Aqueous Solutions Of Propylene Glycol Research Articles

The Method of Calculating the Heat Transfer Coefficient in the Heliosystems with Laminar and Transient Modes of Heat Carrier Flow Movement Structured Into Parts

In this study, a new method of choosing classical empirical equations for calculating heat transfer coefficients in the tubes of a shell-and-tube heat exchanger in the transient mode is proposed. This method is based on the fact that the flow is structured into a laminar boundary layer (LBL) zone and a turbulized part, and the heat transfer coefficient is calculated through the transient and turbulent heat conductivity, as well as the average thickness of the LBL and, accordingly, the average thickness of the rest of the coolant flow. At the same time, the key point of this method is the condition that the transient thermal conductivity of the LBL should be lower than the thermal conductivity of the turbulized part. If this condition is not fulfilled, it is concluded that the corresponding classical empirical equation is not suitable for calculating the heat transfer coefficient. A 45% aqueous solution of propylene glycol was taken as a model liquid, which can be widely used in solar collectors, in particular with nanofillers. This coolant is interesting because at a constant speed of V = 0.93 m/s, and the linear size (diameter) of the "live section" of the flow D = 0.021 m in the temperature range of 243–273 K it moves in the laminar mode, in the temperature range of 283–323 K — in transient mode and 333–353 K — in turbulent mode. A new formula is proposed for calculating the coefficient of turbulence of the coolant flow a, the numerical values of which are experimentally found in literary sources only for the air coolant.

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.

Planar light induced fluorescence quenching oxygen diffusivity measurement near the gas–liquid interface in aqueous glycerol and aqueous propylene glycol

Experimental diffusivity data for gases in liquid mixtures are still scarce. To measure the diffusivity of dissolved oxygen in aqueous solutions of glycerol and propylene glycol, a planar light induced fluorescence (PLIF) method has been employed. The experimental method developed allows the measurement of the concentration field near the gas–liquid interface. The results show an increased oxygen diffusivity for the aqueous glycerol solution compared to the aqueous propylene glycol solution, corresponding to the lower viscosity of the solvent. Interestingly, during the first few seconds of oxygen absorption, a reduced early diffusivity is found for both experiments compared to later times. The results are compared with selected correlations and available experimental values. In general, the results are in good agreement with the literature data found and the discrepancy between early and later diffusivity is discussed.

Improvement of the Method of Calculating Heat Transfer Coefficients Using Glycols Taking into Account Surface Forces of Heat Carriers

This study compares the classic calculating method of the heat transfer coefficients of the shell-and-tube heat exchanger tubes using the classic Nusselt, Reynolds, and Prandtl similarity numbers with a new method that takes into account the coefficients of surface tension of heat carriers, their transitional, turbulent viscosity and thermal conductivity, as well as the average thickness of the laminar boundary layer (LBL). The classic method shows a better efficiency of water as a heat carrier com-pared to a 45% aqueous solution of propylene glycol. Instead, the new calculation method shows that a 45% aqueous solution of propylene glycol at the same Rey-nolds numbers has higher heat transfer coefficients com-pared to water in the temperature range of 273–353 K. We divided the "live cross-section" of the flow of the liquid coolant into a medium-thick LBL, where the Fourier equation of thermal conductivity is applied, and into its turbulent part, where the equation of thermal conductivity with turbulent thermal conductivity is also applied. A new formula (14) is proposed for calculating the average thickness of the LBL based on the radius of the "live cross-section" of the coolant flow, as well as the Blturb similarity number obtained by us in previous works. A new formula (15) is also proposed for calculating the heat transfer coefficient, which includes the transitional and turbulent thermal conductivity of the corresponding zones of the flow "live section", as well as the average thickness of the LBL.

Effects of Coolant and Working Temperature on the Cavitation in an Aeronautic Cooling Pump with High Rotation Speed

The centrifugal pump with high rotation speed is the key component in the cooling system of an aircraft. Because of the high rotation speed, the impeller inlet is very prone to cavitation. Two impellers with different types of blades (cylindrical and splitter) are designed, and the numerical models of the pumps are built. The authenticity of the numerical models is validated with the corresponding experiments in terms of both the hydraulic and cavitation characteristics. Then, the effects of different coolants and working temperatures on the hydraulic and cavitation performances of the prototype models are studied based on the numerical simulations. The results show that the head and efficiency of the pump for conveying water are higher than those for conveying ethylene glycol (EG) aqueous solution and propylene glycol (PG) aqueous solution (EGaq and PGaq are defined to represent the EG aqueous solution and the PG aqueous solution, respectively). The hydraulic performance in the EGaq is slightly better than that in the PGaq. The cavitation performance of water is far less than that of the EGaq and PGaq under high working temperature. The volume of cavitation in EGaq is smaller than that in PGaq, and the volume of cavitation in the splitter blades is slightly smaller than that in the cylindrical blades. It is suggested that EGaq be used as the first option. The splitter blades can improve the cavitation performance somehow while the improvement by using the splitter blades is very limited at high rotation speeds, and the design of the short blades should be careful in order to obtain a smooth internal flow field.

Sulcatol and Fuscumol Increase Catches of Leptostylus asperatus and Styloleptus biustus (Coleoptera: Cerambycidae) in Ethanol-Baited Traps

Sulcatol and Fuscumol Increase Catches of <i>Leptostylus asperatus</i> and <i>Styloleptus biustus</i> (Coleoptera: Cerambycidae) in Ethanol-Baited Traps

Insight into macroscale superlubricity of polyol aqueous solution induced by protic ionic liquid

Currently, macroscale liquid superlubricity remains limited to low applied loads and typical ceramic friction pairs. In this study, a robust macroscale superlubricity with a coefficient of friction (COF) of approximately 0.006 is realized at the bearing steel interface induced by protic ionic liquids (ILs) in propylene glycol aqueous solution, and the lubrication system exhibits excellent anti-corrosion properties. Results show that superlubricity can be achieved by employing ILs with longer alkyl chains over a wide load (< 350 N) and speed (> 700 r/min) range. By systematically investigating factors affecting superlubricity, including the IL structure, ionization degree, test conditions, polyol, water-to-alcohol ratio, and lubrication state, the superlubricity mechanism is discussed. Notably, a thicker and denser stern layer can be formed using ILs with longer alkyl chains, which participates in the tribochemical reaction with the metal substrate to form a tribofilm during rubbing. The hydrogen bond network layer formed by the hydrogen ion and polycol aqueous solution can withstand high applied loads. Water can be used to reduce the shear stress of polyols, and enable superlubricity to be achieved under high-speed rotations. Moreover, an inevitable running-in period serves as a dispersing contact stress and dynamically forms a lubricating film, where the lubrication state locates mixed lubrication and then transforms into boundary lubrication as the roughness of the contact surface increases. This study is expected to significantly promote the development and application of superlubricity in the engineering field.

Viscosity Model for Liquid Mixtures of Propylene Glycol, Glycerol, and Water

The viscosity of liquid mixtures in e-vapor products (EVPs) is key to their performance and is sensitive to mixture composition and temperature. To date, no accurate model exists for the viscosities of said mixtures. Herein, we report an empirical model for the viscosity of liquid mixtures containing propylene glycol (PG), glycerol (GL), and water (W), representative of the mixtures in EVPs. The model captures the interactions between component liquids and makes accurate viscosity predictions for liquid mixtures of PG, GL, and W, as well as such mixtures containing small amounts of menthol, from 20 to 80 °C. The model is calibrated to new experimental data for PG–GL–W ternary mixtures and may be extended to incorporate different or additional liquids or a wider temperature range given additional fitting data. The model should also prove beneficial for food, cosmetic, and pharmaceutical products containing aqueous solutions of PG and GL.

An experimental study of Al2O3 nаnoparticles influence on caloric properties of propylene glycol based coolants

Nanofluids are promising heat carriers, which contribute to the overall efficiency of energy systems. The main obstacle to the practical application of nanocoolants based on aqueous propylene glycol solutions is the lack of accurate data on their thermophysical properties. In the paper, experimental study (adiabatic calorimetry method) of the heat capacity and parameters of solid phase – liquid phase transitions of propylene glycol and coolant based on aqueous propylene glycol solution is carried out. Experimental study of the heat capacity of the liquid phase of the coolant based on an aqueous solution of propylene glycol with additives of Al 2 O 3 nanoparticles (up to 2.01 wt. %) in the temperature range of 235...338 K and propylene glycol with additives of Al 2 O 3 nanoparticles (1.03 wt. %) in the temperature range of 268…335 K is performed. The comparison of the temperature dependence of the effective heat capacity of coolants with changes in their internal structure is made. It is shown that adding water to propylene glycol increases the temperature and heat of the solid phase – liquid phase transition (the heat of the propylene glycol phase transition is 37.85 J∙g –1 , propylene glycol/water coolant (54/46 wt. %) – 77.97 J∙g –1 ). It is shown that additives of Al 2 O 3 nanoparticles both in propylene glycol and in the coolant based on an aqueous propylene glycol solution contribute to the reduction of the heat capacity of the liquid. The heat capacity decreases approximately in proportion to the increase in the concentration of nanoparticles. The effect of heat capacity reduction is greater at high temperatures (3.9 % at 265 K and 5.0 % at 325 K for the nanocoolant with an Al 2 O 3 nanoparticle concentration of 2.01 wt. %). The results obtained will improve the design quality of heat exchange equipment using nanocoolants. The results are useful for developing methods for predicting the specific heat of nanofluids

Experimental and numerical study of non-stationary solid-liquid phase transitions of n-tetradecane

During the experiments, four spherical flasks with n-tetradecane with a total mass of 0.344 kg were placed in a test container inside which an aqueous solution of propylene glycol with a mass concentration of 50% and an initial temperature of 25 °C was circulating. As a result of studies, the values of heat flows at different time intervals during the solid-liquid phase transition of n-tetradecane were obtained. Based on the modeling of the processes, the distribution of temperature and velocity of the heat carrier in the test container as well as the values of the local heat transfer coefficients on the surface of the flasks were established. Numerical calculations of the process of phase transition being studied according to the authors’ model were also performed. Numerical calculations of the process under study have been performed using the authors’ model. A satisfactory convergence of the experimental and calculated values of the heat flow has been obtained. The results can be used in the development of thermal energy accumulators with n-tetradecane.

Microencapsulated PCM slurries’ dynamic viscosity experimental investigation and temperature-dependent prediction model

Microencapsulated PCM (mPCM) slurry is used both as a thermal storage medium and as a heat transfer fluid. The use of mPCM slurry as a working fluid in heat transfer systems requires knowledge of its rheological properties. In this study, experimental research results based on the mPCM product called Micronal® DS 5039 X were used. The research was carried out in the following range: a slurry temperature of 10–50 °C; a mass concentration of microcapsules in the slurry of up to 45%; two types of base liquid (water, an aqueous solution of propylene glycol); a shear rate of 3–130 s−1. This article presents a new temperature-dependent method of calculating the dynamic viscosity coefficient of microencapsulated PCM slurry. The average mean absolute percentage error (MAPE) for the investigated cases was MAPE = 14.19% and MAPE = 12.81% for the Micronal® DS 5039 X slurry in water and the aqueous solution of propylene glycol, respectively. Additionally, the validation of the model was based on the results of other authors’ research. Thus, it was found that 73.1% of the calculated viscosity results of mPCM slurry do not differ by more than 40% from other authors’ experimental results.

Ultrasonication assisted co-dispersion of nanostructured magnesium-lined paraffin wax and magnesium oxide in a heat transfer fluid for energy related applications

Magnesium-lined paraffin wax nanoparticles were prepared through probe ultrasonication, utilization of Tween 80 as surfactant and ionic interactions. These were co-dispersed with nanostructured magnesium oxide (0.6–2 vol%) in aqueous propylene glycol solution to obtain hybrid nanofluids. Magnesium-lined paraffin wax present in hybrid nanofluids underwent solid-liquid/liquid-solid transition between 45 °C and 62 °C during which thermal energy was absorbed/released, thereby increasing hybrid nanofluids' specific heat. The presence of magnesium oxide contributed to thermal conductivity enhancement of hybrid nanofluids, with a maximum of 20% for the one containing 2 vol% nanostructured magnesium oxide, attributable predominantly to the aggregation of primary nanoparticles as flower-like structure. Our data indicates augmentation of overall heat transfer coefficient with the utilization of hybrid nanofluid.

On the solvation of the phosphocholine headgroup in an aqueous propylene glycol solution.

The atomic-scale structure of the phosphocholine (PC) headgroup in 30 mol. % propylene glycol (PG) in an aqueous solution has been investigated using a combination of neutron diffraction with isotopic substitution experiments and computer simulation techniques-molecular dynamics and empirical potential structure refinement. Here, the hydration of the PC headgroup remains largely intact compared with the hydration of this group in a bilayer and in a bulk water solution, with the PG molecules showing limited interactions with the headgroup. When direct PG interactions with PC do occur, they are most likely to coordinate to the N(CH3)3+ motifs. Further, PG does not affect the bulk water structure and the addition of PC does not perturb the PG-solvent interactions. This suggests that the reason why PG is able to penetrate into membranes easily is that it does not form strong-hydrogen bonding or electrostatic interactions with the headgroup allowing it to easily move across the membrane barrier.

Experimental investigation on influence of microcapsules with PCM on propylene glycol rheological properties

This paper details an experimental study that was performed to investigate rheological properties of microencapsulated phase change slurry - mPCM (Micronal® DS 5039 X and ERGOLID EKO®- an aqueous solution of propylene glycol). Seven samples of mPCM slurry were prepared with different mass ratio of the Micronal® to the ERGOLID EKO®: 30:70, 40:60, 50:50, 60:40, 70:30, 80:20 and 90:10. The apparent viscosity-shear rate curves were obtained for spindle speed from 0.01 to 100 rpm (shear rate 0.0132 to 132.00 s-1 respectively). The steady state measurement of viscosity was carried out when the slurry reached constant temperatures, namely: 10.0; 15.0, 17.5, 20.0, 22.5, 25.0, 27.5, 30.0, 40.0 and 50.0°C. The apparent viscosity of slurries increases with the mPCM concentration in dispersion rises. Only the sample of 30% Micronal® may be considered as a Newtonian fluid within the test range. Increasing the shear rate ultimately causes apparent viscosity to decrease down to the Newtonian plateau, where it seems to be constant. The variation of the viscosity as a function of temperature and microcapsules concentration was accurately represented by a modified Vogel-Tamman-Fulcher equation at a mean absolute error (MAE) of 10.76%.

Innovative methodology based on the thermo-denuder principle for the detection of combustion-related solid particles or high boiling point droplets: Application to 3R4F cigarette and the Tobacco Heating System THS 2.2

Combustion-related solid particles are known to potentially have adverse effects on human health. In order to enhance further our understanding of how such particles trigger biological responses in humans, it is crucial to ensure that these particles are specifically collected, and are subsequently properly characterized. To separate the solid particles from an aerosol which contain also gases and liquid droplets, a methodology using a Dekati thermo-denuder operated at 300 °C was established. The current work addresses the performance of the method by assessing its average removal efficiency based on pre-determined aerosol average penetration values for model solid particles and liquid droplets. The solid particle average penetration, or the so-called transmission efficiency, was measured to be 79.4 ± 7.3% based on the aerosol wall losses. Although penetration is size-dependent, in the current work it was assumed that poly-disperse dry NaCl particles were a good surrogate to evaluate the equipment average wall losses of combustion-related fine solid particles. To assess the ability of the thermo-denuder to remove liquid droplets from aerosols, aqueous solutions of propylene glycol and glycerin were nebulized. The largest penetration value was measured to be 2.7 ± 1.0%. As a result, the methodology limit of detection was calculated to be 3.7% and the lower limit of quantification (LLOQ) 11.1%. Moreover, further experiments were conducted to ensure that liquid-coated solid particles could be distinguished from non-evaporated droplets to avoid data misinterpretation. To this end, ∼ 70 nm-NaCl particles were coated with glycerin reaching a size diameter of the order of a micron. The experiments showed that the layer of glycerin-coated NaCl was removed entirely when the aerosol passed through the thermo-denuder for the submicron size range. As an application of the methodology, the 3R4F reference cigarette mainstream smoke and Tobacco Heating System 2.2 (THS 2.2) mainstream aerosol were tested in the thermo-denuder. The data demonstrated that for 3R4F mainstream smoke, solid particles or high boiling point droplets were quantified far above the LLOQ. In contrast, for THS 2.2 mainstream aerosol, the penetration overlapped the LLOQ within the range of experimental uncertainty. In the current work, no combustion-related particles were detected or observed when using THS2.2, and this confirms former data published on this subject.

New Force Field Model for Propylene Glycol: Insight to Local Structure and Dynamics.

In this work we developed a new force field model (FFM) for propylene glycol (PG) based on the OPLS all-atom potential. The OPLS potential was refined using quantum chemical calculations, taking into account the densities and self-diffusion coefficients. The validation of this new FFM was carried out based on a wide range of physicochemical properties, such as density, enthalpy of vaporization, self-diffusion coefficients, isothermal compressibility, surface tension, and shear viscosity. The molecular dynamics (MD) simulations were performed over a large range of temperatures (293.15-373.15 K). The comparison with other force field models, such as OPLS, CHARMM27, and GAFF, revealed a large improvement of the results, allowing a better agreement with experimental data. Specific structural properties (radial distribution functions, hydrogen bonding and spatial distribution functions) were then analyzed in order to support the adequacy of the proposed FFM. Pure propylene glycol forms a continuous phase, displaying no microstructures. It is shown that the developed FFM gives rise to suitable results not only for pure propylene glycol but also for mixtures by testing its behavior for a 50 mol % aqueous propylene glycol solution. Furthermore, it is demonstrated that the addition of water to the PG phase produces a homogeneous solution and that the hydration interactions prevail over the propylene glycol self-association interactions.

Thermo-physical profile of zinc oxide nanoparticles dispersed in aqueous solution of propylene glycol

In this investigation zinc oxide (ZnO) nanoparticles were synthesized by precipitation method using Zn(CH3COO)2 as a starting material. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X- ray spectroscopy (EDX). These nanoparticles were dispersed in 10% aqueous solution of propylene glycol in various concentrations with the help of ultrasonicator to obtain nanofluids of different concentrations. Ultrasonic velocity (u), density (ρ) and viscosity (η) of these nanofluids were measured experimentally as a function of temperatures (T=303.15K, 308.15K and 313.15K). Using these experimentally measured values various acoustic parameters such as adiabatic compressibility (βad), intermolecular free length (Lf), relaxation time (τ), acoustic impedance (Z), free volume (Vf) and attenuation coefficient (α/f2) were evaluated with a view to investigate molecular interactions.

Investigation of Heat Exchange During Movement in a Horizontal Tube of an Aqueous Propylene-Glycol Ice Slurry

A test method for investigating the heat-transfer coefficient as a function of the concentration of ice crystals in an ice slurry, the ice slurry flow rate in a tube, and the tube heat-flow density was presented. The experimental results were given. Comparative tests were carried out with a single-phase aqueous propylene glycol solution of the same initial density as the liquid from which the ice slurry was prepared.

Experimental study of heat exchange and hydrodynamics at the laminar flow of nanocoolant based on propylene glycol and Al2O3 nanoparticles

An experimental study of heat transfer coefficient and pressure losses coefficient under the laminar flow of nanocoolants in the pipe was carried out. The relevance of the studies is related to the possibility of intensification of the heat transfer process when using nanofluids as heat transfer agents and coolants without modernizing the equipment. As the objects of the study, we used nanocoolants based on aqueous solutions of propylene glycol with the addition of Al 2 O 3 nanoparticles in the amount of 0.53 and 1.03 % by weight. A technology for the preparation of nanocoolants by a two-stage method is described. Results of the aggregate stability of nanoparticles in the coolant are presented. Thermophysical properties of nanocoolants, necessary for evaluating heat-transfer coefficient and coefficient of pressure losses, were estimated experimentally (viscosity and heat capacity) and theoretically (density and thermal conductivity) in temperature range of 253–313 K. A schematic of the original experimental installation for measuring heat-transfer coefficient and pressure losses coefficient in the pipe is represented. Results of the calibration experiment with the use of water as coolant are presented. Experimental values of heat-transfer coefficients and pressure losses coefficient under the forced laminar flow of nanocoolant in the pipe are given. It was shown that the mean lengthwise and local values of heat-transfer coefficients for the nanocoolant are larger than those for the base coolant. At the same time, an increase in heat exchange intensity is not proportional to the concentration of nanoparticles in the coolant. An increase in the losses of head at the addition of nanoparticles to the base coolant was demonstrated. The data obtained showed a possibility in principle to intensiy the heat transfer process under the forced motion of nanocoolant based on the aqueous solutions of propylene glycol and Al 2 O 3 nanoparticles in the heat exchange equipment of refrigeration systems.

On the structure of an aqueous propylene glycol solution.

Using a combination of neutron diffraction and empirical potential structure refinement computational modelling, the interactions in a 30 mol. % aqueous solution of propylene glycol (PG), which govern both the hydration and association of this molecule in solution, have been assessed. From this work it appears that PG is readily hydrated, where the most prevalent hydration interactions were found to be through both the PG hydroxyl groups but also alkyl groups typically considered hydrophobic. Hydration interactions of PG dominate the solution over PG self-self interactions and there is no evidence of more extensive association. This hydration behavior for PG in solutions suggests that the preference of PG to be hydrated rather than to be self-associated may translate into a preference for PG to bind to lipids rather than itself, providing a potential explanation for how PG is able to enhance the apparent solubility of drug molecules in vivo.