Research Project: New generation of nanoporous organic and hybrid aerogels for industrial applications: from the lab to pilot scale production
Loading...
Contributors
Funders
ID
EC.00084
Authors
Erkey, Can
Faculty Member
Publications
Determination of composition of ethanol-CO2 mixtures at high pressures using frequency response of microcantilevers
(Elsevier, 2018) Alaca, Burhanettin Erdem; Baloch, Shadi Khan; Erkey, Can; Kiraz, Alper; Jonas, Alexandr; Department of Mechanical Engineering; Department of Physics; Department of Chemical and Biological Engineering; KUTEM (Koç University Tüpraş Energy Center); KUYTAM (Koç University Surface Science and Technology Center); Department of Electrical and Electronics Engineering; Yes; College of Engineering; College of Sciences; Research Center
The measurement of the composition of ethanol-CO2 mixtures at high pressures is important in many applications involving supercritical fluids such as drying of alcogels or release of MEMs. Resonant frequency and quality factor (Q-factor) of microcantilevers immersed in ethanol-CO2 mixtures were measured at a temperature of 308 K and pressure range from 8 MPa to 22 MPa. The measurements were carried out for different mixture compositions ranging from 0.91 to 6.16 wt% of ethanol in CO2. At a given pressure and temperature, the resonant frequencies were found to decrease linearly with the increasing ethanol weight percent in the mixture. The sensitivity of the resonant frequency to changes in composition was found to increase with decreasing pressure. The experimental results show that ethanol-CO2 mixture composition can be determined with good accuracy using mainly the measured resonant frequency of microcantilevers.
Sensitivity of compositional measurement of high-pressure fluid mixtures using microcantilever frequency response
(Elsevier, 2018) Alaca, Burhanettin Erdem; Baloch, Shadi Khan; Erkey, Can; Kiraz, Alper; Jonas, Alexandr; Department of Mechanical Engineering; Department of Physics; Department of Chemical and Biological Engineering; KUTEM (Koç University Tüpraş Energy Center); KUYTAM (Koç University Surface Science and Technology Center); Yes; College of Engineering; College of Sciences; Research Center
Frequency response of an oscillating microcantilever immersed in a fluid mixture can be used to determine the composition of the mixture over a wide range of temperatures and pressures. The Limit of Detection (LOD) in such measurements carried out at high pressures is of great interest for monitoring technologically important processes such as supercritical drying of aerogels. We studied compositional measurement sensitivity of cantilevers defined as the derivative of the cantilever resonant frequency or quality factor with respect to the fluid mixture composition. On the basis of Sader's model of hydrodynamic interaction of an oscillating immersed cantilever with the surrounding fluid, we derived analytical expressions for the sensitivity that were found to be complex functions of the density and viscosity of the mixture as well as the length, width, thickness, and density of the cantilever. We measured the frequency response of cantilevers immersed in ethanol-CO2 mixtures containing 0 - 0.04 wt fraction of ethanol at 318 K and within the pressure range 10-21 MPa. Using the measured resonant frequency and quality factor together with previously published density and viscosity data for ethanol-CO2 mixtures of various compositions, we calculated the sensitivity at each pressure and temperature and determined the LOD of the measurement. In particular, with our current setup, the LOD ranged from 0.0009 to 0.0071 wt fraction of ethanol in the mixture in the pressure range 10-21 MPa for a 150 mu m long cantilever. Our results convincingly illustrate the potential of miniature cantilever-based probes for fast and sensitive in-situ detection of the composition of fluid mixtures in practical technological processes carried out at high pressures.
Kinetics of supercritical drying of gels
(Multidisciplinary Digital Publishing Institute (MDPI), 2018) Erkey, Can; İnönü, Zeynep; Özbakır, Yaprak; Şahin, İbrahim; Ülker, Zeynep; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; Yes; College of Engineering; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING
Supercritical drying of gels is considered as the most important step of aerogel production since it enables preservation of the three-dimensional pore structure which lead to unique material properties such as high porosity, low density, and large surface area. An understanding of the kinetics of supercritical drying is necessary to provide insight into material development, scale-up, and optimization of the aerogel manufacturing process. Thus, investigation of supercritical drying is gaining increased attention in recent years. This review paper covers the experimental considerations and techniques to study the kinetics of supercritical drying, fundamental mass transfer mechanisms during the drying process and modeling efforts to predict the drying kinetics for varying operating conditions and gel properties. Transport phenomena involving diffusion, convection, spillage by volume expansion, and axial dispersion are discussed by providing the fundamental equations and empirical correlations to predict transfer coefficients. A detailed review of literature covering experimental and theoretical studies on kinetics of supercritical drying is presented.
Investigation of kinetics of supercritical drying of alginate alcogel particles
(Elsevier, 2019) Erkey, Can; Şahin, İbrahim; Uzunlar, Erdal; Department of Chemical and Biological Engineering; Yes; College of Engineering
Spherical calcium alginate gel particles were synthesized by dripping method. The effects of temperature, pressure, particle size and CO2 flow rate on kinetics of supercritical drying of alginate gel particles in a packed bed were investigated. Increase in CO2 flow rate, increase in temperature and decrease in particle size increased the drying rate and decreased the drying time. A mathematical model based on (i) the diffusion of the solvent inside the pores of gel particles, (ii) external mass transfer of the solvent from the surface of the gel particles into the flowing fluid stream, and (iii) convection and axial dispersion of the solvent in the flowing fluid stream was developed. A correlation for predicting external mass transfer coefficients for supercritical drying of alcogel particles was developed by fitting the model to experimental data. A good agreement between the experimental data and model results was achieved using the developed correlation.
