PCMs (phase change materials) applied in heat storage technology are on the one hand characterised by relatively large specific heat capacity, and on the other hand by relatively low thermal conductivity (e.g. 0.2 W·m⁻¹·K⁻¹) for paraffin), which prolongs the charging/discharging cycles of heat accumulators based on such materials. In order to improve the heat transfer within PCMs, spatially shaped pin-fin metal alloy structures are being developed that have been immersed in the PCM material. Pin-fin metallic structures can be manufactured via investment casting technology. The 3D structures produced using this technique can be modified and adjusted in order to improve the heat transfer parameters (heat conductivity, specific heat transfer area). For this study, complex metal alloy pin-fin structures were immersed in paraffin, and an experimental test stand was built in order to examine the heat transfer characteristics of composite PCMs with pin-fin metal structures. Multiple heating/cooling cycles confirmed the enhanced transfer of heat inside the heat storage unit and allowed us to ascertain the decreased temperature gradient within the heat accumulator. The heat transfer phenomenon was simulated to show heating and melting course nearby metal inserts and confirm the beneficial influence of the applied pin-fin geometry, that can be further optimized. The thermal behaviour of the PCM, tested with DSC and TGA analysis, was used as an input for the simulation.

The paper presents an innovative method for smoothing fluctuations of heat flux, using the thermal energy storage unit (TES Unit) with phase change material and Artificial Neural Networks (ANN) control. The research was carried out on a pilot large-scale installation, of which the main component was the TES Unit with a heat capacity of 500 MJ. The main challenge was to smooth the heat flux fluctuations, resulting from variable heat source operation. For this purpose, a molten salt phase change material was used, for which melting occurs at nearly constant temperature. To enhance the smoothing effect, a classical control system based on PID controllers was supported by ANN. The TES Unit was supplied with steam at a constant temperature and variable mass flow rate, while a discharging side was cooled with water at constant mass flow rate. It was indicated that the operation of the TES Unit in the phase change temperature range allows to smooth the heat flux fluctuations by 56%. The tests have also shown that the application of artificial neural networks increases the smoothing effect by 84%.

This paper presents a study on the application of a ceramic filter in the biomass gasification process and its efficiency in particulate matter removal from the process gas and flue gas. A significant advantage of this type of filter is its high efficiency in small particle removal (<1 µm). This feature allows us to reach the much lower emissions that are required by the applicable standards. The study was performed using an original biomass gasification installation, where conifer scobs were used as feedstock. The installation, its operation and measurement methodology are described in the article. The study included the analysis of process gas and particulate matter, as well as particulate matter content before and after the filter was applied. The measurements indicate that the efficiency of particulate matter removal reaches 99.1%. The analysis of particulate matter in the process gas allowed us to determine that its content was 18.26%, and additionally it was indicated that it contained combustible parts, which undergo combustion in the combustion chamber. It was found that the content of particulate matter is reduced 11 times when compared to the process gas before the filter. An accurate estimation of particulate matter content in flue gas has been also shown for the system without the ceramic filter. As a result, the method allowed us to determine the overall efficiency of particulate matter removal using the ceramic filter, which is equal to 99.9% or 2 mg/m³ (N). The performed study shows that pre-combustion particulate matter removal is preferred over post-combustion particulate matter removal from flue gas. The reason is that the stream of process gas is several times smaller than the flue gas stream, thus the required size of the filter is smaller. Furthermore, process gas filtering allows us to keep the heat transfer surfaces clean, which preserves high thermal efficiency and durability of equipment. The presented results of performed tests are the early stage of the development of the technology of process gas refining in the waste gasification process. The final target is to reach standards similar to those in the case of natural gas.

We present a DFT analysis of the role of the Cu-Ni synergistic effect for the CO₂ reduction to C₂H₄, in comparison to the pure Cu catalyst. The analysis is focused on the thermodynamic stability of reactive intermediates along the proposed pathway of C₂ species formation. We have observed that the potential needed for the reaction decreases with the addition of Ni in the investigated model. In addition, we have observed the differences in the preferred pathway based on the significant differences in stability of the reactive intermediates depending on th Cu:Ni ratio. The results suggest that despite the fact the Cu surface is always exposed, and it is the only one that is able to directly interact with the intermediates, the presence of the Ni in the underlying sections of the crystal is significant enough to change the mechanism of the reaction.

This paper presents the effect of baffle geometry on the charging process of a low-temperature heat storage unit. Four different geometry variants were considered for this purpose. Each of them was simulated and the results were compared. The following parameters were selected as comparison criteria: the charging time of the heat storage unit, the change in the liquid and solid fractions of the phase change material, and the change in its temperature over time. The analysis showed that, independent from the heat transfer fluid velocity, the use of baffles did not significantly affect the charging time. Furthermore, the application of baffles of all studied types did not bring an essential decrease in charging time. It was found that the optimal solution was to use the simplest construction. Tuning of the HTF flow by the use of baffles is applicable to shell and tube heat exchangers; however, it adds no significant effects in the case of heat storage units of the proposed design. The abovementioned effect has been explained by the heat flux analysis, which shows that the heat transfer in the PCM is radically less intense, when comparing to the working fluid. Therefore, it is expected that enhancing the heat transfer between HTF and PCM material is possible by modifying the PCM–side design.