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Unsteady MHD Natural Convection Flow of Nanofluid in a Cavity Containing Adiabatic Obstacle with Heat Corners
Get PDF Unsteady natural convection heat transfer of nanofluid within cavities with local heaters occurs in several engineering applications. Therefore, investigation of nanofluid flow and heat transfer processes in such systems has a considerable value for evolution of industry. In the current investigation, unsteady MHD natural convection flow of Cu-water nanofluid and heat transfer behavior in square cavity containing a centered adiabatic square block. The mathematical formulation part for present problem is presented in succeeding section. It has been found the size of the adiabatic obstacle influences the behavior of the nanofluid and conduction becomes dominant when size aspect ratio increases to 0.5. It is also noticed that angle of the applied magnetic field can maximize(minimum)the rate of heat transfer if applied in the stream-wise (normal) direction. The novelty of the present work is to consider cavity containing a centered adiabatic square block as well as unsteady effects in the natural convection of nanofluids
A Clustering Algorithm for Block-Cave Production Scheduling
Get PDF Production scheduling is one of the most important steps in the block-caving design process. Optimum production scheduling could add significant value to a mining project. The goal of long-term mine production scheduling is to determine the mining sequence, which optimizes the company’s strategic objectives while honouring the operational limitations over the mine life. Mathematical programming with exact solution methods is considered a practical tool to model block-caving production scheduling problems; this tool makes it possible to search for the optimum values while considering all of the constraints involved in the operation. This kind of model seeks to account for real-world conditions and must respond to all practical problems which extraction procedures face. Consequently, the number of subjected constraints is considerable and has tighter boundaries, solving the model is not possible or requires a lot of time. It is thus crucial to reduce the size of the problem meaningfully by using techniques which ensure that the absolute solution has less deviation from the original model. This paper presents a clustering algorithm to reduce the size of the large-scale models in order to solve the problem in a reasonable time. The results show a significant reduction in the size of the model and CPU time. Application and comparison of the production schedule based on the draw control system with the clustering technique is presented using 2,487 drawpoints to be extracted over 32 years
Heat and Mass Transfer Analysis for the MHD Forced Convective Flow of a Nanofluid over a Slendering Stretching Sheet with Radiation in Porous Medium
Get PDF Computational analysis of radiative heat and mass transfer of nanofluid over a slendering stretching sheet in porous medium with uneven heat source and slip effects have been carried out in this article. The transformed equations a of the flow model are solved by the Runge-Kutta scheme coupled with shooting method to depict the dimensionless velocity, temperature, and concentration at the boundary layer. Numerical computations are carried out and discussed for skin friction coefficient and local Nusselt number. We found an excellent agreement of the present results with the existed results under some special conditions. It is also found that the heat transfer performance is high in the presence of velocity slip effect. Dimensionless skin-friction coefficient has decreased for increasing magnetic field, power law-index with velocity slip and wall thickness
Energetic Assessment of an Electronic and a Thermostatic Expansion Valve for a Variable Capacity Compressor
Get PDF In this study, a chiller system with an electronic expansion valve (EEV) and a thermostatic expansion valve (TXV) were compared from an energy saving view under variable and fixed speed compressor. The experimental chiller system under study has a variable speed scroll compressor, EEV and TXV, air cooled condenser and auxiliary equipments. The R134a was used in the compressor as a refrigerant. Although in variable speed chiller systems usually EEVs are used, in this study a TXV was also used to compare its performance. The results of the experimental studies show that the chiller system with EEV has 30% lower superheat value and 6% lower power consumption than the chiller system with TXV under variable speed operation. From the fixed speed compressor view, the chiller system with TXV performs 1.7% lower superheat value than the chiller system with EEV and, the chiller system with EEV has 8.5% higher compressor power consumption than TXV
Removals of Gentamicin and Benzo[a]Pyrene in an Anaerobic Multichamber Bed Reactor
Get PDF The petrochemical industry wastewaters were not treated effectively due to high concentrations of Polycyclic aromatic hydrocarbon (PAH) benzo [a] pyren (BaP) and an aminoglucoside antibiotic gentamicin (GNT) in an aerobic treatment plant in Turkey. The high GNT concentration in this industry wastewater mainly originated from the toilets of the working people and from the medical care facilities since an intestinal epidemic occurrred for a period of approximately 1.5 years. The High BaP concentrations release into the wastewater originated from the high BaP production in this industry. In order to improve the biodegradability of petrochemical industry wastewaters containing excess BaP and GNT, different mixtures of BaP and GNT were biodegraded in a high rate anaerobic multichamber bed (AMCBR) reactor. The maximum anaerobic yields for 10 mg/L BaP and 1 mg/ L GNT alone were 45% and 12%, respectively. The addition of primary susbstrate increased the 200 mg/L BaP and 50 mg/ L GNT removals to 97% and 89%, respectively. BaP was biodegraded at short operation times compared to GNT. At low BaP (10-200 mg/ L) and GNT (10-35 mg/ L) concentrations, a non-competitive inhibition does not affect the binding of the substrate and KS were not affected. At high BaP (500-900 mg/ L) and GNT (75-100 mg/ L) concentrations, the BaP and GNT were biodegraded according to competitive inhibition with increased KS. BaP and GNT were biodegraded according to Haldane equations at high concentrations where they were used as the sole substrate
Structural Stability Assessment of a Masonry Chimney Subjected to Shocks by Vibration Measurements
Get PDF Nowadays buildings can be stressed and shocked in different ways. Rail and road traffic, demolition work, machines, bells, wind and human movement itself can burden structures and disturb people. Not only a vibration prognosis, but also a monitoring during certain work is important to ensure buildings’ stability. A masonry chimney subject to shocks due to demolition works of surrounding halls was examined by using a new vibration measuring technique. This paper describes this new technique and its application during monitoring. For the measurement technique, the limit values of the German standard DIN 4150-3 were used and the events where this reference values exceeded, were examined in detail. A dynamic analysis of the structure, where the natural frequencies and their modal masses were determined, shows that the frequency-dependent reference values of the German standard DIN4150-3 for the protection of structures, include a relatively high safety factor. A possible exceeding of the values does not immediately lead to a loss of stability
MILP Models for Scheduling Dynamic Jobs with Sequence Dependent Setup Times and a Variable Maintenance on a Single Machine
Get PDF The single machine scheduling problem with variable maintenance has been widely investigated by both academics and practitioners. Differently from most papers proposed so far, and conforming to a real-world process in the semiconductor industry, in this paper a single variable maintenance task has to be carried out within a specific time interval. The maintenance duration is an increasing function of its starting time. The objective is to minimize the total tardiness considering release times and sequence dependent setup times of jobs as well. Since an earlier maintenance starting time implies a smaller maintenance duration but a higher completion time of the subsequent jobs, the best schedule including maintenance activity and jobs has to be achieved. In order to optimally solve the scheduling problem at hand, two distinct mixed integers linear programming models (MILPs) are proposed and compared under the computational efficiency viewpoint
Decontamination using Chlorine Dioxide Disinfectant with Adjuvants Verses Hydrogen-Peroxide and Pentapotassium Disinfectants on Farm Equipment
Get PDF Agricultural machinery and farm equipment are potential sources of infectious material that can lead to the contamination and spread of diseases if proper action isn’t taken. Two stage decontamination methods, involving power washing followed by disinfectant applications, are needed to clean farm equipment, agricultural transport vehicles, and storage units. The field experiments confirm that pressure washing surfaces is an extremely important step in enhancing spore efficacy. Log10 reduction values were 5.45 and 2.90 for disinfectant applications with and without power washing, respectively. Both experiments show that the commercial chlorine dioxide disinfectant Electro-Biocide was an effective disinfectant alone and when mixed with adjuvants. Increasing the concentration of some tested adjuvants resulted in more spores being removed or killed, however this was not true for all adjuvants tested in these two experiments
Shale Oil: Its Present Role in the World Energy Mix
Get PDF When oil shale rocks are heated (pyrolysed) in absence of oxygen it produces shale oil. The shale oil available technologies and production capacities in million bbl/year are the Enefit280, (1.7) VKG Petroter, (0.63), (while total Estonian companies production is 1.6) Brazilian Petrosix, (1.0) Fushun retorts processes, (0.9) and the newly installed ATP process in China in testing stage. The shale oil produced by these technologies is used as heavy fuel oil for heating purposes or ships fuels due to its physical properties and contaminants. The contribution of shale oil in the energy mix is increasing but up to now is insignificant
A Comparative Investigation on Outdoor and Laboratory Test of the Degradation Rates for Different Types of Photovoltaic Modules with Different Exposure Periods
Get PDF Understanding field failure and degradation modes in solar photovoltaic (PV) modules is very important for various reasons especially for this widely used technology. The University of Applied Sciences Ostwestfalen-Lippe in Höxter owns photovoltaic-modules of different cell types, sizes and operation periods in German weather conditions. This paper presents a detailed degradation investigation and performance parameters analysis for chosen samples of polycrystalline, monocrystalline and thin film modules in the laboratory and outdoor test conditions after 10 years of exposure. The obtained measurements were standardized and then compared with the warranted values of the manufacturer’s datasheets for each module type. The real outdoor measurements for the larger units show that the maximum power Pmax after 10 years of exposure for polycrystalline, monocrystalline and amorphous thin film modules had declined by: 8.47%, 37.67%, and 19.05% respectively, which translates to an annual linear degradation rates of 0.652%, 3.67%, and 1.465% for each type respectively. While the maximum power output of the smaller units had declined by 19.05%, 19.36%, and 21.75% for polycrystalline, monocrystalline and amorphous thin film modules respectively, which also translated to annual linear degradation rates of 1.48%, 1.67%, and 0.6% for each type respectively. On the other hand, the laboratory tests for these modules show that there is a clear variation with the obtained outdoor results, where the Pmax for the same larger units had declined by 39.6%, 57.4%, and 82.5% for polycrystalline, monocrystalline and thin film modules respectively, While the Pmax output of smaller units had declined by 51.2%, 39.38%, and 9.39% for polycrystalline, monocrystalline and thin film modules respectively, The comparison of the efficiency and fill factor parameters for the obtained results with the manufacturer’s data shows that the outdoor measurements introduce close results than the laboratory results. The discoloration of the encapsulant is the most frequently occurring visually observable defects on the modules