Buoyant heat transport in fluids across tilted square cavities discretely heated at one side

Laminar natural convection heat transfer inside fluid-filled, tilted square cavities cooled at one side and partially heated at the opposite side, is studied numerically. A computational code based on the SIMPLE-C algorithm is used for the solution of the system of mass, momentum, and energy transfer equations. Simulations are performed for a complete range of heater sizes and locations, Rayleigh numbers based on the side of the cavity from 10³ to 10⁷, Prandtl numbers from 0.7 to 700, and tilting angles of the enclosure from ?75° to +75°, where negative angles correspond to configurations with the heater facing downwards. It is found that the heat transfer rate increases with increasing the Rayleigh and Prandtl numbers, and the size of the heater. In addition, for negative inclinations of the enclosure the amount of heat exchanged decreases with increasing the tilting angle, while for positive inclinations the heat transfer rate either increases or decreases according as the heater is located toward the top or the bottom of the cavity. Finally, as far as the heater location is specifically concerned, the heat transfer performance has a peak for intermediate positions, the higher are the Rayleigh and Prandtl numbers, as well as the tilting angle for positive inclinations, the closer to the bottom of the cavity is the optimum heater location for maximum heat removal.     

Economic and environmental benefits of landfill gas from municipal solid waste in Malaysia

Discharge of Green House Gases (GHGs) and the management of municipal solid waste (MSW) continue to be a major challenge particularly in growing economies. However, these are resources which can be converted to green energy. Landfill gas which is essentially methane (50–55%) and carbon dioxide (40–45%) (both GHGs) is released from MSW by biodegradation processes. The estimation of this methane and its economic and environmental benefits for environmental sustainability are the objectives of this study. Methane emission from MSW disposed of in landfills was estimated using Intergovernmental Panel on Climate Change (IPCC) methodology. From the study, based on 8,196,000 tonnes MSW generated in Peninsular Malaysia in 2010, anthropogenic methane emission of about 310,220 tonnes per year was estimated. This was estimated to generate 1.9 billion kWh of electricity year^?1 worth over RM 570 million (US$190 million). In addition, this leads to carbon dioxide reduction of 6,514,620 tonnes year^?1 equivalent to carbon credit of over RM 257 million (US$85 million). These results were also projected for 2015 and 2020 and the outcomes are promising. Therefore, the exploration of this resource, besides the economic benefits helps in reducing the dependence on the depleting fossil fuel and hence broadening the fuel base of the country.     

The Synthesis and Evaluation of Some New Quinazolones as Antioxidant Additives for Egyptian Lubricating Oils

4-(4-oxo-4H-benzo[d][1,3]oxazin-2-yl)phenyl-4-methylbenzenesulfonate 2 was prepared and reacted with some nitrogen and sulfur nucleophiles. The prepared products were evaluated as antioxidant and corrosion inhibitors for gasoline lubricating oil in which compounds, 4-(3-amino-4-oxo-3,4-dihydroquinazolin-2-yl)phenyl-4-methylbenzene sulfonate 12, 4-(3-(3-chloro-2-oxo-4-phenylazetidin-1-yl)-4-oxo-3,4-dihydroquinazolin-2-yl)phenyl 4-methylbenzenesulfonate 14, 4-(4-oxo-3-(4-oxo-2-phenylthiazolidin-3-yl)-3,4-dihydroquinazolin-2-yl)phenyl 4-methylbenzenesulfonate 15, and 4-(3-(1,3-dioxoisoindolin-2-yl)-4-oxo-3,4-dihydroquinazolin-2-yl)phenyl 4-methylbenzenesulfonate 18 exhibited the highest antioxidant activity. It was interesting also to study the effect of concentration of additive 15 to find the optimum concentration recommended to be used, 0.1 g for 1 L oil of additive 15 was the more effective concentration to be used. Also, measurements of thermal analyses were carried out.     

Synthesis of Some Novel Antioxidant and Anticorrosive Additives for Egyptian Lubricating Oils

Abstract

The starting oxazolone 1 was reacted with p-aminophenol in glacial acetic acid to afford imidazolone 2, which afforded Mannich base 3 via the reaction with piperidine and paraformaldehyde. Moreover, the reaction of 2 with ethylchloroacetate or chloroacetic acid in dry acetone gave the corresponding imidazolones 4 and 5, respectively. Compound 4 reacted with benzylamine or 4-chlorobenzaldehyde to furnish 6 and 7, respectively. On the other hand, oxazolone 1 reacted with hydrazines in glacial acetic acid to afford the 1,2,4-triazines 11–15. Representative compounds of the synthesized products were established and evaluated as antioxidant and corrosion inhibitors for gasoline lube oils.     

Modeling of ion transport reactor for oxy‐fuel combustion

This paper aims at investigating the performance of a cylindrical ion transport reactor designed for oxy‐fuel combustion. The cylindrical reactor walls are made of dense, nonporous, mixed‐conducting ceramic membranes that only allow oxygen permeation from the outside air into the combustion chamber. The sweep gas (CO₂ and CH₄) enters the reactor from one side and mixes with the oxygen permeate, and the products are discharged from the other side. The process of oxygen permeation through the reactor walls is influenced by the flow condition and composition of air at the feed side (inlet air side) and the gas mixture at the permeate side (sweep gas side). The modeling of the flow process is based on the numerical solution of the conservation equations of mass, momentum, energy, and species in the axisymmetric flow domain. The membrane is modeled as a selective layer in which the oxygen permeation depends on the prevailing temperatures as well as the oxygen partial pressure at both sides of the membrane. The CFD calculations were carried out using fluent 12.1 (ANSYS, Inc., Canonsburg, PA, USA), whereas the mass transfer of oxygen through the membrane is modeled by a set of user defined functions. The model results were validated against previous experimental data, and the comparison showed a good agreement. The study focused on the effect of oxygen partial pressure and temperature on the resulting combustion zones inside the reactor for the two cases of co‐current and counter‐current flow regimes. The results indicated that the oxygen to fuel mass ratio increases as the percentage of CO₂ increases in the inflow sweep gas for both co‐current and counter‐current flows. The obtained sweep mixture ratio (CO₂/CH₄) of 24 is found within the stoichiometric limit over most of the reactor length in the co‐current configuration, whereas the sweep mixture ratio of 15.67 is found in the counter‐current configuration owing to the high O₂ permeation. Copyright © 2012 John Wiley & Sons, Ltd.     

An ergonomic evaluation of infant life jackets: Donning time & donning accuracy

Canada is considering the development of a new standard for infant/child life jackets. Eight currently available (approved and non-approved) infant/child life jackets were procured for evaluation. Fifty-six participants were chosen as a sample of convenience from the general public for testing. The life jackets were divided into two groups of four, which were donned on a soft infant manikin procured from the Red Cross. In 224 attempts at donning, only 43 (19%) attempts resulted in the life jacket being donned correctly in less than 1 min. Only one life jacket came close to a good design and passed the life jacket standard for donning time and accuracy. Failure rates were observed across all the participants irrespective of age, gender, experience with children and experience with recreational marine equipment. Accuracy and speed of donning the life jacket were hampered as the number of donning sub-tasks increased. It was concluded that it is possible to design a life jacket that can be donned correctly in under 1 min. The life jacket must be of simple, intuitive design and fall naturally into the anatomical shape of the child. A minimum number of ties, zips and clips should be used in the design, and if such connectors are used they should be color coded or of different shapes and sizes to avoid confusion.     

New Method for Testing Fiber-Reinforced Polymer Rods under Fatigue

This paper presents a newly developed specimen for testing fiber-reinforced polymer (FRP) composite reinforcements under cyclic loading. In this configuration the FRP rod is completely encased in concrete. The specimen is formed of three discrete blocks. The end blocks serve as anchors for the rod, whereas the central block provides the concrete environment to the part of the rod where failure is expected to occur. The specimen can be easily handled and uses a very simple test setup that can be adapted to all universal testing machines. An extensive research program has been initiated by the writers to study the influence of varying parameters on the fatigue performance of FRP products. Results of demonstration tests performed on a proprietary carbon FRP rod using the specimen developed are presented in this paper. The results show consistent findings and great potential for using the specimen in different situations such as tensile and cyclic testing of FRP reinforcements.     

Adaptive allocation of resources and call admission control forwireless ATM using genetic algorithms

In wireless ATM-based networks, admission control is required to reserve resources in advance for calls requiring guaranteed services. In the case of a multimedia call, each of its substreams (i.e., video, audio, and data) has its own distinct quality of service (QoS) requirements (e.g., cell loss rate, delay, jitter, etc.). The network attempts to deliver the required QoS by allocating an appropriate amount of resources (e.g., bandwidth, buffers). The negotiated QoS requirements constitute a certain QoS level that remains fixed during the call (static allocation approach). Accordingly, the corresponding allocated resources also remain unchanged. We present and analyze an adaptive allocation of resources algorithm based on genetic algorithms. In contrast to the static approach, each substream declares a preset range of acceptable QoS levels (e.g., high, medium, low) instead of just a single one. As the availability of resources in the wireless network varies, the algorithm selects the best possible QoS level that each substream can obtain. In case of congestion, the algorithm attempts to free up some resources by degrading the QoS levels of the existing calls to lesser ones. This is done, however, under the constraint of achieving maximum utilization of the resources while simultaneously distributing them fairly among the calls. The degradation is limited to a minimum value predefined in a user-defined profile (UDP). Genetic algorithms have been used to solve the optimization problem. From the user perspective, the perception of the QoS degradation is very graceful and happens only during overload periods. The network services, on the other hand, are greatly enhanced due to the fact that the call blocking probability is significantly decreased. Simulation results demonstrate that the proposed algorithm performs well in terms of increasing the number of admitted calls while utilizing the available bandwidth fairly and effectively     

A probabilistic model for assessing the reliability of wind farms in a power system

Modeling the generation of a wind farm and its effect on power system reliability is a challenging task, largely due to the random behavior of the output power. In this paper, we propose a new probabilistic model for assessing the reliability of wind farms in a power system at hierarchical level II (HLII), using a Monte Carlo simulation. The proposed model shows the effect of correlation between wind and load on reliability calculation. It can also be used for identifying the priority of various points of the network for installing new wind farms, to promote the reliability of the whole system. A simple grid at hierarchical level I (HLI) and a network in the north-eastern region of Iran are studied. Simulation results showed that the correlation between wind and load significantly affects the reliability.