The brake system of an automobile is composed of disc brake and pad which are co-working components in braking and accelerating. In the braking period, due to friction between the surface of the disc and pad, the thermal heat is generated. It should be avoided to reach elevated temperatures in disc and pad. It is focused on different disc materials that are gray cast iron and carbon ceramics, whereas pad is made up of a composite material. In this study, the CFD model of the brake system is analyzed to get a realistic approach in the amount of transferred heat. The amount of produced heat can be affected by some parameters such as velocity and friction coefficient. The results show that surface temperature for carbon-ceramic disc material can change between 290 and 650 K according to the friction coefficient and velocity in transient mode. Also, if the disc material gray cast iron is selected, it can change between 295 and 500 K. It is claimed that the amount of dissipated heat depends on the different heat transfer coefficient of gray cast iron and carbon ceramics.
The climate crisis caused by global greenhouse gas emissions has led to many disasters around the world in recent years. Some of these disasters are floods in various parts of Europe, melting of Arctic glaciers, and rising water levels in the oceans. People living on islands in Southeast Asian countries are forced to migrate due to rising water levels. With the increase in the frequency of such situations, life on earth is at risk. Greenhouse gas emissions harm not only humans but also animals and plants. The most effective measure that can be taken against this is to stay away from fossil fuels. With the use of fossil fuels, the carbon ratio in the atmosphere increases, and climatic imbalances occur. For this reason, the interest in alternative energy sources is increasing. Wind energy is one of the most widely used renewable energy sources. This is due to the low cost of installation and ease of use. The most important factor affecting the aerodynamic efficiency of wind turbines is the blade profiles. Numerous types of wing profiles have been designed and put into use. In this study, numerical analyzes of NACA 0015 and NACA 4415 airfoils at various angles of attack were performed by determining forces every five degrees between 0 and 20 degrees using ANSYS Fluent commercial software. Lift coefficients and drag coefficients were also calculated for the angles of attack used. According to the analysis results obtained, optimum attack angles were found for each airfoil. As a result, NACA0015 and NACA4415 airfoils were compared in terms of their performance.
Thermoelectric refrigerators are widely used in electronics, medical, and food industry application areas. A refrigeration effect can also be achieved without using any moving parts by merely passing a small current through a closed circuit made up of two dissimilar materials. This effect is called the Peltier effect, and a refrigerator that works on this principle is called a thermoelectric refrigerator. They consist of several thermoelectric legs sandwiched between two thermally conductive plates, one cold and one hot. Thermoelectric refrigerators presently cannot compete with the vapor-compression refrigeration system because of their low-coefficient of performance (COP). However, some applications have been preferred because of their small size, simplicity, quietness, and reliability. In this study, a thermoelectric cooler having a maximum cooling power of 50 W, having a dimension of 40mmx40mmx3.6 mm, is modeled in multi-physics software. Also, the performance of a thermoelectric refrigerator is investigated. It is computed the temperature difference between ceramics plates versus electric current and COP for a temperature difference between ceramics plates. The simulation results are compared with experimental data. The data obtained from the analyses have been compared with the experimental results and found to agree with each other. For the surface temperatures of 25 o C and 50 o C, the maximum coefficients of performance have been computed to be 1.091 and 1.445, respectively. In general, as the temperature of hot surfaces has increased for the same temperature differences, the COP of the thermoelectric cooler has increased.
Carbon-containing waste gases from vehicle exhausts are one of the main causes of climatic disasters. This problem is tried to be solved by reducing the amount of energy consumed by vehicles while they are in motion. To reduce fuel consumption, it is necessary to reduce the effect of aerodynamic drag force, which is the resistance on the solid surface in motion. It is known that high aerodynamic drag force increases fuel consumption. Reducing aerodynamic drag force is important not only for fuel consumption but also for wind noise and roadholding. Heavy vehicles such as trucks have high drag forces due to the width of their surface areas. However, this situation can be minimized with changes to be made in vehicle designs. In this study, the effect of the use of top deflectors on the drag force for trucks has been investigated. In this theoretical study, separate calculations have been made for different vehicle velocities and the results have been compared among themselves. In this study, which has been carried out using the computational fluid dynamics method, k-e has been preferred as the turbulence method. As a result, it has been concluded that the use of top deflectors reduces drag force, which in turn reduces fuel consumption.
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