Volume 21, No. 4 (2015)
Articles
COCONUT HUSK CHAR BIOSORPTIVITY IN HEAVY METAL DIMINUTION FROM CONTAMINATED SURFACE WATER
AJAYI-BANJI ADEMOLA(1), SANGODOYIN ABIMBOLA(2), IJAOLA OPOLOLA(2)
Applicability of coconut husk char in heavy metal removal was examined in the study. The surface morphology and elemental compositions of the char was investigated with SEM-EDX machine. Heavy metals sorption on 100 g of the char dosage was studied under five different contact times in the column experiment. Isotherm and kinetic models were the probing tools for biosorption mechanism prediction. Results indicated removal efficiency for chromium, cobalt, cadmium, aluminum and arsenic at 60 mins contact time were 72, 80, 86, 89 and 100 % respectively. Contaminate removal depends on metal involved and sorption contact time. Adsorption data are fitted well into Freundlich isotherm model (R2 > 0.92). Pseudo kinetic second order well described the adsorption process, with most R2 values ≥ 0.94. Coconut husk char is an effective biosorbent in sequestration of arsenic, cadmium, aluminum and cobalt in contaminated surface water.
CHARACTERIZATION OF RHEOLOGICAL PROPERTIES OF SEMISOLID MATERIALS USED AS THERMAL INTERFACES. PART I: A BRIEF REVIEW
FLORINA-CARMEN CIORNEI(1), STELIAN ALACI(1)
In optimizing the performances of electronic devices, the semisolids used as thermal pastes have a significant part. The interface material should have a good compliance to follow the shape of the contacting surfaces and higher spreadability but also, have increased filler content for high thermal conductivity. The properties of composite materials are theoretically modeled and for designing a semisolid the rheological characterization is required. The paper presents a concise review of the methods used in rheology for characterization of semisolids.
STUDIES CONCERNING THE BEHAVIOR OF THE SUSPENDED SOLIDS IN THE MIXING PROCESS
MIHAELA-ELENA DASCĂLU(1), EMILIAN MOŞNEGUŢU(1), VALENTIN NEDEFF(1), ALEXANDRA-DANA CHIȚIMUȘ(1), NARCIS BÂRSAN(1)
A high importance is given to the studies concerning the most reliable mixing process with a minimum of energy consumption, because the mixing process is an often used operation in various industries. The main purpose of this paper is to determine and to identify the behavior of the dispersed phase, in this case, the solid particle, during the mixing process. Through the experiment, the mixing process was recorded using a High-Speed camera, which enables following the behavior of the solid particle. The resulting data were used for different types of charts.
THICKNESS INFLUENCE ON ABSORBING PROPERTIES OF STRATIFIED COMPOSITE MATERIALS
IULIANA IAȘNICU [STAMATE](1), OVIDIU VASILE(2), RADU IATAN(3)
Plates known as sound absorbing materials: textiles recovered fabrics plus polyethylene are made layered composite material intended to be used to encapsulate industrial engines, as sources of noise in the production departments. Influence of thickness sound-absorbing material can be supported by the values obtained for the absorption coefficient, but it can be studied as a study case in the anechoic chamber, where the sound pressure level is measured with a sound level meter. Cases captured: a free engine; the engine placed in a metallic cube and motor inserted; metal cube that was doubled separately with one material and then with the composite material proposed. For each situation are eight determinations on the perimeter of a circle with a radius of one meter from the source of the noise. Plot a graph of experimental results that support the idea: greater thickness of the layer of material will cause a better absorption of noise.
EFFECTS OF GEOMETRIC PARAMETERS ON ENTROPY GENERATION IN FIRE-TUBE STEAM BOILER’S HEAT EXCHANGER
OLUMUYIWA LASODE(1), JOSEPH OYEKALE(2), IDEHAI OHIJEAGBON(1), JOHN OLADEJI(3)
This paper presents a parametric study on fire-tube steam boilers’ heat exchanging unit using Entropy Generation Minimization (EGM) technique. Mathematical equation that models entropy generation rate (Ṡgen), and entropy generation number (Ns), were formulated. The entropy generation number was related to the geometric features of the system. Solving the equations showed the effects of each geometric feature on both pressure drop and Ns. Correlation equation relating dimensionless fire-tube length to dimensionless tube diameter was also obtained. The obtained correlation equation is a tool to be incorporated into fire-tube steam boiler design, so as to account for entropy generation during design.
OVERVIEW OF WORKING OF STRILING ENGINES
SUNNY NARAYAN(1), VIKAS GUPTA(1)
Engines are common devices which are important sources of power to run several devices in modern society. Many of these engines are very complex and need high levels of technological advances for smooth operations. This papers focuses on the identification, design and construction of a Stirling engine which can be easily manufactured without any special tooling or exotic materials. The underlying theory of the device is also presented and discussed with future recommendations to improve the current design.
THEORETICAL RESEARCH REGARDING THE RISK-FREE WORK OF THE GANTRY CRANES
GHEORGHE N. RADU(1), IOANA SONIA COMĂNESCU(2)
The research bases on the observation that the check imposed by the National Authority I.S.C.I.R. regarding the cranes authorization is necessary but not enough for the assurance of their work safety. The current specific rules do not contain provisions concerning the vibratory state of the cranes. Practice shows that the beginning of a work which is outside the normal parameters (changes of the optimum technical state – risk of accidents occurrence), appear in their vibratory mark. The research has as main goal the increase of the work safety and the elimination of the risk of accidents.
EXPERIMENTAL STUDIES REGARDING THE RISK-FREE WORK OF THE GANTRY CRANES
GHEORGHE N. RADU(1), IOANA SONIA COMĂNESCU(2)
The present paper sets that the prerequisite of a crane’s failure (changes of the optimum technical state – risk of accidents occurrence), appear in their vibratory mark. The research has as main goal the increase of the work safety and the elimination of the risk of accidents. The tests had in view both the truss answer to dynamic forces in wind-bracings and the dynamic regime of the main beam.
ENVIRONMENTAL SYSTEM ENGINEERING (ESE): MODELING AND OPTIMIZATION OF A TEXTILE EFFLUENT DISCOLORATION PROCESS BY SORPTION
CARMEN ZAHARIA(1)
Nowadays, an interdisciplinary field of engineering that focuses on analytical and/or empirical models represented by mathematical, data-driven and biotic structures combined with physical, biological and ecological processes in water, air and eco-systems is developing, i.e. environmental system engineering (ESE). In this system, environmental modeling and process optimization acts together for solving problems with environmental systems, especially for minimizing pollution, or eco-toxicological effects. The present paper proposes the study of modeling and optimization of an environmental system (i.e. textile wastewater treatment system based on sorption onto indigene peat) for its discoloration (consequently, decreasing of color, organic and inorganic loads of effluent discharged in aquatic receptor, or inside reused). All performed laboratory tests consisted in 22 hours-sorption experiments onto peat applied for a real colored textile effluent, organized with respecting of an empirical planning by a central active composite rotatable 23 order design, considering as independent variables the peat dose (X1), pH (X2), and temperature (X3), and as optimization criterion, or decision function, the discoloration degree, or color removal (Y, [%]). The mathematical model was found adequate for the textile wastewater treatment, and the optimal operational conditions for highest discoloration efficiency were proposed.
EVALUATION OF WATER POLLUTION STATUS IN BAHLUI RIVER (IASI TOWN AREA) DUE TO DOMESTIC AND URBAN WASTEWATER TREATMENT ACTIVITIES
CARMEN ZAHARIA(1)
This study presents some data about the water pollution status of Bahlui river in Iasi town area (two control sections) mainly due to domestic and urban wastewater treatment activities, considering especially some quality indicators (i.e. nitrogen-based nutrients, total phosphorus and sum organics content) evaluated for 2009-2010. The Bahlui water classification by European standards in Iasi town area corresponds to ‘medium’ (WQI = 53.893 - 64.345). The real water pollution state of Bahlui river (Iasi town area) is estimated by the global pollution index (I*GP), and corresponds to values of 2.80-2.929 (Valea Lupului-Iasi control section), and 3.030-3.196 (Holboca control section, i.e. downstream of Dancu wastewater treatment plant). These values are indicating an aquatic environment modified by domestic and urban wastewater treatment activities, generating discomfort effects, or producing stress against aquatic life forms. These data are recommending application of hydro-ameliorative/remediation actions, and permanent control of Bahlui watercourse quality in all existing control sections.