Effect of corrugation frequencies on natural convective heat transfer and flow characteristics in a square enclosure of vee-corrugated vertical walls

A numerical investigation has been carried out on natural convective heat transfer and fluid flow in a square cavity with vee-corrugated vertical surfaces. This study covers the range of corrugation frequency from 1 to 3 and Grashof number from 10³ to 10⁵. The corrugation amplitude has been fixed at 5% of the enclosure height. The vorticity stream function formulation with the control volume based finite element method has been used to analyse the effects of corrugation frequency and Grashof number. The investigation shows that the overall heat transfer through the enclosure increases with the increase of corrugation for low Grashof number; but the trend is reversed for high Grashof number.     

Briquetting of palm fibre and shell from the processing of palm nuts to palm oil

Malaysia is the major producer of palm oil in the world. It produces 8.5 million tonnes per year (8.5×10⁶ ty⁻¹) of palm oil from 38.6×10⁶ ty⁻¹ of fresh fruit bunches. Palm oil production generates large amounts of process residues such as fibre (5.4×10⁶ ty⁻¹), shell (2.3×10⁶ ty⁻¹), and empty fruit bunches (8.8×10⁶ ty⁻¹). A large fraction of the fibre and much of the shell are used as fuel to generate process steam and electricity in the palm processing mill itself. However, much is wasted by pile burning in the open air with attendant air pollution, dumped in areas adjacent to the mill, or utilized as manure in the palm oil plantation. In this paper, an attempt has been made to convert these residues into solid fuel. The palm shell and fibre is densified into briquettes of diameter 40, 50 and 60 mm under moderate pressure of 5–13.5 MPa in a hydraulic press. Experiments are carried out to determine density, durability, impact and compressive strength of the briquettes. The heating value, burning characteristics, ash and moisture content are other objects of the study. A relationship between press pressure and the briquette density has been established. The produced briquettes have densities between 1100 and 1200 kgm⁻³. The briquettes properties are quite good with good resistance to mechanical disintegration, and will withstand wetting. The gross calorific value is about 16.4 MJkg⁻¹ (maf), and the ash content is about 6% and the equilibrium moisture content is about 12%. Further work is required to acquire complete understanding of the densification process before good quality and durable briquettes could be made free from cracks.     

The nature of the oxygenated fatty acids present in Malva parviflora seed oil

The seed oil of Malva parviflora L. (Malvaceae) is known to contain glycerides of cyclopropene (malvalic and sterculic), cyclopropane (dihydromalvalic and dihydrosterculic), epoxy, and conjugated dienol acids. By preparative thin layer chromatography, the epoxy and conjugated dienol acids were isolated as their methyl esters. These were characterised as cis-12, 13-epoxy-cis-9-octadecenoic (vernolic) acid, and 13-hydroxy-cis-9, trans-11-octadecadienoic (coriolic) acid.     

Dielectric behavior of insulating materials under liquid nitrogen

Measurements were made to assess the AC breakdown voltages in liquid nitrogen (LN/sub 2/) with different electrode configurations such as sphere-sphere, needle-needle, hemisphere-hemisphere, plane-plane, sphere-needle, etc. Experimental results reveal that the breakdown voltage is a function of electrode geometry and gap length. This study also addresses the effect on the breakdown strength of solid insulating materials under LN/sub 2/ environment with a sphere-sphere electrode configuration. In this paper, special emphasis has been attributed to the effect on loss index of a variety of dielectrics dipped in LN/sub 2/. The measured values of breakdown strength and loss index have been compared with those obtained under atmospheric condition. The study reveals that the breakdown strength of cellulosic materials like paper or pressboard increases manifold while the loss index decreases significantly when dipped in LN/sub 2/ with variations of the order of 50% to 90%. However, for impervious noncellulosic materials like Perspex (acrylic glass) or presspahn, the increase in breakdown strength is not that pronounced and the decrease in loss index is of the order of 2 to 30%.     

Four-quadrant and zero-speed sensorless control of a switched reluctance motor

A four-quadrant sensorless controller for switched reluctance motor (SRM) drives is presented in this paper. The drive system with appropriate turn-on and turn-off angles for each operating quadrant delivers excellent dynamic performance over a wide speed range including zero speed. The problems associated with practical implementation especially at low and zero speeds have been addressed and overcome with engineering solutions. Experimental results for a 1-kW SRM obtained on a dSPACE-based system are presented along with useful guidelines for practical implementation.     

Hibiscus sabdariffa Seed Oil: A Re-investigation

Due to controversial reports on the component acids of Hibiscus sabdariffa seed fat and in anticipation of the co-occurrence of cyclopropene and epoxy acids in the seed oils of Malvaceae (especially in the genus Hibiscus)⁵,⁶ it was considered worthwhile to re-examine the seed oil of H. sabdariffa. Seed oil of H. sabdariffa (Malvaceae) contains myristic (2.1%), palmitic (35.2%), palmitoleic (2.0%), stearic (3.4%), oleic (34.0%), linoleic (14.6%) and three unusual HBr-reacting fatty acids. These acids are cis-12,13-epoxy-cis-9-octadecenoic (12,13-epoxyoleic), 4.5 %; sterculic, 2.9%; and malvalic, 1.3%. Acetolysis of epoxide in the presence of cyclopropenes was effected by room temperature treatment with acetic acid-10% sulphuric acid. Seed oils of Vernonia anthelmintica and Sterculia foetida were used as reference standards.     

Exploration and optimization of a homogeneous tree-based application specific inflexible FPGA

An Application Specific Inflexible FPGA (ASIF) is a modified form of an FPGA which is designed for a predefined set of applications that operate at mutually exclusive times. An ASIF is a compromise between FPGAs and Application Specific Integrated Circuits (ASICs). Compared to an FPGA, an ASIF has reduced flexibility and improved density while compared to an ASIC, it has larger area but improved flexibility. This work presents a new homogeneous tree-based ASIF and uses a set of 16 MCNC benchmarks for experimentation. Experimental results show that, on average, a homogeneous tree-based ASIF gives 64% area gain when compared to an equivalent tree-based FPGA. Further, the experiments are performed to explore the effect of look-up table (LUT) and arity size on a tree-based ASIF. Later, comparison between tree and mesh-based ASIF is performed and results show that tree-based ASIF is 12% smaller in terms of routing area and consumes 77% less wires than mesh-based ASIF. Finally the quality comparison between two ASIFs reveals that, on average, tree-based ASIF gives 33% area gain as compared to mesh-based ASIF.     

Landfarming operation of oily sludge in arid region--human health risk assessment

Landfarming is becoming one of the most preferred treatment technologies for oily sludge disposal in the Arabian Gulf region in general, and in the Kingdom of Saudi Arabia in particular. This technology is considered to be, economical, energy efficient, and environmentally friendly with minimal residue disposal problems. Application of this technology in the region is simply based on the studies conducted in the United States of America and Europe. There have hardly been any scientific studies conducted to evaluate performance of landfarming technology under arid conditions. Recently, detailed field experimental study has been conducted to evaluate the degradation process and health risk issues in landfarming under arid conditions. The study observed volatilization as the main process of hydrocarbon degradation, which can cause significantly high concentration of airborne volatile organic compounds (VOCs) in the atmosphere leading to serious human health risk to the onsite workers. It is particularly true in the early phase of the landfarming process (first 2 months from initial loading). This paper elaborates these findings in detail.     

Field emission of MWCNTs/PANi nanocomposites prepared by ex‐situ and in‐situ polymerization methods

The present work describes the field‐emission properties of multiwalled carbon nanotubes (MWCNTs) coated with conducting polymer polyaniline (PANi). MWCNTs/PANi nanocomposites have been prepared by ex‐ situ polymerization methods and inex‐ situ chemical polymerization and are analyzed by SEM and Raman spectroscopy. It is fairly clear from SEM images that PANi is coated on the surface of MWCNT. SEM image of PANi powder also shows that the powder obtained is PANi nanofibers. It is also observed from SEM images that the shell diameter of MWCNTs depends on PANi content in thenanocomposites. The average outer diameter of MWCNTs increases from 7–15 to 50–80 nm upon PANi coating. Field‐emission study shows that although there is decrease in the value of turnex‐on field E_to and increase in the value field enhancement factor β of the nanocomposites as we go from direct solid‐state mixing method to inex‐ situ chemical polymerization method, the parameters obtained by inex‐ situ polymerization chemical method shows superior field emission. The turn‐on field of the nanocomposites are between 2.5 and 4.5 V/μm and the field enhancement factors are significantly high, between 1.2 × 10³ and 9.2 × 10³ while. PANi nanofibers does not show any field emission. POLYM. COMPOS. 34:1298–1305, 2013. © 2013 Society of Plastics Engineers