Theoretical and experimental studies on boiling heat transfer for the zeotropic mixture R-407C
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Universidade Federal de Minas Gerais
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Tese de doutorado
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Membros da banca
Ricardo Nicolau Nassar Koury
Antonio Augusto Torres Maia
Carlos Umberto da Silva Lima
Antônio Carlos Lopes da Costa
Antonio Augusto Torres Maia
Carlos Umberto da Silva Lima
Antônio Carlos Lopes da Costa
Resumo
This work concerns theorical and experimental methods for understanding the heat transfer mechanisms for a zeotropic fluid, namely R-407C. The refrigerant R-407C is a mixture of three refrigerants, R-134a, R-32, and R-125, which may replace R-22 in future refrigerant systems. Due to the degradation of heat transfer coefficients in mixtures such as R-407C, the classical relations may overestimate the experimental heat transfer rates. A correction based on nucleate boiling suppression factors that corrects a previously proposed relation is used to minimize the degradation error. The newly proposed relation was developed through a robust methodology based on genetic algorithm (GA) optimization for three additional refrigerants R-404a, R134a and R-22. A discussion about inventory is also presented, where a modified Otaki method is proposed for the more realistic scenario that corresponds of not knowing a priori the heat transfer coefficient. The inventory obtained by the modified Otaki method is higher than the one obtained by the traditional Otaki method. Both methods yield accurate results for R-407C.
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Engenharia mecânica
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Engenharia Mecânica