The use of beta-carotene as environmentally safe inhibitor for Cu-Al-Ni alloyscorrosion in sulfide polluted chloride solutions

The stability of Cu-Al-Ni alloys used in the manufacture of NaCl in Egypt was investigated in sulfide polluted chloride solutions. Three different alloys, namely, Cu-10Al-5Ni, Cu-10Al-10Ni and Cu-10Al-45Niwereinvestigatedinchloride containingsulfide-ions using different electrochemical techniques including polarization and electrochemical impedance spectroscopy. The presence of sulfide ions in the chloride solution accelerates thecorrosion of Cu-Al-Ni alloys,whereas the increase of the nickel content in the alloy improves its corrosion resistance.?-carotene as eco-friendly corrosion inhibitor was used to protect the Cu-10Al-Ni alloys from corrosion in presence of sulfide ions. The corrosion inhibition efficiency reached >95% at 50 ppm of ?-carotene. The alloy surface was investigated by the scanning electron microscope and the surface constituents were analyzed by EDAX. Keywords: Corrosion; chloride, Cu-Ni alloys; EIS; sulfide pollution

A review and comparison of efficient flooding schemes for on-demand routing protocols on mobile ad hoc networks (MANETs)

Since the basic components of ad hoc wireless networks are mostly battery-operated portable devices, power conservation is one of the central issues of such networks. Power-conservative designs for ad hoc networks pose many challenges due to the lack of central coordination facilities. Existing on-demand routing protocols perform route discovery by flooding the network with a query message requesting a route to the destination. Flooding is used because of its simplicity and greater success in finding the best route between the source and destination available at that time of route discovery. However, as flooding involves querying all reachable network nodes, frequent flooding can rapidly deplete the energy reserved at each node. In addition to consuming significant portions of the available network bandwidth. Further, as the number of communicating nodes increases, more congestion, contention, and collisions can be expected. This paper reviews and compares approaches for optimizing bandwidth efficiency of route discovery, where several efficient flooding schemes have been presented based on different techniques to solve the problems related with the traditional blind flooding

Re-Scaling of Energy in the Stringy Charged Black Hole Solutions using Approximate Symmetries

This paper is devoted to study the energy problem in general relativity using approximate Lie symmetry methods for differential equations. We evaluate second-order approximate symmetries of the geodesic equations for the stringy charged black hole solutions. It is concluded that energy must be re-scaled by some factor in the second-order approximation.Comment: 18 pages, accepted for publication in Canadian J. Physic

Numerical Investigation of Buoyancy Effect Associated with a Continuously Moving Horizontal plate

This work presents numerical studies of the effects of buoyancy force parameter, Bf, coupled with viscous dissipation on the convective heat transfer in a fluid-filled rectangular cavity. The cavity is bounded by a hot horizontal plate maintained at temperature Tw and moving continuously at velocity Uw. It is also bounded on the left vertical and lower horizontal sides by cold isothermal walls and an adiabatic vertical wall on the right. The cavity was filled with quenching medium. The study was carried out for different quenching media such as oil with Prandtl number, Pr = 10, air with Prandtl number, Pr = 0.7 and liquid metal with Prandtl number, Pr = 0.01, for various bouyancy parameters in the range 5 x 10-3 ≤ Bf ≤ 10-2, fixed Eckert numbers, Ec = 1.0 and mixed convection parameter, Gr/Re2 = 1.0, in order to characterize the nature of the flow patterns and energy distribution. The flow governing equations including the momentum and energy equations were thereby solved using the finite difference method. The results are presented in the form of profiles for temperature, velocity and local Nusselt numbers. The results show that the buoyancy force parameter has significant influence on the velocity and temperature profile for a Prandtl number higher than unity at fixed viscous dissipation. Further results show that an increase in the buoyancy force parameter for a Prandtl number greater than unity leads to a significant increase in the maximum velocity attainable in the cavity. The results would be useful as baseline data for manufacturing and material processing industries involved with wire drawing, continuous rolling and glass fiber productions. Keywords: Buoyancy effect, Finite difference scheme, Heat transfer, Isotherms, Mixed Convectio

Thermal Evaluation of a Parabolic Trough Solar Concentrator Using Three Different Receivers

Energy demand, global warming from the fossil fuels and attempt to reduce greenhouse gas emission have placed the centre of attention on how to utilize an alternative sources of energy such as renewable energy technology This work presents the design, fabrication, and evaluation of the performance of Parabolic Trough Solar Concentrator (PTSC) as a source of heat energy. The PTSC is built, having the Supporting stand made of mild steel and reflector is made of the segmented mirror having a reflectivity of 0.85, a rim angle of 90o and aperture area of 2.5 m2 and with a concentration ratio of 11.7. The receiver pipes are made of three different materials; copper, aluminum, and stainless steel. The effects of shifts in focal lengths on the performance of the PTSC with three different receivers were investigated. The results reveal copper as a receiver tube conducts heat to the heat transfer fluid better than aluminum and stainless steel receivers. The focal length of 30 cm gave the best results compared to other values of 27 and 35 cm with a maximum temperature of 114.4 oC. The experimental results revealed that useful heat gained, overall heat loss coefficient, collector efficiency factor, heat removal factor, collector and thermal efficiency were 147.8 J, 5.04 W/m2K, 0.05, 15.05, 0.032% and 15.5% respectively. The study shows that the Parabolic Trough Solar Concentrator as a source of heat energy gives a promising performance. This concentrator will reduce the dependence on the electric power supply, and it controls pollution emanating from fossil fuel, thereby reducing environmental problems. Keywords: Parabolic Trough Solar Collector, Segmented Mirror, Efficiency, Receivers. DOI: 10.7176/JETP/9-5-03 Publication date:June 30th 201

Experimental Evaluation of a Thermally Driven Adsorption Refrigeration System in Ogbomoso Environs

Solar energy is the most promising among the available green energy sources and also the remedy to the increasing global warming potential and ozone depletion. This paper presents an experimental evaluation of an adsorption refrigeration system uses solar energy as a source of heat gain to drive the refrigeration system. It consists of a solar collector, an adsorbent bed, a condenser and an evaporator. The effect of variation of the ambient, condenser, evaporator and desorption temperatures on the COP system and SCP cycle with local weather parameters were investigated. A parabolic solar concentrator was built to collect the solar energy to heat the combination of adsorbent, Activated carbon and adsorbate, methanol and the system employed solar energy as the main power supply. The experimental results revealed that the ambient, condenser, evaporator and desorption temperatures were increased by 25%, 4%, 13% and 265% respectively with solar time from 9hr to 13hr. The response of COP and SCP with variation in solar radiation and desorption temperature had higher influence compare to other weather parameters. The collector and thermal efficiencies were 0.014 and 6.98% respectively at the peak inner adsorber temperature of 114.1 oC. The respective cycle and net solar COPs of the ARS were 0.408 and 0.00080 at an evaporator temperature of 17.1 oC. This study showed that the solar thermal-driven ARS performed well in south-western climatic conditions of Nigeria and can be used to replace conventional refrigeration system to reduce the effect of global warming and environmental pollutions caused chlorofloro-refrigerants. Keywords: Solar, Adsorption, Refrigeration, COP, Concentrator

Stability of Some Copper Ternary Alloys in Chloride Solutions Polluted by Sulfide Ions

The electrochemical performance of three copper alloys was investigated in simulated marine solution polluted by sulfide ions. Polarization techniques and electrochemical impedance spectroscopy, EIS, were used. Surface examination and morphological studies were employed. The results showed that the Cu-10Ni-10Zn alloy is more stable than the other two alloys. The alloy surface was covered by a barrier layer protecting it from corrosion. The thickness and resistance of the barrier layer formed on the Cu-10Ni-10Zn alloy increases with the increase of the immersion time. The mechanism of the corrosion process and the barrier film formation was discussed.  A comparison was made between the electrochemical stability of the three alloys in sulfide polluted chloride solution. The incorporation of Ni in the Cu2O barrier film leads to its stabilization and the stability is enhanced by the presence of Zn. The results leads to the recommendation of the Cu-10Ni-10Zn alloy for applications in sulfide polluted marine environments. Keywords:  Copper alloys, EIS, Polarization, SEM, Passive Films

THE PHENOMENON OF WAKES FORMATION AND DEVELOPMENT BEHIND LIQUID DROPLETS

Numerical simulations of spherical; droplets sedimenting in a Newtonian fluid in an unbounded region were investigated by using finite element method for Reynolds number up to 300. The computations are thereby carried out with the penalty method instead of the integral method. The effect of the viscosity ratio n* in the range 0.02 < n* < 1000 and the density ratio p* in the range 0.02 < p* < 1000 on the wake formation and development was studied. It was observed that no wake is formed behind s droplet when the viscosity ratio n* is below 2.3. The critical Reynolds number for a droplet with fluid properties p* = 1 and n* = 50 and another droplet with fluid properties p* = 1000 and n* = 50 is the same, and is 28.5. The viscosity ratio thus has strong effect on wake formation while density ratio has an insignificant effect. Further results show that the wake length and the angle of separation depend very strongly on the viscosity ratio. The results are very useful for the design and optimization of engineering equipment where droplets occur