38 research outputs found
Thermodynamic analysis and performance improvement of Irem geothermal power plant in Turkey: A case study of organic Rankine cycle
No full textRenewable and environmentally friendly energy sources are becoming increasingly important nowadays. This growth in importance also has an effect on the energy conversion systems using more eco-friendly and renewable energy sources (geothermal, wind, solar) than fossil fuels, the use of which has been reduced these days (oil, coal, natural gas, etc.). From this perspective, renewable energy sources and the conversion efficiency of the facilities which use these sources have also gained importance. The purpose of this study is to calculate the energy and exergy efficiency of the Irem binary cycle geothermal power plant located in Germencik-Aydn, Turkey geothermal area. Data measured in the power plant were used in the calculations, and correlations were developed depending on the ambient temperature. In addition, exergoeconomic analysis was performed by taking into account the total cost of the power plant (investment and maintenance costs). The greatest energy (97,805.34 kW) and exergy (6463.8 kW) losses were observed in the air-cooled condenser. The first law efficiency and the second law efficiency of the power plant were found to be 5.89% and 33.8%, respectively. Furthermore, a model was proposed for 6 different refrigerants with the purpose of investigating the availability of the waste heat and consists of a numerical thermodynamic optimization of the model in this study. (c) 2017 American Institute of Chemical Engineers Environ Prog, 37: 1523-1539, 201
Performance comparison of plate heat exchangers designed using Taguchi method and computational fluid dynamics
No full textIn this study, thermal and hydraulic performances of cross flow plate heat exchangers, designed using Taguchi method and Computational Fluid Dynamics, in a small capacity (50-200 m(3)/h) air to air heat recovery device were compared. The plate heat exchangers, which are designed to have high flow effectiveness and sensible effectiveness, number of sub-channel, channel height, average air velocity and sheet material variables were determined. The equations for flow effectiveness and recovered thermal power, including variables and second order interactions of variables, were derived by multiple regression analysis for flow effective and thermally effective plate heat exchangers. The performances of 3-dimensional plate heat exchangers using finite volume based ANSYS/Fluent were compared in different volumetric flow rates. The channel height and average air velocity were determined as the most influential variables in the design of plate heat exchanger. It was found that on average 50% more heat was recovered and thermal effectiveness was on average 35% higher in the thermal effective model, while pressure drop was on average 2.5 times less and flow effectiveness was on average 10% higher in the flow effective model When the recovered thermal power at the fresh side and flow effectiveness are evaluated together, the optimum average flow velocities for both models was determined to be range of 1.5-2 m/s (similar to 90 divided by similar to 110 m(3)/h)
CHARACTERISTICS OF HEAT TRANSFER AND PRESSURE DROP IN A CHEVRON-TYPE PLATE HEAT EXCHANGER WITH Al2O3-WATER NANOFLUIDS
No full textIn this study, heat transfer and pressure drop characteristics have been experimentally investigated by using Al2O3-water nanofluids in the chevron-type plate heat exchanger. The purpose of the experiments was to determine the heat transfer coefficient and pressure drop for different flow rates of 90, 120, 150, 180, 240, and 300 kg/h and different volume concentrations of 0.25%, 0.5%, 0.75%, and 1% of the nanofluids. The Nusselt number of the nanofluids increased with the increasing volume concentration and flow rate at constant hot water flow rate and constant inlet temperatures. The increase in the Nusselt number is 42.4% when compared to distilled water at the maximum volume concentration and Reynolds number (600 <= Re <= 1900) in the nanofluids plate heat exchanger. It has been concluded that nanofluids enhanced the heat transfer significantly and pressure drops at the maximum volume concentration and the Reynolds number increased by between 6.4% and 8.4% compared to distilled water
Performance analysis of Germencik Geothermal Power Plant
No full textThe objective of this study is to calculate the efficiency of exergy in Germencik Geothermal Power Plant, which has a power output of 47.4 MWe. As being the largest one in Turkey, this plant is operated by double-flash system which is based on the method of analysis of energy and exergy to evaluate its performance. The exergy analysis has been applied to the whole plant considering the first and the second laws of thermodynamics for each equipment. In this study, by using the actual data values the losses of exergy have been determined and the flow diagram of exergy has been illustrated. When making calculations, we have accepted dead state temperature as 15 degrees C, and dead state pressure as 101.325 kPa s. The plant has 7 production and 6 reinjection wells. From these production wells, geothermal fluid reaches the plant at an average temperature ranging from 194 degrees C to 214 degrees C, pressure of 23 bars-30 bars and a total flow rate of 688.87 kg/s. An exergy input of 134,124 kW is obtained from these wells. The largest exergy input of 36,395 kW is obtained from OB-14 and this accounts for 27.1% of total exergy input. Moreover, major exergy losses and their exergy input account for 3.34% (4478 kW) for valves, 22.72% (30,477 kW) for high and low-pressure separation process during the decomposition of geothermal fluid, 5.1% (6837 kW) for turbine-generator during the conversion of steam into mechanic work, 9.41% (12,622 kW) for cooling tower, 5.53% (7414 kW) for internal use, and finally 22.68% (30,415 kW) for reinjection wells. Additionally, the second law efficiency of turbine-generator has been found to be 87.4% and the second law efficiency of overall plant has been found to be 3534%. The obtained results have been given in tables and the largest loss of exergy has been determined to occur in separators. (C) 2013 Elsevier Ltd. All rights reserved
IOP Conference Series-Earth and Environmental Science
No full textIn this study, the availability of waste heat in a power generating capacity of 47.4 MW in Germencik Geothermal Power Plant has been investigated via binary geothermal power plant. Refrigerant fluids of 7 different single components such as R-134a, R-152a, R-227ea, R-236fa, R-600, R-143m and R-161 have been selected. The binary cycle has been modeled using the waste heat equaling to mass flow rate of 100 kg/s geothermal fluid. While the inlet temperature of the geothermal fluid into the counter flow heat exchanger has been accepted as 110 degrees C, the outlet temperature has been accepted as 70 degrees C. The inlet conditions have been determined for the refrigerants to be used in the binary cycle. Finally, the mass flow rate of refrigerant fluid and of cooling water and pump power consumption and power generated in the turbine have been calculated for each inlet condition of the refrigerant. Additionally, in the binary cycle, energy and exergy efficiencies have been calculated for 7 refrigerants in the availability of waste heat. In the binary geothermal cycle, it has been found out that the highest exergy destruction for all refrigerants occurs in the heat exchanger. And the highest and lowest first and second law efficiencies has been obtained for R-600 and R-161 refrigerants, respectively
Experimental investigation of heat transfer and pressure drop in a mini-channel shell and tube heat exchanger
No full textThis study experimentally investigated heat transfer and pressure drop on tube side of a mini-channel shell and tube heat exchanger (MC-STHE) prototype designed and manufactured using Kern method. Mini-channel copper tubes with an inner diameter of 2mm and a length of 240mm were used on the tube side of the MC-STHE. Baffles with a 25% baffle cut and a shell with an inner diameter of 30mm were used on the shell side. The Reynolds number on the tube side was changed from 1000 to 10,000 while that on the shell side was kept constant at 680. The experimental convective heat transfer coefficients and friction factors for the tube side were compared with correlations for macro-pipes commonly used in the literature. The experimental convective heat transfer coefficients were in good agreement with the Shah and Sieder-Tate correlations in the laminar region and in good agreement with the Petukhov, Hausen and Gnielinski correlations in the transition region while the experimental friction factors showed a similar tendency to the correlation modified by Shah. In addition, the Nusselt number and friction factor correlations have been proposed for use in designing similar MC-STHEs. The optimal operating range of Reynolds number for MC-STHEs is 4000<Re <5000 based on the Colburn factor while it is 4000<Re <6000 based on the flow area goodness factor
Experimental investigation of shell side heat transfer and pressure drop in a mini-channel shell and tube heat exchanger
No full textThis study experimentally investigated the shell side heat transfer and pressure drop of a mini-channel shell and tube heat exchanger (MC-STHE) designed and manufactured using Kern's method. A shell with an inner diameter of 30 mm and four horizontally oriented transverse baffles with a 25% baffle cut were used in the mini-channel heat exchanger. Using rotated triangular layout, the tube bundle was composed of 13 mini-channel copper tubes with an outer diameter of 3 mm and a length of 240 mm. The shell-side Reynolds numbers ranged from 250 to 2500 while the tube-side Reynolds number was kept constant at similar to 5900 based on the experimental surface flow area goodness factor (j/f) results. The shell side convective heat transfer coefficients and total pressure drop results were compared with correlations for macro tubes commonly used in the literature. The experimental convective heat transfer coefficients were in good agreement with the Kern design, VDI-HA and McAdam's correlations within the Reynolds numbers ranging from 250 to 2500. The experimental total pressure drop of the MC-STHE was 2.3 times higher than that of macro tube heat exchangers. In addition, the Nusselt number and Colburn factor correlations were proposed for the estimation of shell side convective heat transfer coefficient in MC-STHEs. The optimum working range for shell side is Re < 1000 according to surface flow area goodness factor by which heat transfer and hydrodynamic effects in MC-STHE are evaluated together. (C) 2019 Elsevier Ltd. All rights reserved
Numerical Investigation of Forced Convection Heat Transfer Performance of Al2O3 Water Nanofluids in Plate Heat Exchanger Channel
No full textEnhanced efficiency of CdS/P3HT hybrid solar cells via interfacial modification
No full textTomakin, Murat/0000-0003-1887-848X; UNVERDI, Ahmet/0000-0001-6144-1158; POLAT, ISMAIL/0000-0002-5134-0246The present paper examines the effects of surface modification of CdS with diverse dyes on fabricated CdS-based hybrid solar cells. the X-ray diffraction results showed that CdS thin films had a hexagonal phase with a preferred orientation along the (101) plane. Scanning electron microscopy indicated that the CdS specimen was composed of a granular structure while a P3HT layer was formed from tiny grains. Band gaps of the CdS thin films and the P3HT layer were 2.45 eV and 1.98 eV, respectively. the absorption spectra showed that different dye loading caused an increase in the absorbance of CdS thin films in the wavelength range of 400-650 nm. the photoluminescence of the CdS/P3HT structure including various dyes was lower than that of the pristine one, implying that efficient charge separation was achieved upon surface modification. Current density-voltage curves showed that the ITO/CdS/N719/Ag hybrid solar cell exhibited the best overall efficiency of 0.082%, which can be attributed to improvements in both short circuit current density (J(sc)) and open circuit voltage (V-oc). These enhancements can be attributed to the creation of better interfacial contact between CdS and P3HT layers after dye loading.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [116F296]The authors wish to thank the Scientific and Technological Research Council of Turkey (TUBITAK) for its financial support of this work (project number 116F296)
