INDUSTRIAL REFRIGERATION
The industrial evolution
Andre Patenaude of Emerson Commercial & Residential Solutions takes a look at CO2
systems in large industrial applications. /NH3 T
he large industrial refrigeration market is no stranger to the use of natural refrigerants. For decades, ammonia (or NH3
or R717) has been the backbone
of many cold storage applications. More recently, the increasing uptake of carbon dioxide (or CO2
or R744) in
commercial applications has led refrigeration manufacturers to look for ways to exploit this emerging natural refrigerant in industrial applications, and the technology to combine the benefits of both refrigerants and facilitate this transition is coming of age.
With excellent performance efficiencies and ultra- low environmental impacts, in many ways NH3
is the
closest thing to the perfect refrigerant. However, it has one major caveat: toxicity. In recent years, tightening regulations by the United States’ Occupational Safety and Health Administration (OSHA) has sought to improve the safety of NH3
systems. Operators are now required to
provide documentation for systems charged with at least 10,000 pounds of ammonia, as per OSHA’s Process Safety Management of Highly Hazardous Chemicals standard. For these reasons, operators and manufacturers alike began looking for ways to leverage ammonia’s efficiencies while lowering system charges necessary to limit the potential for exposure to workers and product spoilage. Enter CO2
cascade technology, a system architecture that has been successfully deployed in many commercial applications.
/NH3
To make the transition to the large industrial market, manufacturers first needed to find a way to deliver high- tonnage refrigeration capacity while keeping ammonia charges low to help mitigate safety concerns, ease documentation requirements and, if possible, avoid the potential for exposure in any occupied spaces. In addition, manufacturers also needed to address other prevailing
36 May 2018 concerns about the use of CO2 /NH3 cascade systems,
including: ■ Complexities related to installation, commissioning, operation and servicing requirements
■ Potential heat exchanger leaks of CO2 and NH3 that can
mix and create ammonium carbamate and result in system failure
■ Maintaining uptime during the transition from a legacy system to a new cascade system.
meant that manufacturers had to expand upon the existing cascade architecture. Among the leading solutions to achieve this is via a self-contained system that integrates an entire CO2
Meeting high-tonnage, cold storage requirements while addressing the known operational challenges of ammonia and CO2
/NH3 refrigeration unit.
Designed to be located on the rooftop or next to a building of a cold storage facility, this modular refrigeration unit combines CO2
and NH3 compression technologies,
electronic controls and evaporators in a cascade system that contains two independent CO2
and NH3
portion of the cascade system provides the high stage of the refrigeration cycle, using a small-displacement, very low-charge, single-screw compressor and a condenser that sits on top of the unit and uses ambient air to cool it. This design meets the low-charge NH3 than 100 pounds) while keeping the NH3
condensers and heat exchangers. The NH3
requirement (fewer stage completely
portion of the system uses high-pressure, reciprocating compressors and a heat exchanger as a condenser, where the NH3
separate from the conditioned space. The CO2
chills and condenses the CO2 into vapour. The cooled air is then pumped into the facility’s circuits with separate cascade refrigeration
cascade system into a modular
www.acr-news.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72
