TY - GEN A1 - Kabat, Nancy A1 - Jende, Enrico A1 - Yücel, Fatma Cansu A1 - Stathopoulos, Panagiotis T1 - Thermodynamic analysis of a novel high-temperature heat pump cycle configuration based on the reversed Brayton cycle T2 - International journal of sustainable energy N2 - High-temperature heat pumps offer a promising approach to deliver CO$_2$-neutral process heat by upgrading waste heat with electricity from renewable resources. In this work, a heat pump configuration including multiple heat sinks and sources is presented and compared to the recuperated Brayton cycle. An exergy analysis is conducted by using numerical simulations to provide process heat at 250°C and process cooling at -30°C simultaneously. The results show, that a multi-stage compression leads to an improved overall performance for simultaneous heating and cooling. A parametric study presents the influence of the isentropic efficiency, heat exchanger effectiveness and heat sink and source inlet temperature on the second law efficiency. This study serves as a basis to gain a better understanding on the physics of the novel cycle, highlighting the potentials of improving the efficiency of Brayton heat pumps with cycle layouts adaptation and identify the most important components for minimizing exergy losses. Y1 - 2025 SN - 1478-6451 VL - 44 IS - 1 SP - 1 EP - 37 PB - Taylor & Francis CY - Abingdon, Oxon ER - TY - GEN A1 - Tran, A. Phong A1 - Stathopoulos, Panagiotis T1 - Dynamic simulation and experimental validation of a high-temperature Brayton heat pump T2 - Applied thermal engineering N2 - The decarbonization of industrial process heating will require widespread adoption of high-temperature heat pumps. Brayton cycle heat pumps are capable of providing heat at temperatures that currently cannot be achieved by conventional vapor-compression cycle heat pumps. However, significant challenges remain in adapting these systems to industrial applications, particularly with regard to operational safety, control strategies, and flexibility in response to varying operational conditions. This study presents a dynamic model of a closed-loop Brayton cycle heat pump capable of producing temperatures of 250 °C and higher, validated using experimental data. The physics-based model implemented in Modelica captures key thermodynamic processes and system dynamics, including thermal inertia and volume dynamics. An optimization-based method is used to calibrate model parameters, minimizing the error between measured and simulated data. Given the significant impact of the compressor on overall heat pump performance, a novel calibration method is introduced to adjust an existing compressor map using limited measurement data. This approach ensures that the compressor behavior is represented with sufficient accuracy, smoothness, and numerical robustness. The calibrated model achieves mean-normalized root mean squared errors (NRMSE) ranging from 0.12 % to 1.46 % for temperatures, pressures, and mass flow rates. The model is applied to examine the system’s start-up and deceleration sequences, offering insights into compressor stability and heat exchanger temperature profiles. These results demonstrate the model’s utility for control design, performance evaluation, and stability analysis. KW - High temperature heat pump KW - Brayton cycle KW - Dynamic simulation KW - Modelica KW - Process heat Y1 - 2025 U6 - https://doi.org/10.1016/j.applthermaleng.2025.126536 SN - 1359-4311 VL - 274, Part B SP - 1 EP - 13 PB - Elsevier BV CY - Amsterdam ER - TY - GEN A1 - Schaffrath, Robert A1 - Stathopoulos, Panagiotis A1 - Schmitz, Andreas A1 - Nicke, Eberhard T1 - Multistage turbomachinery optimization for high-temperature heat pumps with the reverse rankine cycle T2 - Journal of turbomachinery N2 - The electrification of process heat generation will be a key to achieving carbon neutrality in the coming decades. One of the most promising approaches is to replace conventional heat supply systems with high-temperature heat pumps (HTHPs). A promising heat pump concept is based on the reverse Rankine cycle that uses water as its working fluid. By using turbomachinery for the compression process in this cycle, the performance of the HTHP can be increased compared to the volumetric displacement systems, like screw or piston compressors. Although the design of the compressor geometry can be done sequentially in relation to the HTHP cycle design, better results can be obtained by an approach that integrates turbomachinery and the thermodynamic cycle design. Against this background, an automated optimization method for a reverse Rankine HTHP with two radial turbo-compressors in series is presented. In contrast to the current state of the art, the presented novel optimization approach uses 3D computational fluid dynamics data to calculate the compressor’s performance. Furthermore, the integration of low-fidelity compressor specific reduced-order models are used to accelerate the gradient-free optimization process by a CO-Kriging surrogate model. The advantages of the novel approach are justified by comparing the numerical effort and the final values of the optimization objectives. KW - Reverse Rankine cycle KW - Turbomachinery optimization KW - Centrifugal compressor KW - Centrifugal compressors and pumps KW - Compressor Y1 - 2025 U6 - https://doi.org/10.1115/1.4068480 SN - 1528-8900 VL - 147 IS - 111003 SP - 111003-1 EP - 111003-12 PB - ASME CY - New York, NY ER - TY - GEN A1 - Kabat, Nancy A1 - Jende, Enrico A1 - Yücel, Fatma Cansu A1 - Stathopoulos, Panagiotis T1 - Thermodynamic analysis of a novel high-temperature heat pump cycle with inter cooled compression and reheated expansion based on the reversed Brayton cycle T2 - International journal of sustainable energy N2 - High temperature heat pumps offer a promising approach to deliver CO2-neutral process heat by upgrading waste heat with electricity from renewable resources. In this work, a heat pump cycle including inter cooled compression and reheated expansion is presented and compared to the simple Brayton cycle. Numerical simulations are used to investigate the provision of process heat at 250°C and process cooling at -30°C. An exergy analysis and parameter study is carried out. The results show an improved performance of the complex cycle as a result of more efficient temperature profiles improving the exergy utilisation. While previous studies often consider idealised process variants or are focused on individual purposes, the present work contributes to the analysis and evaluation of complex cycles with multi-stage process control while simultaneously supplying heat and cold. A deeper understanding of the thermodynamic interactions provides a reliable basis for the energy-related design of systems with multiple temperature levels. KW - High-temperature heat pump KW - Brayton cycle KW - Inter cooled compression KW - Reheated expansion KW - Exergy analysis KW - Parametric study Y1 - 2025 U6 - https://doi.org/10.1080/14786451.2025.2515452 SN - 1478-6451 VL - 44 IS - 1 SP - 1 EP - 37 PB - Taylor & Francis CY - Abingdon, Oxon ER - TY - GEN A1 - Bouras, Dikra A1 - Fellah, Mamoun A1 - Barille, Regis A1 - Obrosov, Aleksei A1 - El-Hiti, Gamal A. T1 - Production of novel Zr–Mg nanoceramics based on kaolinite clay with strong antibacterial activity T2 - Ceramics International N2 - Gram-negative bacteria Pseudomonas putida, Gram-positive Bacillus subtilis, and Staphylococcus aureus were utilized as test samples to evaluate the antibacterial characteristics of DD3-clay/MgO and DD3+38 wt% ZrO2-clay/MgO nanoparticles. The ceramic powders prepared by a thermal autoclave method are characterized before and after Mg addition by SEM, EDX, XRD, IR, UV–visible, and TEM in order to investigate microstructure, phase, and surface morphology. The results showed that after adding Mg, it led to the deformation of the crystal lattices of (mullite, zirconium silicate, and zirconium oxide) together with a decrease in particle size (75–103 nm) and a complete change in its shape from nanotube to nanospherical, as observed by SEM and TEM analyses. It also confirmed by UV–visible spectroscopy that the addition of Mg increases the absorbance accompanying a decrease in the energy gap of 1.91, 1.74, 1.73, and 1.43 eV corresponding to DD3, DD3Z, DD3/30 wt% Mg and DD3Z/30 wt% Mg respectively. The antibacterial mechanism is related to the size of the particles, the solvent used for powder dissolution, the nanoparticle's size when they come into touch with bacteria, and the generation of reactive oxygen species (ROS: ˙O2−, ˙OH, and H2O2). It was observed that the anti-bacterial activity is enhanced with 10 wt% and 30 wt% of Mg added to a modified ceramic powder. Also, more O2− is formed on the surface of the prepared powder, which penetrates the bacterial cell and destroys it. The nanocomposite particles showed remarkable antibacterial activity when they were dissolved in DMSO compared to methanol and chloroform as organic solvents. The aim is to enrich knowledge on the antibacterial activities of metal nanoparticles (ZrSiO4 and MgO) on three bacterial strains with different Grams due to their extensive involvement in the phenomena of contamination and infection encountered in the medical field. The synthesized nanoparticles have good antimicrobial activity against all strains tested. A maximum inhibition zone of 35 ± 0.2 mm was obtained with S. aureus, a zone of 23 ± 0.46 mm with P. putida and a zone of 27 ± 0.46 nm with B. subtilis for DD3/30 wt% Mg and an inhibition zone of 38 ± 0.93 mm, 26 ± 0.24 nm and 17 ± 0.33 nm was obtained with same strains for DD3Z/30 wt% Mg, respectively. KW - DD3 + 38 wt% ZrO2/Mg KW - Nanoparticles KW - Synthesis KW - Antibacterial activity KW - Transmission electron microscope KW - Nanomaterial Y1 - 2024 U6 - https://doi.org/https://doi.org/10.1016/j.ceramint.2024.05.091 SN - 1873-3956 VL - 50 IS - 16 SP - 27949 EP - 27960 PB - Elsevier ER - TY - GEN A1 - Hasanuzzaman, Gazi A1 - Buchwald, Tom A1 - Schunk, Christoph A1 - Schröder, Andreas A1 - Egbers, Christoph A1 - Hampel, Uwe T1 - DATIV—remote enhancement of smart aerosol measurement system using raspberry Pi-based distributed sensors T2 - Sensors N2 - Enclosed public spaces are hotspots for airborne disease transmission. To measure and maintain indoor air quality in terms of airborne transmission, an open source, low cost and distributed array of particulate matter sensors was developed and named Dynamic Aerosol Transport for Indoor Ventilation, or DATIV, system. This system can use multiple particulate matter sensors (PMSs) simultaneously and can be remotely controlled using a Raspberry Pi-based operating system. The data acquisition system can be easily operated using the GUI within any common browser installed on a remote device such as a PC or smartphone with a corresponding IP address. The software architecture and validation measurements are presented together with possible future developments. KW - Aerosol transport, indoor ventilation, sensors, measurement, aerodynamics Y1 - 2024 UR - https://www.mdpi.com/1424-8220/24/13/4314 U6 - https://doi.org/10.3390/s24134314 VL - 24 SP - 1 EP - 12 ER - TY - GEN A1 - Borcia, Ion-Dan A1 - Richter, Sebastian A1 - Borcia, Rodica A1 - Schön, Franz-Theo A1 - Harlander, Uwe A1 - Bestehorn, Michael T1 - Wave propagation in a circular channel: sloshing and resonance T2 - The European Physical Journal Special Topics N2 - Surface wave resonance of a liquid (water) layer confined in a circular channel is studied both experimentally and numerically. For the experiment, eight unevenly distributed ultrasonic distance sensors measure the local height of the wave surface. The resonance curves show maxima only for odd multiples of the fundamental resonance frequency . We explained this behavior using a simple intuitive “ping-pong” like model. Collision of wave fronts can be observed for higher frequencies. Also, the wave reflection on the walls can be treated as wave collision with itself. The non-linearity seems to be weak in our study so the delay in the wave propagation before and after the collision is small. Time-space plots show localized propagating waves with high amplitudes for frequencies near resonance. Between the peaks low amplitude and harmonic patterns are observed. However, for higher frequencies, the frequency band for localized waves becomes wider. In the Fourier space-time plane, this can be observed as a point for the harmonic patterns or a superposition of two lines: one line parallel to wave-vector k axis corresponding to the excitation frequency and a second line with inclination given by wave propagation velocity . For planned future work, this result will help us to reconstruct the whole water surface elevation using time-series from only a few measurement points Y1 - 2023 UR - https://link.springer.com/article/10.1140/epjs/s11734-023-00790-z U6 - https://doi.org/10.1140/epjs/s11734-023-00790-z SN - 1951-6401 SN - 1951-6355 VL - Vol. 232 IS - 4 SP - 461 EP - 468 ER - TY - GEN A1 - Schön, Franz-Theo A1 - Bestehorn, Michael T1 - Instabilities and pattern formation in viscoelastic fluids T2 - The European Physical Journal Special Topics Y1 - 2023 UR - https://link.springer.com/article/10.1140/epjs/s11734-023-00792-x U6 - https://doi.org/10.1140/epjs/s11734-023-00792-x SN - 1951-6401 VL - Vol. 232 IS - 4 SP - 375 EP - 383 ER - TY - GEN A1 - Buchwald, Tom A1 - Hasanuzzaman, Gazi A1 - Merbold, Sebastian A1 - Schanz, Daniel A1 - Egbers, Christoph A1 - Schröder, Andreas T1 - Large-scale flow field and aerosol particle transport investigations in a classroom using 2D-Shake-The-Box Lagrangian Particle Tracking T2 - Heliyon Y1 - 2023 U6 - https://doi.org/10.1016/j.heliyon.2023.e22826 SN - 2405-8440 VL - 9 IS - 12 ER -