" I believe that ammonia holds an undisputed position as a future-proof refrigerant. It ' s unaffected by international protocols like Montreal and Kigali and does not contribute to the production of PFAS and TFA’ s as done by low GWP synthetic refrigerants. For any long-term investment in refrigeration, especially in large industrial applications, ammonia should be the primary consideration,” said Steyn.

" Ammonia has a robust legacy in South Africa, with over a century of proven use. The local industry boasts strong support from manufacturers, engineers, contractors and service providers, making it a reliable and resilient choice. As I ' ve said before, ' It ' s old, but it is bulletproof and for a lot of applications there ' s simply no alternative’." However, South Africa ' s operating environment presents unique challenges. Escalating electricity prices and a pervasive KVA shortage( a widespread lack of available grid power) significantly impact operational costs and limit expansion opportunities for many businesses. Customers often face transformer capacity constraints, with upgrades taking five years or more. While alternative power sources like solar and generators exist, Steyn advocated for proactive measures to cut down on peak power demand directly from refrigeration systems.

Steyn stressed that while equipment manufacturers continue to invest in advanced ammonia compressors and control systems, the onus is on engineers and designers to optimise overall system design.

CASE STUDY: 400 KW LOW- TEMPERATURE AMMONIA PLANT

To illustrate practical optimisation, Steyn presented a real-world case study: A 400 kW low-temperature ammonia freezing plant served as a case study for optimisation, with the client ' s goal being to expand within existing transformer capacity in a warm, dry South African climate.

A two-stage ammonia system was chosen as the most efficient solution, paired with evaporative condensers to optimise fan power and overall system efficiency. Steyn walked attendees through the enthalpy diagram for ammonia, showing the typical operating points. The client ' s specific requirement was a-40 ° C freezing application.

The standard engineering approach focused on optimising key parameters:

• Raising suction pressure

• Dropping discharge pressure

• Optimising the intermediate temperature

" Our optimisation aimed for the lowest overall power consumption. We designed it with a condensing temperature of 30 ° C, with a fallback to 35 ° C if one of the two evaporative condensers was out for maintenance. This ensured we calculated the baseline power consumption at that

higher, more demanding condition." Steyn outlined a standard industrial ammonia system, comprising:

• The 400 kW load feeding into a flash vessel

• Low-stage compressors discharging into an intercooler

• The intercooler creating an induced load for the high-stage compressor, which ultimately rejects heat via the evaporative condensers.

This configuration, a staple in industrial ammonia refrigeration for over five decades, was the foundation. The standard two-stage ammonia system, comprising low-stage compressors, an intercooler, and evaporative condensers, established a baseline power consumption of approximately 218 kW.

" To reduce the high-stage compressor ' s workload, the focus shifted to rejecting energy from the low-stage compressor ' s superheat zone( 10-13 % of total energy) using ambient heat sinks instead of solely relying on compressors."

After exploring various options, including thermos-siphon desuperheaters and air-cooled desuperheaters, GEA opted for a novel approach: integrating the desuperheating process into the evaporative condenser itself.

EVAPORATIVE CONDENSER DESUPERHEATING: A PRACTICAL SOLUTION

" We chose to route the 97 ° C discharge gas

Hannes Steyn, senior director and divisional representative GEA Southern and Eastern Africa.

from the low-stage( booster) compressors through a dedicated coil within the evaporative condenser before it enters the intercooler. The inherent advantage we found with evaporative condensers is their ability to use the wet bulb temperature( in this case, 22 ° C). This gives us a significantly lower heat sink for the hot gas compared to dry bulb temperatures, which allows for efficient cooling of the superheated gas."

Manufacturer data and desktop analysis predicted that routing the 97 ° C discharge gas from the booster compressors through a dedicated coil in the evaporative condenser

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