Cover

Aims and Scope
Editorial Board

1. A green supply chain network design model for enhancing competitiveness and sustainability of companies in high north arctic regions

Hao Yu¹, Wei Deng Solvang¹, Chen Chen²

1 Department of Industrial Engineering, Narvik University College, Postboks 385 Lodve gate 2, NO-8505 Narvik, Norway.

2 Northern Research Institute Narvik AS.Postboks 250, NO-8504 Narvik, Norway.

Abstract: To survive in today’s competitive and ever-changing marketplace, companies need not only to engage in their products and/or services, but also to focus on the management of the whole supply chain. Effectively managing and balancing the profitability and interconnection of each player in the supply chain will improve the overall supply chain surplus as well as individual profit. However, it is extremely difficult to simultaneously optimize several objectives in design and planning of a supply chain, i.e., cost-minimization, risk-minimization, responsiveness-maximization, etc., which are somehow conflict with one another. Furthermore, the natural and infrastructural challenges in high north arctic regions make it become much more difficult and complicated to design and develop cost-efficient, highly responsive, environmentally friendly, and sustainable supply chain network. In order to provide companies in high north arctic regions with decision support tool for the design and planning of theirs supply chain networks, a green supply chain network design (GrSCND) model is formulated in this study based on multi-objective mixed integer programming (MIP). The optimal trade-off among several conflicting objectives is the focus of this GrSCND model aiming to enhance both competitive competence and sustainability of companies and supply chains operated in high north regions. In addition, a numerical experiment is also given to present a deep insight of the GrSCND model.

Volume 5, Issue 4, 2014, pp.403-418.

2. Experimental analysis of airtightness and estimation of building air infiltration using two different single zone air infiltration models

Tijo Joseph, Animesh Dutta

School of Engineering, University of Guelph, Guelph, Ontario, Canada.

Abstract: Building air leakage can contribute significantly to the energy consumption of a building. This paper presents the airtightness performance of a campus building located in Ontario, Canada. The air leakage rate through the building envelope was measured under stilted depressurization conditions following the ASTM E-779 standardized test method. With this test derived empirical leakage flow co-efficient and leakage flow exponent measures, the air infiltration rate for the building under varying wind and outside temperature conditions was calculated using two different single zone air infiltration models – the Lawrence Berkeley Laboratory model and the Alberta Air Infiltration model thus also allowing for a comparison of the results between the two mathematical models.

3. Biogas purification using membrane micro-aeration: A mass transfer analysis

Wathsala Perera¹, Deshai Botheju², Rune Bakke^1,3

1 Telemark University College, Porsgrunn, Norway.

2 Agility Group AS, Sandefjord, Norway.

3 Tel-Tek, Porsgrunn, Norway.

Abstract: When sulfur containing organic feedstocks undergo anaerobic digestion, sulfides are formed due to the biological activities of sulfur reducing bacteria. Presence of hydrogen sulfide (H2S) negatively affects the usage of biogas and needs to be reduced to levels that depend on the intended biogas application. Conversion of sulfide to its oxidized forms can be carried out by aerobic chemolithotrophic bacteria consuming oxygen as the electron acceptor. Membrane micro-aeration is a recently developed reliable method of safely supplying oxygen into anaerobic digesters. In this study, mass transfer models are developed to represent diffusion and back diffusion of gases through tubular polydimethylsiloxane (PDMS) membranes. The models are utilized to determine the required membrane area and length in order to supply the stoichiometric amount of oxygen for biologically oxidizing a given amount of sulfide feed into elemental sulfur. Penetration of oxygen and nitrogen into the digester and transfer of methane, carbon dioxide and hydrogen sulfide back into the membrane tube are analyzed using these mass transfer models. Circulating air or aerated water inside the membrane tube is considered as two alternatives for supplying micro-aeration to the digester. Literature digester performance and sulfide data are used for example calculations. The required membrane length depends on circulating water flow rates and dissolved oxygen concentrations when water is used inside the membrane. A considerable fraction of CO2 can also be removed from the biogas in this case. Circulating air inside the membrane is, however, more promising solution as it requires much less membrane area and thereby also causes insignificant methane loss. The proposed membrane micro-aeration technique cuts N2 biogas dilution in half compared to direct air purging for in-situ sulfide oxidation.

4. Assessment of wind resources in Braşov region (Romania)

E. Eftimie¹, N. Eftimie²

1 Department of Product Design, Mechatronics and Environment, Transilvania University of Braşov, Eroilor 29, 500036, Romania.

2 Department of Manufacturing Engineering, Transilvania University of Braşov, Eroilor 29, 500036, Romania.

Abstract: The accurate assessment of wind potential for an area requires both the knowledge of probability density function and the power density of wind. For this purpose, for the area of interest are required databases that to contain direct measurements of wind parameters recorded during at least one year. In order to model the wind speed, Weibull distribution is used. However, the use of Weibull distribution is most often difficult due to the need of knowing the Weibull distribution parameters (the shape parameter and the scale parameter). Considering this aspect, this paper proposes a method for estimating the Weibull parameters using their dependence on the Gamma function. The exemplification is made through a case study, by processing of data recorded by two weather stations located in two different areas of Braşov. The proposed algorithm is a method easily to apply to any location that has a secure database.

5. Feasibility investigation and combustion enhancement of a new burner functioning with pulverized solid olive waste

Bounaouara H.^1,2, Sautet J.C.¹, Ben Ticha H.², Mhimid A.²

1 CORIA UMR 6614 CNRS, Université et INSA de ROUEN, Avenue de l’Université, BP 12, 76801 Saint Etienne du Rouvray, Cedex, France.

2 LESTE, Ecole Nationale d’Ingénieurs de Monastir, 5019 Monastir, Tunisie.

Abstract: This article describes an experimental study on solid olive residue (olive cake) combustion in form of pulverized jet. This is a contribution to the valorization of olive residue as a source of renewable energy available in the majority of mediterranean countries. A sample of olive cake from Tunisian origin is prepared for the experiment; this sample is crushed, dried and sifted in order to obtain the desired particles form. A new burner made up of a coaxial cylindrical tube is especially designed and fabricated. In order to start the combustion of olive cake and maintain the main flame, two types of pilot flame were used: a central premixed flame of methane/oxygen and an annular diffusion flame of methane. This paper shows the conditions for an efficient olive cake burner operation in free air. The effects of particle size and pilot flame position have been discussed. The olive cake combustion is possible only with particles at a size below 200 μm. Moreover, the combustion maintained by the annular pilot flame ensures better burning conditions than the central pilot flame. Finally, the inserted preheating system has improved the olive cake combustion.

6. Control of temperature and energy consumption in buildings - A review

D.W.U. Perera, C. F. Pfeiffer, N.-O Skeie

Faculty of Technology, Telemark University College, Porsgrunn, Norway.

Abstract: Building sector is one of the largest energy consumers in the world and currently it utilizes 40% of the total energy in the European Union. At the beginning of the article, energy crisis related to the buildings is defined with regard to occupant thermal comfort, energy savings and temperature control. Subsequently, a brief presentation of various types of building heating models available for control purposes is given. Afterward, different approaches used for controlling the building thermal comfort and the energy consumption are shown. These strategies are primarily, classical control, advanced control, intelligent control and hybrid control. The proposed survey also provides up-to-date applications of control techniques. The overview hence affords an insight into current control systems used for temperature and energy consumption in buildings. Further, it helps to have a comprehensive understanding about the variety of control techniques in the field of HVAC (Heating, Ventilation and Air conditioning) applications, at the same time delivering information for careful design of suitable controllers.

7. Development a new equation of polarization curve for a proton exchange membrane fuel cell at different channel geometry

I. Khazaee

Department of Mechanical Engineering, Torbat-e-jam branch, Islamic Azad University, Torbat-e-jam, Iran.

Abstract: The polarization curve of a proton exchange membrane fuel cell is an important parameter that is used to investigate the performance of it that is expressed with the Nernst equation with the equation of losses the voltage such as activation loss, ohmic loss and concentration loss that they are a function of temperature of the cell and the current density. In this study a new correlation for polarization curve is obtained that it is a function of temperature, current density and a new parameter of cross-section geometry of channels. For this purpose three PEM fuel cells with different channels geometry of rectangular, elliptical and triangular have constructed. The active area of each cell is  that its weight is 1300gr. The material of the gas diffusion layer is Carbon clothes, the membrane is nafion112 and the catalyst layer is a plane with 0.004 gr/cm2 Platinum. Also a test bench designed and constructed for testing the cell and a series of experiments are carried out to investigate the influence of the geometry of the cell on performance of the cell. The results show that when the geometry of channel is rectangular the performance of the cell is better than the triangular and elliptical channel.

8. Experimental investigation and comparison of heat transfer coefficient of a two phase closed thermosyphon

I. Khazaee

Faculty of Mechanical and Energy Engineering, Shahid Beheshti University, A.C., Tehran, Iran.

Abstract: In this study, we investigated and reviewed the heat transfer equations of the evaporator and condenser of a two phase closed Thermosyphon as well as the differences between this equations for a working fluid and different conditions. The heat transfer limits of a two phase closed thermosyphon such as sonic, flooding (or entrainment) dry-out and boiling are investigated . A good agreement is observed between analytical results of this study and the analytical and experimental results of those available in the open literature. The heat transfer limits are very important in thermosyphons and have to be calculated accurately while the input heat must be lower than the heat transfer limits for the operations of thermosyphon without any problem. Also by using the experimental results a semi empirical equation for heat transfer coefficient of evaporator was proposed.

9. CFD study of a twisted blade H-Darrieus wind turbine

Rajat Gupta, Rituraj Gautam, Siddhartha Sankar Deka

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

Abstract: In this paper, a two-dimensional Computational Fluid Dynamics (CFD) study of the performance of a H-Darrieus turbine with three twisted blade had been carried out. The chord length of each blade is 5cm and the blade height is considered to be same for all the rotors. A two dimensional (2D) model of the turbine was designed in CATIA V5R19 software and a k-epsilon turbulence closure was adopted with the unstructured mesh generated around the rotor modeled in GAMBIT 2.3.16. The inlet velocities and the rotational speeds are taken from the experimental results and the CFD analysis was carried out in CFD Code-FLUENT 6.3.26. From the CFD analysis, power coefficient (Cp) and torque coefficient (Ct) at three different H/D ratios of 1.13, 1.31 and 1.55 respectively were calculated and compared with available experimental results. The computational analysis showed that the highest values of Cp (0.525) and Ct (0.95) were obtained at H/D ratios of 1.31 and 1.13 respectively. The deviation of computational Cp from experimental Cp was within ±3.08 % and that of computational Ct from experimental Ct was within ±1.106 %. A study of the flow behaviour around the rotor was also carried out using the pressure contours and velocity vectors plots. A maximum pressure drop is obtained for H/D ratio of 1.31 and a vortex reattachment near rear blade of rotor with H/D ratio of 1.31 was observed from the pressure contours and velocity vectors plots. The vortex attachment to the blade of the rotor enhances the lift coefficient of the rotor which helps in improving the power coefficient of the rotor. The comparison between the computational results and previous experimental work is pretty encouraging.

10. Performance of single and multiple pressure wind catchers in terms of air flow changes

M. R. Abouseba¹, J. Khodakarami²

1 Sepehr Institute of Isfahan, Isfahan, Iran.

2 Engineering Department, Ilam University, Ilam, Iran.

Abstract: Although air current is the major cause of flow inside the wind catcher networks, the effect of wind direction changes on the performance of different types of wind catchers is unknown yet. Therefore, present paper aims at creating desirable conditions for comparing single-pressure and multiple-pressure types of wind catchers in order to discover the effect of wind direction changes on the performance of each type of wind catchers. To this end, The CFD model is devised for both types exposed to wind blowing at the speed of 3 m/s and at the angles of 0, 45, 90, 135, and 180 degrees. The obtained results indicated that the type of high-pressure area against the cage inflow determined the direction of wind inside their networks. Despite of this fact, during every blow towards the single-pressure type only one flow was generated whereas in multi-pressure type both downward and upward flows were generated. Moreover, while in the single-pressure types only the high-pressure area in front of the inflow was been used, in the multiple-pressure-type the entire high-pressure area around the cage was been practically in used.