Effect of controlled pH and concentrations of copper sulphate and silver nitrate solutions during nanoparticles synthesis towards modifying compressor oil yield stress and lubricity for improved refrigeration

Vapour compression systems are designed to use refrigerants and lubricants for smooth performance. However, recent advances in nanoparticles research have led to the use of Cu and Ag-nanoparticles (AgNPs and CuNPs) as compressor fluid modifiers. In this study, several concentrations of AgNO3 and CuSO4 solutions were adopted in synthesizing nanoparticles for use in a compressor oil. The optimum Coefficient of Performance and cooling effect of the system were observed at optimum concentrations of 0.08 and 1.6 M for the Ag- and CuNP- lubricating oils, respectively, thus giving better cooling effects than the ordinary Copeland 46B oil. At optimum conditions, the weakly acidic CuNP-oil performed better than the weakly alkaline AgNP-oil with cooling temperatures of −8 and 2.3 °C, respectively. Equilibrium concentrations for both particulate oils were found to be 0.08 and 2.7 M at the same yield stress of 2 lb./ 100 ft2, while the lubricities of the oils ranged from 0.119–0.154, 0.134–0.155 and 0.156–0.180 for the CuNP-, AgNPand Copeland 46B oils, respectively. Since lower lubricities are indicative of better lubrication, it then implies that the CuNP-oils gave the best lubricities. An increase in the motor speed gave a corresponding increase in the torque generated as well as, the lubricity coefficients and lubricities of all the oils. Enthalpy changes ranged from 70.3–520 Jg/mol for the 1.1–2.1 M CuNP-oils, although, it was very high (4523.5 Jg/mol) for the 2.7 M CuNP-oil which may be due to the superficial distribution of copper as well as its large surface area to charge ratio at the oil surface, thus making it a better conductor of heat relative to the AgNP-oils. For the AgNp-oils, the enthalpy changes were very small i.e. from −1.012 – 1.2957 Jg/mol whereas, it was 523 Jg/mol for the Copeland oil. Furthermore, the least power consumption was obtained for the CuNP-oil

Decontamination of Wastewater Effluent using Sugar Cane Bagasse and Soybean Hulls

Wastewater effluents from industrial processes often pose environmental as well as health risks to humans when these waters are consumed without proper trexatment. In this study, distilled water and citric acid were used as modifiers in order to establish the comparative abilities of modified soybean hull and sugarcane bagasse as means of reducing copper and zinc chlorides to their metals and subsequently adsorbing the metals in order to propose both materials as low cost adsorbents for heavy metals. Based on the results, the modified soybeans have good potential for adsorbing Cu metal while sugarcane bagasse showed preferential adsorption of Zn from waste water. Also, results from optimization gave a pH of 4 and 5 for the modified forms of the bagasse and soybean respectively. While a mass of 1g of each adsorbent gave the best removal rate for their preferred metals, the optimum volume for the highest metal adsorption was found to be for solvent of 35 ml/g adsorbent. Adsorption rate was found to increase with temperature and time for both adsorbents

Determination of Optimum Conditions for the Production of Activated Carbon Derived from Separate Varieties of Coconut Shells

Activated carbons were produced from coconut shells of tall and dwarf tree varieties.The activated carbon from the tall tree variety was initially synthesized using 1Mconcentration of each of ZnCl2, H3PO4, and KOHsolutions. From the adsorptive tests conducted using methylene blue solution, the activated carbon produced with H3PO4 gave the best absorbance and adsorptive performance. Coconut shells of dwarf tree variety were then obtained and treated with same mass of coconut shells of the tall tree variety using varied concentrations of the acid in order to determine whether the optimum concentration and temperature for producing carbon black fromthe coconut shells are distinct or similar for both varieties.Theprocess was alsomodelled using the Differential Response Method (DRM) in order to determine the yields and adsorptive performances of the activated carbons by varying the carbonization temperature and concentration. The results from experiment and the developed mathematical model were both found to be in agreement giving the optimum concentration of phosphoric acid and pH for producing activated carbon to be 0.67M and 2.07 for the tall tree variety and 1M and 1.98 for the dwarf variety at optimum temperatures in the range of 450–575∘C and 575∘C, respectivel

Impact of Hall Current on the Entropy Generation of Radiative MHD Mixed Convection Casson Fluid

One of the fundamental problems in engineering processes is the efficient utilization of energy during convection in fluid flow. Studies show that entropy generation exists for all fluid transfer processes and entropy generation destroys useful energy. Furthermore, it has been discovered that some pertinent flow parameters might be chosen in order to minimize entropy generation inside the system. In view of this, the fully developed electrically conducting free convection Casson fluid flow formed by two infinite vertical parallel plates with thermal radiation, Hall current and rotation effects is investigated. The governing equations have been obtained and transformed by suitable transformation variables. Semi-analytical solutions via differential transform technique are obtained using relevant boundary conditions. The results are utilized to calculate fluid irreversibility and Bejan number. The impacts of Hall parameter, rotation parameter, thermal radiation, Casson parameter, Hartman number, Schmidt number and chemical reaction together with skin friction, Nusselt number and Sherwood number are discussed and presented via plots and tables. Generally, entropy generation is discouraged at the upper walls of the channel with higher values of Casson parameter, Schimdt number and chemical reaction parameter while Hall current parameter boost entropy generation in the entire flow channel. Furthermore, Heat transfer irreversibility dominates entropy generation due to a rise in the values of chemical reaction parameter and Schmidt number

Entropy Generation of Unsteady MHD Couette Flow through Vertical Microchannel with Hall and Ion Slip Effects

In this work, the entropy generation of unsteady hydromagnetic Couette flow through vertical microchannel has been considered, the effects of Hall current and Ion-slip are also examined. One of the plates moves with uniform velocity in the direction of the fluid flow while the other plate is stationary. The partial differential equations governing the flow are obtained and transformed to ordinary differential equations. The obtained solutions for the velocity and energy equations via differential transform technique are used to calculate the entropy generation and Bejan number. The results are presented through plots and discussed. It is noticed that primary velocity decreases with increase in Hall current, ionslip and magnetic field parameters whereas it increases as rarefaction parameter, wall-ambient temperature difference ratio, Brinkman number and Grashof number increase in values. Also secondary velocity receives a boost with increase in Hall current, Ion-slip, rarefaction parameters, wall-ambient temperature difference ratio, Brinkman and Grashof numbers. Furthermore, entropy generation is minimised as Hall current, Ion-slip and rarefaction parameters increase

Influx potential and sequestration of CO2 in Cement based material towards establishing a proactive measure for combatting structural deformations

The effect of carbon dioxide sequestration by Sandcrete structures was investigated as a means of reducing CO2 emissions. Experiments were conducted to determine the concentration of trioxocarbonate IV (CO32-) in sandcrete samples as well as its effect on soil pH. The results showed that the presence of CO32-in sandcrete samples evidenced the process of carbonation in sandcrete structures and other cement-based material which provides an alternative means of CO2 Sequestration. Also, the concentration of CO32- varied along heights and horizontal distance within sections of the sandcrete structure. The acidic nature of the soil close to some sections of the sandcrete structure experienced varying pHs of 6.14 - 6.35 which gave room for enhanced leaching which seriously undermines the strength of the sandcrete structure. The percentage concentration differential in the horizontal and vertical directions, were found to vary widely from 5-46%. This constitutes a potential danger i.e. cracking and possible collapse of the structure. The results of calculated diffusivity values and concentration gradients of the carbonate ion conformed with results obtained using a predictive model which helped in monitoring the migration patterns of CO3 2 - in the sandcrete structure

Advancement in engineering materials and the growing concern

Corrosion has been and still the world's worst nightmare which costs hundreds and thousands of dollars for companies to maintain their equipment and repairs. Studies are being done all around the world to create the solution toward preventing the corrosion by surface engineering technology. One of the simplest and most cost effective methods to provide thin film coating for advance application is through electrolytic deposition route. Thus this review looks into the advances of materials and corrosion challenges

Electrochemical reaction of corrosion and its negative economic impact

Persistent corrosion problems through hazardous chemicals and hydrocarbon are potentially harmful resulting into failure and breakdown of infrastructure in marine, oil and gas vessels, petroleum distillation plant, and chemical processing industries. Despite this unstoppable catastrophe, reduction in the amount of cost incurred by corrosion has been an effort by researcher in the field of material science to tackle. This paper addresses the major challenge of materials failure in services resulting to high cost, and the potential remedy form from several applications

Inactivation kinetics and thermodynamics assessments of Geobacillus stearothermophilus during thermal sterilization for products safety

Chemical kinetics and thermodynamics provide modes and mechanisms for the thermal death of microbial spores. In this study, the effect of thermal inactivation on Geobacillus stearothermophilus, a highly heat-resistant bacterial species, was studied over the temperature range of 95, 100, 105, and 110 ◦C and holding sterilization periods of 10, 15, 20, 25, 30, and 45 min by the application of mathematical analysis of kinetic and thermo�dynamic properties. Thermal death rate constant, k, for the best kinetic order of sterilization ranged between 0.0431 to 0.1581 min− 1 with the energy of activation, Ea, estimated to be 115.96 kJ/mol. Two primary thermal death kinetic models were applied (log-linear first order and the nonlinear Weibull). Weibull’s model provided more reliable kinetic parameters to predict the effect of thermal treatments. Concave curves (α >1) were pre�dicted with the Weibull’s model for 100, 105, and 110 ◦C (1.57, 1.26, and 1.22 respectively), indicating the susceptibility of spores to lethal treatment. The rate parameter, ɸ (first reduction time) decreased with increasing thermal heating (28.80 min (95 ◦C), 21.08 min (100 ◦C), 14.61 min (105 ◦C), and 9.65 min (110 ◦C)) following the paths of the D-values (about 7 min to attain 88% spores’ destruction after 110 ◦C heating) of the log-linear kinetic model. Thermal death time (TDT) for the complete destruction of spores was predicted to be after 40 min at 110 ◦C. The z-value was 23.31 ◦C, indicating the sterilization temperature that must be attained for one log destruction of spores. The heat of activation showed endothermic reactions for all temperatures (ΔH ranged 112.90 – 112.78 kJ/mol), Gibb’s free energy of activation, ΔG, ranged from 325 – 333.74 kJ/mol (indicating a non-spontaneous reaction), and the entropy of activation (ΔS) showed reversibility of reaction (ΔS < 1) for all the thermal temperatures