Yazar "Atas, Safak" seçeneğine göre listele

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    Designing of energy saving system with heat recovery and solar air collector
    (Elsevier, 2023) Atas, Safak; Ceylan, Ilhan; Timar, Osman Egemen
    In this study, it is aimed to increase the efficiency of heat pump systems, which are generally used for heating in winter. A combined system was created by utilizing the heat pump system, solar air collectors and a heat recovery device. The coefficient of performance of the heat pump system was 6.4 and the efficiency of the solar air collector was 70% while 85% energy efficiency was acquired from the heat recovery device used in the system. The heat recovery device's energy efficiency was calculated as 85%, while the exergy efficiency was calculated as 40%. The usage of these three systems, which has already high energy-efficiency at separately usage, together in one single system has prevented the decreasing that may occur in the energy efficiency of the systems during the day increased their efficiency. The outdoor air temperature in the winter season significantly reduces the efficiency of heat pump systems, and even many systems work defrost mode. The proposed and experimentally studied system, the operability of the heat pump has been ensured throughout the day. For this process, the system has been able to benefit not only from the solar air collector, but also from the energy of heat recovery device.
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    Development and Analysis of a Multi-evaporator Cooling System with Electronic Expansion Valves
    (Springer Heidelberg, 2017) Atas, Safak; Aktas, Mustafa; Ceylan, Ilhan; Dogan, Hikmet
    In this study, a vapor compression cooling system with three evaporators and electronic expansion valves was designed, manufactured and tested experimentally. Compressor of this system was converted to be inverter driven which enabled it to run at variable speeds. Temperature values of cold rooms were controlled more sensitive by using electronic expansion valves. Energy analysis was done by comparing the operating parameters of the system with constant and variable speeds. Programmable logic control (PLC) and cold room controls were used to control the system. The PLC device provided the variable operation of the system by determining the required operation frequency of the compressor according to the changes at the suction line. Using this program, the desired values are set on the PLC screen and the multi-evaporator cooling system was tested at various conditions. The desired conditions are determined for the system at 0,+5 and -5 degrees C temperatures. Calculations on the experimental results revealed that the cooling coefficient of performance is 1.86 for the constant frequency operation and 2.22 for the variable frequency operation. Besides, it was determined experimentally that the system running on variable frequency consumed 20% less electrical energy than the constant frequency system.
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    EXPERIMENTAL COMPARISON OF ECO-FRIENDLY REFRIGERANT COUPLES R407C/R32/R600a (90/10 BY WT.%) AND R407C/R32 TO REVEAL THE GWP AND THERMODYNAMIC PROPERTIES
    (Begell House Inc, 2023) Al Kraim, Adel Mohmed; Atas, Safak
    In this experimental study, based on cooling couples a new mixture (90%R32 + 10%R600a) has been proven to be better than R32 for the global warming potential (GWP) in a low-pressure cycle (LPC), within a high-pressure cycle (HPC) R407C by utilizing a small laboratory cooling system. This system consists of two cooling cycles connected by a heat exchanger and has also been termed as a mini cascade refrigeration system (MCRS). The main aim of this study is to study a suitable gas or mixture for MCRS at the lowest GWP value and a low-temperature cooling room to reach less than -30?. In the same way, the following conditions have been determined in this research: the inlet and outlet temperatures of the evaporator, condenser, heat exchanger, compressors, with evaporator pressure as well as superheat. Consequently, MCRS can be used with thermostats at the lowest degree of -32? or less, the mixture has results close to R32 and the coefficient of performance for MCRS COPMCRS is equal to 1.63 and 1.78 for the new mixture and R32, respectively, under the same operating conditions. Therefore, the ozone depletion potentials (ODP) for R32 and the new mixture are equal to zero, and the GWP for the new mixture is less by amount of 63 than that for R32. The MCRS can be used in a small place, for instance, transport blood samples, blood tests, and vaccines by small cars. Both R32 and R600a are flammable gases, so this study will be carried on in the future for safer replacements.
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    Using the artificial neural network model for modeling the performance of the counter flow vortex tube
    (Pergamon-Elsevier Science Ltd, 2009) Uluer, Onuralp; Kirmaci, Volkan; Atas, Safak
    In this study, the effect of the nozzle number and the inlet pressure on the heating and cooling performance of the counter flow type vortex tube has been modeled with artificial neural networks (ANN) by using the experimentally obtained data. ANN has been designed by Pithiya software. In the developed system output parameter temperature gradient between the cold and hot outlets (Delta T) has been determined using inlet parameters such as the inlet pressure (P(inlet)), nozzle number (N), and cold mass fraction (mu(c)). The back-propagation learning algorithm with variant which is Levenberg-Marquardt (LM) and Fermi transfer function have been used in the network. in addition, the statistical validity of the developed model has been determined by using the coefficient of determination (R(2)), the root means square error (RMSE) and the mean absolute percentage error (MAPE). R(2), RMSE and MAPE have been determined for Delta T as 0.9947, 0.188224, and 0.0460, respectively. (C) 2009 Elsevier Ltd. All rights reserved.