Efeito de alterações de projeto no desempenho de um condicionador de ar em diferentes temperaturas externas

Abstract

The simulation of thermal cooling systems has been used in order to reduce the time and costs of developing new air conditioning systems, in addition to allowing a better understanding of the operation of the parameters of its components. In the present work, it was analyzed the influence of different constructive and operational parameters of a refrigeration system in the integrated COP, such as fan airflow, number of fins, number of circuits and number of tubes by row of the heat exchangers.. For this, the main components of a split-hiwall air conditioner with variable refrigerant flow were mathematically modeled using the EES (Engineering Equation Solver) software. The models were adjusted to approximate the maximum possible of the physical sample, based on data obtained in tests carried out in a psychrometric calorimeter. For the analyzes performed, the systems were simulated considering the conditions of the internal environment constant and changing the conditions of the external environment from 21 °C to 35 °C. Modified air conditioners were proposed, altering heat exchangers’ physical and operational aspects of the original equipment design so that the COP and the refrigeration capacity presented the same values of the original construction when operating under the nominal conditions. It was found that when the modifications in the equipment influenced only the values of global coefficient of heat transfer and area of heat exchange there were no changes in the value of integrated COP in relation to the original construction. It was verified that the parameter that most influenced in the integrated COP was the circuit of the heat exchangers of the system. There was a decrease in performance compared to the original construction for the equipment with less circuits. The modifications that obtained higher values of COP with the decrease of the external temperature were considering 3 circuits in the condenser and 4 circuits in the evaporator. Simulations were also performed for a rotation frequency of the 30 % lower compressor, where the main advantage was the decrease in the thermal capacity and the significant increase in the equipment performance coefficient, reaching an increase of 48.4 % in relation to the nominal condition. It was demonstrated that the design condition is not always the most representative to evaluate the performance of the equipment and allowed evaluations that can contribute to the decision making regarding the thermal parameters of operation and design.