Recent advances in ammonia dry expansion applications.

The paper will describe the design, installation and operating experiences associated with two evaporators servicing a medium size refrigerated warehouse in Brisbane, Australia. The evaporators each have a capacity of approximately 40 kW. The refrigerant injection in both air coolers is controlled by a combination of superheat signal and refrigerant quality signal both measured at the evaporator exits. The evaporators are specially circuited for ammonia dry expansion feed. The material of construction is aluminium. Two different distributor designs have been installed enabling field comparisons of the performances. Defrost is by means of hot gas using a common defrost drainer. The references to operating experiences will include topics such as:- Comparisons between superheat controlled injection and refrigerant quality controlled refrigerant injection into the evaporators (SH/X control)- Oil management and automation of oil return- Defrost management and control- Humidity ingress into the warehouse and control of same- Recorded energy consumption in kWh/m³*a- Refrigerant charge reduction compared with conventional liquid overfeed systems- Customer satisfaction- Capital cost comparison compared with equivalent HFC based systems.