Title: "Development of a new cooling system for photovoltaic modules with a sun-tracking
system"

Abstract: The integration of renewable energy sources in energy production has become
imperative as the world transitions towards a greener future. The growing demand for
sustainable and efficient energy leads researchers to develop hybrid energy systems.
Photovoltaic/thermal systems (PV/T) drew huge attention from researchers due to their
benefits compared to stand-alone photovoltaic and solar-thermal (ST) systems, as PV/T
systems are hybrid energy systems that simultaneously convert solar energy into electrical
and thermal energy. Acknowledging the current thresholds of maximum thermal efficiency
achieved by the PV/T modules proposed in the literature and commercially available PV/T
modules, typically hovering between 30% and 85%, the research was focused on inventing a
highly efficient, easy-to-produce, advanced, and compact cooling system for PV modules.
The seminar will provide research methodology employed while designing a highly efficient
cooling system that can maximize the cooling of the PV module and harvest the waste heat.
The author will present test results of indoor and outdoor experiments of the designed
system.

Presenter: Mehmet Ali Yildirim, mgr. inż, Ph.D. Candidate in implementation doctorate
program (Doktorat Wdrożeniowy) at the Energy Department of the Cracow University of
Technology. As part of the implementation doctorate program, he works in a private
renewable energy company and specializes in photovoltaic cooling technologies and heat
transfer. The research was conducted under the scientific supervision of dr hab. inż. Artur
Cebula, Prof. PK and dr hab. inż. Piotr Cisek.

Time/Location: 2024.04.26, 9:15 online

Title: "Experimental investigations of the vaporization of isopropanol drops under low pressure conditions"

Abstract: Water is widely recognized as an environmentally-friendly refrigerant. However, the vaporization phenomena occurring at low pressures in evaporators remain not well documented. Pool boiling of water under low pressure conditions exhibits limitations attributable to the large size of nucleation bubbles, leading to dry areas on the heat exchange surface. Nevertheless, leveraging the bubble size in a spray cooling heat exchanger could effectively cover a larger surface area, thereby augmenting the vaporization surface and the efficiency of the evaporators. Previous experimental studies have demonstrated that the vaporization of water drops under low-pressure conditions could actually be favourable to a thermally-controlled generation of a spray. To generalize these observed behaviours, a test campaign involving another fluid vaporizing at a low pressure, namely isopropanol, was conducted in the Politechnika Wrocławska. The experimental setup enables the controlled deposition of isopropanol drops onto a heated wall under low-pressure, saturation conditions. Integration of a high-speed camera with thermocouples and pressure sensors facilitates real-time monitoring of observed behaviours within the depressurized tank. Isopropanol exhibits same explosive boiling behaviour in spreading its volume across the surface, thereby creating a thermal spray that atomizes the deposited drop, owing to the nucleation and growth of large bubbles of vapour inside the drops. These results confirm that the application of such a thermal spray holds significant promises for enhancing the efficiency of low-pressure evaporators.

Presenter: Antoine Courouble, MSc, is a PhD candidate at INSA Lyon, in the CETHIL laboratory. The research is conducted under the scientific supervision of Romuald Rullière, PhD, Assoc. Prof. and Prof. Jocelyn Bonjour.

Time/Location: 2024.03.22, 9:00 online

Title: "Steam bubble formation in pool boiling of water in a narrow vertical channel under subatmospheric conditions"

Abstract: Pool boiling of natural refrigerants, especially water, is still one of the most popular heat transfer topics. The data available in the literature usually refer to atmospheric pressure conditions, which makes it impossible to directly compare it with boiling processes occurring under low-pressure. During subatmospheric pressure boiling, hydrostatic pressure, which is often neglected during boiling at atmospheric pressure, plays a special role due to its order of magnitude. The seminar will present experimental as well as numerical results obtained during a three-month internship at the Conservatoire national des arts et métiers (CNAM) in Paris. The measurements made concerned the pool boiling of water in a rectangular evaporator, consisting of two narrow vertical channels separated by a plate. Using a high-speed camera, it was observed how the very narrow space (2 mm) of the channel affected the shape of vapor bubbles at low pressure. The resulting bubbles exhibited a variety of geometric features at the top of the interface, and both dendritic shapes, waves and a perfectly circular surface were observed. In addition, the focus was on the effect of the depth of the nucleation site and on the role of hydrostatic pressure. In addition to the experimental results, it was decided to map the selected conditions through CFD simulation, which is still being pursued at the Wrocław University of Science and Technology.

Presenter: Dominika Kaczmarek, MSc, is a PhD candidate at the Department of Thermal Sciences. The research is conducted under the scientific supervision of Bartosz Zajączkowski, PhD DSc, Assoc. Prof.

Time/Location: 2024.02.21, 9:30 online

Title: "Nanofluids as a novel material for heat transfer fluids in solar energy systems: opportunities and drawbacks"

Abstract: Nanofluids, or suspensions of nanoparticles, are complex systems with unique thermophysical properties, including optical properties, which, combined with high thermal conductivity, make these materials interesting for applications in solar systems. The seminar will provide information on the basic properties of nanofluids and the resulting possible use of these fluids in heat transfer and solar energy generation systems. The author will also delve into the problems posed by the use of nanofluids and outline the drawbacks of such systems.

Presenter: Gaweł Żyła, PhD DSc, Assoc. Prof., research and teaching fellow in the Department of Physics and Medical Engineering at Rzeszów University of Technology. He specializes in the experimental study of the fundamental physical properties of nanomaterials.

Time/Location: 2023.11.22, 9:15 at bdg. A4, rm. 263

Title: "Heat transfer during flow boiling in minispaces with different geometries"

Abstract: The increase of energy requirements with the trend toward miniaturization of modern equipment is linked to technological advances. Methods are constantly being sought to intensify heat transfer, with phase change heat transfer increasing the efficiency of the process. The presentation will include experimental results, along with consideration of the mathematical methods used in the calculations. The design of the experimental setups will be discussed, the most important element of which is a test module with different geometries: with rectangular-section minichannels, with annular-section minichannels, and with a set of rectangular-section minichannels. The module provides a single or multiple mini-spaces with variable spatial orientation, along which the working fluid (cooling fluids, distilled water) heated by the heater flows. Experiments are carried out under steady-state and time-varying conditions. The temperature of the heater is measured by several methods: liquid crystal thermography, thermal imaging and with the help of thermocouples, simultaneous two-phase flow structures are recorded. The purpose of the experiments was to collect data that, using the proposed models and mathematical methods, allow the determination of local values of the heat transfer coefficient at the interface: heating surface-boiling liquid flowing along the minipace. The results of the analysis of the collected results will be presented, the purpose of which was to determine the intensity of the heat transfer and to identify the influence of important factors on the initiation and development of boiling. The selected factors include the development of the heater surface, the spatial position of the minispace, the mass flux of the fluid flow and its pressure, the boiling medium and the geometric parameters of the test module. Among other things, chosen methods for solving one- and two-dimensional problems used so far in calculations (including numerical) will be discussed, as well as observed two-phase flow structures.

Presenter: Prof. Magdalena Piasecka, head of the Department of Mechanics and Thermal Processes of Kielce University of Technology, specialising in flow boiling heat transfer in minigaps and renewable energy sources.

Time/Location: 2022.12.02, 9:15 online

Title: "Effective use of wastewater injection to improve electrostatic precipitator operation"

Abstract: The presentation will desctibe the results of research on industrial installation of conditioning liquid injection into flue gas ducts before electrostatic precipitator in order to improve its efficiency. The described research is a continuation of the work carried out by the Division of Sustainable Energy Technologies over the past 9 years on the technology for reducing mercury emissions by injection of liquid oxidizing additives into boiler flue gases. The research was carried out in February 2022 on the injection system built as part of the modernization of the KW5 water boiler electrostatic precipitator at ZEW KOGENERACJA S.A.
The primary goal of the investment was to achieve dust concentrations behind the electrostatic precipitator below 25 mg/m3 in reference conditions. The experience gained by the Team during previous research projects (cooperation with industrial partner RAFAKO S.A.) allowed us to propose a solution involving the injection of a conditioning liquid in the form of water or a mixture of water and wastewater from IMOS (wet flue gas desulfurization instalation). Considering the globally visible trend to achieve zero-emission wastewater management at industrial sites, the proposed solution can help to achieve this goal.
The presentation will describe the results of measurements of gaseous and dust emissions, as well as the results of analysis of selected media. The obtained results fully confirmed the applicability of the proposed solution to reduce dust emissions downstream of the electrostatic precipitator, especially for existing facilities, without the need for costly renovation and modernization. In addition, the installation makes it possible to reduce mercury and NOx emissions from boiler flue gases by injecting appropriately selected oxidizing additives.

Presenter: Arkadiusz Świerczok, PhD DSc, Assoc. Prof., Division of Sustainable Energy Technologies, Department of Thermal Sciences

Time/Location: 2022.11.18, 09:15, bdg. A4, rm. 263

Title: "Selected issues on the construction, operation and safety of a PWR nuclear reactor."

Abstract: On October 2, 2020. The Council of Ministers adopted a Resolution (No. 141) on updating the "Polish Nuclear Power Program." The goal of the PNPP is to increase the country's energy security, mainly by diversifying the fuel base and directions of supply of energy carriers, and replacing the aging fleet of high-emission coal-fired units (operating on a capacity basis) with zero-emission units. This will mean a significant reduction in atmospheric greenhouse gas emissions from the electricity sector and low environmental impact. The implementation of nuclear power, moreover, will contribute to halting the growth and maintaining energy prices for consumers at an acceptable level and, due to the size of the investment, will provide a significant boost to the country's economic development.
The PNPP schedule assumes the construction and commissioning of nuclear power plants in Poland with a total installed capacity of 6 to 9 GWe, based on large-scale, pressurized water nuclear reactors of the PWR generation III and III+. This is a proven technology, well known by the nuclear regulatory institutions, characterized by a high level of safety and providing greater site selection (smaller restricted area).
The presentation will discuss the construction and principle of operation of a pressurized water reactor (PWR). Selected issues of the scope of operation and safety of nuclear power plants with pressurized water reactors will be discussed.

Presenter: Wojciech Zacharczuk, PhD, Division of Nuclear Power Engineering, Department of Thermal Sciences

Time/Location: 2022.10.28, 9:15 at bdg. A4, rm. 263

Title: "Laminar Pipe Flow under the Influence of Magnetic Field"

Abstract: Magnetic influence on ferronanofluid flow is gaining increasing interest from not only the scientific community but also industry. The aim of our study is the examination of the potentials of magnetic forces to control heat transfer. Experiments are conducted to investigate the interaction between four different configurations of permanent magnets and laminar pipe flow with mixed convection. For that purpose a pipe flow test rig is operated with a water-magnetite ferronanofluid. The Reynolds number is varied over one order of magnitude (120–1,200). To characterise the employed suspension, density, solid content, viscosity, thermal conductivity, and specific heat capacity are measured. It is found that, depending on the positioning of the magnet(s) and the Reynolds number, heat transfer is either increased or decreased. The experiments indicate that this is a local effect. After relaxation lengths ranging between 2 and 3.5 lengths of a magnet, all changes disappeared. The conclusion from these findings is that magnetic forces are rather a tool to control heat transfer locally than to enhance the overall heat transfer of heat exchangers or the like. Magnetically caused disturbances decay due to viscous dissipation and the flow approaches the basic state again.

Presenter: PD Dr.-Ing. habil. Matthias H. Buschmann works as a Senior Researcher/Project Manager at Institut für Luft- und Kältetechnik gemeinnützige Gesellschaft mbH in Dresden, Germany. He is a theoretician in fluid mechanics, but is also highly interested in heat transfer experiments. He studied at Universities of Dresden, Karlsruhe and Melbourne and received his PhD and habilitation at University of Dresden. His research interests include phase change heat and mass transfer, nanofluid flow and heat transfer, and wall-bounded turbulence. He has contributed to more than 40 full papers and numerous conference papers. 

Time/Location: 2022.09.29, 11:15, bdg. A4, rm. 263

Title: "Experimental studies and modeling of the operation of low-pressure liquid-gas two-phase ejectors"

Abstract: This thesis is devoted to the study of low-pressure liquid-gas ejectors with simultaneous compression and mixing effects. In this work, a prediction tool for the performance parameters of a liquid-gas ejector is developed, particularly in the low-pressure operating parameters. As part of the work, an experimental rig was prepared on which systematic experimental investigations were carried out over a wide range of driving pressures, suction pressures and compression for ejectors with different geometrical parameters. Based on these, the performance characteristics were investigated, which showed close geometrical relationships with respect to the performance parameters of the device. Based on the performance characteristics, a criterion relationship was formulated for the velocity coefficient of the mixing chamber. It was pointed out that although it has been shown in the literature to be treated as constant and unrelated to the flow structures present in the streamer, the experimental studies carried out indicate that this coefficient is variable and dependent on the operating parameters of the ejector. Additionally, the efficiency of the liquid-gas streamer was analyzed in this study. The location and length of the mixing wave forming in the mixing chamber were analyzed. Its location and length dimension are crucial in order to select a suitable mixing chamber. A criterion relationship was developed that describes the location of the mixing wave and its length. In addition, the paper presents an example application of mechanisms describing the operation of an ejector in an application intended for a gas purification system. Thus, practical application of the solutions and possibilities of future implementations in technology are presented.

Presenter: Mateusz Kędzierski, MSc is a PhD student at the Department of Thermal Engineering of the Bialystok University of Technology. His research is carried out under the scientific supervision of Prof. Dariusz Butrymowicz. At the same time, while working on his PhD thesis, he worked as a designer of thermal-flow systems, and currently works as a manager of energy projects.

Date/Location: 2022.06.24, 9:15, online.

Title: "Investigation of the basic physical properties of microencapsulated phase change material (mPCM) slurries"

Abstract: The working fluids that carry energy in heat transfer systems are undergoing a constant change. Miniaturization and the necessity to remove more and more heat from heated surfaces have caused classical working fluids to reach the end of their capabilities. Hence the concept of implementing additives in the form of nanoparticles or phase change materials, which are becoming more and more popular. Phase Change Material (PCM) is a material that undergoes a solid-liquid phase change at a "constant" temperature due to the transfer of significant amount of thermal energy. Currently used PCMs are characterized by a phase change temperature of -100 °C to + 400 °C, depending on the type of material. The heat of phase change can range from 100 kJ to 1 MJ per kilogram of mass. Encapsulating the PCM material allows, in addition to increasing the heat transfer coefficient (due to the housing material), to initiate the phase transformation simultaneously in each enclosed volume. This increases the heat transfer surface area and additionally: prevents direct contact of the PCM active substance with the environment, reduces the risk of leakage, extends the life of the PCM, reduces problems resulting from the separation of liquid and solid phases. Encapsulation techniques can be divided into macro, micro and nano encapsulation. Microencapsulation is a process in which PCM particles (approximately 0.1 - 1000 µm in diameter) are coated with a thin layer - generally a polymer up to a few micrometers thick. With such small capsule sizes, it is possible not only to wet the capsules with a working fluid, but to flow as a whole - a suspension composed of microcapsules filled with a phase change material in a base fluid.

The presentation is planned to show selected results of own laboratory investigations concerning the determination of viscosity, density, specific heat/enthalpy of phase change, and flow resistance of a suspension composed of water and microencapsulated PCM. The properties of the suspension were determined for several different concentrations of mPCM over the temperature range at which PCM undergoes phase transformation. The influence of the PCM state of matter on the obtained quantities was evaluated.

Presenter: Krzysztof Dutkowski, PhD DSc, Assoc. Prof. of Koszalin University of Technology, an employee of the Department of Power Engineering, specialising in mechanics of working fluids in heat exchange systems.

Time/Location: 2022.06.10, 9:15, online

Title: "Experimental study of heat transfer in fluid with phase change material – PCM"

Abstract: Phase change dispersion (PCD) is a fluid consisting of a carrier fluid and a phase change material (PCM) dispersed in it, which allows latent heat to be exploited. Due to the phase change, PCD are efficient and promising working mediums. Their greatest ability is to store thermal energy more than single phase working fluids. Potential applications include refrigeration and heating systems. To effectively utilize the possibilities offered by PCD fluids, it is necessary to understand the heat transfer processes.

During this presentation, the results of the research performed during a research internship at INSA Lyon will be presented. The research concerns the heat transfer for a PCD during the cooling process, from 30°C to about 5°C for PCM with a crystallization point of 15°C. Measurements were performed for different flow rates and cooling temperature settings. The acquired data were used to determine heat transfer parameters such as Nusselt number. The presentation will also include future research plans for fluids using PCM in the form of the microencapsulated phase change material mPCM. The mPCM research will focus on heat transfer and testing the feasibility of using the mPCM fluid as a working medium with better performance than the fluids used currently.

Presenter: Bartłomiej Nalepa, MSc is a PhD candidate at the Department of Thermal Sciences. The research is conducted under the scientific supervision of Bartosz Zajączkowski, PhD DSc, Assoc. Prof.

Time/Location: 2022.06.03, 8:45, online.

Title: "Investigations of the NO₂ to N₂ reduction reaction via SO₃^2- under conditions prevailing in wet flue gas desulfurization installations"

Abstract: The presentation will provide the assumptions and preliminary results of the project funded under the research fund of the Department of Thermal Sciences. The aim of the project is to investigate the possibility of using the NO₂ to N₂ reduction reaction via sulfite ions in a wet flue gas desulfurization installation to reduce NO_x emissions. The awareness progress of the environmental effects of industrial pollutant emissions has resulted in the development of flue gas dedusting, desulfurization, and denitrification installations. In the Polish energy sector, a commonly used type of desulfurization installation is based on a wet lime method which uses a CaCO₃ sorbent suspension to wash flue gases flowing in a countercurrent. Due to the policy of the European Union in terms of tightening emission standards (BAT conclusions), the use of the phenomenon of NO₂ to N₂ reduction in the conditions prevailing in FGD creates an opportunity to meet them. The use of an already existing installation also has the advantage emerging from the fact that for older coal-fired units, there is no economic justification to equip them with dedicated installations. The presentation will include the results of laboratory and industrial tests.

Presenter: Dariusz Łuszkiewicz, PhD, Division of Sustainable Energy Technologies, Department of Thermal Sciences

Time/Location: 2022.05.13, 9:15 at bdg. A4, rm. 263

Title: "Droplets vaporization at low pressure conditions for different range of superheated surface temperature"

Abstract: Spray cooling belongs to the alternative cooling method which are used for shell tube heat exchangers or for cooling of flat surfaces. This technique enables to obtain greater heat transfer coefficients compared to the boiling or evaporation of a thin film of liquid particularly at low pressure conditions. As the fundamentals of the low-pressure evaporation process have not been studied in detail, investigation work is required to understand single droplet evaporation.

The presentation will include a report of a study carried out during a research internship at INSA Lyon. The measurements performed concerned the vaporization of droplets from a flat surface under reduced pressure. Droplets were generated for pressures of respectively: 2 kPa, 3 kPa, 4.5 kPa and 7 kPa and a surface superheat range from 0°C to 45°C. The methodology for calculating the energy associated with the vaporization of a single droplet and the heat transfer coefficients will be briefly discussed during this talk. The analysis results will include the influence of pressure and surface superheat on the type of droplet vaporization. The relationship between the heat transfer coefficient and the surface superheating temperature or the duration of the vaporization process will be highlighted as well.

Presenter: Wiktoria Lada, MSc is a PhD candidate at the Department of Thermal Sciences. The research is conducted under the scientific supervision of Bartosz Zajaczkowski, PhD DSc, Assoc. Prof.

Time/Location: 2022.05.06, 9:15 online 

Title: "Metrological analysis of the ultrasonic flowmeter application in a pipeline downstream of a gate valve"

Abstract: Flow rate measurements are among the most important measurements in engineering measurement practice. The determination of the flow rate of a medium plays a fundamental role in the preparation of mass and energy balances of thermal-fluid systems.  It is important to measure a velocity and a flow rate with the highest possible accuracy, as this information is most often widely used in the calculation process or in the operation of the control system of a given installation. The ultrasonic measurement method is often used due to its high accuracy and versatility of applications. This method is non-invasive. It enables flow measurement without the necessity of stopping the installation and does not interfere with the medium flow.

The presentation will discuss the methodology and results of tests performed with ultrasonic flowmeters with heads placed on the pipeline in nonstandard conditions, behind an obstacle disturbing the flow. Such a situation often occurs in measurement practice when, due to geometrical limitations, it is not possible to install the device while maintaining the straight sections of the pipeline behind the obstacle. The obstacle whose influence on the flow meter readings was analysed in the conducted tests was a knife gate valve. The presentation will indicate measurement recommendations for the optimum place to perform measurements in non-standard conditions. The results of tests carried out with a laser anemometer (LDA), on the basis of which the actual velocity distribution profiles were created, will be presented. The actual velocity distribution will be compared with the distorted flow velocity distribution models most commonly used in the literature. The method of measurement error compensation using the determined correction factor will also be discussed.

Presenter: Piotr Piechota, MSc is a PhD candidate at the Department of Thermal Sciences. The research is conducted under the scientific supervision of Artur Andruszkiewicz, PhD DSc, Assoc. Prof.

Time/Location: 2022.04.22, 9:15 at bdg. A4, rm. 263 

Title: "Experimental study of the influence of magnetic field on the physical properties of ferromagnetic nanofluid."

Abstract: Ferronanofluids are representants of nanofluids that are seen as a working fluids of the future, offering the possibility of increasing the efficiency of heat transfer devices. The magnetic properties of ferronanofluids put them in the spotlight of this group, because of the additional possibility of their control by a magnetic field. To discover the full potential of ferronanofluids and enable future adaptation to convective and phase-change heat transfer processes, research on their thermophysical properties is required. The presentation will focus on the methodology and results of research on the wettability of ferronanofluid containing magnetite nanoparticles on copper and aluminium surfaces and the influence of an external magnetic field on the dynamics of ferronanofluid droplets. The impact of the magnetic field presence during the drying of the ferronanofluid droplet on the crack network in the deposit will also be depicted.

Presenter: Robert Mulka, MSc is a PhD candidate in the Division of Refrigeration and Heat Pumps at the Department of Thermal Sciences. The research is conducted under the scientific supervision of Bartosz Zajączkowski, PhD DSc, Assoc. Prof.

Time/Location: 2022.03.18, 9:15 at bdg. A4, rm. 263