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Papers by Eugenia Teodora Iacob Tudose

Research paper thumbnail of Laboratory Configurations for PCM-TES Materials: A Review

Journal of advanced thermal science research, Sep 26, 2022

The global energy crisis and the negative impact on the environment of the existing technologies ... more The global energy crisis and the negative impact on the environment of the existing technologies have constrained researchers to capture several types of waste energy using different technologies and materials. For heat, energy harvesting technologies include a major source, the sun, and as an effective storage media, phase change materials. The current review covers experimental laboratory configurations used for thermal energy storage (TES), mainly with phase change materials as working fluids. The required characteristics of PCM-TES materials are covered. Geometric configurations, starting with simple shell-and-tube heat exchanger (HX), other multiple constructive alternatives, plate HX, and also modular HX or fixed and fluidized beds systems are overviewed in order to concentrate on heat transfer characteristics important for TES systems operation and optimization. Emphasis falls on important constructive characteristics for thermal performance, such as the heat charge and discharge rates, within specific temperature ranges, depending on the type of TES fluid used, the energy storage capacity, or density. The advantages and disadvantages of each constructive piece of equipment are critically reviewed. Some comparisons among designs are also included, with an accent on beneficial alterations to improve thermal features.

Research paper thumbnail of Wool and Leather Waste Materials with Thermo-Insulating Properties

Revista de Chimie

Seven new different thermo-insulating materials based on wool and /or skin wastes were obtained. ... more Seven new different thermo-insulating materials based on wool and /or skin wastes were obtained. To emphasize this capability, the effective thermal diffusivities were determined at a material moisture content of 10%, in a temperature range of 10 to 40oC. Depending on the material composition, the results showed that the effective thermal diffusivity varies between the limits of 6E-8 and 8.5E-8 m2/s. The smallest values were obtained for the untreated wool and for the material obtained from both untreated wool and finished leather powder. The obtained values underline the fact that the investigated materials can be used to obtain composites with good thermo-insulating properties.

Research paper thumbnail of Textile Wastewater Treatment on a Spinning Disc Reactor: Characteristics, Performances, and Empirical Modeling

Applied Sciences

Spinning disc (SD) technology has been successfully applied, for the first time, in real textile ... more Spinning disc (SD) technology has been successfully applied, for the first time, in real textile wastewater treatment with no other additional processing. The SD efficiency was investigated using real textile effluents to study the color and suspended solids removals at different effluent-supplying flowrates (10–30 L/h) and different disc rotational speeds (100–1500 rpm) with good experimental results; thus, it can minimize the polluting loads within a short time period. Furthermore, within this study, process modeling and its classical optimization were applied to SD technology for wastewater treatment. The experiments were organized according to an active central composite rotatable 23 order design, considering as independent variables the wastewater flowrate, rotational speed, and operating time and, as optimization criteria, the suspended solids removal and discoloration degree. Overall, this novel study proved that the SD technology applied in textile effluent treatment is a su...

Research paper thumbnail of Mass Transfer in Solid-Liquid Extraction at High Solute Concentrations

Environmental Engineering and Management Journal

The solid-liquid extraction process and some of its influencing factors such as solid-liquid rati... more The solid-liquid extraction process and some of its influencing factors such as solid-liquid ratio, temperature and salt initial amount have been investigated. Also, mathematical modeling for mass transfer coefficients calculation was applied. An inert porous solid material (coal), impregnated with 10% and 20% mass NaCl or 15% and 30% mass CaCl2, was used. The leaching was conducted in a fixed bed column, in laminar flow. The CaCl2 impregnated samples were investigated in a column with a height/diameter ratio of 2.5, at 20ºC, 30ºC, and 40ºC and the NaCl samples, in a 4.16 height/diameter ratio column, at 30ºC, 40ºC, 50ºC, 60ºC. In both cases, liquid flow rates of 3.8 L/h, 7 L/h, 10.6 L/h, 13.3 L/h were used. An increase of the extraction degree with the washing liquid flow rate (up to 10.6 L/h) indicated that the solid-liquid ratio is a crucial factor. Temperature increase has a positive influence on the extraction degree. At the beginning of the process, the salt quantity extracted from the high salt amount sample, using the lowest water flow rate has a similar value to the one extracted from the low salt amount sample, using the highest flow rate. At larger time values (t > 500 s), the extraction degree dependence on the liquid flow rate is similar for the high and low salt samples. Based on the proposed mathematical model, mean time mass transfer coefficient values kꞏa were calculated and compared to the experimental obtained data.

Research paper thumbnail of Adsorption Equilibrium and Effective Diffusivity in Cylindrical Alumina Particles Impregnated with Calcium Chloride

Environmental Engineering and Management Journal

Adsorption equilibrium and effective diffusion coefficients of water vapor, in cylindrical partic... more Adsorption equilibrium and effective diffusion coefficients of water vapor, in cylindrical particles of activated alumina (A) and activated alumina impregnated with calcium chloride (MCA), are experimentally determined. The experiments were conducted at 303 K and 323 K using cylindrical particles with 2.5 mm in both length and diameter. Diffusion coefficients were determined from the kinetics of water sorption. The measurements were conducted in a constant pressure unit based on a magnetic suspension balance (Rubotherm) under isothermal conditions. The sorption capacity depends on temperature and it was found to be higher by 25 % for the MCA material compared with the A material. The water diffusion coefficient depends itself on the adsorption equilibrium taking into account the local slope of the water sorption isotherm. The effective diffusivity of water is almost 2 times lower in impregnated than in non-impregnated alumina. The obtained diffusion data could be used to model the dynamic adsorption.

Research paper thumbnail of Free Surface Deformation in Oscillatory Thermocapillary Convection in a Rectangular Cavity

Proceeding of International Heat Transfer Conference 12

Research paper thumbnail of Surface temperature patterns in thermocapillary convection in a rectangular cavity – an experimental study

Research paper thumbnail of Mass transfer acompanied by chemical reaction at sublimation

Hungarian Journal of Industrial Chemistry

ABSTRACT

Research paper thumbnail of Axial Dispersion Study in Fixed Bed Columns

Revista de Chimie -Bucharest- Original Edition-

Fixed bed columns are often used in chemical engineering industry in physical operations (such as... more Fixed bed columns are often used in chemical engineering industry in physical operations (such as absorption, leaching, rectification) and in two-or threephase chemical operations. Fluid flow in such equipment induces axial mixing (dispersion) which can be quantified using the axial dispersion coefficient. Besides the axial dispersion, radial liquid dispersion occurs, the latter one being however less intensive.

Research paper thumbnail of On the modeling of solid materials drying in fixed beds.I. Drying with a thermal gas agent

Research paper thumbnail of Effective wood diffusion coefficients

Cellulose Chemistry and Technology

Research paper thumbnail of Spinning disc reactor technology for environmental chemical processing design and environmental application

Research paper thumbnail of An experimental study of oscillatory, thermocapillary convection in a rectangular cavity

Research paper thumbnail of Slug flow-radial displacement in the Taylor bubble acceleration mechanism

Research paper thumbnail of Studiul influentei excentricitatii bulei Taylor asupra vitezei de deplasare in curgerea bifazica de tip slug

Revista de Chimie -Bucharest- Original Edition-

Research paper thumbnail of An experimental investigation of the onset of oscillations in thermocapillary-buoyant flows in a rectangular cavity

Research paper thumbnail of An experimental study of thermocapillary convection in a thin horizontal liquid layer in a rectangular cavity under normal gravity with and without controlled vibration

Research paper thumbnail of Slug flow experiments and computer simulation of slug length distribution in vertical pipes

Research paper thumbnail of Investigation of flow structures in vertical slug flow

Nuclear Engineering and Design, 1997

The flow structure of gas-liquid slug flow in a vertical tube has been investigated experimentall... more The flow structure of gas-liquid slug flow in a vertical tube has been investigated experimentally and numerically. A photochromic dye activation method was used to obtain two-dimensional liquid velocity profiles around a Taylor Bubble rising in stagnant kerosene in a vertical 25.6 mm I.D. pipe. A numerical simulation of the flow was conducted using a Volume-of-Fluid approach to predict both the shape of the Taylor Bubble and the velocity profiles in the liquid phase. In order to test the hypothesis that a trailing bubble can accelerate, catch up and coalesce with a leading bubble because of lateral motion and reduced drag force, a second experiment was performed using a solid Taylor Bubble placed in a steady downward flow of liquid. The measured drag force showed significant reduction as the bubble was moved from the tube axis towards the wall, giving support to the hypothesis. © 1997 Elsevier Science S.A.

Research paper thumbnail of Hydrodynamics and mass transfer coefficients for a modified Raschig ring packed column

Heat and Mass Transfer, 2014

ABSTRACT The pressure drop, the liquid holdup, as well as the liquid film mass transfer coefficie... more ABSTRACT The pressure drop, the liquid holdup, as well as the liquid film mass transfer coefficients (kL) for a modified Raschig packing, with turbulence promoters, used in absorption columns, were determined experimentally. The aim of this work is to verify the improved mass transfer properties of this new packing for the randomly and, particularly, for the arranged packed columns. The experiments were performed at gas velocities ranging from 800 to 2,000 m h-1 and liquid velocities scaling between 2.5 and 8.11 m h-1, ranges that cover most of the absorption column operation conditions. Experimental data and correlations for the pressure drop, the liquid holdup and the gas– liquid mass transfer coefficients (kL) for modified Raschig ring packed columns are presented. The influence of the gas and the liquid velocities on the column hydrodynamics and the mass transfer coefficients have been obtained experimentally and also, have been compared with literature data.

Research paper thumbnail of Laboratory Configurations for PCM-TES Materials: A Review

Journal of advanced thermal science research, Sep 26, 2022

The global energy crisis and the negative impact on the environment of the existing technologies ... more The global energy crisis and the negative impact on the environment of the existing technologies have constrained researchers to capture several types of waste energy using different technologies and materials. For heat, energy harvesting technologies include a major source, the sun, and as an effective storage media, phase change materials. The current review covers experimental laboratory configurations used for thermal energy storage (TES), mainly with phase change materials as working fluids. The required characteristics of PCM-TES materials are covered. Geometric configurations, starting with simple shell-and-tube heat exchanger (HX), other multiple constructive alternatives, plate HX, and also modular HX or fixed and fluidized beds systems are overviewed in order to concentrate on heat transfer characteristics important for TES systems operation and optimization. Emphasis falls on important constructive characteristics for thermal performance, such as the heat charge and discharge rates, within specific temperature ranges, depending on the type of TES fluid used, the energy storage capacity, or density. The advantages and disadvantages of each constructive piece of equipment are critically reviewed. Some comparisons among designs are also included, with an accent on beneficial alterations to improve thermal features.

Research paper thumbnail of Wool and Leather Waste Materials with Thermo-Insulating Properties

Revista de Chimie

Seven new different thermo-insulating materials based on wool and /or skin wastes were obtained. ... more Seven new different thermo-insulating materials based on wool and /or skin wastes were obtained. To emphasize this capability, the effective thermal diffusivities were determined at a material moisture content of 10%, in a temperature range of 10 to 40oC. Depending on the material composition, the results showed that the effective thermal diffusivity varies between the limits of 6E-8 and 8.5E-8 m2/s. The smallest values were obtained for the untreated wool and for the material obtained from both untreated wool and finished leather powder. The obtained values underline the fact that the investigated materials can be used to obtain composites with good thermo-insulating properties.

Research paper thumbnail of Textile Wastewater Treatment on a Spinning Disc Reactor: Characteristics, Performances, and Empirical Modeling

Applied Sciences

Spinning disc (SD) technology has been successfully applied, for the first time, in real textile ... more Spinning disc (SD) technology has been successfully applied, for the first time, in real textile wastewater treatment with no other additional processing. The SD efficiency was investigated using real textile effluents to study the color and suspended solids removals at different effluent-supplying flowrates (10–30 L/h) and different disc rotational speeds (100–1500 rpm) with good experimental results; thus, it can minimize the polluting loads within a short time period. Furthermore, within this study, process modeling and its classical optimization were applied to SD technology for wastewater treatment. The experiments were organized according to an active central composite rotatable 23 order design, considering as independent variables the wastewater flowrate, rotational speed, and operating time and, as optimization criteria, the suspended solids removal and discoloration degree. Overall, this novel study proved that the SD technology applied in textile effluent treatment is a su...

Research paper thumbnail of Mass Transfer in Solid-Liquid Extraction at High Solute Concentrations

Environmental Engineering and Management Journal

The solid-liquid extraction process and some of its influencing factors such as solid-liquid rati... more The solid-liquid extraction process and some of its influencing factors such as solid-liquid ratio, temperature and salt initial amount have been investigated. Also, mathematical modeling for mass transfer coefficients calculation was applied. An inert porous solid material (coal), impregnated with 10% and 20% mass NaCl or 15% and 30% mass CaCl2, was used. The leaching was conducted in a fixed bed column, in laminar flow. The CaCl2 impregnated samples were investigated in a column with a height/diameter ratio of 2.5, at 20ºC, 30ºC, and 40ºC and the NaCl samples, in a 4.16 height/diameter ratio column, at 30ºC, 40ºC, 50ºC, 60ºC. In both cases, liquid flow rates of 3.8 L/h, 7 L/h, 10.6 L/h, 13.3 L/h were used. An increase of the extraction degree with the washing liquid flow rate (up to 10.6 L/h) indicated that the solid-liquid ratio is a crucial factor. Temperature increase has a positive influence on the extraction degree. At the beginning of the process, the salt quantity extracted from the high salt amount sample, using the lowest water flow rate has a similar value to the one extracted from the low salt amount sample, using the highest flow rate. At larger time values (t > 500 s), the extraction degree dependence on the liquid flow rate is similar for the high and low salt samples. Based on the proposed mathematical model, mean time mass transfer coefficient values kꞏa were calculated and compared to the experimental obtained data.

Research paper thumbnail of Adsorption Equilibrium and Effective Diffusivity in Cylindrical Alumina Particles Impregnated with Calcium Chloride

Environmental Engineering and Management Journal

Adsorption equilibrium and effective diffusion coefficients of water vapor, in cylindrical partic... more Adsorption equilibrium and effective diffusion coefficients of water vapor, in cylindrical particles of activated alumina (A) and activated alumina impregnated with calcium chloride (MCA), are experimentally determined. The experiments were conducted at 303 K and 323 K using cylindrical particles with 2.5 mm in both length and diameter. Diffusion coefficients were determined from the kinetics of water sorption. The measurements were conducted in a constant pressure unit based on a magnetic suspension balance (Rubotherm) under isothermal conditions. The sorption capacity depends on temperature and it was found to be higher by 25 % for the MCA material compared with the A material. The water diffusion coefficient depends itself on the adsorption equilibrium taking into account the local slope of the water sorption isotherm. The effective diffusivity of water is almost 2 times lower in impregnated than in non-impregnated alumina. The obtained diffusion data could be used to model the dynamic adsorption.

Research paper thumbnail of Free Surface Deformation in Oscillatory Thermocapillary Convection in a Rectangular Cavity

Proceeding of International Heat Transfer Conference 12

Research paper thumbnail of Surface temperature patterns in thermocapillary convection in a rectangular cavity – an experimental study

Research paper thumbnail of Mass transfer acompanied by chemical reaction at sublimation

Hungarian Journal of Industrial Chemistry

ABSTRACT

Research paper thumbnail of Axial Dispersion Study in Fixed Bed Columns

Revista de Chimie -Bucharest- Original Edition-

Fixed bed columns are often used in chemical engineering industry in physical operations (such as... more Fixed bed columns are often used in chemical engineering industry in physical operations (such as absorption, leaching, rectification) and in two-or threephase chemical operations. Fluid flow in such equipment induces axial mixing (dispersion) which can be quantified using the axial dispersion coefficient. Besides the axial dispersion, radial liquid dispersion occurs, the latter one being however less intensive.

Research paper thumbnail of On the modeling of solid materials drying in fixed beds.I. Drying with a thermal gas agent

Research paper thumbnail of Effective wood diffusion coefficients

Cellulose Chemistry and Technology

Research paper thumbnail of Spinning disc reactor technology for environmental chemical processing design and environmental application

Research paper thumbnail of An experimental study of oscillatory, thermocapillary convection in a rectangular cavity

Research paper thumbnail of Slug flow-radial displacement in the Taylor bubble acceleration mechanism

Research paper thumbnail of Studiul influentei excentricitatii bulei Taylor asupra vitezei de deplasare in curgerea bifazica de tip slug

Revista de Chimie -Bucharest- Original Edition-

Research paper thumbnail of An experimental investigation of the onset of oscillations in thermocapillary-buoyant flows in a rectangular cavity

Research paper thumbnail of An experimental study of thermocapillary convection in a thin horizontal liquid layer in a rectangular cavity under normal gravity with and without controlled vibration

Research paper thumbnail of Slug flow experiments and computer simulation of slug length distribution in vertical pipes

Research paper thumbnail of Investigation of flow structures in vertical slug flow

Nuclear Engineering and Design, 1997

The flow structure of gas-liquid slug flow in a vertical tube has been investigated experimentall... more The flow structure of gas-liquid slug flow in a vertical tube has been investigated experimentally and numerically. A photochromic dye activation method was used to obtain two-dimensional liquid velocity profiles around a Taylor Bubble rising in stagnant kerosene in a vertical 25.6 mm I.D. pipe. A numerical simulation of the flow was conducted using a Volume-of-Fluid approach to predict both the shape of the Taylor Bubble and the velocity profiles in the liquid phase. In order to test the hypothesis that a trailing bubble can accelerate, catch up and coalesce with a leading bubble because of lateral motion and reduced drag force, a second experiment was performed using a solid Taylor Bubble placed in a steady downward flow of liquid. The measured drag force showed significant reduction as the bubble was moved from the tube axis towards the wall, giving support to the hypothesis. © 1997 Elsevier Science S.A.

Research paper thumbnail of Hydrodynamics and mass transfer coefficients for a modified Raschig ring packed column

Heat and Mass Transfer, 2014

ABSTRACT The pressure drop, the liquid holdup, as well as the liquid film mass transfer coefficie... more ABSTRACT The pressure drop, the liquid holdup, as well as the liquid film mass transfer coefficients (kL) for a modified Raschig packing, with turbulence promoters, used in absorption columns, were determined experimentally. The aim of this work is to verify the improved mass transfer properties of this new packing for the randomly and, particularly, for the arranged packed columns. The experiments were performed at gas velocities ranging from 800 to 2,000 m h-1 and liquid velocities scaling between 2.5 and 8.11 m h-1, ranges that cover most of the absorption column operation conditions. Experimental data and correlations for the pressure drop, the liquid holdup and the gas– liquid mass transfer coefficients (kL) for modified Raschig ring packed columns are presented. The influence of the gas and the liquid velocities on the column hydrodynamics and the mass transfer coefficients have been obtained experimentally and also, have been compared with literature data.