The Integrated Energy System (IES) enables integrated control and coordinated optimization of multiple energy flows. Due to the complexity of dynamic characteristics of multiple energy flows and the significant differences in time scales, thermodynamic problems occur during the operation of the system. In this paper, we propose an IES operation method that comprehensively considers thermodynamics to reduce the impact of thermal transmission delay on the system's operational strategy, including modeling, evaluation, and scheduling programs. Firstly, an IES model is established to describe the dynamic characteristics of the energy supply network. Secondly, a two-stage optimization scheduling model considering thermal transmission delay is established to reduce the impact of thermal transmission delay on the operation decisions of IES, and the thermal power imbalance rate index is proposed to measure the impact of thermodynamics. Finally, the proposed method's effectiveness is validated by utilizing a comprehensive energy system as an example and implementing it on the MWORKS platform using the Modelica and Julia languages.

In parallel channels of a nuclear reactor core, flow instability can cause a significant decrease in critical heat flux (CHF) or mechanical oscillation of the fuel components, endangering the normal operation of the reactor. The NUMAP software, developed based on the two-fluid six-equation theory and using the Modelica language, is a multi-domain unified modeling and simulation platform for nuclear power plants. In this paper, a parallel dual-channel system model was constructed based on the NUMAP software, referencing a high-temperature and high-pressure steam-water two-phase thermohydraulic experimental device, to simulate flow instability phenomena. The comparison with experimental data validated the transient analysis ability of the NUMAP software for flow instability phenomena. Based on this, the flow instability boundary of a parallel multi-channel system was calculated under the same operating conditions. When the number of parallel channels was 2, 3, and 4, the calculated flow instability boundary error did not exceed ±5%, verifying that a parallel dual-channel structure can be used to obtain the flow instability boundary when there are multiple parallel heating channels.

Keywords: parallel channels, flow instability, Modelica, NUMAP

For dynamically simulating the thermal behavior of a building, the reduced-order model (ROM) implemented in the Modelica IBPSA and AixLib libraries provides a time-efficient calculation method based on the standard VDI 6007-1. Additionally, the Python package TEASER features a possilibity to fill the model parameters with automatically generated typical and/or enriched building data. So far, both have not been capable of modelling heat flow through borders between thermal zones. In this contribution, we present the integration of this feature into the open-source software combination. Additional new features include non-constant soil temperatures and a new approach to estimate interior building elements in cases without proper knowledge. Calculation results are presented for an exemplary application and show satisfactory agreement with measured values. The respective code (including the example presented here) is in the process of being published as part of the AixLib and TEASER open-source repositiories.