نشریه مهندسی مکانیک ایران
سال بیست و دوم شماره 2 (پیاپی 59، تابستان 1399)

The use of Turbocharger for increasing incoming air density to the motor and thus increasing its power is a common method. Due to the variation of the engines in volume, the number of cylinders and the power, the turbocharger for a particular engine may not completely match the motor. This paper tries to improve the turbine performance by changing the angle of the turbine blade toward the selective compressor turbocharger and the 3-D flow simulation. The results show that the variation of the angle of the turbine at a value of about 4.7 degrees improves the turbine performance by about 18 %. This improvement of performance, especially the power of the turbine at the low speed of the motor, is very valuable when the energy from the engine is low. In order to validate, the engine and turbocharger set are tested on the test platform, and in different cycles of the motor, the performance parameters of the turbocharger turbine are measured and compared with the simulation results.

In the treatment of magnetic hyperthermia (MFH), tumor cells are degraded under the heat generated by magnetic nanoparticles (MNPs) under an intermittent magnetic field. The function of MFH treatment depends on factors such as concentrations and the distribution of MNPs within the tumor's interstitial space. A prominent method for the accumulation of MNPs within the tumor area is arterial infusion. In this study, a complex numerical model based on the solution of advanced mathematical equations, by injection of MNPs into the arteries, the transfer of a soluble substance from the wall to the arteries through the presence of a concentration gradient due to the difference in plasma concentration and interfacial concentration leads to the diffusion mechanism , And fluid movement due to the pressure gradient leads to the displacement of MNPs. For this purpose, in three constant concentrations of plasma, 130 mol/m^3 , 150mol/m^3 , 170mol/m^3 0, based on two continuous injections and mass injections, their effects on the concentration of the antifungal fluid and The temperature field is treated during hyperthermia magnetic therapy.

The present study investigates the effect of office building orientation on energy consumption, solar heat gain and carbon production in three climates. Using Designer Builder software, simulations are performed on a sample building in Bushehr, Bandar-Abbas, Shiraz, Yazd and Tabriz in different orientations. Based on the results, building faced exactly to the south has the most favorable conditions. Buildings with 0 and 180 orientation have minimum energy consumption while maximum energy consumption is in other orientations. The most unfavorable orientations in Bushehr, Bandar Abbas, Shiraz, Yazd and Tabriz are 80, 70, 85 and 68 degrees, respectively. Best orientation in terms of energy consumption and reduced carbon is the same, and only in Tabriz maximum carbon is produced at 83 degrees orientation. The difference in energy consumption is 2.9 to 5.4 percent and 1.9 to 5.6 percent for corresponding carbon production. The results are in contrast to the general recommendation for building design to face south-east orientation.

In this work, 50% deionized water and 50% ethylene glycol hybrid nanofluids containing carbon nanotubes (CNTs) with different lengths and 0.1 Vol% concentration were prepared and their thermal conductivity were measured at 30, 50, 70 and 90 °C. In order to change the CNTs lengths and enhance their dispersibility in different fluids, the CNTs were functionalized. The results showed that the thermal conductivity of nanofluids containing functionalized CNTs was higher than that of for nanofluids containing pristine CNTs. The results showed that such nanofluids exhibited a combination behavior of the pure deionized water based nanofluids and ethylene glycol based nanofluids. It was found that the thermal conductivity was increased with increasing temperature as pure deionized water based nanofluids, and the thermal conductivity was increased with increasing time for all kind of nanofluids as the ethylene glycol based nanofluids so that after 65 days, about 21% thermal conductivity enhancement was measured.

In the present study, three types of solar air heaters for geographical location and climatic conditions of Kermanshah were analyzed numerically using fluent software. The analysis was carried out for the radiation intensity measured at different hours of July 15th and January 15th at two mass flowrates of 0.011 and 0.037 kg / s. The results show that the use of porous media below the adsorbent surface in double-pass solar air heaters increases the temperature difference and also increases thermal efficiency. The maximum temperature difference in double-pass solar air heater with porous medium was calculated at 13 o'clock at a mass flow rate of 0.011 kg / s and its value was 40.8 ° C. At the same solar air heater, the maximum thermal efficiency was calculated on July 15th at 1:00 pm at a mass flow rate of 0.037 kg / s and its value was 70%. In general, it can be concluded that the temperature difference and thermal efficiency in the single-pass solar air heaters with thermal recovery are less than double-pass heaters with porous medium and simple double-pass heaters.

Electrowinning is the process of copper deposing from the intracellular electrolyte solution to the cathode. In the present study, using electrodynamic cell simulation of the Miduk Copper Complex, mass transfer coefficient on the entire cathode surface are investigated. The hydrodynamic simulation of these cells in the Miduk Copper Complex is studied using computational fluid dynamics. Ansys-CFX is used for this modeling. The Navier-Stokes equations and the continuum are considered as two-phase liquid and gas, turbulent, incompressible, and steady state, and the equation for the concentration of copper in the electrolyte will be solved by considering its specific boundary condition. The perturbation of the flow will be modeled using k-ω relations. The cathode mass transfer coefficient of the industrial copper cell was evaluated by measuring the copper mass of the cathode sheets produced in each cell and the operating conditions of the cell under real conditions. The results show 1.9% difference between the actual amount in copper and the modeling value

Today, electricity generation from photovoltaic panels is on the rise due to the reduction of fossil fuel resources and the problem of global warming. Because these modules are exposed to the outdoors, they are greatly affected by weather conditions. This study was conducted to investigate the effect of radiation intensity on the performance of photovoltaic panels in Tehran with different climates. The results show that the amount of radiation is linearly dependent on the panel output power and the panel surface temperature. The radiation in summer is 70% more than winter and the panel output power is 50% more in winter. The results show that solar air temperature can be used as a heating source from 8 am to 4 pm in winter and 7 pm in summer and can be used as a cooling source after such times. The measurement uncertainty and equipment measurement uncertainty were also found to be in the range (7.91% - 7.69%).

The purpose of this study was to investigate the effect of distance between glass cover and absorber plate, the height of the V grove in the absorber plate, The mass flow rate of the air inlet to the collector, on the energy and exergy efficiencies of a solar air collector with V grove absorber plate, by mathematical modeling. The heater is of dual pass type and its length, width and height are 2, 1 and 0.2 meters, respectively. The distance between the glass and the absorber plate is 12.5, 25, 50, 75, 100 millimeter, , respectively. The results show that by increasing the distance between the glass and the absorber, the thermal efficiency increases by 9 percent and the exergy efficiency by 30 percent. Also increasing the height of the V grove more than 10 cm will not cause significant changes in the efficiency of the first and second laws.

In this experimental research the heat transfer coefficient changes in pool boiling using bubble dynamic in three aqueous, electrolyte and nanofluid solutions have been investigated. An insulated glass tank with a cooper cylindrical element (constant roughness) was considered. The effects of the bubble dynamic parameters such as bubble departure diameter, bubble departure frequency and the density of the bubble generation points are significant and effective on the heat transfer coefficient through increasing agitagation and turbulency in the solution. Therefore increasing these parameters had a direct relation to enhance the heat transfer coefficient due to agitation conditions. Although the deposition of the nanoparticles and salt led to decrease the heat transfer coefficient, it aided to make capillary force on heat transfer surface and increase the critical heat flux point. Therefore, it could act as a positive parameter in optimum conditions. Finally, the deposition resulted in a delay in converting the nucleate boiling to film boiling. The results showed that CuO nanofluid increased the heat transfer coefficient from 6.2 (deionized water) to 8.8 kW.m -2.°C -1. This amount is about % 38.44 and % 39.76 higher than deionized water and electrolyte solution, respectively.

The present paper aimed to conduct an experimental study on the hydro-thermodynamic performance of the double-tube heat exchanger using the water-magnesium oxide nanofluid and double twisted tape with three different steps (3.5,5and7 cm).The experiments were performed in the turbulent flow for the Reynolds numbers from 4400 to 16000 and the nanofluid volume fractions of 0.7%and 1.0%.The results were obtained at different flow rates with or without the use of twisted tape and nanofluid designed and manufactured in the experimental setup to calculate the convection heat transfer coefficient.Also the effect of using double twisted tapes at three steps along with the magnesium oxide nanofluid was greater in the higher Reynolds numbers.In the Reynolds numbers 4400,the convection heat transfer coefficient increased about17%for the volume fraction of0.7%and about 29% for the volume fraction of 1%.Also in the Reynolds number of 16000,it increased about48%for the volume fraction of 0.7% and about53% for the volume fraction of 1%.The simultaneous use of magnesium oxide nanofluid and double twisted tapes with the step of 3.5 cm in the Reynolds number 6400 was more effective than deionized water compared to other results.The performance evaluation criteria were examined in all cases and in case of using nanofluid and twisted tape with the step size of 3.5 cm, the highest value of the performance evaluation criterion is obtained with80% increase compared to the base state.