Corresponding States Method for Estimation of Upper Flammability Limit Temperature of Chemical Compounds
The accuracy and predictability of predictive methods to determine the flammability characteristics of chemical compounds are of drastic significance in the chemical industry. This work aims at continuing application of the gene expression programming (GEP) mathematical strategy to modify the existing thermophysical properties correlations available in the literature to pursue the following objectives: optimization of the number of independent parameters, amplification of the generality, and improvement of the accuracy and predictability. This work deals with presenting a simple corresponding states model to predict the upper flammability limit temperature of 1462 organic compounds from 76 chemical families. The parameters of the correlation include the critical temperature and the acentric factor of the compounds. The obtained statistical parameters including average absolute relative deviation of the results from DIPPR 801 database values (1.7, 1.8, 1.7% for training, optimization, and prediction sets, ...
Development of a general model for determination of thermal conductivity of liquid chemical compounds at atmospheric pressure
Farhad Gharagheizi, Poorandokht Ilani-Kashkouli, and Mehdi SattariThermodynamics Research Unit, School of Engineering, University of KwaZulu-Natal, Howard College Campus,King George V Avenue, Durban 4041, South AfricaAmir H. MohammadiMINES ParisTech, CEP/TEP, Centre E´nerge´tique et Proce´de´s, 35 Rue Saint Honore´, 77305 Fontainebleau, FranceThermodynamics Research Unit, School of Engineering, University of KwaZulu-Natal, Howard College Campus,King George V Avenue, Durban 4041, South AfricaDeresh RamjugernathThermodynamics Research Unit, School of Engineering, University of KwaZulu-Natal, Howard College Campus,King George V Avenue, Durban 4041, South AfricaDominique RichonTechnical University of Denmark, Center for Energy Resources Engineering (CERE), Dept. of Chemical andBiochemical Engineering, DK-2800 Kgs. Lyngby, DenmarkThermodynamics Research Unit, School of Engineering, University of KwaZulu-Natal, Howard College Campus,King George V Avenue, Durban 4041, South AfricaDOI 10.1002/aic.13938Published online November 9, 2012 in Wiley Online Library (wileyonlinelibrary.com).In this communication, a general model for representation/presentation of the liquid thermal conductivity of chemicalcompounds (mostly organic) at 1 atm pressure for temperatures below normal boiling point and at saturation pressure fortemperatures above the normal boiling point is developed using the Gene Expression Programming algorithm.Approximately 19,000 liquid thermal conductivity data at different temperatures related to 1636 chemical compoundscollected from the DIPPR 801 database are used to obtain the model as well as to assess its predictive capability. Theparameters of the model comprise temperature, acentric factor, critical pressure, normal boiling temperature, andmolecular weight. Nearly 80% of the data set (15,221 data) is randomly assigned to develop the model equation, 10% of thedata set (1902 data) is used to validate the model, and the remaining data (1902 data) were implemented to evaluate itspredictive power. The average absolute relative deviation of the model results from the DIPPR 801 data is less than 9%. Interms of simplicity and wide range of applicability, this empirical model shows acceptable accuracy.
Submicron polymer structures with X-ray lithography and hot embossing
This article describes the process chain for replication of submicron structures with varying aspect ratios (AR) up to 6 in polymethylmethacrylate (PMMA) by hot embossing to show the capability of the entire LIGA process to fabricate structures with these dimensions. Therefore a 4.7 μm thick layer of MicroChem 950k PMMA A11 resist was spin-coated on a 2.3 μm Ti/TiOx membrane. It was patterned with X-ray lithography at the electron storage ring ANKA (2.5 GeV and λc ≈ 0.4 nm) at a dose of 4 kJ/cm3 using a Si3N4 membrane mask with 2 μm thick gold-absorbers. The samples were developed in GG/BDG and resulted in AR of 6–14. Subsequent nickel plating at 52°C resulted in a 200 μm thick nickel tool of 100 mm diameter, which was used to replicate slit-nozzles and columns in PMMA. Closely packed submicron cavities with AR 6 in the nickel shim were filled to 60% during hot embossing.