The high-energy requirements of cleanrooms are the main motivation for optimizing their operational conditions. The ventilation system consumes the most energy in order to ensure the precise air conditioning of the room (filtration, temperature, and humidity adjustment). The main function of the ventilation system is to keep particle concentration to a minimum. This work deals with the optimization of an experimental operating room via the optimization of air supply through the distribution element (laminar airflow ceiling) in the range of 0.15–0.25 m·s−1. The laminar airflow between the distribution element and the patient is influenced by the operating light and different airflow velocities. These factors affect changes in particle concentration. Ansys Fluent software was used to investigate the nature of the flow, velocity profiles, and particle trajectories. The results of our numerical simulation demonstrate that a suitable flow rate setting increases the efficiency of particle reduction in the operating table area by up to 54%, which can, in turn, reduce operating costs. The simulated air velocity profile was subsequently verified using the particle image velocimetry (PIV) method. The typical size of particles monitored for in cleanrooms is 0.5 μm according to ISO EN 7. Therefore, the results of this study should be helpful in correctly designing distribution elements for clean rooms.

The assessment of heating systems is not only interested in the efficiency of the heating system itself, but also in the quality of the environment that the heating system creates. The quality of the environment and the heat-humidity microclimate is closely related to thermal comfort. A suitable environment has a positive effect, for example, on the efficiency of work at the workplace. The range of temperatures, humidity and operating temperatures in workplaces is often also legally prescribed in such a way that there is no thermal discomfort for users in the heated space. In terms of savings, it is therefore best to use heating systems that can create a comfortable environment with the lowest possible energy costs. During their development, variations are possible with temperature gradients, the size of the heat exchange area, or the ratio of the radiant and convective components of heat transfer. When developing such systems, it is appropriate to consider CFD simulations. The comparison of the results of CFD simulation and experimental measurement is also in the following article, where the comparison of the operating temperature and the mean radiation temperature of two different heating systems in the model office is monitored.

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This paper focuses on the model of gas hydrate formation in an experimental device, which allows the circulation of the resulting mixture (water and gas) and significantly accelerates the process of hydrate formation in the laboratory. A 3D model was developed to better imagine the placement of individual parts of the device. The kinetics of hydrate formation were predicted from equilibrium values of chemical potentials. The aim of solving the equations of state gases in the mathematical model was to optimize the parameters involved in the formation of hydrates. The prediction of the mathematical model was verified by numerical simulation. The mathematical model and numerical simulation predict the chemical reaction evolving over time and determine the amount of crystallized water in the reactor. A remarkable finding is that the deviation of the model and simulation at the initiation the calculation of crystallized water starts at 76% and decreases over time to 2%. Subsequently, the number of moles of bound gas in the hydrate acquires the same percentage deviations. The amount of water supplied to the reactor is expressed by both methods identically with a maximum deviation of 0.10%. The different character is shown by the number of moles of gas remaining in the reactor. At the beginning of the calculation, the deviation of both methods is 0%, but over time the deviation slowly increases, and at the end it expresses the number of moles in the reactor with a deviation of 0.14%. By previous detection, we can confirm that the model successfully determines the amount of methane hydrate formed in the reactor of the experimental equipment. With the attached pictures from the realized experiment, we confirmed that the proposed method of hydrate production is tested and takes minutes. The article calculates the energy efficiency of natural gas hydrate in the proposed experimental device.

Accumulation of primary energy of natural gas is a perspective industrial area mainly for countries dependent on the import of energy and raw materials. Transporting and storage of natural gas is economically and technologically demanding, which is always reflected in the resulting price. Natural gas hydrates allow transport and storage at low pressures and relatively favorable temperatures. Another no less important area is the storage of energy in biogas plants where gas formation is time-dependent. Biogas hydrates would allow short-term storage at room temperature and atmospheric pressure. This article deals with the design of a functional prototype for the production of hydrates and numerical simulation.

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For countries with limited access to conventional hydrocarbon gases, methane hydrates have emerged as a potential energy source. In view of the European Union’s requirements to reduce the energy intensity of technological processes and increase energy security, it appears promising to accumulate natural gas and biomethane in the form of hydrate structures and release them if necessary. Storing gas in this form in an energy-efficient manner creates interest in developing and innovating technologies in this area. Hydrates that form in gas pipelines are generated by a more or less random process and are an undesirable phenomenon in gas transportation. In our case, the process implemented in the proposed experimental device is a controlled process, which can generate hydrates in orders of magnitude shorter times compared to the classical methods of generating natural gas hydrates in autoclaves by saturating water only. The recirculation of gas-saturated water has been shown to be the most significant factor in reducing the energy consumption of natural gas hydrate generation. Not only is the energy intensity of generation reduced, but also its generation time. In this paper, a circuit diagram for an experimental device for natural gas hydrate generation is shown with complete description, principle of operation, and measurement methodology. The natural gas hydrate formation process is analyzed using a mathematical model that correlates well with the measured hydrate formation times. Hydrates may become a current challenge in the future and, once verified, may find applications in various fields of technology or industry.

Various waste materials have energy potential. It is important to make use of this potential and prepare the product for further use by treating the waste. Treatments such as compressing waste into pellets leads to increasing the energy density of this fuel, which benefits transport and storage costs. However, low bulk density, high ash content, low-ash melting temperatures, and low calorific values of non-woody pellets can cause problems during their combustion. This article deals with the energy usage of walnut shells, which were blended with spruce sawdust in various amounts and compressed into pellets. The mechanical and energy properties of these were measured and compared with recommended or standardized values. The formed pellets met the quality limit for bulk density, ash content, moisture content, the content of nitrogen and sulfur, and net calorific value according to ISO 17225. However, low ash melting temperatures were noticed for pellets from pure walnut shells, and also lower mechanical durability for produced pellets with walnut shells contents higher than 10% were detected.