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Industrial refrigeration equipment companies are continuously looking for ways to optimise the design of chilling and freezing tunnels in order to minimise food quality loss and increase the energy efficiency of the equipment. However, possibilities for dedicated experimental tests of the industrial operations are limited due to a large amount of food product involved while the number of design variables to be considered is high. A cost-effective alternative to experiments is numerical modelling. The main goal of this research was to simulate heat transfer of packaged food products in a chilling and freezing tunnel. Computational fluid dynamics (CFD) models were developed to improve prediction in industrial cheese chilling and chicken freezing. The industrial cheese chilling model was developed based on six blocks of agar that mimic the product arrangement and airflow pattern of a cheese chiller; while the chicken freezing model represents the first case of a CFD freezing model where the geometry was derived empirically via computed tomography scan data. The model predictions were validated by experimental temperature histories generated as part of the study. Once validated, the model was used to investigate the cooling heterogeneity and the effect of different operating conditions on the processing time. In addition to the CFD model, a simple heat transfer simulation based on the one-dimensional finite difference method was developed for industrial users. Thermal property models in the literature were also reviewed to propose the most suitable choice for thermal processing calculations.

Forced-air cooling is a widely used pre-cooling process that enables the New Zealand horticultural industry, valued at over NZD $8B in 2016, to maintain the quality of perishable exports. In the typical systems used in New Zealand’s horticultural industry, forced-air cooling involves stacking fruit boxes into pallets, which are stacked together in a refrigerated room, and a fan is used to create a pressure drop through the pallets. This forces cold air through the packaging ventilation and over the fruit, facilitating heat transfer and rapidly cooling the product from the field heat (~20 °C) to the storage temperature (0-2 °C), thus prolonging shelf life and preserving fruit quality. Package design is linked with cooling performance, as the specifics of the ventilation (i.e. placement and size of vents in the boxes) results in different airflow patterns. Unfortunately, it is not well understood how to predict the performance of a hypothetical design, which is partly why in industry and academia there has been a focus on package design testing – where through experimental or computational means, the performance of a given design is thoroughly tested. Trial-and-error experimental work represents a steep materials cost, and construction and validation of detailed mathematical models can be a highly arduous and specialised task. It would therefore be beneficial to the New Zealand horticulture industry and academia to have a suite of methodologies that can simply and rapidly predict performance of a hypothetical package design. It was proposed that such methods are based upon mathematical modelling, with a focus on flexibility, computational efficiency, and automation. The goal is that such a model can be used to rapidly develop mathematical descriptions of a wide variety of products and cooling scenarios, and if integrated with optimisation routines, will allow swift iteration toward an optimised design.--Shortened abstract