Impact of Sintered Temperature on the Heat and Cation Transport in NaK-BASE Tube

Alkali metal thermoelectric converter (AMTEC) is a clean energy converter that can be coupled with biomass for power generation. In present research, the transport of heat and cation was investigated in NaK-BASE tubes prepared at different sintered temperatures. The heat conduction and the fractal model were employed to investigate the temperature distributions based on the microstructures of the NaK-BASE tubes sintered at different temperatures, and the transport of Na+ and K+ in NaK-BASE tube was simulated by Poisson-Nernst-Planck multi-ions transport model, and the cation concentrations and surface charge densities were obtained in the NaK-BASE tubes with different temperatures. The results showed that microstructure of the NaK-BASE was related to the sintered temperature, and the microstructure of the NaK-BASE impacted the temperature distribution, the cation concentration and the surface charge density of Na+ and K+ in the NaK-BASE tubes. At the same heat source temperature, the average temperature in the NaK-BASE prepared at high sintered temperature was higher than that prepared at low sintered temperature. In addition, the increase of the average temperature resulted in the increase of the cation concentration and the surface charge density of Na+ and K+ in the NaK-BASE, therefore, the performance of the NaK-AMTEC could be enhanced by increasing the sintered temperature and the average temperature of the NaK-BASE.

Li2CO3 as Protection for a High-Temperature Thermoelectric Generator: Thermal Stability and Corrosion Analysis

In most steelmaking processes, huge amounts of waste heat at high temperature (700–800 °C) are thrown into the environment without any use. An alternative use for this waste heat is electricity generation through thermoelectric generators. However, these high temperatures, as well as their fluctuations over time, affect not only the conversion rate of the thermoelectric generator but also its useful lifetime. The incorporation of a latent thermal energy storage (TES) system could be a solution; nevertheless, the thermal stability and corrosive effect of the (PCM) phase change material are key aspects for the thermal storage system definition, in terms of durability. In this work, developed in the framework of the European project “PowGETEG” (RFSR-CT-2015-00028, funded by the Research Fund for Coal and Steel), a high-temperature analysis (700–800 °C) of the Li2CO3 thermal properties, thermal stability and corrosive effect on the AISI 304 and AISI 310 stainless steels is carried out. The results show that the eutectic salt Li2CO3 exhibits high thermal stability with neither change in its thermal properties nor material degradation. This work shows that lithium carbonate Li2CO3 and AISI 310 make a very good combination for the definition of a thermal storage system able to protect a high-temperature thermoelectric converter from temperature variations, making it more reliable.

IMPROVING THE EFFICIENCY OF HOT GAS GENERATORS FOR HEATING AUTOMOTIVE EQUIPMENT

Hot gas generators are used as a source of thermal energy for pre-start preparation of motor vehicles in cold climatic conditions. Their wide application is due to the high thermal power and safety. (Research purpose) The research purpose is in determining the possibilities of using thermoelectric modules to reduce the energy consumption of the battery by hot gas generators. (Materials and methods) Authors used research methods based on the application of standard techniques, while the object of research was the power supply system of a thermal energy source. (Results and discussion) Authors conducted research on ways and methods to reduce the electric consumption of a hot gas generator by recuperating thermal energy into electrical energy using thermoelectric generator modules. The thermoelectric converters installed on the heat pipe of the hot gas generator, due to the high temperature difference, will allow to obtain a high value of the electromotive force. Modeling of the nozzle in the software package of the Ansys three-dimensional modeling system showed that part of the heat energy goes through the surface of the heat pipe. The article proposes the use of a nozzle with a thermoelectric converter installed on the outer surface of the cylinder instead of a heat pipe. The article presents the mathematical model of an improved hot gas generator nozzle. (Conclusions) The use of a thermoelectric converter for the utilization of thermal energy and the replacement of energy losses of the battery, which feeds the hot gas generator, will reduce the internal power losses of the battery and increase the technical readiness of automotive equipment. The introduction of a comprehensive heat treatment system, which is intelligently and functionally linked to a remote monitoring system, will significantly increase the service life of the units most exposed to temperature influences.

STUDY OF PELTIER ELEMENT POWER CHARACTERISTICS

Цель исследования состоит в определении количества выделяемой и поглощаемой теплоты элементом Пельтье марки ТЭК-12705, который в силу своих конструкционных особенностей имеет особую характеристику по потреблению электрической энергии, зависимости которой и необходимо определить. Материалы и методы исследования. Для достижения цели исследования и ответа на поставленные исследовательские вопросы было проведено экспериментальное исследование. Объектом исследования являлся термоэлектрический преобразователь, для которого были созданы условия, позволяющие наблюдать характеристики элемента Пельтье в замкнутой термодинамической системе. Элемент Пельтье – это термоэлектрический преобразователь, принцип действия которого базируется на эффекте Пельтье, а именно возникновении разности температур при протекании электрического тока. В основу работы элементов Пельтье положен спай двух полупроводниковых материалов с разными уровнями энергии электронов в зоне проводимости. При протекании тока через контакт таких материалов электрону необходимо приобрести энергию, чтобы перейти в более высокоэнергетическую зону проводимости другого полупроводника. При поглощении этой энергии происходит охлаждение места контакта полупроводников. Принимая во внимание компактные габаритные размеры этих элементов (пластинки толщиной от 3 до 7 мм), можно заключить, что данные устройства могут быть использованы в сушильных установках. Результаты исследования и их анализ. Результаты настоящего исследования показали, что при изменении разности температуры элемента Пельтье марки ТЭК-12705 от 16,1 до 50,2 °С потребляемая им мощность изменяется от 36,6 до 30,1 Вт, при этом напряжение питания составляет 11,2 В. Продолжительность работы следует определять экспериментальным путем, так как эффективность работы элемента зависит от эффективности теплоотвода. Заключение. В результате проведённого исследования были установлены зависимости, показывающие, что работа элемента Пельтье по своей характеристике наиболее близка к линейному нагревательному устройству, но только при продолжительной эксплуатации и превышении рабочей температуры выше нормы. Problem and goal. The purpose of this study is to determine the amount of heat released and absorbed by the Peltier element of the TEK-12705 brand, which, due to its design features, has a special characteristic for the consumption of electrical energy, the dependencies of which must be determined. Methodology. To achieve the research goal and answer the research questions, an experimental study was conducted. The object of the study was the thermoelectric converter itself, for which conditions were created that allow us to observe the characteristics of the Peltier element in a closed thermodynamic system. The Peltier element is a thermoelectric converter, the principle of operation of which is based on the Peltier efect, namely, the occurrence of a temperature diference when an electric current fows. The work of the Peltier elements is based on the junction of two semiconductor materials with diferent levels of electron energy in the conduction band. When a current fows through the contact of such materials, the electron needs to acquire energy in order to move to a higher-energy conduction band of another semiconductor. When this energy is absorbed, the contact point of the semiconductors cools. Taking into account the compact overall dimensions of these elements (plates with a thickness of 3 to 7 mm), it can be concluded that these devices can be used in drying plants. Results. The results of this study showed that when the temperature diference of the Peltier element of the TEK-12705 brand changes from 16.1 to 50.2 °C, the power consumed by it changes from 36.6 to 30.1 W, while the supply voltage is 11.2 V. The duration of operation should be determined experimentally, since the efciency of the element depends on the efciency of the heat sink. Conclusion. As a result of the conducted research, the dependences were established, showing that the operation of the Peltier element in its characteristic is closest to a linear heating device, but only with prolonged operation and exceeding the operating temperature above the norm.

High-efficiency solar thermoelectric conversion enabled by movable charging of molten salts

Solar energy as an abundant renewable resource has been investigated for many years. Solar thermoelectric conversion technology, which converts solar energy into thermal energy and then into electricity, has been developed and implemented in many important fields. The operation of solar–thermal–electric conversion systems, however, is strongly affected by the intermittency of solar radiation, which requires installation of thermal storage subsystems. In this work, we demonstrated a new solar–thermal–electric conversion system that consists of a thermoelectric converter and a rapidly charging thermal storage subsystem. A magnetic-responsive solar–thermal mesh was used as the movable charging source to convert incident concentrated sunlight into high-temperature heat, which can induce solid-to-liquid phase transition of molten salts. Driven by the external magnetic field, the solar–thermal mesh can move together with the receding solid–liquid interface thus rapidly storing the harvested solar–thermal energy within the molten salts. By connecting with a thermoelectric generator, the harvested solar–thermal energy can be further converted into electricity with a solar–thermal–electric energy conversion efficiency up to 2.56%, and the converted electrical energy can simultaneously light up more than 40 orange-colored LEDs. In addition to stable operation under sunlight, the charged thermal storage subsystem can release the stored heat and thus enables the solar–thermal–electric system to continuously generate electricity after removal of solar illumination.