Daniel Street Fish Market

Stage 1 Freezer System 1

We recently upgraded the System 1 Freezer Room condensing unit to a brand-new custom engineered, energy efficient and Australian built semi hermetic condensing unit from Beijer Ref. With compressor starting peak demand reduction in the ballpark of 80%, the inclusion of a Danfoss Variable Speed Drive (VSD) provided a short return on investment while improving operational efficiencies and capacity control.

Stage 2 Prep Room

Installation of a designated Prep Area cooling system allowed for a reduced temperature holding and preparation area. By maintaining a lower average temperature in this middle room, the influx of ‘unconditioned air’ and humidity has been significantly reduced during the frequent opening of the main freezer and coldroom doors, hence reducing the load on these larger systems. A suitable VSD and low GWP R134a refrigerant was utilised to provide a cost effective and efficient system.

Stage 3 Freezer System 2

As a result of a recent catastrophic failure of the System 2 compressor, it was decided to continue with the energy efficiency mindset and fully upgrade the second freezer system. This time, a complete circular approach was undertaken in the design & engineering process. Heat reclamation and embedded glycol defrosting were included to provide a full cycle utilisation approach, providing the most efficient and effective total system.

• VSD – allowed for soft starting, compressor ramping, capacity control and over-spin.
• EC Condenser Fans – provided consistent & precise control over desired head pressures.
• Heat Recovery – transferred high discharge refrigerant temperatures to the thermal mass tank.
• Embedded Glycol Defrost – eliminated electric defrost heaters and utilised waste heat.

Stage 4 Hot Water Thermal Battery

With a constant generation of wasted heat, the two large Freezer Room systems were maintaining the thermal mass tank at temperature above 70degs, even during the defrost process. As much as this heat was now utilised, defrosts only lasted 20 minutes every 8hrs. There was so much more potential to be used in other ways. Relying on our experience and utilisation techniques from Beefy’s Pies Factory, we integrated a third heat exchanger into the loop. This time, transferring heat away from the thermal mass, into mains water to be used as a designated wash down hot hose. This process generated virtually unlimited free hot water (65degs +). And by using more hot water, this then dropped the thermal mass tank temperature down, and in turn allowed for continual removal and transfer of heat away from the refrigeration systems, further reducing their load again.

Stage 5 Sub Cooling

Further expansive thinking of ways to improve operations and total site efficiency saw the integration of a Cascade system to provide supplementary sub-cooling to the two Freezer Systems. The recently installed Prep Area Refrigeration system had plenty of capacity when required, by means of a VSD and large condenser, however outside of the hottest 3 months of the year and busy loading/unloading times, the system rarely ramped up to its maximum capacity.

We installed a designated pipework set to provide additional subcooling of the liquid lines of the two-freezer system through means of a series of heat exchangers. Subcooling is the process of cooling liquid refrigerant below its saturation temperature, prior to entering the TX valve. By artificially cooling this liquid line, it increases system efficiency and capacity by ensuring the refrigerant is fully liquid before reaching the expansion valve, reducing the risk of vapor formation (flash gas) and improving heat absorption. This leads to a higher Coefficient of Performance (COP) and increased cooling capacity, without requiring additional electrical input.

The implementation of the cascade system reduced our liquid line temperature from a typical 40+ degrees down to 16 degrees. This additional sub-cooling provided a 32% increase in compressor capacity in both systems. Input energy (kVA) remained the same, however the VSD output to the compressors dropped from 29amps / phase to 26amps / phase, meaning a 10% reduction in required running current. Basically, the systems were providing ‘more’, but for less ‘work’.

This was a significant improvement, as we were able to further drop the room’s temperature beyond its original design conditions, but still allowed the systems to achieve their desired setpoints quicker, and hence off cycle more frequently.