Wyniki wyszukiwania - BazTech

1

Numerical investigations on the impact of aortic arch inclusion on hemodynamics of abdominal healthy and aneurysmal aorta

Han Xinyi, Specklin Mathieu, Kouidri Smaine, Koskas Louise, Bakir Farid, Davaine Jean-Michel

Biocybernetics and Biomedical Engineering

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2026

|

Vol. 46, iss. 1

76--94

EN

This numerical study evaluates the impact of including the aortic arch in in-vivo and in-silico studies, by comparing an abdominal healthy aorta model to an aneurysmal one. CFD simulations were performed using OpenFOAM, with patient-specific blood flow data. Wall shear stress indices (TAWSS, OSI, RRT) and vortex distributions (Q criterion) were analyzed. The results show that the aortic arch amplifies blood flow disturbances, leading to a reduction in TAWSS and an increase in OSI, which may enhance the risk of potential thrombosis. Simplified models without the arch underestimate these effects. The influence of the aortic arch is more pronounced in the abdominal healthy aorta than in the abdominal aortic aneurysm, highlighting the importance of including it in hemodynamic simulations for a more accurate risk assessment.

2

Hydrodynamic Assessment of Distributed Propulsion Systems for Shallow-Draft Inland Vessels

Jurkovic Martin, Illes Ladislav, Sosedová Jarmila, Prabowo Aditya Rio, Melnyk Oleksiy, Stopka Ondrej

Polish Maritime Research

|

2025

|

nr 4

20--32

EN

This study investigates the hydrodynamic performance of three distributed propulsion configurations with distinct hull shapes. The influence of duct design and hull geometry on thrust, absorbed power, and the resulting thrust-topower ratio is explored, and a computational fluid dynamics analysis is conducted with a focus on the relationship between the hull and propulsion system at a constant speed of 3 m/s. The results indicate that a pontoon-shaped hull with matching propulsion configuration yields optimal performance, with superior thrust-to-power ratios and hydrodynamic efficiency. In addition, a comprehensive design graph is presented, with the intention of aiding ship designers in selecting suiTable propulsion configurations for specific vessel types. The findings highlight the importance of integrating hydrodynamic and performance criteria into the design of distributed propulsion systems, and provide insights for the development of next-generation efficient inland vessels. Overall, the study provides practical guidelines for optimising distributed propulsion layouts in shallow-water vessel design.

3

Optymalizacja komory spalania w miniaturowym silniku turbinowym

Dopieralski Marcin, Polak Filip

Journal of KONBiN

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2025

|

Vol. 55, iss.3

49--61

PL

Miniaturowe silniki turbinowe, ze względu na swoje niewielkie rozmiary i dużą siłę ciągu, znajdują coraz szersze zastosowanie w autonomicznych systemach zasilania i np. do modeli lotniczych, dronów, małych generatorów, eksperymentalnych pojazdów. Kluczowym wyzwaniem w ich rozwoju jest optymalizacja komory spalania, która bezpośrednio wpływa na wydajność, emisję i stabilność pracy silnika. Niniejszy artykuł koncentruje się na pytaniu, jak zaprojektować i zoptymalizować komorę spalania dla miniaturowego silnika turbinowego, aby osiągnąć maksymalną efektywność energetyczną przy zachowaniu kompaktowych wymiarów i niskiej emisji szkodliwych substancji. Celem badań było opracowanie nowatorskiej konstrukcji komory spalania, minimalizującej straty ciśnienia i zapewniającej efektywne spalanie paliwa w ograniczonej przestrzeni. W tym celu zastosowano metody numerycznej mechaniki płynów (CFD) do symulacji przepływów i procesów spalania w różnych konfiguracjach geometrycznych. W efekcie zaprojektowano komorę spalania i przeprowadzono symulacje, która wymaga dalszego przeprojektowania, tak aby zniwelować powstawanie niekorzystnych stref zawirowań powietrza. Wkład własny autorów obejmuje opracowanie innowacyjnej geometrii komory spalania oraz zastosowanie zaawansowanych algorytmów optymalizacyjnych w symulacjach CFD.

EN

Miniature turbine engines, due to their small size and high trust in aircraft, are finding increasing use in autonomous power systems and for e.g. model aircraft, drones, small generators, experimental vehicles. A key challenge in their development is the optimization of the combustion chamber, which directly affects engine performance, emissions and stability. This article focuses on the question of how to design and optimize a combustion chamber for a miniature turbine engine to achieve maximum energy efficiency while maintaining compact dimensions and low emissions. The goal of the research was to develop a novel combustion chamber design that minimizes pressure losses and ensures efficient fuel combustion in a limited space. To this end, computational fluid mechanics (CFD) methods were used to simulate flow and combustion processes in various geometric configurations. As a result of the research, a combustion chamber was designed and simulations were conducted, which requires further redesign to negate the formation of unfavourable air turbulence zones. The authors' own contributions include the development of innovative combustion chamber geometry and the application of advanced optimization algorithms in CFD simulations.

4

Computational fluid dynamics – based assessment of thermal comfort parameters in residential buildings in Amman: Implications for indoor environmental quality

Al-Zuriqat Mai Hathal, Obeidat Bushra

Journal of Ecological Engineering

|

2025

|

Vol. 26, nr 5

383--400

EN

With the increasing reliance on indoor living, the design of residential environments has become essential for ensuring occupant comfort, health, and well-being. This study evaluates thermal comfort variables—air temperature and relative humidity (RH)—in apartment buildings in Amman, Jordan, using computational fluid dynamics (CFD) simulations to assess the impact of spatial design parameters on indoor environmental quality. The findings reveal thermal deficiencies in existing apartment layouts, where low indoor temperatures (16.6 °C) and excessive humidity (94.96%) compromise indoor comfort. The study examines how optimizing wall insulation (phenolic foam, R = 5.7, 8 cm) and window-to-wall ratio (40%) can improve indoor air conditions. While previous research suggests that temperature and humidity influence airborne virus viability, this study does not directly investigate pathogen survival. Instead, it provides a data-driven assessment of indoor thermal comfort, offering insights for future research, design improvements, and policy considerations to enhance residential indoor environments.

5

Research on Cleaning the Bach Ho Field In-Field Pipeline from Msp-A To Msp-D using Foam Pig Technology

Nguyen Van Thanh, Nguyen Khac Long, Doan Thi Tram, Le Van Nam, Le Quang Duyen, Vu Viet Thanh, Nguyen Quoc Dung, Nguyen Quoc Nam

Inżynieria Mineralna

|

2025

|

Vol. 1, no. 2

925--933

EN

This paper presents the research and experimental results of applying pipeline cleaning technology using flexible pigs (Foam Pig/Gel) for the Bach Ho in-field oil and gas gathering pipeline, specifically the MSP-Ato MSP-B pipeline. This pipeline has a complex structure and is not equipped with traditional pig launching and receiving systems, making periodic cleaning difficult. The authors conducted Computational Fluid Dynamics (CFD) simulations to assess the theoretical feasibility of Foam Pig technology, alongside implementing two phases of actual industrial trials. Simulation results showed that Foam Pig could maintain its shape and high displacement efficiency under the actual conditions of the pipeline. Initial industrial trials faced challenges with gel durability, but after optimizing the chemical composition and improving the pig casting chamber (especially the vertical type), the technology achieved significant success in removing water and deposits from the pipeline. The paper also summarizes lessons learned and recommendations for widespread deployment of this technology.

6

Gas Phase Distribution in a Mixer with a Mechanical High-Speed Mixer – Case Study

Młynarczykowska Anna

Inżynieria Mineralna

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2025

|

Vol. 1, no. 1

189--193

EN

The mechanical mixing process is a common operation in the technological processes of many industries, also in the mineral processing. The separation of valuable mineral from gangue in the flotation chamber results in electrical power consumption of 1-10 kW/m3 and depending on the type of flotation machine. Air is introduced into the flotation chamber and the bubbles are dispersed using a rotorstator system, which simultaneously mixes the suspension with air bubbles. Flotation efficiency depends on tank shape, rotor and stator design, as well as operating conditions such as rotor speed, aeration rate, and suspension properties. Striving to reduce energy consumption while maintaining high process efficiency, optimizing the shape of the stator-rotor system is crucial. This system determines the distribution of bubble in flotation chamber and the occurrence of elementary flotation acts. The article presents experimental results from measurements of the velocity field of the water and air-water systems in a laboratory flotation chamber under various hydrodynamic conditions by using the digital image anemometry (PIV) technique and numerical simulations (CFD).The obtained dates were used to check the distribution of the gas phase in the flotation chamber and to assess the energy consumption of the rotor.

PL

Proces mechanicznego mieszania jest powszechną operacją w procesach technologicznych wielu gałęzi przemysłu, również w przetwórstwie minerałów. Oddzielenie cennego minerału od skały płonnej w komorze flotacyjnej powoduje zużycie energii elektrycznej wynoszące 1-10 kW/m3 i w zależności od rodzaju maszyny flotacyjnej. Powietrze jest wprowadzane do komory flotacyjnej, a pęcherzyki są rozpraszane za pomocą układu wirnik-stojan, który jednocześnie miesza zawiesinę z pęcherzykami powietrza. Sprawność flotacji zależy od kształtu zbiornika, konstrukcji wirnika i stojana, a także warunków pracy, takich jak prędkość wirnika, szybkość napowietrzania i właściwości zawiesiny. Dążąc do zmniejszenia zużycia energii przy jednoczesnym zachowaniu wysokiej sprawności procesu, optymalizacja kształtu układu stojan-rotor ma kluczowe znaczenie. Układ ten określa rozkład pęcherzyków w komorze flotacyjnej i występowanie elementarnych aktów flotacji. W artykule przedstawiono wyniki eksperymentów z pomiarów pola prędkości układów woda i woda-powietrze w laboratoryjnej komorze flotacyjnej w różnych warunkach hydrodynamicznych, wykorzystując technikę cyfrowej anemometrii obrazowej (PIV) oraz symulacje numeryczne (CFD). Uzyskane dane posłużyły do sprawdzenia rozkładu fazy gazowej w komorze flotacyjnej oraz do oceny zużycia energii przez wirnik. W artykule przedstawiono wyniki eksperymentów z pomiarów pola prędkości układów woda i woda-powietrze w laboratoryjnej komorze flotacyjnej w różnych warunkach hydrodynamicznych, wykorzystując technikę cyfrowej anemometrii obrazowej (PIV) oraz symulacje numeryczne (CFD). Uzyskane dane posłużyły do sprawdzenia rozkładu fazy gazowej w komorze flotacyjnej oraz do oceny zużycia energii przez wirnik.

7

Optimization of the cooling system in a prototype VCR engine using CFD analysis

Jakubowski Mirosław

Combustion Engines

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2025

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R. 64, nr 3

36--43

EN

The cooling system of an internal combustion engine affects various key parameters, including ignition delay, fuel evaporation, and the compression-expansion process. The geometry of its components impacts both cooling efficiency and the energy demand of the coolant pump. This paper presents CFD simulation results of coolant flow through selected elements of a modified cooling system in a prototype engine. Due to design changes in the power unit, the original coolant outlet manifold required redesign. Three manifold variants were analyzed under two coolant types and two back pressure levels. Flow patterns were evaluated using streamlines and velocity distributions in selected cross-sections. The applied manifold modification significantly increased coolant velocity. In the analyzed cases, the local resistance coefficient rose to values as high as 9. For version mod2, the risk of turbulence was higher with a water-glycol mixture than with water. For version mod1, turbulence sensitivity to coolant type was negligible.

8

Effects of torch flame strength on the combustion process in medium-speed gas engines through pre-chamber orifice specifications

Aoyagi Takahide, Wakasugi Takuya, Tsuru Daisuke, Tashima Hiroshi

Combustion Engines

|

2025

|

R. 64, nr 3

44--57

EN

Gas engines are eagerly introduced for the moment to reduce GHG emissions from the marine sector, and could be used by green methane from the methanation process in the future. Pre-chamber-type gas engines burning lean premixture in a main chamber are the mainstream in the medium-speed engine range. Although the ejection behaviour of torch flames from the pre-chamber has a significant impact on the combustion in the main chamber, there are few research examples of confirming the effects of the pre-chamber specifications by actual observation of the combustion process. In this study, a constant-volume chamber was prepared to reproduce the combustion chamber near the top dead centre of a medium-speed gas engine, to visualize its whole combustion chamber, and to investigate the effects of the pre-chamber specifications. The validity of the CFD simulation based on the RANS turbulence model and the possibility of a design index for the ejection strength of torch flames were also examined.

9

Effect of mesh density and grid type on cavitation cloud volume

Jasionowski Robert, Kostrzewa Waldemar

Zeszyty Naukowe Politechniki Morskiej w Szczecinie

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2024

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nr 80 (152)

23--31

EN

This work is devoted to determining the effect of mesh density and mesh type on cavitation cloud volume generated during the flow of water through the cavitation tunnel. The numerical analysis was carried out on a water model based on a cavitation tunnel located at the Institute of Water Problems of the Bulgarian Academy of Sciences in Sofia, used to test the resistance of construction materials to cavitation erosion. A numerical analysis is performed for four different types of grids: polyhedra, poly-hexcore, hexcore, and tetrahedral. These grids have five different maximum cell sizes: 0.0025, 0.0020, 0.0015, 0.0010, and 0.0005 m. A numerical analysis is performed using commercial CFD software ‒ i.e., Ansys Fluent 2023 R1. The Schnerr and Sauer cavitation model and the k-omega viscous model for shear stress transport (SST) are used. This paper analyzes the qualitative parameters of the quality of the grid, distribution of velocity, pressure, average cell volume, and volume of cavitation cloud consisting of 90% volume vapor fraction. Based on the numerical analyses, it is shown that the basis for obtaining accurate results of the CFD simulations is not only the qualitative parameters of the grid but also its density.

10

Study of predictive control model for cooling process of mark III LNG bunker

Bao Guozhi, Qin Weiguang, Jiang Qingfeng, Pu Chunrong

Polish Maritime Research

|

2024

|

nr 3

102--112

EN

When loading liquefied natural gas (LNG) onto a dual-fuel LNG container ship fuelled by LNG, there is a considerable temperature difference between LNG and the fuel tank at room temperature. The current solution is to pre-cool the tank with LNG through a spray line but the cooling process, if not correctly handled, can result in excessive cooling rates and Boil-Off Gas (BOG), which can expose the tank to increased temperature stress and gas pressure. Therefore, this paper takes the Mark III fuel tank of a specific type of LNG container ship as the object and realises a real-time predictive control system by writing a UDF (User Defined Function) to simulate and analyse the influence of LNG spray rate on the change of cooling effect, cooling time and cooling cost under the unidirectional LNG spray cooling mode. Compared with the results of the fuel tank gas experiment, the deviation of numerical model simulation results is less than 5%. Under the same cooling rate, the real-time control scheme can achieve a more uniform cooling rate and reduce the total LNG consumption by 25%. With the increase in LNG cooling rate, the cooling time, LNG usage, and the total BOG exhaust volume all decrease; however, the decreased range gradually decreases as well. The results of this paper provide parameters and suggestions for optimising and improving the LNG fuel tank cooling monitoring and control system.

11

Exhaust gas heat recovery from a marine engine using a thermal oil system

Le Van Vang, Duong Xuan Quang, Bui Van Hung, Rudzki Krzysztof, Nguyen Van Nhanh, Hai Truong Thanh

Polish Maritime Research

|

2024

|

nr 4

89--99

EN

The recovery of exhaust gas recovery from marine engines is gaining attention in regard to saving fuel and improving system efficiency. Waste heat recovery is particularly beneficial for providing thermal and electric power, and offers efficient solutions to both economic and environmental challenges. The use of waste heat recovery technology offers the opportunity to lower fuel consumption and improve systems, and this approach also falls in line with the stringent emissions guidelines of the International Maritime Organization. This paper describes a unique exhaust gas heat recovery system in which a thermal oil system is used to heat fuel and feed cargo, in order to lower exploitation costs while also addressing environmental issues. CFD simulations of the heat recovery unit with plain and finned helix coils provide important insights into their thermal performance and pressure characteristics. The results indicate that the incorporation of fins could markedly enhance the heat transfer performance. Finned configurations are also found to have higher oil outlet temperatures, reaching up to 145.4°C in the case of a rectangular configuration. In general, this study contributes to the advancement of waste heat recovery technologies in marine applications.

12

Investigation of Tool Cooling and Heat Transfer Using Computational Fluid Dynamics Simulations

Naumann Christian, Schmidt Claus-Dieter, Geist Alexander, Brier Steffen, Glänzel Janine, Klimant Philipp, Ihlenfeldt Steffen, Dix Martin

Journal of Machine Engineering

|

2024

|

Vol. 24, No. 4

5--26

EN

Thermal errors remain one of the biggest challenges for the precision of cutting machine tools. Aside from optimizations in the machine tool design and behaviour, optimal cutting process parameters and targeted usage of cutting fluid or alternative methods of tool cooling are required for improved process efficiency with minimal energy demand and maximal tool life. A simulation-based study is presented which compares both different methods of tool cooling, specifically air cooling, flooded cooling and minimum quantity lubrication and also different simulation methods and models. Using a case study, which models an existing thermal test stand comprised of motor spindle, tool holder, tool and coolant nozzle, different cooling scenarios were tested and compared. The simulations were performed in ANSYS CFX. Comparisons were made between simulations with and without buoyancy, with and without tool rotation, transient and steady-state, with laminar flow and with different turbulence models and between the different cooling scenarios. Some insight on different time step sizes and the resulting increase in simulation time and precision was also gained. These results will make future studies on the thermal behaviour of both tool and cutting process easier by showing suitable simulation techniques and viable model simplifications.

13

Analysis of effects of pre-chamber orifices on torch flame behaviours in lean-burn gas engines

Aoyagi Takahide, Wakasugi Takuya, Tsuru Daisuke, Tashima Hiroshi

Combustion Engines

|

2024

|

R. 63, nr 4

3--14

EN

Fuel conversion from heavy oil to natural gas is favoured as a quick remedy for GHG reduction from industrial engines in ship propulsion and power generation fields thanks to fewer carbon contents in natural gas. In medium-speed gas engines, the ejection of torch flame from a pre-chamber is often used to promote flame propagation within a main combustion chamber. Although orifice specifications affect the ejection behaviour of the torch flame and the following combustion in the main chamber, the effects are difficult to fully understand. Some of the authors developed a constant-volume combustion vessel that simulated the combustion chamber around the top dead centre of a pre-chamber type gas engine and observed the effects of orifice specifications on the torch flame ejection and the combustion in the main chamber. Still, the correlation was not concluded due to the lack of physical examination. In the paper, the above measurement results were confirmed by using RANS-type CFD considering the larger scale of the target engines, and the physical background of the effects of orifice specifications was successfully reproduced.

14

Determination of the heat capacity of a water-ice reservoir as a lower heat source for heat pump - numerical analysis

Tarnawski Piotr

Archives of Thermodynamics

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2024

|

Vol. 45, no. 2

157--163

EN

The paper presents the design of a heat exchanger immersed in a water-ice reservoir and the determination of its heat capacity as a lower heat source for the heat pump. This is an innovative solution, the first project on this scale in Poland. Heat absorption from the water-ice tank took place in three stages: from water at a temperature range of 20˚C to 0˚C, from the water-ice phase change at 0˚C, and from ice at a temperature range of 0˚C to -10˚C. The CFD (Computational Fluid Dynamics) analysis of a heat exchanger performance was performed. It required simulation of water natural convection, water-ice phase change, and heat transfer from the ground. The heat flux absorbed in the designed exchanger was calculated based on the current glycol temperature and the implemented COP (Coefficient of Performance) characteristic of the heat pump. This was done via the user-defined function (UDF) available in Ansys FLUENT. The compiled internal software subroutine was defined based on the DEFINE_ADJUST macro. Moreover, the thermal resistance of ice forming on the pipes was included. The numerical analysis indicated that 66097 kWh of heat would be absorbed from the reservoir in 500 hours of exploitation. The volume fraction of water at the end of the simulation was equal to 26.7% and the volume fraction of ice was equal to 73.3%. The CFD simulation confirmed the heat capacity value of the water-ice storage tank which fulfilled the design requirements.

15

Numerical analysis of the volume of cavitation cloud in a cavitation tunnel using multiphase computational fluid dynamics simulations

Jasionowski Robert, Kostrzewa Waldemar

Zeszyty Naukowe Politechniki Morskiej w Szczecinie

|

2023

|

nr 76 (148)

48--56

EN

This work is devoted to a computational investigation of the position and volume of the cavitation cloud in a cavitation tunnel. The position of the cavitation cloud and its volume in the cavitation tunnel, determined by numerical analysis with respect to the inlet velocity, allows for the determination of the lower or higher intensity of cavitation erosion within the tunnel of the sample material. A numerical analysis is carried out on a model of a typical cavitation tunnel used to investigate the resistance of structural materials to cavitation erosion. The tunnel under study consists of barricade (upper) and counter-barricade (lower) systems. The numerical analysis is carried out with the following five different values of the velocity in the tunnel inlet: 6 m/s, 9 m/s, 12 m/s, 15 m/s, and 18 m/s in the commercial CFD software – Ansys Fluent 2019 R3. The Schnerr and Sauer cavitation model and shear stress transport (SST) viscous model k-omega are used. The paper analyzes the distribution of velocity, pressure, and volume of the cavitation cloud. On the basis of the performed numerical analyses, the optimal velocity at the inlet to the tunnel of 15 m/s is determined, for which the volume of the cavitation cloud is the largest and the phenomenon of cavitation is the most intense. The determination of the position and maximum volume of the cavitation cloud relative to the inlet velocity to the tunnel will, in future, allow us to shorten the resistance tests for cavitation erosion of different materials under real fluid flow conditions.

16

Parametrization of the thermal model of induction motor with outer rotor

Opach Szczepan, Wolnik Tomasz

Przegląd Elektrotechniczny

|

2023

|

R. 99, nr 12

250--257

EN

This paper presents a method of parameterization of the thermal model of an electric motor on the example of an external rotor induction motor with high power density. The simulations presented in this paper were carried out on the motor model with a copper rotor cage with a rated power 25 kW and a mass of 16 kg. This construction, due to the demanding operating conditions they are subjected to, require precise thermal analysis at the design stage. In many works, this analysis is usually limited to thermal simulations without taking into account the rotating elements of the motor. This article presents a method of numerical determination of selected parameters of the CFD model, including the value of the heat transfer coefficient through the air gap, taking into account the rotational motion of the rotor, the convection coefficient, describing the intensity of convective heat exchange of the outer surface of the rotor body with the environment, and an alternative method of numerical determination of substitute values stator winding thermal conductivity coefficients. Based on the results obtained in numerical simulations, a three-dimensional CFD model of the motor was developed and solved.

PL

W publikacji przedstawiono sposób parametryzacji modelu cieplnego silnika elektrycznego na przykładzie silnika indukcyjnego z wirnikiem zewnętrznym o dużej gęstości mocy. Przedstawione w niniejszej pracy symulacje przeprowadzono na modelu sinika z miedzianą klatką wirnika o mocy znamionowej 25 kW i masie 16 kg. Tego rodzaju konstrukcje, ze względu na wymagające warunki eksploatacji, jakim są poddawane, wymagają precyzyjnej analizy termicznej na etapie projektowania. W wielu pracach analiza ta ogranicza się zwykle do symulacji termicznych bez uwzględnienia wirujących elementów maszyny. W niniejszym artykule zaprezentowano metodę numerycznego wyznaczania wybranych parametrów modelu CFD, w tym wartości współczynnika przenikania ciepła przez szczelinę powietrzną z uwzględnieniem ruchu obrotowego wirnika, współczynnika przejmowania ciepła, opisującego intensywność konwekcyjnej wymiany ciepła zewnętrznej powierzchni obudowy wirnika z otoczeniem oraz przedstawiono alternatywną metodę numerycznego wyznaczania wartości zastępczych współczynników przewodzenia ciepła uzwojenia stojana. Na podstawie wyników uzyskanych w symulacjach numerycznych opracowano i rozwiązano trójwymiarowy model CFD silnika.

17

Effects of propeller fouling on the hydrodynamic performance of a marine propeller

Zinati Ali, Ketabdari Mohammad Javad, Zeraatgar Hamid

Polish Maritime Research

|

2023

|

nr 4

61--73

EN

Propeller performance is typically considered under clean conditions, despite the fact that fouling is an inevitable phenomenon for propellers. The main objective of this study is to investigate the effects of roughness due to fouling on the performance of a propeller using a CFD simulation in conjunction with the roughness function model. A simulation of a clean propeller is verified for a five-blade propeller model using existing experimental results. A roughness function model is then suggested based on existing measured roughness data. The simulations are extended for the same propeller under varying severities of roughness. Initially, it is concluded that KT and ηo gradually decrease with increasing fouling roughness, while KQ increases, compared to smooth propeller. For instance, at J=1.2 for medium calcareous fouling, KT is reduced by about 26%, KQ increases by about 7.0%, and ηo decreases by 30.9%. In addition, for the rough propeller, the extra power required is defined as the specific sea margin (SSM) to compensate for the power loss. A slight roughness causes a large decrease in ηo. A propeller painted with foul-release paint and an unpainted propeller are found to require 2.7% SSM and 57.8% SSM over four years of service, respectively. Finally, the use of foul-release paints for propeller painting is strongly advised.

18

CFD simulation of airflow in a new receiver concept for solar tower

Cheilytko Andrii, Nohutcu Oguzhan, Schwarzbözl Peter, Broeske Robin Tim

Journal of New Technologies in Environmental Science

|

2023

|

Vol. 7, nr 3

83--98

EN

Open cavity solar receivers play an important role in concentrated solar power (CSP) systems and hold great promise, particularly in scenarios where their ability to absorb high fluxes at very high temperatures yields beneficial results. This intense concentration of sunlight can be used to produce electricity through various means, such as generating steam to drive a turbine. The efficiency of the open volumetric receiver concept relies heavily on the air return ratio (ARR) which refers to the proportion of air recirculated and returned to the receiver. A high ARR contributes to high receiver efficiencies, as with rising ARR, the reused part of the enthalpy of warm air increases. This paper deals with the design and simulation of a new receiver concept with a conical cavity and square cross-section. The objective is to identify the most effective design arrangement for the square-cone structure, considering different depths, that maximizes both the air return ratio (ARR) and thermal efficiency. The findings demonstrate that increasing the depth of the mentioned receiver leads to a rise in the ARR, up to a certain threshold which can reach values up to 94.53%, beyond which there is a subsequent decline in efficiency. Furthermore, this study examined how varying the amount of air passing through a specific section of the receiver across a defined area, along with the temperature changes in these sections, affected its operational efficiency.

19

The impact of size in fenestration design on the airflow and temperature in natural cross ventilation, case study: A two-bedroom Polish multifamily home

Mohammadi Mohammad Mahdi, Janowski Maciej

Builder

|

2023

|

R.27, nr 10

74--83

EN

In countries with cold winters such as Poland, there is growing evidence for proliferating overheating in summer times due to climate change. Hence, buildings become more uncomfortable for their occupants during hot summers. To tackle this challenge, we use the passive strategies potential to adapt buildings in line with their experimental and engineering analysis of the indoor environment. This paper demonstrates the results of both thermal and airflow simulation of existing naturally ventilated in double-bedroom homes in Poland. Thermal and airflow simulation is used to improve the natural ventilation system and to address summer thermal comfort problems due to excessive hot airflow caused by climate change. In the first step of the research, over 300 multi-family home plans all over Poland were categorized by size, ventilation type, facade organization, and fenestration type. In the second part, computational fluid dynamics (CFD) analysis is used on 3D models to predict indoor airflow velocities for different levels of the building envelope airflow permeability. Then, a coupled thermal and airflow simulation with 2 different window size, fully open, and with 3 integrated shadings options (base model or no shadings, 30 cm overhang with side-fin, and 10 cm depth horizontal louvers) are done to investigate whether the more opened envelope reduces a summer overheating problem. The results for the optimized natural ventilation through fenestrations successfully address houses' summer discomfort problem by reducing the indoor temperature between 2-3ºC and in some cases up to 4ºC cooler than similar model with small windows.

PL

Z powodu zmian klimatu w krajach o mroźnych zimach, takich jak Polska, pojawia się coraz więcej dowodów na coraz częstsze przegrzewanie się pomieszczeń w okresie letnim. Dlatego budynki stają się bardziej niewygodne dla ich mieszkańców podczas upalnego lata. Aby sprostać temu wyzwaniu, wykorzystano potencjał strategii pasywnych do adaptacji budynków zgodnie z ich eksperymentalną i inżynierską analizą środowiska wewnętrznego. W artykule przedstawiono wyniki symulacji termicznej i przepływu powietrza w istniejących polskich mieszkaniach dwupokojowych z naturalną wentylacją. Symulacja termiczna i przepływu powietrza służy do poprawy systemu naturalnej wentylacji i rozwiązania problemów związanych z komfortem cieplnym w lecie, spowodowanych nadmiernym przepływem gorącego powietrza związanym ze zmianami klimatycznymi. Na pierwszym etapie badań ponad 300 projektów domów wielorodzinnych z całej Polski zostało skategoryzowanych pod względem wielkości, rodzaju wentylacji, organizacji elewacji i rodzaju okien. W drugiej części analiza obliczeniowej dynamiki płynów (CFD) była wykorzystywana na modelach 3D do przewidywania prędkości przepływu powietrza w pomieszczeniach dla różnych poziomów przepuszczalności powietrza przez powłoki zewnętrzne budynku. Następnie przeprowadzano połączoną symulację termiczną i przepływu powietrza z dwoma różnymi rozmiarami okien, całkowicie otwartymi, i trzema zintegrowanymi opcjami zacienienia, aby zbadać, czy bardziej otwarta powłoka budynku zmniejsza problem przegrzania mieszkania w okresie letnim. Wyniki pokazują, że zoptymalizowana naturalna wentylacja przez okna skutecznie rozwiązuje problem dyskomfortu w domach latem, obniżając temperaturę wewnętrzną o 2-3°C, a w niektórych przypadkach nawet o 4°C w porównaniu do podobnych modeli ze standardowymi oknami.

20

Przepływ powietrza w przestrzeni klatki schodowej w zależności od temperatury powietrza zewnętrznego

Bogusławska Arleta, Brzezińska Dorota

Materiały Budowlane

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2022

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nr 12

17--21

PL

W artykule przedstawiono wyniki eksperymentu w skali rzeczywistej dotyczącego przepływu powietrza wywołanego siłą ciągu naturalnego w przestrzeni klatki schodowej budynku średniowysokiego, zlokalizowanego na terenie Politechniki Łódzkiej. Badania były realizowane przez 6 miesięcy, co wynika z braku informacji literaturowych o zachowaniu się systemu w tak długim przedziale czasu. Uzyskane wyniki pozwalają stwierdzić, że przez ok. 80% czasu w ciągu roku system oddymiania grawitacyjnego działa z odpowiednią wydajnością. Wyniki pomiarów zostały zweryfikowane z wykorzystaniem symulacji CFD.

EN

Article presents the results of a real-scale experiment for natural air flow in staircase space in medium-high building located on Lodz University of Technology Campus. The experiments were performed for six months. In literature data there is a lack of information about temporary air flow in such a long period time. On the basis of research results it has been found that natural smoke exhoust system works with sufficient capacity for almost 80% time in year. The experimental results were verified using CFD simulation.