Home Freezing strategies When blast freezing foodstuff there are basically...Read More
When blast freezing foodstuff there are basically two approaches – Speed or convenience.
The difference can be up to 80% in energy consumption
Speed or excellence?
When blast freezing foodstuff there are generally two basic freezing-strategies;
in which the products are aimed frozen as quickly as possible in order to fully utilize the capacity of the blast freezer
in which the company has a natural ”operational cycle” – perhaps with 24 or 36 hours shifts, after which the blast freezer is emptied and reloaded. Here the freezing-strategy is to match the freezing-time to such cycles.
And how is this of importance?
Well – it is obvious that shorter freezing time requires more energy, as the main driver for cooling products in your blast freezer is the combination of temperature and air-flow – both factors which require energy.
But did you know that the energy-consumption develops exponentially as air-flow is adjusted?
The explanation to this is that increased air/flow requires more energy to your fans and cooling unit. As the fans generate heat during operation increased fan-speed will require even more energy just to cool its own heat.
The general relation between air-flow, energy consumption and freezing time is illustrated in the graph on the right:
Data is derived from a test carried out in a rather effective 20” test-blast freezer.
Figures will of course vary in-between various blast freezer set-ups – but the tendency is general and more likely in an even worse relation.
The above graph illustrates how the energy-consumption is exponentially increasing as air-flow is increased in order to shorten freezing time.
In the example above an air-flow (illustrated on the button axis) of 2,4 m³/s will result in a freezing-time of nearly 36 hours – entailing a total energy-consumption (illustrated on the right axis) of approx., 13 kWh. If air-flow is increased to 6,5 m³/s freezing time (illustrated on the left axis) is reduced to approx. 30 hours while the energy consumption is increasing to 81 kWh.
In other words; By reducing the freezing time with 6 hours or 16%, energy-consumption will be six-doubled
As energy consumption increases exponentially the figures can be even more alarming when looking at a reduction from lets say 31½ hours at 5 m³/s to 27 hours at 6.5 m³/s. In this case the energy consumption will double in order to save 4½ hours or 13% freezing time.
If freezing capacity is a bottleneck in the operation the above might be the only possible strategy, but generally the balance between freezing time and energy-consumption should always be in focus.
Learn more about freezing strategies in this video
Did you know?
Amongst others, VDKL (Verband Deutscher Kühlhäuser und Kühllogistikunternehmen – The German union of cold storage and logistics) highly recommends using spacers in blast-freezing processes.