ATAC i system - Energimyndigheten

2002-02-22
2. New model proposed based on the abundant experimental data of the nitrogenwater
and oxygen-water systems.
3. Verification of the new model by comparing the calculation results with the
available experimental data and those calculated with other models.
4. Preparation of experiment including the laboratory locations and equipment.
Prefer making the experiment abroad with the existing equipment.
Within the whole period of project, a Lic or PhD (with more time) is planned to be
finished.
Uppnådda resultat (Results):
1. Experimental data and calculation methods evaluation (Paper I):
In the literature study, comprehensive experimental data and property calculation
methods for the air-water system have been surveyed. Due to the lack of the
experimental data at elevated temperature, it becomes important to investigate
evaluation of the different calculation methods. A method with a common basis for
calculating the thermodynamic properties of the air-water system by using three types
of models (an ideal model, an ideal mixing model and a real model) was developed.
The results have been compared to find the appropriate model with its accuracy of
reliable temperature and pressure. Following conclusions were made from the
literature survey:
Experimental data of the air-water system are meager, the temperatures are below
75°C. Furthermore, most of them are enhancement factors. For enthalpy, no
experimental data for the air-water mixture has been determined. Thus new
experimental data at high temperature are needed.
The ideal and ideal mixing models can be used to calculate saturated vapor
composition when the pressure is less than 10 bar and the temperature is higher
than 280 K. For the calculation of enthalpy, the deviation between these two
models is very high. It implies that the consideration of the non-ideal of the pure
species may cause a large difference between enthalpy calculations. Meanwhile,
the vapor composition has a large effect on the enthalpy calculation results.
All existing real models are based on the virial equation in which the parameters
are correlated from experimental data or estimated from theory. For the air-water
system, the available experimental data are only valid up to 75 °C, therefore, the
reliability of the real models at high temperatures cannot be considered. Careful
extrapolation is required.
Experimental data for the nitrogen-water and oxygen-water systems are abundant.
Furthermore, properties of air are similar to those of the nitrogen-oxygen mixture.
It might be a "short-cut" for developing models for the air-water system at
elevated temperature and pressure by using the experimental data of nitrogenwater
and oxygen-water systems.
2. New model and the verification (Papers II-V):
A new thermodynamic model was proposed in which the dry air was assumed to be
the mixture of nitrogen and oxygen with the mole fractions of 0.7812 and 0.2188,
respectively. Fugacity coefficients were calculated with the modified Redlich-Kwong
equation of state. The dissolved gas followed Henry’s law and activity coefficients of