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Aims and Scope
Editorial Board

1. CFD model of air movement in ventilated façade: comparison between natural and forced air flow

Miguel Mora Pérez, Gonzalo López Patiño, P. Amparo López Jiménez

Hydraulic and Environmental Engineering Department, Universitat Politècnica de Valencia, Spain.

Abstract: This study describes computational fluid dynamics (CFD) modeling of ventilated façade. Ventilated façades are normal façade but it has an extra channel between the concrete wall and the (double skin) façade. Several studies found in the literature are carried out with CFD simulations about the behavior of the thermodynamic phenomena of the double skin façades systems. These studies conclude that the presence of the air gap in the ventilated façade affects the temperature in the building skin, causing a cooling effect, at least in low-rise buildings. One of the most important factors affecting the thermal effects of ventilated façades is the wind velocity. In this contribution, a CFD analysis applied on two different velocity assumptions for air movement in the air gap of a ventilated façade is presented. A comparison is proposed considering natural wind induced velocity with forced fan induced velocity in the gap. Finally, comparing temperatures in the building skin, the differences between both solutions are described determining that, related to the considered boundary conditions, there is a maximum height in which the thermal effect of the induced flow is significantly observed.

Volume 4, Issue 3, 2013, pp.357-368.

2. Experimental study of relative permittivity of atmospheric ice

Shravan K. Bhattu, Umair N. Mughal, Muhammad S. Virk

Department of Technology, Narvik University College, 8505 Narvik, Norway.

Abstract: Atmospheric icing on onshore and offshore structures is problematic, if we don’t detect and remove it. Despite of various ice detection techniques, capacitor based ice sensing technique is interesting one, as it is based on dielectric properties of material. This technique of measuring icing event is simple and cost-effective. Based on the dielectric concept, an experimental setup comprised of two rectangular aluminum bars in parallel connected with an LCR meter, thermocouples, data acquisition system and computer was designed at the cold room chamber facility of Narvik University College to study the transient response of dielectric constant of ice at different operating atmospheric conditions. Analysis showed that depending on the atmospheric ice type the capacitance varies due to the variation in temperature.

3. Cooling load optimization of an irreversible refrigerator with combined heat transfer

M. El Haj Assad

Aalto University School of Science and Technology, Department of Energy Technology, P. O. Box 14100, 00076 Aalto, Finland.

Abstract: In this work a mathematical model to study the performance of an irreversible refrigerator has been presented with the consideration of heat exchange by combined convection and radiation. The external irreversibility effects due to finite rate heat transfer as well as the effects of internal dissipations have been considered in the analysis. The relation between the cooling load and the coefficient of performance of the refrigerator has been derived. Furthermore an expression for the maximum cooling rate has been derived. The parameters that affect the cooling load have been investigated. The cooling load has been discussed and the effect of internal irreversibility has been investigated.

4. Numerical simulation and optimization of CO₂ sequestration in saline aquifers for enhanced storage capacity and secured sequestration

Zheming Zhang, Ramesh K. Agarwal

Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, MO 63130, USA.

Abstract: Saline aquifer geological carbon sequestration (SAGCS) is considered most attractive among other options for geological carbon sequestration (GCS) due to its huge sequestration capacity. However, in order to fully exploit its potential, efficient injection strategies need to be investigated for enhancing the storage efficiency and safety along with economic feasibility. In our previous work, we have developed a new hybrid code by integration of the multi-phase CFD simulator TOUGH2 with a genetic algorithm (GA) optimizer, designated as GA-TOUGH2. This paper presents the application of GA-TOUGH2 on two optimization problems: (a) design of an optimal water-alternating-gas (WAG) injection scheme for a vertical injector in a generic aquifer and (b) the design of an optimal injection pressure management scheme for a horizontal injector in a generic aquifer to optimize its storage efficiency. The optimization results for both applications are promising in achieving the desired objectives of enhancing the storage efficiency significantly while reducing the plume migration, brine movement and pressure impact. The results also demonstrate that the GA-TOUGH2 code holds a great promise in studying a host of other problems in CO₂ sequestration such as how to optimally accelerate the capillary trapping, accelerate the dissolution of CO₂ in water or brine, and immobilize the CO₂ plume.

5. University buildings in Greece: Energy analysis of heating and cooling demand

Apostolos Michopoulos, Vassiliki Voulgari, Nikolas Kyriakis

Process Equipment Design Laboratory, Mechanical Engineering Department, Aristotle University of Thessaloniki – POB 487 – 541 24 Thessaloniki – Greece.

Abstract: The paper presents the energy analysis results of 10 University building blocks, confirmed by in-situ recordings. The results prove that the University buildings present a significant potential for energy consumption reduction, behaving differently than the other constructions of the non-residential sector. Energy consumption and environmental behavior indices are reported for the specific building category, in an attempt to fill the existing gap in the literature.

6. Radiological risk assessment for Al-Twuaitha nuclear site in Iraq

Abdul Hameed M. J. Al Obaidy¹, Bashair AR Mohammed², Hisham M.J. Al Sharaa³

1 Environmental Research Center, University of Technology, Baghdad, Iraq.

2 Department of Physics, College of Science, University of Baghdad, Baghdad, Iraq.

3 Geomatic Engineering Division, University of Technology, Baghdad, Iraq.

Abstract: In this paper, the contamination level of U, ¹³⁷Cs, ⁶⁰Co, ⁴⁰K and ⁹⁰Sr from different soil samples of the destroyed nuclear reactor at Al-Tuwaitha site south of Baghdad investigated and four contaminated spots identified. The obtained values of the ⁴⁰K in soil samples are within normal concentration values and close to the environmental levels. The skewness coefficient for the U series,¹³⁷Cs and ⁶⁰Co distribution indicates asymmetric distribution tailing slightly towards higher concentration. However, the activity of U series, ¹³⁷Cs, ⁶⁰Co and ⁹⁰Sr in the soil samples exhibit higher variability and above the regulated environmental levels.

7. Development of DMC controllers for temperature control of a room deploying the displacement ventilation HVAC system

Zhicheng Li¹, Ramesh K. Agarwal¹, Huijun Gao²

1 Department of Mechanical Engineering and Materials Science, Washington University in Saint Louis, MO 63130, USA.

2 Research Institute of Intelligent Control and Systems, Harbin Institute of Technology, Harbin 150001, China.

Abstract: In this paper, by developing a new Dynamic Matrix Control (DMC) method, we develop a controller for temperature control of a room cooled by a displacement ventilation HVAC system. The fluid flow and heat transfer inside the room are calculated by solving the Reynolds-Averaged Navier-Stokes (RANS) equations including the effects of buoyancy in conjunction with a two-equation realizable k - epsilon turbulence model. Thus the physical environment is represented by a nonlinear system of partial differential equations. The system also has a large time delay because of the slowness of the heat exchange. The goal of the paper is to develop a controller that will maintain the temperature at three points near three different walls in a room within the specified upper and lower bounds. In order to solve this temperature control problem at three different points in the room, we develop a special DMC method. The results show that the newly developed DMC controller is an effective controller to maintain temperature within desired bounds at multiple points in the room and also saves energy when compared to other controllers. This DMC method can also be employed to develop controllers for other HVAC systems such as the overhead VAV (Variable Air Volume) system and the radiant cooling hydronic system.

8. Modeling and verification of hemispherical solar still using ANSYS CFD

Hitesh N. Panchal ¹, P. K. Shah ²

1 KSV University, Gujarat Power Engineering and Research Institute, Mehsana, India.

2 Silver Oak College of Engineering and Technology, Ahmedabad, Gujarat, India.

Abstract: In every efficient solar still design, water temperature, vapor temperature and distillate output, and difference between water temperature and inner glass cover temperatures are very important. Here, two dimensional three phase model of hemispherical solar still is made for evaporation as well as condensation process in ANSYS CFD. Simulation results like water temperature, vapor temperature, distillate output compared with actual experimental results of climate conditions of Mehsana (latitude of 23° 59’ and longitude of 72° 38) of hemispherical solar still. Water temperature and distillate output were good agreement with actual experimental results. Study shows that ANSYS-CFD is very powerful as well as efficient tool for design, comparison purpose of hemispherical solar still.

9. Alternative solvents for post combustion carbon capture

Udara S. P. R. Arachchige¹, Morten C. Melaaen^1,2

1 Telemark University College, Porsgrunn, Norway.

2 Tel-Tek, Porsgrunn, Norway.

Abstract: The process model of post combustion chemical absorption is developed in Aspen Plus for both coal and gas fired power plant flue gas treating. The re-boiler energy requirement is considered as the most important factor to be optimized. Two types of solvents, mono-ethylamine (MEA) and di-ethylamine (DEA), are used to implement the model for three different efficiencies. The re-boiler energy requirement for regeneration process is calculated. Temperature and concentration profiles in absorption column are analyzed to understand the model behavior. Re-boiler energy requirement is considerably lower for DEA than MEA as well as impact of corrosion also less in DEA. Therefore, DEA can be recommended as a better solvent for post combustion process for carbon capture plants in fossil fuel fired power industries.

10. Studies on biomethanation of water hyacinth (eichhornia crassipes) using biocatalyst

Santanu Sarkar¹, Saikat Banerjee²

1 Department of Chemical Engineering, Jadavpur University, Kolkata-700032 (WB), India.

2 Department of Chemical Engineering, Salalah College of Technology, Salalah, Sultanate of Oman.

Abstract: Water hyacinth is a huge source of biomass in tropical countries. That can be used for biogas production. The aim of this conversion process is to improve the quality, specific energy content, transportability, etc. of the raw biomass source or to capture gases which are naturally produced as biomass is micro biologically degraded. An experimental study on catalytic biomethanation of Water Hyacinth has been carried out in a semi batch digester at different substrate concentration using cow urine as an organic catalyst under controlled pH with in the range of 6.9 to 7.2. The rate of bio gas production varies with different conditions and parameters like temperature, stirring speed, feed concentration, catalyst concentration, etc. It has been found that the catalyst mainly increases the production rate of biogas from water hyacinth. Mathematical analysis of the experimental data on catalytic biomethanation has been done in the present study. Mathematical equations relating maximum specific growth rate and kinetic parameter at different substrate and catalyst concentration have been developed.

11. Thermal resistances of air in cavity walls and their effect upon the thermal insulation performance

S. M. A. Bekkouche¹, T. Benouaz², M. K. Cherier¹, M. Hamdani¹, M.R. Yaiche³, N. Benamrane¹

1 Application of Renewable Energies in Arid and Semi Arid Environments /Applied Research Unit on Renewable Energies/ EPST Development Center of Renewable Energies, URAER & B.P. 88, ZI, Gart Taam Ghardaïa, Algeria.

2 University of Tlemcen, BP. 119, Tlemcen R.p. 13000, Algeria.

3 Development Center of Renewable Energies, CDER & B.P 62, 16340, Route de l'Observatoire, Bouzaréah, Algiers, Algeria.

Abstract: The optimum thickness in cavity walls in buildings is determined under steady conditions; the heat transfer has been calculated according to ISO 15099:2003. Two forms of masonry units are investigated to conclude the advantage of high thermal emissivity. The paper presents also some results from a study of the thermal insulation performance of air cavities bounded by thin reflective material layer "ε = 0.05". The results show that the most economical cavity configuration depends on the thermal emissivity and the insulation material used.

12. Energy and exergy analysis of a two pass photovoltaic –thermal (PV/T) air heater

M. Srinivas, S. Jayaraj

Department of Mechanical Engineering, National Institute of Technology, Calicut-673601, India.

Abstract: A double pass hybrid solar air (PV/T) heater with slats is designed and fabricated to study elaborately its thermal and electrical performance corresponding to the warm and humid environment. Air as a heat removing fluid is made to flow through upper and lower channels of the collector. The collector is designed in such way that the absorber plate is partially covered by solar cells. Thin metallic strips (called slats) are attached longitudinally at the bottom side of the absorber plate to improve the overall system performance (by increasing the cooling rate of the absorber plate). Thermal and electrical performances of the whole system at different cooling rates are presented. The exergy analysis of double pass hybrid solar air (PV/T) heater with slats has also been carried out. The instantaneous overall energy and overall exergy efficiency of the double pass hybrid (PV/T) solar air heater varies between 29 – 37 percent and 14-17 percent respectively. These obtained values are comparable with that of published results.

13. Impacts of environmental degradation and climate change on electricity generation in Malawi

Chiyembekezo S. Kaunda¹, Felix Mtalo²

1 Department of Energy and Process Engineering – WaterPower Laboratory, Norway University of Science and Technology, Trondheim NO-7491, Norway.

2 Department of Water Resources Engineering, University of Dar es Salaam, P.O. Box 35031, Dar es Salaam, Tanzania.

Abstract: Hydropower is an important energy source in Malawi because it provides almost all of the country’s electricity generation capacity. This paper has reviewed the impacts of environmental degradation and climate change on hydropower generation in Malawi. Energy scenario and other issues that contribute towards the current state of environment have been discussed. All of Malawi’s hydropower stations are run-of-river schemes cascaded along the Shire River with an installed capacity of nearly 280 MW. The generation is impacted negatively by floods, siltation, droughts and aquatic weeds infestation. The way how these challenges are being exacerbated by the poor state of the environment, especially within the Shire River basin in particular is also discussed in the paper. Measures taken by the national electricity utility company on how to manage the impacts are discussed as well. The paper concludes that hydropower generation system in a highly environmental degraded area is difficult to manage both technically and economically. In the case of Malawi, diversifying to other energy sources of generating electricity is considered to be a viable option. Some mitigation measures concerning environment degradation and climate change challenges have been suggested in the paper.

14. Effect of hydrogen-diesel combustion on the performance and combustion parameters of a dual fuelled diesel engine

P. K. Bose, Rahul Banerjee, Madhujit Deb

Mechanical Engineering Department, National Institute of Technology, Agartala, Tripura-799055, India.

Abstract: Petroleum crude is expected to remain main source of transport fuels at least for the next 20 to 30 years. The petroleum crude reserves however, are declining and consumption of transport fuels particularly in the developing countries is increasing at high rates. Severe shortage of liquid fuels derived from petroleum may be faced in the second half of this century. In this paper, experiments are performed in a fur stroke, single cylinder, compression ignition diesel engine with dual fuel mode. Diesel and hydrogen are used as pilot liquid and primary gaseous fuel, respectively. The objective of this study is to find out the effects on combustion and performance parameters observed at diesel hydrogen fuel mixture for all the different loadings (2kg,4kg,6kg,8kg,10kg and 12kg) in the engine.

15. Modeling GHG emission and energy consumption in selected greenhouses in Iran

M. Yousefi, M. Omid, SH. Rafiee, B. Khoshnevisan

Department of Agricultural Machinery Engineering, Faculty of Agricultural Engineering and Technology, University of Tehran, Karaj, Iran.

Abstract: It is crucial to determine energy efficiency and environmental effects of greenhouse productions. Such study can be a viable solution in probing challenges and existing defects. The aims of this study were to analyze energy consumption and greenhouse gas (GHG) emissions for pepper production using biological method inside greenhouses which used natural gas (NG) heating system in Esfahan province. Data were collected from 22 greenhouse holders using a face to face questionnaire method, in 2010-2011. Also, functional area was selected 1000 m2. Total energy input, total energy output, energy ratio, energy productivity, specific energy, net energy gain and total GHG emissions were calculated as 297799.9 MJ area-1, 3851.84 MJ area-1, 0.013, 0.016 kg MJ-1, 61.85 MJ kg-1, -293948 MJ area-1 and 14390.85 kg CO₂ equivalent area-1, respectively. Result revealed that replacing diesel fuel with NG will not be an effective way of reducing energy consumption for greenhouse production. However, it is crucial to focus on energy management in order to enhance the energy and environmental indices. One way to supply adequate input energy and a reduction in GHG emissions is the utilization of renewable and clean energy sources instead of NG and diesel fuel. Also, it is suggested to adopt solar greenhouses in the region and to supply electricity from non-fossil sources seriously.

16. An investigation of heat transfer augmentation and friction characteristics in solar air heater duct with V-shaped wire as artificial roughness on absorber plate

Madhukeshwara N.¹, E. S. Prakash²

1 Department of Mechanical Engineering, B.I.E.T, Davanagere, Karnataka, India.

2 Department of Studies in Mechanical Engineering, U.B.D.T.C.E, Davanagere, Karnataka, India.

Abstract: An experimental investigation of heat transfer augmentation and friction characteristics of fully developed turbulent flow in a rectangular duct of solar air heater with absorber plate having V-shaped wire ribs as artificial roughness on its underside is carried out. The investigation covers wide range of different parameters of wire ribbed roughness: relative roughness pitch (p/e) from 10 to 40, relative roughness height (e/Dh) from 0.01 to 0.04 and angle of attack of flow (α) from 20° to 90°. Duct aspect ratio (W/B) is kept 5 and Reynolds number (Re) is varied from 2,500 to 8,500. The heat transfer and friction factor values obtained are compared with those of smooth duct under similar flow conditions. Expressions are developed for Nusselt number and friction factor for the roughness geometry. Enhancement of Nusselt number and friction factor for roughened duct are 1.5 and 2.7 times of smooth duct respectively.