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Koleksiyondaki öğeler
- MakaleAçık Erişim2013Scopus SJRQ1Solutions of an anisotropic nonlocal problem involving variable exponent
Avci, Mustafa; Ayazoglu, Rabil A.; Cekic, Bilal
The present paper deals with an anisotropic Kirchhoff problem under homogeneous Dirichlet boundary conditions, set in a bounded smooth domain Ω of ℝN (N ≥ 3). The problem studied is a stationary version of the original Kirchhoff equation, involving the anisotropic p→(.)-Laplacian operator, in the framework of the variable exponent Lebesgue and Sobolev spaces. The question of the existence of weak solutions is treated. Applying the Mountain Pass Theorem of Ambrosetti and Rabinowitz, the existence of a nontrivial weak solution is obtained in the anisotropic variable exponent Sobolev space W01p→(.) (Ω), provided that the positive parameter λ that multiplies the nonlinearity f is small enough.
AtıfScopus13WoS14OpenAlex9
İncele - BildiriYalnız künye2017Analysis of turbulent convective heat transfer from rectangular baffles by Taguchi method
Sahin, B.; Bayrakceken, A.; Manay, E.; Ates, I.
In this study, the effects of the rectangular baffles mounted on the bottom surface of a heat exchanger on the heat and pressure drop characteristics were investigated using the Taguchi experimental-design method. Nusselt number and friction factor were considered as performance parameters. An L18(2135) orthogonal array was selected as an experimental plan for the six parameters: corner angle (α), inclination angle (β), baffle height (H), baffle length (L), baffle width (S) and Reynolds number. First of all, each goal was optimized, separately. Then, all the goals were optimized together, considering the priority of the goals. The presence of the rectangular cross sectioned baffles caused higher pressure drop than that of the smooth channel. It was concluded that increasing inclination angle and corner angle caused heat transfer to decrease. The length of the baffle was found to be the most influential parameter on friction factor. Likewise, it was concluded that the most affected parameter on the heat transfer was Reynolds number.
- MakaleYalnız künye2018Scopus SJRQ3Energy and exergy analysis of a solid-oxide fuel cell power generation system for an aerial vehicle (ISSA- 2015–139)
Genç, Gamze; Sarikoç, Selçuk
This paper presents the performance of the solid-oxide fuel cell/gas turbine hybrid power generation system with heat recovery waste unit based on the energy and exergy analyses. The effect of air inlet temperature and air/fuel ratio on exergy destruction and network output is determined. For the numerical calculations, air inlet temperature and air fuel ratio are increased from 273 to 373 K and from 40 to 60, respectively. The results of the numerical calculations bring out that total exergy destruction quantity increases with the increase of air inlet temperature and air/fuel ratio. Furthermore, the maximum system overall first and second law efficiencies are obtained in the cases of air inlet temperature and air/fuel ratio equal to 273 K and 60, respectively, and these values are 62.09% and 54.91%.
AtıfScopus9WoS9OpenAlex12İncele - MakaleAçık Erişim2016Scopus SJRQ2Effect of external magnetic field on valence-electron structures of Fe and Ni in Invar, Permalloy and the other Fe-Ni alloys by using Kβ-to-Kα X-ray intensity ratios
Alim, Bünyamin; Han, Ibrahim; Demir, Lütfü
The effect of external magnetic field on the valence-electron structures of Fe and Ni in various Fe-Ni alloy compositions was investigated by using X-ray fluorescence spectroscopy. Kβ-to-Kα X-rayin-tensity ratios of Fe and Ni in Invar(Fe0.64Ni0.36), Permalloy(Fe0.20Ni0.80) and Fe N - i x 1x Firstly,(x=0, 0.40, 0.52, 0.55, 0.61, and 1) alloys were measured without any magnetic field and under 0.5 and 1 T external magnetic fields, separately. Later, the valence-electron structures of Fe and Ni in both pure form and alloys were obtained by comparison of measured X-ray intensity ratios with the results of multi-configurations Dirac-Fock (MCDF) calculations. The results obtained for valence-electron structures of Fe and Ni in various Fe-Ni alloys were evaluated in terms of magnetic field effect, delocalization and/or charge transfer phenomena. The results have shown that valence electron structure of Fe and Ni in Fe-Ni alloys are dependent on both external magnetic field and concentration of alloy elements.
AtıfScopus16WoS14OpenAlex17
İncele - MakaleAçık Erişim2018Scopus SJRQ1Determination of effective constitutive parameters of inhomogeneous metamaterials with bianisotropy
Hasar, Ugur Cem; Buldu, Gul; Kaya, Yunus; Ozturk, Gokhan
A recursive algorithm is proposed to accurately extract the electromagnetic parameters of isotropic/bianisotropic metamaterial (MM) slabs of inhomogeneous structures. The algorithm is based on the recursive calculations of measured/ simulated forward and backward scattering (S-) parameters from previously extracted wave impedances and refractive indices of each homogeneous layer (except the analyzed intermediate layer) by a suitable retrieval method. There are two main advantages of our proposed method over existing extraction algorithms. First, it could retrieve the electromagnetic parameters of both isotropic and bianisotropic MM slabs. Second, it is applicable for electromagnetic parameter extraction of inhomogeneous structures. For validation of our method and assessing its accuracy over existing extraction methods, we used the simulation results of various inhomogeneous structures constructed by different isotropic/bianisotropic MM slabs (split-ring-resonator (SRR), SRR-wire, omega, and omega-wire). For completeness, the effects of noise present in S-parameters and iterative error (by increasing the value of iteration numbers) are examined to test the robustness of the proposed algorithm.
AtıfScopus43WoS42OpenAlex47İncele - MakaleAçık Erişim2016Scopus SJRQ1Exergetic interrelation between an heat pump and components
Çakır, Uğur; Çomaklı, Kemal
In this study, the relation between the exergetic performance of the heat pump and its components are investigated experimentally by using an air to water heat pump. Moreover, the effects of the working conditions of the components on the exergetic performance of the system are exposed and discussed. An experimental air to water heat pump system was designed and built. The results were evaluated by comparing the components and heat pump according to their performances. 33–45% of the all destructed exergy of the heat pump system comes into existence in the compressor. The contribution of the condenser to the total exergy destruction rate of the heat pump is between 23% and 34%. Contribution of the compressor to the exergy destruction rate of heat pump decreases with an increase in the air temperature and it increases with a decrease in the air mass flow rate. Contribution of the compressor to the exergy destruction rate of heat pump decreases with an increase in the air temperature and it increases with a decrease in the air mass flow rate. In terms of exergetic performance of the heat pump, the importance and priority of the components vary with the heat source thermal conditions.
AtıfScopus15WoS14OpenAlex16İncele - MakaleYalnız künye2017Scopus SJRQ4Bioactive content of Rosa canina biotypes from Turkey
Beyhan, O.; Koc, A.; Ercisli, S.; Jurikova, T.; Cakir, O.
Rose hips have been used as medicinal and aromatic plants for a long time throughout Turkey. The plant has been the focus of many recent studies due to its potential effects on treatment and prevention of several diseases. However, there are few in vitro studies concerning its composition and antioxidant capacity. The aim of the present study was to determine bioactive content including ascorbic acid, total phenolics, total flavonoids, total carotenoids and antioxidant activity of Rosa canina biotypes growing wild in Sivas province located eastern Anatolia. The results revealed that fruits of Rosa canina biotypes rich in terms of Vitamin C which ranged from 360 to 482 mg/100 g fresh weight base. The total phenolic content varied from 340 to 464 mg/100 g fresh weight. The biotype S-07 had the highest total flavonoids content (241 mg quercetin equivalent/100 g fresh weight) and the lowest value attributed to biotype S-01 as 151 mg/quercetin equivalent/100 g fresh weight. The antioxidant activity of the biotypes was between 14.2-30.7 μg Trolox/ml sample. The results revealed that there was enough diversity among Rosa canina biotypes for bioactive content and promising biotypes with high bioactive content are ready material for future breeding activities.
AtıfScopus4İncele - BildiriAçık Erişim2017Scopus SJRQ3Thermodynamic performance assessment of different fluids in a typical organic Rankine cycle for usage in municipal solid waste power plant
Özahi, E.; Tozlu, A.; Abuşoǧlu, A.
This paper presents the energy and exergy analyses of some different organic fluids which can be used in an organic Rankine cycle adapted to a municipal solid waste power plant in the frame of energy recovery. The novelty of the study is to adapt a well-known organic Rankine cycle system theoretically to the existing municipal solid waste power plant where the exhaust gas with a temperature of almost 560 °C is sent to atmosphere causing both energy loss and air pollution, and also violating the related legislation. The efficient organic fluid that can be used in such a plant is estimated by means of the thermodynamic analyses. It is known that, in a typical municipal solid waste power plant, a considerable amount of energy is sent up from a plant chimney to the atmosphere. This waste energy can be utilized by using an adapted organic Rankine cycle system with a proper organic fluid. In this frame, some different organic fluids were examined and compared thermodynamically in this study. The optimal operation conditions of some organic fluids, R141b, isobutane, R245fa, n-pentane and n-hexane have been evaluated by means of ASPEN and EES software programs. The effects of the outlet temperature of heat source on the energetic and exergetic efficiencies and the net power output at a given pinch point temperature difference were investigated. It can be deduced from the analyses that n-hexane has the highest energetic and exergetic efficiencies at all outlet temperatures of the heat source such as 8.92% and 34.47% at 82.08°C, respectively. It can also be stated that the maximum net power output is obtained by using the organic fluid n-hexane.
AtıfScopus14WoS12OpenAlex13İncele - BildiriYalnız künye2015Evaluation of electromagnetic interference emitted from compact fluorescent lamps according to CISPR-15
Kocakusak, A.; Cakir, M.; Yalcin, S.; Ozen, S.; Helhel, S.
In this study, Electromagnetic interference (EMI) emitted by the compact fluorescent lamps (CFL) having biggest pie in the market has been investigated according to CISPR-15. Emissions of CFLs vary depending on trademark, since some cannot provide the requirements of CISPR-15 standards such that they act as contaminants in the electric supply system. Conducted analysis considering the limits of CISPR-15 at 150-500 kHz frequency brings out that the effect of CFL produced by Company A at 181.298 kHz is 83.94 dBμV, whereas the effect of CFL produced by Company D at 173.593kHz frequency is 49,92dBμV, respectively. Obtained results are out of CISPR-15 limits of 66-56 dBμV.
AtıfScopus2İncele - MakaleYalnız künye2016Scopus SJRQ2Optimum design of steel space frames under earthquake effect using harmony search
Artar, Musa
This paper presents an optimization process using Harmony Search Algorithm for minimum weight of steel space frames under earthquake effects according to Turkish Earthquake Code (2007) specifications. The optimum designs are carried out by selecting suitable sections from a specified list including W profiles taken from American Institute of Steel Construction (AISC). The stress constraints obeying AISC- Load and Resistance Factor Design (LRFD) specifications, lateral displacement constraints and geometric constraints are considered in the optimum designs. A computer program is coded in MATLAB for the purpose to incorporate with SAP2000 OAPI (Open Application Programming Interface) to perform structural analysis of the frames under earthquake loads. Three different steel space frames are carried out for four different seismic earthquake zones defined in Turkish Earthquake Code (2007). Results obtained from the examples show the applicability and robustness of the method.
AtıfScopus14WoS14OpenAlex7İncele - Derleme MakaleYalnız künye2018Scopus SJRQ1Green roofs and facades: A comprehensive review
Besir, Ahmet B.; Cuce, Erdem
Based on United Nations Environment Program (UNEP), building sector accounts for 40% of total energy consumption. In European countries, 36% of total greenhouse gas emissions is attributed to buildings. In this respect, green roofs are considered to be one of the most appropriate sustainable solutions to resolve the urban heat island-related issues. Roofs account for nearly 20–25% of overall urban surface areas. Energy saving, thermal insulation, shading and evapotranspiration features highlight the key role of green roofs in overall thermal performance of buildings and microclimatic conditions of indoor environments. Within the scope of this research, the concept of green roofs and facades is comprehensively analysed in a holistic and thematic way. Following a historical overview of the technology, the research is split into various subfields such as energy saving in buildings through greenery systems, multifunctional thermal benefits including evapotranspiration, thermal insulation, shading and thermal comfort features, evaporative cooling for reducing cooling demand and minimising wind driven convection losses. The results achieved from the literature survey clearly indicate that green roofs and facades are key solutions to mitigate building-related energy consumptions and greenhouse gas emissions. According to the previous works, heat flow through the building roofs in summer can be reduced by approximately 80% via green roofs. The green roofs are reported to consume less energy in the range of 2.2–16.7% than traditional roofs during summer time. A similar tendency is observed for the winter season depending on regional and climatic conditions. The temperature difference between conventional and greens roofs in winter is found to be about 4 °C, which is remarkable. Energy demand of buildings in summer is highly dependent on the plant intensity as it is reported to be 23.6, 12.3 and 8.2 kWh/m2/year for extensive, semi-intensive and intensive greenery surface, respectively. Greenery systems are also capable of providing thermally comfortable indoor and outdoor conditions. It is underlined that the annual average accumulation of CO2 reaches the level of 13.41–97.03 kg carbon/m2 for 98 m2 of vertical greenery system. The results of this research can be useful for dwellers, builders, architects, engineers and policy makers to have a good understanding about the potential of green roofs and facades to mitigate building-related energy consumptions and carbon emissions in a renewable, sustainable, energy-efficient and cost effective way.
AtıfScopus547WoS435OpenAlex617İncele - MakaleAçık Erişim2015Scopus SJRQ2The effect of magnetic field distribution and pole array on the vertical levitation force properties of HTS Maglev systems
Ozturk, Kemal; Abdioglu, Murat; Sahin, Ercin; Celik, Sukru; Gedikli, Hasan; Savaskan, Burcu
In this paper, the levitation force measurements have been carried out by the magnetic force measurement system under both field-cooling and zero-field-cooling regimes, whereas the magnetic field distribution over the permanent-magnet guideway (PMG) was calculated by numerical analysis based on the finite-element method. It was shown in this study that the vertical levitation capability and stability of Maglev systems can be improved depending on the cooling regime, pole number, and suitable arrangement of the PMG. In this paper, it was shown that when the pole number increases, the levitation force density increases. It also appeared that the reasonable position of the supplementary permanent magnet and appropriate cooling heights are key parameters for both levitation performance and stabilization of the high-temperature superconductor (HTS) Maglev. It is believed that the numerical and experimental data in this paper are useful for relative design and practical application of HTS Maglev systems.
AtıfScopus38WoS33OpenAlex36İncele - MakaleYalnız künye2015Scopus SJRQ3AlGaAs film growth using thermionic vacuum arc (TVA) and determination of its physical properties
Özen, Soner; Şenay, Volkan; Pat, Suat; Korkmaz, Şadan
In this research, an AlGaAs film was deposited on a microscope slide by means of the thermionic vacuum arc (TVA) technique which is a novel plasma production technique. AlGaAs structures were grown by this deposition technique for the first time and this process occurred in a very short period of time. In order to characterize the produced film, nano-structural, nano-mechanical, optical, and surface properties were determined by field emission scanning electron microscope (FESEM), atomic force microscope (AFM), X-ray diffractometer (XRD) and interferometer. According to the results of the measurements, the mean thickness value of the produced film was obtained as 1.8 μm. The band gap value was determined as 2eV from the Kubelka-Munk plot. The refractive index value was obtained as approximately 3.4. Hardness value was determined as 2 GPa from the Oliver-Pharr method. All these values are consistent with the reported values in the literature for the AlGaAs films produced by different methods. TVA technique appeared as a suitable and promising technique for the production of AlGaAs films.
AtıfScopus22WoS24OpenAlex24İncele - MakaleYalnız künye2015Scopus SJRQ1Reference-Plane-Invariant Effective Thickness and Electromagnetic Property Determination of Isotropic Metamaterials Involving Boundary Effects
Hasar, Ugur Cem; Barroso, Joaquim José; Buldu, Gul; Bute, Musa; Kaya, Yunus; Karacali, Tevhit; Ertugrul, Mehmet
It is well recognized that near-field effects become dominant when the metamaterial (MM) is in resonance. In addition, any inaccurate information of the location of reference planes, and the effective length can seriously affect the accuracy of retrieved electromagnetic properties of MMs. By considering all these issues, in this research paper, we propose a retrieval method for reference-plane invariant and thickness-independent determination of electromagnetic parameters of MM slabs involving boundary effects. Our method first accomplishes determination of effective length of MMs and calibration-plane factors using scattering parameter measurements, aside the resonance region, of two identical MMs with different lengths. Our method then incorporates near-field effects in accurate retrieval of electromagnetic properties of MMs. The method is verified by scattering parameters simulated for a homogeneous conventional material and a weakly or negligibly coupled inhomogeneous MM slab made by two metallic concentric split-ring-resonators. Consequences of an inaccurate information of reference-plane transformation factors and the value of effective lengths and of noninclusion of near field effects on the retrieved electromagnetic properties are thoroughly discussed by way of few examples to substantiate the accuracy of the proposed method.
AtıfScopus15WoS15OpenAlex15İncele - MakaleYalnız künye2014Scopus SJRQ4Antagonistic effects of Satureja hortensis essential oil against AFB, on human lymphocytes in vitro
Ceker, S.; Agar, G.; Alpsoy, L.; Nardemir, G.; Kizil, H.E.
Satureja hortensis L. (Lamiaceae) has been used as a folk remedy to treat various such as cramps, muscle pains, nausea, indigestion, diarrhea, and infectious diseases. In this study, the antagonistic effects of essential oil of S. hortensis (SHE) were studied against aflatoxin B1 (AFB1) in human lymphocytes in vitro. The analysis of the essential oil was performed by using Gas chromatography-mass spectrometry (GC-MS). Anti-genotoxic effects of the SHEs was evaluated using sister chromatid exchange (SCE), micronuclei (MN) tests against AFB1. Also level of malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities used to determine the anti-oxidative effects of the SHEs. This result showed AFB1 (5 μM) increased the frequencies of SCE, MN and the level of MDA. AFB1 at the same concentration decreased the activities of SOD and GPx. However, different concentrations of SHE with AFB1 decreased the frequency of SCE and MN and level of MDA and also increased the activities of SOD and GPx significantly. Especially, the 1.0, 1.5, 2.0 μL dose of SHE are more effective than other doses. The results of this experiment have clearly shown that SHE has strong antioxidative and antigenotoxic effects, these biological activities of SHEs can be due to its component.
AtıfScopus6WoS6OpenAlex10İncele - MakaleAçık Erişim2015Scopus SJRQ2Determination of the critical fraction of solid during the solidification of a PM-cast aluminium alloy
Kayikci, Ramazan; Colak, Murat; Sirin, Selcuk; Kocaman, Engin; Akar, Neset
During the solidification of aluminium alloys, a flow of the interdendritic liquid through the mushy zone plays an important role in the feedability and shrinkage-driven porosity formation. Therefore, for almost all the studies about casting modelling, a good knowledge of the mushy-zone behaviour is necessary. In this study, the limit of the mushy-zone permeability for permanent-mould (PM)-cast aluminium alloys was investigated. A novel experimental technique was developed to quantify the value of the critical fraction of solid (CFS) at which the interdendritic feeding stops. Grain-refined and non-grain-refined aluminium alloys were used to evaluate the effect of the grain size on the CFS limit of both the non-grain-refined and fully grain-refined alloys. Three different initial mould temperatures were used to find if the mould temperature has any effect on the feeding of a casting. Alloys of varying solidification intervals were also used to determine the critical fraction of solid (CFS) for the feeding limit of solidifying castings. The results showed that the CFS values for solidifying aluminium alloys may vary from 34 % to 57 % depending on the casting conditions. The results also showed that for A356 aluminium-alloy castings the CFS value is not an alloy property, yet it significantly depends on the parameters such as the grain refinement and the modification of eutectic silicon.
AtıfScopus9WoS5OpenAlex9İncele - MakaleAçık Erişim2016Scopus SJRQ2Optical, morphological and mechanical properties of an Al-Al2O3 nanocomposite thin film grown by thermionic vacuum arc
Şenay, Volkan; Özen, Soner; Pat, Suat; Korkmaz, Şadan
An Al-Al2O3 nanocomposite thin film was deposited onto a glass substrate in high vacuum condition using Al2O3 pellets as source material by means of the thermionic vacuum arc technique in just 50 s. UV-visible spectrophotometer, optical reflectometer, spectroscopic ellipsometer, XRD, FESEM and AFM were employed to investigate the optical, structural morphological and mechanical properties of the produced film. The film exhibited a high transmittance (above 80%) in the 400-1000 nm region. The dispersion of the refractive index was discussed in terms of the single oscillator model. The optical band gap value derived from the Wemple-DiDomenico dispersion relationship was 5.7 eV. It was observed that the results of the optical investigations agreed well with Al2O3 thin films. XRD characterization showed that the film contained Al and Al2O3 phases. The FESEM analysis revealed that the film morphology had a dense characteristic. 2D and 3D AFM micrographs indicated a smooth surface with a low value of average roughness. When compared to the mechanical properties of Al2O3 thin films, it was observed that the hardness and Young's modulus reduced due to presence of ductile Al particles.
AtıfScopus9WoS8OpenAlex11İncele - MakaleAçık Erişim2019Scopus SJRQ3Effects of varying essential oil mixture concentrations applied underconditions of different temperature stress on cardiac markers and other blood parameters
Bayraktar, Bülent; Tekce, E.
Cardiac troponin (cTnI) and erythrocyte distribution width (RDW) have been used as specific markers for the evaluation of cardiac arrhythmias and myocardial diseases. In this experimental study, we aimed to determine the dose-dependent administration of an Essential OilMixture (EOM) (Eucalyptus globulusLabill, Thymus vulgaris, Cymbopogon nardus, and Syzygiumaromaticum) on the serum erythrocyte indices and myocardial damage. We used 400 male, oneday-old, Ross-308 chicks. Each group ((n=8) (22°C Control (C), C+250 mL/1,000 L, C+500 mL/1,000 L, C+750 mL/1,000 L), 36°C (stress control (SC), SC+250 mL/1,000 L, SC+500 mL/1,000 L, SC+750 mL/1,000 L) was further divided into eight groups with 50 animals. Each group of 50 chicks was further subdivided into five groups with 10 animals in each compartment. The results showed that the WBC, RBC, HGB, HCT, RDWSD, RDW-CV, and Lymphocyte decreased in groups without exposure to temperature stress (22ºC) compared to the 22ºC control group; whereas, CnTnI, MCHC, NEUT, and IG (p<0.05) increased compared to the control group. In groups exposed to temperature stress (36ºC), the WBC, HGB, HCT, RDW-SD, and Lymphocyte decreased compared to the control group, but MCH, MCHC, NEUT, and IG increased compared to the control. However, cTnI, CK, creatinine, RBC, and RDW had no effect on CD, MONO, EO, and BASO (p<0.05). EOM mixture had no effect on hematological and biochemical parameters.
AtıfScopus9WoS9OpenAlex9İncele - MakaleAçık Erişim2016Scopus SJRQ1Development of a fermented ice-cream as influenced by in situ exopolysaccharide production: Rheological, molecular, microstructural and sensory characterization
Dertli, Enes; Toker, Omer S.; Durak, M. Zeki; Yilmaz, Mustafa T.; Tatlisu, Nevruz Berna; Sagdic, Osman; Cankurt, Hasan
This study aimed to investigate the role of in situ exopolysaccharide (EPS) production by EPS+ Streptococcus thermophilus strains on physicochemical, rheological, molecular, microstructural and sensory properties of ice cream in order to develop a fermented and consequently functional ice-cream in which no stabilizers would be required in ice-cream production. For this purpose, the effect of EPS producing strains (control, strain 1, strain 2 and mixture) and fermentation conditions (fermentation temperature; 32, 37 and 42°C and time; 2, 3 and 4 h) on pH, S. thermophilus count, EPS amount, consistency coefficient (K), and apparent viscosity (η50) were investigated and optimized using single and multiple response optimization tools of response surface methodology. Optimization analyses indicated that functional ice-cream should be fermented with strain 1 or strain mixture at 40-42°C for 4 h in order to produce the most viscous ice-cream with maximum EPS content. Optimization analysis results also revealed that strain specific conditions appeared to be more effective factor on in situ EPS production amount, K and η50 parameters than did fermentation temperature and time. The rheological analysis of the ice-cream produced by EPS+ strains revealed its high viscous and pseudoplastic non-Newtonian fluid behavior, which demonstrates potential of S. thermophilus EPS as thickening and gelling agent in dairy industry. FTIR analysis proved that the EPS in ice-cream corresponded to a typical EPS, as revealed by the presence of carboxyl, hydroxyl and amide groups with additional α-glycosidic linkages. SEM studies demonstrated that it had a web-like compact microstructure with pores in ice-cream, revealing its application possibility in dairy products to improve their rheological properties.
AtıfScopus86WoS74OpenAlex98İncele - MakaleYalnız künye2013Scopus SJRQ1An experimental exergetic comparison of four different heat pump systems working at same conditions: As air to air, air to water, water to water and water to air
Çakir, Uǧur; Çomakli, Kemal; Çomakli, Ömer; Karsli, Süleyman
In this study, we designed a multifunctional heat pump system using just one scroll compressor and which can be run in four different modes, namely air to air, air to water, water to water and water to air, in order to make an experimental energetic and exergetic performance comparison. Experimental system consists of two condensers and two evaporators and uses R22 as working fluid. One of the evaporators and condensers uses water and the others use air as heat source/sink. Heating capacities of four heat pump types are equal to each other. It is realized by adjusting the mass flow rate and temperature level of external fluid of condenser. Results show that the heat pump unit which has the maximum COP (coefficient of performance) value is water to air type with 3.94 and followed by water to water type with 3.73, air to air type with 3.54 and air to water type with 3.40. Ranking of four heat pump types with respect to their mean exergy efficiency is as follows; water to air type with 30.23%, air to air type with 30.22%, air to water type with 24.77% and water to water type with 24.01%. Exergy destruction rates of the systems were investigated in this study and the results revealed that the heat pump type which has the maximum exergy destruction is air to air type with 2.93kW. The second highest one is air to water type with 2.84kW. The third highest one is water to air type with 2.64kW and last one is water to water type with 2.55kW. It is understood that the temperature of the evaporator external fluid affects the exergetic efficiency of the system more than the mass flow rate. In contrast to the previous, the dominant parameter which has more important effect on the exergy destruction of the heat pump unit is the mass flow rate of evaporator external fluid.
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