Exergy analysis of the diesel pre-reforming solid oxide fuel cell system with anode off-gas recycling in the SchIBZ project. Part I: Modeling and validation

Solid oxide fuel cell (SOFC) systems with anode off-gas recirculation (AGR) and diesel pre-reforming are advantageous because they can operate with the current fuel infrastructure. In the SchIBZ-project, the prototype of such a SOFC system for maritime applications has already been commissioned. In this first paper, we model the system devices to conduct an exergy analysis of this real SOFC plant and validate them with experimental values from experiments in laboratory scale. The results of our simulation agree well with the experimental values. The calculations with the validated results may be closer to the real thermodynamic behavior of such system components than previous literature.     

High Performance Tubular Heat Exchanger with Minijet Heat Transfer Enhancement

ABSTRACT

In the paper, the original cylindrical heat exchanger with minijets (MJHE) was introduced. The systematic experimental analysis of the prototype heat exchanger was described with special attention paid to such parameters as the heat transfer effectiveness, heat transfer rates, overall heat transfer coefficients, and pressure drop. The heat transfer coefficients were determined based on Wilson plot method, the most suitable approach for heat transfer coefficient determination in exchangers of complex geometry. The thermal-hydraulic characteristics of the in-house manufactured prototype of MJHE in water–water and gas–water configuration are also presented. The experimental results were compared with the predictions from well-known correlations found in the published research papers dedicated to the free-surface and submerged types of jets.     

A case study of a hydride container performance applying non dimensional parameters

Many efforts have been done so far to understand sorption dynamics of hydride containers for hydrogen storage. Particularly, there are many articles in literature where experimental results for different hydride systems and container set-ups were successfully simulated using basically the same group of models. This fact is the base of a previous work where we defined a series of non dimensional parameters which may be used to estimate absorption time of hydride containers.In this work we compare estimated absorption times with experimental outcomes for a prototype hydride container. We performed non dimensional analysis of our finned container prototype at two scales, i.e.: overall or macroscopic container scale and pore or microscopic scale. We discuss about this simplified model approach that allows estimating, with few parameters, the reaction time of a complex-geometry prototype.The prototype container was designed according to the results of a numerical optimization that maximized the amount of hydrogen absorbed for a 3 min charging period. Experimental results indicate good agreement between estimated and experimental absorption time, making the non dimensional method a useful tool at preliminary stages of hydride container design.     

Power balance considerations for brushless doubly-fed machines

This paper discusses the power balances in a brushless doubly-fed machine (BDFM). Equations of power in the two stator windings and the rotor circuit, showing the distribution of electrical and mechanical powers in the air-gap, are obtained in two different speed ranges of BDFM synchronous mode operation. Comparisons vis-a-vis power distribution are made between the wound-rotor induction machine (WRIM) and the BDFM. A brief analysis of the power balances, along with experimental data points obtained using a laboratory prototype machine, are given     

A novel high power density permanent magnet variable-speed motor

A novel polyphase, multipole, permanent magnet (PM) motor which possesses high power density, high efficiency and excellent controllability, yet can be produced by conventional fabrication techniques, is proposed. The basic operating principles, design features, performance analysis and control system are described. The experimental results for a 5 kW, 1500 RPM prototype PM motor and its comparison with other types of motors such as switched reluctance motors and induction motors are given. This motor also has superior dynamic performance     

Cooling performance and energy saving of a compression–absorption refrigeration system driven by a gas engine

The prototype of combined vapour compression–absorption refrigeration system was set up, where a gas engine drove directly an open screw compressor in a vapour compression refrigeration chiller and waste heat from the gas engine was used to operate absorption refrigeration cycle. The experimental procedure and results showed that the combined refrigeration system was feasible. The cooling capacity of the prototype reached about 589 kW at the Chinese rated conditions of air conditioning (the inlet and outlet temperatures of chilled water are 12 and 7°C, the inlet and outlet temperatures of cooling water are 30 and 35°C, respectively). Primary energy rate (PER) and comparative primary energy saving were used to evaluate energy utilization efficiency of the combined refrigeration system. The calculated results showed that the PER of the prototype was about 1.81 and the prototype saved more than 25% of primary energy compared to a conventional electrically driven vapour compression refrigeration unit. Error analysis showed that the total error of the combined cooling system measurement was about 4.2% in this work. Copyright © 2006 John Wiley & Sons, Ltd.     

Development of a PM transverse flux motor with soft magnetic composite core

This paper reports the design, performance analysis, fabrication, and experimental results of a three-phase, three-stack permanent magnet transverse flux motor with a soft magnetic composite stator core, which was designed to take advantage of the unique properties of the new material. Parameter computations by finite element analysis of the magnetic field and performance prediction by the equivalent electric circuit are discussed. To validate the simulation, a prototype motor has been fabricated and operated with a sensorless, brushless direct coupler drive scheme. The experimental results are thoroughly presented and agree with the theoretical calculations very well.     

Domestic-scale combined heat-and-power system incorporating a heat pump: analysis of a prototype plant

This paper introduces an innovative domestic scale combined heat-and-power plant (CHP), incorporating a heat pump (HP) for single-dwelling applications. The incorporation of a heat pump enhances the flexibility of a domestic scale CHP plant to satisfy domestic energy demand economically. The development, testing and subsequent thermodynamic analysis of the prototype plant are presented. First law thermodynamic analysis of experimental results is compared to equivalent second law analysis. Analysis of experimental results practically demonstrates that heat-pump incorporation satisfies extremely low domestic electrical requirements economically, whilst delivering relatively high thermal output, without resorting to electricity export.     

Design and analysis of a 35 kVA medium frequency power transformer with the nanocrystalline core material

Medium frequency power transformers embedded into power electronics converters are frequently encountered in many applications such as electrical transportation and renewable energy systems and power supplies. Thus, researchers have been focused on soft magnetic materials such as amorphous and nanocrystalline materials to obtain smaller and more efficient transformer designs with the improvements on manufacturing technologies of the high frequency core materials. In this study, the transformer design methodology is proposed with the finite element analysis method, and a 35 kVA medium frequency transformer with nanocrystalline core material is designed. After the sizing stage, three-dimensional model of the transformer is created with finite element analysis software, and then co-simulations of this electromagnetic transformer model with a power electronics converter circuit are performed for practical operation conditions. Furthermore, thermal behavior of the prototype transformer is determined with the thermal coupling analysis, and temperature distribution of the prototype transformer is visualized with a thermal imaging camera. The transformer efficiency, exact equivalent circuit of the transformer and flux distributions in the transformer core are obtained from these simulation studies. In addition, the prototype of the designed transformer is produced and tested. The design conditions and simulation results are validated with experimental studies.     

Analysis of Operation of a Self-Excited Induction Generator With Generalized Impedance Controller

In this paper, analysis of the operation of a stand-alone self-excited induction generator (SEIG) with generalized impedance controller (GIC) (voltage source pulsewidth-modulated bidirectional inverter with dc link battery) has been discussed. Model of the SEIG along with the generalized impedance controller, has been developed in MATLAB/Simulink environment. The simulation results obtained for steady-state operation of the system, following speed and load perturbations have been presented here. The simulation results are validated with the experimental ones, which are conducted on a laboratory prototype of the SEIG-GIC system. The generalized impedance controller is found to be capable of maintaining the frequency of the SEIG constant under open-loop condition, following the speed and load perturbations.     

Design analysis of permanent magnet DC motors with differingarmature, magnet and yoke lengths

A modified magnetic circuit method and a 2-D finite element procedure are presented here for the analysis of DC permanent magnet motors with differing armature, magnet and yoke lengths including nonlinear material behavior of steel and permanent magnet. A 12 V, 120 W motor is analyzed through these methods and compared with experimental results of a prototype sample. In case of finite element analysis, commutation effects and short chording of the armature winding are treated appropriately, and cogging torque and voltage ripple are predicted     

Modelling and testing of a solar-receiver system applied to high-temperature processes

Solar volumetric-receivers have been successfully used in both electricity production and thermochemical applications. This paper studies the applicability of this technology to the production of process heat for high-temperature uses (573–1073 K).As such, a volumetric-receiver system was designed, installed and tested in the Plataforma Solar de Almería's Solar Furnace (SF-60). The facility consisted of an open-volumetric-receiver module connected to a concentrated-solar-energy driven prototype, whose design was based on a previous three-dimensional CFD model.This work focuses on the validation of the CFD model and on the experimental evaluation of the high-temperature solar prototype, taking into account the uncertainty of the experimental and simulation results. Numerical results were in appreciable agreement with the experimental data, which determined that the prototype was able to reach the high-temperature range (850 K) with a homogeneous thermal profile.     

Experimental investigation of a new solar desalination prototype using the humidification dehumidification principle

This paper tackles an experimental investigation of a new solar desalination prototype using the humidification dehumidification principle at the weather conditions of Sfax City, Tunisia. The prototype is designed and constructed at the national engineering school of Sfax to conduct this experimental investigation under different meteorological and operating parameters. It is composed of a flat plate solar air collector, a flat plate solar water collector, a humidifier, an evaporation tower and a condensation tower. An economic analysis was conducted, since it affects the final cost of produced water, to determine both the cost of fresh water production and the payback period of the experimental setup. Although a system may be technically very efficient, it may not be economic. The experimental investigation of the dynamic behaviour of the solar desalination unit during summer season (June, July and August) and during a typical day in July was carried to study the temporal evolutions of the temperature of air and water and the relative humidity at the inlet and the outlet of each component of the system.     

A novel multilayer switched reluctance motor

The switched reluctance motor is a simple and robust machine, which has found application over wide power and speed ranges in different shapes and geometries. This paper introduces a new configuration for a high starting torque switched reluctance motor (SRM). This configuration allows more space for coil windings in small size motors with a high number of stator and rotor poles. It also presents a centrifugal switch mounted on the motor shaft for a sudden advancement of current-pulses relative to rotor position after reaching a preset motor speed in order to develop higher torque at starting. To evaluate the motor performance, two types of analysis, namely numerical techniques and an experimental study have been utilized. In the numerical analysis, due to the highly nonlinear nature of the motor, a finite element analysis is employed, and for the experimental study, a prototype motor has been built and tested. Finally, the prototype motor is compared with a conventional SRM of the same size. The calculated results compare favorably with the test results. In comparison with the conventional SRM, the proposed motor in this paper seems to be very promising     

Bluff body with built-in piezoelectric cantilever for flow-induced energy harvesting

This paper investigates a flow-induced vibration energy harvester comprising a piezoelectric beam (piezo-beam) installed within a hollow circular cylinder. Under the flow excitation, the energy-harvesting system including the cylinder and the piezo-beam vibrates and generates electricity. A lumped parametric model incorporating the fluid-structure interaction (FSI) is developed to evaluate the performance of the proposed energy harvester. Based on the theoretical analysis, several guidelines on the design and optimization of the proposed energy harvester are provided. Subsequently, a numerical model is used to simulate the FSI between the proposed system and the external flow field. Finally, a physical prototype is fabricated and an experiment is conducted to test the actual performance for validation. The theoretical analysis results are verified by the numerical and experimental results.     

Experimental study and modeling of an Organic Rankine Cycle using scroll expander

This paper presents both a numerical model of an Organic Rankine Cycle (ORC) and an experimental study carried out on a prototype working with refrigerant HCFC-123, and whose heat sources consist in two hot air flows. The ORC model is built by interconnecting different sub-models: the heat exchanger models, a volumetric pump model and a scroll expander model. Measured performance of the ORC prototype is presented and used to validate the ORC model. This model is finally used to investigate potential improvements of the prototype.     

Twin cylinder alpha stirling engine combined model and prototype redesign

This article shows the development of a twin cylinder alpha type Stirling engine model, as well as the redesign of a prototype, its manufacture and preliminary results. The mechanical model is coupled with a thermodynamic model which allows an analysis and comparison of the theoretical and experimental behavior of the machine and a better understanding of the whole process. On the other side, a prototype redesign is presented. Thermal circuit was improved in order to eliminate losses, reduce dead volumes and improve heat transfer to the working fluid. Modifications of the seal system and the pistons design are included as well. An equation for the sizing of the flywheel is developed and finally the results obtained in tests between the new and the previous design are compared.     

压缩比对内燃机性能的影响研究

笔者从理论的角度定性地分析了内燃机压缩比分别对其循环热效率、平均有效压力、工质状态和换气过程的影响。再以2135G柴油机为原型机,利用AVL boost软件建立仿真模型,定量地分析了柴油机压缩比与其工作参数的关系和对整机性能参数的影响规律,通过分析计算,为柴油机压缩比的合理选择提供了理论依据。     

Convective heat transport along a thermoacoustic couple in the transient regime

This work proposes a simple calculus procedure based on the linear thermoacoustic theory. The methodology applies on rate of change (time derivative) rather than on steady state temperature distributions so it constitutes a complementary to conventional analysis to perform test on the reliability and applicability of the linear theory. The procedure has been applied to experimental data collected by means of a simple prototype of thermoacoustic device. The apparatus, whose technical characteristics are described in detail along with the data acquisition procedure, has been able to highlight the general features of the thermoacoustic effect. Measurements concern the acoustically generated temperature gradients across a ThermoAcoustic Couple, a structure firstly introduced by Wheatley and coworkers in 1983. The obtained results indicate that heat transfer phenomena are more critical than non linear acoustic behavior in determining the overestimation that theoretical predictions make on experimental values.