Modelo dinâmico para um evaporador operando com R-1234yf e R134a

• Ano de defesa: 2018
• Autor(a) principal: Thiago Ali Resende Lauar
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Meio ambiente; R-1234yf; R-134a; Evaporador; Modelo matemático; Evaporadores; Modelos matemáticos; Engenharia mecânica
• Link de acesso: http://hdl.handle.net/1843/BUOS-B4KMKS

Currently, hydrofluoroleophins (HFOs) have been used more in refrigeration processes because they have low ozone depletion potential (ODP) and low global warming potential (GWP). With the emergence of restrictions such as the European Directive 2006/40 / EC and EU No. 517/2014, refrigerants with GWP above 150, such as R-134a, are now subject to study for substitution. In this context, a numerical model was developed for a coaxial evaporator of a refrigerating machine to simulate the behavior of the system operating with R-134a and its possible substitute, R-1234yf. Experimental tests were performed for the validation of the developed model and comparative simulations between R-134a and R-1234yf refrigerants were performed applying the model to determine the behavior of the evaporator in a steady-state and unsteady. Among the results obtained, it should be noted that in the worst cases the model was able to predict the water outlet temperature with a maximum error of 1,9 °C and the inlet and outlet temperature of the refrigerant with a maximum error of 1,8 e 1.6 °C, respectively. For the unsteady-state the simulations showed that the mass of refrigerant required for R-1234yf operation was lower than that of R-134a. It was also observed that the time constant of R-1234yf (12s) was practically the same as that of R-134a (13s) when the evaporator was subjected to a step in the inlet mass flow. Such proximity may be linked to the similarities between the thermodynamic properties of the two fluids