Cold Link Africa July/August 2019 | Page 41

FEATURE INCORPORATING COLD CHAIN Reciprocating vs screw compressors – how do you choose? By Russell Hattingh, engineering manager at Johnson Controls Systems and Service, South Africa. What would you choose for your HVAC&R applications: reciprocating or screw compressors? The age-old debate continues. vs Reciprocating versus screw compressors — how do you choose? T here is no single answer to this question of choosing between recips and screws — it depends on the application, operating conditions, and attitudes. New recip advances may win these compressors a few more converts, however … In South Africa, as elsewhere globally, there has been a move away from recip compressors in the HVAC industry for more than a decade, with scroll- type chillers taking some market share. Demand for recips is still high for certain applications, such as cold stores and process cooling, however. The short answer is that each compressor type has its particular advantages, depending on the required operating conditions.  To make an optimum selection, the actual application conditions must be analysed. Relevant criteria, such as required capacity, operating conditions, part load, energy consumption, temperature levels, refrigerant, ease of maintenance, investment, and available space should be taken into consideration. Let’s take a look at the fundamental differences. Reciprocating compressors: Recips are piston-driven compressors delivering stepped control with specific output per piston. They work well in high- temperature applications, delivering energy savings. They typically use ammonia refrigerant, which is in demand COLD LINK AFRICA • July/August 2019 as it is considered a more naturally eco- safe option. R&D by large manufacturers for recip compressors continue to deliver enhancements and new features that keep the compressor evergreen. Screw compressors: Screw compressors offer a higher capacity output, larger compression ratios, and smoother control to deliver energy savings in large applications. A later evolution of the compressor, they are considered more 41