University of TehranEnergy Equipment and Systems2383-11118320200901Investigation of convective heat transfer, pressure drop and efficiency of ZnO/water nanofluid in alternating elliptical axis tubes2032154463410.22059/ees.2020.44634ENAhmadreza SajadiFaculty of Engineering, Shahrekord University, Shahrekord, IranSasan TalebiFaculty of Engineering, Shahrekord University, Shahrekord, IranJournal Article20200504In this study, for the first time, the heat transfer and the pressure drop of zinc oxide nanoparticles in alternating elliptical axis (AEA) tube have been investigated experimentally. The zinc oxide nanoparticles were at volumetric concentrations 1% and 2%. The base fluid was heat transfer oil and the experiments were conducted at constant wall temperature. Also, the study was done in Reynolds number range of 400- 1900. The experimental results show that the heat transfer, pressure drop and, the efficiency of AEA tubes are higher than the circular tube. The heat transfer rate and pressure drop increase by flattening the tube and adding nanoparticles. To compare the heat transfer and pressure drop simultaneously, an efficiency parameter is defined. This parameter shows how much increase in heat transfer can be obtained for the pressure drop of a circular tube with the same hydraulic diameter as the AEA tube. Using AEA tube with nanoparticles increases heat transfers by up to threefold, and pressure drop by up to twofold, resulting in an overall twofold increase in the efficiency.University of TehranEnergy Equipment and Systems2383-11118320200901Cost and performance analysis of an integrated solar combined cycle with two tanks for indirect thermal energy storage2172354464210.22059/ees.2020.44642ENBagher ShahbaziFaculty of Mechanical Engineering, University of Tabriz, Tabriz, IranFaramarz TalatiFaculty of Mechanical Engineering, University of Tabriz, Tabriz, IranMohammad SeyyedmahmoodiFaculty of Mechanical Engineering, University of Tabriz, Tabriz, IranMortaza YariFaculty of Mechanical Engineering, University of Tabriz, Tabriz, IranJournal Article20190607In this paper, the annual and economic performance of an integrated solar combined cycle (ISCC) with indirect energy storage tanks is investigated. The study includes four scenarios, in which the combined cycle performance was studied exclusively in the first scenario. In the second scenario, the integrated solar combined cycle (ISCC) was examined, and the use of supplementary firing instead of solar energy with the assumption of producing the same power as that by the ISCC scenario was examined for the third scenario. For the fourth scenario, the use of energy storage in the form of indirect tanks with the purpose of energy storage during peak solar direct normal irradiation times and discharge during peak power electricity consumption within the network for such power plants were subjected to investigation. Results show that the contribution of solar energy in the annual produced power by the ISCC scenario is 40 GWh, which is 2.2% of the total. In the case that this amount of power is produced using supplementary firing, there will be about 1.98 tons of increased fuel consumption, and about 18 kton increased in CO<sub>2</sub> production. By using the energy storage system, the annual power generation increases by 5 GWh, which will raise the plant's annual revenue by 0.25 M$ if the increment occurs during peak hours. Moreover, the levelized costs of energy (LCOE) for the four scenarios are 8.99, 8.86, 9.04, and 9.135 cents/kWh, respectively.University of TehranEnergy Equipment and Systems2383-11118320200901A numerical study of the effect of channel spacers on the performance of cross-flow forward osmosis membrane modules2372514465710.22059/ees.2020.44657ENAlireza JalaliSchool of Mechanical Engineering, College of Engineering, University of Tehran, North Kargar Avenue, Tehran,1439957131, IranNaeem NiknafsSchool of Mechanical Engineering, College of Engineering, University of Tehran, North Kargar Avenue, Tehran,1439957131, IranJournal Article20200810In this paper, we perform two-dimensional simulations of cross-flow forward osmosis (FO) membrane modules in the presence of draw and feed channel spacers. For this purpose, the equations corresponding to the conservation of mass, momentum, and convection-diffusion for the mass fraction of solute are solved using a commercial finite volume flow solver. We consider six configurations of channel spacers being constructed by the symmetric and asymmetric placement of cavity, submerged, and zigzag arrangements. We will study the effect of the spacers’ geometrical parameters such as diameter and relative distance in these configurations as well as the solute resistivity of the porous support layer on the performance of the FO membrane modules in terms of water flux, external concentration polarization (ECP) factors, and pressure drop per unit length of the membrane. Our results reveal that increasing the solute resistivity of the porous support layer has an adverse effect on the water flux, whereas the impact on the ECP factors is positive. In addition, it turns out that the submerged configurations, where the spacer filaments are not in direct contact with the membrane surface, produce the highest water flux through the membrane; however, they have an adverse effect on the pressure drop along the membrane surface.University of TehranEnergy Equipment and Systems2383-11118320200901Determination of significant sources generating low-frequency noise in horizontal axis wind turbines2532624465810.22059/ees.2020.44658ENAlireza BozorgiDepartment of Mechanical Engineering, Arak University of Technology, Arak, IranGhader GhorbaniaslVrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, BelgiumJournal Article20200813Several studies show that the Low-Frequency Noise (LFN) of wind turbines could have harmful effects on human health even when it is infrasound. In traditional classifications, the LFN of upwind turbines is referred only to steady thickness and steady loading sources, and the effect of vortices is considered negligible. In this study, the LFN of a horizontal axis wind turbine is simulated in wind speeds of 5-25 m/s by using a hybrid approach. The results show that vortices being far from blades have a significant effect on the LFN. It is also observed that the position received maximum LFN is far from the point introduced by the IEC 61400-11 standard for measuring the noise of horizontal axis wind turbines.University of TehranEnergy Equipment and Systems2383-11118320200901Economic assessment of solar-based hydrogen for methanol production2632734475310.22059/ees.2020.44753ENNima Bahrami ZiabariSustainable Energy Research Group (SERG), School of Mechanical Engineering, Iran University of Science and Technology, Tehran, IranSamane GhandehariunSustainable Energy Research Group (SERG), School of Mechanical Engineering, Iran University of Science and Technology, Tehran, IranJournal Article20191231The climate change crisis has urged societies to take action for mitigating greenhouse gas emissions. Carbon neutral fuel is one of the proposed solutions to achieve this goal. Carbon neutral fuel is the product of captured CO<sub>2</sub> with different methods such as direct air capture, sea water-absorbent, and power plant chimneys, and reformed through reactions with hydrogen under high temperatures and pressures. Methane, Methanol, E-diesel and Dimethyl Ether are some fuels that can be made through these processes. With this renewable fossil fuel, there will be no need for building new infrastructures, and it saves tons of money and mitigates greenhouse gas emissions resulting in higher GDP and life quality in the long term. Since there must be no added CO<sub>2</sub> emissions within the whole process of carbon-neutral fuel production, to fulfill carbon neutrality, the hydrogen component should be produced from renewable energy sources like solar, wind or geothermal. This paper presents an economic assessment of the solar-based hydrogen for green methanol production. The results show that the levelized cost of solar-based hydrogen is dramatically higher than fossil-based hydrogen due to lack of investments in the renewable energy section in Iran. With a solar-based hydrogen price of $28.1/kg, green methanol price is evaluated $19159/mt.University of TehranEnergy Equipment and Systems2383-11118320200901The use of waste heat recovery (WHR) options to produce electricity, heating, cooling, and freshwater for residential buildings2772964494910.22059/ees.2020.44949ENEhsan GholamianSchool of Mechanical Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran, IranPouria AhmadiSchool of Mechanical Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran, IranPedram HanafizadehSchool of Mechanical Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran, IranLivio MazzarellaDepartment of Energy, Polytechnic University of Milan, Milan, ItalyJournal Article20200202<em>In recent years, there is a growing attention drawn to the area of building-integrated CCHP systems, due to its high capability in cost and energy saving. In this study, a residential scale multigenerational system is proposed to generate power by using solid oxide fuel cell and gas turbine (hybrid SOFC/GT), heating (by using HRSG), cooling (by using a double-effect absorption chiller) and freshwater (by using a Revers osmose plant). The system is modeled in engineering equation solver and studied from energy, exergy, economic and environmental standpoints. A parametric study is conducted in order to define the crucial decision variables in the system, and their effect on the overall exergy efficiency and unit product cost, along with the rate of freshwater production is observed. Results of the parametric study demonstrated that fuel utilization factor, stack temperature difference, current density, and the pressure ratio of air compressor have the most substantial influence on the behavior of the proposed system. Moreover, obtained results revealed that the energy and exergy efficiency of the system reaches 86.32% and 69.06%, respectively. In addition, the rate of freshwater production and unit product cost of the entire system becomes 256 L/day and 37.78 $/GJ.hr. Furthermore, the emission of the proposed system becomes 0.225 ton/MW.hr, which faces a 31% reduction compared to the standalone power generation system.</em>University of TehranEnergy Equipment and Systems2383-11118320200901Simulation of an airfoil with a deformable flap applicable in wind turbine structural load reduction2973064568110.22059/ees.2020.45681ENMajid EbrahimiSchool of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, IranFarzad A. ShiraziSchool of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, IranKobra GharaliSchool of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, IranJournal Article20190610<em>Flow over an airfoil equipped with Deformable Trailing Edge Flap (DTEF) has been numerically</em> <em>studied in a two-dimensional steady-state condition with various angles of attack. The airfoil is NACA 64-418, and the flap angle is defined by changing camber</em>-<em>line geometry at 10% chord length from the trailing edge. It has been shown that the direction of the flap deflection has significant impacts on aerodynamic behaviors, which provides an extra means to adjust wind turbine structural loads. Simulations have been conducted with aerodynamic-aeroelastic FAST code in the form of an open-loop control scheme to determine the DTEF's performance in a wind turbine. The wind turbine behavior has been plotted and compared for various flap angles. The load-variation ranges of the wind turbine have been identified, which help determine their sensitivity to flap changes. Finally, an open-loop control circuit is aimed at reducing the amplitude of oscillations of the blade root flapwise bending moment.</em>