Metamaterials with negative compressibility – a novel concept with a long history

Metamaterials with negative compressibility are a very promising group of novel materials with a wide variety of potential application. A recent model proposed the construction of structures with three-dimensional negative compressibility by utilizing successive destabilization of stable or metastable states and inducing phase transitions mimicking negative compressibility. Here, we would like to show that similar concept is used by the Nature and a nice example for this kind of metamaterial can be seen even in a glass of water

Cold Energy Utilization in LNG Regasification System Using Organic Rankine Cycle and Trilateral Flash Cycle

"Cold energy" refers to a potential to generate power by utilizing the exergy of cryogenic systems, like Liquefied Natural Gas (LNG), using it as the cold side of a thermodynamic cycle, while the hot side can be even on the ambient temperature. For this purpose, the cryogenic Organic Rankine Cycle (ORC) is one type of promising solution with comprehensive benefits to generate electricity. The performance of this cycle depends on the applied working fluid. This paper focuses on the applicability of some natural working fluids and analyzes their performance upon cold energy utilization in the LNG regasification system. An alternative method, the cryogenic Trilateral Flash Cycle (TFC), is also presented here. The selection of working fluid is a multi-step process; the first step uses thermodynamic criteria, while the second one is addressing environmental and safety issues. It will be shown that in LNG regasification systems, single cryogenic ORC performs higher net output power and net efficiency compared to single cryogenic TFC. Propane as working fluid in the single cryogenic ORC generates the highest net output power and net efficiency. It is demonstrated, that concerning 26 novel LNG terminals, a net power output around 320 MW could be recovered from the cold energy by installing a simple cycle, namely a single-step cryogenic ORC unit using propane as working fluid

Physical-chemical Background of the Potential Phase Transitions during Loss of Coolant Accidents in the Supercritical Water Loops of Various Generation IV Nuclear Reactor Types

Loss of coolant accidents (LOCA) are a serious type of accidents for nuclear reactors, when the integrity of the liquid-loop breaks. While in traditional pressurized water reactors, pressure drop can cause flash boiling, in Supercritical-Water Cooled reactors, the pressure drop can be terminated by processes with fast phase transition (flash boiling or steam collapse) causing pressure surge or the expansion can go smoothly to the dry steam region. Modelling the pressure drop of big and small LOCAs as isentropic and isenthalpic processes and replacing the existing reactor designs with a simplified supercritical loop, limiting temperatures for various outcomes will be given for 24.5 and 25 MPa initial pressure. Using the proposed method, similar accidents for chemical reactors and other equipment using supercritical fluids can be also analyzed, using only physical-chemical properties of the given supercritical fluid

Investigation of Corrosion Resistance of Alloys with Potential Application in Supercritical Water-cooled Nuclear Reactors

The Supercritical Water Cooled Reactor (SCWR) is one of the Generation IV reactor types, which has improved safety and economics, compared to the present fleet of pressurized water reactors. For nuclear applications, most of the traditional materials used for power plants are not applicable, therefore new types of materials have to be developed. For this purpose corrosion tests were designed and performed in a supercritical pressure autoclave in order to get data for the design of an in-pile high temperature and high-pressure corrosion loop. Here, we are presenting some results, related to corrosion resistance of some potential structural and fuel cladding materials

Anomalous Properties of Some Fluids − with High Relevance in Energy Engineering − in Their Pseudo-critical (Widom) Region

Recent results are shown about the peculiarities of the pseudo-critical region, with special emphasis on properties important for energy production and conversion. The property-map of some materials, which are relevant as model fluids or as working / cooling fluids in energy engineering (argon, methane, water and carbon dioxide) and their relative positions to various adiabats – influencing their stability through the anomalous properties – are presented. Some potential technological problems related to the existence of these anomalies are discussed

Estimation of the Thermodynamic Limit of Overheating for Bulk Water from Interfacial Properties

The limit of overheating or expanding is an important property of liquids, which is relevant for the design and safety assessment of processes involving pressurized liquids. In this work, the thermodynamic stability limit – the so-called spinodal – of water is calculated by molecular dynamics computer simulation, using the molecular potential model of Baranyai and Kiss. The spinodal pressure is obtained from the maximal tangential pressure within a liquid‒vapor interface layer. The results are compared to predictions of various equations of states. Based on these comparisons, a set of equations of state is identified which gives reliable results in the metastable (overheated or expanded) liquid region of water down to −55 MPa

Relation between the Liquid Spinodal Pressure and the Lateral Pressure Profile at the Liquid-Vapor Interface

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