• Energy Research
• Restricted close
• Open Source close
• RU close
• CNR ExploRA close

[object Object]

Abstract This paper presents a mathematical model of coupled heat and mass transfer in multi-layers of loose adsorbent grains under realistic conditions of adsorption heat transformation (AHT) cycle. The model allows a simulation of the adsorption dynamics in the adsorbent layer which consists of a low number of loose adsorbent grains (1 ≤ n ≤ 4). Firstly, the model was validated by comparison with the kinetics of isothermal water adsorption on a single spherical grain, initiated by a small pressure drop, for which an analytical solution is well-known. Afterwards, the model was applied to simulate non-isothermal water dynamics for adsorbent-heat exchanger configurations of one, two and four layers of loose grains of Fuji silica type RD. The grains are located on a metal support subjected to a fast variation of temperature as it takes place during isobaric phases of AHT cycle. The system of partial differential equations was solved by using the COMSOL Multiphysics® simulation environment. The calculated sorption dynamics is in a good accordance with the experimental data obtained for n = 1, 2 and 4 under the same boundary conditions. Moreover, the model was used to simulate the ad/desorption process for different grain sizes (0.45, 0.85 and 1.7 mm). The input parameters which ensure the best data fitting were compared with those experimentally determined for Fuji silica type RD as well as with the input data of other heat and mass transfer models presented in the literature. The developed model gives a powerful tool for accurate simulation of dynamic features for the AHT units with practically interesting configuration of the adsorber/heat exchanger which utilizes a low number of loose adsorbent grains. Moreover, useful information about radial and axial distributions of the temperature and vapour concentration can be obtained for both gas and solid phases. Finally, the specific cooling power of AHT cycle was estimated and recommendations on the cycle dynamic optimization were made.

Recently, a new composite "LiCl inside Multi-Wall Carbon NanoTubes" (LiCl/MWCNT) has been suggested as water sorbent for Adsorption Thermal Energy Storage (ATES), because it has a large thermal storage capacity of 1.7 kJ/g for a daily heat storage cycle. This work addresses the results of the study of water sorption dynamics on the novel composite loaded into representative small scale fragments of a common finned flat-tube HEx. The study consists of four parts: (1) shaping the LiCl/MWCNT composite as grains using polyvinyl alcohol (PVA) as a binder; (2) analysis of sorption equilibrium for the pair "LiCl/ MWCNT/PVA - water"; (3) measuring the thermal storage capacity of the granulated LiCl/ MWCNT/PVA composite; (4) investigation of water sorption dynamics on the LiCl/MWCNT/PVA under typical conditions of the daily storage cycle. It is shown that the thermal storage capacity of the LiCl/MWCNT/PVA composite equals 1.5-1.6 kJ/g. The specific power reaches 4.2 and 9.8 kW/kg of the heat release and thermal storage stages, respectively. The results obtained show that the working pair "LiCl/MWCNT/PVA - water" appears to be advantageous for ATES.

Farming of shellfish and seaweeds is a tested tool for mitigating eutrophication consequences in coastal environments, however as many other marine economic activities it should be a subject of marine spatial planning for designating suitable sites. The present study proposes site selection framework for provisional zebra mussel farming in a eutrophic lagoon ecosystem, aimed primarily at remediation purposes. GIS-based multi-criteria approach was applied, combining data from empirical maps, numerical models and remote sensing to estimate suitability parameters. Site selection and prioritisation of suitable areas considered 15 environmental and socio-economic criteria, which contributed to 4 optimisation models (settlement, growth and survival of mussels, environmental and socio-economic) and 3 predefined scenarios representing provisional goals of mussel cultivation: spat production, biomass production and bioremediation. The relative importance of each criterion was assessed utilizing the Analytical Hierarchy Process. Site suitability index was calculated and the final result of the site selection analysis was summarized for 3 scenarios and overall suitability map. Four suitability classes (unsuitable, least, moderately and most suitable) were applied, and 3 most suitable zones for provisional zebra mussel cultivation with 12 candidate sites were selected accordingly. The integrated approach presented in this study can be adjusted for designating zebra mussel farming sites in other estuarine lagoon ecosystems, or cultivation of other mussel species for bioremediation purposes. The analytical framework and the workflow designed in this study are also adoptable for addressing other aquaculture-related spatial planning issues.

Thermochemical systems for energy conversion are just at the interface between chemical and thermal engineering because the final aim is a transformation of energy, while the specific tool is a thermally driven chemical reaction. Designing the efficient systems calls for appropriate choice of chemical process, comprehensive analysis of its thermodynamics and kinetics, intensification of heat and mass transfer, intelligent integration of components into overall heat device, etc. This paper reviews the joint activity of the six institutes from the four countries on applying chemical reactions in modern devices for production of cold, which are driven by solar heat.

A X-ray l-tomography technique, using a Cu Ka source at 8.048 keV coupled with both polycapillary optics and CCD detector, has been developed to reconstruct the composition of a transient gasoline spray generated by a high-pressure GDI injector for automotive applications. The polycapillary elements enable shaping the divergent beams and getting high-contrast images due to the suppression of radiation multiple scattering. A pressure-tight device permits the 360 rotation of a six-hole nozzle, with a step of 0.1, at injection pressures up to 20 MPa, while the spray plume develops in a vented Plexiglas chamber at the atmospheric backpressure. The entire system is configured as a table-top experiment. The extinction images acquired along the X-ray source-spray-detector line-of-sight have permitted the reconstruction of a 3D structure together with a morphology of the jets within a 3 mm region downstream the nozzle. The spray shape as well as the propagation direction can be clearly identified in the tomographic reconstruction for all the six jets. Quantitative measurements of the fuel mass density in the near nozzle region have been performed. Typical Gaussian-shape distribution of the intensities appears for the cross sections revealing the more dense jet regions in the core, while slight longitudinal asymmetries indicate an interaction between the jet plumes

The present paper reports the experimental characterization of dynamic performance of three Ad-HEx configurations based on the activated carbon/ethanol working pair. The kinetic behavior of ethanol adsorption onto activated carbon was studied by the LTJ (Large Temperature Jump) method that reproduces the real conditions of isobaric stages of adsorptive cooling cycles. The study consists of two main parts: the first one is related to the adsorption kinetics of the Flat Adsorbent Bed configuration, composed of loose adsorbent grains placed on the metal support. While the second one describes the performance evaluation of finned flat - tube HEx configurations loaded with adsorbent grains. The effects of the grain size, the ratio S/m of heat transfer surface to the adsorbent mass and the Ad-HEx geometry are explored in detail in order to find the main factors affecting the adsorption dynamics. On the base of the main findings obtained, the practical recommendations on optimization of the Ad-HEx unit are formulated in order to enhance the specific cooling power of an adsorptive chiller. Furthermore, a comparison of the adsorption characteristic times between the activated carbon and a properly synthesized porous composite, composed of LiBr inside a silica gel host matrix is shown.

Composite SWS-8L was synthesized by impregnating a mesoporous silica KSK with a Saturated aqueous solution of Ca(NO(3))(2). Its equilibrium with water vapor was studied by measuring sorption isobars and isosters at T = 30-150 degrees C. The water sorption increased up to 0.2-0.3 g/g due to the presence of the salt inside the silica pores. The water uptake was not a simple addition of those by the bulk salt and the silica, because the confined salt changed its properties. The isosteric sorption heat decreased from 52 to 47 kJ/mol when the water uptake increased from 0.07 to 0.23 g/g. The X-ray diffraction study revealed no formation of crystalline dihydrate in the confined state during the hydration process that can be caused by the dihydrate dissolution inside the pores. For approximation of the sorption equilibrium, a simple analytical equation based on the Polanyi principle of temperature invariance Was suggested. Sorption kinetics was studied by the Isothermal Differential Step method at T = 50 and 70 degrees C and the pressure range 10-35 mbar, Confinement of calcium nitrate to the silica pores significantly hastened the sorption with respect to the bulk salt. The hydration of the confined salt was limited by the intraparticle water diffusion instead of intrinsic chemical transformation of the bulk Salt. Comparison of the new composite adsorbent with those based on CaCl(2), MgSO(4) and LiBr confined to the same host matrix showed that SWS-8L can be envisaging further development for adsorptive air conditioning driven by low temperature heat.