Journal of Modeling, Design and Management of Engineering Systems

Evaluation of journal bearings characteristics using finite element method

A Aiad

Dynamic behavior of the rotor-bearings system exerts a considerable
influence on rotating machine operating and stability. Indeed, vibrations in
such machines may cause not only high level of noise but also wearing of
moving components. Hydrodynamic journal bearings, which are among the
best devices to prevent contacts between rubbing surfaces, are analyzed in
the present study by considering dynamic effects due to flexibility of the
lubricant fluid film. The finite element method is used to numerically
evaluate stiffness and damping coefficients of the fluid film and applications
concern performances of finite length and aligned journal bearings. Results
are compared with those obtained by an alternative method and show good
agreement.

Keywords: Journal bearings, Dynamic characteristics, Finite element

Numerical investigation of heat transfer in Plastic Leaded Chip Carrier (PLCC) packages in in-line arrangement

M Mohamed

Plastic Leaded Chip Carrier (PLCC) package has been emerged a promising option to tackle the thermal management issue of micro-electronic devices. In the present study, three dimensional numerical analysis of heat and fluid flow through PLCC packages oriented in-line and mounted horizontally on a printed circuit board, is carried out using a commercial CFD code, FLUENTTM. The simulation is performed for three configurations such as 4PLCC, 8PLCC and 12PLCC under natural, mixed and forced convection modes with different inlet velocities and chip powers. The contours of average junction temperatures are obtained for each package under different conditions. It is observed that the junction temperature of the packages decreases with increase in inlet velocity and increases with chip power. Moreover, the increase in package density significantly contributed to rise in temperature of chips. Thus the present simulation demonstrates that the chip density (the number of packages mounted on a given area), chip power and the coolant inlet velocity are strongly interconnected; hence their appropriate choice would be crucial.

Keywords: PLCC package, Thermal management, Numerical simulation,
Average junction temperature

Modeling of 1-D nitrate transport in single layer soils

B.U Dike

There is increasing concern on environmental pollution especially potential of groundwater contamination by nitrates. The objectives therefore were to investigate the 1-D solute transport equation for single layer soil, calibrate, verify and apply model to field condition. The transport of nitrate in laboratory single soil columns of sand, laterite and clay were investigated after 21 days. The 1-D contaminant transport model by Notodarmojo et al (1991) for single layer soils were calibrated and verified using field data collected from a refuse dump site at avu, owerri, Imo state. The experimental distribution of nitrate along the sandy soil is linear with reduction rate of 0.44 ppm/cm, slightly exponential for laterite and clay with reduction rate of 0.136 ppm/cm and 0.24 ppm/cm respectively. The results show predicted transport was in close agreement with measured values with coefficient of correlation (R) ranging from 0.9 to 0.99. Application of the results in the prediction of possibility of pollution of groundwater was very promising.

Keywords: Contaminant transport, Nitrate, 1-D, column experiment

Exergy analysis of a gas turbine power plant

C.O.C Oko

Exergy analysis of a 100MW gas turbine power plant that works on the
Brayton cycle is presented. The average increase in the thermodynamic
degradation of the plant over the period of six (6) years at three different
levels of load was assessed. The exergy analysis of the plant was done on
two sets of data: one from the start-up report at the commissioning of the
plant and the other from the log sheets for operation of the plant in the
period considered. The later set of data was processed using statistical tools. The result shows that at full load, 259.216 MW of exergy is lost on the average, and that exergy loss is most prevalent in the combustion chamber, followed by the exhaust system, and is lowest in the compressor. Both the rational and thermal efficiencies of the plant reduce in value over the period considered, but not significantly. The fuel consumption rate also increased on the average by 0.24%.

Keywords: Exergy analysis, gas turbine power plant, irreversibility.

Adsorption studies on bleaching of palm-kernel oil with activated bentonite clay

E.L Viele

Adsorption studies were performed on bleaching of palm-kernel oil (PKO)
with different weight ratios of activated bentonite clay/PKO, ranging from
0.25% to 3% and at different temperatures of 70ºC, 80ºC, 90ºC and 100ºC. The equilibrium data generated were subsequently fitted with Langmuir and Freundlich adsorption models. The Freundlich equation parameters were calculated and the isotherms gave a better fit of the equilibrium data than the Langmuir equation. A study of the temperature effect on the adsorption showed that the isosteric heat of adsorption was a monotonically increasing function of adsorbent loading. Increase in adsorbent loading was found to increase the colour removal as temperature and adsorbent dosage are increased but became constant at increased loading.

Keywords: Adsorption isotherm, bleaching, Langmuir equation, Freundlich
equation, activated bentonite clay, palm-kernel oil.

Automation of a dust sampling train

A Akinola

The accuracy of measuring the concentration of particulate matter in flue gas streams by a dust sampling train can be significantly improved or minimized by automating the sampling process using a microprocessor based system. Two situations are presented here, in which a dust sampling train is interfaced via appropriate transducers with a microprocessor and additional circuit boards. The results obtained from this work show that the flue gas sampling process can be automated using microprocessor-based control system and a sampling train. Using the sampling train developed by the British Coal Utilization Research Association (BCURA) with both the internal and external flow-meter arrangements, the maximum error in iso-kinetic sampling velocity throughout the sampling period did not exceeding 5%.

Keywords: Automation, Dust Sampling, Iso-kinetic Sampling, Digital
control