HEAT TRANSFER IN MULTIPHASE CONTACTORS

A procedure for the prediction of wall-bed heat transfer coefficient for bubble columns and gas-solid fluidized beds is developed on the basis of hydrodynamic behavior of these contactors. A comparison between the predicted and experimental values of heat transfer coefficient over a wide range of design and operating variables is presented. An attempt is made to analyze the occurrence of maxima in heat transfer coefficient with respect to gas velocity in the case of fluidized beds. A procedure for the calculation of the optimum superficial gas velocity is outlined.     

Effects of Microwave Heating and Gamma Irradiation on Phytate and Phospholipid Contents of Soybean (Glycine max. L.)

The effect of microwave heating and gamma irradiation treatments on phosphorus compounds of soybean seeds were studied. Inorganic phosphorus was significantly (P < 0.05) increased while, phytate and phospholipids were significantly decreased when soybean seeds were microwave-heated for 9 min or more. Furthermore, gamma-irradiation treatments of 20 KGy or more significantly increased inorganic phosphorus and decreased phytate and phospholipids of the beans. Two dimensional thin-layer chromatography was employed to study the phospholipid pattern. Gamma-irradiation at doses from 40 to 100 KGy produced lysophosphatidylcholine and phosphatidic acid. The data of this study showed that, the increase of inorganic phosphorus was mainly due to the decomposition of phytic acids and phosphates of inositol.     

Kinetics of Water Sorption by Soybean and Pigeonpea Grains

Kinetics of liquid water sorption by soybean (Glycine max) and pigeonpea (Cajanus cajan) seeds was studied at several temperatures. The data could be accurately correlated in terms of an empirical model involving a single rate constant. The temperature dependence of the rate constant followed Arrhenius relation. Swelling of grains due to water sorption was slightly less than the volume of water imbibed. This loss related to the energy of activation of the water sorption process.     

A RESEARCH NOTE CHEMICAL CHANGES IN HELIANTHUS ANNUUS AND EUCALYPTUS LANCEOLATUS HONEY DURING STORAGE

A comparison between changes in hydroxymethylfurfural, pH, total acidity and free acids content in Helianthus annuus and Eucalyptus lanceolatus honey heated under different conditions during storage was made. Storage duration showed the most pronounced effect on hydroxymethylfurfural content followed by temperature and heating duration for both types of honey. Total acidity and free acids content was higher in Helianthus annuus honey than in Eucalyptus lanceolatus honey. Total acidity and free acids content increased and pH decreased in both the honey types during heating and storage. However, storage duration showed the most pronounced effect on these parameters.     

Utilization of alkali-activated copper slag as binder in concrete

This study was focused on developing concrete using alkali-activated copper slag (AACS) as a binder. The properties of alkali-activated copper slag concrete (AACSC) were compared with portland cement concrete (PCC). Different AACSC mixes were prepared with varying Na₂O dosage (6% and 8% of the binder by weight) and curing methods. Hydration products in AACSC were retrieved using Fourier-transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD) techniques. The test results indicate that the workability of AACSC was lesser than that of PCC. The AACSC mix with 6% Na₂O dosage has exhibited similar mechanical properties as that of PCC. The mechanical properties of AACSC were higher than PCC when 8% of Na₂O dosage was used. Heat curing was effective to upgrade the strength properties of AACSC at an early age of curing, but at a later age mechanical properties of ambient cured and heat-cured AACSC were comparable. The hydration products of AACSC were not identified in XRD patterns, whereas, in FTIR spectra of AACSC some alkali-activated reaction products were reflected. The AACSC mixes were found to be more sustainable than PCC. It has been concluded that AACSC can be produced similarly to that of PCC and ambient curing is sufficient.     

EFFECT OF HOMOGENIZATION PRESSURE ON CONSISTENCY OF TOMATO JUICE 1

Pressurized homogenization of tomato juice at room temperature (28C) leads to an increased consistency and reduced serum separation in the juice. Percentage increase in consistency (as measured by Libby's tube) of hot processed juice from different cultivars ranged from 95 ± 3 to 282 ± 13 s. The magnitudes of change in consistency and serum spearation of cold processed juice due to homogenization were smaller than those for hot processed juice. Increases in consistency of cold processed juice ranged from 42 ± 4 to 213 ± 10 s. Consistency in all the samples increased with increasing pressure of homogenization up to a pressure of 3000 psi, above which it became constant. Homogenization of juice at higher temperature resulted in a very small increase in consistency. However, the magnitude of increase in consistency decreased with increasing temperature. Serum separation slightly increased at higher pressure of homogenization, after reaching a minimum with increasing pressure initially. In general, the juice with higher initial efflux and serum viscosities showed a larger increase in consistency and greater reduction in serum separation.     

Oil Absorption and Sensory Properties of a Snack Food from Chickpea Genotypes

Among the commonly consumed grain legumes the score on general acceptability of a snack food (seviya) was the highest for that from chickpea (Cicer arietinum L.) followed by lentil, pigeonpea and green gram, whereas the oil absorption by the product was highest for lentil followed by black gram, chickpea, and green gram. Different methods of dehulling did not cause any notable effects on oil absorption of chickpea seviya. The flour particle size, starch, and protein contents significantly influenced oil absorption of seviya. The oil absorption of the product differed significantly among genotypes, but clear cut differences were not found between desi and kabuli groups of chickpea genotypes.     

APPLICABILITY OF ALGINATE ENTRAPPED YEAST CELLS FOR THE PRODUCTION OF LACTOSE-HYDROLYZED MILK

To overcome the problem of enzyme extraction and poor permeability of cell membrane to lactose, permeabilized Kluyveromyces marxianus NCIM 3465 cells as a source of β‐D‐galactosidase were employed for the production of lactose‐hydrolyzed milk. In view of the advantages of an immobilized cell system over a free cell system, the yeast cells were entrapped in alginate gel for their subsequent use in lactose hydrolysis. Different process parameters (alginate concentration, bead size, biomass load, temperature, agitation and incubation time) were monitored to enhance lactose hydrolysis in milk. Maximum lactose hydrolysis (87.9%) was observed with yeast cells immobilized in 2% (w/v) alginate concentration with a bead size of 2.90 mm at 30C under agitation (80 rpm) after 150 min of incubation. The developed system was highly stable and the alginate entrapped yeast cells can be recycled up to the eight cycle without any marked change in their ability to carry out the lactose hydrolysis.     

Structural characteristics of titanium coating on copper substrates

The growth characteristics of titanium films deposited on glass, silicon (100) and oxygen free high purity copper substrate using magnetron sputtering have been investigated using X-ray diffraction, electron microscopy and scratch indentation techniques. The study of interface between the titanium film and the substrate was carried out to determine coating thickness, as well as intermixing of the elements at the interface. Studies revealed that the interface is free from voids and intermixing of the film and the substrate. Microstructural and diffraction analysis showed that the Ti coating was polycrystalline and exhibited columnar growth. The Ti crystallite size varied between 24 and 58 nm depending on the substrate. The thickness of the films were typically about 4 μm. Scratch test indicated that the films are adherent and the first critical load to failure was observed to be 4·5 N ± 2 N.     

PERFORMANCE AND ANALYSIS OF CHOPPER FED D.C. SEPARATELY EXCITED MOTOR UNDER REGENERATIVE BRAKING

Abstract

A method is presented here to analyse the performance of a separately excited d.c. motor under regenerative braking mode and provides a technique to select the necessary inductance to reduce the ripple in the armature current as well as to eliminate the discontinuous conduction of the armature current and to optimize the regenerative power. The effect of armature reaction and also that of chopper commutation interval have been taken into account. The calculated performance agrees very closely with the experimental results.