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Öğe Artificial neural network approach for evaluation of temperature and density profiles of salt gradient solar pond(Elsevier Sci Ltd, 2007) Kurt, H.; Atik, K.; Ozkaymak, M.; Binark, A. K.The purpose of this study is to evaluate temperature and density profiles of an experimentally investigated salt gradient solar pond (SGSP) by using artificial neural network ( ANN). The input parameters of the ANN are solar pond depth, ambient temperature, radiation absorption coefficient of salty solution in the pond, initial density values of the pond and time of day. The output parameters of the ANN are temperature and density profiles in the pond. The experimental data set consists of 168 values. These divided into two groups, of which the 134 values were used for training/learning of the network and the rest of data ( 34 values) for testing/validation of the network performance. According to the ANN predicted results compared to the experimental results, the mean relative error (MRE) is 2.30% for temperature and 0.63% for density. The correlation coefficients (R-2) between the experimentally measured and the ANN predicted results are 0.9632 for temperature and 0.9855 for density in the test/validation data set. The calculated errors of proposed ANN model are in acceptable ranges. These results indicated that the ANN approach could be considered as an alternative and practical technique to evaluate the temperature and density profiles of a SGSP.Öğe An Experimental Investigation of a Domestic Type Solar TE Cooler(Taylor & Francis Inc, 2012) Atik, K.; Yildiz, Y.In this study, a domestic refrigerator is operated by a thermoelectric cooler Thermoelectric modules are fed by the photovoltaic, which are connected directly to thermoelectric modules. Thermoelectric modules were chosen so as to compensate the heat gained by the refrigerator; and solar cells were chosen so as to supply the power demand of the solar cells. Incident solar radiation, outside and inside temperatures, surface temperatures of thermoelectric module, and the voltage produced were measured. Calculations were made using these measurements. According to the results, the temperature difference between the inside and outside of the refrigerator was 14.7 degrees C and cooling coefficient of performance of the system was calculated as 0.58.Öğe An experimental investigation of the effect of refrigerant charge level on an automotive air conditioning system(2011) Atik, K.; Aktas, A.During the last 25 years automotive air conditioning (AAC) systems have significant development introduced by the industry and research institutes in the world to minimize the global warming threat to the environment. This paper reports the results of a study on the performance of an AAC system with measuring the compressor driving speed and the refrigerant leakage. For this purpose an experimental set up is designed and constructed to investigate the system performance. Although, the manufacturer's recommended amount for the tests with R-134a as refrigerant was 750 g, the experiments were also carried out by selecting different amount of the same refrigerant charges to analyse the coefficient of performance (COP), the cooling capacity and the compressor power change with respect to the rotating speed of the compressor. The evaluation of experimental data revealed that the best cooling capacity was achieved at 500 g refrigerant charge. Although, while the charge level decreased 40% below or increased 20% above the 500g of the charge amount, cooling capacity loss increased up to 25% when optimum value of 500 g of the cooling refrigerant was utilized. The test results proved in each case that increasing the compressor driving speed cause almost a linear change in the corresponding power level. The test results also shown that COP of the cooling system was decreased effectively when the revolution speed increased for any specified charge amount of the refrigerant. ©2008 TIBTD Printed in Turkey.Öğe Investigation of instable movements of liquid-solid two phase mixture by using numerical and Slezkin-Targ method(2006) Atik, K.; Racabovadiloglu, Z.In this study, instable movements of a liquid-solid two phase mixture flow through the pipe have been investigated. A differential equation system representing movement has been solved in two different ways. One of them is analytical solution of an equation system obtained by the application of Slezkin-Targ Method which is used in the problems with one fluid movement. The other is the solution of differential equation by the help of finite difference equations which is one of the numeric solution methods. Both of solutions have been obtained considering beginning and boundary conditions. The results obtained from the solutions have been investigated by velocity-time graphs for different semi-diameters. The results lead to the decision that is Slezkin-Targ Method can be applied for two phase flow problems providing which velocity profiles in both solutions are very close one another and accessing the same velocity values in steady state position.
