DYNAMIC MODEL FOR AN EVAPORATOR OPERATING WITH R- 1234yf AND R- 134a

Thiago Ali¹; Willian Duarte¹; Philippe Haberschil²; Antônio Maia¹; Luiz Machado¹

¹ Programa de Pós Graduação em Engenharia Mecânica (PPGMEC) da Universidade Federal de Minas Gerais; ² Centre d'Energétique et Thérmique de l'INSA de Lyon (CETHIL)

doi:10.20906/CPS/CILAMCE2015-0614

Resumo

Due to the environmental deterioration, as the global warming and destruction of the ozone layer, the production and trade of CFCs fluids have been regulated since 1987, when the Montreal Protocol was signed. Since then, the refrigeration industry develops researches in fluids with characteristics favorable to the environment. In recent years, the fluid R-1234yf (low levels of ODP and GWP) has been used to replace the traditional fluid R-134a in automotive air conditioning systems in Europe and USA. This paper presents a mathematical model of a evaporator of refrigeration machine operating with the fluids R-134a and R-1234yf. The model is based at the principles of conservation of energy, mass, and linear-momentum, and literature correlations are used to calculate the heat transfer, pressure drop, and void fraction to the flow of the fluid. To validate the model, 36 tests were carried out with a testing bank operating with the fluid R-134a, in which the compressor speed was varied systematically and the evaporation temperature and mass flow rate of the fluid were measured. The results obtained with the model were satisfactory when compared with the experimental results. Furthermore, operation simulations of the evaporator were carried out to compare the behavior of the system operating with the fluids R-134a and R-1234yf.

Palavras-chave: Environment; R-1234yf; R-134a; Evaporator; Model