Thermodynamic and Thermophysical Properties of Dry Air by Using Cubic Peng-Robinson EoS for Gas Mixtures

Dry air is widely used in industrial and technological applications. Ideal gas EoS is used in dry air thermodynamic property calculations. For most applications, it might be sufficient, but when applications with higher pressure zones are considered, error level will increase. Peng-Robinson cubic Eq. of states is considered for better accuracy of the thermodynamic properties for dry air in this paper. So, the objective of this study is to suggest a more accurate EoS for thermodynamic and heat transfer analyses. Set of computer programs were developed in java language to calculate thermodynamic properties like specific volume, internal energy, enthalpy, entropy, Gibbs energy, Helmholtz energy, specific heat, thermal conductivity, and viscosity of dry air. The results are compared with the perfect gas EoS and the Eq.s developed by The International Association for the Properties of Water and Steam (IAPWS)

Thermal design of spiral heat exchangers and heat pipes through global best algorithm

WOS: 000395170800012This study deals with global best algorithm based thermal design of spiral heat exchangers and heat pipes. Spiral heat exchangers are devices which are highly efficient in extremely dirty and fouling process duties. Spirals inherent in design maintain high heat transfer coefficients while avoiding hazardous effects of fouling and uneven fluid distribution in the channels. Heat pipes have wide usage in industry. Thanks to the two phase cycle which takes part in operation, they can transfer high amount of heat with a negligible temperature gradient. In this work, a new stochastic based optimization method global best algorithm is applied for multi objective optimization of spiral heat exchangers as well as single objective optimization for heat pipes. Global best algorithm is easy-to-implement, free of derivatives and it can be reliably applied to any optimization problem. Case studies taken from the literature approaches are solved by the proposed algorithm and results obtained from the literature approaches are compared with thosed acquired by GBA. Comparisons reveal that GBA attains better results than literature studies in terms of solution accuracy and efficiency

Neural Network Predictive Control of a Vapor Compression Cycle

Turgut, Mert Sinan/0000-0002-5739-2119WOS: 000519133700024This study investigates the Neural Network Predictive Control of a vapor compression cycle (VCC). VCC consists of four components, namely the compressor, electronic expansion valve (EEV), evaporator and condenser. Modeling of the compressor and EEV is carried out with the static relationships, while modeling of the evaporator and condenser is performed with the lumped parameter moving boundary method. the established thermodynamic model is validated against the ASPEN model with the same design specifications. the neural network is trained off-line with the input and output signal data of the established model. the solution of the optimization problem for the each time step is achieved with the metaheuristic method called Whale Optimization Algorithm in the predictive controller. Ultimately, performances of the four different controllers, namely the cooling load, first law efficiency, entropy generation and second law efficiency, are compared with each other. the results show that the entropy generation controller achieves the most favorable exergy destruction performance with 0.2% lower than the worst performer cooling load controller. It is also observed that the second law efficiency controller is the best performer in terms of the overall second law efficiency through the simulation time

Modeling of the drying process of apple slices: Application with a solar dryer and the thermal energy storage system

WOS: 000408288100032In this study a solar air heater was developed to determine the drying rate of apple (Golden Delicious). In order to provide the drying process continuously a packed bed thermal energy storage system was designed and manufactured. Also, a recuperator unit was used for waste heat recovery. In the recuperator unit, it is provided the mixing of the fresh air with the drying air whose moisture content increases, at a specified rate. So at the rate of 50-60% waste heat is recovered and reutilized in the drying system. The advantage of the system is that it consumes less energy at the rate of 76.8% than other drying technologies. Experinients on the drying system were repeated twice a day. In the experiments the drying kinetics of apple slices (5 +/- 2 mm thick) was determined at constant temperatures ranging from 50-60 degrees C. Also, Diffusion Approximation model was used for drying of apple slices in constant temperature. A mathematical model was developed to calculate the prediction of the moisture ratio during time and it is observed that the model is complied with the studies in the literature. (C) 2017 Elsevier Ltd. All rights reserved.Republic of Turkey Ministry of Science, Industry and Technology as a San-Tez ProjectThe study was supported by Republic of Turkey Ministry of Science, Industry and Technology as a San-Tez Project

Numerical investigation of inward solidification inside spherical capsule by using temperature transforming method

In this study, a numerical analysis of the inward solidification of phase change material inside spherical capsule is carried out. The spherical capsule that is subjected to convection from the outside surface initially is not at its melting temperature. The control volume approach and temperature transforming method are applied to solve the dimensionless energy equation. The model solution results are validated through a comparison with published experimental data for similar case and it shows a considerably good agreement. The analysis results show that the larger diameter spherical capsules have significantly greater solidification time compared to those with smaller diameters of spherical capsules. In addition, the entropy generation inside spherical capsule is analyzed. It is found that the entropy generation increases with increasing sphere capsule diameter, attains a maximum and then decreases. Keywords: Entropy generation, Phase change material, Solidification, Spherical capsule

Novel Saturated Flow Boiling Heat Transfer Correlation for R32 Refrigerant

[No Abstract Available