Summary
Coldstore Hengelo bv, located in Hengelo, the Netherlands, has built a new frozen food storage facility that uses a direct-expansion (DX) ammonia cooling system. Compared to existing direct-expansion systems using refrigerants R507 and R404A, ammonia is an energy-efficient and environmentally friendly refrigerant. Larger ammonia cooling systems normally include systems with storage vessels, where a separate pump distributes the liquid ammonia to the evaporators. The vapour from the evaporators is collected in the vessel and eventually drawn out by the compressor. The refrigerant content of direct-expansion systems is substantially smaller (approximately 80% less) than the regular ammonia systems, increasing safety. Inspections can be carried out as part of the annual overhaul. A number of cooling cycle optimisation measures have been incorporated into the system design, such as oil washers and electronic expansion valves. Another DX ammonia liquid cooling system has already been demonstrated for temperature and humidity control using ice water for malt production (breweries). However this project demonstrates the direct-expansion system for multiple air coolers located some distance away from the engine room, and incorporates a DX hot gas defrost system. Total project costs amount to NLG 837,000. This is approximately NLG 135,000 more than conventional systems. Total energy savings amount to 310,000 kWh per year (or NLG 42,000). Additional cost savings for maintenance and inspection amount to NLG 15,000. The payback period on the extra costs is therefore approximately 2.5 years.Applications for direct-expansion ammonia refrigeration systems can be found in all sorts of industrial cooling and refrigerating plants in the food processing and other industries.