https://hdl.handle.net/20.500.12294/484 Makina Mühendisliği Bölümüne ait bildiri ve sunumlar bu koleksiyonda listelenir. Tue, 10 Nov 2026 23:22:30 GMT 2026-11-10T23:22:30Z https://hdl.handle.net/20.500.12294/1973 The performance evaluation of CO2 transcritical booster and R290/R744 cascade refrigeration systems for different cities in Turkey Özyurt, A.; Sinar, U.; Yılmaz, Deniz; Yılmaz, B. CO2 as a natural and fully environmentally friendly refrigerant has become more preferable in refrigeration systems in recent years. Since its critical temperature is much lower than that of other refrigerants. It is mostly used in cascade refrigerant systems as a low temperature cycle fluid. On the other hand, CO2 may be used in single-stage transcritical refrigeration systems. In this study, performance of two natural refrigerant solutions, trans-critical booster CO2 refrigeration system with ejector and a R290/CO2 cascade refrigeration system are examined theoretically by using EES software. Operating conditions are determined to represent different climatic regions in Turkey using summer dry bulb temperatures of various cities. The trans-critical and the cascade system are assumed to operate at two different evaporation temperatures of -10°C and -25°C,respectively. The overall EER values for each system with respect to the same ambient and evaporation conditions are compared and evaluated. Finally, performance of both systems has been compared and the appropriate solution for each city has been suggested. © 2017 International Institute of Refrigeration. All rights reserved. Yılmaz, Deniz(Arel Author); 7th Conference on Ammonia and CO2 Refrigeration Technology -- 11 May 2017 through 13 May 2017 -- Sun, 01 Jan 2017 00:00:00 GMT https://hdl.handle.net/20.500.12294/1973 2017-01-01T00:00:00Z https://hdl.handle.net/20.500.12294/1918 Numerical investigation for convective heat transfer and friction factor under pulsating flow conditions Aslan, Erman; Özsaban, Mert; Özçelik, Güven; Güven, Hasan Rıza For pulsating flow, the behaviours of the convective heat transfer and friction factor for a periodic corrugated channel are investigated numerically. The finite volume method is used in the numerical study. Three different Reynolds Averaged Numerical Simulation based turbulence models, namely the k-? model, the Shear Stress Transport (SST) model and the transition SST model are used and compared. The results are also compared with the previous experiments for non-pulsating flow. Analyses are conducted for air flow through a corrugated channel which has sharp corrugation peaks with an inclination angle of 30° and a 5mm minimum channel height. Reynolds number is changed in the range 6294 to 7380, while keeping the Prandtl number constant at 0.70. A sinusoidal pulsatile flow condition which is F=400 and uA?=0.5 is used. Variations of the Nusselt number and the friction factor with the Reynolds number are studied. Non-pulsating flow results and pulsating flow results are compared with each other. © The Authors, published by EDP Sciences, 2018. 11th International Conference on Computational Heat, Mass and Momentum Transfer, ICCHMT 2018 -- 21 May 2018 through 24 May 2018 -- Mon, 01 Jan 2018 00:00:00 GMT https://hdl.handle.net/20.500.12294/1918 2018-01-01T00:00:00Z https://hdl.handle.net/20.500.12294/1910 Improving performance of transcritical CO2 systems, using phase change materials (PCM) in a cold storage application Özyurt, Ali; Yılmaz, Barış; Mançuhan, Ebru; Yılmaz, Deniz; Kurtboğan, Dilara Thermal energy storage is one of the most promising solutions for energy savings and increasing efficiency. To improve the performance of cold storage applications, incorporating phase change materials (PCM) to these systems, is a new approach. In this study, the performance of a transcritical CO2 refrigeration with a PCM incorporated supermarket refrigerator was investigated experimentally. The supermarket refrigerator was operated at evaporation temperature of-10 oC and cooling capacity of 4.2 kW. The PCM was chosen to have a melting and freezing point temperature of-4 oC. Differential Scanning Calorimeter (DSC) device was used to determine properties of salt solutions such as melting/freezing temperatures and latent heat of fusion and freezing. In order to determine the system performance, compressor on-off time and its duration were measured for the cases with and without PCMs. It is revealed that by addition of PCMs, the compressors runtime was decreased meaningfully. © 2019 IIF/IIR. Bitzer;et al.;GEA Refrigeration;JCI-Sabroe;LU-VE Group;Thermofin GmbH; 8th Conference on Ammonia and CO2 Refrigeration Technologies, Ohrid 2019 -- 11 April 2019 through 13 April 2019 --; #nofulltext# -- Yılmaz, Deniz (Arel Author) Tue, 01 Jan 2019 00:00:00 GMT https://hdl.handle.net/20.500.12294/1910 2019-01-01T00:00:00Z https://hdl.handle.net/20.500.12294/485 The place of pedagogical training in engineering education İnce, İbrahim Timuçin Academic personnel attendant in engineering education predominantly performs educational functions besides research functions, development and laboratory works. At this stage, the communication and interaction between instructor and student make very large influence in the quality of the education. This paper describes the role of pedagogical knowledge and training of instructors and academic personnel in the educational activity and in the relation and communication with students. A list of fundamental objectives is presented along with suggestions. Conference: International Teacher Education Conference. Dubai, UAE, February 5-7, 2014. Wed, 01 Jan 2014 00:00:00 GMT https://hdl.handle.net/20.500.12294/485 2014-01-01T00:00:00Z