Experimental data on the solubility of CO2 in methyl methacrylate (MMA) and butyl methacrylate (BMA) are reported at temperatures from 308 to 333 K and pressures in the range of 1 to 10 MPa. The corresponding measurements of the volumetric expansion of the liquid phase are also presented. The solubility data are correlated with the Peng-Robinson equation of state using two interaction parameters. Solubilities of CO2 as high as 80 mol% can be attained in both monomers in the range of pressure considered. A near-linear relationship is observed between pressure and liquid-phase composition. The Peng-Robinson equation of state provides a satisfactory correlation of the solubility data. The average absolute relative deviations with respect to the calculated values of pressure are less than 2%. For a given monomer, the expansion isotherms coincide when plotted as a function of the liquid - phase composition. Catalytic chain transfer (CCT) polymerisation of CO2-expanded MMA, BMA and styrene is then described. Experimental values of the chain transfer constant are determined at 323 K and 333 K and in the range of pressure from 0.1 to 6 MPa. A cobaloxime complex is used as the chain transfer catalyst. The effect of small quantities of polymer on the volumetric expansion of the corresponding monomer is considered. The chain transfer constants for the expanded monomers are significantly higher than those obtained in the bulk monomers. It is demonstrated that a linear relationship exists between the chain transfer rate coefficient and the inverse of liquid-phase viscosity. These results provide significant evidence that the rate-determining step in the CCT process is diffusion-controlled. Finally, molecular weight evolution in CCT polymerization of CO2-expanded MMA is reported. Experimental molecular weight and polydispersity index data are presented at 323 K in the range of conversion from 1 to 25%, and at pressures of 5 and 6 MPa. Both molecular weight and polydispersity increase with conversion at conditions below the homogeneous expansion limit. Predici simulations suggest that either irreversible catalyst deactivation or cobalt-carbon bond formation is the most likely mechanism for the increase in molecular weight with conversion.

[pt] O setor da refrigeração possui um papel essencial e crescente na economia global, com um aumento na quantidade de sistemas operantes. A necessidade de desenvolver novos refrigerantes tem sido cada vez mais frequente, a fim de atender a legislações ambientais cada vez mais rigorosas. Igualmente, medidas envolvendo a introdução de novos materiais, como os nanofluidos, tem sido uma constante. Neste trabalho, um sistema de refrigeração usando uma mistura nanolubrificante POE-diamante e refrigerante R410A foi simulado. Dados experimentais cedidos pela Universidade Federal de Uberlândia (UFU) foram usados para a elaboração e validação do modelo. O simulador utiliza a equação de Peng-Robinson para o cálculo das propriedades termodinâmicas e o método de fronteira móvel para a modelagem dos trocadores. O impacto das nanopartículas em relação aos parâmetros críticos foi avaliado a partir do princípio do isomorfismo e da natureza de ambos os materiais: fluido base e nanopartículas. A convergência da simulação do ciclo de refrigeração foi obtida com o método do simplex modificado, que mostrou-se adequado para tal aplicação, apresentando convergência satisfatória em todos os casos. As temperaturas de evaporação, condensação e de descarga do compressor são obtidas a partir das condições de operação do compressor, dos dois fluidos de transferência de calor, do grau de superaquecimento no evaporador e também do grau de subresfriamento no condensador. Superfícies de resposta foram criadas a fim de avaliar o efeito de cada uma das variáveis (temperatura de evaporação, frequência do compressor e concentração de nanopartículas) utilizadas no estudo do coeficiente de performance (COP), da capacidade frigorífica e da potência do compressor. A temperatura de evaporação possui um impacto significativo sobre a capacidades frigorífica e o COP, enquanto que a potência é mais afetada pela frequência do compressor. A concentração de nanopartículas, apesar de possuir um efeito marginal, não deve ser desprezada, devido à modificação que causa sobre as propriedades termofísicas da mistura. / [en] The refrigeration sector has an essential and growing role in the global economy, with an increase in the number of operating systems. The need to develop new refrigerants has been increasingly frequent, in order to meet increasingly stringent environmental legislation. Equally, measures involving the introduction of new materials, such as nanofluids, have been a constant. In this work, a cooling system using a POE-diamond nanolubricant mixture and R410A refrigerant was simulated. Experimental data provided by the Federal University of Uberlândia (UFU) were used for the elaboration and validation of the model. The simulation uses the Peng-Robinson equation to calculate thermodynamic properties and the moving-boundary method for modeling the heat exchangers. The impact of the nanoparticles in relation to critical parameters was evaluated based on the principle of isomorphism and the nature of both materials: base fluid and nanoparticles. The convergence of the refrigeration cycle simulation was obtained with the modified simplex method, which proved to be adequate for such application, presenting satisfactory convergence in all cases. Evaporation,condensation and discharge temperatures are obtained from the operating conditions of compressor and both heat transfer fluids, the degree of superheating in the evaporator and also the degree of subcooling in the condenser. Response surfaces were created in order to evaluate the effect of each of the variables (evaporation temperature, compressor frequency and nanoparticle concentration) used in the study of the performance coefficient (COP), refrigeration capacity and compressor power. Results have shown that the evaporation temperature has a significant impact on the cooling capacity and the COP, while the power is mainly affected by the compressor frequency. The nanoparticles concentration, despite having a more attenuated effect, should not be neglected, due to the change it causes to the mixture thermophysical properties.