Glycol-water Mixture Research Articles

Thermo-Hydraulic Performance of Heated Tube with Twisted Delta Winglet Swirler Insert: A Numerical Simulation

Among the various methods for enhancing heat transfer in a heat exchanger, a passive method of inserting a continuous swirler inside a heated tube provides a secondary flow along the fluid that reduces the thickness of the thermal boundary layer, thus increasing the efficiency of convection heat transfer performance. The research’s primary goal is to conserve energy, materials, and money by operating efficient heat exchanger equipment. However, the continuous swirler along the fluid flow creates a persistent obstruction, which amplifies the friction factor and increases the working fluid’s energy loss. As a result, this research presented the twisted delta winglet swirler (TDWS), a new design of a decaying swirler that uses delta winglets twisted to 180° to produce a swirling flow along the tube. The swirler comprises four twisted delta winglets arranged in a circle with a diameter 6% smaller than the tube and a length of L/D=2.2. It was placed at the entrance to a heated tube test section with a diameter of 0.016 m and a length of L/D=93.75. The Reynolds Stress Model was used to simulate the flow domain with a water-ethylene glycol mixture was chosen as the working fluid. TDWS transformed the uniform inlet flow from potential energy to high kinetic energy, resulting in a high intensity of swirling flow downstream of the circular tube up to L/D=46.88 before decaying and reaching a steady state. Compared to other decaying swirlers, TDWS obtained one of the lowest relative friction factors, 1.36, with this flow. The maximum global relative Nusselt number increased by only 11% because this value considered the area where the flow reached a steady state. Since the TDWS is a decaying swirler, the thermal-hydraulic performance reached unity along the tube. However, the optimal performance of TDWS in the plain tube with a length of L/D=93.75 can be found if the dimension or geometric configuration of the TDWS is modified, or two or more TDWS may be placed in an array orientation.

Intrinsically adhesive, conductive organohydrogel with high stretchable, moisture retention, anti-freezing and healable properties for monitoring of human motions and electrocardiogram

A novel self-adhesive conductive organohydrogel without catechol adhesive components is developed for long-term, continuous monitoring of human motions and electrocardiogram. The organohydrogel is achieved by covalent cross-linking polymerization of acrylamide, N-acryloylglycinamide, and reduced graphene oxide, followed by soaking into ethylene glycol-water mixture. The organohydrogel exhibits intrinsic adhesion to various substances, excellent healing ability of nearly 100% conductivity repair rate, long-lasting moisture retention (about 30 days), extreme temperature tolerance (–20–60 °C), stable conductivity and extraordinary mechanical properties with a maximum tensile strength of 300 kPa, high stretchability over 1700%, compressive stress over 5 MPa. This organohydrogel can adhere to human skin without other fixture for human motions monitoring, such as the bending of wrist, finger, elbow and knee, and throat actions. Moreover, the organohydrogel can achieve long-term, continuous monitoring of human ECG signals in various daily activities, such as a night of sleep, standing, walking, performing leg curls and leg presses, and using an elliptical machine. This research offers a new strategy to develop self-adhesive conductive organohydrogel for long-term, continuous, and imperceptible monitoring of human health signals.

Numerical investigation on Enhancing Heating performance in Automotive Radiator

In this paper, the improvement of heat exchange in a compact heat exchanger that is used in the automotive cooling system is numerically studied due to the importance that this part of the automotive represents in removing the heat generated in the automotive engine. The study adopted CFD simulation to introduce a new design of radiator that included changing the geometry and material of the tube while maintaining the same cross-section area In addition, the study also included replacing the shape of the fins from the louver to plain fin with the increase in the number of tubes. The study used a water-Ethylene glycol mixture (50:50) as a hot fluid with four flow rates (10, 12, 18, 24) l/h, (75, 85, 95) °C inlet temperature, and air as a cold fluid with 1.5, 2.5, 4.5, 5.5) m/s and (35) °C inlet temperature. Through the results obtained, the designed model appeared to have a higher thermal performance than the standard model due to the material and shape of the tube and fins. The designed model performed well, achieving an improvement ratio of (18.6%) for the heat transfer rate, (13.8%) for the overall heat transfer coefficient for the hot fluid, and (29.8%) for the air-side heat transfer coefficient

Characterization of Fluorescence Tracers for Thermometry and Film Thickness Measurements in Liquid Coolants Relevant for Thermal Management of Electric and Electronic Components.

This study investigated a novel two-color LIF (laser-induced fluorescence) technique for thermometry in coolants relevant for electric components. In principle, this diagnostic enables thermometry in liquid flows but also a simultaneous determination of film thickness and film temperature, which is relevant, e.g., for jet impingement cooled electric components. Temperature measurements are based on a temperature-sensitive intensity ratio of special tracers realized by suitable band pass filters within the respective emission spectra. For this purpose, the heat transfer fluids Fragoltherm F12, Marlotherm LH, and a water-glycol mixture WG20 (80 vol.% water, 20 vol.% glycol) and its individual components were doped with suitable tracers. The tracer Eosin-Y was utilized for polar coolants (water, WG20, and glycol) and Nile red was utilized for non-polar solvents (Fragoltherm F12 and Marlotherm LH). The spectral LIF intensities were recorded for a wide range of temperatures (253-393 K), which are relevant for cooling of electric motors, batteries, and power electronics. Furthermore, absorption spectra were analyzed as well. The temperature-dependent fluorescence measurements revealed different behavior for the polar and non-polar solvents. A temperature increase in the polar solvents (water, WG20, glycol) led to a spectral shift of the emission peaks of Eosin-Y towards longer wavelengths (red-shifted), while the peaks of Nile red in the non-polar solvents (Fragoltherm F12 and Marlotherm LH) showed an opposite behavior and were blue-shifted. The highest average temperature sensitivity was achieved for Marlotherm LH (4.22%/K), followed by glycol (1.99%/K), WG20 (1.80%/K), water (1.62%/K), and Fragoltherm F12 (1.12%/K). These sensitivities are similar to or even much higher than the literature data of other LIF tracers, which were, however, not determined in those coolants. Consequently, the two novel proposed dyes for the studied heat transfer liquids enable a reliable temperature determination.

Thermal management of lithium-ion batteries using carbon-based nanofluid flowing through different flow channel configurations

In this study, a novel lithium-ion battery (LIB) thermal management system is developed, and its cooling performance for cylindrical 18,650 LIB cells under different discharging rates is experimentally observed. The experiments are carried out using indirect-type liquid cooling with single and dual aluminium serpentine channels with different flow configurations. The study includes the preparation of nanofluid using multi-walled carbon nanotubes (MWCNTs) at three different volume fractions (Vf) (0.15%, 0.3%, and 0.45%) in the mixture of ethylene glycol and water and compares their cooling performance with water and ethylene glycol-water mixture. At 0.45% Vf of MWCNTs, the maximum drop in the average temperature of the battery cells is observed about 6.9 °C, 10.2 °C, and 11 °C at 2.1C in a single-channel flow configuration, dual-channel with parallel flow configuration, and dual-channel with counter-flow configuration, respectively. Dual-channel with counter-flow configuration provides the best cooling performance in terms of temperature drops of 8.6–13 °C using different working fluids. When a counter-flow configuration is used, the battery module's temperature uniformity is very good, with a maximum deviation of 1.5–3 °C, well within the safe limit to prevent thermal runaway. The pressure drop for 0.45% Vf of MWCNTs is 13.3% and 14% higher than water for single-channel and dual-channel, respectively.

Aggregation and adsorption behavior of cobalt‐based metallosurfactant in water–ethylene glycol media forming worm‐like micelles

AbstractThe cobalt based metallosurfactant cis‐chlorobis(ethylenediamine)hexadecylaminecobalt(III) chloride (CHCC) has been prepared and well characterized by utilizing elemental analysis, NMR (1H, 13C), FT‐IR and UV–Vis spectroscopy. The CHCC metallosurfactant shows thermal stability up to 168°C. The micellization behavior of the synthesized CHCC metallosurfactant has been investigated systematically by the tensiometric, conductometric, and fluorescence techniques. The critical micelle concentration (cmc) values of CHCC have been determined in various water–ethylene glycol mixtures ranging from 0 to 100 weight % of ethylene glycol at 293.15, 298.15, 303.15, and 308.15 K. The physicochemical parameters namely counterion binding constant, surface pressure, surface excess, surface area covered per CHCC metallosurfactant molecule, free energy minimum, standard free energies of micellization and adsorption, standard enthalpy and entropy of micellization, and Gibb's free energy of transfer have been calculated. The hydrodynamic diameters and zeta potentials of the CHCC metallomicelles have been measured by dynamic light scattering method. Transmission electron microscopy was employed to confirm the presence of worm‐like micelles.

Difference in aqueous solution structure at 293.2 and 473.2 K between ethanol and ethylene glycol via molecular dynamics

Our recent experimental study found that ethylene glycol–water mixture at 473.2 K and 10 MPa has a positive excess molar volume in water-rich region in contrast to the negative one at 293.2 K and 0.1 MPa and that in ethanol–water mixture [1]. The present study performed molecular dynamics simulation to clarify the difference in the solution structure between the two aqueous mixtures at the two temperatures. Radial distribution functions, coordination (hydration) numbers, numbers of hydrogen bonding and spatial distribution functions were calculated around the hydroxyl groups of alcohol and water molecules. In both mixtures, hydrogen bonds between alcohol and water molecules and between water molecules were shown to remain even at 473.2 K although the number of hydrogen bond decreased upon the temperature increase. In addition, at the high temperatures, it was indicated that tetrahedral-like hydrogen bonding network among water molecules was lost in ethylene glycol–water mixture whereas it remained in ethanol–water one.

Development and validation of Nusselt number correlations for a helical coil based energy storage integrated with solar water heating system

Storage tanks based on helical coil heat exchangers are an integral part of solar water heating systems and require optimal design configuration to achieve maximum heat transfer and a longer storage period. This study is focused on thermal analysis of a vertical helical coil-based water storage tank and derivation of inner and outer Nusselt number correlations by considering the storage tank as well as helical coil and catering to both forced and natural convection effects. A fluid-fluid conjugate heat transfer transient state model is validated with experiments performed with 50/50 % water-glycol mixture as heat transfer fluid at flow rates of 2 and 3 L/min in a solar water heating system, while water remains at static flow condition inside the tank. To reduce the computational cost, a symmetrical downsized (50 % of the real storage tank size) model is also designed and validated, which showed a mean absolute percentage error of 3.25 %. In order to derive the mathematical correlations, alterations were made to the validated model by using coils with curvature ratios ranging from 0.09 to 0.184 with HTF flow rates in laminar flow regimes, ranging from 30 to 100 L h−1 at temperatures from 40 °C to 80 °C. Furthermore, inner Nusselt number mathematical correlations based on M number, curvature ratio, and Prandtl number showed good agreement with correlations derived by past investigators. Similarly, the outer Nusselt number of the coil was related to Rayleigh's number and the derived relations showed good agreement with the past studies, while Nuo = 0.1996 (Rado0.326) showed the least error of 2.06 %. Finally, thermal stratification analysis helped to understand that coil position and aspect ratio determine the thermocline developed inside the storage tank. Results show that extension of coil inside the tank up to 83.7 % of the tank height, ensured greater thermocline range, and tank with aspect ratio 3 turned to be better for thermal energy storage for longer period.

Transient isogeometric heat conduction analysis of stationary fluid in a container

This article is devoted to the numerical simulation of transient heat conduction problems in fluids. A numerical formulation depending on isogeometric analysis-based GeoPDE's toolbox is employed to establish the viability of isogeometric analysis as a tool for analysing heat conduction problems. An experimental analysis is conducted on a physical model of a container for checking the change in temperature with time. Then the isogeometric analysis is used for the development of a numerical model and evaluation of unknown field variable, that is, temperature and its dependent properties. The validation of the proposed model is done by comparing it with an experimental analysis and calculating the coefficient of correlation between the two models. As a result, +0.99 value of correlation coefficient is devious out, which presents a positive relationship between the two. Based on the validated results, the proposed model is employed for the evaluation of thermophysical properties for different fluids like liquid water and ethylene glycol–water mixture. The evaluated properties of ethylene glycol–water solution are compared with existing literature values. A root mean square error is compared between evaluated and literature property values for various concentrations. The deduced values are in the range of 2.3%–8.4% for density and 0.26%–4.6% for viscosity. It is found that isogeometric analysis can be effectively applied in heat conduction problems using GeoPDE.

Experimental Studies and Analytical Analysis of Thermophysical Properties of Ethylene Glycol–Water-Based Nanofluids Dispersed with Multi-walled Carbon Nanotubes

The present study investigates the thermal conductivity and dynamic viscosity of ethylene glycol–water solutions dispersed with oxidized multi-walled carbon nanotubes. The physico-thermal properties and Mouromtseff number (Mo) were used to evaluate the heat transfer properties of the nanofluids. Ethylene glycol–water mixtures were chosen as base fluids, and the volume fraction of ethylene glycol varied from 100 % to 0 % (pure water). Oxidized multi-walled carbon nanotubes in weight percentages of 0.0625, 0.125, 0.25, and 0.5 were dispersed in ethylene glycol–water mixtures to achieve the best stability. The stability of the nanofluids was monitored by UV–Vis spectroscopy for 2 months. The dispersion of multi-walled carbon nanotubes in the base fluids resulted in a significant improvement in thermal conductivity. To derive correlations for thermal conductivity and dynamic viscosity, 1 500 data points were collected for all possible combinations of temperature, weight percent of multi-walled carbon nanotubes, and ethylene glycol content. The Mouromtseff number (Mo) showed that dilute nanofluids at low concentrations are the most effective heat transfer medium in turbulent flow.

Performance analysis of liquid-based battery thermal management system for Electric Vehicles during discharge under drive cycles

The performance of an Electric Vehicle (EV) is determined by the battery pack's specific power, specific energy, self-discharging rate, and cycle life. However, these parameters are sensitive to temperature. Therefore, thermal management is the most critical factor defining a battery pack's performance in an EV. Even though thermal management of lithium-ion batteries has received a lot of attention, there has been minimal research on the performance of liquid based battery thermal management systems for Electric Vehicles for the actual drive cycles like the Indian drive Cycle and Federal Test Procedure (FTP-75) drive cycle. This study investigates the thermal behaviour of the Li-ion battery pack of an EV and the performance of a liquid-based battery thermal management system with various coolant options, such as Water, Water-Ethylene Glycol mixture, and Water-Propylene glycol mixture for both Indian Drive Cycle and FTP-75 (Federal Test Procedure) Drive Cycle. The numerical simulation is carried out for a battery pack with four modules, and liquid-based battery thermal management is designed at the pack level, considering the heat generated in the battery pack. The variation of battery pack temperature and cumulative energy consumption by the battery thermal management system (BTMS) is also investigated. The simulation model is designed in such a way that it tries to maintain a set battery pack temperature of 25 °C. Also, the effect of ambient temperature on the performance of the liquid cooling system has been analyzed. The results indicated that with the increase in ambient temperature the BTMS takes a longer time to cool the battery pack and cumulative energy consumption by the liquid based BTMS also increases for both the drive cycles. In the case of Water-Propylene glycol mixture, 25 % propylene glycol concentration is recommended, whereas in the case of Water-Ethylene glycol mixture, 50 % ethylene glycol concentration provides the best performance as both cumulative energy consumption by the battery thermal management system and temperature distribution in the battery pack are optimum.

Zeta potential and particle size in dispersions of alumina in 50–50 w/w ethylene glycol-water mixture

HypothesisDispersions of solid particles in glycols and in their mixtures in water have been proposed as promising heat transfer fluids, and the zeta potentials in such systems are often reported. We challenge a popular approach in which high absolute value of zeta potential implies excellent stability in such systems. ExperimentsNanoparticles of alumina were dispersed in 50–50 ethylene glycol-water mixture, and zeta potential and particle size were studied as a function of concentration of various solutes. FindingsAddition of HCl and CTMABr induced positive zeta potentials. A maximum value of about 120 mV was obtained at CTMABr concentration of about 10−5 M, and further increase in the concentration of the surfactant had moderate effect on the zeta potential. A maximum value of about 120 mV was obtained at HCl concentrations of 10−5 - 10−4 M, and further increase in the HCl concentration led to depression of the zeta potential. Addition of NaOH and KOH, and of anionic surfactants induced negative zeta potentials. With NaOH and KOH the maximum negative zeta potential of − 60 mV was obtained at base concentration of about 10−3 M, and increase in the base concentration to 10−2 M had moderate effect on the zeta potential. Negatively charged particles showed substantial aggregation in spite of high negative zeta potentials.

Carboxylate functionalized NaDy(MoO4)2 nanoparticles with tunable size and shape as high magnetic field MRI contrast agents

Uniform sodium-dysprosium double molybdate (NaDy(MoO4)2) nanoparticles having different morphologies (spheres and ellipsoids) and tunable size have been synthesized for the first time in literature. The procedure is based on a homogeneous precipitation process at moderated temperatures (≤220 °C) from solutions containing appropriated precursors dissolved in ethylene glycol-water mixtures, in the absence (spheres) or the presence (ellipsoids) of tartrate anions. The effects of the morphological characteristics (size and shape) of the nanoparticles on the magnetic relaxivity at high field (9.4 T) have been evaluated finding that the latter magnitude was higher for the spheres than for the ellipsoids, indicating their better suitability as contrast agents for high-field magnetic resonance imaging. Such nanoparticles have been successfully coated with polymers bearing carboxylate functional groups through a layer-by-layer process, which improves the colloidal stability of the nanoparticles in physiological media. It has been also found that the coating layer had no significant effects on the nanoparticles relaxivity and that such coated nanoparticles exhibited a high biocompatibility and a high chemical stability. In summary, we have developed NaDy(MoO4)2 based bioprobes which meet the required criteria for their use as contrast agents for high-field magnetic resonance imaging.

Zinc glycolate Zn(OCH2CH2O): Synthesis and structure, spectral and optical properties, electronic structure and chemical bonding

This article presents new findings obtained from the study of formation conditions, crystal structure, thermal, spectral, optical properties and electronic band structure of zinc glycolate Zn(OCH2CH2O). This compound was synthesized by heating the solutions of zinc formate Zn(HCOO)2·2H2O in ethylene glycol (A) or in a mixture of ethylene glycol and distilled water (B). The crystal structure of Zn(OCH2CH2O) has been studied using the X-ray powder diffraction method. It is shown that the crystal structure is built via zigzag joining of [Zn4O12C8H16] tetracycles with the tetrahedrally coordinated zinc (ZnO4). Zinc atoms inside the tetracycles and the tetracycles themselves are interconnected with oxygen bridges. Complex anions OCH2CH2O2- are bonded to zinc atoms by chelation. The unit cell parameters of Zn(OCH2CH2O) are as follows: the tetragonal structure, space group I41/a (88−2), Z = 16, a = b = 11.08673(9) Å, c = 11.5902(1) Å, V = 1424.62(2) Å3. The IR and Raman spectra of Zn(OCH2CH2O) correlate fully with the results of structural analysis. Under UV excitation, the luminescence spectra of Zn(OCH2CH2O) samples synthesized following the methods (A) and (B) are characterized by emission maxima at 460 nm (blue luminescence) and 540 nm (yellow-green luminescence), respectively. Yellow-green luminescence is due to the presence of an admixture of zinc oxide nanoparticles of size 10 nm in the sample. The electron density functional method is employed to study the electronic band structure and chemical bonding in Zn(OCH2CH2O). It is shown that the 3dZn orbitals are covalently bonded to 2pO orbitals so that an octagon is formed, where the zinc atoms of four neighboring ZnO4 tetrahedrons are linked through their vertices. The feasibility of synthesizing a layered structure of Zn(OCH2CH2O) is analyzed on the basis of ab initio calculations and Voigt-Reuss-Hill theory.

Entropy Generation and Statistical Analysis of MHD Hybrid Nanofluid Unsteady Squeezing Flow between Two Parallel Rotating Plates with Activation Energy

Squeezing flow is a flow where the material is squeezed out or disfigured within two parallel plates. Such flow is beneficial in various fields, for instance, in welding engineering and rheometry. The current study investigates the squeezing flow of a hybrid nanofluid (propylene glycol–water mixture combined with paraffin wax–sand) between two parallel plates with activation energy and entropy generation. The governing equations are converted into ordinary differential equations using appropriate similarity transformations. The shooting strategy (combined with Runge–Kutta fourth order method) is applied to solve these transformed equations. The results of the conducted parametric study are explained and revealed in graphs. This study uses a statistical tool (correlation coefficient) to illustrate the impact of the relevant parameters on the engineering parameters of interest, such as the surface friction factor at both plates. This study concludes that the squeezing number intensifies the velocity profiles, and the rotating parameter decreases the fluid velocity. In addition, the magnetic field, rotation parameter, and nanoparticle volumetric parameter have a strong negative relationship with the friction factor at the lower plate. Furthermore, heat source has a strong negative relationship with heat transfer rate near the lower plate, and a strong positive correlation with the same phenomena near the upper plate. In conclusion, the current study reveals that the entropy generation is increased with the Brinkman number and reduced with the squeezing parameter. Moreover, the results of the current study verify and show a decent agreement with the data from earlier published research outcomes.

Squeezed flow of polyethylene glycol and water based hybrid nanofluid over a magnetized sensor surface: A statistical approach

Hybrid liquids having better energy transportation properties comparative to mono-fluids. Such materials have appliances in distinct areas like military equipment and solar collectors. When thermal radiation and heat source are significant, nothing is known on a comparative analysis between the dynamics of chemically reactive polyethylene glycol and water-zirconia nanofluid and polyethylene glycol and water-zirconia‑magnesium oxide hybrid nanofluid over a permeable sensor surface. The results are presented in two cases: hybrid nanofluid (propylene glycol-water mixture + zirconia+ magnesium oxide) and nanofluid (propylene glycol-water mixture + zirconia), using the Runge-Kutta fourth-order based shooting method. The squeezed flow index parameter reduces both fluid temperature and velocity, according to the study's main findings. When the squeezed flow index parameter is increased, the surface drag force decreases at a rate of 0.47936 (in the case of hybrid nanofluid). There is also a significant positive relationship between two parameters (chemical reaction and Schmidt number) and mass transmission rate. Both parameters are increasing at 0.870459 and 0.886875, respectively. Furthermore, it is discovered that the magnetic field improves fluid velocity (due to the squeezing of the upper plate) and heat transfer rate decreases at a rate of 1.50787 as the heat source parameter increases.

Entropy generation minimization of Ag-Fe_3O_4/water-ethylene glycol squeezed hybrid nanofluid flow between parallel disks

PurposeThis paper aims to examine the squeezing flow of hybrid nanofluid within the two parallel disks. The 50:50% water–ethylene glycol mixture is used as a base fluid to prepare Ag–Fe_3O_4 hybrid nanofluid. Entropy generation analysis is examined by using the second law of thermodynamics, and Darcy’s modal involves estimating the behavior of a porous medium. The influences of Viscous dissipation, Joule heating and thermal radiation in modeling are further exerted into concern.Design/methodology/approachFor converting partial differential systems to ordinary systems, a transformation technique is used. For the validation part, the numerical solution is computed by embracing a fourth-order exactness program (bvp4c) and compared with the analytical solution added by the homotopy analysis method (HAM). Graphical decisions expose the values of miscellaneous-arising parameters on the velocity, temperature and local-Nusselt numbers.FindingsHybrid nanofluid gives significant enhancement in the rate of heat transfer compared with nanofluid. The outcomes indicate that the average Nusselt number and entropy generation are increasing functions of the magnetic field, porosity and Brinkman number. When the thermal radiation rises, the average Nusselt number diminishes and the entropy generation advances. Furthermore, combining silver and magnetite nanoparticles into the water–ethylene glycol base fluid significantly enhances entropy generation performance.Originality/valueEntropy generation analysis of the magneto-hydrodynamics (MHD) fluid squeezed between two parallel disks by considering Joule heating, viscous dissipation and thermal radiation for different nanoparticles is addressed. Furthermore, an appropriate agreement is obtained in comparing the numerical results with previously published and analytical results.

The developing flow characteristics of water - ethylene glycol mixture based Fe3O4 nanofluids in eccentric annular ducts in low temperature applications

• The effect of nanofluids’ lower viscosity values on heat transfer was investigated. • Annular flow propagation of water-ethylene glycol based Fe 3 O 4 nanofluid was studied. • Maximum heat transfer enhancement was obtained for highest concentration. • Addition of the nanoparticles resulted in delay to reach steady-state conditions. • The performance evaluation criteria, pressure drop and exergy analysis were studied. Natural circulation loops with double pipe heat exchangers at heating and cooling ends have a potential to be used in the refrigeration systems as an alternative to suction line heat exchangers. The heat transfer capability of such natural circulation loops depends on the geometrical parameters as well as thermophysical properties of the working fluid. This study aims to investigate the effect of water-ethylene glycol mixture based Fe 3 O 4 nanofluids (0.01, 0.05 and 0.1 vol.%) on the annular flow propagation and heat transfer in the annuli of double pipe heat exchanger at low pressure side of the refrigeration cycle. In addition to increased non-dimensional velocity values due to the lower viscosity and higher non-dimensional temperature values with expanded temperature gradient, improved heat transfer by nanofluids shows that they can be used as secondary heat transfer fluids at low-pressure side in refrigeration systems. Although the maximum transferred (13.6% improvement compared to base fluid) heat observed for the highest concentration, the nanofluids with smallest concentration has the minimum pressure drop value (25% reduction compared to base fluid) and the highest performance evaluation criteria (PEC) value (PEC = 1.08) with tiny increase in exergy destruction (1.45% compared to base fluid).

Transient Chemical Activation of Covalent Bonds for Healing of Kinetically Stable and Multifunctional Organohydrogels

Transient Chemical Activation of Covalent Bonds for Healing of Kinetically Stable and Multifunctional Organohydrogels

Solubility of meloxicam in ethylene glycol-water and propylene glycol-ethanol mixtures: Experimental determination and thermodynamic analysis

The solubility profile of meloxicam in ethylene glycol (EG)-water and propylene glycol (PG)–ethanol mixtures at five temperatures in the range of 288.15–308.15 K under atmospheric pressure are determined and related by means of the Jouyban-Acree model. Experimental results show that solubility always increases as temperature increases; and, when the composition of ethylene glycol increased in the first mixture, while in the second one is maximum, in the region 0.4 < XPG < 0.8. The thermodynamic parameters (Gibbs energy, enthalpy and entropy) of meloxicam in both systems are also calculated by using vańt Hoff and Gibbs equations. Both Gibbs energy and enthalpy of solution are positive in the mixture under analysis. As far as, dissolution entropy is negative in all proportion of EG except for neat ethanol; in PG mixture is positive when 0.1 > XPG and the range 0.4 < XPG < 0.6. For ethylene glycol–water mixtures, enthalpy-driving is the main contributing force to the Gibbs energy. Conversely, in propylene glycol systems, the entropic contribution is higher.