| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| 1.96 MB | Adobe PDF |
Authors
Abstract(s)
A presente dissertação tem como principal objetivo contribuir para o estudo do aumento da eficiência energética e melhoria do desempenho
térmico de câmaras frigoríficas utilizadas para conservação e armazenamento de produtos cárneos, vulgarmente utilizadas no setor agroindustrial. Neste âmbito, são abordadas várias temáticas relacionadas com eficiência energética, nomeadamente as diretrizes implementadas na
Europa com o intuito de melhorar a eficiência energética.
É desenvolvida uma análise experimental do desempenho térmico de uma câmara frigorífica na zona da Covilhã, verificando as condições externas e parâmetros de construção onde está inserida. É analisado todo o sistema de frio, nomeadamente o seu estado de conservação e modo de operação. No interior da câmara frigorífica é desenvolvido um estudo experimental, tendo-se em consideração o layout, desde a organização dos produtos a conservar até à disposição dos evaporadores, o procedimento de manuseamento dos produtos, e efectuada a medição da velocidade e
temperatura de insuflação do ar, da temperatura do ar no espaço refrigerado, e da temperatura das várias superfícies.
Também é considerado um modelo com geometria tridimensional da câmara frigorífica, simulado por Dinâmica de Fluidos Computacional (CFD),
em regime permanente, avaliando deste modo o escoamento do ar e a transferência de calor com mais detalhe.
Na construção dos modelos CFD foi necessário definir, um modelo físicomatemático
baseado nas equações da continuidade, da quantidade de movimento e da energia. A turbulência foi considerada através do modelo
de turbulência k-ε padrão.
Da comparação resultante entre os resultados numéricos e experimentais, apesar de haver uma ligeira desfasagem de resultados, o modelo é
validado. Deste modo, é desenvolvido um estudo paramétrico, que consiste na alteração das condições de fronteira no evaporador, pelo aumento do valor da temperatura do ar e redução do valor da velocidade do ar de
insuflação.
Da análise dos resultados numéricos do estudo paramétrico, prevê-se que o sistema de frio, para a carga de produtos definida pela análise
experimental, se encontra sobredimensionado, permitindo assim que a temperatura e velocidade de insuflação do ar sejam alteradas. Com esta
alteração, reduz-se o consumo energético do sistema mantendo um desempenho térmico similar e consequentemente garantindo a segurança
alimentar. Assim, prevê-se uma melhoria de eficiência energética, e uma consequente poupança de recursos ambientais, energéticos e financeiros.
The present dissertation has the main objective of contributing to the study of improving energy efficiency and thermal performance in cold rooms used for conservation and storage of meat products, commonly used in the agro industrial sector. Within this framework are addressed several issues related to energy efficiency, including the guidelines implemented in Europe in order to reach the goal of improving energy efficiency. An experimental analysis of the thermal performance of a cold room in the Covilhã region is developed, verifying its external conditions and construction parameters. The cooling system is analysed, including its conservation status and operation mode. Experimental tests are developed inside the cold room taking into account the layout, from the organization of products storage to the evaporators location and position, the procedure of handling the products, and it is performed the measurement of the discharge air velocity and temperature, air temperature in refrigerated environment, and temperature of the various surfaces. Also, it is developed a three-dimensional model of the cold room, simulated by Computational Fluid Dynamics (CFD), in steady state, allowing the detailed evaluation of the airflow and heat transfer. The setup of the CFD model required the definition of a physical-mathematical model based on the equations of continuity, momentum and energy. The turbulence was considered by standard k-ε turbulence model. From the comparison of numerical and experimental results, although there is a slight shift between results, the model was validated. Thus, a parametric study is developed, which consists in changing the boundary conditions value at the discharge grille of the evaporator. The air temperature value is increased while the air velocity value is reduced. From the analysis of the numerical results provided by the parametric study, it is predicted that the cold system, for product loading defined on the experimental analysis, is oversized, thus enabling the modification of the discharge air temperature and velocity. In this modification, the energy consumption is reduced maintaining similar thermal performance e consequently ensuring the food safety. Thus, it is predicted an improvement of the energy efficiency and a consequent savings of environmental resources, energy and financial resources.
The present dissertation has the main objective of contributing to the study of improving energy efficiency and thermal performance in cold rooms used for conservation and storage of meat products, commonly used in the agro industrial sector. Within this framework are addressed several issues related to energy efficiency, including the guidelines implemented in Europe in order to reach the goal of improving energy efficiency. An experimental analysis of the thermal performance of a cold room in the Covilhã region is developed, verifying its external conditions and construction parameters. The cooling system is analysed, including its conservation status and operation mode. Experimental tests are developed inside the cold room taking into account the layout, from the organization of products storage to the evaporators location and position, the procedure of handling the products, and it is performed the measurement of the discharge air velocity and temperature, air temperature in refrigerated environment, and temperature of the various surfaces. Also, it is developed a three-dimensional model of the cold room, simulated by Computational Fluid Dynamics (CFD), in steady state, allowing the detailed evaluation of the airflow and heat transfer. The setup of the CFD model required the definition of a physical-mathematical model based on the equations of continuity, momentum and energy. The turbulence was considered by standard k-ε turbulence model. From the comparison of numerical and experimental results, although there is a slight shift between results, the model was validated. Thus, a parametric study is developed, which consists in changing the boundary conditions value at the discharge grille of the evaporator. The air temperature value is increased while the air velocity value is reduced. From the analysis of the numerical results provided by the parametric study, it is predicted that the cold system, for product loading defined on the experimental analysis, is oversized, thus enabling the modification of the discharge air temperature and velocity. In this modification, the energy consumption is reduced maintaining similar thermal performance e consequently ensuring the food safety. Thus, it is predicted an improvement of the energy efficiency and a consequent savings of environmental resources, energy and financial resources.
Description
Keywords
Desempenho térmico Camâras frigoríficas Agroindústria Dinâmica de fluídos computacionais