Refrigeration System

Ammonia/CO2 Refrigeration Systems

Mainly including ammonia/CO2 secondary refrigerant refrigeration systems and ammonia/CO2 cascade refrigeration systems.
Characteristics of CO2 Refrigerant
CO2 is and entirely natural refrigerant(ODP=0,GWP=1);
CO2 has goods safety and is nontoxic and incombustible;
High refrigerating capacity per unit volume,small compressor volume at the same refrigerating capacity; as shown in Table 2-1,The gas-liquid characteristics of CO2 greatly reduce CO2 gas lines.
Comparison of heat exchange efficiency of CO2:In the low temperature heat exchange area,the heat exchange efficiency of ammonia etc. Is reduced as temperature decreases,whereas the heat exchange efficiency of CO2 is not reduced as temperature decreases;Under the same terminal condition, the heat exchange temperature difference of CO2 is less than that of NH3. The lower the temperature, the large the heat exhange temperature difference. In general,3~4℃ heat exchange temperature difference can be reduced. The COP of the system is decreased by 3~7% every 1℃ increase in heat exchange temperature difference.
Excellent flowing and heat transfer characteristics;
Low price, easy to obtain.
Good chemical stability,small chemical reaction of relevant materials;
The operating pressure of CO2 is higher than that of conventional refrigerants;however,as CO2 is nontoxic, CO2 refrigeration lines and conventional refrigerant refrigeration lines belongs to grade GC2 pressure lines.
The critical point of CO2 is at low temperature:31.1℃(88.0℉).