Mechanical Engineering / Makina Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4129
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Article Citation - WoS: 12Citation - Scopus: 11Inverted Fins for Cooling of a Non-Uniformly Heated Domain(Yıldız Teknik Üniversitesi, 2015) Çetkin, Erdal; Çetkin, Erdal; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThis paper shows that the peak temperature of a non-uniformly heated region can be decreased by embedding high-conductivity tree-shaped inserts which is in contact with a heat sink from its stem. The volume fraction of the high-conductivity material is fixed, and so is the volume of the solid region. The length scale of the solid domain is L. Inside there is a cube-shaped region with length scale of 0.1L and heat production 100 times greater than the rest of the domain. The location of this hot spot was varied to uncover how its location affects the peak temperature and the design of inverted fins, i.e. highconductivity tree-shaped inserts. The volume fraction of the high-conductivity tree was varied for number of bifurcation levels of 0, 1 and 2. This showed that increasing the number of the bifurcation levels decreases the peak temperature when the volume fraction decreases. The optimal diameter ratios and optimal bifurcation angles at the each junction level are also documented. Y-shaped trees promise smaller peak temperatures than T-shaped trees. The location of the vascular tree in the z direction also affects the peak temperature when the heat generation is non-uniform. In addition, the peak temperature is minimum when z = 0.65L even though the hot spot is located on z = 0.75L.Article Citation - WoS: 3Citation - Scopus: 4The Effect of Cooling on Mechanical and Thermal Stresses in Vascular Structures(Yıldız Teknik Üniversitesi, 2018) Çetkin, Erdal; Çetkin, Erdal; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyHere, we show how the vascular channel configuration and its shape affect the mechanical strength which is simultaneously subjected to heating and mechanical load. The material properties were defined as functions of temperature. The effect of channel cross-section on the coolant mass flow rate, peak temperature and peak stresses are documented. The results show that the resistances to flow of stresses and fluid is minimum with the circular channels while the resistance to the heat flow is the smallest with semi-circular channels. In addition, morphing the vascular design provides almost the smallest resistance to the heat flow with circular channels (0.3% difference in the peak temperature). This shows that even the convective resistances are the smallest with circular-cross section, overall thermal resistance is smaller in semi-circular design for the fixed fluid volume. The peak stress is smaller with hybrid design than the parallel designs for the entire pressure drop range. In addition, the effects of mechanical load, heating rate and reference temperature on the stress distribution are also documented. Furthermore, the thermal and mechanical stresses are also documented separately, and then compared with the coupled solution cases. The chief result of this paper is that for a coupled system minimizing only one of the resistance terms is not sufficient, all the resistances considered simultaneously in order to uncover the best performing design. In coupled solutions, we documented the simulation results with temperature dependent material properties and the resistances to the heat and fluid flow is affected by the mechanical deformations. In addition, the results show that the designs should be free to vary, the unexpected designs can be the best performing designs for the given parameters and constraints. Therefore, the design parameters based on the experience does not always yield the best performing designs as the objectives and constraints vary.Article Citation - WoS: 2Citation - Scopus: 2Vascular Structures for Smart Features: Self-Cooling and Self-Healing(Yıldız Teknik Üniversitesi, 2017) Çetkin, Erdal; Çetkin, Erdal; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyHere we show how smart features of self-cooling and self-healing can be gained to mechanical systems with embedded vascular structures. Vascular structures mimic the circulatory system of animals. Similar to blood distribution from heart to the animal body, vascular channels provide the distribution of coolant and/or healing agent from a point to the entire body of a mechanic system. Thus the mechanic system becomes capable of cooling itself under unpredictable heat attacks and capable of healing itself as cracks occur due to applied mechanical loads. These smart features are necessary for advanced devices, equipment and vehicles. The essential design parameter is vascularization in order to provide smart features. There are distinct configurations for vascularization such as radial, tree-shaped, grid and hybrids of these designs. In addition, several theories are available for the shape optimization of vascular structures such as fractal theory and constructal theory. Unlike fractal theory, constructal theory does not include constraints based on generic algorithms and dictated assumptions. Therefore, constructal theory approach is discussed in this paper. This paper shows how smart features can be gained to a mechanical system while its weight decreases and its mechanical strength increases simultaneously.Article Citation - WoS: 7Citation - Scopus: 7The Importance of Internal Heat Gains for Building Cooling Design(Yıldız Teknik Üniversitesi, 2017) Durmuş Arsan, Zeynep; Turhan, Cihan; Durmuş Arsan, Zeynep; Coşkun, Turgay; Turhan, Cihan; Gökçen Akkurt, Gülden; 02.02. Department of Architecture; 03.10. Department of Mechanical Engineering; 03.06. Department of Energy Systems Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology; 02. Faculty of ArchitectureThis paper aims to investigate the effect of internal heat gains on the cooling load of a building. The house occupied by three adult men is selected as the case study for paper. The house is in the third floor of the apartment. The apartment has four flats and it has no insulation around the external walls. The heat dissipation from lighting devices, electrical equipment and the occupants are calculated by using the DesignBuilder v4 Beta release simulation program. The temperature of the house is observed during three weeks by using hobo data loggers and calibration of the measurements is made with respect to weather data file of the flat. Detailed schedule based on time of operation and occupancy is prepared to get more accurate results. Annual energy consumption and cooling load of the house is determined by using the dynamic simulation program.