Experimental and numerical modelling comparison of thermal performance of expanded polystyrene and corrugated plastic packaging for fresh fish

Experiments were carried out to compare the thermal performance of wholesale fresh fish boxes made of corrugated plastic (CP) and expanded polystyrene (EPS). Free standing boxes containing whole, fresh fillets were exposed to dynamic thermal loads. The chilling effect of frozen ice packs was studied by including them in some of the boxes. The frozen ice packs proved efficient for protecting fresh fish fillets against temperature abuse. Further-more, the results show that the insulating performance of EPS is significantly better than were recorded inside the thermally abused boxes without ice packs, initially at 1.9 to 2.1 °C and stored for 6.1 h at a mean ambient temperature of 19.4 °C. The fish temperature distributions during thermal abuse were studied with a numerical model for both pack-aging types, applying effective thermal properties of the sandwich-structured CP box. The purpose of the model was to cost effectively improve the packaging design. A satisfactory agreement between numerical results and experimental results was obtained

Hermun hitastigsbreytinga í flutningi ferskra fiskafurða

Temperature control is a critical parameter to retard quality deterioration of perishable foodstuff, such as fresh fish, during distribution from processing to consumers. This thesis is aimed at analysing and improving the temperature management in fresh fish chill chains from processing to market by means of experiments and numerical heat transfer modelling. Ambient and product temperatures are mapped in real multi-modal distribution chains, which are both sea and air based. The results serve as a basis for simulation experiments, in which different packaging units and solutions are compared with respect to thermal insulation and product quality maintenance and more optimal ones are proposed. The experimental results are used to validate 3-D heat transfer models of fresh or superchilled whitefish, packaged in single boxes or multiple boxes assembled on a pallet, under thermal load. Much more severe temperature control problems are measured in air transport chains, especially in passenger airplanes, compared to sea transport. However, space for improvement in sea transport chains has also been discovered. The results underline the importance of precooling whitefish products before packaging for air freight and applying well distributed cooling packs inside the packaging. The results imply that product temperature differences of up to 10.5 °C can occur in a non-superchilled fresh fish pallet load and the storage life difference between the most and the least sensitive boxes on a full size pallet in a real air transport chain can exceed 1–1.5 days. It is demonstrated that even though a widely used expanded polystyrene (EPS) box design with sharp corners offers better thermal insulation than a corrugated plastic (CP) box, the sharp-corner design can be significantly improved. Such design improvement has been accomplished by developing a numerical heat transfer model in ANSYS FLUENT resulting in a new 5-kg EPS box currently manufactured by the largest EPS box manufacturer in Iceland. Other temperature-predictive models of products, developed and validated in this thesis, consider a cooling pack on top of superchilled cod packaged in two types of EPS boxes, compared to fresh fish packaged in a CP box without a cooling pack. Finally, models are developed for pallet loads of different sizes containing either chilled or superchilled fish. The models are used to confirm the temperature-maintaining effect of precooling and estimate the effect of pallet stack size. KEYWORDS: fish, temperature, heat transfer modelling, packaging, transport, precooling.AVS Rannsóknasjóður í sjávarútvegi, Tækniþróunarsjóður, Rannsóknasjóður Háskóla Ísland

Assessing the impact of policy changes in the Icelandic cod fishery using a hybrid simulation model

Most of the Icelandic cod is caught in bottom trawlers or longliners. These two fishing methods are fundamentally different and have different economic, environmental, and even social effects. In this paper we present a hybrid-simulation framework to assess the impact of changing the ratio between cod quota allocated to vessels with longlines and vessels with bottom trawls. It makes use of conventional bioeconomic models and discrete event modelling and provides a framework for simulating life cycle assessment (LCA) for a cod fishery. The model consists of two submodels, a system dynamics model describing the biological aspect of the fishery and a discrete event model for fishing activities. The model was run multiple times for different quota allocation scenarios and results are presented where different scenarios are presented in the three dimensions of sustainability: environmental, social, and economic. The optimal allocation strategy depends on weighing the three different factors. The results were encouraging first-steps towards a useful modelling method but the study would benefit greatly from better data on fishing activities