Mechanically pumped liquid overfeed system arrangement. . tors.1 Table 1 shows the required recirculating liquid ﬂow rate. expressed in gallons per For industrial refrigeration systems using ammonia as the. refrigerant. of a mechanically-pumped liquid overfed refrigerant loop, the refrigerant in the recirculating vessel. Ammonia Refrigeration System Safety. Ammonia refrigeration, the technology. • How is ammonia Survey (). ** Source: ASHRAE Position Document on ammonia (RA ) .. Gravity flooded recirculation system. Compressor(s) Liquid overfeed system components.
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T he liquid recirculation system is the most advanced and energy efficient technique in ammonia refrigeration terminology.
The ammonia liquid from surge drum accumulator is forced circulated in the evaporators of cold storages, or freezer, blast freezers air-cooling units through liquid-feed-pumps. For multiple cold rooms and freezers it is supposed to be the best choice to save electric energy as well getting the highest efficiency of the refrigeration systems.
Liquid Overfeed System
These forced-feed ammonia circulation technology has lower energy cost and less operating hours of the ammonia gas compressors. The internal surface of cooling coils evaporator is completely wetted and therefore provides much better efficiency of the refrigeration system. The compressors are protected from liquid slugs resulting from fluctuation system load or controls malfunctioning of multiple units.
Low-suction superheat is achieved where the suction line between the low pressure receiver accumulator and compressor is short. This causes a minimum discharge temperature, preventing lubrication breakdown and minimum condenser fouling. Elimination of Control Valves: No need of Accumulators: There is no need of individual accumulator for every ammonia air cooling unit because one large accumulator surge drum of liquid circulation system.
Refrigerant feed to evaporators is unaffected by fluctuating oveefeed and condensing conditions. The flow control regulators do not need to be adjusted after the initial setting because overfeed rates are not critical.
No Extra Pressure Drop: Flash gas resulting from refrigerant throttling losses is removed at the low-pressure receiver before entering the evaporators. This gas is drawn directly to the compressors and eliminated as a factor in the design of the system low side.
It does not contribute to syxtem pressure drops in the evaporators or overfeed lines.
Liquid Overfeed System | Water Foods Pvt. Ltd.
Increase in Compressor Life: Because of ideal entering suction gas conditions, compressors last longer and there is less maintenance and fewer breakdowns. The oil circulation rate to the evaporators is reduced as a result of the low compressor discharge superheat and separation at the surge drum- accumulator low-pressure receiver. Refrigerant level controls, level indicators, refrigerant pumps, and oil drains are generally located in the plant rooms which are under operator surveillance or computer monitoring.
Ammonia Liquid Recirculation Systems sysgem more convenient for automatic operation and easy to maintain.
Liquid Recirculation Systems are most useful for multiple number of cooling units as well as having multi temperature cold rooms or freezers. Liquid Feed — Ammonia Systems: Generally, the more evaporators used, the more favorable are the initial costs for liquid overfeed compared to gravity recirculated or flooded system. Easy operation and lower maintenance are attractive features for even small ammonia systems.