Ugur Akbulut

Technical and Economic Performance Analysis of Utilization of Solar Energy in Indoor Swimming Pools, An Application

In this study, technical and economic performance analyses are conducted in order to determine the optimum collector surface area for indoor swimming pools. Required heat and economical conditions are taken into consideration while performing these evaluations. A brief summary of solar energy source and heat transfer equations for the Olympic pools are given. An Olympic swimming pool is assumed to be in different cities, and energy losses are calculated. For our sample Olympic pool, convective heat loss obtained is −3.86 kW and evaporative heat loss obtained is 265 kW. Total heat loss always maximum in January from 384 kW to 455.1 kW. Solar energy gain (assumption 1000 m2 collector area) and energy gain from boiler for different cities are calculated as maximum solar energy gain in July between 160 and 175 kW and minimum in January between 54.9 and 82 kW. High investment costs for solar power systems are responsible for low value of the reduction rate. Also, according to the energy demand and economical conditions, technical evaluations are performed in order to obtain optimum surface collector area, and economical analyses are conducted using unified cost method.

A parametric study on exergetic performance of a YSZ electrolyte supported SOFC stack

This paper presents a parametric study on the exergetic performance assessment of an electrolyte supported solid oxide fuel cell (SOFC) stack. Considering the operating and design parameters of yttria stabilised zirconia (YSZ) electrolyte supported SOFC stack, the variations of overpotentials, the rational overpotentials and the exergetic efficiencies are investigated for comparison purposes. Consequently, considering the selected operating conditions and design parameters, it is suggested that the YSZ electrolyte supported SOFC stack having higher exergetic efficiency than 30% is used. Moreover, in order to operate such a fuel cell in an exergetically more efficient manner, the minimum YSZ electrolyte thickness needs to be thicker than 150 μm. Otherwise, some durability and manufacture problems may occur. However, a decrease of operating temperatures from 1273 K to 1073 K and an increase of YSZ electrolyte thickness from 150 μm to 500 μm will result in a reduced exergetic efficiency.

Entropy Generation of Hydrogen Flow in a Curved Annular Duct

The main objective of this study is to numerically investigate the entropy generation of both hydrodynamically and thermally fully developed laminar flow of hydrogen gas under various operating pressures and temperatures in the concentric curved annular ducts with rectangular cross section. In this regard, the solutions of discretized continuity, momentum and energy equations have been obtained using elliptic Fortran Program based on the SIMPLE algorithm. The solutions have been achieved for (1) Dean numbers ranging from 2.3 to 202.9, (2) Annulus dimension ratios of 5.5, (3) Operating pressures of 0.101325, 1, 10, 40, 70 and 100 MPa, (4) Core wall temperature of 50 and 80 °C, (5) Duct wall temperature of 25 °C. In this regard, overall entropy generation in the whole flow field has been analyzed in detail. Moreover, the effects of Dean number, operating pressure and core wall temperature on entropy generation arising from the flow and heat transfer have been investigated. Accordingly, it is concluded that the effect of volumetric entropy generation that is a result of fluid flow can be neglected as compared with volumetric entropy generation due to heat transfer. When Dean number, operating pressure and core wall temperature increase the total volumetric entropy generation goes up. Thus, it is expected that this study will contribute to develop the energy efficient-hydrogen gas heaters for practical applications including hydrogen exchangers, PEMFC applications, hydrogen gas turbines, chemical mixing processes and hydrogen gas dryers in hydrogen industry.

Viscous dissipation effects on entropy generation in heated vertical parallel-plate channels for mixed convection

In this study, effect of viscous dissipation on entropy generation for fully developed incompressible laminar flow mixed convection in vertical parallel-plate channels with asymmetric and symmetric uniform heat fluxes was parametrically analysed. Analytical equations were derived by using continuum approach and perturbation method. A specific MATLAB code was created to solve the governing equations. The effects of Gr/Re, the Brinkman number, and the ratio of wall heat flux on the entropy generation are presented and discussed. It is concluded that viscous dissipation has a significant effect on the entropy generation for mixed convection in heated vertical parallel-plate channels. Entropy generation resulting from fluid friction goes up, however, entropy generation due to heat transfer decreases by increasing of viscous dissipation. Consequently, it can be said that, this study will contribute to literature in optimising the systems that operates under mixed convection conditions in the vertical parallel-plate configuration.

Exergetic Analysis of a Vertical Ground-Source Heat Pump System with Wall Heating/Cooling

The present study deals with an exergetic analysis and assessment of a Vertical Ground-Source Heat Pump System (VGSHP) combined with a Wall Heating System (WHCS) in a building. This study is an experimental investigation of a real building’s heating system. The system is located at Yildiz Renewable Energy House (YREH) in Yildiz Technical University and fulfills the heating demand of YREH and a living room of the neighboring dormitory. In order to validate an exergetic model, the system is divided into three subsystems: (1) the ground coupling circuit, (2) the refrigerant circuit, and (3) the WHS circuit. The schematic diagram of the constructed experimental system is given in Fig. 26.1. Exergetic model is obtained by applying mass, energy, and exergy equations for each system component. YREH has four rooms, each has 8 m2 floor area, and the neighboring dormitory has a 50 m2 living room. In this study three rooms of YREH and the living room have been heated during heating season. The heating season was assumed to be between 1 January and 31 March. As average results on the heating season, 6.509 kW heat energy was extracted from ground and 5.799 kW was used in the WHS. In this process electrical energy consumption of system components are as follows: compressor 1.711 kW, ground heat exchanger pump 0.092 kW, accumulator tank circulation pump 0.114 kW, and WHS circulation pump 0.108 kW. For heating season, calculated overall system efficiency was 67.36 % while GSHP unit’s efficiency was 85 %. In addition, overall system COP was 2.76, while GSHP unit’s COP was 4.13. Total exergy destruction was found 1.759 kW and largest exergy destruction has occurred in the compressor as 0.714 kW. The exergy efficiency values for the individual components of the system have been found ranging from 58.3 to 98.4 % according to P/F concept. It is expected that the model would be beneficial for evaluating low exergy heating systems which use ground source as a renewable energy.

Comparison of Energy Performance and Static Loads on a Building Integrated Wind, Solar, and Rainwater Harvester

In recent years, sustainable energy and green buildings are developed as important issues. Many helpful systems were developed to profit from advantages of different renewable energy sources. However, the research on disadvantages of sustainable energy systems is very rare and papers focus on only economic issues. In this paper, an innovative building integrated wind, solar, and rainwater harvester (WSRH) system was analyzed by nonlinear static pushover (NSP) analysis. The results are compared in terms of energy performance and its effects on the structural system.