12я Азиатская конференция по теплофизическим свойствам (ATPC 2019)






Конференция будет проходить со 2 по 5 октября в КНР
(Xian Jiaotong University - Сиань, провинция Шэньси)



Регистрация участников



Сайт конференции:atpc2019.org
Ying Zhang, zhangying@mail.xjtu.edu.cn
Yaohui Shi, 18051368905@163.com


Программа и контакты с организаторами конференции



Приглашенные доклады


Mikhail A. Anisimov

Professor at University of Maryland, USA

Thermodynamics of Fluid Polyamorphism


Abstract


For most pure materials (at a given temperature and pressure), molecules are arranged in a single noncrystalline or amorphous structure that is liquid, gas, or solid. Conventional theory adequately predicts the thermodynamic properties of such materials, which are well understood. In contrast to this simple picture, there is increasing evidence that many pure fluids exist in several alternative structures,resulting in the phenomenon known as “fluid polyamorphism.” It has been hypothesized that even water may exhibit this behavior at very low temperatures. Our recent research1 contributes to better understanding of this phenomenon by developing a unified theoretical framework that is capable of making robust predictions for the thermodynamic properties of different polyamorphic fluids. We use the theory of phase transitions and the concept of two competing interconvertible amorphous structures to develop a generic phenomenological approach, which is independent of the underlying molecular origin of the phenomenon and provides new physical insights. It succeeds in unifying all,apparently unrelated, cases of fluid polyamorphism with and without phase separation, from the liquid-liquid transition in supercooled water and silicon to superfluid helium and polymerized sulfur. Our approach generically describes the phase behavior and thermodynamic anomalies typically observed in polyamorphic materials, including liquid-vapor and liquid-liquid transitions, as well as stretched metastable liquid states under negative pressures. The results mark a paradigm shift that significantly broadens fluid polyamorphism from its original narrow scope to a cross-disciplinary field that addresses a wide class of systems and phenomena with interconversion of alternative molecular or supramolecular states.


Yasuyuki Takata

Professor at Kyushu University, Japan

Thermal Problems of Hydrogen at High Pressures


Abstract


Hydrogen is a promising energy career in the future carbon-neutral society. In December 2014, Toyota motors has started to sell a commercial fuel cell vehicle (FCV) into Japanese market and has been increasing its production year by year. In order to disseminate the FCVs, the hydrogen refueling station (HRS) should be placed everywhere in the society. There are about 90 HRSs in Japan as of January 2019. The current FCV has 5kg of hydrogen at 82MPa in tank pressure. Therefore, the HRS has to handle hydrogen with higher pressure up to 100MPa to refill it to FCVs. Currently, the charging time to fill up the H2 tank is expected to be 3 min or shorter. However, such a rapid refueling process causes temperature rise in the H2 tank by adiabatic compression. The limit temperature of the H2 tank is 85C because of the melting point of a bonding agent for carbon fibers of the tank. To avoid undesirable temperature rise, the recent HRSs are equipped with a precooling device that cools the hydrogen down to -40 C in advance. However, this precooling process causes the other problems. One is the overcharge of hydrogen. Since the hydrogen gas at low temperature is injected into tank up to target pressure at the end of refueling process, the tank pressure increases gradually due to heat transfer from the surrounding. This pressure rise by heat transfer sometimes exceeds the limit pressure of the tank. The second problem is a frost formation around the injection nozzle and the receptacle. Sometimes, ice is formed and the hydrogen nozzle is stuck to the receptacle. For safety operations of HRS, these thermal problems must be solved. Our research effort is devoted to the first problem. To ensure the safety of FCVs during refueling hydrogen, transient pressure and temperature in tank should be predicted with sufficient accuracy. The first step is to collect accurate thermophysical property data for hydrogen in a wide range of pressures and temperatures. We have been measuring thermodynamic and transport properties of hydrogen up to 100 MPa and 500 C to develop a reliable database. Based on this hydrogen thermopysical property database, we have been developing a useful software for dynamic simulation of HRS which predicts flow rate, temperatures and pressures of HRS and H2 tank of FCV. Some typical thermo-technical problems with hydrogen refueling process are introduced in the presentation.

Дата публикации: 2019-10-01 (11176 Прочтено)