On a special project and based on specific customer request, a hot gas defrost system has been introduced to enhance the performance of low‑temperature remote cabinets.
The system uses hot gas coming from the MT compressors' discharge, which feeds a header on board of the rack kept at 45 bars. A dedicated distribution piping delivers hot gas to the evaporator coil, mainly in the LT cabinets, according to the cabinets defrost scheduling.
The liquid flow in the evaporators is locally diverted by solenoids that close valves in favor of the hot gas flow, expanded by a dedicated a valve at 42 bar.
Condensed liquid is then collected and sent to the main receiver.
- ECO2Large pack
- Hot gas defrost system
- MT design load 177 kW
- LT design load 53 kW
- Store surface: 4100 m2
The choice of hot gas defrost system is driven mainly by energy efficiency: in fact, by reusing heat from the compressor discharge, the system enables faster and more energy‑efficient defrosting compared to electric methods. This solution is particularly effective in stores with a high number of LT cabinets and coldrooms.
Although it’s a tailor-made solution, it has been installed in 7 stores, with another 10 to follow in the future, making such concept suitable for multiple stores.
The picture shows the hot gas defrost header lines, from which all the dedicated lines depart to the cabinets and coldrooms connected to the hot gas system.
The graph shows the trend of the gas cooler and receiver pressure over a period of several months. The key takeaway is the stability of receiver pressure and, hence, liquid delivery, including defrost ON/OFF switches.
The graph shows the trend of discharge air temperature on a selected cabinet, which stays well below 41°F as per NFS specifications also during defrost phase, demonstrating the effectiveness of the hot gas defrost system