CARBON DIOXIDE AS REFRIGERANT: WHY, AND WHEN BENEFICIAL

摘要

Based on the Protocol of Montreal and later the Kyoto Protocol, increasingly sharper legislation onrnsynthetic refrigerants made that alternatives have been developed and that techniques from almost arncentury old are reviving.rnOn the other hand, the natural refrigerant ammonia is also subject to increased legislativernrestrictions because of its hazardous effects to humans at reasonably low concentrations in air. Forrnall refrigerants it applies that it is strived for reduced refrigerant content. So far, this is mainlyrnachieved by applying secondary refrigerants like water, glycols, brine and other substances for therntransport of the cold generated. From an energy consumption point of view, the energy consumptionrnof these systems is 15 to 30 % higher than systems where the primary refrigerant also is used for therntransport of the cold generated.rnApplication of CO2 as primary or secondary refrigerant also causes an increased energyrnconsumption compared to an all ammonia system, but for a well designed system, the increase isrnlimited to 5 to 10 %.rnBased on studies and practical experience, it is shown and demonstrated (by calculation) under whatrncircumstances CO2 as primary refrigerant in a cascade system with preferably ammonia, and whenrnCO2 as secondary refrigerant can be applied with the lowest operational costs, including costs forrndefrosting of aircoolers, if needed.