Glycol Aqueous Solution Research Articles

Conformational Composition of Ethylene Glycol in Aqueous Solutions and on Metal Substrates

In this work, we studied the Raman spectra of ethylene glycol (EG) and its aqueous solutions, as well as the spectra of ethylene glycol solutions deposited on a metal substrate prepared by laser ablation. Scattering was excited by laser radiation with wavelengths of 532 nm and 785 nm. It was found that the Raman spectra of EG are similar to the spectra of aqueous solutions of EG and to the spectra of EG solutions on a metal substrate, which may indicate the stability of the conformational composition of EG upon dissolution and drying on a structured metal substrate.

INVESTIGATION OF THE HEAT CAPACITIES OF NANOFLUIDS BASED ON NANOPARTICLES OF Al2O3, TiO2 AND CuO BY THE ADDITIVE METHOD

This study investigates the thermal properties of nanofluids, with a particular focus on their heat capacity when various nanoparticles are integrated into a base fluid. Nanofluids, which are composed of nanoparticles dispersed within a base fluid, are of significant interest due to their enhanced thermal characteristics compared to traditional fluids. The research employs the additive method, a widely used technique for estimating the effective heat capacity of nanofluids. This method posits that the total heat capacity of a nanofluid can be approximated by summing the contributions of each component according to its volume or mass fraction. This research represents the effect of nanopartilces concentration (1wt.%, 3 wt.%, 5 wt.%) on effective heat capacity of TiO2 based nanofluid. The analysis reveals that key factors influencing the heat capacity of a nanofluid, as determined by the additive method, include the heat capacities of the individual components and the concentration of the nanoparticles. Specifically, the greater the disparity in heat capacities between the base fluid and the nanoparticles, and the higher the nanoparticle concentration, the more the nanofluid's heat capacity shifts toward that of the nanoparticles. The calculations in this study indicate that the most significant decrease in heat capacity occurs in a nanofluid containing 5 wt.% Al2O3 nanoparticles with water as the base fluid. Conversely, the smallest reduction is observed in a nanofluid with 1 wt.% Al2O3 nanoparticles in a 50% aqueous ethylene glycol solution.

Raman analysis of aqueous solutions of ethylene glycol and 1,3-propylene glycol: Fundamental and applied aspects

Aqueous solutions of glycols, on the one hand, are widely used in many applications; on the other hand, they can serve as simple and representative models for studying intra- and intermolecular hydrogen bonds. In this work, we analyze the possibilities and limitations of Raman spectroscopy for fundamental and applied researches of such solutions on the examples of ethylene glycol (EG) and 1,3-propylene glycol (1,3-PG). It is shown that Raman spectroscopy is an effective tool for monitoring temporal changes in the structure of glycol solutions deposited on substrates. This study demonstrates that the water content in the solutions on the substrates decreases rapidly with time, and the rate of this decrease depends on the chemical structure of both glycol and substrate. It was found that the reduction in the water content leads to slight decrease in the contents of gauche-conformers in the backbones of EG and 1,3-PG molecules. It is shown that use of the 1064 nm excitation ensures a reliable Raman analysis of automotive antifreezes containing various dyes, in particular determination of the relative contents of water and glycol.

Effect of operating variables on isopropanol absorbed by triethylene glycol solution and discussions on the mass transfer coefficient predicted by artificial neural network

The mass transfer performance of isopropanol (IPA) absorption by triethylene glycol (TEG) aqueous solution in a spray-bed absorber was investigated, and the mass transfer coefficients predicted by an artificial neural network (ANN) and response surface methodology were compared in this study. The operating variables affecting the mass transfer performance of a spray-bed absorber include the gas and TEG fluxes, concentration of IPA, concentration of TEG aqueous solution, and operating temperature. The experimental results demonstrated that the mass transfer coefficient of a spray-bed absorber increased with increases in gas and liquid fluxes and decreased with increases in concentration of IPA. The Back-Propagation algorithm in the ANN model was selected to predict the mass transfer coefficients of the spray–bed absorption system. Hidden layers with 2, 4 and 6 neurons respectively were set to analyze the effect of the number of neurons on the target value, and then different transfer functions were used to compare the accuracy in predicting mass transfer coefficient. Finally, the influences of the number of hidden layers and different learning rules on the prediction of mass transfer coefficients were examined. The simulated results showed that the average error of the ANN using the TanhAxon transfer function, the Conjugate Gradient learning rule, two hidden layers, and 6 neurons in each hidden layer was within 1%. The results not only verified the successful establishment of the experimental device but also proved the accurate prediction of mass transfer coefficients by the ANN model.

Experimental investigation on spray cooling heat transfer properties of ethylene glycol-water-based nanofluids

Abstract Spray cooling is a practical solution for high heat flux heat dissipation problems. The spray cooling experiment was conducted with 50wt% ethylene glycol aqueous solution as the base liquid in this paper. The effects of the concentrations of copper nanoparticles, copper oxide nanoparticles, silica nanoparticles and surfactant Tween-20 on the heat transfer characteristics during spray cooling were investigated. The results showed that adding nanoparticles within a certain concentration range could enhance the effectiveness of spray cooling's heat transmission. Under the same conditions, adding copper nanoparticle has the best effect, followed by copper oxide nanoparticle, and silica nanoparticle has relatively poor effect. Among them, the heat transfer coefficient and heat flux of the nanofluid could be raised by 10.58% and 11.34% in comparison to the base liquid when the concentration of copper nanoparticles was 0.01wt%. As the concentration of nanoparticles rises higher, spray cooling's ability to transfer heat is hampered. Adding the surfactant Tween-20 could effectively improve the copper-water-ethylene glycol nanofluid's capacity for heat transmission. When the concentration is 3ppm, the heat transfer coefficient and heat flux of the nanofluid with Tween-20 were increased by 9.81% and 10.38% compared to the copper-water-ethylene glycol nanofluid.

Structural and dynamic behaviour of concentrated aqueous solutions of (poly)ethylene glycols: Insight into the impact of hydrophobicity, hydrogen bonding and chain length

Understanding the delicate interplay between hydrophobicity/hydrophilicity, hydrogen bonding ability and solute size in modulating the chemico-physical properties of aqueous solutions with increasing solute concentration is a challenging task. Here, we focus on how bulk properties, such as diffusion and aggregation behaviour, are affected by the different hydration patterns observed for differently concentrated aqueous solutions of (poly)ethylene glycols, and their corresponding methoxyethers, of various lengths. Using a combined experimental and computational approach, we analyse solutions of ethylene glycol (EG), dimethoxyethane (DME), polyethylene glycol with 4 repeating units capped with either hydroxyl (PEG200) or methoxyl (PEG250DME) tails, and polyethylene glycol with 9 repeating units (PEG400). By disentangling the contributions of hydrophobicity, hydrogen bonding ability, and chain length, we observe that for the smaller solutes electristriction and hydrophobic hydration are the main phenomena occurring. Instead, as the solute becomes larger, these effects give way to the non-trivial conformational flexibility that can either favour or disfavour intermolecular interactions which lead to the formation of water-rich regions excluded from the solute.

Macroporous hydrogel prepared via aqueous polymerization induced phase separation toward in situ immobilization of yeast

AbstractYeast‐loaded open‐cell macroporous poly(acrylamide) (PAM) hydrogels are prepared by polymerization induced phase separation (PIPS) with potassium persulfate (KPS)‐yeast as a redox initiator in a polyethylene glycol (PEG) aqueous solution. The presence of PEG not only allows the sizes of both void and interconnected pores of the hydrogels controllable, but also enlarges the void. Which makes it possible to embed cells in situ and efficiently transport nutrients inside the hydrogels. Yeasts are herein used to form a redox pair with KPS to run the polymerization of acrylamide (AM) at a mild temperature (less than 31°C), avoiding the cell inactivation during the polymerization. The in situ immobilization causes a uniformly distribution and high immobilization rate (~100%) of yeasts in the hydrogels. The hydrogels are then used to ferment glucose to produce ethanol, exhibiting high fermentation efficiency of 68%. After 10 cycles, the yeast can still maintain 86% of the initial fermentation efficiency. The yeasts maintain 87% and 93% of the initial cell activity after 1 week store at 4°C in dry state and in yeast extract peptone dextrose (YPD) medium, respectively. This study demonstrates that an aqueous PIPS initiated by peroxide‐target cells is an effective platform to efficiently in situ immobilize cells in a hydrogel for high performance fermentation.

Fabrication of crosslinked starch microspheres via water-in-water Pickering emulsion and their application in controlled release of Vitamin C

Green technology for the fabrication of bio-degradable microspheres is exciting and needed. In this study, a new water-in-water Pickering emulsion green technology is proposed for the fabrication of the crosslinked starch microspheres with sodium tripolyphosphate as the crosslinker, polyethylene glycol aqueous solution as the continuous phase (PEG phase) and starch aqueous solution as the dispersed phase (starch phase). The factors that affect the morphology and particle sizes of cross-linked starch microspheres are investigated by laser scanning confocal microscope (LCM) and laser particle size analyzer. The results reveal that the particle sizes of crosslinked starch microspheres are increasing with increased starch concentration. The particle sizes of crosslinked starch microspheres show a first increase and then decrease trend with the increase of the concentration of PEG 20,000 in the PEG phase. The hydrophobic nano silica is used as an emulsifier to form water-in-water Pickering emulsion and shows an obvious effect on the morphology of starch microspheres. When the starch concentration is 20.00 wt%, PEG 20000 concentration is 32.56 wt%, the ratio of starch to PEG phase is 0.20 and the amount of silica is 5.00 wt% of starch, starch microspheres with regular shapes are obtained with the size of about 32.30 ± 0.22 µm. The fabricated cross-linked starch microspheres are non-crystalline and show good water and oil absorption performances. The application of fabricated crosslinked starch microspheres in the adsorption and release of Vitamin C is conducted. The maximum adsorption capacity of crosslinked starch microspheres for Vitamin C reaches 309.9 mg/g. Starch microspheres show a controlled release of Vitamin C in water. This study indicated that crosslinked starch microspheres can be fabricated through a green water-in-water Pickering emulsion technology and may find potential applications in degradable controlled-release microspheres.

Prediction of bubble departing diameter in pool boiling of mixtures by ANN using modified ReLU

In this research, bubble departure diameter in pool boiling have been measured in aqueous amine and ethylene glycol solutions for various concentrations. The experimental data have been compared with major existing predictive correlations. It is shown that the effect and identity of the independent variables on bubble diameter proposed in the previous studies are inconsistent. The predictions of different correlations have on average a deviation of about 40% from the experimental data. This is mainly due to the complicated interactions between bubbles on the heterogeneous boiling medium, which provides a complex condition. This complexity limits any mathematical modelling of the forces acting on the developing bubbles. Particularly in liquid solutions, where mass transfer by back diffusion through micro-sub-layers adds further complexity. In this work, the classical artificial neural network, ANN, with rectified linear unit, ReLU, activating function, AF, has been modified. This modification is based on adding a numerical matrix to each layer to adjust the slope of AF for each neuron independently. The addition of this parameter, together with the adjustment of the bias matrix, makes the activation function more flexible than the classical ReLU. To find the tuning parameters, a genetic algorithm was implemented instead of the back-propagation technique. It is shown that the predictions of the trained ANN with modified ReLU AF agree within an absolute average error of 10%, which is equal to the total uncertainty of the measurements. Prediction of bubble departing diameter in boiling phenomena is a key parameter for accurate design, operation and optimisation in many industrial systems.

Experimental study of phase change heat dissipation system based on hydrogen fuel cell

In order to improve the internal heat dissipation efficiency of the proton exchange membrane fuel cell, this paper designs and builds a set of fuel cell heat dissipation system experimental bench with a heat dissipation capacity of 15 kW based on the separated heat pipe technology, and investigates the heat dissipation characteristics of the HFE-7100 and ethylene glycol aqueous cooling medium under different condenser processes and different ambient temperatures. The results show that at an ambient temperature of 35 °C, under the same condenser flow arrangement, the two-phase heat dissipation efficiency of HFE-7100 is higher than that of glycol aqueous solution liquid cooling, and its heat dissipation and EER (Energy Efficiency Ratio) are increased by 81.2 %∼98.8 % and 68.2 %∼86.6 %, respectively. The best effect is achieved when the condenser is 3-process, with two-phase heat dissipation of 14.1 kW and EER of 20.5 kW/kW, which are 82.8 % and 68.9 % higher than liquid cooling, respectively. As the ambient temperature rises, the two-phase heat dissipation effect is further improved, and at 50 °C ambient temperature, the heat dissipation is 10.44 kW, which is 145 % higher than that of liquid cooling, and the EER is 15 kW/kW, which is 132 % higher.

Energy storage density enhancement in paraffin phase change material emulsions: A comparative study with two different base fluids

This investigation examined the thermophysical properties of emulsions comprising paraffin 56/58 phase change material (PCM) dispersed in water and ethylene glycol (60 wt%) aqueous solution to optimize energy storage density for low-temperature thermal applications. Dynamic Light Scattering analysis revealed a uniform dispersion of paraffin 56/58 PCM droplets in the basefluids, with an average diameter of approximately 150 nm achieved by incorporating sodium dodecyl sulfate surfactant. The latent heat of fusion for emulsions containing paraffin 56/58 PCM in ethylene glycol (60 wt%) exhibited values of 37.5/41.7, 58.5/63.9, 73.8/75.43, and 93/90.25 J/g for concentrations of 20, 30, 40, and 50 wt%, respectively, during melting/solidification phases. Furthermore, the highest energy storage densities of 306.95 and 361.3 kJ/kg were attained at a PCM concentration of 50 wt% in ethylene glycol (60 wt%) and water-based emulsions, respectively, surpassing those of similar working fluids. It is also indicated that water-based paraffin 56/58 PCMs offer superior energy storage density. However, under severe operating conditions such as extreme temperatures, ethylene glycol (60 wt%) based paraffin 56/58 emulsions demonstrate greater suitability, as the evaporation and freezing points of the basefluid can be adjusted by modulating the ethylene glycol concentration ratio.

Solubility measurement of methane in triethylene glycol aqueous solutions (90,95,98 wt.% triethylene glycol) from 298 to 323 K and 0.17 to 2.5 MPa

Limited phase equilibria data exists for the methane + water + triethylene glycol system. In this work, new phase equilibrium data were measured for this system for a temperature range of 298 to 323 K and a pressure range of 0.17 to 2.5 MPa. These data add to the information that is required in the design of TEG contactor units since they normally operate over a temperature and pressure range of 283 to 329 K, and 2 to 10 MPa respectively. The data were measured using a static synthetic apparatus. The measured data were modelled in Apen Plus V12.1 using the Cubic Plus Association equation of state. The model correlation yielded a satisfactory description of the measured data since the maximum absolute average relative deviation in pressure was 4.30 %.

Complete thermal characterization of liquids by front photopyroelectric configuration using the reference sample method

We explored the use of the front photopyroelectric (FPPE) configuration and the reference sample method to determine the thermal properties of liquid samples such as extra virgin olive oil and aqueous glycerol (GL), ethylene glycol (EG), and sodium chloride (NaCl) solutions. The thermal diffusivity (α) and thermal conductivity (k) were determined from photopyroelectric phase and amplitude signals, respectively, using water as a reference. The thermal effusivity (e) and volumetric heat capacity (ρc) were also determined based upon both obtained thermal properties. All thermal properties of GL and EG in aqueous solutions decrease as their volume fraction increases at an average rate of 5% for concentrations higher than 20% and between 23% and 10% for concentrations less than 20%. The Matvienko and Mandelis’ model for α and our proposed expression for ρc described this trend with a reliable approximation to the experimental data with R 2 about 0.97 and 0.99, respectively. Moreover, the frequency of a specific angle is proportional to α as established by the theory for the phase signal for thermally thick samples. In the case of aqueous NaCl solutions, the α and k values were slightly below 4.6% and 3% from water values reported at room temperature. The proposed method allows the simultaneous determination of α and k by using only the FPPE configuration with test and reference liquid samples, reducing time and uncertainties from the use of more than one experimental setup, and providing the complete thermal characterization.

Heat exchange characteristics of underground and pavement buried pipes for bridge deck heating conditions.

Geothermal energy is increasingly employed across diverse applications, with bridge deck snow melting emerging as a notable utilization scenario. In Jinan city, China, a project is underway to utilize ground source heat pumps (GSHPS) for heating bridges. However, essential operational parameters, including fluid medium, temperature, and heat exchange details, are currently lacking. This study addresses the thermal design challenges associated with ground heat exchangers (GHE) for bridge heating through a combination of numerical modeling and field experiments. Utilizing software Fluent, a refined three-dimensional multi-condition heat transfer numerical analysis was carried out. Field tests based on actual operating conditions were also conducted and the design parameters were verified. The results indicate that an inlet temperature of 5°C and an aqueous solution of ethylene glycol with a mass concentration of 35% as the heat exchange medium are suitable for the GSHPS in Jinan; Moreover, the influence of backfill material and operation time on the heat transfer efficiency was revealed and the suitable material with 10% bentonite and 90% SiO2 was suggested; Finally, based on the influence of the pipe spacing on the heating characteristics of bridge deck, the transition spacing of 0.2 m is given for the temperature response of the bridge deck. This comprehensive study contributes valuable insights through simulation and experimental analysis of the thermal environment variation, aiming to advance the development of GSHPS for bridge deck heating in Jinan, China.

Parallel connected natural circulation loops using different working fluids: experimental results

Natural Circulation Loops (NCLs) are closed-loop systems that transport heat from a source to a heat sink without a pump, relying on free convection of the working fluid. Previous research has focused on the stability and influence of different operative parameters on NCLs. This experimental study investigates the thermo-hydraulic performance of three parallel-connected NCLs with small inner diameters using three different working fluids: deionized water, glycol aqueous solution (50+50% wt), and FC-43 dielectric fluid. This study examines the steady-state behaviour of the NCLs at various heat sink temperatures and heat powers. The results indicate that the common one-dimensional model for a single loop’s steady-state can be applied to this configuration and for all the tested fluids, and a proposed figure of merit can describe the working fluids and predict their steady-state behaviour.

Study of thermodynamic, transport and volumetric properties of nanofluids containing ZrO2 nanoparticles in polypropylene glycol, polyvinyl pyrrolidone and water.

Zirconium dioxide (ZrO2) nanofluids are used in cooling systems, solar energy, and heat exchangers, offering improved heat transfer and efficiency across a wide temperature range. The aim of this work was to study the influence of polypropylene glycol (PPG) and polyvinyl pyrrolidone (PVP) and aqueous solutions of them as a base fluid on stability, volumetric properties, and viscosity of nanofluids containing Zirconium oxide (ZrO2) nanoparticles. The stability of these nanofluids has been confirmed using UV-Vis spectroscopy, and the particle size distribution of the systems using dynamic light scattering (DLS). Among these systems ZrO2-PPG and ZrO2-H2O-PVP30% have appropriate stability. The density, speed of sound and viscosity of these nanofluids have been measured at T = (293.15 to 318.15) K. From these data, the excess molar volume (V E m) and isentropic compressibility (κ s) have been determined. The effects of ZrO2 nanoparticles and temperature have also been investigated on volumetric and transport properties of aqueous solutions of PPG and PVP. The (V E m) values were fitted to the Redlich-Kister, Ott et al., and polynomial equations. Also, the isentropic compressibility (κ s) values were correlated with the polynomial equation. The Eyring-NRTL and Eyring-mNRF models have been used for correlating of the viscosity of the nanofluids with temperature dependency. The performance of the Einstein, Brinkman, Lundgren and Batchelor models in the prediction of viscosity of the nanofluids has also been analyzed.

РЕКУПЕРАЦИЯ ТЕПЛОТЫ ИЗ ВОЗДУХА, УДАЛЯЕМОГО ИЗ ЖИВОТНОВОДЧЕСКОГО ПОМЕЩЕНИЯ

The air removed from the livestock premises by the forced ventilation system contains a significant amount of heat, that can be usefully used, for example, the supply air heating. Currently this energy saving area in the literature is being actively considered. The amount of heat air had being recovered from the indoor rooms depends on the area’s latitude where the livestock farm is located. The influence of cattle farm area’s latitude location saving heat from the air removed from the livestock premises is analyzed. The calculations for three regions of the Russian Federation’s European part located at different latitudes (Rostov, Tambov and Arkhangelsk), in relation to a 280-head cattle farm were performed. To determine the thermal power extracted from the exhaust air, these rooms thermal and material balances (the latter in terms of moisture and carbon dioxide) for the cold (winter) period of the year were compiled and the exhaust air consumption was calculated. In the calculations, a scheme of intermediate coolant, propylene glycol was considered, that circulates between two heating units, the first -on supply air, the second one - on the removed one were installed. It is shown that the farm’s location area latitude gives a significant impact on the energysaving effect: the more northerly the farm is located, the greater the effect, explaining by different indicators of the regions’ heating period under consideration. An payback period’s assessment for capital expenditures and installation work of this system implementation was carried out. The cost of three KSk3-11 brand heaters, a Grundfos UPS 32-80 F 220 circulation pump, 50 liters of propylene glycol aqueous solution, and 100 m of mounting pipes to material costs are attributed. This assessment showed considered heat recovery system’s expediency using. The numerical calculations of obtained results for country’s specified regions can be used economic effect magnitude estimate resulting.

Liquid-Vapor Interface of Aqueous Ethylene Glycol Solutions: A Molecular Dynamics Study.

While the organic constituent in an aqueous binary solution enriches its liquid-vapor (l-v) interface, the extent of enrichment can depend nonlinearly on its mole fraction. A microscopic quantification and rationalization of this behavior are crucial to understand the dependence of properties such as surface tension and evaporation rate of the solution on its composition. Extensive all-atom molecular dynamics simulations of aqueous ethylene glycol (EG) solutions show that the composition of the solution at the l-v interface deviates the most from that in the bulk solution at an EG mole fraction of 0.3. The population of EG molecules with their central C-C dihedral in the gauche conformation was found to be higher at the l-v interface than that in the bulk solution to facilitate the orientation of its hydrophobic methyl groups toward the vapor phase. Free energy calculations reveal that in dilute EG solutions, an EG molecule is most stable at the l-v interface. The behavior of vapor pressure in aqueous EG solutions is ideal and follows Raoult's law, while in contrast, the aqueous solution of dimethyl sulfoxide does not. A rationale for the same is provided through the orientational distribution of interfacial water molecules in the respective solutions.

Evaluations of ethylene glycol and polyethylene glycol aqueous solutions using a hybrid sensor of surface plasmon resonance and quartz crystal microbalance

A hybrid sensor based on surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) was prepared. One of the electrodes of the QCM sensor had a grating structure to enable SPR excitation. The SPR property was investigated through the transmission of the visible-light spectrum. The theoretical calculation showed that the experimental values almost corresponded to the theoretical ones; this suggests that the transmitted light dips were due to SPR. In order to investigate the usefulness of this hybrid sensor, the characteristics of SPR and the oscillation frequency drops of QCM (ΔF QCM) were investigated for aqueous solutions of ethylene glycol and polyethylene glycols with various degrees of polymerization. The position and slope of the SPR dip wavelength and the ΔF QCM curves depended on the degree of polymerization, suggesting that the sensor can be used to evaluate a solution property and/or discriminate a solute material.

Impact of Water Content on the Superlubricity of Ethylene Glycol Solutions

Aqueous solutions of water and ethylene glycol (EG) are prevalently employed in braking, heat transfer, and lubrication systems. However, the precise mechanism through which water content affects the lubricative attributes of EG solutions remains elusive. This research systematically examines the tribological characteristics of EG solutions at varying concentrations using a ceramic–TiAlN friction-pair system. As the concentration of EG increases, the sequential transformation of the associated molecular complex structure in the lubricating medium can be described as follows: [H2O]m·EG → [H2O]m·[EG]n → H2O·[EG]n. Among them, the stoichiometric coefficients “m” and “n” are the simplest mole ratio of H2O and EG in the molecular complex structure, respectively. The most favorable EG concentration was determined to be 50 wt.%. At this concentration, a flexible molecular complex adsorption structure ([H2O]m·[EG]n) with a significant bearing capacity (due to intense hydrogen bonding) forms on the surface of the friction pair, which results in a reduction in the running-in duration and facilitates the achievement of superlubricity, and the coefficient of friction (COF) is about 0.0047. Solutions containing 50 wt.% EG enhance the load-bearing ability and hydrophilicity of the lubricating medium. Moreover, they minimize the roughness of the worn region and curtail the adhesive forces and shear stress at the frictional interface, enabling the realization of superlubricity. Consequently, this research offers valuable insights into the optimal water-to-EG ratio, revealing the mechanism of a superlubricity system that possesses exceptional tribological attributes and holds significant potential for practical applications.