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Abstract(s)
O constante e elevado crescimento da população a nível mundial põe em causa a sustentabilidade do planeta. Estima-se que no ano 2050 a população mundial atinja os 9,1 bilhões, sendo assim necessário um incremento na ordem dos 70% da produção alimentar de forma a sustentar o aumento populacional. A redução das perdas na fase de pós colheita é importante. Como um dos principais fatores que influenciam o tempo de vida das frutas e vegetais é a temperatura torna-se imperativo arrefecer estes o mais rapidamente possível após a sua colheita. O rápido arrefecimento de F&V na fase de pós-colheita é denominado de pré-arrefecimento, consistindo na rápida remoção do calor de campo dos produtos de forma a retardar os seus processos fisiológicos e assim estender o seu tempo de vida, preservando-os em quantidade e qualidade. A refrigeração de F&V tem sido constante alvo de estudo ao longo do tempo, sendo do máximo interesse o estudo de quanto tempo demoram os produtos a serem arrefecidos até à sua temperatura de armazenamento. A temperatura de armazenamento é denominada de Tempo de Sete Oitavos de Arrefecimento. De forma caracterizar os processos de arrefecimento das F&V verifica-se uma crescente utilização de software de simulação e modelação computacional. Na presente dissertação, com o intuito de caracterizar o processo de arrefecimento do pêssego na fase de pós-colheita, recorreu-se à ferramenta computacional COMSOL Multiphysics com o objetivo de modelar um empacotamento de pêssegos e estudar o seu processo de arrefecimento. Assim, foram primeiramente obtidos dados experimentais relativos à variação de temperatura ao longo do tempo de dois lotes distintos, arrefecidos a ar e a água, de forma a validar um modelo computacional produzido no COMSOL Multiphysics que descrevesse a variação da temperatura ao longo do tempo dos dois lotes de pêssego para ambas situações de arrefecimento. Recorrendo-se ao COMSOL Multiphysics foram realizados estudos paramétricos de modo a avaliar a influencia no tempo de arrefecimento de F&V de parâmetros como dimensão física; temperatura inicial e temperatura de escoamento não perturbado. O estudo paramétrico foi realizado para situações de arrefecimento em ar e em água.
The constant and high population growth endangers the sustainability of the planet. It is estimated that by 2050 the world population will reach 9.1 billion, thus there is a need for a increase of around 70% of the food production in order to sustain the population growth. The reduction of losses in the postharvest phase is important so that there are readily available food products without the excessive exploitation of additional natural resources to support the increase in population. Because temperature is one of the most influential factors that influence the shelf life of fruits and vegetables it is imperative to cool them as fast as possible after their harvest. The rapid cooling of fruit and vegetable products in the post-harvest stage is denominated pre-cooling. Pre-cooling consists in the rapid removal of the field heat from the products in order to slow-down their physiological processes and thus extend its life, in order to preserve them in quantity and quality. The cooling of perishable products has been subject of study in order to determine how long it takes for the products to be cooled to their storage temperature. The storage temperature is commonly referred to as seven-eighths of cooling time, this corresponds to the cooling of the products to 0,125 temperature in the dimensionless form. In order to characterize the cooling processes of F&V there has been a growth in the use of computer modeling and simulation software. With the aim of characterizing the peach cooling process in the post-harvest stage, COMSOL Multiphysics ® was used in order to model a packed layer of peaches. Thus, it was first modeled and validated a model that represented the variation of temperature over time of two batches of peaches subjected to air cooling and hydrocooling. Subsequently, using COMSOL Multiphysics’ ® capabilities to perform parametric studies, relevant parameters that influence the cooling time of F&V products such as dimensions, initial produce temperature and fluid temperature were changed with the intention to study its effect on the cooling time. The parametric study was conducted considering both air-cooling and hydrocooling.
The constant and high population growth endangers the sustainability of the planet. It is estimated that by 2050 the world population will reach 9.1 billion, thus there is a need for a increase of around 70% of the food production in order to sustain the population growth. The reduction of losses in the postharvest phase is important so that there are readily available food products without the excessive exploitation of additional natural resources to support the increase in population. Because temperature is one of the most influential factors that influence the shelf life of fruits and vegetables it is imperative to cool them as fast as possible after their harvest. The rapid cooling of fruit and vegetable products in the post-harvest stage is denominated pre-cooling. Pre-cooling consists in the rapid removal of the field heat from the products in order to slow-down their physiological processes and thus extend its life, in order to preserve them in quantity and quality. The cooling of perishable products has been subject of study in order to determine how long it takes for the products to be cooled to their storage temperature. The storage temperature is commonly referred to as seven-eighths of cooling time, this corresponds to the cooling of the products to 0,125 temperature in the dimensionless form. In order to characterize the cooling processes of F&V there has been a growth in the use of computer modeling and simulation software. With the aim of characterizing the peach cooling process in the post-harvest stage, COMSOL Multiphysics ® was used in order to model a packed layer of peaches. Thus, it was first modeled and validated a model that represented the variation of temperature over time of two batches of peaches subjected to air cooling and hydrocooling. Subsequently, using COMSOL Multiphysics’ ® capabilities to perform parametric studies, relevant parameters that influence the cooling time of F&V products such as dimensions, initial produce temperature and fluid temperature were changed with the intention to study its effect on the cooling time. The parametric study was conducted considering both air-cooling and hydrocooling.
Description
Keywords
Modelação Computacional Pêssego Pós-Colheita Pré-Arrefecimento Produtos Perecíveis