The article presents results of thermodynamic analysis using a zero-dimensional mathematical models of a negative CO₂ emission power plant. The developed cycle of a negative CO₂ emission power plant allows the production of electricity using gasified sewage sludge as a main fuel. The negative emission can be achieved by the use this type of fuel which is already a “zero-emissive” energy source. Together with carbon capture installation, there is a possibility to decrease CO₂ emission below the “zero” level. Developed models of a novel gas cycle which use selected codes allow the prediction of basic parameters of thermodynamic cycles such as output power, efficiency, combustion composition, exhaust temperature, etc. The paper presents results of thermodynamic analysis of two novel cycles, called PDF0 and PFD1, by using different thermodynamic codes. A comparison of results obtained by three different codes offered the chance to verify results because the experimental data are currently not available. The comparison of predictions between three different software in the literature is something new, according to studies made by authors. For gross efficiency (54.74%, 55.18%, and 52.00%), there is a similar relationship for turbine power output (155.9 kW, 157.19 kW, and 148.16 kW). Additionally, the chemical energy rate of the fuel is taken into account, which ultimately results in higher efficiencies for flue gases with increased steam production. A similar trend is assessed for increased CO₂ in the flue gas. The developed precise models are particularly important for a carbon capture and storage (CCS) energy system, where relatively new devices mutually cooperate and their thermodynamic parameters affect those devices. Proposed software employs extended a gas–steam turbine cycle to determine the effect of cycle into environment. First of all, it should be stated that there is a slight influence of the software used on the results obtained, but the basic tendencies are the same, which makes it possible to analyze various types of thermodynamic cycles. Secondly, the possibility of a negative CO₂ emission power plant and the positive environmental impact of the proposed solution has been demonstrated, which is also a novelty in the area of thermodynamic cycles.

Sewage sludge is a residue of wastewater processing that is biologically active and consists of water, organic matter, including dead and living pathogens, polycyclic aromatic hydrocarbons, and heavy metals, as well as organic and inorganic pollutants. Landfilling is on the decline, giving way to more environmentally friendly utilisation routes. This paper presents the results of a two-stage gasification–vitrification system, using a prototype-entrained flow plasma-assisted gasification reactor along with ex situ plasma vitrification. The results show that the use of plasma has a considerable influence on the quality of gas, with a higher heating value of dry gas exceeding 7.5 MJ/m_N³, excluding nitrogen dilution. However, dilution from plasma gases becomes the main problem, giving a lower heating value of dry gas with the highest value being 5.36 MJ/m_N³ when dilution by nitrogen from plasma torches is taken into account. An analysis of the residues showed a very low leaching inclination of ex-situ vitrified residues. This suggests that such a system could be used to avoid the problem of landfilling significant amounts of ash from sewage sludge incineration by turning inorganic residues into a by-product that has potential use as a construction aggregate.

The Navier–Stokes slip boundary conditions are considered as conditions following from the mass and momentum balances within a thin, shell-like moving boundary layer. A problem of consistency between different models, that describes the internal and external friction in a viscous fluid, is stated within the framework of a proper form of the layer momentum balance. Appropriate constitutive equations for friction forces are formulated. The common features of the Navier, Stokes, Reynolds, and Maxwell concepts of a boundary slip layer are revalorized and discussed. Different mobility mechanisms connected with the transpiration phenomena, important for flows in micro- and nanochannels, are classified as a part of equations for the external friction.

In this publication, we present an energy and exergy analysis of the Szewalski binary vapor cycle based on a model of a supercritical steam power plant. We used energy analysis to conduct a preliminary optimization of the cycle. Exergy loss analysis was employed to perform a comparison of heat-transfer processes, which are essential for hierarchical cycles. The Szewalski binary vapor cycle consists of a steam cycle bottomed with an organic Rankine cycle installation. This coupling has a negative influence on the thermal efficiency of the cycle. However, the primary aim of this modification is to reduce the size of the power unit by decreasing the low-pressure steam turbine cylinder and the steam condenser. The reduction of the “cold end” of the turbine is desirable from economic and technical standpoints. We present the Szewalski binary vapor cycle in addition to a mathematical model of the chosen power plant’s thermodynamic cycle. We elaborate on the procedure of the Szewalski cycle design and its optimization in order to attain an optimal size reduction of the power unit and limit exergy loss.

The need of reformulation for basic concepts of fluid mechanics in order to account some enhancement phenomena in micro- and nano-flows is presented in the paper. The work is a general formulation of angular velocity slip condition which is developed from primary principles. It is postulated that the different slipping phenomena take place within a thin shell-like layer where a material particle undergoes independently: the slip velocity and angular slip velocity. We suppose also that the molecules rolling at the layer can give a serious contribution to the mass flow enhancement, and therefore, it can be a reason to inclusion of a mathematical modeling for molecules angular momentum. In this paper, we propose the general form of an angular momentum balance for the shell-like layer. This balance is expressed by the surface divergence of an unsymmetric surface stress and an unsymmetric surface couple stress, either by the bulk momentum and bulk moment of momentum or by a surface friction torque. With constitutive relations appropriate for a linear, viscous, isotropic fluid and the constitutive relation for frictional resistance, we obtain generalized Navier-type boundary equations for the slip velocity and the angular slip velocity. As special cases, Poisson’s type boundary condition and Aero–Bulygin–Kuvshlinskii’s angular slip condition are obtained. Proposed here boundary conditions have few applications in modeling of complex nano-flows phenomena. For instant, recently discovered electropumping phenomena by De Luca et al. (J Chem Phys 138:154712-1–154712-10, 2013a) are based on nano-coupling of angular momentum with linear momentum and the electroosmotic draining effect. The theoretical background relies upon different angular velocity slip of dipolar liquids when confined between hydrophobic and hydrophilic solid surfaces—this phenomenon combined with applied rotating electric field leads to pumping of liquid. In our opinion, a concept of angular velocity slip leads to an explanation of the electropumping effect enhancement in nano-channels.

Numerical models of geothermal doublet allows us to reduce the high risk associated with the selection of the most effective location of a production well. Furthermore, modeling is a suitable tool to verify possible changes in operational geothermal parameters, which guarantees liveliness of the system. An appropriate selection of software as well as the methodology used to generate numerical models significantly affects the quality of the obtained results. In this paper, the authors discuss the influence of such parameters as grid density and distance between wells on the efficiency of geothermal heating plant. The last stage of the analysis was connected with estimation of geothermal power potential for a hypothetical geothermal doublet. Numerical simulations were carried out using the TOUGH2 code, which applies the finite-difference method. The research was conducted in the Szczecin Trough area (NW Poland), based on archival data from Choszczno IG-1 well. The results demonstrated that in the studied case of the Choszczno region, the changes in the distance of boreholes can have a visible influence on obtained results; however the grid density of the numerical model did not achieve a significant impact on it. The results show the significant importance of numerical modeling aimed at increasing the efficiency of a potential geothermal heating plant.