Tag: Heat transfer model

Reports

Instructions for the cooling ability of slurry ice intended for chilling of fish products in fish containers

Published:

01/06/2016

Authors:

Björn Margeirsson, Sigurjón Arason, Þorsteinn Ingi Víglundsson, Magnea G. Karlsdóttir

Supported by:

AVS Fisheries Research Fund (R 034‐14)

Contact

Sigurjón Arason

Chief Engineer

sigurjon.arason@matis.is

Instructions for the cooling ability of slurry ice intended for chilling of fish products in fish containers

Objectives of the project Optimization of fresh fish transport is to improve the handling of fresh fish products in container transport and thereby increase their shelf life and the possibility of further transport by sea from Iceland. In work step 1, the aim is to estimate the appropriate amount and type of ice scraper to maintain the fish temperature at -1 ° C during transport in tanks. Heat transfer models are made from 340 PE and 460 PE food pots from Sæplast to estimate the required amount of ice scraper to maintain -1 ° C inside the pots, which is the optimal temperature for storing fresh whitefish products. Pre-cooling of fish products before packing in pots has a decisive effect on the amount of products that can be placed in pots if it is required to maintain the fish temperature -1 ° C. This is explained by the fact that with increasing fish temperature during packing, an increased amount of ice scraper is needed to lower the fish temperature to -1 ° C, thereby reducing the space for the fish inside the tank. The volume utilization of the pot, i.e. quantity of fish products in a tank, it is of course necessary to maximize in order to minimize transport costs and make sea transport of fish products packed in ice scrapers in a tank a viable alternative to sea transport in foam boxes. These guidelines should be used to estimate the amount of fish products that can be packed in 340 PE and 460 PE Sæplast tanks. The aim is to pack the fish in an ice scraper with a temperature of -1 ° C, an ice ratio of 35% and a salinity ratio of 1.2% and the amount of ice scraper is sufficient to maintain -1 ° C in an ice scraper and fish for four days at ambient temperatures between -1 ° C and 5 ° C. It should be noted that the instructions only take into account the need for refrigeration and not a possible, undesirable color that can be created on the bottom fish layers in a tank and can potentially cause loss of utilization and quality.

The aim of the project Optimization of fresh fish transport is to improve handling of sea transported fresh fish products, thereby improving their quality and increasing the possibility of sea transport from Iceland. The aim of work package no. 1 is to estimate the suitable quantity and type of slurry ice in order to maintain the optimal fish temperature of –1 ° C during transport in fish containers (tubs). Heat transfer models of 340 PE and 460 PE fish containers manufactured by Saeplast are developed for this purpose. Precooling of fresh fish products before packing in slurry ice in containers has a dominating effect on the maximum fish quantity, which can be packed in each container assuming a maintained fish temperature of –1 ° C. This is because an increased fish packing temperature increases the required amount of slurry ice in order to lower the fish temperature down to –1 ° C, thereby decreasing the volume for fish within the container. The fish quantity within the container must certainly be maximized in order to minimize the transport cost and make sea transport of fresh fish products in slurry ice in containers a viable option. These guidelines should be useful to estimate the fish quantity, which can be packed in 340 PE and 460 PE Saeplast containers. The temperature, ice ratio and salinity of the slurry ice assumed are –1 ° C, 35% and 1.2%, respectively. Furthermore, it is assumed that the amount of slurry ice applied is sufficient to maintain the slurry ice and fish at –1 ° C for four days at ambient temperature between –1 ° C and 5 ° C.

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Reports

Superchilled Round Fish - Final Report / Supercilled Whole Fish - Final Report

Published:

01/03/2013

Authors:

Björn Margeirsson, Valur Oddgeir Bjarnason, Sigurjón Arason

Supported by:

AVS Fisheries Research Fund (R 11 062‐11)

Contact

Sigurjón Arason

Chief Engineer

sigurjon.arason@matis.is

Superchilled Round Fish - Final Report / Supercilled Whole Fish - Final Report

The main objective of the project "Super-chilled whole fish - for death solidification", which began in July 2011, was to investigate whether super-cooling of whole fish on board a fishing vessel could extend the shelf life and increase the quality of the products. Appropriate temperature and time settings for red and touch refrigerators were sought with four refrigeration experiments and the best settings were used to supercool whole fish in a shelf life experiment. The results of a shelf life test indicate that supercooled processing of whole cod can extend its shelf life by two days. According to sensory evaluation, however, there was little difference in the shelf life of different fillet groups. Shelf life was estimated at 16-18 days, which is quite a long time for cod fillets. However, the freshness period of the experimental group with super-chilled fillets of super-chilled whole fish seemed to be somewhat longer than the other groups. As with whole cod, there was little difference between the fillet groups in terms of microbial growth, chemical and physical properties. Limited differences between experimental groups can possibly be explained by stable and supercooled storage conditions. With this in mind, it is recommended to carry out another similar experiment, simulating more typical environmental temperature processes in the transport of fresh fish products (0–4 ° C) than in this experiment (–1.4 to –1.2 ° C). The results of computerized thermodynamics and hydrology modeling indicate that such models could be used for the continuous design of red and touch chillers for whole fish.

The main aim of the R&D project "Superchilled round fish - pre ‐ rigor", which was initiated in July 2011, was to investigate whether superchilled processing of whole fish on ‐ board fishing ships could increase product quality and prolong storage life. The appropriate temperature and time settings for the superchilling equipment were studied in four cooling trials and the best settings applied when preparing samples for a storage life study. The results from the storage life study indicate that superchilled processing of whole cod can extend storage life by two days. However, differences in sensory scores between the fillet groups were small. Storage life was estimated between 16 and 18 days which is quite long storage life for cod fillets. However, the group with superchilled fillets from superchilled whole fish seemed to retain freshness a little longer than other groups. As in case of the whole cod, the differences in bacterial count, chemical and physical properties between the fillet groups were small. Very similar fish temperatures between both the whole fish and the fillet groups resulting from the superchilled storage conditions applied may be the main reason for the small differences obtained. Thus, another study with more common temperature conditions during transport and storage of fresh fish (chilled but not superchilled) should be performed. The results obtained in this study show that CFD modeling of fluid flow and heat transfer is a realistic and functional tool to simulate superchilling of whole fish in a CBC ‐ cooler. In future work CFD modeling can be used to determine optimal values for parameters such as holding time, chilling temperature and air velocity. 

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Reports

Thermal modeling of processing and transport of fresh fish / Hermun kæliferla - LOKASKÝRSLA

Published:

01/09/2011

Authors:

Björn Margeirsson, Sigurjón Arason, Kristín Valtýsdóttir

Supported by:

AVS Fisheries Research Fund, Technology Development Fund, University of Iceland Research Fund

Contact

Sigurjón Arason

Chief Engineer

sigurjon.arason@matis.is

Thermal modeling of processing and transport of fresh fish / Hermun kæliferla - LOKASKÝRSLA

The main objective of the project Simulation of cooling processes - thermodynamic simulation of production and transport processes, which began in June 2008, was to present improvements in procedures and equipment related to the transport of marine products through process analysis, experiments and computerized thermal and hydrological models. The consequences of improved temperature control in production and transport processes are increased quality, stability and safety, which at the same time increase the value of the product. Partners in the project were Matís, the University of Iceland, Promens Tempra, Eimskip Ísland, Samherji, Brim (ÚA), Festi, Völusteinn and Eskja. This report describes the main results and products of the project. Examples of products are heat transfer models of fresh fish products in a foam box, which make it possible to predict fish temperatures based on environmental temperature history. Heat transfer models were used to redesign the Promens Tempra 3, 5 and 7 kg foam boxes with the minimum target fish temperature minimization under the target heat load. Experiments confirmed the superiority of the new boxes over traditional box types, both in terms of temperature control and product quality under heat load. The results of another experiment show that the shelf life of fresh fish fillets in corner boxes of whole pallets in the air transport chain can be about 1-1.5 days shorter than fillets in boxes in the middle of the pallet stack. Heat distribution in different cooling chains was mapped and special emphasis was placed on pre-cooling fillets for packing and heat distribution in different types of cooling containers with different loading patterns. 

The main aim of the research project Hermun kæliferla - Thermal modeling of processing and transport of fresh fish, which was launched in June 2008, was to improve technology and practices used for fish processing and transport by means of analysis of chill chains, experiments and computational modeling. Improved temperature control in fish chill chains leads to increased product quality, stability and safety and thereby increased product value. This report describes the main results and products of the project. Examples include heat transfer models of fresh fish fillets packaged in boxes, which can be used to predict product temperature evolution as a function of variable ambient temperature. Numerical heat transfer models were used to optimize the design of 3, 5 and 7 ‐ kg expanded polystyrene boxes manufactured by Promens Tempra with the aim of minimizing the maximum fish temperature in boxes under thermal load. Improved thermal protection of the new box design was confirmed in different experiments, both with regard to lesser product temperature variations and extended freshness period and storage life of products. The results from another storage study suggest that the storage life of fresh fish products in a corner box can be more than 1‐1.5 days shorter than in the center boxes of a full size pallet stack in a real air transport chain, depending on the level of ambient thermal load. Environmental and product temperatures were mapped in different chill chains with special emphasis laid on precooling during processing and temperature distribution in reefer containers of different types and loading patterns. 

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Reports

Increased value of pelagic species - FINAL REPORT / Increased value of pelagic species

Published:

01/05/2011

Authors:

Lárus Þorvaldsson, Björn Margeirsson, Ásbjörn Jónsson, Sindri Sigurðsson (SVN), Ásgeir Gunnarsson (SÞ), Sigurjón Arason

Supported by:

AVS Fisheries Research Fund

Contact

Sigurjón Arason

Chief Engineer

sigurjon.arason@matis.is

Increased value of pelagic species - FINAL REPORT / Increased value of pelagic species

The main objective of the project Increasing the value of pelagic fish - improved refrigeration technology, which began in June 2008, was to lay the foundations for a new method of cooling and storing pelagic fish on board seiners. The result of improved cooling is that a higher proportion of the catch is useful for human consumption. Partners in the project were Matís, Síldarvinnslan (SVN) and Skinney Þinganes (UN). This report describes the main results and products of the project. Examples of products are heat transfer models of pelagic catches in ships and storage tanks on land and the integration of heat transfer models and quality forecast models, which make it possible to predict the quality of raw materials based on environmental temperature history. Heat distribution in pelagic vessel loads with different versions of cooling systems was mapped and storage temperatures were linked to quality measurements made during landing. From temperature and quality measurements it is clear that the frequency of defects in landed catch increases with increasing storage temperature. The main advantage of the MCS (Mixed Cooling System) cooling system, which combines CSW (Chilled Sea Water) and RSW (Refrigerated Sea Water) cooling systems, is that the system can reduce the inevitable temperature rise that occurs in a pre-cooled vessel following the pumping of catch in lestina. During the project, the Icelandic mackerel fishery was the largest and it can be stated that the results of the project have been used very well to improve the results of food processing of mackerel in this country and thus increase the product prices of a valuable species.  

The main aim of the research project Increased value of pelagic species - improved chilling methods, which was initiated in June 2008, was to develop a new method for chilling and storing pelagic species on board purse seiners resulting in more valuable products. This report describes the main results and products of the project. Examples include heat transfer models of pelagic fish stored in a ship hold and a storage tank onshore and coupling of the heat transfer models and quality forecasting models, which makes it possible to predict spoilage of pelagic species as a function of ambient temperature history. Temperature distributions in ship holds with different cooling systems were mapped and storage temperature related to quality measurements conducted during landing. The fault ratio of landed raw material clearly increased, indicating lower quality, with higher storage temperature. The main advantage of a mixed cooling system (MCS), which combines RSW and CSW systems, compared to using only RSW is a lower temperature increase in a precooled ship hold caused by loading the catch in the hold. During the project, the emphasis on mackerel fishing increased significantly around Iceland. It can be stated that the results of this project have been widely exploited in order to improve the yield of the mackerel and thereby increase the profitability of that valuable species.

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Reports

Comparison of insulation of tanks with experiments and heat transfer models

Published:

01/04/2008

Authors:

Björn Margeirsson

Supported by:

Promens Dalvík ehf, Matís ohf

Comparison of insulation of tanks with experiments and heat transfer models

The aim of the project was to investigate the insulation value of three types of fish tanks. The pots were either insulated with polyethylene or polyurethane foam and of two sizes, 400 and 460 L. In two experiments, the temperature rise of water in the pots was monitored with a time with the initial temperature of the water approx. 4 ° C and ambient temperature approx. 18-20 ° C. The increase in temperature was also assessed using computerized heat transfer (CFD) models. The effect of forced airflow around the pot (forced heat transfer) was assessed by comparison with the heat condition in free heat transfer (in heat). The study showed that there is a considerable difference in the insulation of different pots and the pots came out differently depending on whether it was free or forced heat transfer. The results of measurements and heat transfer models for calm pots were well matched, but the model for wind pots needs to be improved. In further research into the insulation value of the pots, frozen fish should be used instead of water to further mimic the actual situation.

The aim of the project was to investigate the insulation capability of three types of fishing tubs. The tubs were either insulated with polyethylene or polyurethane foam and of two sizes; 400 and 460 L. In two experiments water temperature inside the tubs was monitored with initial water temperature ca. 4 ° C and ambient temperature ca. 18-20 ° C. The water temperature was also simulated in computational fluid dynamics models (CFD models). Influence of forcing air flow around the tubs (forced convection) was evaluated by comparison to free convection. Considerable difference was found between insulation capabilities of the different fishing tubs. Forced convection had different effects on different tub types. A good congruity was between experimental and CFD results for tubs in no wind, but some improvements should be done for the CFD model for tubs in wind (forced convection). In further research on insulation capability of the tubs iced fish should be used instead of water in order to resemble practical situations.

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