Showing papers in "Indian journal of technology in 1992"

Sound absorbing double curtains from local textile materials

Abstract: A new sample made of local textile material (100% cotton) (Misr Spinning and Weaving Company, Mehalla El Kubra) is produced from a specially woven structure which possesses high porosity for use as a sound absorbing curtain. A double-layered curtain was designed for high efficiency, not only in sound absorption, but also light insulation. One layer was made of 100% cotton, while the other was made of cotton/polyester 35:65. The two layers are separated by an air space, which is varied to obtain a construction of optimum effectiveness. Using the standing wave apparatus (Bruel and Kjaer type 4002), the sound absorption coefficient α of such samples was measured at normal sound incidence. The effect of air space, behind and/or between the layers of curtain, on the absorption coefficient has been studied in order to achieve the best construction for a specific application.

Calorimetric measurements of heat capacities and heats of mixing in the range 300-570 K and up to 30 MPa

Abstract: Two Setaram C-80 calorimeters have been used to measure heats of mixing and heat capacities of fluids, liquids as well as gases, from ambient temperature to 570K and in the pressure interval 0.1 to 25 MPa. The heats of mixing technique uses a flow method with an active heat exchanger; the heat capacities are measured in the static mode. Details and performances of the two methods are given and results are reported for the heats of mixing of tetrachloromethane + benzene and of carbon dioxide + toluene, and also for heat capacities of argon, methane and n-hexadecane

The conversion of ethanol to hydrocarbons over ZSM-5

Abstract: The influence of incorporating Zn and Ga in ZSM-5 on the catalytic transformation of ethanol into hydrocarbons has been investigated. Under the conditions of this study, considerable amount of hydrocarbons boiling above 423 K are produced over the catalysts. The incorporation of Zn and Ga in ZSM-5 increases its life considerably apart from increasing the yield of the liquid products. Further, the Zn- and Ga-catalysts produce more aromatics and less olefins.

Kinetics and morphological studies of silver cementation on copper single crystals in acidic medium

Abstract: The kinetics of Cu dissoln. and rate of cementation of Ag on Cu single crystals was studied. The deposit morphol., dissoln. rate of Cu and displacement rate of Ag were a function of crystallog. orientation, activity of depositing, agitation, temp. and pH of the medium. The order of cementation rate of Ag was (110) > (100) > (111) due to the anisotropic nature of single cryst. Cu. The reaction is chem. controlled in the initial stages of cementation and becomes diffusion-​controlled for prolonged immersion period. The rates conform to first order kinetics. Surface topog. of Ag deposited on Cu single crystal planes was obsd. Triangular and hexagonal pyramids appear on (111) plane of Cu while cubic pyramids and rectangular blocks were obsd. on (100) and (110) planes. Epitaxial displacement are indicated when the rates were chem. controlled. When displacement was diffusion-​controlled, no regular growth features on all the planes was obsd. The mechanism and kinetics of the cementation process are reported.

Excess molar volumes and viscosities of ten binary and four ternary liquid mixtures

Abstract: Densities and viscosities of ten binary and four ternary mixtures containing bromoform, bromobenzene, chlorobenzene, toluene, 1,3,5-trimethylbenzene and dimethylformamide at 30,35 and 40°C have been measured. Excess molar volumes, apparent values of excess molar viscosities and excess molar Gibbs energy of activation of flow have been calculated for both the binary and ternary mixtures. The results of ternary excess molar volumes have been analysed by using the theoretical models suggested in the literature. The calculated excess quantities have been discussed in terms of the nature of binary and ternary interactions

Theoretical performance of metallized unsymmetrical dimethylhydrazinered fuming nitric acid propellant system

Abstract: The theoretical performance of gellet and ungelled unsymmetrical dimethylhydrazine (UDMH)-red fuming nitric acid (RFNA) liquid bipropellant systems has been evaluated over a wide range of oxidizer-fuel ratio. The performance losses due to addition of chemical gelling agents like methyl cellulose (MC) and agar-agar (AA) in the fuel and overall gains on metallization (Al and Mg) up to 50 wt% in specific impulse have been assessed. The variation of density-specific impulse for equilibrium and frozen flow conditions with different metal loading in the fuel gel using RFNA oxidant has been computed. The specific impulse (I sp ) has been found to increase with the equivalence ratio (ER), defined as fuel to oxidizer ratio/stoichiometric mixture ratio, to attain a maximum value at a given ER which varies as a function of propellant composition. The optimum I sp for all compositions investigated correspond to fuel rich systems with respect to stoichiometric condition. The results show a significant gain in equilibrium I sp with increasing metal powder (Al and Mg) loading up to 40 wt% of Al and 30 wt% of Mg content in the gelled fuel. The study also indicates that oxidizer requirement for metallized fuels corresponding to maximum equilibrium I sp is drastically curtailed to the extent of 65.83% and 61.90% in case of 40 wt% Al and Mg content respectively in comparison to the patent bipropellant system

Microcalorimetric investigations of oscillating reactions-instrumental approach and some results

Abstract: Four examples of oscillating chemical reactions are presented: the Belousov-Zhabotinskii (BZ) reaction, the Briggs-Rauscher (BR) reaction, some examples of uncatalyzed (ABA) reactions with aromatic compounds, bromate and acid, and periodic reactions during glycolisis in cytoplasmic extracts from yeast. All reactions were monitored by means of isoperibolic batch and flow calorimeters. Special calorimetric set-ups for simultaneous recording of changes in spectrophotometric absorption, electrical potential and in pressure are described. We underline that microcalorimetry is an appropriate and promising tool to study processes periodic in time

Effect of fin height on heat transfer during condensation of R-11 on horizontal integral-fin tubes

Abstract: An experimental study to measure the condensing side heat transfer coefficient during film condensation of pure saturated R-11 vapour on single, horizontal, integral-fin tubes is reported.

An experimental study on packing and drift eliminators in an evaporative condenser with induced draft

Abstract: The pressure drop and drift loss characteristics of cement asbestos dift eliminators (CADE), concrete drift eliminators (CDE) and cellular type drift eliminators (CTDE) in an evaporative condenser (EC) were experimentally investigated. For CADE and CDE, data were taken for various number of stages, n and for a range of the orientation angle,theta of the eliminator plates. For CTDE, the data were recorded for various values of n and the air velocity through a drift eliminator stage. The results showed that the pressure drop and drift were strong function of n and air flow rate. In case of CADE and CDE, they were strongly dependent on theta as well. A cellular type packing placed inside the EC was also studied experimentally ans its volume transfer coefficient was correlated in terms of the ratio of liquid to air loading.

Applications of calorimetry (macro and micro) to the study of host-guest interactions in solution

Abstract: Some of the applications of calorimetry (macro and micro) to the study of host-guest interactions in solution are described. These include: (1) complexation reaction involving neutral macrocyclic ligands (cryptands, calixarene esters and cyclodextrins) and different guest substrates and (2) solution and transfer enthalpy data for the host, guest and the resulting complex in different solvent systems. The advantages of microcalorimetry with respect to standard macrocalorimetry are illustrated with a variety of examples arising from limitations encountered with the latter technique in the course of these investigations

A method of estimating the standard heat of formation using molar refraction

Abstract: Standard heat of formation (ΔH f0 ) has been linearly correlated to the molar refraction (R M ). The linear equations, applied to the data on 9 series of hydrocarbons at 216 compounds, yielded correlation coefficients ranging between 0.8673 and 0.9998, implying strong relationship between ΔH f 0 and R M . The prediction capability of the method has been found to be comparable to some of the methods reported in recent literature