فصلنامه مهندسی و مدیریت انرژی
سال چهارم شماره 2 (پیاپی 12، تابستان 1393)

In this paper، a novel control strategy for a Shunt Active Power Filter (shunt-APF) is proposed. In the proposed control strategy which is based on a new application of the instantaneous reactive power theory، the current injected by the shunt-APF is capable of compensation for the reactive component، the harmonic components and also unbalance of the load current. In this strategy، the shunt-APF acts so that the set of load and shunt-APF is seen as a balanced three phase resistance from the source side. The simulation results in PSIM show the effectiveness of the proposed control strategy.

A Number of Industries release large amounts of water vapor into the atmosphere through their stacks. The flue gas can be a potential source for obtaining the required water for those industries. Separation process of water vapor by means of membrane condenser exchanger was studied. Numerical simulation of the process was conducted by COMSOL software using computational fluid dynamics. Simulation was based on solving conservation equations for solute in the membrane condenser exchanger. The tube wall is made of a specially designed porous material that is capable to extract condensated liquid from the flue gas. The tubes capture، recover، and reuse sensible and latent waste heat، along with the water vapor from the exhaust or flue gas. The clean water can be returned to the system. The nanoporous ceramic membrane tubes capture water via capillary condensation، which occurs more readily within nanoporous ceramic pores rather than with typical steel finned tube economizers. Comparison of the model results with experimental data proved the validity of the model with a deviation of less than 6%. The achieved results indicated that 20% of water and energy could be recovered only by a temperature reduction less than 10 °C if the flue gas was in regular conditions (60 °C < T <90 °C and 10% < RH < 20%).

In this study، detailed fluid flow and heat transfer in cooling plates of polymeric membrane fuel cell is studied using computational fluid dynamics (CFD) techniques. The performances of four different coolant flow field designs were compared in terms of the maximum surface temperature، temperature uniformity and pressure drop characteristics. The results indicate that the porous flow field with metal foaming structure is the best model for reducing surface temperature difference، maximum surface temperature and maximum average temperature among the other models which were studied in this paper. On the other hand، because of high permeable coefficient، coolant fluid pressure drop is rather low in the model (1. 4kPa in comparison with 1. 7kPa and 6. 5kPa at serpentine fields). So the model has the potential to be used as coolant fluid distributor to improve fuel cell performance، of course further optimization is required to improve the design.

This paper investigates the effects of subcooling the condenser outlet refrigerant in a compression refrigeration by an absorption refrigeration in an integrated refrigeration system from energy view point. For this purpose the thermodynamic system is analyzed، base on the mass and energy equation and also the effects of operating parameters such as prime mover، ambient temperature and evaporator temperature on the work of compressor and performance of the integrated refrigeration system are considered. LiB-H2O and NH3-H2O are used as fluid pair in an absorption section. Result indicates that integrated refrigeration system with H2O-NH3 having a better EUF than LiBr-H2O integrated refrigeration system. The results show that increasing the ambient temperature and decreasing the evaporator temperature enhance the improvement of EUF and also the use of SOFC as a prime mover has significant advantages.

In this research، Magneto-Hydro-Dynamic subsonic flow in a MHD generator has been simulated and its effect on efficiency and power generation of a triple cycle has been investigated. A 2D constant cross-section Faraday channel with segmented electrodes was used as MHD generator. MHD flow was assumed steady and compressible with ideal five-wave model MHD equations. Navier-Stokes equations were solved with an implicit density based method and the Poisson equation was solved by electric potential method. The suggested triple cycle consists of an open-cycle MHD as a topping cycle، gas turbine as the middle generator and steam turbine as bottoming cycle. A MATLAB code consists of the thermodynamic relations، governing the triple cycle behavior has been developed to analyze the performance of the combined cycle base on the MHD generator. Results showed that for a constant cross-section subsonic MHD generator، the maximum enthalpy extraction can be achieved for Mach numbers between 0. 3 and 0. 4 and the magnetic field between 4 and 6 Tesla. The enthalpy extraction of the MHD generator at Mach number of 0. 3 and magnetic field of 6 Tesla increases up to 12. 27%. Besides the optimum efficiency of 63. 59% is achieved compared to the combined cycle without MHD generator، which was estimated almost 40. 89%.

In this paper، the feasibility of using heat energy of steam turbine combined cycle power plant as the energy required to start up desalination systems has been studied. The optimal model of combined cycle power plant equipped with a multi-effect desalination plants in different design modes of the effects of desalination and steam pressure of the steam turbine output has been evaluated. In order to develop a code for designing of desalination units، mass and energy equations of desalination systems of non-linear control volume method has been solved using MATLAB and optimization model of a dual system power plant with desalination system. The demand for water and electricity in accordance with the design requirements، by the economic indicators of the payback period (PB) and internal return of rate (IRR) has been introduced. According to the results، three-effect desalination under pressure steam turbine of three bars with internal return of rate of 21. 73% and a payback period of 4. 5 years has been presented as the optimal model of combined water and power (CWP) system.