Energy Equipment and Systems
Volume:3 Issue: 1, Winter 2015

Heat recuperation is often used to improve the overall cycle efficiency of gas turbines. However, generally in small- scale gas turbines, it has a negative effect on turbine inlet temperature, pressure ratio and pressure drops, and thus decreases the overall cycle efficiency. In this paper, a thermodynamic model is performed to evaluate recovered heat as a function of heat exchanger effectiveness, pressure drops, and defines the overall cycle energy and exergy efficiency. A high heat exchanger effectiveness, and low pressure drops are favorable to achieve maximal cycle energy efficiency. The main challenge in recuperator designis to find compromise between these conflicting requirements. Hence, a thermodynamic model is developed to determine recuperator design with an aim to maximize overall cycle energy and exergy efficiency. Further, to analyze Iran's manufacturing and its technological capabilities,a pre-requisite is considered for the proposed model. Hence, Iran's capability level could be determined. Finally, a case study of selecting recuperator of a 200kW gas turbine is conducted. Industrial gas turbines show performance characteristics that distinctly depend on ambient and operating conditions. They are influenced by site elevation, ambient temperature, and relative humidity. Proper application of gas turbines requires consideration of these factors. Thus, in this study, the effect of ambient conditions on overall cycle energy and exergy efficiency is performed by the proposed thermodynamic model.

The shape of wake behind a wind turbine is normally assumed to have a hat shape for the models used in wind farm layout optimization purposes; however, it is know from experimental tests and numerical simulations that this is not a real assumption. In reality, the results of actual measurements and detailed numerical simulation show that the velocity in wake region has a S-shape profile. The present study calculated a semi-analytical profile for the shape of the wake behind a wind turbine using blade element momentum method. It is shown that the wake shape differs in different operational conditions and geometrical characteristics of the wind turbine.

In the present study, the effect of porosity on the cathode microstructure (50:50 wt. % LSM: YSZ) of a Solid Oxide Fuel Cell (SOFC) has been examined. A 3-D finite element method for Mixed Ionic and Electronic Conducting Cathodes (MIEC) is presented to study the effects of porosity on cell performance. Each microstructure was realized using the Monte Carlo approach with the isotropic type of growth rate. The effect of porosity on the cathode of a solid oxide fuel cell involving the Three Phase Boundary Length (TPBL), electric conductivity of LSM phase, ionic conductivity of YSZ, mechanical behavior and tortuosity of the pore phase were explored in the present work. The cathode having a porosity value between 31 and 34% revealed the maximum TPBL value as well as a high variation in the electrical conductivity of the LSM phase. Pore phase tortuosity was also decreased by increasing the porosity factor.

The performance of the electric submersible pump (ESP) significantly affected by Gas Void Fraction (GVF). Thus, using of a Rotary Gas Separator (RGS) is a suitable solution for this issue. The performance of the RGS is function of different parameters such as geometry of impeller, rotating speed, boundary conditions, media viscosity and GVF. In this study, the influences of GVF, viscosity, and flow rate on vortex and paddle wheel gas separator have been studied. For this purpose, commercial CFD software has been implemented. As results show, paddle wheel geometry is more efficient in comparison to the vortex gas separator in same conditions. Nevertheless, low efficient region occurs in high flow rates. In other words in flow rates higher than 1000 bpd efficiency of separator is lower than 50% which means that only the natural separation occurs in RGS equipment. Paddle wheel separator is more sensitive to GVF increase in high viscosities and the dropdown of efficiency in viscosity of 10 cp is about 20 in percent. The opposite happens with vortex gas separator in which the separation efficiency is more sensitive to increase of GVF of liquid stream in lower viscosities.

This study investigated the performance and aeroelastic characteristics of a wind turbine blade based on strongly coupled approach (two-way fluid structure interaction) to simulate the transient FSI1 responses of HAWT2. Aerodynamic response was obtained by 3D CFD-URANS approach and structural response was obtained by 3D Finite element method. Aeroelastic responses of the blade were obtained by coupling those aerodynamic and structural models. The analysis model was validated using the experimental result of performance of NREL phase VI rotor which was conducted by NASA/AMES wind tunnel. Numerical results consist of torque and pressure coefficient in different sections of span (over wind speed of 7 to 15 m/s) which were compared with available experimental results. The present model was also evaluated with results of other aeroelastic simulations.

Electric motors are the largest consumer of world electric energy, consuming more than twice as much as lighting, the next largest consumer. Electric motors account for between 43 and 46% of all global electricity consumption approximately. They give rise to about 6 040 Mt of CO2 emissions. End‐users approximately spend USD 565 billion per year on electricity [1]. In recent years, increase in energy price has led to development of highly efficient motor technologies and their applications. Despite the fact that the application of brushless DC electric machines with variable frequency drive is rapidly increasing due to their higher efficiency versus typical AC motors, industries are not fully aware of the potential benefits of these machines and their applications. In this paper, recent applications of brushless DC machines in oil & gas, transportation, home appliance, HVAC and refrigeration, marine propulsion and electricity production and their potential energy saving are reviewed.