I. Stöcker

Bio: I. Stöcker is an academic researcher. The author has contributed to research in topics: Critical point (thermodynamics) & Boiler (power generation). The author has an hindex of 4, co-authored 6 publications receiving 976 citations.

The IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam

Abstract: In the 1960’s an industrial formulation for the thermodynamic properties of water and steam was developed called “The 1967 IFC Formulation for Industrial Use” (IFC-67) [1]. Since 1967 IFC-67 has been formally recognized to calculate thermodynamic properties of water and steam for any official use such as performance guarantee calculations of power cycles. In addition to this, IFC-67 has been used for innumerable other industrial applications. However, during the last few years a number of weaknesses of IFC-67 have appeared. This fact and the progress that has been achieved in mathematical methods to develop accurate equations of state led to the development of a new industrial formulation in an international research project initiated and coordinated by the International Association for the Properties of Water and Steam (IAPWS).

Supplementary Backward Equations for Pressure as a Function of Enthalpy and Entropy p(h,s) to the Industrial Formulation IAPWS-IF97 for Water and Steam

Abstract: In modeling steam power cycles, thermodynamic properties as functions of the variables enthalpy and entropy are required in the liquid and the vapor regions. It is difficult to perform these calculations with IAPWS-IF97, because they require two-dimensional iterations calculated from the IAPWS-IF97 fundamental equations. While these calculations are not frequently required, the relatively large computing time required for two-dimensional iteration can be significant in process modeling. Therefore, the International Association for the Properties of Water and Steam (IAPWS) adopted backward equations for pressure as a function of enthalpy and entropy p(h,s) as a supplement to the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam (IAPWS-IF97) in 2001. These p(h,s) equations are valid in the liquid region 1 and the vapor region 2. With pressure p, temperature T(h,s) can be calculated from the IAPWS-IF97 backward equations T(p,h). By using the p(h,s) equations, the two dimensional iterations of the IAPWS-IF97 basic equations can be avoided. The numerical consistency of pressure and temperature obtained in this way is sufficient for most heat cycle calculations. This paper summarizes the need and the requirements for the p(h,s) equations and gives complete numerical information about the equations. Moreover, the achieved quality of the equations and their use in the calculation of the backward function T(h,s) is presented. The three aspects, numerical consistency with the IAPWS-IF97 basic equations, consistency along subregion boundaries, and computational speed important for industrial use are discussed.

Supplementary Backward Equations T(p,h), v(p,h), and T(p,s), v(p,s) for the Critical and Supercritical Regions (Region 3) of the Industrial Formulation IAPWS-IF97 for Water and Steam

Abstract: In modeling advanced steam power cycles, thermodynamic properties as functions of pressure and enthalpy (p,h) or pressure and entropy (p, s) are required in the critical and supercritical regions (region 3 of IAPWS-IF97). With IAPWS-IF97, these calculations require cumbersome two-dimensional iteration of temperature T and specific volume v from (p,h) or (p,s). While these calculations in region 3 are not frequently required, the computing time can be significant. Therefore, the International Association for the Properties of Water and Steam (IAPWS) adopted backward equations for T(p,h), v(p,h), T(p ,s), and v(p,s) in region 3, along with boundary equations for the saturation pressure as a function of enthalpy, P 3sat (h), and of entropy, p 3Sat (s). Using the new equations, two-dimensional iteration can be avoided. The numerical consistency of temperature and specific volume obtained in this way is sufficient for most uses. This paper summarizes the need and the requirements for these equations and gives complete numerical information. In addition, numerical consistency and computational speed are discussed.

Supplementary Backward Equations p(h,s) for the Critical and Supercritical Regions (Region 3), and Equations for the Two-Phase Region and Region Boundaries of the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam

Abstract: When steam power cycles are modeled, thermodynamic properties as functions of enthalpy and entropy are required in the critical and supercritical regions (region 3 of IAPWS-IF97). With IAPWS-IF97, these calculations require cumbersome two-dimensional iteration of temperature T and specific volume v from specific enthalpy h and specific entropy s. While these calculations are not frequently required, the computing time can be significant. Therefore, the International Association for the Properties of Water and Steam (IAPWS) adopted backward equations for p(h,s) in region 3. For calculating properties as a function of h and s in the part of the two-phase region that is important for steam-turbine calculations, a backward equation T sat (h,s) is provided. In order to avoid time-consuming iteration in determining the region for given values of h and s, equations for the region boundaries were developed. The numerical consistency of the equations documented here is sufficient for most applications in heat-cycle, boiler, and steam-turbine calculations.

A method for generating interpolation tables with optimized data density for fast interpolations of thermodynamic properties in process modeling

Abstract: The paper presents an algorithm which is able to gener­ ate interpolation tables with optimized data density for the required interpolation accuracy (absolute or rela­ tive) for the required thennodynamic functions, including backward functions, and for a given interpolation method (linear interpolation, spline interpolation with or without coordinate trans­ fonnations). The generated tables may be used for the interpolation of thennodynamic properties in process modeling. The optimization of the data density is realized by a flexible strategy of condensing the data grid. Ranges of state where the required interpolation accuracy is already fulfilled are sorted out step by step. Furthennore, the data density is decreased by transfonning the properties concemed in the interpolation. The transfonnations differ in the liquid and vapor regions and, also, for linear and spline interpo­ lations. The fmdings show that the number of data points neces­ sary for accurate interpolations is considerably fewer than expected. INTRODUCTION The interpolation of thennodynamic properties in proc­ ess modeling is becoming more and more attractive due to the availability of computers with large memories and modem spline algorithms. The advantages of interpolation are: • Simple mathematical operations requiring very brief computing times. • Fast application of the calculations to other fluids, other functions, or other ranges of state, by merely replacing the interpolation data tables. • Interpolation of both forward and backward thenno­ dynamic functions, such as h=f(T,p) and T=f(h,p), with the extremely high numerical consistency required in process modeling. A very important issue in all interpolations is the density of the data tables. As is weIl known, the data density depends on: the demanded interpolation accuracy the interpolation method used. However, the data density may be decreased, provided the variables upon which the interpolation is based are first mathematically transfonned. This investigation advances the authors' earlier works (Kretzschmar, 1990) and (NabeI, 1991) and describes the present state of research. INTERPOLATION METHODS AND DATA TABLE STRUCTURE In the work presented here, linear and spline interpo­ lations have been applied. The procedure for generating the corresponding, optimized data tables can also be used for other interpolation methods. As shown in Fig. I, the data tables for supercooled liquid and superheated vapour are divided by the saturation line Ps =f(T) and by the critical isothenn Tcr =const above the critical pressure and have an isobaric structure.

Bio-Inspired Evaporation Through Plasmonic Film of Nanoparticles at the Air–Water Interface

Abstract: Plasmonic gold nanoparticles self-assembled at the air-water interface to produce an evaporative surface with local control inspired by skins and plant leaves. Fast and efficient evaporation is realized due to the instant and localized plasmonic heating at the evaporative surface. The bio-inspired evaporation process provides an alternative promising approach for evaporation, and has potential applications in sterilization, distillation, and heat transfer.

New International Formulation for the Viscosity of H2O

Abstract: The International Association for the Properties of Water and Steam (IAPWS) encouraged an extensive research effort to update the IAPS Formulation 1985 for the Viscosity of Ordinary Water Substance, leading to the adoption of a Release on the IAPWS Formulation 2008 for the Viscosity of Ordinary Water Substance. This manuscript describes the development and evaluation of the 2008 formulation, which provides a correlating equation for the viscosity of water for fluid states up to 1173K and 1000MPa with uncertainties from less than 1% to 7% depending on the state point.

Entropy Generation Analysis of Desalination Technologies

Abstract: Increasing global demand for fresh water is driving the development and implementation of a wide variety of seawater desalination technologies. Entropy generation analysis, and specifically, Second Law efficiency, is an important tool for illustrating the influence of irreversibilities within a system on the required energy input. When defining Second Law efficiency, the useful exergy output of the system must be properly defined. For desalination systems, this is the minimum least work of separation required to extract a unit of water from a feed stream of a given salinity. In order to evaluate the Second Law efficiency, entropy generation mechanisms present in a wide range of desalination processes are analyzed. In particular, entropy generated in the run down to equilibrium of discharge streams must be considered. Physical models are applied to estimate the magnitude of entropy generation by component and individual processes. These formulations are applied to calculate the total entropy generation in several desalination systems including multiple effect distillation, multistage flash, membrane distillation, mechanical vapor compression, reverse osmosis, and humidification-dehumidification. Within each technology, the relative importance of each source of entropy generation is discussed in order to determine which should be the target of entropy generation minimization. As given here, the correct application of Second Law efficiency shows which systems operate closest to the reversible limit and helps to indicate which systems have the greatest potential for improvement.

How Can Hydrophobic Association Be Enthalpy Driven

Abstract: Hydrophobic association is often recognized as being driven by favorable entropic contributions. Here, using explicit solvent molecular dynamics simulations we investigate binding in a model hydrophobic receptor−ligand system which appears, instead, to be driven by enthalpy and opposed by entropy. We use the temperature dependence of the potential of mean force to analyze the thermodynamic contributions along the association coordinate. Relating such contributions to the ongoing changes in system hydration allows us to demonstrate that the overall binding thermodynamics is determined by the expulsion of disorganized water from the receptor cavity. Our model study sheds light on the solvent-induced driving forces for receptor−ligand association of general, transferable relevance for biological systems with poorly hydrated binding sites.