Avaliação da aplicabilidade de modelos híbridos na simulação computacional de válvulas de compressores de refrigeração
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Data
2016-08-30
Autores
Dias, Allan Demétrio Sales de Lima [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Na atualidade, um compressor precisa ter elevada eficiência para ser competitivo no mercado. Como o escoamento de refrigerante nas válvulas é uma das maiores fontes de perdas termodinâmicas, melhorias no seu projeto podem aumentar significativamente a eficiência do compressor. Simular computacionalmente válvulas de compressores utilizando modelos tridimensionais completos, além de computacionalmente caro, demanda muito tempo e, por essa razão, pesquisadores buscam metodologias simplificadas para realizar a tarefa de predizer a dinâmica das válvulas. Aqui avaliamos a aplicabilidade de um modelo híbrido para simular computacionalmente o comportamento dinâmico de um modelo frequentemente usado como válvula de sucção. Neste modelo, resolvemos o problema do escoamento tridimensional em regime transiente pela válvula aplicando o método de volumes finitos para escoamento compressível e isotérmico e a dinâmica da válvula usando um modelo massa-mola-amortecedor com um grau de liberdade. Comparamos os resultados do modelo híbrido com aqueles obtidos de um modelo tridimensional completo para a estrutura da válvula usando como parâmetros o tempo de processamento, deslocamento da válvula, força sobre a válvula e distribuições de pressão e de velocidade do escoamento. Validamos os modelos numéricos com resultados experimentais. A boa concordância entre os resultados indicam que a redução de tempo obtida pelo modelo híbrido é pequena (15% em média) e não justifica seu uso.
Currently, a refrigeration compressor must have high efficiency in order to become competitive in the market. Since the refrigerant flow through the valves is one of the largest sources of thermodynamic losses, improvements in their design can significantly increase the compressor efficiency. Computational simulations of compressors valves using - complete three-dimensional models, besides computationally expensive, is time consuming. For this reason, researchers always look for simplified methodologies for predicting the valves dynamics. Here, we evaluate the applicability of a hybrid model to computationally simulate the dynamics of a model frequently used as suction valve. In this model, we solve the problem of the three-dimensional unsteady flow through the valve by applying the finite volume method for compressible and isothermal flow and the dynamics of the valve by using a mass-spring-damper model with one degree of freedom. We compare the results from the hybrid model with those obtained with a complete three-dimensional model for the structure using as parameters the processing time, valve displacement, force acting on the valve, and pressure and velocity fields of the flow. We validate the numerical models with experimental data. The good agreement between the results indicates that the reduction of the processing time obtained by using the hybrid model is small (15% in average) and does not justify its use.
Currently, a refrigeration compressor must have high efficiency in order to become competitive in the market. Since the refrigerant flow through the valves is one of the largest sources of thermodynamic losses, improvements in their design can significantly increase the compressor efficiency. Computational simulations of compressors valves using - complete three-dimensional models, besides computationally expensive, is time consuming. For this reason, researchers always look for simplified methodologies for predicting the valves dynamics. Here, we evaluate the applicability of a hybrid model to computationally simulate the dynamics of a model frequently used as suction valve. In this model, we solve the problem of the three-dimensional unsteady flow through the valve by applying the finite volume method for compressible and isothermal flow and the dynamics of the valve by using a mass-spring-damper model with one degree of freedom. We compare the results from the hybrid model with those obtained with a complete three-dimensional model for the structure using as parameters the processing time, valve displacement, force acting on the valve, and pressure and velocity fields of the flow. We validate the numerical models with experimental data. The good agreement between the results indicates that the reduction of the processing time obtained by using the hybrid model is small (15% in average) and does not justify its use.
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Palavras-chave
Simulação numérica, Válvulas de compressores, Modelos Híbridos, Engenharia mecânica, Numerical simulation, Compressor’s valve, Hybrid models