Perpustakaan Digital ITB

New Helmholtz equations of state for environmental-friendly refrigerants of R-600 (n-butane) and R-600a (isobutane) have been developed based on newly available and reliable experimental data with taking consideration on the theoretical background. The thermodynamic property models for the fluids were previously developed by some researchers. These models still have some drawbacks. Various experimental thermodynamic properties consist of ppT property and caloric properties were selected through literature survey and introduced to develop the models. Ancillary equations for saturation properties were firstly established with specified structural forms to prepare input data at saturation. Consistency to the intermolecular potential theory has been investigated by the behavior of the second and third virial coefficients. Further assessment was made for the behavior of the so-called ideal curves. The new fundamental equations of states for R-600 and R-600a are relatively short and they are in better agreement with more recent available measurements than other existing accurate equations of state. The models are based on the International Temperature Scale 1990 (ITS-90). Second and third virial coefficients, PVT and caloric surfaces, and ideal curves derived from the new equations of state behave reasonably. The estimated uncertainties of the new fundamental equations of state are 0.02% in ideal-gas isobaric specific heat, 0.2% in density, 0.15 to 0.2% in pressure in vapor phase, 1% in heat capacities, 0.15 to 0.2% in vapor-pressure, 0.05% in saturated-liquid density, 0.02% and around 1% in speed of sound in gaseous and liquid phase, respectively.