322,969 research outputs found
4E analysis of a modified multigeneration system designed for power, heating/cooling, and water desalination
No full textMultigeneration systems, owing to their efficient fuel utilization, are recognized as one of the best technical and economical methods of energy saving and climate control. In this paper, a multigeneration system is proposed for the production of power, heating/cooling, and desalinated water. The proposed system was first studied by means of an energy, exergy, exergoeconomic, and environmental analyses and the obtained results were compared with that of multigeneration systems described in the literature (the selected multigeneration systems are based on a gas turbine cycle as prime mover). In addition, a parametric study was used to investigate the effects of primary thermodynamic quantities such as air pre-heater outlet temperature, pinch-point temperature difference in evaporator, evaporator temperature of cooling cycle, and evaporator temperature of desalination system on cycle performance. Results indicated that the proposed cycle's power, heating, cooling, and desalinated water production is 30.5 MW, 40.8 MW, 1 MW, and 0.364 kg/s, respectively. In addition, the cycle's total cost and total CO2 emissions are 1943.5 $/h and 0.163 kg/kWh. The parametric survey showed that the air pre-heater outlet temperature and the gas turbine inlet temperature are the most influential parameters in changing the system's CO2 emissions. In this way, an increase of the pre-heater outlet temperature causes a 26% reduction in the cycle's CO2 emissions, whereas an increase of the gas turbine inlet temperature leads to a 53% increase in CO2 emissions
Fame bias in editorial choice: Yes or No?
No full textRecently, Scientometrics has published a paper titled “Is there bias in editorial choice? Yes” (Moustafa 2015) in which some comments are given on our published paper in Nature titled “Is there fame bias in editorial choice?” (Mahian et al. 2015). Unfortunately, the author of above mentioned paper and many other readers might misunderstand the main aim of our correspondence. Here, we try to give some explanations to clarify the main goal of analysis presented in the paper
Optimization of a solar air heater with phase change materials: Experimental and numerical study
No full textIn this paper, a solar air heater (SAH) with phase change material (PCM)-based energy storage is investigated. Paraffin was placed underneath the absorber plate as the PCM. A transient two-dimensional laminar model was used in the Ansys Fluent 17 software to study the effects of different parameters on the performance of the SAH, such as the air mass flow rate, the amount of paraffin, and the thermal conductivity of the paraffin. The performance of the SAH was optimized by considering two objectives simultaneously: thermal energy efficiency and maximum nocturnal temperature difference between the inlet and the outlet of the SAH. To validate the numerical model, a SAH with a 2-cm paraffin layer and the same dimensions as the numerical model was built and tested. The results of the simulation showed good agreement with the experimental results.
Multi-objective optimization of a proposed multi-generation cycle based on Pareto diagrams: Performance improvement, cost reduction, and CO2 emissions
No full textEnergy system optimization is a significant task aimed at optimizing system operations and reducing costs and emissions. In this paper, an energy system is presented for multi-energy generation of power, heating/cooling, and desalination. First, the cycle's exergy, exergoeconomics, and environmental impact are analyzed. Then, optimization is performed using MATLAB software by applying a genetic algorithm (GA) and adopting 10 design parameters with two objective functions. The goal of optimization is to find the design variable values based on a Pareto plot that will increase the exergy efficiency while reducing cost and CO2 emissions. Scatter plots of the decision variables for the population indicate that objective functions can be optimized. Optimal values for the objective functions can be found by selecting lower values for the heat exchanger and evaporator's pinch-point temperature differences and higher values for the compressor pressure ratio, inlet temperature of the gas turbine (GT), isentropic efficiencies of air compressor (AC) and GT, and temperature of Rankine cycle evaporator. After optimization, exergy efficiency increased around 8.4%, cost dropped 14.8%, CO2 emissions were reduced by 1.2%, and the production of desalinated water increased about 7.6% using the proposed cycle. At the end of work, the influences of design variables on CO2 emissions as well as the total cycle cost are investigated in a parametric study
Natural convection of Al2O3/ water nanofluid in a square cavity: effects of heterogeneous heating
No full textIn this paper, the natural convection in a square cavity filled with Al2O3/water nanofluid has been investigated.
The flow and heat transfer characteristics of the nanofluid in the cavity are documented when
bottom wall is under heterogeneous heating, the right wall is considered cold while the top and left walls
are adiabatic. Nine different cases are considered for the non-uniform heat flux where the total heat flux
applied to the cavity is the same for all the cases in magnitude but the profile is different. For different
values of Rayleigh numbers (103–106), nanoparticle volume fractions (0–9%), and aspect ratios, the optimal
profile of heat flux is determined in which Nusselt number is maximized. It is found that the trend of
Nusselt number is different for the nine cases at Ra = 103 where the conduction is the dominant phenomenon.
The results also reveal that for high values of Rayleigh number, i.e. 106, the Nusselt number is minimized
where the heat flux in the vicinity of adiabatic wall is smallest while the heat flux near the cold
wall is biggest
Nucleate pool boiling heat transfer correlation for TiO 2-water nanofluids
No full textThis paper is a continuation of the authors' previous work on the nucleate pool boiling heat transfer of nanofluids [Suriyawong, A. and Wongwises, S., "Nucleate pool boiling heat transfer characteristics of TiO2-water nanofluids at very low concentrations," Exp. Therm. Fluid Sci., Vol. 34, No. 8, 2010, pp. 992-999.] This study presents new correlation for predicting heat transfer coefficient for nucleate pool boiling of TiO 2-water nanofluids at several low concentrations. Unlike most previous studies, the proposed correlation consists of various relevant factors. Two horizontal circular plates made from copper and aluminum with different surface roughness values are used as heating surfaces. Because the calculation concerns with properties of nanofluids, this research uses various correlations from previous studies to find the properties of nanofluids and the best one is selected for the presentation. Compared with measured data of nucleate pool boiling of water and nanofluids from present and previous studies, it was found that the developed correlation could be used for prediction at a certain level. Copyright © 2012 by ASTM International
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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