Simulation physical packages

A number of design calculations require a knowledge of thermodynamic properties and phase equilibrium. In practice, the designer most often uses a commercial physical property or a simulation software package to access such data. However, the designer must understand the basis of the methods for thermodynamic properties and phase equilibrium, so that the most appropriate methods can be chosen and their limitations fully understood. 

To calculate the enthalpy of liquid or gas at temperature T and pressure P, the enthalpy departure function (Equation 4.78) is evaluated from an equation of state2. The ideal gas enthalpy is calculated at temperature T from Equation 4.81. The enthalpy departure is then added to the ideal gas enthalpy to obtain the required enthalpy. Note that the enthalpy departure function calculated from Equation 4.78 will have a negative value. This is illustrated in Figure 4.9. The calculations are complex and usually carried out using physical property or simulation software packages. However, it is important to understand the basis of the calculations and their limitations. 

The aim of this chapter is to offer practical guidance on how to choose the appropriate technique for a particular physical problem, how to set up a simulation, and how to analyze and visualize the output. In addition it should provide the theoretical background required to become a competent user of the available simulation software packages. 

Huber, T., Kruger, R, van Gunsteren, W. F. (1999). The GROMOS biomolecular simulation program package. The Journal of Physical Chemistry A, 103, 3596-3607. 

The NURESIM (Nuclear Reactor Simulation) software package was also developed by the Institute of Nuclear Science and Technique, Hanoi, (Research Contract No. VIE/5304) in order to provide users a set of tools for training on ftmdamentals of reactor theories, as well as for performing reactor calculations. The project Windows User-Friendly Code Package Development for Operation of Research Reactors is a continuation of the project NURESIM Lectures on Reactor Physics which is attached to this report. 

In a preliminary study, Tomasula et al. (2009) simulated the fluid milk process to identify energy usage and GHGs associated with HTST pasteurization and the related unit operations, such as homogenization. Physical property data for milk and cream were provided to the simulator. Packaging was not included as part of the simulation. GHGs were... 

Fortunately — and not unfortunately — no one model exists as yet which simulates all of the physical, chemical, and biological processes associated with pollutant fate in soils. We say fortunately, because such a package would be very data intensive and difficult to use. Intensive research is required to accomplish the above objective and the value of the overall product may be questioned by users. Section 7.0 presents selected models. 

Driscoll, D. F., Ling, P. R., and Bistrian, B. R. (2007), Physical stability of 20% lipid injectable emulsions via simulated syringe infusion effects of glass versus plastic product packaging, J. Parenteral Enteral Nutr., 31(2), 148-153. 

Computer simulation can also be used for relief sizing (see Annex 4). This may be the only safe alternative in cases where physical properties are non-ideal, multiple reactions occur or there are significant continuing.feed streams or external heating. It will be necessary to choose a computer simulation package which can handle multi-component mixtures comprising both volatile and permanent gas components. 

The mathematical description considered in Section 2.3 and Appendix A was used as a modeling basis for the specially developed completely rate-based simulator DESIGNER (155). This tool consists of several blocks, including model libraries for physical properties, mass and heat transfer, reaction kinetics, and equilibrium, as well as a specific hybrid solver and thermodynamic package. 

Basically, DESIGNER can use different physical property packages that are easy to interchange with commercial flowsheet simulators. For the case considered, the vapor-liquid equilibrium description is based on the UNIQUAC model. The liquid-phase binary diffusivities are determined using the method of Tyn and Calus (see Ref. 72) for the diluted mixtures, corrected by the Vignes equation (57), to account for finite concentrations. The vapor-phase diffusion coefficients are assumed constant. The reaction kinetics parameters taken from Ref. 202 are implemented directly in the DESIGNER code. 

Finally, in some of the most widely used classical models - the free-volume models of Fujita, Vrentas and Duda and their alternatives (171-175) - more than a dozen structural and physical parameters are needed to calculate the free-volume in the penetrant polymer system and subsequently the D. This might prove to be a relatively simple task for simple gases and some organic vapors, but not for the non-volatile organic substances (rest-monomers, additives, stabilizers, fillers, plasticizers) which are typical for polymers used in the packaging sector. As suggested indirectly in (17) sometimes in the future it will maybe possible to calculate all the free-volume parameters of a classical model by using MD computer simulations of the penetrant polymer system. 

---