The UK''s Coolideas Ltd launched its multi-role refrigeration plant for fishing vessels in January this year, after a fully functional test plant was installed on a small Scottish fisher in August 2006 and has been monitored since then.
The equipment is called a 'Marine refrigeration power pack' (MRP) and is a "high efficiency, marine refrigeration power-pack, invented for a new breed of fishing vessel to produce top quality, fish and shellfish products, through state-of-the-art preservation and processing methods".
New methods of fish preservation require specialist refrigeration equipment, enabling these high quality targets to be met.
Equipment to maintain the high quality of fish required by discerning markets, is generally large, complicated and costly. This usually limits such equipment to vessels of appromately 30m or more.
Coolideas claims that the MRP brings this capability to all fishing vessels, from as small as 10m.
The MRP employes a conventional, but very compact, flooded type, refrigeration system, (primary system), to support a series of slurry ice production cylinders (secondary refrigerant system).
The slurry ice, produced from filtered raw seawater, has the thermodynamic properties of a true refrigerant, i.e. latent heat absorbtion by phase change. The slurry is pumped from the point of production, around the fishing vessel in a loop, including the fish hold, where the slurry enters a hair-pin type, pipe coil configuration, completely covering the deck-head of the holding area.
The pipe coil is constantly pressurised by a two-stage raw seawater pump. This pump, provides both condensing water for the refrigeration plant, and make up water for the slurry ice supply loop.
As slurry ice is drawn from the recirculation loop, an equal quantity of raw seawater is added to the loop for transforming into slurry.
The ice slurry harvesting pressure is therefore equal to the condensing water pump delivery pressure (approximately 1.5 bar is adequate for most applications).
The pipe coil, is designed to provide three important primary needs:
• Keep the fish hold of the vessel below 3oC (unlike conventional 'fin-coil' evaporators in the hold, the pipe coils maintain a desirable high humidity)
• Provide a substantial slurry ice storage volume within the tube coil itself (eliminating the need for a stirred storage tank)
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• Provide slurry ice on-tap, at various vantage points around the vessel, for ad-hock use during careful handling of freshly caught product
The over all size of the slurry ice plant is decided by the total heat load of all refrigeration requirements on board.
The total refrigeration requirement can include one, or all, of the following heat sources:
• 'Cascade' refrigeration condensing medium for special low temperature (minus 60oC) blast freezers
• Accurate temperature control of onboard, live fish tanks, at any temperature from zero to ambient
• Chilled storage of provisions for domestic (galley) perishables
• Air conditioning and humidity control of designated volumes, e.g. cabins, wheelhouse, saloon, etc.
To complete the calculation, the total 'tonnage' of refrigeration required, is matched to an ice machine with a production capacity greater than the calculated total. Thus, the primary cooling requirements of any fishing vessel, are catered for efficiently and simply.
Coolideas describes the MRP as an innovative yet simple answer to-state-of-the-art refrigeration needs.
