The contact angle of nanofluids as thermophysical property

Droplet volume and temperature affect contact angle significantly. Phase change heat transfer processes of nanofluids – suspensions containing nanometre-sized particles – can only be modelled properly by understanding these effects. The approach proposed here considers the limiting contact angle of a droplet asymptotically approaching zero-volume as a thermophysical property to characterise nanofluids positioned on a certain substrate under a certain atmosphere. Graphene oxide, alumina, and gold nanoparticles are suspended in deionised water. Within the framework of a round robin test carried out by nine independent European institutes the contact angle of these suspensions on a stainless steel solid substrate is measured with high accuracy. No dependence of nanofluids contact angle of sessile droplets on the measurement device is found. However, the measurements reveal clear differences of the contact angle of nanofluids compared to the pure base fluid. Physically founded correlations of the contact angle in dependency of droplet temperature and volume are obtained from the data. Extrapolating these functions to zero droplet volume delivers the searched limiting contact angle depending only on the temperature. It is for the first time, that this specific parameter, is understood as a characteristic material property of nanofluid droplets placed on a certain substrate under a certain atmosphere. Together with the surface tension it provides the foundation of proper modelling phase change heat transfer processes of nanofluids

Özel yapım optik cımbız ile maya hücresi manipülasyonu

The goal of this study is developing custom designed optical tweezer which uses two He-Ne lasers (λ=632.8 nm) parallel to each other to trap yeast cells. The characteristic specs of this optical tweezer determined by Brownian Motion of polystyrene beads in water. Stiffness and trapping forces of optical tweezer calculated for laser 1, laser 2 and when both lasers used simultaneously. Laser 2 can trap and move particle to laser 1 and multiple particles can be trapped by the laser 1. After determination of specs of optical tweezer, yeast cells in yogurt culture medium were trapped by laser 1 and laser 2. Stiffness of optical tweezer and trapping force on yeast cells were determined by drag force and Brownian motion methods by assuming the medium was homogenous and had viscosity of 0.038 kg/ms. Viscosity depends on the concentration of fluid and surface. Viscosity of the yogurt culture medium which was used in experiments was calculated theoretically with respect to velocity of fluid and specs of optical tweezer calculated previously. Possibility of application inside yeast cells was studied theoretically by using viscosity of cytoplasmic medium. As a result of this study, this custom designed optical tweezer which uses two He-Ne lasers are applicable in life sciences like inside cells, viscosity measurements and drug delivery systems

Geometrical Optimization of Dimpled Double-Pipe Heat Exchangers for Nanofluid-based Natural Circulation Loops Operating at Lower Temperatures

Excessive use of global energy sources causes negative environmental impacts and a reduction in the available energy resources. Therefore, energy efficiency is the main scope of engineering studies. Since household refrigeration accounts for a large portion of the energy consumption rate in buildings, several innovative techniques have been developed to improve the energy efficiency of vapor compression refrigeration systems. Suction line heat exchangers are considered one of these techniques and they are used to avoid the presence of liquid at the compressor and to prevent sweating on the suction line, as well as increasing enthalpy difference together with superheating the refrigerant at the compressor inlet. Here, a single-phase natural circulation mini loop (SPNCmL) with double pipe heat exchangers (DPHX) at cooling and heating-ends, has been proposed as an alternative to suction line heat exchangers which requires more attention to control the heat exchange process. Locating DPHXs at the low-pressure side and high-pressure sides of a conventional refrigeration cycle forms a thermal bridge with connecting these by vertical legs of the SPNCmL and provides precise control of the heat transfer with a flexible design

Azerbaycan Gence Kazak Bölgesi Ballarının Mikroskobik, HPLC ve GC-MS Analizleri ile İçeriklerinin Belirlenmesi

In this study, it was aimed to evaluate the quality and botanical sources of Azerbaijan Ganja Gazakh Region’s honeys by melitopalynological, physicochemical and organoleptic analyzes. For this purpose, 23 honey samples were collected from 8 different administrative regions (rayon) of Azerbaijan Ganja Gazakh Economic Region during the honey harvest period in 2014. The pollen contents, total number of pollen (TPN-10) and starch content of 10 g honey were examined by melitopalynological analyses. As a result of the analysis, 34 different plant families, 42 plant genera and 4 species were determined and it was determined that 7 honey were monofloral and 16 honey were multifloral. iv The mean values of the amount of ash is 0,13 ± 0,1 g / 100 gr, the electrical conductivity is 0,37 ± 0,18 mS / cm, the humidity is 16 ± 1,01%, the pH is 3,50 ± 0,22, the free acidity is 18,68 ± 5, 41 meq / kg and total acidity is 31,74 ± 11,44 meq / kg. The sugar content of honeys was determined by high performance liquid chromatography (HPLC) with an average glucose of 33,26 ± 4,43 g / 100 g and an average fructose of 40,24 ± 2,85 g / 100 g. The mean sucrose was 1.35 ± 0, 98 g / 100 g. Aluminum (Al), Arsenic (As), Cadmium (Cd), Copper (Cu), Iron (Fe), Magnesium (Mg), Manganese (Mn), Nickel (Ni), Vanadium (V) element analyzes of honey samples were performed by inductively coupled plasma optical emission spectrometry (ICP-OES). The average values of the minerals are Al 2.49 - As 4,38.- Cd 0,23 - Cu 0,32 - -Fe 3,84 - Mg 21,95.- Mn 0,35 - Ni 7,46 - V 0,57 - Zn 6,56 mg / kg. The total phenolic mean value of honey is 578, 20 GAE / kg and the color index ranges from 0.09 to 0.34 mAU. Residue analyzes were performed by liquid chromatography-mass spectrometry (LC-MS) and antibiotic residues such as chloramphenicol, ciprofloxine, difloxacin, doxycycline, oxytetracycline, sulfadiazine, sulfamethazine, sulfatiazole and tetracycline were found in ppb and ppm levels. Methanol ethanol extraction and solid phase microextraction methods were used to determine volatile content of the honeys. Two separate readings were taken with methanol ethanol extrection method at intervals of 6 months. Sensory analyzes of honey samples were made with organoleptic analyzes and 17% of the samples were evaluated as good quality. It was determined that 30% of the honeys were monofloral, 70% were multifloral and 87% of them were appropriate to the current quality criteria. As, Cd, V elements were detected in honey samples and antibiotic residues were found in 87% of the honey samples. As a result of the analyzes performed with GC-MS at 6-month intervals, the decrease in the amount of the substance was determined as 14%. At the same time, methanol ethanol extraction with solid phase microextraction (SPME) was compared with. 18.8% more substances in methanol ethanol extraction than SPME.ÖZET i ABSTRACT iii TEŞEKKÜR v İÇİNDEKİLER DİZİNİ vi ÇİZELGELER DİZİNİ xxii ŞEKİLLER DİZİNİ xxv SİMGELER VE KISALTMALAR DİZİNİ xxviii 1. GİRİŞ 1 2. GENEL BİLGİLER 5 2.1. Balın Tarihçesi 5 2.2. Balın Tanımı 5 2.3. Balın Bitkisel Kökeni ve Üretim 6 2.3.1. Nektar Balı 6 2.3.1.1. Monofloral Bal 7 2.3.1.2. Multifloral Bal 7 2.3.2. Salgı Balı 7 2.3.3. Bal Üretimi 7 2.4. Balın Fiziksel Karakteristikleri 8 2.4.1. Viskozite 8 2.4.2. Hidroskopi 9 2.4.3. Yüzey Gerilimi 9 2.4.4. Renk 10 2.4.5. Kristalizasyon 11 2.4.6. Fermentasyon 11 2.4.7. Tat ve Aroma 12 2.4.8. Elektriksel İletkenlik 13 2.5. Balın Kimyasal İçeriği 13 2.5.1. Karbohidratlar 13 2.5.2. Proteinler 14 2.5.3. Nem 15 2.5.4. Mineraller 16 2.5.5. Organik asitler 16 2.5.6. Vitaminler 17 2.5.7. Fenolik Bileşenler 17 2.5.8. Uçucu Bileşenler 19 2.6. Balda Yer Alan Bileşenlerin Stabilitesi 20 2.7. Balın Kalitesini Belirleyen Parametreler 21 2.7.1. Melitopalinolojik Analizler 25 2.7.2. Kimyasal Analizler 27 2.7.2.1. Şekerler 27 2.7.2.2. Nem 28 2.7.2.3. Serbest Asitlik, pH, Toplam Asitlik 29 2.7.2.4. Kül ve Elektriksel İletkenlik 29 2.7.2.5. Renk 30 2.7.2.6. 5- Hidroksimetil furfural (5-HMF) 31 2.7.2.7. Pestisit Analizi 31 2.7.2.8. Element Analizi 34 2.7.2.9. Kimyasal İçerikTayini 34 2.7.3. Duyusal Analizler 35 2.8. Balın Biyolojik Aktiviteleri ve Kullanım Alanları 36 2.9. Araştırma Alanının Tanımlanması 36 2.10. Azerbaycan Gence Kazak Ekonomik Bölgesi’nin İklimi ve Bitki Örtüsü 38 2.11. Azerbaycan’ın Genel Tarımsal Yapısı 40 2.12. Azerbaycan Arıcılığının Durumu 41 3. MATERYAL VE YÖNTEMLER 44 3.1. Arazi Çalışması 44 3.1.1. Bitkilerin Toplanması 44 3.1.2. Bal Örneklerinin Toplanması ve Saklanması 45 3. 2. Balın Mikroskobik Analizi 48 3.2.1.Toplam Polen Sayısı (TPS) Analizi 48 3.2.1.1. Preperatların Hazırlanması 48 3.2.1.2. Preparatların İncelenmesi 49 3.2.2. Balın polen analizi 49 3.2.2.1. Preparatların hazırlanması 49 3.2.2.2. Referans polen preparatlarının hazırlanması 50 3.2.2.3. Bazik fuksinli gliserin-jelatin hazırlanması 50 3.2.2.4. Preparatların incelenmesi 50 3.2.3. Balda Nişasta Analizi 51 3.2.3.1. Preparat Hazırlanması 51 3.2.3.2. Nişasta Analizi İçin İyot Çözeltisi Hazırlanması 51 3.2.3.3. Preparat İncelenmesi 51 3.3. Balın Fizikokimyasal Analizleri 51 3.3.1. Balda Kül Miktarı ve Elektriksel İletkenlik Tayini 51 3.3.1.1.Örnek Hazırlanması 52 3.3.1.2. Kül Miktarı 52 3.3.1.3. Elektriksel İletkenlik 52 3.3.2. Balda Refraktometre ile Nem Tayini 52 3.3.3. Balda pH, Serbest Asitlik, Toplam Asitlik ve Lakton Asitliği Tayini 52 3.3.3.1.Örnek Hazırlanması 52 3.3.3.2. pH 53 3.3.3.3. Serbest Asitlik 53 3.3.3.4. Lakton Asitliği 54 3.3.3.5. Toplam Asitlik 54 3.3.4. Bal Örneklerinde Yüksek Performanslı Sıvı Kromatografi (HPLC) Cihazı ile Şeker Analizi 54 3.3.5. Bal Örneklerinde Hidroksimetilfurfural (HMF) Analizi 55 3.3.6. Balda Element Analizi 56 3.3.8. Bal Örneklerinin Renk Yoğunluğunun Belirlenmesi 58 3.3.9.Balda LC-MS/MS Cihazı ile Antibiyotik Kalıntı Analizi 59 3.3.10. Balda Etanol Metanol Ekstraksiyon Yöntemi Kullanılarak Gaz Kromatografisi-Kütle Spektrometresi (GC-MS) ile Uçucu Bileşen Tayini 59 3.3.11. Balda Katı Faz Mikroekstraksiyon (SPME) Yöntemi Kullanılarak Gaz Kromatografi-Kütle Spektrometresi ile Uçucu Madde Tayini 60 3.4. Organoleptik Analiz 61 3.5. İstatistiksel Analizler 61 4.BULGULAR 62 4.1. Melitopalinolojik Analiz Sonuçları 62 4.1.1. Toplam Polen Sayısı (TPS 10) Analizi 62 4.1.2. Balda Polen Analizi 64 4.1.2.1. Bitki Örnekleri 98 4.1.3. Balda Nişasta Analizi 98 4.2. Fizikokimyasal Analiz Sonuçları 101 4.2.1. Balda Kül ve Elektriksel İletkenlik Miktarı Tayini 102 4.2.3. Balda pH, Serbest Asitlik, Toplam Asitlik ve Lakton Asitliği Tayini 107 4.2.4. Bal Örneklerinde Yüksek Performanslı Sıvı Kromatografi (HPLC) Cihazı ile Şeker Analizi 111 4.2.5. Bal Örneklerinde Hidroksimetilfurfural (HMF) Analizi 118 4.2.6. Balda Element Analizi 120 4.2.7. Balda Toplam Fenolik Asitlik Analizi 127 4.2.8. Bal örneklerinin renk yoğunluğunun belirlenmesi 129 4.2.9. Balda LC-MS MS Cihazı ile Antibiyotik Kalıntı Saptanması 131 4.2.10. Balda Etanol Metanol Ekstraksiyon Yöntemi Kullanılarak Gaz Kromatografisi-Kütle Spektrometresi (GC-MS) ile Uçucu Bileşen Tayini 134 4. 2.11. Balda Katı Faz Mikroekstraksiyon (SPME) Yöntemi Kullanılarak Gaz Kromatografi-Kütle Spektrometresi ile Uçucu Madde Tayini 146 4.2.12. Fizikokimyasal Sonuçların İdari Bölge, Yüksekliklere Göre Kıyaslanması ve Kalite Kriterlerine Uygunluğu 153 4.3. Organoleptik Analiz Sonuçları 155 5. TARTIŞMA 157 KAYNAKLAR 187 ÖZGEÇMİŞ 206Bu çalışma ile Azerbaycan Gence Kazak Ekonomik Bölgesi ballarının melitopalinolojik, fizikokimyasal ve organoleptik analizleri ile kalitesinin ve botanik kaynağının değerlendirilmesi hedeflenmiştir. Bu amaç doğrultusunda, 23 adet bal örneği 2014 yılı, bal hasadı döneminde Azerbaycan Gence Kazak Ekonomik Bölgesi’nin 8 farklı idari bölgesinden (Rayon) toplanmıştır. Melitopalinolojik analizler ile balların polen içerikleri, 10 gr baldaki toplam polen sayısı (TPS-10) ve nişasta içerikleri incelenmiştir. Analiz sonucunda 34 farklı bitki familyası, 42 adet bitki cinsi ve 4 tür belirlenmiş ve 7 balın monofloral, 16 balın multifloral olduğu tespit edilmiştir. Kül miktarı ortalama 0,13 ± 0,1 g/100 gr, elektriksel iletkenlik 0,37 ± 0,18 mS/cm, nem 16 ± 1,01 %, pH 3,50 ± 0,22, serbest asitlik 18,68 ± 5,41 meq/kg ve toplam ii asitlik 31,74 ± 11,44 meq/kg olarak saptanmıştır. Balların şeker içeriği yüksek performanslı sıvı kromatografisi (HPLC) ile belirlenmiş olup, ortalama glukoz içeriği 33,26 ± 4,43 g/100 g, fruktoz içeriği 40,24 ± 2,85 g/100 g’dır. Sukroz miktarının ise ortalama 1,35 ± 0,98 g/100 g olduğu görülmüştür. Balların alüminyum (Al), arsenik (As), kadmiyum (Cd), bakır (Cu), demir(Fe), magnezyum (Mg), mangan (Mn), nikel (Ni), vanadiyum (V), çinko (Zn) element analizleri indüktif eşleşmiş plazma optik emisyon spektrometrisi (ICP-OES) ile yapılmış olup elementlerin ortalama değerleri, Al 2,49 - As 4,3 - Cd 0,23 - Cu 0,32 - Fe 3,84 - Mg 21,95 - Mn 0,35 - Ni 7,46 - V 0,57 - Zn 6,56 mg/kg bulunmuştur. Balların toplam fenolik asitlik analizleri spektrofotometrik yöntem kullanılarak yapılmış, toplam fenol değeri ortalama 578,20 ± 170 GAE/kg olup, renk indeksi 0,09 ile 0,34 mAU arasında değişmektedir. Balların kalıntı analizleri sıvı kromatografisi – kütle spektrometresi (LC-MS) ile yapılmış, kloramfenikol, siprofloksin, difloksasin, doksisiklin, oksitetrasiklin, sülfadiazin, sülfametazin, sülfatiazol, tetrasiklin grubu antibiyotik kalıntıları belirlenmiştir. Balların uçucu bileşen içeriğinin tespitinde metanol etanol ekstraksiyon ve katı faz mikro ekstraksiyon yöntemi kullanılmış olup, metanol etanol yöntemi ile 6 ay aralıklarla iki ayrı okuma alınmıştır. Organoleptik analizler ile bal örneklerinin duyusal analizleri yapılmış, balların %17’si kaliteli olarak değerlendirilmiştir. Yapılan analizler sonucunda, balların % 30’ unun monofloral, %70’ nin ise multifloral olduğu, %87’ sinin kalite kriterlerine uygun olduğu saptanmıştır. Ballarda As, Cd, V elementleri tespit edilmiş ve balların %87’ sinde antibiyotik kalıntısına rastlanılmıştır. GC-MS cihazı ile 6 aylık aralıklarla yapılan analizler sonucunda, madde miktarındaki azalma %14 olarak tespit edilmiştir. Aynı zamanda, katı faz mikro ekstraksiyonu (SPME) ile metanol etanol ekstraksiyonu kıyaslanmış olup, metanol etanol ekstraksiyonunda %18,8 daha fazla madde saptanmıştır

Effect of Nanofluid Thermophysical Properties on the Performance Prediction of Single-Phase Natural Circulation Loops

Specifying nanofluids’ thermophysical properties correctly is crucial for correct interpretation of a system’s thermo-hydraulic performance and faster market-uptake of nanofluids. Although, experimental and theoretical studies have been conducted on nanofluids’ thermophysical properties; their order-of-magnitude change is still a matter of debate. This numerical study aims to reveal the sensitivity of single phase natural circulation loops (SPNCL), which are the passive systems widely used in solar thermal and nuclear applications, to thermophysical property inputs by evaluating the effects of measured and predicted nanofluid thermophysical properties on the SPNCL characteristics and performance for the first time. Performance and characteristics of an SPNCL working with water-based-Al2O3 nanofluid (1–3 vol.%) for heating applications is evaluated for different pipe diameters (3–6 mm). The thermal conductivity effect on SPNCL characteristics is found to be limited. However, viscosity affects the SPNCL characteristics significantly for the investigated cases. In this study, Grm ranges are 1.93 × 107–9.45 × 108 for measured thermophysical properties and 1.93 × 107–9.45 × 108 for predicted thermophysical properties. Thermo-hydraulic performance is evaluated by dimensionless heat transfer coefficients which is predicted within an error band of ±7% for both the predicted and measured thermophysical properties of the data. A Nu correlation is introduced for the investigated SPNCL model, which is useful for implementing the SPNCL into a thermal system

Carbon-based Nanofluid Applications in Solar Thermal Energy

Renewable energy sources such as solar, wind and geothermal are proposed as an alternative to fossil fuels whose excessive use causes global warming. The most popular one of the renewable energy sources is considered as solar energy due to the fact that required energy is provided by the sun entire year around the world. Solar energy systems convert the solar radiation to the useful heat or electricity. In order to achieve better performance in solar thermal systems many studies have been conducted. Some of these studies suggest that heat transfer fluid could be changed with the nanofluids which can be defined as new generation heat transfer fluid. Nanofluids are suspensions of nano-sized particles such as metals, metal-oxides, and Carbon-allotropes (C), in the conventional base-fluids (water, ethylene glycol and oil). Using nanofluid enhances the efficiency and thermal performance of solar systems due to their better thermophysical and optical properties. Recently, C-based nanofluids are getting attention due to their enhanced thermal conductivity and absorptivity at even low concentrations. The results show that C-based nanofluids have a potential to use in solar energy systems: solar collectors, solar stills, photovoltaic/thermal systems

The developing flow characteristics of water - ethylene glycol mixture based Fe3O4 nanofluids in eccentric annular ducts in low temperature applications

International audienc

The Developing Natural Convection Visualization of Water - Ethylene Glycol Mixture based Fe3O4 Nanofluids in Eccentric Annular Ducts in Low Temperature Applications

International audienc