Desempenho energético de liofilizador vertical para desidratação de filés de Tilápia do Nilo (Oreochromis niloticus)

Abstract

This study aims to evaluate the energy consumption performance of a vertical freezer for dehydrating Nile Tilapia fillets in a prototype vertical freeze dryer. Tilapia fillets were used for the tests of both studies if they did not have a precise classification in terms of mass and size. In study 1, a vertical freezer with a Blast Chiller 230L freezing tunnel was used with Freon R404A refrigerant. Based on the data obtained, the freezing cycle, performance and experimental tests were evaluated. Three batches of tilapia fillets were used, containing masses of 18.29 kg, 19.94 kg, and 21.38 kg, totaling the mass of the batch at 59.61 kg. The variations in power consumed in relation to the freezing cycle times were measured, as well as the variations in latent and sensible heat throughout the process. The behavior of the freezing cycle was evaluated at 2 different points in the vertical freezer. In study 2, the vertical freeze dryer, still in the prototype stage, was subjected to controlled tests inside a test chamber for a period of 432 hours. To evaluate energy consumption, different samples of tilapia fillets with initial masses of 1.5 kg, 2.5 kg, 3.5 kg, and 4.5 kg, totaling 48 kg, were subjected to dehydration. The freeze-drying process lasts 18, 24, 30 and 36 hours and measures the final masses, comparing their percentage weight loss in relation to the initial masses and the average consumption in W/h. Energy consumption and the estimated time needed to reach the level of 30.00% dry matter, considered ideal for dehydrating tilapia fillets according to Fellows (2006), were evaluated. A comparison was made between the energy consumption of an upright freezer for domestic use and the estimated energy consumption to freeze-dry the equivalent mass of tilapia fillets that can be stored and preserved in the upright freezer. As the main result of the comparative study, it was found that the estimated energy consumption for the freezedrying process would only have advantages after 0.96 years (350 days) of product storage, for the mass of the batch of tilapia fillets of 2 .5 kg subjected to freeze-drying. The worst result in the freeze-drying process is 1.67 years (611 days) for the batch of tilapia fillets with an initial mass of 1.5 kg, when compared to the vertical freezer. This comparison is only based on energy consumption, not considering other factors, such as lower mass and volume of freeze-dried fillets, storage area and maintenance of the upright freezer.