Alireza Rahimi

Lattice Boltzmann method based on Dual-MRT model for three-dimensional natural convection and entropy generation in CuO–water nanofluid filled cuboid enclosure included with discrete active walls

Abstract In the present study, the three-dimensional natural convection and entropy generation in a cuboid enclosure included with various discrete active walls is analyzed using lattice Boltzmann method. The enclosure is filled with CuO–water nanofluid. To predict thermo-physical properties, dynamic viscosity and thermal conductivity, of CuO–water nanofluid, the KKL model is applied to consider the effect of Brownian motion on nanofluid properties. In lattice Boltzmann simulation, two different MRT models are used to solve the problem. The D3Q7-MRT model is used to solve the temperature filed, and the D3Q19 is employed to solve the fluid flow of natural convection within the enclosure. The influences of different Rayleigh numbers 1 0 3 R a 1 0 6 and solid volume fractions 0 φ 0 . 04 and four different arrangements of discrete active walls on the fluid flow, heat transfer, total entropy generation, local heat transfer irreversibility and local fluid friction irreversibility are presented comprehensively.

Entropy generation analysis and heatline visualization of free convection in nanofluid (KKL model-based)-filled cavity including internal active fins using lattice Boltzmann method

Abstract Two-dimensional natural convection and entropy generation in a square cavity filled with CuO–water nanofluid is performed. The lattice Boltzmann method is employed to solve the problem numerically. The influences of different Rayleigh numbers 1 0 3 R a 1 0 6 and solid volume fractions 0 φ 0 . 05 on the fluid flow, heat transfer and total/local entropy generation are presented comprehensively. Also, the heatline visualization is employed to identify the heat energy flow. To predict the thermo-physical properties, dynamic viscosity and thermal conductivity, of CuO–water nanofluid, the KKL model is applied to consider the effect of Brownian motion on nanofluid properties. It is concluded that the configurations of active fins have pronounced effect on the fluid flow, heat transfer and entropy generation. Furthermore, the Nusselt number has direct relationship with Rayleigh number and solid volume fraction, and the entropy generation has direct and reverse relationships with Rayleigh number and solid volume fraction, respectively.

Emission characteristics of oxy-fuel combustion of crude oil in a fluidized bed combustor

ABSTRACT One of the most important thermochemical methods for heat and electricity generation is combustion process; however, it has become a serious problem for researchers in the field of green chemistry due to high emissions and pollutants. In this paper, a modeling study of crude oil combustion was carried out based on the rate of reactions and combustor characteristics. To evaluate the potential of crude oil for heat and power generation, the influence of residence time of droplets and system pressure on greenhouse gas emissions was studied. Results obtained from model were validated against the experimental data of crude oil combustion and found to be in a good agreement.

Postural changes during first pregnancy.

Aims: The precise changes in postures of each part of the spine of primigravid women are still ambiguous. This study aimed to find out the spinal curvature and pelvic tilt changes during the first pregnancy. Study Design: Observational longitudinal study (Cohort study). Place and Duration of Study: The study was conducted at a hospital clinic in Iran, between April 2014 and December 2014. Methodology: Thirty primigravid women at the first, second and third trimesters of pregnancy were recruited in this cohort study and their lumbar and thoracic curves changes and pelvic inclination angles were studied and compared with 18 age-BMI matched non-pregnant women. The curves were measured by use of a flexible ruler and the pelvic inclination angle was measured by a pelvic inclinometer device. Before starting the main study, the reliability and repeatability of the measuring tools were confirmed in this study (ICC>0.87). A one-way ANOVA and independent tOriginal Research Article Kouhkan et al.; BJMMR, 7(9): 744-753, 2015; Article no.BJMMR.2015.384 745 test were used for statistical analysis. Results: Marked increased curvature and inclination angles were revealed as pregnancy advanced (P<0.05). The lumbar lordosis significantly increased when the first trimester was compared with the second and third ones. The thoracic curvature showed significantly increased curvature between the first and third and between the second and third trimesters. None of the lumbar or thoracic curve showed significantly difference between the control group and pregnant women during the first trimester of pregnancy. Although ten weeks pregnancy increased lumbar lordosis and thoracic kyphosis (4.2%, 8%, respectively), but it was not significant when compared with no pregnant women. The pelvic inclination angle showed to be more sensitive than spinal curvatures as it showed significant increase within all trimesters and when compared to the control group. Interestingly, it increased nearly 2.5 times more at the end of pregnancy (236%). Conclusion: The present study showed a significant increase in most variables that became higher as the months of pregnancy increased. The results might help clinicians for prescribing suitable exercises or spinal orthoses during pregnancy. More research is recommended in this area in women intending to get pregnant.