Convective Heat Transfer and Fluid Dynamic Characteristics of SiO2 Ethylene Glycol/Water Nanofluid

Nanofluids comprised of silicon dioxide (SiO₂) nanoparticles suspended in a 60:40 (% by weight) ethylene glycol and water (EG/water) mixture were investigated for their heat transfer and fluid dynamic performance. First, the rheological properties of different volume percents of SiO₂ nanofluids were investigated at varying temperatures. The effect of particle diameter (20 nm, 50 nm, 100 nm) on the viscosity of the fluid was investigated. Subsequent experiments were performed to investigate the convective heat transfer enhancement of nanofluids in the turbulent regime by using the viscosity values measured. The experimental system was first tested with EG/water mixture to establish agreement with the Dittus-Boelter equation for Nusselt number and with Blasius equation for friction factor. The increase in heat transfer coefficient due to nanofluids for various volume concentrations has been presented. Pressure loss was observed to increase with nanoparticle volume concentration. It was observed that an increase in particle diameter increased the heat transfer coefficient. Typical percentage increases of heat transfer coefficient and pressure loss at fixed Reynolds number are presented.     

Design,fabrication and performance evaluation of natural circulation rectangular box-type solar domestic water heating system

This study includes design and experimental analysis of a solar domestic water heating system. Water heating systems with glazed and unglazed collectors were constructed and tested at Dhaka, Bangladesh, at a latitude of 23.7 °N. Collector thermal efficiency and capability of raising water temperature were considered as performance evaluation measures. A typical day analysis showed that collector efficiency varied with time and touched its peak at around 12:00 h. During testing, the efficiency of the glazed collector increased by about 70.3% when compared with the unglazed collector. Average collector efficiency over the whole test period was also estimated to be 57.3% and 33.7% for glazed and unglazed collectors, respectively. Maximum water temperatures measured at daytime user outlets were, respectively, 82.4 °C and 65.5 °C for domestic water heating systems with glazed and unglazed collectors and approximated to be 49 °C and 32 °C higher than the ambient temperature. The glazed collector eventually offered significantly higher performances over the unglazed collector in improving system performance.     

A graph theoretic approach to evaluate the intensity of barriers in the implementation of total productive maintenance (TPM)

Total productive maintenance (TPM) is an innovative approach to maintenance which holds the potential for enhancing effectiveness of production facilities. But, implementation of TPM is not an easy task. Innumerable barriers are encountered in real-life cases during TPM implementation. It is very essential to evaluate the nature and impact of these barriers so that production and maintenance managers can cultivate some strategies to overcome these barriers. In the present exertion, a graph theoretic approach has been applied to find the intensity of these barriers through an index which is computed through a permanent function obtained from the digraph of TPM barriers.     

An approach for estimating the end-of-life product disassembly effort and cost

Disassembly is the process of physically separating a product into its parts or subassembly pieces. The overall economics of the disassembly process, and in particular the cost to disassemble, is still not well understood. In this paper our goal is to introduce a methodology that will support and facilitate the economic analysis of the disassembly activity. We present a multi-factor model to compute the disassembly effort index (DEI) score, which is representative of the total operating cost to disassemble a product. The DEI score can then be compared against the projected market value of the disassembled parts and subassemblies to get an economic measure. To develop the DEI model we surveyed a variety of commercial disassembly facilities. Based on these surveys we propose a multifactor weighted estimation scheme. The seven factors are (i) time, (ii) tools, (iii) fixture, (iv) access, (v) instruct, (vi) hazard, and (vii) force requirements. The DEI scale is defined in the 0 to 100 range. This range is assigned on a weighted basis to each of the seven factors. For each factor, an independent utility scale is formulated, using the assigned range as anchors. Using a conversion scale the DEI score is used to derive an estimate of disassembly cost and the disassembly return on investment. An example is presented.     

Role of some transition metal cations on the kinetics of thermal dehydration of synthetic zeolites

Zeolite was synthesized by the interaction of sodium silicate and sodium aluminate solution. The gel formed was purified and physico-chemically characterized. The gel was converted into different cationic forms, like, Ni²⁺, Co²⁺, Cd²⁺, etc., by ion exchange process. Isothermal dehydration kinetics of the hydrogel was studied from thermo-gravimetry. The gel dehydration reaction was observed to be low energy diffusion controlled process and the major part of the process followed first order kinetics. Exchangeable cations affected the kinetic parameters of the dehydration process.     

Comparative study of the performance of conventional and column flotation when treating coking coal fines

Investigations were carried out on coking coal fines by conventional cell and column flotation techniques. The effects of different operating parameters were evaluated for both conventional and column flotation. The coal fines were collected from Bhojudih washery, India. These coal fines averaged 24.4% ash, 19.8% volatile matter and 53.8% fixed carbon on a dry basis. A commercial grade sodium silicate, light diesel oil and pine oil were used as depressant, collector and frother respectively. The flotation performance was compared with release analysis. The conventional flotation results indicated that a clean coal with 14.4% ash could be obtained at 78.0% yield with 88.4% combustible recovery. The ash of the clean coal could be further reduced to 10.1% at 72.0% yield with 85.6% combustible recovery by using column flotation. The column flotation results were close to those obtained by release analysis.     

Study of different approaches for management of contaminated emulsified aqueous secondary waste

The underlying objective governing the management of radioactive waste is protection of human being and the environment, now as well as in the future. As a waste management philosophy, utmost emphasis is given to waste volume minimization at all stages of design, operation and maintenance [1]. The development of innovative treatment processes for low and intermediate level wastes (LLW and ILW) in recent times has focused on volume reduction as one of the main objectives [2]. During reprocessing of spent fuel, an optimized mixture of tri-n-butyl phosphate (TBP) and dodecane is used as an extracting agent for actinides. During their repeated use, solvent undergoes chemical/radiolytic degradation, loosing its efficiency and hence to be discarded as spent organic solvent waste. This waste is presently being treated by alkaline hydrolysis process where spent solvent is refluxed with concentrated sodium hydroxide solution at 110°C [3]. TBP component of the spent solvent waste gets hydrolyzed and is converted into sodium salt of di-butyl phosphate (DBP). The other products obtained during hydrolysis include sodium salt of mono-butyl phosphate (MBP), butanol and phosphoric acid. Dodecane component of the spent solvent waste does not take part in the hydrolysis reaction and appears as a clear phase. The dodecane waste thus separated is subjected for thermal destruction by incineration. The emulsified aqueous layer thus obtained retains most of the activity present in the spent solvent waste. The present paper describes experimental studies performed to look for various approaches for management of this type of waste.     

Colorimetric sensor for triphosphates and their application as a viable staining agent for prokaryotes and eukaryotes

The chromogenic complex 1 x Zn (where 1 is (E)-4-(4-dimethylamino-phenylazo)-N,N-bispyridin-2-ylmethyl-benzenesulfonamide) showed high affinity toward the phosphate ion in tetrabutylammonium phosphate in acetonitrile solution and could preferentially bind to adenosine triphosphate (ATP) in aqueous solution at physiological pH. This binding caused a visual change in color, whereas no such change was noticed with other related anions (adenosine monophosphate, adenosine diphosphate, pyrophosphate, and phosphate) of biological significance. Thus, 1 x Zn could be used as a staining agent for different biological cells through binding to the ATP, generated in situ by the mitochondria (in eukaryotes). For prokaryotes (bacteria) the cell membrane takes care of the cells' energy conversion, since they lack mitochondria. ATP is produced in their unique cell structure on the cell membrane, which is not found in any eukaryotes. These stained cells could be viewed with normal light microscopy. This reagent could even be used for distinguishing the gram-positive and the gram-negative bacteria (prokaryotes). This dye was found to be nonlipophilic in nature and nontoxic to living microbes (eukaryotes and prokaryotes). Further, stained cells were found to grow in their respective media, and this confirmed the maintenance of viability of the microbes even after staining, unlike with many other dyes available commercially.     

Time-resolved fluorescence polarization dynamics and optical imaging of Cytate: a prostate cancer receptor-targeted contrast agent

Cypate-octreote peptide analogue conjugate (Cytate) was investigated as a prostate cancer receptor-targeted contrast agent. The absorption and fluorescence spectra of Cytate were ranged in the near-infrared "tissue optical window." Time-resolved investigation of polarization-dependent fluorescence emitted from Cytate in solution as well as in cancerous and normal prostate tissues was conducted. Polarization preservation characteristics of Cytate in solution and tissues were studied. Fluorescence intensity emitted from the Cytate-stained cancerous prostate tissue was found to be much stronger than that from the Cytate-stained normal prostate tissue, indicating more Cytate uptake in the former tissue type. The polarization anisotropy of Cytate contained in cancerous prostate tissue was found to be larger than that in the normal prostate tissue, indicating a larger degree of polarization preservation in Cytate-stained cancerous tissue. The temporal profiles of fluorescence from Cytate solution and from Cytate-stained prostate tissue were fitted using a time-dependent fluorescence depolarization model. The photoluminescence imaging of Cytate-stained cancerous and normal prostate tissues was accomplished, showing the potential of Cytate as a fluorescence marker for prostate cancer detection.     

Cluster formation in Ag2O-P2O5-CdCl2 glass system

Ag₂O-P₂O₅ and Ag₂O-P₂O₅-20 wt% CdCl₂ glasses were prepared by melt quenching method and characterized with the help of several experimental techniques. Powder X-ray diffraction study indicated that the glasses are amorphous in nature. DSC studies showed that CdCl₂ doped glass is chemically more durable. Electrical conductivity and ionic transference number measurements have shown that both the glasses are ionic conductors with Ag⁺ ions as the charge carriers. The electrical conductivity of the doped glass is found to be higher than the undoped one. Structures of the glasses have been proposed on the basis of IR spectral analysis. From SEM studies it has been inferred that addition of 20 wt% CdCl₂ modifies the morphology of Ag₂O-P₂O₅ glass and in its presence formation of clusters composed of nanofibers occur.