Arzu Şencan Şahin

Optimization of solar air collector using genetic algorithm and artificial bee colony algorithm

Thermal performance of solar air collector depends on many parameters as inlet air temperature, air velocity, collector slope and properties related to collector. In this study, the effect of the different parameters which affect the performance of the solar air collector are investigated. In order to maximize the thermal performance of a solar air collector genetic algorithm (GA) and artificial bee colony algorithm (ABC) have been used. The results obtained indicate that GA and ABC algorithms can be applied successfully for the optimization of the thermal performance of solar air collector.

COMPARATIVE ANALYSIS OF NEURAL NETWORK AND NEURO-FUZZY SYSTEM FOR THERMODYNAMIC PROPERTIES OF REFRIGERANTS

Fast and simple determination of the thermodynamic properties of refrigerants is very important for analysis of vapor compression refrigeration systems. Although tables are available for refrigerants, limited data of tables are not useful in the simulation of refrigeration systems. The aim of this study is to determine the thermodynamic properties such as enthalpy, entropy, specific volume of the R413A, R417A, R422D, and R423A by means of the artificial neural networks (ANN) and adaptive neuro-fuzzy (ANFIS) system. The results of the ANN are compared with the ANFIS, in which the same data sets are used. The ANFIS model is slightly better than ANN. Therefore, instead of limited data as found in the literature, thermodynamic properties for every temperature and pressure value with the ANFIS are easily estimated.

Energy and exergy analyses of vacuum drying process of pine timbers

In this study, an experimental system for the vacuum drying of timbers is designed. Experiments in the different temperature, pressure and the residence time in vacuum are carried out. The drying experiments are conducted at three different drying temperatures varied between 40°C and 60°C. The drying experiments are conducted at three different pressures varied between 60 kPa and 80 kPa. The residence time in vacuum is varied between 5 min and 15 min. In addition, Programmable Logic Controller (PLC) system to drying system is added. Energy and exergy analyses of vacuum drying process of pine timbers are carried out.

Prediction of Thermodynamic and Thermophysical Properties of Carbon Dioxide

CO2 may be an important alternative refrigerant to hydrofluorocarbons in commercial refrigeration systems. CO2 is one of the few natural refrigerants that is neither flammable nor toxic. It is inexpensive, widely available, and does not affect the global environment as do many other refrigerants. In this study, alternative methods are presented using artificial neural networks and adaptive neurofuzzy inference systems to determine thermodynamic and thermophysical properties of CO2. The results of the artificial neural network model are compared with those of the adaptive neurofuzzy inference system model in which the same datasets are used. The artificial neural network model is much better than the adaptive neurofuzzy inference system model. A new formulation is presented for the determination of the thermodynamic and thermophysical properties of CO2. The results of this study show that the artificial neural network model is an excellent alternative method for the calculation of thermodynamic and thermop...

Determination of drying rates of different timber kinds

ABSTRACT In this study, the drying rate of poplar, pine, and oak timbers is estimated using an adaptive neuro-fuzzy inference system (ANFIS). Experimental data were used for training and testing networks. The R2 value obtained when unknown data were applied to the networks was 0.99982 for the drying rate of poplar timbers, 0.999028 for the drying rate of pine timbers, and 0.999968 for the drying rate of oak timbers, which is very satisfactory. The method proposed offers more flexibility and therefore drying analysis of different timber kinds is fairly simplified.

A gene expression programming approach for thermodynamic properties of working fluids used on Organic Rankine Cycle

The selection of appropriate fluid in Organic Rankine Cycles (ORC) is an important issue. The thermodynamic properties of working fluids affect the efficiency, operation and environmental impact of the system. Many working fluids for ORC power plants are available. Pentane (R-601) and R245fa are the most used for ORC. In this work, a gene expression programming (GEP) model for estimating thermodynamic properties of pentane (R-601) and R245fa was used. New formulations are presented for determination of the enthalpy and entropy values of two working fluids. The actual results were compared to the results obtained with GEP. The obtained results showed that the formulations are effectively capable of evaluating the thermodynamic properties of working fluids. The GEP-based formulations are simple. These formulations will be helpful for thermodynamic analysis of ORC systems.

Mathematical modelling of drying characteristics of medical plants in a vacuum heat pump dryer

ABSTRACT In this study, drying behaviour of medical plants such as fresh sweet basil, parsley and dill leaves in a vacuum heat pump dryer was investigated. Drying experiments were conducted at the vacuum pressure of 0.6 bar and the drying temperatures of 36°C and 46°C. Five thin layer drying models namely the Henderson and Pabis model, Logarithmic model, Two-term model, Modified page equation model and Lewis model to estimate moisture ratio of medical plants were used. Different mathematical drying models were compared according to their root mean square error, the coefficient of determination (R2) and reduced chi-square (χ2). For sweet basil, parsley and dill leaves, the logarithmic model, the Two-term model and the Henderson and Pabis model showed better fit to the experimental data compared to other models, respectively.

Soft Computing in Absorption Cooling Systems

Absorption cooling systems make sense in many applications for process water cooling. Instead of mechanically compressing a refrigerant gas, as in the conventional vapor compression process, absorption cooling uses a thermo-chemical process. Two different fluids are used, a refrigerant and an absorbent. Heat directly from natural gas combustion, solar energy, waste-heat source or indirectly from a boiler, drives the process.