Indian Journal of

The effect of radiative transfer on Rayleigh-Benard convection in a fluid-saturated porous layer is studied using Goody’s approach. The Milne–Eddington approximation is employed in obtaining the initial static state and linear stability analysis is performed. An equivalent single-phase two-flux model is used in deriving the equation of heat transport for transparent and opaque media. The critical Rayleigh number is obtained by the Galerkin method and radiation is shown to stabilise the system for both the transparent and opaque media. It is found that the opaque media releases heat for convection more slowly than transparent media. Radiation is shown to affect the cell size in the case of transparent media only. The results of the problem have applications in heat engine containing fluid saturated-packed bed which works on the regenerative cycle.

Indian Journal of Engineering & Materials Sciences

Vol. 9, June 2002, pp. 172-176

High efficient contamination free clean heat production

Pradip Kumar Sadhu^a, Sanat Kumar Mukherjee^a, Rupendranath Chakrabarti^b, Shamapada Chowdhury^b,Bhuwan Mohan Karan^a, Rajesh Kumar Gupta^a & C V S C Reddy^a

The present investigations relate to the process of electromagnetic induction heat flow through metallic package (stainless steel) in glass pipeline or vessel. The inverter fed fluid heating appliance is more acceptable than gas combustion, steam heating and electrical resistive heating methods for better heat transfer and delivery processing under precise temperature management. This technology has been found to improve heat energy storage and heat exchange processing of tank fluid heating in the container or vessel or pipeline directly. The other advantages are: contamination-free heat production, good compactness, high reliability, quick response, absence of combustion waste and shock hazards in the boiling vessel. Besides, enrouting water through specially designed metallic assemblies will permit eddy-current based heating through electromagnetic induction. In the case of steel vessel plant, heat can be generated directly on the vessel without heat conduction loss. The series-resonant constant-frequency PWM IGBT inverter system has been introduced as a new conceptual induction-heated pipeline fluid or vessel fluid heating for medicinal plant, sterilization plant and drier for surgical instruments.

Indian Journal of Engineering & Materials Sciences

Vol. 9, June 2002, pp. 177-180

Gasification of Nigerian bituminous coal in shallow bed

J Soji Adeyinka^a* & F O Akinbode^b

Gasification experiment was carried out on Lafia Obi Bituminous (LOB) coal grades of Nigeria. Adiabatic carbon boundary condition was investigated using reduce coal-air feed ratio to evaluate coal conversion. CO:CO₂ gas yield followed coal property with increasing CO production at lower air-feed ratio; it was also observed that air distribution into the freeboard improved conversion and CO yield reducing CO₂ production. Thermal analysis of the gasification showed possibility of using excess heat from the hot bed zone to convert CO₂ in the freeboard.

Indian Journal of Engineering & Materials Sciences

Vol. 9, June 2002, pp. 181-186

Kinetics of wet versus dry grinding of lignite by a porcelain mill

A Ozkan & M Yekeler*

The kinetics of dry versus wet grinding of several feed size fractions of lignite in a laboratory size porcelain mill are reported here using feed fractions prepared to –600+425, –425+300 and –300+212 µm mono-sizes. The kinetics process is first-order up to 8 min for dry grinding while it is first-order up to 16 min for wet grinding. However, the specific rates of breakages decrease as feed sizes decrease for both dry and wet grinding. Rates of breakage (S_i) of wet grinding are found to be consistently higher than those of the dry values. The dry B_i,j rates are also g=1.58, f=0.58 and b=7.11, as the wet values obtained to be g=1.45, f=0.63 and b=6.45. The breakage parameters, therefore, indicate that wet grinding in a porcelain ball mill is more efficient to get finer product sizes. The simulated product size distributions of both dry and wet grinding are in good agreement with the experimental product size distributions using a standard ball mill simulation program.

Indian Journal of Engineering & Materials Sciences

Vol. 9, June 2002, pp. 187-190

preparation of aluminium-zirconium master alloys

J M Juneja

Preparation of Al-Zr master alloys was investigated by aluminothermic reduction of zirconium oxide (ZrO₂) using sulphur (S)-based slags. The influences of process variables such as requirement of heat energiser (KClO₃+ Al), amount of aluminium (Al) reductant, slag compositions, etc. were investigated to establish conditions for good slag-alloy separation and also to get optimum recoveries of the alloy. A maximum recovery of 92.8% Al-Zr alloy was obtained for a charge containing 20% excess aluminium over stoichiometric requirement, 50 g KClO₃, and 99 g S per 100 g ZrO₂. The alloy, on chemical analysis, was found to contain 33.74 wt% Zr, 0.4wt% oxygen, 0.0035 wt% nitrogen and 0.5 wt% S.

Indian Journal of Engineering & Materials Sciences

Vol. 9, June 2002, pp. 191-193

Effect of pre-formation of LB arachidic acid film on the structure of barium arachidate by exchange reaction

S D Sathaye*, D V Paranjape & K R Patil

The effect of subphase pH and the presence of exchangeable ions in subphase before and after arachidic acid monolayer formation is studied. It is found that introduction of exchangeable Ba⁺⁺ ions introduced in the subphase after arachidic acid film formation facilitates barium arachidate film formation via cation exchange reaction with good structural feature as revealed by X-ray diffraction and X-ray photoelectron spectroscopy. The barium arachidate film formation is supported by X-ray photoelectron spectroscopic studies while XRD reveals the c-axis oriented nature of the films.

Indian Journal of Engineering & Materials Sciences

Vol. 9, June 2002, pp. 194-196

Barnacle cleanship by simple chemical treatment

P G K Murthy, Reji John, K V Sanil Kumar & G V Krishna Kumar

The transducer assembly of the Acoustic Doppler Current Profiler (ADCP) is installed on the ship's hull directly exposing it to sea water. Consequently, the barnacles deposit and grow on and around the transducers. Conventional barnacle cleaning techniques could not be adapted in this case due to sensitive nature of the polyurethane cover (around the transducers) to the mechanical impacts. So, a simple chemical method is tried to remove the barnacle deposits. The transducers are immersed in dilute HCl of 3 N for dissolving the barnacles. The roots of the barnacles are removed with a rush, and the oily films are cleaned by soaking the transducers in soapy water. The transducers are finally washed with fresh water.

Indian Journal of Engineering & Materials Sciences

Vol. 9, June 2002, pp. 197-202

Conducting polymeric products from metal powder-filled castor oil-based polyurethanes

Anil Srivastava^a, R C Chauhan^a& Paramjit Singh^b

In the present studies, the polyurethanes were prepared by reaction between low cost vegetable oil, i.e., castor oil and its polyols and toluene 2,4-di-isocyanate. The fine metal powders, i.e., aluminum and graphite of 200 mesh size were dispersed in the castor oil and its based polyols before preparation of polyurethane pre-polymer. The pre-polymers of polyurethanes achieved by these methods were reacted by vinyl monomer followed by in-situ polymerization technique. Powder filled composites were prepared by compression molding technique. The composite specimens prepared by these methods were characterized for volume resistivity and surface resistivity to find out electrical conductivity. The products are expected to find suitable application as floor-tiles in the areas, where electrostatic charges are of great concern; conducting coatings, adhesives for electrical industries and junction boxes, panels particularly in the areas of EMI and RFI concerned.

Indian Journal of Engineering & Materials Sciences

Vol. 9, June 2002, pp. 203-208

Abrasive wear of glass fibre reinforced polysulfone composites

A P Harsha & U S Tewari*

Abrasive wear behaviour of polysulfone (PSU), an amorphous, brittle and high temperature engineering thermoplastic material, and its composites were investigated by using pin-on-disc machine against silicon carbide (SiC) abrasive paper under multipass conditions. Abrasive wear studies were conducted under various testing conditions such as sliding distance, load, velocity, and abrasive grit size. It was observed that neat PSU showing better wear performance than glass fibre reinforced PSU in most of the experimental conditions. These results may be attributed to the reinforcement, greatly reducing ultimate elongation to fracture, which in turn is key factor in abrasive wear performance. Worn sample surfaces were studied with Scanning Electron Microscopy (SEM).

Indian Journal of Engineering & Materials Sciences

Vol. 9, June 2002, pp. 209-212

Tribology and tribochemistry of oil soluble methylene-bis-[dialkyl/alkylaryl-
dithiocarbamates] as potential EP additives

V K Verma, R Singh, Vandana Srivastava & P K Singh

A number of blends of methylene-bis-[N,N-dialkyl/alkylaryl dithiocarbamates] in paraffin oil (0.5% w/v) were evaluated for their anti-wear, EP and friction reducing tribological properties by employing 12.7 mm diameter low carbon and chromium bearing ball specimen in a four ball test. All the additives were found to decrease wear and friction to appreciable levels and increase the load carrying capacity to very high values. In particular, the additive methylene-bis-[morpholino-dithiocarbamate] was instrumental in exhibiting lower values of wear scar diameter and coefficient of friction at lower as well as higher loads and high load carrying capacity, load wear index and flash temperature parameter values in comparison to plain paraffin oil and a reference additive. The additives also afforded lower values of wear-scar diameter in one-hour wear test. The topography of the used bearing ball specimen was investigated by scanning microscopy technique.

Indian Journal of Engineering & Materials Sciences

Vol. 9, June 2002, pp. 213-217

New condensation products as corrosion inhibitors for mild steel in
hydrochloric acid medium

S K Rajappa & T V Venkatesha*

The corrosion behaviour of mild steel in 2M hydrochloric acid solution containing various concentrations of condensation products formed from glutaraldehyde + glycine (CP1) and glutaraldehyde + methionine (CP2) has been investigated using weight loss measurement and galvanostatic polarization technique. The percentage of inhibitor efficiency varies with immersion time, inhibitor concentration and temperature. The condensation product CP2 shows better inhibition than CP1. The effect of temperature on corrosion of mild steel has been studied by polarization measurement at various temperatures [298, 308, 318 & 338 K] in the absence and presence of inhibitors.

Indian Journal of Engineering & Materials Sciences

Vol. 9, June 2002, pp. 218-222

Inhibition of corrosion of mild steel by nitrite in aqueous solution in presence of aggressive ions

Rita Mehra & Aditi Soni

The potentiality of sodium nitrite as corrosion inhibitor for mild steel in aqueous solution of sodium chloride and magnesium sulphate, containing nitrite as inhibitor is reported here. The inhibition appears to function through general adsorption on the surface of mild steel. The thermodynamic parameters such as activation energy, heat of adsorption and free energy of adsorption have been calculated to determine the mechanism of adsorption of the inhibitor. Along with, potentiostatic parameters, viz. open circuit potential (OCP), corrosion potential (E_corr), corrosion current (I_corr) Tafel slopes and corrosion rate have also been determined.

Indian Journal of

VOLUME 9 NUMBER 3 JUNE 2002

CONTENTS

Engineering

Materials Science