilities. Field evaluation of this new innovative product demonstrated its energy and water saving potential with the safe usage of zero GWP natural refrigerant based, air-cooled packaged chiller at a food processing industrial host site in the USA. Two key energy efficiency advances of the technology enable the significant reduction of ammonia refrigerant charge by an order of magnitude, specifically by a factor of 20 compared to conventional ammonia-based chillers. The two innovations are: (a) Advanced microchannel heat exchangers, which have improved heat transfer effectiveness due to the increased surface area; and (b) A new, pre commercial, semi hermetic compressor with no mechanical seal between the compressor and the compressor motor.

The advanced microchannel heat exchanger has integrally brazed airside fins, which gives higher heat transfer effectiveness. The heat exchanger is all aluminium; efficiency in heat transfer allows for the same capacity to be delivered with much lower refrigerant charge. A mechanical seal is one of the most vulnerable point of refrigerant leak in a refrigeration system, and this is the first type of compressor compatible for ammonia refrigerant that is available globally.

The new semi-hermetic compressor has aluminium windings since typically the motor windings are made of copper, which are incompatible with ammonia. Accordingly, the combination of these two innovations enabled the development of a packaged, air-cooled, ultra-low charge ammonia- based chiller, which eliminates and reduces the many burdensome regulations that otherwise govern the use of ammonia in industrial plants. The evaluated chiller uses less than 1.5 pounds (0.68 kg) of ammonia refrigerant per ton refrigeration (TR) capacity of the chiller, which corresponds to less than 75 pounds (35 kg) for the 50 TR chiller at the field demonstration site. While the field evaluation project is on-going, the aircooled ammonia (R-717) system has been evaluated against an existing conventional water-cooled chiller with R-507A as a baseline at the food processing site. Field performance results show up to 40 % improvement in energy efficiency and water savings of 2.35 gallons of water per kWh of electricity used by the air-cooled ammonia chiller.

This presentation was unfortunately not recorded due to technical problems. Watch session discussion.