جلال قاسمی

This research has analyzed the drilling process in the human femur bone in order to determine the heat transfer coefficient and investigate the occurrence or non-occurrence of thermal necrosis. 3D drilling simulation have carried out in natural with air and force convection with normal-saline and the analysis performed for three feed rates of 50, 100 and 150mm/min at rotational speeds of 500, 1000 and 2000 rpm. The results show that in the natural cooling state, the highest generated heat is equal to 4J at 50mm/min and 500rpm while the lowest value of generated heat is 1.65J at 150mm/min and 2000rpm. The maximum difference of the average heat transfer coefficient with the experimental results is %12.5, which represents a good accuracy of the present results. The results in this state also show that the average heat transfer coefficient at 100 and 150mm/min is %55 and %29.1 more, respectively, and it is %5 less at 50mm/min rate, compared to the constant value of 20w/m2.k which is considered in the previous researches. Thermal necrosis occurs under all conditions of the natural cooling. In the force cooling, the highest average heat transfer coefficient with normal_saline is 150mm/min at a rotational speed of 2000rpm, which is equal to 3650w/m2.k and in all conditions, the bone temperature has not exceeded the temperature limit of thermal necrosis

In this research, the compact power substation with 800KVA capacity that is produced by Irantransfo Substations Development Company, has been modeled and its thermal class is determined. Modeling of this compact power substation that include a three-phase cast resin dry transformer placed in the enclosure chamber carried out in three-dimension. Then the desired parameters such as fluid flow, pressure drop and temperature distribution in significant parts are investigated. In order to verify the accuracy of the results, four sensors were placed in suitable locates to compare the results of the analysis with the measured values of these sensors. The results of the modeling in comparison with the experimental results show a difference of up to 5.8K. By applying data according to IEC62271-202 standard and appropriate boundary conditions, the maximum temperature difference which occurs in low voltage bobbin is 12K. So the thermal class will be 15K according standard definition. Although it was 14% lower than the laboratory results, the thermal class of this substation also determined in the Laboratory of Electrical Industries of Iran 15K and indicate the good results of this study.

This paper examines the various methods of applying no slip boundary condition on a fixed and rotary cylinder in the lattice Boltzmann framework. For this purpose, five methods of bounce back, LYMLS, QYMLS, LBFL and QBFL are chosen. The main challenge in all of these methods is how to calculate and interpolate the unknown distribution functions at the points around the boundary points. Results show that in the stable conditions (Re=20 and Re=40), the maximum error of calculation of the separation angle is 6.7 % and it is related to the bounce back method, while in the stable conditions, a significant difference cannot be seen between the bounce back and other methods. Also, the LBFL method has the most error in calculating the separation length (6% for Re=20 and 8.82 % for Re=40). By increasing the Reynolds number and increasing the rotational velocity, the bounce back method differs in the prediction of the lift and drag coefficients respect to other methods; so that there is a difference in the lift coefficient in the early times, t*> 7.78 for the conditions of k=0.2 and Re=200, between the bounce back and other methods, however with increasing time, this difference reduces, whereas the three methods of LYMLS, LBFL and QYMLS continue to produce similar results. Investigations show that the choice of the single release time τ has a serious effect on the convergence of the stated methods, so that the two methods of the QYMLS and QBFL have a smaller convergence limit.

In this paper, numerical analysis of flow and heat transfer in a two-dimensional channel with porous medium and based on the lattice Boltzmann method is performed. The main reason for placing the porous medium inside the channel is to reduce the effective cross section of the channel and increase the localized mean velocity to increase the rate of heat transfer and control the maximum temperature of the hot plate. Also, due to passage of a part of the flow from inside of the porous medium, a sudden drop in pressure is prevented by reducing the cross-section. For this purpose, a porous medium with a random structure is considered in the upper part of the channel. The results include the effects of effective parameters such as Reynolds numbers, Prandtl number, aspect ratio and porosity of the porous medium on the maximum temperature, average Nusselt number and pressure drop. Results show that increase of the porosity increases the difference between the maximum temperature of simple channel and channel with porous medium. It is also observed that the use of a porous medium in the low Reynolds numbers creates a higher decrease in the hot plate temperature. In addition, increasing the Prandtl number initially increases the maximum temperature of the hot plate and its further increase will reduce the maximum temperature.

In this paper, the governing equations of sea waves are analyzed nonlinearly and the energy extraction from the waves in the Lark and Faror islands in the Persian Gulf is determined. According to the data in the last 31 years, the waves of these two islands have the most incidence for the height of 0-0.4 m and 0.4-0.8 m corresponding for the time periodicity of 2.4-3 s and 3-3.6 s, respectively. Therefore, waves with an average period of 3 s and a height of 0.5 m are used in the design process. The Cylindrical Energy Transfer Oscillatory (CETO) mechanism is chosen and the conceptual design is carried out with an in-house FORTRAN code, in which the results are in favorable agreement with the available experimental data. Investigations show that optimum power production requires the range of 2.8 to 3.2 for the ratio of the height to the radius of the buoy. Also, it is possible to access 25 kW power for each mechanism in the optimum conditions.

This study was designed to compare morning and evening exercises on a change in levels of salivary immunoglobulin A (IgA), cortisol, and total protein in middle-aged men. For this purpose, 12 middle-aged men (age: 53.42±6.87 years; BMI: 25.21±2.88 kg/m2) participated in this study. They had an endurance training session for 45 minutes with 65% of maximum heart rate in the morning (7 - 8 am) and evening (5 - 6 pm) with a 2-day interval. Salivary immunoglobulin A, cortisol, and total protein levels were measured in the morning and evening (before and after the exercise) by ELISA method. Data were analyzed using analysis of variance with repeated measures and Bonferroni post hoc test. The results showed that morning exercise significantly decreased salivary cortisol concentration levels (P=0.03). No significant changes were observed in other measures. In conclusion, morning exercises reduces salivary cortisol levels in middle-aged men.

Experimental study of convective heat transfer behavior and the AC dielectric breakdown voltage of nano oil for use in transformers is the main scope of this work. The nano oil containing colloidal magnetic Fe3O4 nanoparticles at different volume concentration and the Nytro Libra oil that is the conventional oil in power transformers has been considered as the base fluid. The convective heat transfer behavior was studied by using an experimental setup in laminar flow regime and under constant heat flux. The AC dielectric breakdown voltage by usingBA100 portable dielectric oil tester according to IEC 60156 was carried out. Results show that nano oil with 23 nanometer size and volume concentration of 0.1% has convective heat transfer coefficient to 4.5% higher than the base oil. The AC dielectric breakdown voltage improved 23.8% for nano oil with volume concentration of 0.1% compared to the base oil. The results of the convective heat transfer coefficient behavior of nano oil were compared with othe researchers.

Experimental study of convective heat transfer in nano-fluid, containing Fe3O4powder nano-particles without stabilizer and nano-fluid containing colloidal nanoparticles of Fe3O4, with stabilizer, is the main aim of this work. For this purpose, the Nytro Libra oil, as a conventional oil in power transformers has been considered as the base oil. Results show thatthe use of nanoparticles, improves the base fluid heat transfer characteristics. Alsobased on the experimental observations, the use of nanoparticles in the powder form, decreases and in the colloidal form increases the dielectric properties of transformer oil. Hence, the thermal behavior of the two types of nano-oils would be important. The results in present study showed that the convective heat transfer coefficient of nanofluid, containing nano-particles in the powder form in a tube with constant heat flux, and volume concentration of 0.1% and 0.3%, is 7% and 9.5% mare than nano-oil containing colloidal particles and also 6.5% and 2.4% higher than the base oil, respectively. Finally, thermal behavior of different nano-oils samples are discussed, and other researcher’s arguments are also taken into consideration.

In this paper, a viscous flow simulation is presented using the Lattice Boltzmann Equation (LBE). A finite volume approach is adapted to discretize the LBE on a cell-centered, arbitrary shaped, rectangular tessellation. The formulation includes upwind scheme and high order descretization schemes for the flux term and collision operator respectively. A consistent open and solid boundary treatment according to cell-centered scheme also addressed, which resulted in a wider domain of stability and faster convergence. Validation of the results is conducted by symmetric sudden expansion. The results are compared with reliable analytical or experimental results, indicating the accuracy and robustnes's of the proposed method for analyzing different flows of the interest.

In this paper، the thermo-hydrodynamical analysis of incompressible flow in conjunction with cell-centered finite volume-lattice Boltzmann method (FV-LBM) was developed. To demonstrate the temperature field، the double distributions function (DDF) was used. A novel approach was applied in cell flux calculation by definition of biasing factors based on pressure and temperature. This treatment enlarges the domain stability and leads to faster convergence. A consistent open and solid boundary treatment of flow was also addressed. The unknown energy distribution at the boundary cells were decomposed into its equilibrium and non-equilibrium parts. Then، the non-equilibrium part was approximated with extrapolation of the non-equilibrium part of the populations at the neighboring nodes. Two test cases namely، thermo-hydrodynamic in a backward-facing step and around a circular cylinder inserted within the backward-facing step were carried out. The results were compared with the available solutions in the technical literature showing reasonable agreements.