Lincoln de Camargo Neves Filho

Estudo comparativo do resfriamento de laranja valência com ar forçado e com água

This work presents a study to compare the orange Valencia (Citrus sinensis O.) cooling with forced-air cooling and hydrocooling. The forced-air cooling system operated with air flow of 1933m3/h, at 1oC, RH= 88,4 ± 2,0% and air velocity around 1m/s. The experiments with immersion hydrocooling systems with capacity of 0,23m3 of water at 1oC, approximately. The half-cooling time and seven-eighths cooling time, they are determinate with the temperature data, made two repetitions. The results showed that the cooling the bed fruits, with air cooling, is not homogeneous, and obtained cooling time average, between 107min and 170min, depending on the position the fruit in the package. In the hydrocooling system, the cooling of the bed fruits happens uniformly in the bed, with average cooling time of 57min.

Avaliação de temperaturas em câmaras frigoríficas de transporte urbano de alimentos resfriados e congelados

The objective of this work was to monitor the operational conditions of the transport of chilled and frozen foods during delivery within cities and to evaluate the impact of the door openings on the alteration of the internal temperature of the refrigerated environment. Several temperature and pressure sensors were used in a refrigerated container with two compartments and they were installed in the refrigeration system unit and on the internal and external surfaces of the container. After the monitoring tests, it was verified that door openings during deliveries resulted in a disturbance that raised the internal temperature of the refrigerated container above values recommended for adequate conservation of the products transported. Moreover, increasing the number of door openings promoted a cumulative effect on the internal temperature, mainly in the chilled food compartment of the container. It was concluded that the refrigeration system unit presented serious limitations with regard to the maintenance of the containers internal temperature during the actual distribution routine, since it does not possess enough instantaneous capacity to restore the temperature set-point between deliveries.

Resfriamento de banana-prata com ar forçado

This work presents the cooling curves for bananas Prata, (Musa balbisiana Colla), and determinates half-cooling and seven-eight cooling times and the cooling rate. Bananas were kept in a cold room with a forced-air system at 7oC and RH = 87.6±3.8%. The experiment was conducted in a 2x2 factorial design, to test the effects of two flow rates (factors) of air passing through the product, and two types of boxes (levels). The statistical analysis was performed at p<0.10. The air flow rates were 1933 and 1160 m3/h and the boxes differed from each other by the area of openings, allowing more or less contact of the cooling media with the product (boxes with 40% or 3,5% of opening area). Significant differences were observed between cooling times of the product. The shortest cooling time was reached when the product was packed in a box with 40% of opening area and with the largest air flow rate of 1933 m3/h. The longest cooling time was obtained using a box with 3,2% of opening area and with the smallest air flow of 1160 m3/h. The results demonstrated the influence of the package opening area and the air flow on the cooling rate of bananas. The average time cooling was 117 min at 555 min in the different treatments. There is no statistical difference on weight loss.

Escoamento de ar através de embalagens de polapa de frutas em caixas comerciais: efeito sobre os perfis de velocidade em túneis de congelamento

The changes in air velocity, as a function of stacking of fruit pulp packages (100g), offering a resistance to air flow in commercial boxes were evaluated and the air flow rates estimated during blast freezing operations. Velocities were initially measured prior to passing the air through the multi-layer stacks of boxes in the chamber. Processing of the data was accomplished by applying a non-linear regression routine. Air flow rates were determined by numerical integration from adjusted air flow velocity profiles and appeared to be 10% higher than those obtained by the traditional procedure. Under constant operating conditions of the fan, the results for the 7-layer arrays of boxed products exhibited a 62% reduction in the flux of chilling air, in relation to the 3-layer arrays, and 50.9% decrease with respect to the 5-layer array. These values were directly proportional to the void space available for air flow.

Preliminary economic analysis of lettuce vacuum cooling system in Brazil

This paper presents an economic analyzes of a vacuum pre-cooling unit for lettuce in Brazil. The fixed and local operational costs were considered and the benefits derived from the investment were quantified considering the actual losses of horticultural products. The obtained results indicate a satisfactory period of return for the project (less than 1 year) although the investment is considered quite high.

FUZZY-PID CONTROLLER APPLIED TO A REFRIGERATION SYSTEM

A refrigeration system exhibits a dynamic behavior on which the variables are interdependent and subjected to oscillation, hence, implicating necessity of changes on operating conditions and undesirable energy expenses. These characteristics ratify the importance of adequate dimensioning and equipment selection to find pre-defined operating conditions such as, the maximum cooling capacity and the evaporating and condensing temperatures. The application of fuzzy control in industrial processes is growing fast in the last decades, mainly in processes whose first principle models require complex methods to be simulated. In these cases, the fuzzy controllers’ capacity of acting correctly based only on expert knowledge and on the capacity of inter-relating all the variables of the process are attractive features. This work presents the experimental development and evaluation of fuzzy-PID controllers for the maintenance of the evaporating temperature in a chiller. The system was submitted to load and set-point disturbances accomplishing an analysis based upon error parameters and transient response. The results showed that fuzzy controllers were adapted satisfactorily.

Processo de congelamento em túnel portátil com convecção forçada por exaustão e insuflação para paletes

The objective of this work is to build an experimental portable forced-air freezing tunnel which creates a low or high pressure region surrounding the product. Comparative studies with air exhausting and blowing were conducted. The tunnel was built and placed inside a freezing product storage chamber, and the objective was to improve the air circulation and the thermal distribution between the product and cold air for a sample batch left inside the chamber. A heat transfer analysis comparing the process and the air distribution around the product was performed. The air evacuation process reduced up to 14% of the freezing time in relation to the blowing system and 10% in relation to the mixed system.

Air blast freezing of fruit pulp models in commercial boxes: influence of preferential channels in the bed on freezing times estimating

Os tempos de congelamento da solucao modelo de polpas de frutas embaladas e acondicionadas em diferentes arranjos de camadas no interior das caixas do empilhamento foram avaliados sob varias condicoes de operacao encontradas nas praticas comerciais. Nestes tipos de processos, as caixas contem uma porosidade significativa e metodos para avaliar como esta afeta o tempo de congelamento, torna o problema de dificil resolucao. Procedimentos para as estimativas dos tempos de congelamento, usando modelos encontrados na literatura, foram comparados com medidas experimentais atraves da aquisicao de dados de tempo/temperatura. Os resultados mostraram que o escoamento do ar entre as embalagens e um parâmetro significativo nas estimativas dos tempos de congelamento. Quando e considerada a presenca de canais preferenciais, dependendo do metodo utilizado, estes valores sao subestimados em cerca de 10% quando comparados com os valores experimentais. As isotermas tracadas em funcao da localizacao das amostras no interior das caixas comprovam o deslocamento do centro termico, em relacao ao centro geometrico do produto.

Refrigerated container: an alternative for postharvest conservation

Refrigeration is an excellent method for storing horticultural fresh products such as fruits and vegetables. The use of refrigerated containers is a simple and ready-to-use technology allowing better quality and decreasing postharvest losses. In this work some experiments were conducted with a refrigerated container in two operating conditions: with and without load. The following variables were evaluated: air temperature, air velocity, air relative humidity, and pressure of the refrigeration system. The lettuce (Latuca sativa L.) half-cooling time was also determined when this product was stored at 1oC. It was observed that the container surfaces receiving more radiation presented temperature increases of 1,5 ± 1oC in contrast to the surfaces that were less exposed. Air speed ranged from 2.1; 1.7 and 0.3 m/s for the three studied surfaces. The lettuce half-cooling time varied from 530 min and 1.080 min, depending on the position of the head of lettuce in the container. The relative humidity of the air was 81-86% ± 1% in the empty container and 90-91 ± 1%, for the loaded container.