Dimensionamento da área de troca térmica de um trocador de calor duplo tubo para um sistema de aspersão de meias-carcaças bovinas

Abstract

Heat exchangers are widely used equipment in industries, with various models and designs available, making the selection of the correct configuration to meet the required demand often a challenging task. The refrigeration industry is a scenario where this equipment is essential, including for systems that spray half-carcasses of cattle. This study aims to size the heat transfer area of a double-tube heat exchanger to meet the needs of a spray system for half-carcasses of cattle. Data were obtained from an existing refrigeration scenario currently in operation, which includes a spray system designed to serve three cooling chambers. Additionally, the heat transfer area will be sized for two additional water flow rates collected from two refrigeration plants: 2.9 m³/h and 25 m³/h, to compare configurations for the heat exchanger. Subsequently, water flow rates will be simulated in 3 m³/h intervals, ranging from 3 m³/h to 25 m³/h, to analyze the results of the overall heat transfer coefficient, heat transfer area, and effectiveness. To meet the initially proposed water flow rate of 16 m³/h, the refrigerant fluid R-134a volumetric flow rate was calculated as 6.06 m³/h. A configuration of a double-tube heat exchanger with five columns and eight tubes per column (5x8) and an effective length of 5.9 meters per tube was determined to achieve a heat transfer area of 46.47 m². For a water flow rate of 2.9 m³/h, maintaining the effective tube length, a configuration with four columns and eight tubes per column (4x8) was required, achieving the necessary heat transfer area of 36.88 m². For a flow rate of 25 m³/h, a configuration with six columns (five with eight tubes and one with three tubes, 5x8, 1x3) was used to achieve a heat transfer area of 49.75 m². In addition, water flow rates of 3, 6, 9, 12, 15, 18, 21, and 24 m³/h were tested, keeping the same geometric parameters. The behavior of the heat transfer area, overall heat transfer coefficient, and heat exchanger effectiveness was analyzed. The required heat transfer area ranged from 37 to 49.44 m², the overall heat transfer coefficient from 151.66 to 907.94 W/m²·K, and the effectiveness remained constant at 0.8. The heat transfer area results were close, as the temperatures did not change. The overall heat transfer coefficient values showed greater variation since all variables required for the calculation were affected. Only the effectiveness remained constant, as the required temperatures stayed the same, and the results varied proportionally in the same magnitude. [resumo fornecido pelo autor]