RACA Journal June 2016 - Page 94

Technical compression systems to a greater extent. ISCEON M089 is a mixture of R125 and R218 with a small proportion of R290. Due to the properties of the two main components, density and mass flow are relatively high and discharge gas temperature is very low. Liquid sub-cooling is of particular advantage. Both of the mentioned refrigerants have relatively high pressure levels and are therefore limited to 40 through 45°C condensing temperature with the usually applied two-stage compressors. They also show less capacity than R13B1 at evaporating temperatures below -60°C. In addition to this, the steep fall of pressure limits the application at very low temperatures and may require a change to a cascade system with, for example, R23 in the low temperature stage. Lubrication and material compatibility are assessed as being similar to the other HFC blends. Alternatives for R13 and R503 The situation is more favourable with these substances as R23 and R508A/R508B can already replace R13 and R503, Refrigerant R170 (Ethane) is also suitable when the safety regulations allow the use of hydrocarbons (safety group A3). Due to the partly steeper pressure curve of the alternative refrigerants and the higher discharge gas temperature of R23 compared with R13, differences in performance and application ranges for the compressors must be considered. Individual adaptation of the heat exchangers and controls is also necessary. As lubricants for R23 and R508A/B, polyol ester oils are suitable, but these must be matched for the special requirements at extreme low temperatures, R170 also has good solubility with conventional oils, however an adaptation to the temperature conditions will be necessary. This was the concluding instalment of Bitzer’s Refrigerant Report 18. RACA Visit www.bitzer.de for extra figures and tables. HUMOUR All about connecti v ity Everything in product deve lopment thes about connec e days is tivity. One co m pa ny ju st came out with a new silent sm oke alarm. Whe n it detects sm it sends you a oke text, tweets yo ur friends, and picture of the po sts a fire on Facebo ok. RACA 92 RACA Journal I June 2016 www.hvacronline.co.za