Cover

Aims and Scope
Editorial Board

1. Mechanical behaviour of PEM fuel cell catalyst layers during regular cell operation

Maher A.R. Sadiq Al-Baghdadi

Fuel Cell Research Center, International Energy & Environment Foundation, Al-Najaf, P.O.Box 39, Iraq.

Abstract: Damage mechanisms in a proton exchange membrane fuel cell are accelerated by mechanical stresses arising during fuel cell assembly (bolt assembling), and the stresses arise during fuel cell running, because it consists of the materials with different thermal expansion and swelling coefficients. Therefore, in order to acquire a complete understanding of the mechanical behaviour of the catalyst layers during regular cell operation, mechanical response under steady-state hygro-thermal stresses should be studied under real cell operating conditions and in real cell geometry (three-dimensional). In this work, full three-dimensional, non-isothermal computational fluid dynamics model of a PEM fuel cell has been developed to investigate the behaviour of the cathode and anode catalyst layers during the cell operation. A unique feature of the present model is to incorporate the effect of hygro and thermal stresses into actual three-dimensional fuel cell model. In addition, the temperature and humidity dependent material properties are utilize in the simulation for the membrane. The model is shown to be able to understand the many interacting, complex electrochemical, transport phenomena, and deformation that have limited experimental data.

Volume 1, Issue 6, 2010, pp.927-936.

2. CFD for hydrodynamic efficiency and design optimization of key elements of SHP

Ana Pereira, Helena M. Ramos

Civil Engineering Department and CEHIDRO, Instituto Superior Técnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001, Lisbon, Portugal.

Abstract: This paper aims to study how the flow behaves in key elements of small hydropower plants (SHP) which  should be well designed in order to achieve properly the best hydraulic and energy efficiency. There are some hydrodynamic and structural fundaments that all hydro circuits design has to follow, and there are other aspects that vary from design to the flow behavior. The variables that influence the hydro systems design are related with performance, technical, operational and environmental aspects. For instance, design discharge, produced energy, intakes and outlets geometry are some of the technical variables. The components of SHP design should be characterized by a balance between hydraulic, structural, operational and environment efficiency and economic issues. To improve the hydraulic efficiency is necessary information concerning with hydrodynamic flow behavior. The knowledge in this area is still insufficient since the hydrodynamic flow patterns, in some key elements of hydraulic circuits of SHP are quite complex. Therefore this paper uses an advanced computational fluid dynamic (CFD) model for flow simulation, with the aim to improve the behavior comprehension enabling the identification of parameters’ variation which influences the performance efficiency of those components in the design criteria of such SHP. Since the inefficiency and the unsafe operating conditions are normally associated to separated flow zones, vorticity development, macro turbulence intensity, pressure gradients, shear stress increase, this paper intends to analyze causes and consequences of the flow behavior. Among these concerns it is possible to identify induced problems, such as vibrations, resonance effects, ruptures or collapses, cavitation, water column separation, significant friction losses, vortices and regions of reversed flow.

3. Computational fluid dynamics analysis of a twisted airfoil shaped two-bladed H-Darrieus rotor made from fibreglass reinforced plastic (FRP)

Rajat Gupta, Sukanta Roy, Agnimitra Biswas

Department of Mechanical Engineering, National Institute of Technology, Silchar, Assam, 788010 India.

Abstract: H-Darrieus rotor is a lift type device having two to three blades designed as airfoils. The blades are attached vertically to the central shaft through support arms. The support to vertical axis helps the rotor maintain its shape. In this paper, Computational Fluid Dynamics (CFD) analysis of an airfoil shaped two-bladed H-Darrieus rotor using Fluent 6.2 software was performed. Based on the CFD results, a comparative study between experimental and computational works was carried out. The H-Darrieus rotor was 20cm in height, 5cm in chord and twisted with an angle of 30° at the trailing end. The blade material of rotor was Fiberglass Reinforced Plastic (FRP). The experiments were earlier conducted in a subsonic wind tunnel for various height-to-diameter (H/D) ratios. A two dimensional computational modeling was done with the help of Gambit tool using unstructured grid. Realistic boundary conditions were provided for the model to have synchronization with the experimental conditions. Two dimensional steady-state segregated solver with absolute velocity formulation and cell based grid was considered, and a standard k-ε viscous model with standard wall functions was chosen. A first order upwind discretization scheme was adopted for pressure velocity coupling of the flow. The inlet velocities and rotor rotational speeds were taken from the experimental results. From the computational analysis, power coefficient (C_p) and torque coefficient (C_t)  values at ten different H/D ratios namely 0.85, 1.0, 1.10, 1.33, 1.54, 1.72, 1.80, 1.92, 2.10 and 2.20 were calculated in order to predict the performances of the twisted H-rotor. The variations of C_p and C_t with tip speed ratios were analyzed and compared with the experimental results. The standard deviations of computational C_p and C_t from experimental C_p and C_t were obtained. From the computational analysis, the highest values of C_p and C_t were obtained at H/D ratios of 1.0 and 1.54 respectively. The deviation of computational C_p from experimental C_p was withinplus-minus 2.68%. The deviation of computational C_t from experimental C_t was within3.66%. Thus, the comparison between computational works and experimental works is quite encouraging.

4. Finite time exergoeconomic performance optimization for an irreversible universal steady flow variable-temperature heat reservoir heat pump cycle model

Huijun Feng, Lingen Chen, Fengrui Sun

Postgraduate School, Naval University of Engineering, Wuhan 430033, P. R. China.

Abstract: An irreversible universal steady flow heat pump cycle model with variable-temperature heat reservoirs and the losses of heat-resistance and internal irreversibility is established by using the theory of finite time thermodynamics. The universal heat pump cycle model consists of two heat-absorbing branches, two heat-releasing branches and two adiabatic branches. Expressions of heating load, coefficient of performance (COP) and profit rate of the universal heat pump cycle model are derived, respectively. By means of numerical calculations, heat conductance distributions between hot- and cold-side heat exchangers are optimized by taking the maximum profit rate as objective. There exist an optimal heat conductance distribution and an optimal thermal capacity rate matching between the working fluid and heat reservoirs which lead to a double maximum profit rate. The effects of internal irreversibility, total heat exchanger inventory, thermal capacity rate of the working fluid and heat capacity ratio of the heat reservoirs on the optimal finite time exergoeconomic performance of the cycle are discussed in detail. The results obtained herein include the optimal finite time exergoeconomic performances of endoreversible and irreversible, constant- and variable-temperature heat reservoir Brayton, Otto, Diesel, Atkinson, Dual, Miller and Carnot heat pump cycles.

5. An experimental investigation of heat transfer and fluid flow in a rectangular duct with inclined discrete ribs

K. R. Aharwal ¹, B. K. Gandhi ², J. S. Saini ²

1 Department of Mechanical Engineering S.G.S.I.T.S. Indore (M.P.), India.

2 Department of Mechanical and Industrial Engineering I.I.T. Roorkee (U.A.), India.

Abstract: Artificial roughness in the form of repeated ribs is generally used for enhancement of heat transfer heated surface to the working fluid. In the present work experimental investigations has been carried out to study the effect of a gap in the inclined rib on the heat transfer and fluid flow characteristics of heated surface. A rectangular duct of aspect ratio of 5.83 has been used to conduct experiments on one rib roughened surface. Experimental data have been collected to determine Nusselt number (heat transfer coefficient) as a function of roughness and flow parameters in the form of repeated ribs. In order to understand the mechanism of heat transfer through a roughened duct having inclined rib with and without gap, the detailed analysis of the fluid flow structure is required. Therefore the detailed velocity structures of fluid flow inside a similar roughened duct as used for the heat transfer analysis were obtained by 2-Dimensional Particle Image Velocimetry (PIV) system and the heat transfer results were correlated with the flow structure. It was found that inclined rib with a gap (inclined discrete rib) had better heat transfer performance compared to the continuous inclined rib arrangement. Further the inclined discrete rib with relative gap width (g/e) of 1.0 gives the higher heat transfer performance compared to the other relative gap width.

6. Study of contaminants stemmed from the waste water of the Ivorian Refining Company

Loukou Kouakou, Abolle Abolle, Henri Planche

Unite de Chimie et Procedes de l'Ecole Nationale Superieure des Techniques Avancees, 32 Boulevard Victor, 75739 Paris Cedex 15, France.

Abstract: The dissolved hydrocarbons in waste water from the Ivorian Refining Company (SIR) are analyzed by means of a GC/MS coupling. The range of molar masses represented fairly fits the range of saturated hydrocarbons present in the treated crude oils. From this, it is deduced that solubility tables of pure hydrocarbons in water are not relevant for evaluating the risk of pollution propagation in the Ebrié lagoon. Aromatics are represented almost totally by toluene which is a molecule representing more than the half of total hydrocarbons. This particularity suggests that saturated hydrocarbons with high molecular weight found in the water form micelles with the toluene behaving as a surfactant. This molecule would be the main dispersion vector of hydrocarbons pollutants. The study of the ageing of these waters shows that they contain some agent responsible for biodegradation. These agents destroy the paraffins made soluble by the toluene.

7. Potential biogas production from sewage sludge: A case study of the sewage treatment plant at Kwame Nkrumah university of science and technology, Ghana

RichardArthur¹, Abeeku Brew-Hammond²

1 Energy Systems Engineering Department, Koforidua Polytechnic, Box KF 981, Koforidua, Ghana.

2 Faculty of Mechanical and Agricultural Engineering, Kwame Nkrumah University of Science and Technology (KNUST), Private Mail Bag, Kumasi, Ghana.

Abstract: Biogas generation is one of the most promising renewable energy sources in Ghana. Anaerobic digestion is one of the effective ways of generating biogas. Anaerobic digestion is also a reliable method for wastewater treatment and the digestion the effluent can be used as fertilizer to enhance the fertility of the soil. This paper looks at the possibility of constructing a biogas plant at the KNUST sewage treatment plant tapping its feedstock the sludge at the Primary Sedimentation Tank to generate biogas. A laboratory experiment was done to determine the faecal sludge quality. The flowrate of the sludge was estimated based on the number of times the penstocks (valves) are operated to desludge the sewage which also depends on whether the university is on vacation (35.72 m³/day) or in session (71.44 m³/day). These parameters were used to determine the biogas potential of the sewage using 10, 20 and 30 days retention time for plant sizes of 540 m³, 1100m³ and 1600 m³ respectively. It was estimated that 170,719 m³, 341,858 m³ and 419,458 m³ of methane can be produced in a year and the power production was estimated to be 50 kW, 100 kW and 120 kW for the 540 m³, 1100m³ and 1600 m³ digester sizes respectively.

8. Performance of Jatropha curcas: A biofuel crop in wasteland of Madhya Pradesh, India

A.K.Pandey, Pankaj Bhargava, Nivedika Gupta, Dhanshree Sharma

Non Wood Forest Produce Division, Tropical Forest Research Institute, P.O. RFRC, Jabalpur  482021, India.

Abstract: In India vast tracts of land (20.17% of total geographical area) exists as wastelands accounting for about 63.85 million hectares. Wastelands are degraded lands that lack their life sustaining potential as a result of inherent or imposed disabilities such as by location, environment, chemical and physical properties of the soil or financial or management constraints. In recent years, the central government and many of the state governments have expressed their support for bringing wastelands, under cultivation. Jatropha curcas has been found most promising for this purpose due to the use of its seed oil as biodiesel and other favorable attributes like hardy nature, short gestation period and adaptability in a wide range of agro-climatic conditions etc. Jatropha plantation helps in restoration of vast stretches of wastelands into green oil fields and can address major issues of developing countries like energy security, environmental amelioration, rural employment generation and conservation of foreign exchange reserves. With the objective to evaluate the performance of Jatropha plants in wasteland conditions, Tropical Forest Research Institute, Jabalpur has initiated a study in 2006. Progeny trial was laid out in Barha (Jabalpur) locality comprising of 20 superior genotypes of Jatropha. Among them, Gessani Shivpuri 3, Gessani Shivpuri 2, Bilara Pohiri Shivpuri 2, Parsoria Damoh Sagar, Bizouli Janarpura Gwalior 3, Bizouli Janarpura Gwalior 2 and Dewari Sagar 1 genotype are performing better as compared to other genotypes. This information will be helpful in assessing of the potential of locally adapted accessions and provide baseline information for future Jatropha plantation and wasteland reclammation programmes.

9. Heat transfer enhancement of free surface MHD-flow by the wall with non-uniform electrical conductivity

H. L. Huang, B. Li

Academy of Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, P.R.China.

Abstract: Due to the Magnetohydrodynamic (MHD) effect, which degrades heat transfer coefficients by pulsation suppression of external magnetic field, on the electrically conducting flow, the wall with non-uniform electrical conductivity is employed in a free surface MHD-flow system for heat transfer enhancement. The non-uniform electrical conductivity distribution of the channel wall may create alternate Lorentz forces along spanwise direction, which can effectively produce flow disturbance, promote mixture, reduce the thickness of boundary layer, and enhance heat transfer. So the heat transfer performances enhanced by some conducting strips aligned with the mean flow direction on the insulating wall of free surface MHD-flow are simulated numerically in this paper. The flow behaviors, heat transfer coefficients, friction factors and pressure drops are presented under different Hartmann numbers. Results show that, in the range of Hartmann numbers 30≤Ha≤100, the wall with non-uniform conductivity can achieve heat transfer enhancements (Nu/Nu0) of about 1.2 to 1.6 relative to the insulating wall, with negligible friction augmentation. This research indicates that the modules with three or five conducting strips can obtain better enhancement effect in our research. Particularly, the heat transfer augmentation increases monotonically with increasing Hartmann numbers. Therefore, the enhancement purpose for high Hartman number MHD-flow is marked, which may remedy the depressing heat transfer coefficients by MHD effect.

10. Two-zone modeling of diesel / biodiesel blended fuel operated ceramic coated direct injection diesel engine

B. Rajendra Prasath¹, P. Tamil Porai², Mohd. F. Shabir¹

1 Department of Mechanical Engineering, Tagore Engineering College, Anna University Chennai, India.

2 Department of Mechanical Engineering, Anna University Chennai, India.

Abstract: A comprehensive computer code using ”C” language was developed for compression ignition (C.I) engine cycle and modified in to low heat rejection (LHR) engine through wall heat transfer model. Combustion characteristics such as cylinder pressure, heat release, heat transfer and performance characteristics such as work done, specific fuel consumption (SFC) and brake thermal efficiency (BTE) were analysed. On the basis of first law of thermodynamics the properties at each degree crank angle was calculated. Preparation and reaction rate model was used to calculate the instantaneous heat release rate. The effect of coating on engine heat transfer was analysed using a gas-wall heat transfer calculations and total heat transfer was based on ANNAND’s combined heat transfer model. The predicted results are validated through the experiments on the test engine under identical operating conditions on a turbocharged D.I diesel engine. In this analysis 20% of biodiesel (derived from Jatropha seed oil) blended with diesel was used in both conventional and LHR engine. The simulated combustion and performance characteristics are found satisfactory with the experimental results.

11. Dynamic effects in reversible hydro systems towards safety solutions

Pedro A. Morgado, Helena M. Ramos

Civil Engineering Department and CEHIDRO, Instituto Superior Técnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001, Lisbon, Portugal.

Abstract: The purpose of this paper is to establish general strategies to evaluate the dynamic effects occurring in reversible hydro systems (i.e. turbine/pumping) with long penstocks resulting from the regular operation of the hydro equipments and, most significantly, from accidental events. It is of great importance these particular aspects are considered in the early stages of a design, in order to ensure the best technical, economical and safety operation for each developed solution. This work presents two complementary approaches to the study of dynamic effects associated to reversible hydro systems based on a parametric analysis and a simulation-based procedure, as well as in the definition of design and operation rules to guarantee a safe solution. The first approach establishes the dynamic behavior of the system by means of a parametric analysis of the hydraulic and the hydro mechanical aspects associated to system operation. Based on this methodology, it is possible to estimate the maximum upsurge, the flow variation under turbogenerators runaway conditions and a valve manoeuvre. The second approach consists in the implementation of a numerical model that simulates accurately enough, the interaction between different components of the system during transient flow regimes associated to the hydropower load rejection, pumps shutdown, actuation of upsurge protection devices and wave propagations along the all system. This methodology gathers the necessary tools for the computational transient analysis of a complex reversible system.

12. Smooth-operating point and theoretical analyses of unsmooth operation in pyrological processes

Wenqiang Sun¹, Jiuju Cai¹, Fangmin Quan^1,2, Shizheng Ren³

1 SEPA Key Laboratory on Eco-industry, Institute of Thermal and Environmental Engineering, Northeastern University, Shenyang 110819, P. R. China.

2 Jirui Renewable Resources Development Co., Ltd., JISCO, Jiayuguan 735100, P. R. China.

3 School of Materials and Metallurgy, Northeastern University, Shenyang 110819, P. R. China.

Abstract: To emphasize the role of heat loss in energy conservation, this paper introduces smooth operation principle. By least square method, the smooth-operating point (SOP) formula of fuel gas with definite composition and temperature is deduced, which is then used to analyze changes in heat effect when injecting heat at unsmooth-operating point (UOP), educe allocation regulations of heat effect in furnace, and study the heat loss resulting from unsmooth operation. It indicates that for fuel gas with definite composition and temperature, the SOP is unique and there is no heat loss if injecting heat at SOP. With regard to unsmooth operation, low UOP is better than a high one.

13. Integrated energy planning for sustainable development in rural areas: A case study from Eastern Uttar Pradesh

Shweta Singh, Usha Bajpai

Renewable Energy Research Laboratory, Department of Physics, University of Lucknow, Lucknow 226 007, India.

Abstract: Energy is required for every aspect of our daily life. At present, commercial energy consumption makes up about 65% of the total energy consumed in India. This includes coal with the largest share of 55%, followed by oil at 31%, natural gas at 11% and hydro energy at 3%.  Non-commercial energy sources consisting of firewood, cow dung and agriculture wastes account for over 30% of the total energy consumption. The critical feature of India’s energy sector and linkages to economy is the import dependence on crude and petroleum products. Import bill is likely to grow to more than 100% in the near future because of population explosion and improved living standard in the country. Being a tropical country India has unlimited potential for producing renewable energy sources. These sources of energy can play an important role in the sustainable development by providing basic energy needs of rural and remote areas. A survey of energy consumption pattern has been carried out in different sector domestic, agricultural, transport, rural industries and miscellaneous uses in a cluster of 3 villages, district Ballia, Uttar Pradesh India during 2008. The questionnaires have been filled by gram pradhan, respective old persons and head of the family of the surveyed households. This paper discusses the current energy status, choice of energy options and potential of renewable energy systems for creating sustainable livelihoods in rural areas. The outline plan at decentralized level was prepared with the objective of providing energy security in villages by meeting total energy needs for cooking, lighting and motive power through various forms of available renewable energy sources.

14. Kinetics of palm kernel oil and ethanol transesterification

Julius C. Ahiekpor ¹, David K. Kuwornoo ²

1 Centre for Energy, Environment and Sustainable Development (CEESD), P.O. Box FN 793, Kumasi, Ghana.

2 Faculty of Chemical and Materials Engineering, Kwame Nkrumah University of Science and Technology (KNUST), Private Mail Bag, Kumasi, Ghana.

Abstract: Biodiesel, an alternative diesel fuel made from renewable sources such as vegetable oils and animal fats, has been identified by government to play a key role in the socio-economic development of Ghana. The utilization of biodiesel is expected to be about 10% of the total liquid fuel mix of the country by the year 2020. Despite this great potential and the numerous sources from which biodiesel could be developed in Ghana, there are no available data on the kinetics and mechanisms of transesterification of local vegetable oils. The need for local production of biodiesel necessitates that the mechanism and kinetics of the process is well understood, since the properties of the biodiesel depends on the type of oil use for the transesterification process. The objective of this work is to evaluate the appropriate kinetics mechanism and to find out the reaction rate constants for palm kernel oil transesterification with ethanol when KOH was used as a catalyst. In this present work, 16 biodiesel samples were prepared at specified times based on reported optimal conditions and the samples analysed by gas chromatography. The experimental mass fractions were calibrated and fitted to mathematical models of different proposed mechanisms in previous works.The rate data fitted well to second-order kinetics without shunt mechanism. It was also observed that, although transesterification reaction of crude palm kernel oil is a reversible reaction, the reaction rate constants indicated that the forward reactions were the most prominent.

15. Dynamic stability analysis of microgrid by integrating transfer function of DERs

Prasenjit Basak ¹, S. Chowdhury ², S.P. Chowdhury ²

1 Calcutta Institute of Engineering & Management, Electrical Engineering Department, Kolkata, India.

2 University of Cape Town, Electrical Engineering Department, Cape Town, South Africa.

Abstract: A microgrid is an integrated form of distributed energy resources (DERs) which are connected together to serve electrical power to the selected consumers or can exchange power with the existing utility grid suitably under standalone or grid connected mode. The microgrid can be cited as a physical system which is a combination of DERs such as, Photovoltaic Generator, Wind turbine, Fuel Cell, Microturbine etc. and can be modelled   with suitable assumptions depending upon specific operational condition to be studied. Interconnection of several kinds of power sources would impact the quality of power within the microgrid. Since voltage and frequency are not the only factors for a system delivering good quality power, the capacity of the same to withstand instability due to transient condition is one of the prime factors to be considered to accept a system as a stable system. Before practical integration of distributed energy resources, it would be essential to check the stability of the system at the design stage. In this paper, the authors have presented the microgrid based on control system engineering. To represent the individual components of microgrid, the DERs (Distributed Energy Resources) have been represented with their transfer functions and they have been simulated using Simulink-Matlab. To observe the response of the DERs, the frequency fluctuation due to step and random change in output power/load are considered as the main factors for stability analysis. All the DERs are integrated forming the microgrid which is represented with an equivalent transfer function based model. The models are studied and results are discussed with the waveforms. This paper shows one feasible method to check the dynamic stability of a proposed microgrid.