Рабочая пара "LiCl/многослойные углеродные нанотрубки" - вода для запасания тепловой энергии: исследование динамики

Сорбционное запасание тепла (СЗТ) - одна из перспективных технологий для эффективного использования возобновляемых источников энергии. Композитные материалы типа "Соль в пористой матрице" представляют интерес для СЗТ, так как демонстрируют высокие значениями запасающей способности. Недавно для СЗТ был предложен новый сорбент на основе хлорида лития и многослойных углеродных нанотрубок "LiCl/(МУНТ)", характеризующийся запасающей способностью 1,7 кДж/г. Новый материал представляет собой порошок, что затрудняет его загрузку в теплообменник. Данная работа посвящена: 1) формованию нового композита с использованием поливинилового спирта в качестве связующего; 2) исследованию сорбционного равновесия гранулированного композита с парами воды и оценка его запасающей способности; 3) изучению динамики сорбции воды в условиях суточного цикла СЗТ на небольшом, но репрезентативном фрагменте реального оребренного плоского теплообменника; 4) оценке удельной мощности для стадий запасания и высвобождения тепла. Было показано, что динамические кривые сорбции воды подчиняются экспоненциальному закону с характерным временем [tau]=90-300 с. При конверсии 0,8 удельная мощность для стадии выделения тепла варьируется в диапазоне 2,9-4,1 Вт/г, для стадии запасания тепла - 9,7-9,8 Вт/г. Высокие значения удельной мощности наряду с большой запасающей способностью нового композита демонстрируют перспективность упомянутого материала для СЗТ

Activated Carbons as Methanol Adsorbents for a New Cycle “Heat from Cold”

Activated carbons are widely used for sustainable technology of adsorptive transformation and storage of heat. Here, we analyze the applicability of twelve commercial carbons and an innovative carbonaceous composite “LiCl confined to multi-wall carbon nanotubes” (LiCl/MWCNT) for a new cycle “Heat from Cold” (HeCol). It has recently been proposed for amplification of low- temperature ambient heat in cold countries. The analysis is made in terms of the methanol mass exchanged and the useful heat generated per cycle; the latter is the main performance indicator of HeCol cycles. The maximum specific useful heat, reaching 990 and 1750 J/g, can be obtained by using carbon Maxsorb III and the composite, respectively. For these materials, methanol adsorption dynamics under typical HeCol conditions are experimentally studied by the large pressure jump method. Before making this analysis, the fine carbon powder is consolidated by either using a binder or just pressing to obtain larger particles (ca. 2 mm). The methanol desorption from the consolidated samples of Maxsorb III at T = 2 °C is faster than for LiCl/MWCNT, and the maximum (initial) useful power reaches (2.5–4.0) kW/kg sorbent. It is very promising for designing compact HeCol units utilizing the carbon Maxsorb III

New Adsorption Method for Moisture and Heat Exchange in Ventilation Systems in Cold Countries: Concept and Mathematical Simulation

Due to global climate change and fossil fuel depletion, the rational use of thermal energy has attracted great research interest. Large differences between indoor and outdoor temperatures in cold regions results in huge amounts of heat waste and drop in indoor humidity. Ventireg, an adsorption method, has been often recommended for heat and humidity regeneration in cold countries. In this research work, VentireC, an advanced method employing two thermally coupled adsorbent beds is discussed. It allows the heat released during adsorption of moisture in one adsorber to be transferred to another adsorber to facilitate water desorption. The VentireC approach is comprehensively analysed and described in this paper. A composite adsorbent based on LiCl in silica gel pores, which can exchange up to 0.5 g-H2O/g-sorbent, is selected for VentireC processes under cold Western Siberia conditions. Mathematical simulation of humidity recuperation, employing the selected sorbent with and without thermal coupling, demonstrates the advantages of the VentireC process

Novel adsorption method for moisture and heat recuperation in ventilation: Composites “LiCl/matrix” tailored for cold climate

Nowadays, advanced technologies for rational use of energy in dwellings have aroused a considerable interest. In cold countries huge amounts of heat and moisture are wasted through the air infiltration due to the large difference between indoor and outdoor temperatures. In this work, an advanced adsorption approach to heat and moisture recuperation in ventilation, called VentireC, is suggested. In this approach, the moisture and sensible heat from outgoing air are absorbed on the adsorbent and heat storing beds and then withdrawn into the inflowing outdoor air, thus, maintaining the indoor temperature and humidity balance. Thermal coupling between two adsorbent beds, which work out of phase, allows latent and sensible loads to be managed separately to enhance the humidity recuperation. For harmonizing the adsorbent properties with the operating conditions of the VentireC process, the requirements for optimal sorbents are formulated based on the thermodynamic analysis of the process. New sorbents based on LiCl incorporated in four matrices with the various mesoporous structure are synthesized and investigated. The water sorption/desorption equilibrium for the most promising sorbent is reported. This composite exchanges over 0.5 g-H2O/g under a typical VentireC cycle, which is promising for effective heat and moisture regeneration

"Water - Silica Siogel" working pair for adsorption chillers: Adsorption equilibrium and dynamics

The aim of this paper is to study the equilibrium and dynamics of water adsorption on a commercial silica gel Siogel. This adsorbent has recently been suggested and tested for adsorptive transformation and storage of low temperature heat. The original data on the water vapour equilibrium and dynamics are compared with those earlier reported for the Fuji silica RD. This database can be used for theoretical analysis, mathematical modeling and evaluation of adsorptive cycles based on the working pair water - Siogel and driven by heat from renewable heat sources