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Öğe Advanced exergoeconomic analysis with using modified productive structure analysis: An application for a real gas turbine cycle(Pergamon-Elsevier Science Ltd, 2021) Uysal, Cuneyt; Kecebas, AliIn this study, advanced exergoeconomic analysis is performed for a gas turbine cycle located in Inchon/ South Korea. In addition, an approach combining advanced exergy analysis with modified productive structure analysis is applied to the system and the results are compared. Both methods showed that higher part of exergy destruction cost rate for overall system was unavoidable. The investment cost rate of system equipment was also unavoidable. Avoidable exergy destruction cost rate was higher than unavoidable part only for gas turbine. The exergy destruction cost rates obtained with approach are considerably lower than the results obtained with the advanced exergoeconomic analysis. This situation affected the strategies developed to obtain a cost-effective system for gas turbine. Advanced exergoeconomic analysis proposed reducing the exergy destruction cost rate for gas turbine. However, for gas turbine, the approach proposed reducing the investment cost rate. The sum of exergy destruction cost rate of system equipment was higher than that of overall system in advanced exergoeconomic analysis. However, the exergy destruction cost rate of overall system was equal to the sum of exergy destruction cost rate of system equipment in the approach. Finally, it can be concluded that the results obtained with the approach were more compatible. ? 2021 Elsevier Ltd. All rights reserved.Öğe A comparative assessment of SPECO and MOPSA on costing of exergy destruction(Inderscience Enterprises Ltd, 2020) Uysal, Cuneyt; Ozen, Dilek Nur; Kurt, Huseyin; Kwak, Ho YoungThis paper presents the comparison of specific exergy costing (SPECO) and modified productive structure analysis (MOPSA) method to test their abilities on costing of exergy destruction. MOPSA method is applied to a combined supercritical CO(2)regenerative cycle and organic Rankine cycle using zeotropic mixtures for gas turbine waste heat recovery system. The results obtained with applying SPECO method to the system are taken from literature. The exergy destruction cost rate of overall system is obtained to be $86.08/h and $1,113.13/h for MOPSA and SPECO methods, respectively. The exergoeconomic factor of overall system is found to be 31.88% for SPECO method, while this value is found to be 85.82% for MOPSA method. The obtained results with applying MOPSA method for exergy destruction cost rate are significantly lower and more consistent compared to the results obtained by SPECO method.Öğe Energy, exergy, economic and sustainability assessments of a compression ignition diesel engine fueled with tire pyrolytic oil - diesel blends(Elsevier Sci Ltd, 2020) Karagoz, Mustafa; Uysal, Cuneyt; Agbulut, Umit; Saridemir, SuatEvery year, millions of tons of tire become unusable around the world and waste tire dumps threaten human health and the environment. Therefore, recycling of waste tires has attracted attention recently. In this study, energy, exergy, economic and sustainability analyses of a compression ignition diesel engine fueled with tire pyrolytic oil-diesel blends were performed and the results were compared with that of neat diesel. Tire pyrolytic oil was produced from waste tires with vacuum pyrolysis technique. Hydro-sulfuric acid treatment, vacuum distillation and oxidative desulfurization processes were applied to reduce emission values of tire pyrolytic oil. Tire pyrolytic oil was blended with neat diesel as 10 vol% (TPO10D90), 30 vol% (TPO30D70) and 50 vol% (TPO50D50). The test engine was single-cylinder, four-stroke, naturally aspirated, compression ignition diesel engine and the experiments were conducted for different test engine loads of 3 Nm, 6 Nm, 9 Nm and 12 Nm at constant crankshaft speed of 2000 rpm. The highest energy and exergy efficiencies were obtained for TPO10D90, while the lowest ones were obtained for neat diesel. At 12 Nm, the energy efficiency of test engine was obtained to be 26.89% for neat diesel and 28.15% for TPO10D90, while the exergy efficiency of test engine was found to be 25.19% for neat diesel and 26.36% for TPO10D90. The energy loss per capital investment cost was obtained to be 0.87 x 10(-4) kW/$ for TPO10D90 and 1.03 x 10(-4) kW/$ for neat diesel at 3Nm. At 12 Nm, the highest sustainability index was determined to be 1.358 for TPO10D90, while the lowest sustainability index was 1.337 for neat diesel. Results showed that TPO10D90 had better performance at each test engine load in terms of energy, exergy, economic and sustainability and the increase in tire pyrolytic oil content of blend made the results worse but better than neat diesel. As a conclusion, it can be said that tire pyrolytic oil production from waste tires is important fact from the viewpoint of both waste management and protection of fossil fuel resources depletion. (C) 2020 Elsevier Ltd. All rights reserved.Öğe ENTROPY GENERATION OF ZIRCONIA-WATER NANOFLUID FLOW THROUGH RECTANGULAR MICRO-CHANNEL(Vinca Inst Nuclear Sci, 2018) Uysal, Cuneyt; Arslan, Kamil; Kurt, HuseyinThe fluid flow and heat transfer characteristics and entropy generation of zirconia, ZrO2-water, nanofluid flow through a rectangular micro-channel are numerically investigated. The flow is considered under single-phase 3-D steady-state incompressible laminar flow conditions. The constant heat flux is applied to the bottom surface of micro-channel. The finite volume method is used to discretize the governing equations. As a result, the average Nusselt number decreases with increasing nanoparticle volume fraction, while the average Darcy friction factor is not affected. Moreover, the total entropy generation decreases with increase in nanoparticle volume fraction, while the Bejan number is almost not affected.Öğe Estimation of Entropy Generation for Ag-MgO/Water Hybrid Nanofluid Flow through Rectangular Minichannel by Using Artificial Neural Network(Gazi Univ, 2019) Uysal, Cuneyt; Korkmaz, Mehmet ErdiThe convective heat transfer and entropy generation characteristics of Ag-MgO/water hybrid nanofluid flow through rectangular minichannel were numerically investigated. The Reynolds number was in the range of 200 to 2000 and different nanoparticle volume fractions were varied between phi = 0.005 and 0.02. In addition, Artificial Neural Network was used to create a model for estimating of entropy generation of Ag-MgO/water hybrid nanofluid flow. As a result, it was found that the convective heat transfer coefficient for phi = 0.02 Ag-MgO/water hybrid nanofluid is 21.29% higher than that of pure water, at Re=2000. Total entropy generation of Ag-MgO/water hybrid nanofluid increased with increasing nanoparticle volume fraction. The results obtained by ANN showed good agreement with the numerical results obtained in this study.Öğe Exergetic and exergoeconomic analyses of a CI engine fueled with diesel-biodiesel blends containing various metal-oxide nanoparticles(Pergamon-Elsevier Science Ltd, 2021) Karagoz, Mustafa; Uysal, Cuneyt; Agbulut, Umit; Saridemir, SuatComprehensive exergetic and exergoeconomic analyses of a single-cylinder, four-stroke, naturally aspirated compression ignition (CI) diesel engine were conducted in the present paper. Exergy-based sustainability indicators were also determined in the study. The test engine was fueled with diesel fuel (D100), %90 diesel+10% waste cooking oil methyl ester blend (D90B10), D90B10 with Al2O3 nanoparticle of 100 ppm (D90B10Al(2)O(3)), D90B10 with TiO2 nanoparticle of 100 ppm (D90B10TiO(2)), and D90B10 with SiO2 nanoparticle of 100 ppm (D90B10SiO(2)) nanofuels, separately. The tests were performed at a constant engine speed of 2000 rpm and at varying engine loads from 2.5 to 10 Nm with an increment of 2.5 Nm. As a result, the exergy efficiencies of the test engine for D90B10 and D90B10Al(2)O(3) were determined to be 25.57% and 28.12%, respectively. The lowest cost flow rate of crankshaft work was found to be 0.4247 US$/h at 2.5 Nm, 0.5154 US$/h at 5 Nm for D90B10Al(2)O(3), and 0.6029 US$/h at 7.5 Nm, 0.7253 US$/h at 10 Nm for D90B10SiO(2). At 10 Nm, the highest and lowest sustainability index values were determined to be 1.391 for D90B10Al(2)O(3) and 1.344 for D90B10, respectively. From the perspective of exergy and sustainability, D90B10Al(2)O(3) had the best results. Besides, from the perspective of exergoeconomics, D90B10Al(2)O(3) had the best results at lower engine loads. As a conclusion, it can be said that nanofuels showed better performances compared to neat diesel fuel and diesel-biodiesel blend in the terms of in terms of exergy, exergoeconomics, and sustainability analyzes. Considering all analyses together, it is noticed that Al2O3-doped nanofuel is the best test fuel for this study, and then it is followed by SiO2 and TiO2-doped nanofuels, respectively. (C) 2020 Elsevier Ltd. All rights reserved.Öğe Exergetic and exergoeconomic analyses of a diesel engine fueled with binary and ternary blends of diesel-palm oil biodiesel-diethyl ether for various injection timings(Springer, 2022) Uysal, Cuneyt; Uslu, Samet; Aydin, MustafaIn this study, ten different blends were prepared with binary and ternary combinations of diesel, palm oil biodiesel (0 vol%, 15 vol%, 20 vol% and 30 vol%), and diethyl ether (0 vol%, 5 vol% and 10 vol%) and were tested in a diesel engine. The experiments were performed on various engine loads (500 W, 750 W, 1000 W and 1250 W) and various injection timings (25 degrees CA bTDC, 30 degrees CA bTDC and 35 degrees CA bTDC) at a fixed crankshaft speed of 3000 rpm. The prepared blends were compared in terms of exergy and exergoeconomics. It may be said that exergy efficiency and specific exergy cost of work for blends improved with increasing injection timings at high engine loads. However, at low engine loads, these parameters worsened with increasing injection timings. As a result, at 500 W, relative exergy efficiency of D70PO20DE10 was 0.57 for 25 degrees CA bTDC and 0.54 for 35 degrees CA bTDC. However, at 1250 W, this value was 0.59 for 25 degrees CA bTDC and 1.16 for 35 degrees CA bTDC. Similarly, at 500 W, relative specific exergy cost of work for D70PO20DE10 was 5.29 for 25 degrees CA bTDC and 5.94 for 35 degrees CA bTDC. However, at 1250 W, this value was 5.31 for 25 degrees CA bTDC and 2.66 for 35 degrees CA bTDC. Finally, it can be concluded that neat diesel had the best results compared to all blends considered in this study in terms of exergy and exergoeconomics.Öğe Exergetic and exergoeconomic assessments of a diesel engine fuelled with waste chicken fat biodiesel-diesel blends(Pergamon-Elsevier Science Ltd, 2024) Gad, M. S.; Uysal, Cuneyt; El-Shafay, A. S.; Agbulut, UemitResearchers have constantly been looking for renewable alternative fuels due to high fuel price volatility, energy security concerns, and produced harmful emissions. One of the promising alternatives is to produce biodiesel from waste economical feedstock such as chicken fat. Esterification and transesterification are used to create methyl ester from chicken fat. Then, 25%, 50%, 75%, and 100% of chicken oil biodiesel are volumetrically blended with diesel fuel. Diesel engine is loaded between 0% and 100% at 3000 rpm rated speed. Exergetic and exergoeconomic assessments of diesel engine fuelling with blends of chicken biodiesel were conducted in the present study. Diesel oil performed most efficiently in terms of exergy. For B100, the worst exergetic results are attained. The exergy efficiency of test engine at 75% engine load was 33.25% for the D100 and 27.85% for the B100. D100 produced the best exergoeconomic findings, while adding biodiesel to D100 made the exergoeconomic parameters worse. Crankshaft work had a particular exergy cost of 110.02 $/GJ for D100 and 194.37 $/GJ for B100 at 75% of engine output power. In the conclusion, it is noted that the waste chicken fat methyl ester can be used at low fractions as a substitute for traditional diesel fuel without modifying the engine, and this is a promising solution for waste management, turning waste products into an energy source, and dwindling fossil fuel reserves.Öğe Exergetic and exergoeconomic assessments of a diesel engine operating on dual-fuel mode with biogas and diesel fuel containing boron nitride nanoparticles(Springer, 2024) Uysal, Cuneyt; Agbulut, Umit; Topal, Halil Ibrahim; Karagoz, Mustafa; Polat, Fikret; Saridemir, SuatThis study investigates the exergetic and exergoeconomic analyses of a diesel engine operated on dual-fuel mode with fuelled both diesel fuel-boron nitride nanofuel and biogas purchased commercially. The experiments were performed for diesel fuel, diesel + 100 ppm boron nitride nanoparticle, diesel + 100 ppm boron nitride nanoparticle + 0.5 L min-1 biogas, diesel + 100 ppm boron nitride nanoparticle + 1.0 L min-1 biogas and diesel + 100 ppm boron nitride nanoparticle + 2.0 L min-1 biogas at various engine loads (2.5 Nm, 5.0 Nm, 7.5 Nm, and 10.0 Nm) and fixed crankshaft speed of 1500 rpm. The obtained experimental data were used to realize exergetic and exergoeconomic analyses. Among the fuels considered in this study, diesel + 100 ppm boron nitride nanoparticle nanofuel had the best exergetic and exergoeconomic results. As a result, at engine load of 10 Nm, the exergy efficiency of test engine and specific exergy cost of crankshaft work were obtained to be 29.12% and 124.86 US$ GJ-1 for diesel + 100 ppm boron nitride nanoparticle nanofuel, respectively. These values were 27.35% and 125.19 US$ GJ-1 for diesel fuel, 25.50% and 141.92 US$ GJ-1 for diesel + 100 ppm boron nitride nanoparticle + 0.5 L min-1 biogas, 23.10% and 156.33 US$ GJ-1 for diesel + 100 ppm boron nitride nanoparticle + 1.0 L min-1 biogas, and 21.09% and 171.92 US$ GJ-1 for diesel + 100 ppm boron nitride nanoparticle + 2.0 L min-1 biogas, respectively. It is clear that biogas addition to combustion made worse the exergetic and exergoeconomic performances of test engine. As a conclusion, it can be said that diesel + 100 ppm boron nitride nanoparticle nanofuel can be used as alternative fuel to D100 in terms of exergy and exergoeconomics.Öğe Exergetic and thermoeconomic analyses of a coal-fired power plant(Elsevier France-Editions Scientifiques Medicales Elsevier, 2017) Uysal, Cuneyt; Kurt, Huseyin; Kwak, Ho-YoungExergetic and thermoeconomic analyses of a coal-fired power plant with 160 MW capacity where located in Turkey were performed. Specific Exergy Costing (SPECO) and Modified Productive Structure Analysis (MOPSA) methods were separately applied to the system to determine the unit exergy cost of electricity generated by the coal-fired plant. The differences of these methods were discussed. As a result, the exergy efficiency of coal-fired power plant is found to be 39.89%. The equipment having the highest improvement potential is determined as boiler. The unit specific exergy cost of electricity generated by the system obtained for SPECO and MOPSA thermoeconomic analysis methods are 12.14 US$/GJ and 14.06 US$/GJ, respectively. The unit specific exergy cost of electricity obtained by using MOPSA thermoeconomic method is the same as the one obtained by the overall cost-balance equation for the coal-fired power plant. (C) 2017 Elsevier Masson SAS. All rights reserved.Öğe Exergetic, exergoeconomic, and sustainability analyses of diesel-biodiesel fuel blends including synthesized graphene oxide nanoparticles(Elsevier Sci Ltd, 2022) Uysal, Cuneyt; Agbulut, Uemit; Elibol, Erdem; Demirci, Tuna; Karagoz, Mustafa; Saridemir, SuatIn this study, graphene oxide nanoparticles were synthesized and added to 85 vol% diesel + 15 vol% biodiesel (D85B15) blend with amounts of 100 ppm, 500 ppm, and 1000 ppm to prepare D85B15GO100, D85B15GO500, and D85B15GO1000 blends, respectively. The prepared fuels were tested in a compression ignition diesel engine. The experiments were performed on various engine loads ranging from 3 Nm to 12 Nm with intervals of 3 Nm at fixed crankshaft speed of 2400 rpm. The results obtained from the experiments were used in the exergetic, exergoeconomic, and sustainability analyses of test engine. According to the results, D85B15GO100 had the highest exergy efficiency and sustainability index and the second-cheapest specific exergy cost of crankshaft work. As a result, at 12 Nm, the exergy efficiency, specific exergy cost of work produced by crankshaft, and sustainability index values of test engine were 25.82%, 75.82 $/GJ, 1.348 for D85B15, whereas these values were 27.05%, 77.52 $/GJ, 1.371 for D85B15GO100, respectively. Increase in graphene oxide nanoparticle content in the blend led to decrease in the exergy efficiency and sustainability index and increase in the specific exergy cost of crankshaft work. Finally, it can be concluded that D85B15GO100 is optimal fuel compared to the fuels tested in this study.Öğe Exergy analysis of a spark ignition engine for different crankshaft speeds(Pamukkale Univ, 2019) Ozdalyan, Bulent; Uysal, Cuneyt; Kurt, HuseyinIn this study, a spark ignition (SI) engine performance is exergetically investigated for different crankshaft speeds. The test engine is VSG413 SI type engine fueled with 95 octane gasoline. The test engine has 1.3 l volume, four stroke, four cylinder, 45 kW maximum power capacity and 98 Nm maximum torque capacity. The experiments are realized under fully loaded test conditions. The crankshaft speed is changed between 1200 rpm and 5000 rpm. In the calculations, actual operating data obtained by experiments are used. It is found that maximum energy and exergy efficiencies are obtained at crankshaft speed of 2500 rpm, which are 29.78% and 27.77%, respectively. Entropy generation rate increases with increase in crankshaft speed and ranged from 0.059 kW/K to 0.253 kW/K for all study.Öğe Exergy, exergoeconomic, life cycle, and exergoenvironmental assessments for an engine fueled by diesel-ethanol blends with aluminum oxide and titanium dioxide additive nanoparticles(Elsevier Sci Ltd, 2022) Agbulut, Umit; Uysal, Cuneyt; Cavalcanti, Eduardo J. C.; Carvalho, Monica; Karagoz, Mustafa; Saridemir, SuatThis study develops energy, exergy, exergoeconomic, exergoenvironmental, and sustainability analyses for a compression ignition (CI) engine fueled with neat diesel (D100), 90 vol% neat diesel + 10 vol% ethanol (D90E10), D90E10 + 100 ppm Al(2)O(3 )nanoparticle (D90E10Al(2)O(3)), and D90E10 + 100 ppm TiO2 nanoparticle (D90E10TiO(2)). The experiments were performed on various engine loads (from 3 Nm to 12 Nm with 3 Nm increments) at a fixed crankshaft speed of 2400 rpm. D90E10Al(2)O(3) showed the best energy, exergy, exergoenvironmental, and sustainability results among all fuels. However, according to exergoeconomic analysis, the lowest cost of crankshaft work was obtained with D100, followed by D90E10Al(2)O(3). This means that D90E10Al(2)O(3) presented better exergoeconomic results than its base fuel D90E10 and D90E10TiO(2) but worse exergoeconomic results than D100. The addition of ethanol to D100 excessively increased the fuel cost. As a result, the crankshaft work cost flow rate is 0.7645 $/h for D100, 1.1123 $/h for D90E10, 1.1069 $/h for D90E10Al(2)O(3) and 1.1338 $/h for D90E10TiO(2). Similarly, the environmental impact rate of work is 250.8 mPt/h for D100, 264.2 mPt/h for D90E10, 245.6 mPt/h for D90E10Al(2)O(3 )and 248.7 mPt/h for D90E10TiO2. Increments in the engine load have led to increases in all environmental impact rates due to higher fuel consumption but caused a decrease in the environmental impact rate per exergy unit. In conclusion, it is well noticed that fuel blends with nanoparticles can be used as alternative fuels to their base fuels, but D100 (or an equivalent lower-cost fuel than D100) should be selected for cost-effectiveness purposes.Öğe A new approach to advanced exergoeconomic analysis: The unit cost of entropy generation(Wiley, 2020) Uysal, CuneytAdvanced exergoeconomic analysis is based on costing of avoidable/unavoidable and endogenous/exogenous exergy destruction rates obtained with advanced exergy analysis. For this purpose, the unit cost of fuel of any system (c(F)) is used. In this study, a unit cost term, which is called as unit cost of entropy generation (c(S)), is assigned for exergy destruction rate and is used on costing of exergy destruction terms. Modified Productive Structure Analysis (MOPSA) thermoeconomic method is used to determine the unit cost of entropy generation value. Approach proposed in this study is applied to an electricity-generating facility that operates with natural gas. As a result, the unit cost of entropy generation value for the considered system is calculated to be -1.5748 $/GJ. In addition, it is found that the exergy destruction cost rates obtained with approach proposed in this study are lower compared to that of advanced exergoeconomic analysis.Öğe A Numerical Analysis of Fluid Flow and Heat Transfer Characteristics of ZnO-Ethylene Glycol Nanofluid in Rectangular Microchannels(Assoc Mechanical Engineers Technicians Slovenia, 2016) Uysal, Cuneyt; Arslan, Kamil; Kurt, HuseyinThe fluid flow and heat transfer characteristics of ZnO-Ethylene glycol (EG) nanofluid through rectangular microchannels having different aspect ratios (a is 1 to 2) are numerically investigated. The different nanoparticle volume percentages (phi is 1 % to 4 %) of ZnO-EG nanofluid are used. The flow is considered under single-phase, three-dimensional, steady-state, incompressible, thermally developing, laminar flow conditions. As a result, the microchannel with an aspect ratio value of 1 has the highest convection heat transfer coefficient and the lowest pressure drop. It is also observed that the convection heat transfer coefficient and pressure drop increases with an increase in nanoparticle volume fraction value of nanofluid. However, the Nusselt number decreases with increasing nanoparticle volume fraction, while the Darcy friction factor is not affected.Öğe Rebuttal letter to the article entitled as Exergy analysis and nanoparticle assessment of cooking oil biodiesel and standard diesel fueled internal combustion engine by I. Yildiz, H. Caliskan, K. Mori, Energy and Environment 31(8) (2020) 1303-1317(Sage Publications Ltd, 2024) Uysal, CuneytThis rebuttal letter reports some physical facts, which are contradictory with known physical facts, in the article entitled Exergy analysis and nanoparticle assessment of cooking oil biodiesel and standard diesel fueled internal combustion engine by I. Yildiz, H. Caliskan, K. Mori, Energy and Environment 31(8) (2020) 1303-1317.Öğe Role of Waste Cost in Thermoeconomic Analysis(Mdpi, 2020) Uysal, Cuneyt; Kwak, Ho-YoungPower plants or thermal systems wherein products such as electricity and steam are generated affect the natural environment, as well as human society, through the discharging of wastes. The wastes from such plants may include ashes, flue gases, and hot water streams. The waste cost is of primary importance in plant operation and industrial ecology. Therefore, an appropriate approach for including waste cost in a thermoeconomic analysis is essential. In this study, a method to take waste cost into account in thermoeconomics to determine the production cost of products via thermoeconomic analysis is proposed. The calculation of the waste cost flow rates at the dissipative units and their allocation to system components are important to obtain the production cost of a plant.Öğe THERMOECONOMIC ANALYSIS OF T56 TURBOPROP ENGINE UNDER DIFFERENT LOAD CONDITIONS(Turkish Soc Thermal Sciences Technology, 2020) Ozen, Dilek Nur; Uysal, Cuneyt; Balli, OzgurIn this study, T56 turboprop engine was theoretically modelled for 75% load, 100% load, military (MIL) mode, and Take-off mode conditions. For each load conditions, thermoeconomic analyses of T56 turboprop engine were performed to allocate the unit costs of shaft work and thrust and to determine exergy destruction cost rates for system equipment. In thermoeconomic analyses, Specific Exergy Costing (SPECO) and Modified Productive Structure Analysis (MOPSA) methods were used. MOPSA method gave higher unit cost values for shaft work and thrust compared to SPECO method. As a result, for Take-off mode, the unit cost of shaft work transferred to propeller was determined to be 78.87 $/GJ in SPECO method, while this value was calculated to be 84.68 $/GJ with MOPSA method. The unit cost of negentropy of T56 turboprop engine decreased with increasing in engine load and ranged from 14.98 $/GJ to 11.08 $/GJ. The exergy destruction cost rates obtained with MOPSA method for the system equipment were considerably lower than the results obtained with SPECO method. For instance, in Take-off mode, exergy destruction cost rate of combustion chamber was calculated to be 865.10 $/h in SPECO method, whereas it was calculated to be 247.94 $/h in MOPSA method. The exergoeconomic factor of overall system was determined to be 23.07% in SPECO method, and 54.16% in MOP SA method for Take-off mode.Öğe Thermoeconomic diagnosis of an air-cooled air conditioning system(Inderscience Enterprises Ltd, 2018) Yoo, Yungpil; Oh, Hoo-Suk; Uysal, Cuneyt; Kwak, Ho-YoungDiagnosis of a 120-kW air-cooled air conditioning system under faulty conditions was performed using modified productive structure analysis. Unit cost of cooling capacity for the system and lost cost flow rate for components were calculated based on data obtained by using a simulator for the cases of pre-fixed faulty and normal operating conditions. The relative malfunction (RMF) and the relative difference in the lost cost flow rate between real and normal operations (RDLC) were found to be effective indicators to identify the malfunction components. Results revealed that malfunction due to fouling at the condenser and evaporator, compressor valve leakage, the superheating in the suction line and refrigerant undercharge, whose fault levels by the percent degradation induced in the cooling capacity are 3.4%, 10.5%, 15.1%, 3.5% and 4.1%, respectively, can be identified. Unit cost of the cooling capacity of the system increases when malfunction occurs at any component in the air conditioning system.Öğe WHICH PARAMETER SHOULD BE USED IN EVALUATING NANOFLUID FLOWS: REYNOLDS NUMBER, VELOCITY, MASS FLOW RATE OR PUMPING POWER?(Begell House Inc, 2020) Uysal, CuneytThe heat transfer, fluid flow, and entropy generation characteristics of a diamond-Fe3O4/water hybrid nanofluid are investigated numerically for different nanoparticle volume fractions under laminar flow conditions. In addition, diamond/water and Fe3O4/water nanofluids are investigated to compare with their hybrid form. The results are presented at the given Reynolds number, velocity, mass flow rate, and pumping power. As a result, overabundant enhancements are observed in thermal performances of nanofluids when evaluation is realized for the same Reynolds number. At Re = 2000, a diamond-Fe3O4/water hybrid nanofluid (phi = 0.2%) provides a convective heat transfer enhancement of 30.31%. However, at V = 1.3 m/s, the convective heat transfer coefficient obtained for a diamond-Fe3O4/water hybrid nanofluid (phi = 0.2%) is 2.17% higher than that of pure water. It is also observed that pure water has a better convective heat transfer rate compared to a diamond-Fe3O4/water hybrid nanofluid when the evaluation is performed at the same pumping power. Among all evaluation parameters, it is found that there is a minimum entropy generation point. Although it is difficult to decide, but the results obtained with evaluation performed at the same velocity or the same pumping power can be more realistic and reasonable.
