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Norway: Breakthrough technology for long term carrot storage

Carrot production and chilled storage can be challenging hence the reason why Lundstad Grønt selected SRS Frigadon to undertake the entire refrigeration project based on experiences with such similar installations in Romania, UK and USA.

Ever with an eye on the future SRS Frigadon a UK company located in Stratford upon Avon and its sister manufacturing partner Frigadon of Halmstad Sweden did its homework before embarking on this large 14,000m³ quadruple chamber carrot cold store installation now recognized as being the first of its kind in Scandinavia.

The deployment of such Frigadon HYCOOL stainless steel chillers and HYCOOL heat
transfer fluids has been contributory to its huge success for both companies.

It is the aim of SRS Frigadon Ltd to supply technically superior long term root and vegetable cold storage for apples, stone fruits and berries as well with efficient zero CO2 emission chilled storage systems.

This is a breakthrough of technology for long term carrot storage and is the first of its kind using HYCOOL potassium formate heat transfer fluids and +GF+ pre-insulated ABS ‘COOL-FIT ‘ pipe work to be undertaken in Scandinavia for such an application.

In so doing SRS Frigadon takes great pride in providing a fluid refrigeration system operating at low pressures of only 1.5bar – tap water pressure. This is the perfect solution compared with the high pressure CO2 systems which operate at high pressures of up to 120bar to the gas cooler.

The HYCOOL fluids manufactured in Porsgrunn, Norway was supplied by HYCOOL GLOBAL LTD and is as it says - ‘a global supplier of HYCOOL fluids’. It takes into account the low ambient temperatures that can be experienced during the cold Norwegian winters.

With its environmental profile of zero GWP (Global Warming Potential) coupled to its low viscosity enables the system to operate at much lower pumping energy costs compared to propylene glycol and other heat transfer fluids within indirect
cooling systems.

The advantage with this SRS (Secondary Refrigerant System) method of cooling is that it enables a low and stable air flow velocity and in so doing enables carrots to be stored 4 to 6 months at 0° to 1°C at a high % RH relative humidity.

Chilled long term storage of carrots means maintaining a RH of 98% and over. One of the worst things that can happen to carrots during storage is when they dry out and this can occur because of the Vapour Pressure Deficit (VPD) between
them and the surrounding storage air. In order to demonstrate the VPD problem, one must remember that warm air can hold more water than cold air.

Carrot freezing injury will likely result at temperatures of -1.2°C or lower.
Frozen carrots generally exhibit an outer ring of water-soaked tissue, viewed in cross section, which blackens in 2-3 days and therefore such evenly distributed cold air which can be achieved from the SRS dual discharge coils avoids such
product freezing injury.

To avoid pathological disorders carrots must initially be rapid cooled to 5°C or below immediately after harvest. This rapid removal of the field heat is absolutely imperative and essential to minimize decay and moisture losses during extended storage period.

With the demands being to supply such a system to operate at a 98% RH at air temperature of +1°C then the HYCOOL fluid was the best selected solution.
This was achieved with the AIA dual discharge coils thus giving a very even distribution of cold air throughout the rooms and as such the system design using HYCOOL fluids enabling a very narrow fluid flow and return TD (Temperature Difference) of -4°C to -1°C to achieve the highest % RH which is essential for long term storage of carrots.

Another significant factor is to minimise risks of product degradation and therefore the higher operating temperature permitted with HYCOOL enables higher evaporation temperatures and lower pressure drops which in turn will reduce compressor energy consumption.

The selected SRS Frigadon stainless steel 300kW chiller with only 4 x 5.5kg R1270 hydrocarbon Bitzer compressor circuits incorporated the SRS method of WFD (Warm Fluid Defrost.) There are no risks with the WFD because this method of defrosting is rapid by virtue of the fact that warm HYCOOL is circulated through the coils thus ensuring a quick defrost. The principle idea with the WFD is to allow the HYCOOL temperature to rise thus effectively melting the ice (if any) from within the coil with the minimum of disturbance to temperature and humidity balance within the carrot
cold stores.

Such a defrosting strategy means that the compressors do not need to run longer to remove all of the unwanted defrost heat which can be generated within other types of refrigeration installations thus minimising defrosting costs.

Low pressure 1.5bar HYCOOL fluids do not cause any pipe work thermal stress, maintains correct humidity levels and the temperatures will remain constant.

HYCOOL enables the very rapid removal of product field heat which is crucial for postharvest carrot storage but is unachievable with other heat transfer fluids.

In summary it can be seen that the influence of the HYCOOL heat transfer fluid plays a significant part with its increased thermodynamic properties compared with other fluids.

Such system engineering with SRS Frigadon HYCOOL cooled chillers will ensure the long term preservation of carrots in terms of crispiness, flavour and minimise shrinkage matching the quality on the day that the carrots were harvested.

The SRS engineering design included the SRS°Kilowatch energy management control system.

Whilst the SRS°Kilowatch was installed to ensure energy savings and energy monitoring the system will provide a communications facility for delivering alarms via mobile phone and internet and allows for remote chiller control access. Being able to interrogate the installation performance enables service and maintenance time and costs to be minimised.

Further energy savings are achieved by means of the EC Low Energy fans fitted to the Frigadon air cooled chiller together with its built-in PEO (Pump Energy Optimisation) which reduces the mass flow of fluid when the cooling demands are

In line with the client’s expectations SRS Frigadon also supplied the fresh air ventilation; heat recovery and the 300kW Frigadon air cooled chiller system with its high COP (Coefficient of Performance) which has only 22kg charge in total of
R1270 hydrocarbon zero CO2 emission primary natural refrigerant gas.

In line with the new F-Gas Regulations such an installation using hydrocarbon refrigerants with a high environmental profile and minimal energy consumption will ensure the client’s green credentials.

A combination of the minimal CO 2 emissions with the +GF+ Cool-fit pre-insulated pipe work compared with copper, the natural refrigerant chillers, zero GWP HYCOOL fluids together with the added benefits of using the SRS°Kilowatch system collectively contributed to the client being able to obtain a development grant.

Whilst SRS (Secondary Refrigerant System) is not a new concept in refrigeration engineering, the industry is facing the challenge of phasing out the use of traditional volatile refrigerant gases in search of more efficient methods of reducing the adverse environmental effects of those synthetic HFC refrigerants and to minimise CO2 emissions.

Reliable SRS refrigeration systems are dependent upon simplicity

The results of this are proving that the economics in terms of energy usage and plant performance are based on a combination of the efficiencies of all the component parts determined by compressors, coils, heat transfer fluids as well as
valves, pumps, piping, insulation plus other component parts of the system and the design concept by which it is all brought together.

In conclusion the proven performance supported by its green credentials has given the industry further confidence thus paving the way for more food processors, growers and food distributors to consider installing these economic and
sustainable Secondary Refrigerant Systems.

The entire proposal was scrutinised and supported by Sintef in Trondheim.

SRS Frigadon Ltd

Tel: +44 (0)1789 450 982
Email: [email protected]
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