Date of Award
Master of Science in Chemical Engineering - (M.S.)
Chemical Engineering, Chemistry and Environmental Science
Edward Charles Roche, Jr.
Dana E. Knox
John E. McCormick
Chemical process simulation programs have become an indispensable tool to chemical engineers in the preparation of heat and material balances, and energy conservation studies. Since the 1960's several dozen process simulators have been developed which are in use today within companies and through computer service bureaus. Due to advances in the areas of unit operation analysis and thermodynamic relations, these programs require periodic modification. This thesis describes the programming modifications made to the Chemical Engineering Simulation System (CHESS) version 2.0, computer program. This undertaking was considered warranted since no improvements have been made to CHESS since its release in 1971. The objective is to produce a version which is more useful to practicing engineers and students than version 2.0.
Many features of CHESS were found to be inferior to other simulators such as ChemShare's DESIGN II and SimSci's PROCESS which are considered by many as the industrial standards. The identified deficiencies are (1) lack of an extensive thermodynamics package, (2) simplified treatment of unit operations, (3) components restricted to hydrocarbons, (4) maximum of 20 components per stream, and (5) brief output.
The following improvements to CHESS have been made, Producing version 2.1:
- A new equipment module, COMP, has been added to simulate the operation of a single stage gas compressor. The outlet conditions and power requirement are determined to increase the pressure of a gas stream. The adiabatic and mechanical efficiencies are included in the calculation of power requirement. Multi-stage compressors must be handled as individual stages in series. This new module replaces the compression calculations in the PUMP module which was inflexible and gave incorrect results.
- PUMP module has been modified to strictly handle the simulation of liquid pumping. The outlet conditions and power requirement to increase the pressure of a liquid stream are determined. The mechanical efficiency of the pump is included in the power requirement. The energy requirement is added to the feed enthalpy to determine the outlet temperature.
- The Fahrenheit temperature scale is now used in input/output data, replacing Rankine.
- Petroleum fraction components may be defined by the user. CHESS will automatically calculate all the necessary physical constants from boiling point, density and molecular weight information supplied in the input data. The capability to define non-standard, user defined components has been retained.
- An additional summary of the mass rates (lbs/hr) of the components in each stream will be printed at the end of the simulation.
- A summary of seventeen properties including viscosity, thermal conductivity and density for each stream will be printed at the end of the simulation.
- Heat release curves (temperature v.s. enthalpy) for specified temperature and pressure limits can be calculated for a maximum of five streams in the simulation.
Use of version 2.1 of CHESS provides more useful and practical information about the process and additional simulation capabilities than version 2.0. Compressors and pumps may now be simulated in a more realistic manner using the new COMP and PUMP modules. The calculation of heating/cooling curves provides useful information for the design of heat exchangers (e.g., reboilers and condensers). The stream properties summary provides all the necessary physical properties for equipment design and specification. In addition, the specification of petroleum fraction components in the input data has been simplified.
It is recommended that further improvements be made to CHESS in the areas of unit operations and thermodynamics in future work.
Zvolensky, Thomas, "Improving the capabilities of the chemical engineering simulation system (CHESS) computer program" (1985). Theses. 2088.