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Aims and Scope
Editorial Board

1. A parametric study of assembly pressure, thermal expansion, and membrane swelling in PEM fuel cells

Maher A.R. Sadiq Al-Baghdadi

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

Abstract: Proton Exchange membrane (PEM) fuel cells are still undergoing intense development, and the combination of new and optimized materials, improved product development, novel architectures, more efficient transport processes, and design optimization and integration are expected to lead to major gains in performance, efficiency, durability, reliability, manufacturability and cost-effectiveness. PEM fuel cell assembly pressure is known to cause large strains in the cell components. All components compression occurs during the assembly process of the cell, but also during fuel cell operation due to membrane swelling when absorbs water and cell materials expansion due to heat generating in catalyst layers. Additionally, the repetitive channel-rib pattern of the bipolar plates results in a highly inhomogeneous compressive load, so that while large strains are produced under the rib, the region under the channels remains approximately at its initial uncompressed state. This leads to significant spatial variations in GDL thickness and porosity distributions, as well as in electrical and thermal bulk conductivities and contact resistances (both at the ribe-GDL and membrane-GDL interfaces). These changes affect the rates of mass, charge, and heat transport through the GDL, thus impacting fuel cell performance and lifetime. In this paper, computational fluid dynamics (CFD) model of a PEM fuel cell has been developed to simulate the pressure distribution inside the cell, which are occurring during fuel cell assembly (bolt assembling), and membrane swelling and cell materials expansion during fuel cell running due to the changes of temperature and relative humidity. The PEM fuel cell model simulated includes the following components; two bi-polar plates, two GDLs, and, an MEA (membrane plus two CLs). This model is used to study and analyses the effect of assembling and operating parameters on the mechanical behaviour of PEM. The analysis helped identifying critical parameters and shed insight into the physical mechanisms leading to a fuel cell durability under various operating conditions. The model is shown to be able to understand the effect of pressure distribution inside the cell on the performance and durability that have limited experimental data.

Volume 7, Issue 2, 2016, pp.97-122.

2. Performance of photovoltaic systems: Green office’s case study approach

Juliana D’ Angela Mariano¹, Henrique M. Campos¹, Fabianna S. Tonin², Jair Urbanetz Junior^{1, 2}, Eloy F. Casagrande Junior¹

1 Post-graduation Program on Civil Engineering, Technological Federal University of Paraná, Curitiba, Brazil.

2 Post-graduation Program on Electrical Engineering, Technological Federal University of Paraná, Curitiba, Brazil.

Abstract: The aim of this paper is to highlight the parameters that interfere in the performance of grid-connected PV systems. In the three years of analysis, the energy generated and the solar radiation were locally monitored and used to calculate the performance parameters, such as Final Yield, Performance Ratio and Capacity Factor. The results obtained are related to the three years of operation of the Green Office PV system located in UTFPR. The case study compares the monitored PV system in Curitiba, as well as the literature cases in Santa Catarina and Pará states, in order to analyze the photovoltaic systems performance in several conditions. The results were very close in each case, although in Pará PV system case the highest final yield is explained by its location, which is close to the Equator’ line, therefore there are the highest solar radiations in Brazil. In the end some suggestions were made to improve the GO’s grid-connected PV system, because it has revealed a significant performance decrement, mainly due to partial shading losses.

3. Earthing system for stand alone PV solar house

M. Nassereddine, J. Rizk, M. Nagrial, A. Hellany

School of Computing, Engineering & Mathematics, Western Sydney University, Penrith, Australia.

Abstract: Renewable energy is becoming an essential element when it comes to climate change. The advance technology in energy storage increases the installation of standalone system for residential houses. As the solar system is the sole power source for the property, a rigid reliability system should be designed. The paper addresses the earthing requirement for the standalone system to mitigate lightning strike, transfer voltage from nearby high voltage infrastructure and adequate protection operation. Case study is also included.

4. Turbulent flow heat transfer and pressure loss in a double pipe heat exchanger with triangular fins

Vinous M. Hameed, Bashar Muslem Essa

Mechanical Engineering Department, College of Engineering, Al-Nahrain University, Baghdad, Iraq.

Abstract: Experimental investigation of heat transfer and friction factor characteristics in a double pipe heat exchanger with triangular fins was studied. The working fluids were air, flowing in the annular pipe, and water through the inner circular tube. The test section is consisting of two parts. The first part is an insulated tube which has been manufactured from Perspex material of (54mm) inner diameter, (2000mm) length and (3mm) thickness. The second part is an internal copper tube without or with triangular copper fins. The smooth copper tube has (2250mm) long and (20mm, 22mm) inner and outer diameter respectively. The triangular fins were made of the copper with thickness of 0.3mm and 10mm height. They were installed on the straight copper tube section in three different cases (32, 27, and 22) mm distance between each two successive fins and (15mm) pitch between each two of fins. Air at various mass flow rates (0.001875 to 0.003133) kg/sec flows through annuli and water at Reynold's numbers ranging from (10376.9 to 23348.03) flows through the inner tube. The inlet cold air and hot water temperatures are 30oC and 70oC, respectively. The experimental results showed an increase in convective heat transfer coefficient by decreasing in distance between two fins and by increasing Reynold's number. This is due to increase in surface area. It was found that (Space=22mm) gives good heat transfer enhancement.

5. Evaluation of a pilot-scale wood torrefcaction plant based on pellet properties and Finnish market economics

Tapio Ranta¹, Jarno Föhr¹, Hanne Soininen²

1 Lappeenranta University of Technology, Lönnrotinkatu 7 50100, Mikkeli, Finland.

2 Mikkeli University of Applied Sciences, Patteristonkatu 3 D, 50100 Mikkeli, Finland.

Abstract: In this study torrefaction was demonstrated at a Torrec Ltd. pilot plant located in Mikkeli, eastern Finland. The pilot plant with a nominal capacity of 10,000 tonnes/year began operation in August 2014. The torrefaction solution was a batch type process based on a vertical reactor, where biomass material flows by gravity without drives or actuators and torrefaction happens by steam inertization and accurate process control. Steam was supplied from the local biomass combined heat and power (CHP) plant next to the pilot plant. The product quality of torrefied pellets was analysed by testing alternative local woody biomass sources, such as forest chips made from coniferous trees (spruce, pine) and broadleaf (birch), as well as by-products such as veneer chips. Lower heating value as dry basis varied 18.47–20.53 MJ/kg with a moisture content of 4.41-8.60% for torrefied pellets. All raw materials were suitable for torrefied pellet production without binder addition. Noteworthy was good results also with hardwood species. The potential Finnish customers are CHP plants aiming to replace coal with pellets. In 2013 coal use was 31.2 TWh, where condensing was 15.3 TWh, CHP 14.2 TWh, and separate heat 1.6 TWh in Finland. If half of the current coal use in CHP would be replaced by biocoal, then Finnish potential bio-coal markets would be 7 TWh or 1.2 million tonnes of pellets/year. Aided by the results of this demonstration study and modelling of logistics it is possible to evaluate the competitiveness of torrefied pellets based on the local circumstances.

6. Experimental investigation of compound side weir with modeling using computational fluid dynamic

Saleh I. Khassaf¹, Ali N. Attiyah², Hayder A. Al-Yousify²

1Civil Engineering Department, University of Basrah, Iraq.

2Civil Engineering Department, University of Kufa, Iraq.

Abstract: Side weirs, also known as lateral weirs, are flow diversion devices widely used in irrigation as a head regulator of distributary and escapes, land drainage, and urban sewage systems. The modeling of side weir is a sophisticated problem in the hydraulic engineering. The coefficient of discharge over side weirs were investigated by many of the researchers experimentally and theoretically. In this study, the coefficient of discharge over the two compound side weirs (Rectangular and Semi-Circle) were modeled by using Computational Fluid Dynamic (CFD) to describe the flow characteristics in subcritical flow conditions. (Flow-3D) program was used to determine the numerical uncertainty of the simulation results. The simulation results were compared with experimental observations, and good agreements were obtained between the both results.

7. Optimal configuration for a finite low-temperature source refrigerator cycle with heat transfer law

Jun Li^1,2,3, Lingen Chen ^1,2,3, Yanlin Ge^1,2,3, Fengrui Sun^1,2,3

1 Institute of Thermal Science and Power Engineering, Naval University of Engineering, Wuhan 430033.

2 Military Key Laboratory for Naval Ship Power Engineering, Naval University of Engineering, Wuhan 430033.

3 College of Power Engineering, Naval University of Engineering, Wuhan 430033.

Abstract: The optimal configuration of a refrigeration cycle operating between a finite low-temperature source and an infinite high-temperature sink are derived by using finite time thermodynamics based on a complex heat transfer law, including Newtonian heat transfer law, linear phenomenological heat transfer law, radiative heat transfer law, Dulong-Petit heat transfer law, generalized convective heat transfer law and generalized radiative heat transfer law. In the refrigeration cycle model the only irreversibility of finite rate heat transfer is considered. The optimal relation between cooling load and coefficient of performance (COP) of the refrigeration cycle is also derived by using an equivalent temperature of low-temperature source. The obtained results include those with various heat transfer laws and infinite low-temperature source, and can provide some theoretical guidelines for the designs of practical refrigerators.