NUMERICAL AND EXPERIMENTAL ANALYSIS OF THE STRENGTH OF TANKS DEDICATED TO HOT UTILITY WATER

The focus of this paper are experimental and numerical strength tests of domestic hot water storage tanks. The tests involved the verification of the minimum wall thickness for the assumed operating parameters while meeting all safety standards. The authors presented numerical and experimental analyses for the verification of strength parameters of axial cylindrical tanks due to the lack of methodological guidelines for this type of equipment. In order to verify the conducted theoretical considerations and calculations, experimental tests of samples of front welds produced with austenitic steel as well as a pressure test for the whole tank were conducted using a research test stand

NUMERICAL AND EXPERIMENTAL ANALYSIS OF THE STRENGTH OF TANKS DEDICATED TO HOT UTILITY WATER

The focus of this paper are experimental and numerical strength tests of domestic hot water storage tanks. The tests involved the verification of the minimum wall thickness for the assumed operating parameters while meeting all safety standards. The authors presented numerical and experimental analyses for the verification of strength parameters of axial cylindrical tanks due to the lack of methodological guidelines for this type of equipment. In order to verify the conducted theoretical considerations and calculations, experimental tests of samples of front welds produced with austenitic steel as well as a pressure test for the whole tank were conducted using a research test stand

HIGH SPEED MILLING IN THIN-WALLED AIRCRAFT STRUCTURES

Aircraft structures are designed to mainly consist of integral elements which have been produced by welding or riveting of component parts in technologies utilized earlier in the production process. Parts such as ribs, longitudinals, girders, frames, coverages of fuselage and wings can all be categorized as integral elements. These parts are assembled into larger assemblies after milling. The main aim of the utilized treatments, besides ensuring the functional criterion, is obtaining the best ratio of strength to con-struction weight. Using high milling speeds enables economical manu-facturing of integral components by reducing machining time, but it also improves the quality of the machined surface. It is caused by the fact that cutting forces are significantly lower for high cutting speeds than for standard machining techniques

Numerical simulations of temperature and velocity fields in the storage tank with the three-coil heat exchanger

This article presents the results of the numerical investigation of the thermal stratification in the hot water storage tank. The exchanger consists of three tube coils that are immersed in the storage tank of hot water. Two coils—lower and upper—are designed to warm the water in the tank using the water as a heating medium. Another coil—uses the refrigerant for the waste heat transfer. The temperature stratification device is mounted in the thermal storage tank. The device’s task is to improve the thermal stratification level of heated water. The performed numerical simulations allowed us to obtain the temperature and velocity fields in the storage tank under the conditions of the work of coils filled with water. Calculations were made in the case of the use of the stratification device under the operating conditions of the 10.2478/amst-2019-0015upper and lower coils with water

Using hsm technology in machining of thin-walled aircraft structures

Subtracting manufacturing technologies have entered that realm of production possibilities which, even a few years ago, could not be directly adapted to direct production conditions. The current machines, i.e. heavy, rigid cutting machines using high spindle speed and high feed speed, allow for manufacturing very thin and relatively long parts for use in the automotive or aerospace industry. In addition, the introduction and implementation of new 70XX aluminium alloys with high strength parameters, as well as monolithic diamond cutting tools for special machining, have had a significant impact on the introduction of high-speed machining (HSM) technologies. The main ad-vantage of the applied manufacturing method is obtaining a very good smoothness and surface roughness, reaching even Sz = 6–10 μm and Sa <3 μm, and about four times faster and more efficient machining compared to conventional machining (for the beam part). Moreover, fixed and repeatable milling process of the HSM method, reduction of operational control, easy assembly of components and increase in the finishing efficiency compared to other methods of plastic processing (forming) are other benefits. The authors present a method using HSM for the manufacturing of aircraft parts, such as the chassis beam at the front of a commuter aircraft. The chassis beam assembly is made of two parts, front and rear, which – through a bolted connection – form a complete element replacing the previous part made using traditional technology, i.e., cavity machining, bending and plastic forming. The implementation of HSM technology eliminates many operations related to the construction of components, assembling the components (riveting) and additional controls during construc-tion and assembly

Thermal performance of the thermal storage energy with phase change material

Values of energy supply and demand vary within the same timeframe and are not equal. Consequently, to minimise the amount of energy wasted, there is a need to use various types of energy storing systems. Recently, one can observe a trend in which phase change materials (PCM) have gained popularity as materials that can store an excess of heat energy. In this research, the authors ana-lysed paraffin wax (cheese wax)’s capability as a PCM energy storing material for a low temperature energy-storage device. Due to the relatively low thermal conductivity of wax, the authors also analysed open-cell ceramic Al2O3/SiC composite foams’ (in which the PCM was dispersed) influence on heat exchange process. Thermal analysis on paraffin wax was performed, determining its specific heat in liquid and solid state, latent heat (LH) of melting, melting temperature and thermal conductivity. Thermal tests were also performed on thermal energy container (with built-in PCM and ceramic foams) for transient heat transfer. Heat transfer coefficient and value of accumulated energy amount were determined

Zastosowanie cienkościennych konstrukcji integralnych w lotnictwie na przykładzie projektu SAT-AM

Konstrukcje samolotów są poddawane w trakcie lotu działaniu różnych składowych stanu obciążenia. Każde zadanie w czasie lotu składa się z szeregu manewrów, które generują różne obciążenia samolotu, zarówno pod względem wartości, jak i kierunku ich działania. Wysoki poziom trwałości i niezawodności jest podstawowym, ścisłym wymogiem dla współczesnych konstrukcji lotniczych. Oznacza to, że podczas projektowania statku powietrznego należy wziąć pod uwagę wiele nierzadko sprzecznych ze sobą ograniczeń. Najważniejszym z nich jest masa konstrukcji, która ma decydujący wpływ zarówno na właściwości lotne i techniczne, jak i na ekonomikę eksploatacji. To sprawia, że samolot jest jednym z najbardziej złożonych produktów technicznych. Nowoczesne konstrukcje samolotów, a ściślej ich elementy nośne, są prawie wyłącznie wykonane jako cienkościenne, które spełniają postulat zminimalizowania masy konstrukcji. Szeroko rozpowszechnione są systemy, w których pokrycie jest wzmocnione elementami wzdłużnymi i poprzecznymi, zapewniając wymaganą sztywność i wytrzymałość całości systemu. Podczas gdy miejscowa utrata stateczności pokrycia jest dopuszczalna w warunkach obciążenia roboczego, przekroczenie poziomów obciążenia krytycznego elementów szkieletu konstrukcyjnego (ramy, podłużnice, wręgi) jest praktycznie równoznaczne ze zniszczeniem konstrukcji. Wskazane czynniki wymuszają ciągłe doskonalenie zarówno metod projektowania, jak i rozwiązań konstrukcyjnych w lotnictwie. Rozwój inżynierii materiałowej i ciągłe doskonalenie procesów technologicznych nie pozostają bez znaczenia dla skuteczności tych pomysłów. Dyscypliny te pozwalają konstruować geometrycznie złożone integralne struktury, które stwarzają możliwość nie tylko bardziej racjonalnego wykorzystania właściwości materiału, ale także, poprzez ich odpowiednie ukształtowanie, znacznie zwiększają dopuszczalne obciążenia konstrukcji nośnej. Główną zaletą przy projektowaniu części integralnych jest oszczędność ekonomiczna, uzyskana w wyniku wyeliminowania lub ograniczenia operacji montażowych. Gęsto żebrowane elementy pokrycia wykonane w tej technologii należą do elementów konstrukcji nośnej, które zmniejszają masę i podnoszą parametry wytrzymałościowe konstrukcji nośnej. Zmniejszając grubość pokrycia i jednocześnie wprowadzając gęsto usztywniające elementy podłużne, można uzyskać konstrukcję o znacznie wyższych obciążeniach krytycznych, a w konsekwencji bardziej korzystny rozkład gradientów i poziomów naprężeń, co bezpośrednio przyczynia się do zwiększenia trwałości zmęczeniowej. W artykule podjęto próbę oceny wprowadzenia nowych technologii wykonania konstrukcji płatowców dla podniesienia ich walorów wytrzymałościowych, aerodynamicznych oraz masowych

Experimental and Numerical Characterization of Thermal Bridges in Windows

Actions aimed at improving the energy performance of buildings increase the share of heat loss through thermal bridges and windows in a building’s energy balance. This is especially true of buildings currently under construc- tion. In addition, it is known that the correct installation of windows is one of the biggest obstacles that must be overcome in order to achieve higher energy efficiency and reduce the impact of linear thermal bridges. Therefore, the study analysed, numerically and experimentally, the energy properties of PVC window frames with improved metal stiffening profiles, which were introduced to reduce the risk of window frame deformation and reduce leakage caused by faulty installation. The value of the frame thermal transmittance coefficient and the linear heat transfer coefficients were determined numerically. The simulation results showed that filling large air spaces with insulation material allowed for the reduction of the Uf frame’s thermal transmittance coefficient by over 10%. Moreover, where the window connects with the wall, there was a reduction in the linear thermal bridges’ influence on heat losses. The reduction in the linear thermal transmittance coefficient Ψ was 9.6%, 1.0%, and 3.5% for the window sill, jamb, and lintel, respectively, compared to a frame without insulation. Moreover, experimental studies were conducted on the influence of the insulation of the PVC window frame with metal closed stiffening profiles on the linear thermal bridge located at the joint with the glass. It was found that the incidence factor Itb decreased by more than 6%. Thus, there is also a positive effect on the linear thermal bridge at the joint of the glass pane with the window frame

Analytical and numerical analysis of injection pump (stepped) shaft vibrations using Timoshenko theory

The free transverse vibrations of shafts with complex geometry are studied using analytical methods and numerical simulations. A methodology is proposed for evaluating the results of a natural transverse vibration analysis as generated by finite element (FE) models of a shaft with compound geometry. The effectiveness of the suggested approach is tested using an arbitrarily chosen model of the injection pump shaft. The required analytical models of the transverse vibrations of stepped shafts are derived based on the Timoshenko thick beam theory. The separation of variables method is used to find the needed solutions to the free vibrations. The eigenvalue problem is formulated and solved by using the FE representation for the shaft and for each shaft-simplified model. The results for these models are discussed and compared. Additionally, the usefulness of the Myklestad–Prohl (MP) method in the field of preliminary analysis of transverse vibration of complex shaft systems is indicated. It is important to note that the solutions proposed in this paper could be useful for engineers dealing with the dynamics of various types of machine shafts with low values of operating speeds