International Association For The Properties Of Water And Steam Research Articles

Numerical modeling of the long-term poromechanical performance of a deep enhanced geothermal system in northern Québec

This study numerically investigates the thermo-poromechanical effects in a Canadian geothermal reservoir caused by long-term fluid production and injection. Using finite element modeling, it explores pore pressure diffusion and thermal dynamics, incorporating both the geological structure of the rock mass and faults. The simulations utilize the IAPWS (International Association for the Properties of Water and Steam) equations to model fluid density and viscosity, ensuring realistic representations of heterogeneous pressure fields. The system replicates a doublet configuration within a faulted zone, featuring two hydraulically stimulated fractures. The primary aim is to assess the likelihood of fault reactivation under varying in-situ stress conditions over a 100-year geothermal operation. Results show that stress distribution is largely influenced by thermal stresses along the fluid circulation pathway, with fluid velocity and temperature gradients affecting reservoir stability. Minimal pore pressure changes highlight the dominant role of thermal stresses in controlling fault behavior. The analysis indicates no potential for fault reactivation, as slip tendency values remain below the critical threshold, even when accounting for reduced mechanical properties using the Hoek-Brown criterion. Thermal effects continue to influence the surrounding rock throughout the operational period, suggesting that the reservoir maintains mechanical stability conducive to sustained geothermal production and injection. These findings provide valuable insights into the long-term safety and behavior of geothermal reservoirs, offering important implications for future geothermal energy development and management strategies.

Development of thermo-physical property database and code of fusion materials for CFETR blankets

The conceptual design of China Fusion Engineering Test Reactor (CFETR) has been completed and is currently in the engineering design phase. In this paper, focusing on three categories of candidate blanket designs and divertor designs, the selection schemes for materials of plasma-facing components, solid structure, tritium breeding materials, neutron multiplier, coolant, and divertor were extracted. Thermo-physical property data was compiled to form a material thermo-physical property database, named Thermo-physical Property Database (ThePD), which is the first advanced thermo-physical database for materials of CFETR blankets. Besides, the callable code was generated, which can be directly applied in the system code for the blanket. Based on internationally available database from National Institute of Standards and Technology (NIST) and similar software AP1700, the correctness of the data and the transitional analysis of regions designed by International Association for the Properties of Water and Steam (IAPWS) were verified. Using the thermal-hydraulic system analysis code, integrated validation was performed for the validated thermo-physical property data and code, demonstrating the applicability and accuracy of the data. ThePD is conducive to addressing the issue of incomplete thermo-physical property data faced by blanket design and safety analysis software for CFETR, and it can fill this gap.

Prediction of shock heating during ultrasound-induced bubble collapse using real-fluid equations of state

Numerical simulations of collapsing air bubbles considering complex and more accurate equations of state (EoS) for estimating the properties of both the liquid and gas are presented. The necessity for utilising such EoSs in bubble collapse simulations is illustrated by the unphysical (spurious) liquid temperature jump formed in the vicinity of the bubble-air interface when simplified EoSs are used. The solved fluid flow equations follow the mechanical equilibrium multiphase method of Kapila. The solver is coded in the AMReX platform, enabling high-performance computation with parallel processing and Adaptive Mesh Refinement for speeding up simulations. It is initially demonstrated that the frequently used Stiffened Gas (SG) EoS overpredicts the liquid temperature at high compression. More sophisticated EoS models, such as the International Association for the Properties of Water and Steam (IAPWS), the Modified Noble Abel Stiffened Gas (MNASG) and a modified Tait EoS introduced here, are also implemented into the flow solver and their differences are highlighted for bubble collapse cases for the first time. Subsequently, application of the developed model to cases of practical interest is showcased. More specifically, simulations of bubble collapse near a solid wall are presented for conditions simulating shock wave lithotripsy (SWL). It is concluded that for such cases, a maximum increase of 25 K of the liquid temperature in contact along the solid wall is caused during the collapse of the air bubble due to shock wave focusing effects. It is also highlighted that the maximum liquid heating varies depending on the initial bubble-wall stand-off distance.

Water Chemistries of an Electrical Generator Cooling System

At some thermal and nuclear power plants, water is used for cooling the electric generator stator windings with copper used as their main structural material. During operation of such cooling systems, certain problems are encountered as a consequence of copper corrosion and deposits formed on the inner surfaces of stator winding cooling channels. Inadequate quality of water circulating in the tubes is one of the factors causing the corrosion to occur. The article outlines the main stages of the corrosion and deposit formation processes: copper surface oxidation with formation of copper ions, formation of oxides on the metal surface, partial transfer of oxides from the metal surface into water, and carryover of oxides from one metal surface area to another. Four basic water chemistries for electric generator cooling water systems developed by the International Association for the Properties of Water and Steam (IAPWS) are discussed. These water chemistries are based on using low-oxygen (20–50 μg/dm3) and high-oxygen (2000 μg/dm3) treatments. The article gives the basic standardized and monitored indicators characterizing the water quality in electric generator cooling systems for the water chemistries developed by the IAPWS. Apart from the water chemistries described in the IAPWS technical document, the article presents data on the advantages of using reducing agents for cooling water treatment, e.g., hydrogen in concentrations ranging from 30 to 60 μg/dm3.

Improved and Always Improving: Reference Formulations for Thermophysical Properties of Water

This Review presents the state of knowledge of the thermophysical properties of water in all its phases and the reference formulations that provide standardized, recommended values of these properties for science and industry. The main focus is the standard formulations adopted by the International Association for the Properties of Water and Steam (IAPWS), but some properties are covered for which IAPWS has not yet adopted recommendations. It is emphasized that, despite many advances over the last 100 years, there is room for further improvement, and current weaknesses and opportunities for advancing knowledge are discussed. Particular attention is given to the formulation for thermodynamic properties of fluid water known as IAPWS-95, which is planned to be replaced in the coming years. Additional topics include properties of heavy water and seawater and the growing ability of molecular modeling to provide properties at conditions where experimental measurements are difficult or inaccurate.

A new single equation of state to describe the dynamic viscosity and self-diffusion coefficient for all fluid phases of water from 200 to 1800 K based on a new original microscopic model

A microscopic model, which is able to simultaneously describe the dynamic viscosity and the self-diffusion coefficient of fluids, is presented. This model is shown to emerge from the introduction of fractional calculus in a usual model of condensed matter physics based on an elastic energy functional. The main feature of the model is that all measurable quantities are predicted, depending on external parameters in a non-trivial way (e.g., the experimental set-up geometry, in particular the sample size). On the basis of an unprecedented comparative analysis of a collection of published experimental data, the modeling is applied to the case of water in all its fluid phases, in particular in the supercooled phase. It is shown that the discrepancies in the literature data are only apparent and can be quantitatively explained by different experimental configurations (e.g., geometry, calibration). This approach makes it possible to reproduce the water viscosity with a better accuracy than the 2008 International Association for the Properties of Water and Steam (IAPWS) formulation and also with a more physically satisfying modeling of the isochors. Moreover, it also allows the modeling within experimental accuracy of the translational self-diffusion data available in the literature in all water fluid phases. Finally, the formalism of the model makes it possible to understand the “anomalies” observed on the dynamic viscosity and self-diffusion coefficient and their possible links.

Transport properties of real moist air, dry air, steam, and water

This paper presents the ASHRAE transport properties model for moist air as a "real-gas mixture" employing a modification of the mixing model of Vesovic and Wakeham. It uses the latest research from the International Association for the Properties of Water and Steam (IAPWS), the International Union of Pure and Applied Chemistry (IUPAC), and the National Institute of Standards and Technology (NIST). The modification represents an improvement and consists in an adjustment of the underlying Vesovic-Wakeham model to experimental data in accordance with the composition of the mixture moist air. The model allows the calculation of viscosity and thermal conductivity in the validity range with total pressures from 0.01 kPa to 10 MPa, temperatures from −70 to 300 °C, and humidity ratios from 0 to 10 kgw/kga. The model has been used to generate transport property tables for moist air and for H2O at saturation states for the Psychrometrics Chapter in the 2021 ASHRAE Handbook Fundamentals. This work summarizes the results of the ASHRAE Research Project 1767 (RP-1767).

Thermodynamic and Thermophysical Properties of Dry Air by Using Cubic Peng-Robinson EoS for Gas Mixtures

Dry air is one of the most used gases in industrial and technological applications. In dry air thermodynamic property calculations, it is usually ideal gas EoS is used. The basic reason for this is the simplicity of using ideal gas EoS. For most applications, it might be sufficient, but when applications with higher pressure zones are considered error level will increase. An equation of state with better accuracy of thermodynamic properties will be required for extreme cases. Therefore, Peng-Robinson cubic equation of states (EoS) for dry air is considered in this paper. Set of computer programs were developed in java language in order to calculate thermodynamic and thermophysical properties of dry air and compared with perfect gas EoS and EoS developed by The International Association for the Properties of Water and Steam (IAPWS).

Use of the international association for the properties of water and steam (IAPWS) formulations, IAPWS-95 & IAPWS-IF97: Making of Mollier diagram and T-s diagram of water and steam

It is very important to correctly calculate the thermodynamic properties of water and steam needed for design and operation of the main equipment of the power industry such as boilers and steam turbines. On the other hand, the Mollier diagram and T-s diagram of water and steam are widely used to study or review thermodynamic cycles as well as expansion processes of steam turbines and steam power equipment in the power industry. Presented in this paper are the method and procedures to exactly construct the diagrams. The diagrams involve several lines, including the saturation line, and constant pressure, temperature and vapor fraction lines. In the paper, a method is proposed for correctly calculating other thermodynamic properties of saturated liquid water and water vapor in saturation line of near-critical region by using the basic equation of region 3 of IAPWS-IF97 and iteration. Then, the procedures to plot the lines are presented by combining the method with IAPWS-95 and IAPWS-IF97, and the Mollier diagram and T-s diagram made in MS-Excel are shown. The method and procedures in the paper can be used not only in making the Mollier diagram, T-s diagram and steam tables, but also in accurately calculating the thermodynamic properties of saturated liquid water and water vapor.

The Ionization Constant of Water at Elevated Temperatures and Pressures: New Data from Direct Conductivity Measurements and Revised Formulations from T = 273 K to 674 K and p = 0.1 MPa to 31 MPa

Experimental values for the ionization constant of water, pKw,m, from T = 373 K to T = 674 K and from p = 5.75 MPa to p = 31.15 MPa, have been derived from direct measurements of the electrical conductivity of very pure water at the University of Guelph, the University of Delaware, and the Oak Ridge National Laboratory using high-precision high-temperature flow-through AC electrical conductance instruments based on the design by Wood and co-workers [J. Phys. Chem. 99, 11612 (1995)]. The results compare well with published high-temperature potentiometric and calorimetric studies up to 573 K and are consistent with the 1981 and 2006 IAPWS (International Association for the Properties of Water and Steam) pKw,m formulations to within better than 0.1 pK units up to 598 K and to better than 0.2 pK units at 623 K. Above 623 K, the 2006 and 1981 IAPWS formulations showed systematic deviations from the new results, which reached two and five orders of magnitude near the critical point, respectively. Based on these conductivity studies and critically evaluated literature data, revised parameters for the Marshall–Franck and Bandura–Lvov equations of state are reported, which reproduce the experimental data with standard uncertainties u(pK) = 0.018 and u(pK) = 0.016, respectively, over the experimental temperature range at water densities from 1.00 g cm−3 to 0.20 g cm−3, which corresponds to T = 373 K–674 K from psat to p = 31 MPa, and over the range T = 273 K–373 K at p = 100 kPa. These new experimental conductivity results are the most accurate values to be reported under near-critical conditions for densities between 0.50 g cm−3 and 0.20 g cm−3.

Нормирование качества воды и пара при полиаминном (хеламинном) водно-химическом режиме на тепловых электростанциях с парогазовыми установками

Complex chemicals that include filming amines have been widely used for water chemistry control at combined cycle power plants during the last 10-20 years. Use of these complex chemicals has resulted in: lower rates of material corrosion and deposition on heat transfer surfaces, removal of deposits from heat exchange surfaces and turbine blades, and simplification of layup procedure of heat recovery steam generators. The chemicals under trademark Helamin are the first polyamine-based complex chemicals that have been in use at Russian combined cycle power plants since 2004. Water chemistry with the use of these chemicals is called Helamin treatment. If other types of polyamines (e.g., Epuramin, Vtiamin etc.) are used for chemistry control, then the water chemistry is called polyamine treatment. In spite of the wide experience with polyamine treatment at combined cycle power plants, guidelines on water and steam purity that available for this treatment need significant revision. Domestic guidelines are mostly associated with certain types of complex chemicals and sometimes are out-of-date, requiring amendment and revision. The first international technical guidance on the use of complex chemicals with filming amines for water chemistry control at drum-type and combined cycle power plants (Application of Film Forming Substances in Fossil, Combined Cycle, and Biomass Power Plants) was issued in 2016 (re-issued in 2019) by International Association for the Properties of Water and Steam (IAPWS). However, water/steam purity target values used in this guidance are based on reducing and oxidizing all- volatile treatments (AVT(R) and AVT(O) respectively), which do not account for all features associated with filming amine treatment. In this work, development of water/steam target values for treatment with complex chemicals accounts for norms used in previously issued complex chemical treatment guidelines as well as in existing AVT(R) and AVT(O) guidelines. These target values take into account process flow diagrams of power-generating units and presence/absence of copper-based alloys in condensate/feed water train. Comparison of chemical monitoring results and target values from plant operational guidelines with those presented in this work has been performed for three different combined cycle power-generating units. The results of the work indicate that the suggested water/steam purity target values, on the whole, are either in line with, or stricter than, the respective values from plant operational guidelines of the surveyed units. Average water/steam chemistry values measured during more than one year of base-load operation of three combined cycle power plants with different process flow diagrams and materials, are within suggested target values.

Fast methods of Debye-Hückel limiting slopes calculation and low-temperature extrapolation based on IAPWS equation of state of water

An accurate approximation for the Debye-Hückel limiting slopes based on the IAPWS (the International Association for the Properties of Water and Steam) equations for water was proposed. It is valid for T=273.15−523.15K and p=0−100MPa and uses one self-consistent formula and parameters set for all six coefficients. It uses a special extrapolation procedure for values below 273.15 K that is not dependent on equations of state for supercooled water and can be applied down to 173.15 K. The computations took only about 1% of the time that was required for the computations based on original IAPWS equations. Usage of the IAPWS-IF97 (IAPWS Industrial Formulation 1997) equation instead of the IAPWS95 equation for the water density is also discussed. The developed procedure was also applied to other popular equations for Debye-Hückel coefficients (by Archer and Wang and by Bradley and Pitzer). Tabulated IAPWS95 based values for the Debye-Hückel limiting slopes for T=273−723K, p=0−100MPa and their extrapolation down to 173 K are given.

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.

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.

Cycle water chemistry based on film forming amines at power plants: evaluation of technical guidance documents

Efficiency and reliability of the equipment in fossil power plants as well as in combined cycle power plants depend on the corrosion processes and deposit formation in steam/water circuit. In order to decrease these processes different water chemistries are used. Today the great attention is being attracted to the application of film forming amines and film forming amine products. The International Association for the Properties of Water and Steam (IAPWS) consolidated the information from all over the World, and based on the research studies and operating experience of researchers and engineers from 21 countries, developed and authorized the Technical Guidance Document: “Application of Film Forming Amines in Fossil, Combined Cycle, and Biomass Power Plants” in 2016. This article describe Russian and International technical guidance documents for the cycle water chemistries based on film forming amines at fossil and combined cycle power plants.

“Live” Formulations of International Association for the properties of Water and Steam (IAPWS)

Online publication of IAPWS formulations for calculation of the properties of water and steam is reviewed. The advantages of electronic delivery via Internet over traditional publication on paper are examined. Online calculation can be used with or without formulas or equations printed in traditional publications. Online calculations should preferably free of charge and compatible across multiple platforms (Windows, Android, Linux). Other requirements include availability of multilingual interface, traditional math operators and functions, 2D and 3D graphic capabilities, animation, numerical and symbolic math, tools for solving equation systems, local functions, etc. Using of online visualization tools for verification of functions for calculating thermophysical properties of substances is reviewed. Specific examples are provided of tools for the modeling of the properties of chemical substances, including desktop and online calculation software, downloadable online calculations, and calculations that use server technologies such as Mathcad Calculation Server (see the site of National Research University “Moscow Power Engineering Institute”) and SMath (see the site of Knovel, an Elsevier company).

Unleashing Empirical Equations with “Nonlinear Fitting” and “GUM Tree Calculator”

Empirical equations having large numbers of fitted parameters, such as the international standard reference equations published by the International Association for the Properties of Water and Steam (IAPWS), which form the basis of the “Thermodynamic Equation of Seawater—2010” (TEOS-10), provide the means to calculate many quantities very accurately. The parameters of these equations are found by least-squares fitting to large bodies of measurement data. However, the usefulness of these equations is limited since uncertainties are not readily available for most of the quantities able to be calculated, the covariance of the measurement data is not considered, and further propagation of the uncertainty in the calculated result is restricted since the covariance of calculated quantities is unknown. In this paper, we present two tools developed at MSL that are particularly useful in unleashing the full power of such empirical equations. “Nonlinear Fitting” enables propagation of the covariance of the measurement data into the parameters using generalized least-squares methods. The parameter covariance then may be published along with the equations. Then, when using these large, complex equations, “GUM Tree Calculator” enables the simultaneous calculation of any derived quantity and its uncertainty, by automatic propagation of the parameter covariance into the calculated quantity. We demonstrate these tools in exploratory work to determine and propagate uncertainties associated with the IAPWS-95 parameters.

Application of the new IAPWS Guideline on the fast and accurate calculation of steam and water properties with the Spline-Based Table Look-Up Method (SBTL) in RELAP-7

Abstract The numerical simulation of thermalhydraulic processes in nuclear power plants requires very accurate and extremely fast algorithms for calculating the thermophysical properties of water and steam. In order to provide such algorithms, the International Association for the Properties of Water and Steam (IAPWS) has adopted the new “IAPWS Guideline on the Fast Calculation of Steam and Water Properties with the Spline-Based Table Look-Up Method (SBTL)”. In this article, the SBTL method is applied to property functions of specific volume and specific internal energy (v,e) based on the scientific formulation IAPWS-95 and the latest IAPWS formulations for transport properties. From the newly generated SBTL functions, thermodynamic and transport properties as well as their derivatives and inverse functions are calculable in the fluid range of state for pressures up to 100 MPa and for temperatures up to 1273 K, including the metastable liquid and the metastable vapor regions. The SBTL functions reproduce the underlying formulations with an accuracy of 10–100 ppm and significantly reduced computing times. The SBTL method has been implemented into the nuclear reactor system safety analysis code RELAP-7 [2] to consider the real fluid behavior of water and steam in a novel 7-equation two-phase flow model.

International water and steam quality standards for thermal power station drum-type and waste heat recovery boilers with the treatment of boiler water with phosphates and NaOH

One of the ways for improving the operational reliability and economy of thermal power station equipment, including combined-cycle equipment, is to decrease the rates of the corrosion of constructional materials and the formation of scales in the water-steam circuit. These processes can be reduced to a minimum via the use of water with a minimum content of admixtures and the correction treatment of a heat-transfer fluid. The International Association for the Properties of Water and Steam (IAPWS), which unites specialists from every country of the world, has developed water and steam quality standards for power station equipment of different types on the basis of theoretical studies and long-term experience in the operation of power plants in 21 countries. Different water chemistry regimes are currently used at conventional and combined-cycle thermal power stations. This paper describes the conditions for the implementation of water chemistry regimes with the use of sodium salts of phosphoric acid and NaOH for the quality correction of boiler water. Water and steam quality standards and some recommendations for their maintenance under different operational conditions are given for each of the considered water chemistry regimes. The standards are designed for the water-steam circuit of conventional and combined-cycle thermal power stations. It is pointed out that the quality control of a heat-transfer fluid must be especially careful at combined-cycle thermal power stations with frequent startups and shutdowns.

International water and steam quality standards on thermal power plants at all-volatile treatment

One of the methods for the improvement of reliability and efficiency of the equipment at heat power plants is the decrease in the rate of corrosion of structural materials and sedimentation in water/steam circuit. These processes can be reduced to minimum by using the water with low impurity content and coolant treatment. For many years, water and steam quality standards were developed in various countries (United States, Germany, Japan, etc.) for specific types of equipment. The International Association for the Properties of Water and Steam (IAPWS), which brings together specialists from 21 countries, developed the water and steam quality standards for various types of power equipment based on theoretical studies and long-term operating experience of power equipment. Recently, various water-chemistry conditions are applied on heatpower equipment including conventional boilers and HRSGs with combined cycle power plants (Combined Cycle Power Plants (CCPP)). In paper, the maintenance conditions of water chemistry with ammonia or volatile amine dosing are described: reducing AVT(R), oxidizing AVT(O), and oxygen OT. Each of them is provided by the water and steam quality standards and recommendations are given on their maintenance under various operation conditions. It is noted that the quality control of heat carrier must be carried out with a particular care on the HPPs with combined cycle gas turbine units, where frequent starts and halts are performed.