Operating Experiences with NH3 Dry Expansion Systems Servici
Operating Experiences with NH3 Dry Expansion Systems Servicing Refrigerated Distribution Centers (2015)-Several jurisdictions of the World have either already legislated a phase-down of high global warming (GWP) refrigerants or are in the process of doing so. In June 2013 Presidents Xi and Obama entered into an agreement to work together towards a phase-down of Hydrofluorocarbon (HFC) refrigerants. On the 6th of September during the G20 assembly in Russia, around twenty nations agreed to participate in an HFC phase-down using the Montreal Protocol as a phase-down tool provided other nations would agree to participate. In December 2013 the European Parliament decided overwhelmingly in favor of a 79% reduction in HFC emissions by 2030. Aside from being powerful contributors to global warming, high GWP synthetic refrigerants also feature relatively poor vapour compression cycle efficiencies compared with natural refrigerants such as ammonia. Costs of electrical energy are rising rapidly. In Australia recent cost increases (22.6% as at July 2013 and 13.6% as at July 2014 in Queensland) are mainly the result of changes to the demand for network assets. The rapid uptake of solar panels has given rise to reductions in electricity demand from the grid. In some jurisdictions, demand on some days is below the power plant base load. The unit costs of electricity must therefore rise in concert with reductions in demand to ensure network maintenance can be funded. This is also referred to as the death spiral. The uncertainty with respect to the future of synthetic refrigerants and the rapidly rising electrical energy costs have renewed the focus of refrigerated warehouse operators towards future proofing of new installations and refrigeration system energy performance. By way of two case studies and references to a third installation in a food factory, this paper details the end-user business benefits associated with employing ammonia refrigerant and dry expansion refrigerant feed in small to medium size refrigerated distribution centers. In the case of one study, the energy consumption cost difference between a new dual stage NH3 dry expansion system and a single stage HFC based system servicing a similar sized facility owned by the same end-user in the same suburb is shown. One study describes a fully factory assembled NH3 based engine room comprising compressors, vessels, electrical equipment, engine room ventilation, PPE, controls and weatherproof enclosure ready for positioning on a prepared slab on site. This concept reflects the need to minimize site installation time and post-commissioning maintenance in small rural jurisdictions of Australia. Finally the paper describes future design areas (wish list) that will require attention by contractors as well as product/equipment suppliers in order to make NH3 systems more attractive to those end-users who have traditionally favored HFC systems.
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