KEY PARAMETERS FOR COMPARISON OF LOWCHARGE AMMONIA SYSTEMS The systems described above all come with their own set of advantages and potential drawbacks. When selecting a low-charge ammonia system, it is important to first consider the application to determine which system will be most suitable. Cost will also always be a key deciding factor for system selection. It is important to not only look at capital expenditure (CAPEX) of the equipment. Instead, it’s worth considering the total life cycle cost, which includes maintenance and installation costs – as well as energy consumption. The various low-charge ammonia systems discussed compare as follows in terms of ammonia charge, cost (installed and maintenance cost), energy consumption, and applications.
AMMONIA CHARGE All low-charge ammonia systems have significantly reduced ammonia charges compared to the recirculated pumped system type. The International Association for Refrigerated Warehouses (IARW) released a white paper in 2014 entitled “Low Ammonia Charge Refrigeration Systems for Cold Storage” wherein it ranked these systems in terms of ammonia charge in lbs/TR [kg/kW], from highest to lowest. According to the report, the highest ammonia charge is contained within a DX system [7.5lbs/TR; 0.95kg/kW], followed by a cascade system [6lbs/TR; 0.76kg/kW] and an indirect system [6lbs/TR; 0.76kg/kW]; with the lowest charge being for a packaged system [4.3lbs/TR; 0.54kg/kW]. Interestingly, while the charge variation between the different types of low-charge systems is quite minimal actually, the difference between a traditional recirculated pumped system [23lbs/TR; 2.9kg/kW] and a DX system [7.5lbs/TR; 0.95kg/kW] is more significant.
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