Thermophysical Properties Of Water Research Articles

Effect of Magnetic Field on Optical Density of Distilled Water

Water is considered as the working fluid of wet steam turbine units. The importance of a purposeful change in the thermophysical properties of water used for energy needs is indicated. A reagent-free method (transverse magnetic field of permanent magnets) of influence on water is proposed. Literature data on currently available papers dedicated to the study of water properties is presented. It is shown that the mechanisms of influence of external physical fields on the physicochemical and thermophysical properties of water have not been elucidated as of now. It is emphasized that the properties of distilled water during exposure and after exposure to physical fields are even less studied. The currently existing contradictions between theoretical ideas about the properties of water and experimental results are considered. It was found that currently there are no correct methods and equipment capable of indicating changes in water properties in real time. As a solution, the equipment and method of analyzing the optical density of distilled water is proposed. The shortcomings of most existing experimental works on the study of the influence of physical fields on the optical density of water are analyzed. The requirements for devices intended for measuring the optical density of distilled water are formulated. A stand was made and experimental work on the study of the dependence of the optical density of distilled water on the induction of a magnetic field that affects it was carried out. It is proved that the magnetic field affects the optical density of distilled water in the infrared range of wavelengths both in the direction of increase (4.1%) and in the direction of decrease (1.7%) depending on the induction of the magnetic field and the speed of water flow through the working section of magnetization device. A hypothesis explaining the obtained result is proposed.

Figures-of-Merit Analysis Using the Thermophysical Properties of Water and Ethylene Glycol Based Reduced Graphene Oxide/Nanodiamond Hybrid Nanofluids

The water and ethylene glycol based stable rGO/nanodiamond hybrid nanofluids were prepared and used for thermophysical properties analysis. The thermophysical properties were measured experimentally at various particle loadings from 0.2% to 1.0% and various temperatures ranging from 20 to 60 °C. From the measured thermophysical properties the figures-of-merit were analyzed by assuming constant heat flux and turbulent boundary conditions by using different models, and also by assuming the hybrid nanofluids flows through a tube. Results indicate that the thermal conductivity of water and ethylene glycol based hybrid nanofluids at Φ = 1.0% vol. is enhanced about 27.87% and 18.8% at 60 °C; viscosity of water and ethylene glycol based hybrid nanofluids at Φ = 1.0% vol. is also enhanced by 72.15% and 86.62% compared to their base fluids at 20 °C. The density is also increased with an increase of particle loadings, whereas, the specific heat is decreased with a rise of particle loadings. Experimental thermophysical properties are fitted into regression equations by using multi linear regression method. The figures-of-merit of all the prepared hybrid nanofluids show its value is less than one under the used particle loadings and temperatures.

THERMAL CONDUCTIVITY, RHEOLOGY AND ELECTRICAL CONDUCTIVITY OF WATER AND ETHYLENE GLYCOL BASED NANOFLUIDS WITH COPPER AND ALUMINUM PARTICLES

Nanoparticles are mesoobjects that occupy an intermediate position in size between ordinary molecules and macroscopic particles. Suspensions with nanoparticles, called nanofluids, are also specific mesoscopic suspensions. Today it is known that their thermophysical and mechanical properties are not described by classical theories. The unusual properties of these dispersed fluids make them extremely popular in a wide variety of applications. However, successful use of nanofluids involves the prediction of their properties, which in turn requires systematic studies. This paper presents an experimental study on the thermophysical properties of water and ethylene glycol based nanofluids with aluminum and copper particles. The thermal conductivity, rheology and electrical conductivity of nanofluids were systematically studied. The weight concentration of nanoparticles varied from 2.5 to 20%. It was shown that the thermal conductivity of these nanofluids significantly exceeds that of nanofluids with oxide particles. Its higher values are determined by the size of the nanoparticles and the thermal conductivity of the base fluid. The nanofluids studied are either pseudoplastic or viscoplastic. Their rheology is determined by the concentration and size of nanoparticles. The smaller the size of nanoparticles and the higher their concentration, the more likely the change in rheology is. Correlation curves were constructed for the rheological parameters of nanofluids versus the concentration and size of nanoparticles. It was found that the electrical conductivity of nanofluids increases almost linearly with increasing nanoparticle concentration and strongly depends on the nanoparticle size. The electrical conductivity mechanisms of nanofluids were discussed. The speed of sound in a nanofluid and its dependence on particle size were measured.

Dynamic modelling of ice‐based thermal energy storage for cooling applications

The development of accurate dynamic models of thermal energy storage (TES) units is important for their effective operation within cooling systems. This paper presents a one-dimensional discretised dynamic model of an ice-based TES tank. Simplicity and portability are key attributes of the presented model as they enable its implementation in any programing language which would, in turn, facilitate the simulation and analysis of complex cooling systems. The model considers three main components: energy balance, definition of the specific heat curve, and calculation of the overall heat transfer coefficient. An advantage of the model is that it can be adapted to other types of TES units employing phase change materials. The modelling approach assumes equal flow and temperature distribution in the tank and considers two internal tubes only to represent the whole tank—significantly reducing the number of equations required and thus the computation time. Thermophysical properties of water during the phase change and of the heat transfer fluid are captured. The ice-based TES tank model has been implemented in MATLAB/Simulink. A good agreement between simulation results and experimental data available in the literature has been achieved—providing confidence in the validity of the mathematical model.

Heat transfer characteristics of water under supercritical conditions

The paper deals with the problems of describing heat transfer modes in a turbulent flow of supercritical water based on generalization of known experimental data for vertical round tubes. Due to the danger of overheating of heat transfer surfaces, special attention is paid to modes with deteriorated heat transfer. Later, the authors developed a universal model that includes the well-known Dittus–Boelter correlation with corrections for changes in the thermophysical properties of water with temperature and the effect of thermal acceleration occurring in the flow. It is shown that the variation of the coefficients in the correction functions allows us to take into account individual features of changes in characteristics of the process in modes with deteriorated heat transfer. Three forms of displaying the modes of heat transfer to water of supercritical parameters with conditional boundaries of the modes of normal, improved and deteriorated heat transfer are proposed. The estimates of the limiting heat flux obtained in this paper for normal modes are compared with the data of other authors.

Nonlinear thermal radiation and activation energy features in axisymmetric rotational stagnation point flow of hybrid nanofluid

The present study particularizes the effects of nonlinear thermal radiation and the novel accepts of activation energy in the axisymmetric rotational stagnation point flow of hybrid fluid. Thermophysical properties of water and CWCNT/MWCNT are used for base fluid and nanoparticles respectively. The modeled partial differential equations are reduces to system of ordinary differential equations. The resulting equations are integrated numerically and the impact of involved parameters on velocity, temperature and nanoparticle concentration presented graphically. The tabular values for local Nusselt numbers in case of linear and nonlinear thermal radiation and the Sherwood number with and without activation energy are documented. It is observed that concentration of nanoparticles reduces with activation energy and increasing the solid volume fraction of SWCNT as well as MWCNT nanoparticles. Moreover the axial velocity increases while secondary velocity decreases by increasing the rotation parameter.

Implementation of magnetic field force in molecular dynamics algorithm: NAMD source code version 2.12.

The external fields, such as the magnetic force, have made advances in many industrial and biotechnology applications during the past century, although the changes in the structure of materials under the impact of the electromagnetic fields have not entirely been clear yet. The molecular simulation technique by providing extensive data from the configuration and orientations of the atoms is becoming the effective useful tool for scientists in a wide range of research areas. This paper presents an extended velocity Verlet algorithm inside the Nanoscale Molecular Dynamics (NAMD) package that enhances the NAMD features with the capability to compute the magnetic field force. We described how this novel feature has been implemented inside the package. Moreover, the results are reported for the rotation of a charged particle, and the thermo-physical properties of water in the presence of a magnetic field confirming how this developed NAMD source code provides accurate measurements compared with other available data.

The effect of droplets thermophysical properties on turbulent heat transfer in a swirling separated mist flow

The numerical investigation of the effect of the swirl number and the thermophysical properties of water, ethanol, and acetone droplets on the particle scattering, turbulence modification and heat transfer in a droplet-laden flow is carried out. The set of 3D steady-state Reynolds-averaged Navier–Stokes (RANS) equations for the two-phase flow is utilized. The dispersed phase is modeled by the Eulerian approach. The flow swirling significantly shortens the length of the recirculation zone (up to two times in comparison with non-swirling flow at swirl number S = 0.5) for all types of the studied liquids. The highest value of heat transfer rate is obtained for the ethanol droplets (up to 10%), and the lowest one is obtained for the acetone droplets (up to 50%), both in comparison with water droplets. The swirling of the turbulent mist flow causes heat transfer enhancement (more than 1.5 times in comparison with the non-swirling droplet-laden flow). In the swirling flow, the value of the volume fraction of the dispersed phase has a maximum in the axial region of the pipe, and further in the direction of the wall its value is very small. The effect of heat transfer enhancement weakens with increasing Reynolds number of the flow. A region without droplets appears in the wall zone of the swirling two-phase flow, and the region is largest for acetone droplets.

Energy Efficient Processing of Geotermal Water for Energy-Heating Objects of the Building Industry

Due to the energy crisis in Ukraine, the problem of significant increase in the efficiency of production, transportation and use of energy is of particular importance. Considering the significant role in energy supply of the country, the issues of efficient use of heat energy in all areas of these systems are solved: generation for heating water or for steam generation; transportation to the consumer, as well as when using it by the consumer. On the heat exchange surfaces of the systems, scale occurs, which leads to deterioration of heat and mass transfer processes and heat energy indices [6]. This affects the overall performance of the process. In this paper, the question of determining the parameters of an electromagnetic field in the process of treatment of pure water is solved and physical models of the change of the structure of pure water after treatment in the electromagnetic field and the change in the nature of its interaction with different surfaces are developed. To improve the efficiency of the system perform preliminary cleaning and softening water before feeding it to the heat pump by the method of processing it in fields of constant current and in the field of permanent magnets. Next, filtration and water treatment in the field of electromagnets with certain parameters of high frequency of electric current and field induction are carried out. The scientific principles of changes in structural and thermophysical properties of water, ecological and technical technologies, which include the implementation of its basic principles, in which environmental and anthropogenic factors perform a functionally unifying role, are developed.

Fabrication and characterization of phase change nanofluid with high thermophysical properties for thermal energy storage

The thermophysical properties of water were modified by adding MWCNT and the organic PAAS. The effects of MWCNT and PAAS on supercooling degree and phase change characteristics of water were experimentally studied. The results showed that the length of the water phase change platform increases by 41% and decreases by 19.6% when concentration of PAAS is from 0 wt% to 2 wt% and 2 wt% to 5 wt%, respectively; The maximum supercooling degree declines up to 95% by adding MWCNT with the variations of particle size and concentration. The interfacial free energy at MWCNT outer diameter of 8–15 nm is approximately 1.75 and 2.14 larger than particle size of 20–40 nm and >50 nm. The temperature homogeneity of composite material is better than that of DW in application test, and the increased percentage of cold discharge time is less than that of the small dose experiments. The cold discharge time of the optimum PCM at top cold plate and other three positions are 81.8% and 35.3% higher than those of DW.

Hotspot Analysis of Double-Layer Microchannel Heat Sinks

ABSTRACTThe performance of double-layer microchannel heat sinks are evaluated comparatively for the parallel flow, counter flow, and transverse flow configurations with and without hotspots as heating condition. Conjugate heat transfer analysis is performed by solving three-dimensional Navier–Stokes and energy equations using a finite volume solver. The flow is considered to be steady, incompressible, and laminar. Functional relations between the thermophysical properties of water and temperature are developed and used for numerical calculations with variable fluid properties. The thermal resistances, maximum temperature increase at the hotspots, temperature variation among the hotspots, and pressure drops are evaluated for the three heat-sink designs with two hotspot schemes (single hotspot at the center of the heat sink and multiple hotspots distributed uniformly at six peripheral locations). For the single-hotspot case, the parallel flow heat sink exhibited the lowest thermal resistance and temperature rise at the hotspot. For all the six multiple hotspot cases, the transverse flow heat sink exhibited the lowest thermal resistance and temperature variation among the hotspots.

Dual solutions for nanofluid flow past a curved surface with nonlinear radiation, Soret and Dufour effects

Present work explores the numerical study of heat and mass transfer in nanofluid flow past a curve shaped stretchable (linearly/nonlinearly) geometry. The impact of Lorentz force caused by magnetic field, nonlinear radiation due to high temperature near the surface, frictional heating by virtue of viscous dissipation and cross diffusion by virtue of concentration and temperature differences are pondered while formulating the problem. The thermo physical properties of water and silver nanoparticles are used for calculations. Hamilton-Crosser model is considered for effective thermal conductivity of nanofluid. Shooting method and R.K. fourth order algorithm are adopted to solve the nonlinear coupled differential equations of the problem. The concentration, temperature and velocity fields are studied graphically for distinct values of flow parameters. Numerical values also calculated to know the impact of same parameters on mass and heat transfer coefficients. Results depict that mass and heat transfer performance in the flow via nonlinear curved surface is better when compared with the flow over linearly curved surface. As usually Eckert number and temperature ratio parameter boosts the fluid temperature in the present flow situation also.

An R-package for water and steam properties for scientific and general use

The International Association for the Properties of Water and Steam (IAPWS) develops formulations for the calculation of thermophysical properties of water as a function of different combinations of temperature, density, pressure, enthalpy, and entropy. These properties are useful for scientists and nuclear, chemical, and mechanical engineers who analyse experimental data or are involved with projects and equipment development, like heat exchangers, turbines, or nuclear power reactors. The IAPWS-95 formulation solves the fundamental equation of Helmholtz free energy as a function of temperature and density. This paper gives a description of how these equations are solved and exemplifies the use of a package developed for the free platform R. The IAPWS95 package was developed to help users to get access to the IAPWS-95 formulation in a free software environment which is growing exponentially. Transport properties were programmed using other IAPWS releases. The examples consider the uncertainty analysis of thermal parameters of a nuclear power reactor and the preparation of tables and graphs of water properties.

Releases from the International Association for the Properties of Water and Steam for calculating properties of steam, ordinary and heavy water substance and seawater

An overview of the developed in recent years documents from the working group on thermophysical properties of water and steam from the International Association for the Properties of Water and Steam (www.iapws.org) is given. Not only brief description of each Formulation is given, but also information about relationship between them is provided. Most of listed documents are international and Russian state standards.

Analytical Technique for Estimating the Termophysical Properties of Hybrid Nanofluids

Over the past years, the development of functional heat transfer fluids by compounding different substances or different phases of matter (solid, liquid, or gas) has raised increasing interest in view of their potential applications in technologies. In particular, the nanofluids in which the solid particles (<100 nm or smaller) are incorporated as the dispersed phase in the suspensions, are currently focus of great attention because of their perspective potentials as high-performance heat transfer fluids. The potential advantage of utilizing the nanofluid lies mainly in its drastic increase in the thermal conductivity. This paper presents a study of the thermophysical characteristics of some nanofluids and their hybrids. General correlations for the effective thermal conductivity and viscosity of nanofluids are used for this analysis. Regarding the importance of thermophysical properties of water based drilling fluids, the effects of insertion of two oxides in an alumina-water nanofluid on the thermal conductivity, viscosity and density of distilled water were investigated. According to the results, viscosity and density of the nanofluids increased with the concentration. At high concentrations, the least increase in the viscosity of distilled water by adding the nanomaterials is related to H2 (8.2% increase at 1.0 wt.%). As the results show, increase in the density of distilled water by adding the nanomaterials is insignificant, that in the worst case it did not exceed 0.9%. The least increase in the density of base fluid at high concentrations was for H1.

Natural convective heat transfer characteristics of Rayleigh-Benard convection of Al<sub>2</sub>O<sub>3</sub>-water nanofluids

Transient three-dimensional numerical computations are implemented to clarify the natural convective heat transfer characteristics of the Rayleigh-Benard convection of Al2O3-water nanofluids induced in a shallow vertical cylindrical enclosure. The thermophysical properties of nanofluids, assumed to be a single-phase fluid in the numerical computations, are estimated using the experimental correlation equations reported by Khanafer and Vafai (2011). When the average Nusselt numbers of nanofluids are plotted against the Rayleigh number defined by the thermophysical properties of water, computations for four different volume fractions of nanoparticles were below the average Nusselt number curve experimentally reported by Silveston (1958). The diagram also reveals that the increase of nanoparticles in the base fluid delays the generation of Rayleigh-Benard convection. However, the average Nusselt numbers of nanofluids almost agreed with the average Nusselt numbers of Silveston without depending on the volume fraction of nanoparticles when plotted against the Rayleigh number defined by the thermophysical properties of nanofluids. Thus, the natural convection heat transfer rates of Al2O3-water nanofluids can be considered to be similar to the general fluids reported by Silveston as long as experimental thermophysical properties are employed.

Experimental investigation of the thermal hydraulics of supercritical water under natural circulation in a closed loop

The thermal hydraulics of supercritical water under forced-, mixed convection and natural circulation conditions is not fully understood. In order to study the thermal hydraulic behaviour of this fluid under natural circulation conditions a small size, closed experimental loop has been designed and built. The thermal hydraulic phenomenon occurring in the loop can be measured by thermocouples mounted onto the outer surface of the heated tube wall, absolute and differential pressure transducers and a flow meter; moreover, simultaneously can be visualized by neutron radiography techniques. This paper describes the loop itself, the process of the experiment with the measurement techniques, the data acquisition system applied and the results got during the first measurement series. Based on the results of the first measurement series, it was found that the measured part of the steady state characteristic is independent from the system pressure. A slight dependence of steady state characteristic on the inlet temperature can be identified: the higher the inlet temperature the higher the mass flow rate. The total pressure drop and its components seem to be independent from the system pressure but strongly dependent on the inlet temperature due to the influence of bulk-fluid temperature on the relevant thermophysical properties (density and dynamic viscosity). The pressure drop due to acceleration of flow found to be negligible next to the two dominant components, the pressure drop due to frictional resistance and due to gravity. The coupled evaluation of the radiographic images and the thermophysical properties of water have shown that the main driving force behind the decrease of the neutron attenuation is the decreasing water density as the bulk-fluid temperature increases. The reverse of this relationship could be exploited during the validation of future Monte Carlo simulations.

On Calculating Heat Transfer and Pressure Drop of Supercritical-Pressure Coolants

Specific features of thermophysical properties of single-phase supercritical-pressure (SCP) coolants and typical ranges of their thermodynamic state that determine heat-transfer regularities are presented. A brief analysis of the existing concepts on SCP-coolants heat transfer under turbulent flow in tube is given. Typical features of normal and deteriorated heat-transfer regimes are described. The simple classification of deteriorated heat-transfer regimes at high heat loads that make it possible to distinguish the causes and appraise a degree of heat-transfer deterioration danger is proposed. The results from the studies of the hydraulic-resistance structure under the regimes of normal and deteriorated heat transfer are considered and the conditions, when a one-dimensional (1-D) (homogeneous) flow model can be used in hydraulic calculations, are revealed. Using sounding measurements data, the interrelation between heat-transfer deterioration and radical changes in the averaged turbulent flow structure due to fluid thermal acceleration and Archimedes forces effects is analyzed. The recommendations on calculating normal heat transfer with an account of refined standards on thermophysical properties of water and carbon dioxide are presented. The review and analysis of the existing criteria for forecasting heat-transfer deterioration and assessing the boundaries of the normal heat-transfer range are given, and the correlations for describing deteriorated heat transfer are presented.

Thermo-physical properties of water and ethylene glycol mixture based SiC nanofluids: An experimental investigation

The mixture of water and ethylene glycol (EG) is a kind of traditional heat transfer fluids commonly used in many energy systems to retain the good heating (or cooling) ability of water, as well as broadening the operating temperature range for energy applications. Therefore, the enhancement of water/EG mixture thermo-physical properties by using nanoparticles would be beneficial for the performance of the energy systems. With the purpose of filling the research gap in the literatures, this paper presents experimental data of thermal conductivity and viscosity properties of water/EG-based SiC nanofluids. It was found that the thermal conductivity of nanofluids increased with the volume fraction, and the highest thermal conductivity enhancement was found to be 33.84% for 1.0vol% nanofluid at 20°C. The prepared SiC nanofluids behaved Newtonian behavior and the viscosities decreased with the increasing temperature. In addition, the heat transfer benefits suggested that the water/EG-based SiC nanofluids had potential applications for energy systems, which indicated promising capability of this kind of nanofluids for further heat transfer characteristics investigation.

New RELAP5-3D Lead and LBE Thermophysical Properties Implementation for Safety Analysis of Gen IV Reactors

The latest versions of RELAP5-3D©code allow the simulation of thermodynamic system, using different type of working fluids, that is, liquid metals, molten salt, diathermic oil, and so forth, thanks to the ATHENA code integration. The RELAP5-3D©water thermophysical properties are largely verified and validated; however there are not so many experiments to generate the liquid metals ones in particular for the Lead and the Lead Bismuth Eutectic. Recently, new and more accurate experimental data are available for liquid metals. The comparison between these state-of-the-art data and the RELAP5-3D©default thermophysical properties shows some discrepancy; therefore a tool for the generation of new properties binary files has been developed. All the available data came from experiments performed at atmospheric pressure. Therefore, to extend the pressure domain below and above this pressure, the tool fits a semiempirical model (soft sphere model with inverse-power-law potential), specific for the liquid metals. New binary files of thermophysical properties, with a detailed mesh grid of point to reduce the code mass error (especially for the Lead), were generated with this tool. Finally, calculations using a simple natural circulation loop were performed to understand the differences between the default and the new properties.