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.

Fast Simulations of Air Conditioning Systems Using Spline-BasedTable Look-Up Method (SBTL) with Analytic Jacobians

“…SBTL method is one of them with proven accuracy, performance, and robustness. A detailed description of the SBTL method can be found in the reference (Kunick et al, 2015). This section focuses on its distinct features and derivative derivation.…”

“…To address performance requirements for complex vapor cycle system simulations, a new property model based on the Spline-Based Table Look-Up Method (Kunick et al, 2015) was implemented in Modelica (Li et al, 2018). This implementation uses external C functions for fast spline evaluations and inversion.…”

Fast Calculation of Refrigerant Properties in Vapor Compression Cycles Using Spline-Based Table Look-Up Method (SBTL)

“…The key concepts of the SBTL method are illustrated in this section using an example of 1D spline. A complete description of the method can be found in the reference (Kunick et al, 2015). The data generation process is also covered here followed by the explanation of the property model structure.…”

“…Spline interpolation in 2D is just an extension of the 1D example. The detailed formulation can be found in the reference (Kunick et al, 2015). The solution algorithm for the spline coefficients are given in the book .…”

“…Extensive literature reviews can be found in the reference (Laughman et al, 2012;Schulze, 2013;Aute et al, 2014) and thus not repeated in this paper. The Spline-Based Table Look-Up Method (Kunick et al, 2015) is chosen to approximate different refrigerant properties in this work because it possesses the following unique features:…”