A. Dittmann

Bio: A. Dittmann is an academic researcher from Dresden University of Technology. The author has contributed to research in topics: Algorithm & Set (abstract data type). The author has an hindex of 3, co-authored 3 publications receiving 965 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.

IMPROVED EQUATIONS FOR BACKWARD FUNCTIONS T=f(p,h), T=f(p,s), Ts=f(p) - A CONTRIBUTION TO THE IAPWS PROJECT "NEW INDUSTRIAL FORMULATION"

Abstract: The paper presents improved equation structures for g=f(T,p), T=f(p,h) and T=f(p,s) in the steam region, equation structures for T=f(p,h) and T=f(p,s) in the liquid region and various equation pairs p_s=f(T) and T_s=f(p) on the saturation curve which are the subject of the current IAPWS project "New Industrial Formulation". The established equations fall within the uncertainty limits set by the IAPWS 1985 Skeleton Tables when compared to the Saul/Wagner equation converted to the new Temperature Scale ITS 90. The numerical consistency of the backward.equations meets the demands of process modeling which were set by the IAPWS Subcommittee on Industrial Calculations. Using these equations in process modeling eliminates the otherwise necessary iterations in calculating backward functions. The structures of the equations have been optimized with the Algorithm of Setzmann and Wagner. After that equations have been made numerically consistent with the simultaneous approximation method developed by Zschunke and advanced by Willkommen.

An algorithm for setting up numerically consistent forward and backward equations for process modelling

Abstract: The algorithm has been designed for setting up simplified, fast equations for use in energetic process modellings. Simplified numerically consistent equations h=h(T,p), derived from an equation g=g(T,p), and T=T(p,h) for use in power cycle calculations were set up for demonstration purposes. The algorithm finds numerically consistent equations with a minimized total number of terms automatically and with hardly any subjective influences. Only the corresponding banks of terms have to be established by the equation maker. The algorithm connects the structure optimization method of Setzmann and Wagner with the simultaneous steady approximation method of Zschunke. So the disadvantages of one method can be compensated by the advantages of the other one. Subalgorithms for optimizing the distribution of the input data calculated from a very precise equation of state and for optimizing their weightings have been developed in order to get good equations automatically. The algorithm can be used for setting up the numerically consistent equation pairs T=T(p,h) and h=h(T,p) as well as T=T(p,s) and s=s(T,p) needed for the IAPWS-project "New Industrial Formulation", too.

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.