2022 Cilt 27 Sayı 2

Permanent URI for this collectionhttps://hdl.handle.net/11452/30949

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Design and thermodynamic performance analysis of an ammonia-water absorption refrigeration and microturbine combined system
(Bursa Uludağ Üniversitesi, 2022-08-02) Altun, Ayşe Fidan; Orhangazi Yeniköy Asıl Çelik Meslek Yüksekokulu; 0000-0001-7236-8398
Integrating absorption chillers in cogeneration and trigeneration systems are beneficial for increasing energy efficiency and sustainability. Those systems have higher efficiency, lower emissions, and lower costs compared to conventional systems. Therefore, it is crucial to develop thermodynamic models to predict the energy behaviour of the system for efficient design. System design and extensive thermodynamic analysis were conducted for a microturbine-NH3/H2O absorption cold and power system. The microturbine with a 60 kW power capacity is the prime mover.14 kW absorption chiller is fed by exhaust gases coming from the waste heat recovery part of the microturbine. The thermodynamic properties of the fluid at various state points were determined. The first and second law efficiency of the system was presented for different design parameters such as evaporation, condensation, generation temperature of the absorption system, effectiveness of the condenser-evaporator heat exchanger, and the solution heat exchanger. The proposed system's energy utilization factor is 28.3%, representing a 43.5% efficiency increase relative to the sole microturbine cycle. In addition, if waste heat from the flue gases discharged from the turbine is not recovered, a tremendous amount of energy may be lost. Therefore, the application of combined energy systems is a vital solution for energy efficiency.
Evaluation of mechanical properties of intraply hybrid carbon/aramid composite materials
(Bursa Uludağ Üniversitesi, 2022-04-20) Karaçor, Berkay; Özcanlı, Mustafa
Hybridization is an important application in obtaining the multi-functionality to combine the best properties of each reinforcing element makes up the composite. In this study, hybrid composites and uniform composites were fabricated using carbon, aramid, and intraply carbon/aramid hybrid weaves with two different production methods (vacuum-assisted resin transfer molding process and vacuum bagging process). The mechanical properties of the produced hybrid composites and uniform composites were analyzed with respect to two different methods. Epoxy resin from thermoset resins was used as a matrix element. The composite samples produced were analyzed mechanically (tensile test, hardness test) and morphologically, as well as in the production of intraply hybrid carbon/aramid composites and interply hybrid Carbon and Kevlar composites, how different production methods affect the results. Results show in the productions made with VABM (vacuum bagging method), the tensile strength value of Intraply carbon/aramid hybrid samples was 1.56 times better than the ones made with VARTM (vacuum assisted resin transfer molding). In the comparison of hardness values, 1.20 times higher results were obtained in the value of Intraply carbon/aramid hybrid samples produced with VARTM compared to those made with VABM. Using SEM analysis, the interfacial properties such as fiber breakage, fiber shrinkage, and fracture were determined in the specimens after the uniaxial tensile test, and it was found that the interactions of the fiber interfaces support the mechanical properties of the specimens.
Numerical heat flux analysis of a trombe wall system in Turkey
(Bursa Uludağ Üniversitesi, 2022-04-23) Kaya, Ercan Şerif
Trombe wall is an inexpensive passive heating design method used for storing and utilizing solar energy to increase indoor temperature without relying on any mechanical system that requires additional energy. Most recent studies concerning solar wall configuration and energy efficiency have been conducted by using computational fluid dynamics. One reason for this is because semi-transparent and opaque boundaries are provided in simulating wall and glazing surfaces around the fluid domain and solar heat flux energy are allowed in through semi-transparent boundaries. However, finite element method programs employ solid and shell elements as opaque walls that transmit the energy into the domain. In this study, numerical heat flux analysis of a Trombe wall system, which was built for a previous experimental study, has been performed and numerical and experimental analysis results have been verified. According to the simulation studies, heat transfer analysis results are obtained in a good agreement with real time measurements when additional solar load calculated due to transmissivity are defined at the surfaces which are expected to be sun exposed. Besides, numerically verified model of the Trombe wall system was used in evaluating energy saving potential of residential buildings for three cities with different climate regions in Turkey.
Numerical investigation of X-45A type unmanned combat air vehicle
(Bursa Uludağ Üniversitesi, 2022-08-22) Soğukpınar, Hacı; Cağ, Serkan
In this paper, the low-speed aerodynamic performance of unmanned combat air vehicle (UCAV) X-45 delta wing was investigated by a numerical method using computational fluid dynamic approaches (CFD). The investigation was conducted with X-45 and the formation of leading-edge vortices (LEV) and vortex breakdown was studied by a varying angle of attack with the range of 5° to 30° at the Reynolds number of 10,000 using the SST turbulence model and are compared with experimental data to validate simulation accuracy of CFD. Stall conditions happened at around 30°, averaged vorticity layer demonstrates a prolonged form that goes along by narrow recirculation zones neighboring to the wing surface. Detail about flow field, including LEV formation, vortex breakdown, interaction, and nonlinear aerodynamic characteristics of X-45 was presented and discussed.
PID tuning with up-to-date metaheuristic algorithms
(Bursa Uludağ Üniversitesi, 2022-05-23) Vatansever, Fahri; Hacıiskenderoğlu, Emre; Mühendislik Fakültesi; Elektrik Elektronik Mühendisliği; 0000-0002-3885-8622; 0000-0001-5724-1153
Control of systems is very important in applications. For this purpose appropriate controllers need to be designed. PIDs are the most popular controllers and there are traditional methods for their design. In recent years, metaheuristic algorithms also have been used to tuning the PID coefficients. In this study, an interactive graphical user interface program was designed, which makes the design of PID type controllers with six up-to-date metaheuristic algorithms according to different performance criteria. The controller coefficients can be tuned easily, quickly and effectively with this software tool that performs single or comparative designs, provides numerical and graphical solutions, and enables detailed analysis and synthesis.
Stability analysis of stone column slopes under different earthquake loads
(Bursa Uludağ Üniversitesi, 2022-08-07) Vekli, Mustafa; Çadır, Cenk Cuma
How a slope behaves under the action of a dynamic load such as an earthquake is of great importance in stability analyses of slopes. Improving the region where slope failure occurs or preventing potential slope failure can lead to reducing the factors that excite movement in a slope and/or increasing the sliding resistance of the soils. In this study, the stone column method was used as an improvement technique. In the analysis performed with Plaxis 2D, safety factors were defined for slopes with different slope angles, soil cohesion, and three different earthquake magnitudes. Later, the slopes with the same characteristics were improved using the stone column method. The slopes were improved with different s/D ratios and different internal friction angles of the stone column. The same earthquake forces were also applied to the improved slopes and the factors of safety were determined. In the study, slope models with stone columns designed without the effect of earthquake force showed an increase in safety values in the range of 1.01to 1.34 times compared to slope models without stone columns. It was found that the safety values of the slope models with stone columns increased by 1.02- 1.80 times compared to the slope models without stone columns under the effect of earthquake force.
Static analyses of the effect of deep excavation on the behaviour of an adjacent pile in sand
(Bursa Uludağ Üniversitesi, 2022-07-21) Ashour, Sameh; Ünsever, Yeşim S.; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0003-0590-0203; 0000-0003-3735-9554
The influence of deep excavation on adjacent pile behaviour is an important issue to ensure its serviceability and stability. In this paper, the effect of deep excavation on an adjacent loaded single pile in saturated cohesionless soil was investigated by 3D finite element method. After verification of finite element model using centrifuge test results found in literature, a parametric study was conducted by varying the most influence factors on the pile behaviour such as excavation depth, distance from the pile to the excavation and pile head type. It was concluded that the excavation depth (He) with respect to pile length (Lp) has a significant effect on pile response. Among the three cases of He/Lp, the case of He/Lp= 0.5 induced the maximum bending moment while the case of He/Lp= 1.5 induced the maximum pile lateral deflection. Moreover, the distance from the pile to the excavation site has also a significant influence on pile response and the induced bending moment in pile is inconsiderable after 9 m distance. Also, it is observed that the pile head type has an important effect on the pile behaviour especially in case of rigid head case.

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