Enhancement of Heat Transfer Performance of a Heat Pipe by Using Calcium Magnesium Carbonate-Ethylene Glycol/Water Nanofluid with Sodium Dodecylbenzene Sulfonate

In this paper, the effect of using CaMg(CO3)2/Ethylene Glycol-water (50:50%) as a working fluid on the thermal performance of thermosyphon heat pipe was experimentally studied. Nanofluid was prepared by two-step method using 2% concentration of CaMg(CO3)2 nanoparticle and 0.05% surfactant (Sodium dodecylbenzene sulfonate). For the experimental set-up, a straight copper pipe of one-meter length was used. The inner diameter of the pipe is 13 mm, and the outer diameter is 15 mm. Experiments were conducted at three different cooling water mass flow rates (5, 7.5, and 10 g/s) and different heating powers (200, 300, 400 W) to test heat pipe performance. It was observed that the CaMg(CO3)2 nanofluid reduced the average wall temperature of the heat pipe according to the base fluid. Furthermore, the efficiency and thermal resistance of the heat pipe were investigated separately for EG/water and CaMg(CO3)2 nanofluid. The maximum heat transfer enhancement was obtained as 9.55% under 400 W heating power and 10 g/s cooling water mass flow rate conditions and the maximum improvement in thermal resistance was observed as 21% at 200 W and 10 g/s cooling mass flow rate. Viscosity and specific heat of base fluid and CaMg(CO3)2 nanofluid were also determined and compared to each other

Uçucu Külün Yapı Malzemelerinin Mukavemeti ve Bağlayıcılığına Etkisinin Araştırılması

Dünyada yaşanılan iklim değişikli nedeniyle enerji temini gibi hafif yapı malzemelerinin kullanımına yönelik araştırmalar son yıllarda hız kazanmıştır. Tasarım uygulamalarının birçoğu iklimi de dolaylı olarak etkileyecek nitelikte olduğundan yapılan araştırmalar, fosil yakıtlara bağlı olmaksızın, düşük karbonlu bir geleceği teşvik etmeye yardımcı olacaktır. Yapı malzemelerinde aranan özellikler; ekonomiklik, dayanım, insan sağlığına ve çevreye olumsuz etkisinin bulunmamasıdır. Türkiye’de kömür yakıtlı termik santrallerde 2017 yılında 63 milyon ton linyit elektrik üretimi amacıyla tüketilmiştir. Yakılan kömürlerden elde edilen uçucu küller, depolama alanlarında depolanmakta rüzgar, yer altı ve yer üstü suyu ile taşınarak çevre ve insan sağlığını olumsuz yönde etkilemektedir. Bu çalışmada, puzolan özellik gösteren, kireç oranı yüksek ve atık malzeme nitelendiğinde Yatağan Termik Santrali uçucu külü kullanılmıştır. Standart bağlayıcı malzemeler olarak bilinen çimento, kireç ve alçı yerine kullanılabileceği düşünülen uçucu külün bağlayıcı özelliği ve malzemenin mukavemeti üzerine araştırma yapılmıştır. Deneysel çalışmalarda üretilen 4x4x16 cm ebatlarındaki numunelere basınç ve eğilme deneyleri uygulanarak mekanik dayanımları belirlenmiştir. Deneyler sonucunda 4.4 nolu numunede en yüksek eğilme dayanımı 2,39 MPa, 3.1 nolu numunede en yüksek basınç dayanımı 10,03 MPa olarak bulunmuştur. Yapılan çalışmalar sonucunda puzolan özelliğe sahip uçucu küllerin bağlayıcı etkisi görülmüş ve dolgu malzemesi olarak mekanik dayanımda artış sağladığı tespit edilmiştir

Extraction of phytosterols from melon (Cucumis melo) seeds by supercritical CO2 as a clean technology

Extraction with supercritical carbon dioxide (SC-CO2) which is known as a clean technology was carried out to extract oil from melon (Cucumis melo) seeds. SC-CO2 extraction technique does not contaminate extracts. SC-CO2 is not a toxic and a flammable solvent. Phytosterols, natural and bioactive compounds, which is known to provide protection against various chronic diseases were examined in the seed oil by using gas chromatography – mass spectrometry (GC-MS). Stigmasterol and β-sitosterol were detected in the melon seed oil. SC-CO2 extractions were performed in a range of 30-55°C, 150-240 bar, 7-15 g CO2/min, 0.4-1.7 mm (mean particle size of the seeds) and 1-4 h. The optimal quantities of extracted oil, β-sitosterol and stigmasterol were 36.8 g/100 g seed, 304 mg/ kg seed and 121 mg/ kg seed, respectively, at 33°C, 200 bar, 11 g CO2/min, 0.4 mm and 3 h

Thermal Performance Improvement of the Heat Pipe by Employing Dolomite/Ethylene Glycol Nanofluid

In heat transfer applications, heat pipes are widely- preferred because of some characteristics such as low cost, being able to be produced in any size and low maintenance cost make them superior. Moreover, the working fluid to be employed substantially affects the heat transfer characteristics of a heat pipe. In this paper, effects of nanoparticle addition into the ethylene glycol on heat pipe’s thermal performance were analysed experimentally. Every test was done using two variant working fluids, ethylene glycol and dolomite nanoparticles-doped ethylene glycol, respectively. Dolomite nanoparticles (2% by weight) and Sodium Dodecyl Benzene Sulfonate (0.5% by weight) were doped into the ethylene glycol while preparing the dolomite/ethylene glycol nanofluid. After filling in the heat pipe, experiments were realized under changing working conditions. Using experimental data, efficiency and thermal resistance of the heat pipe were examined. Viscosity of the each working fluid was determined. The contact angle –wettability measurements were also performed to specify the effects of surface active agent addition. The obtained findings revealed that nanoparticle inclusion inside the base fluid, i.e. ethylene glycol, improved the thermal performance (efficiency) and decreased the heat pipe’s thermal resistance substantially. ©2020. CBIORE-IJRED. All rights reserve

Effects of Boron Phosphate Additive on Ceramics with Anorthite Phase

In this study, the anorthite phase was chosen as a ceramic type that can withstand thermal shock. First, boron phosphate was synthesised, boron phosphate was calcined at 1000°C and characterized by XRD and chemical analyzes. On the other hand, in the phase diagram, the most suitable eutectic points covering the anorthite phase (CaO, Al2O3 , SiO2) and at the lowest temperature at which anorthite can form are selected. 6 mixtures were prepared using wollastonite, kaolinite and calcite. The 6 mixtures prepared were separated into two equal parts and the second parts were added of BPO4 10%. The mixtures were pressed at the same pressure and cooked under the same conditions and at the same heating rate in the electric oven at 1050, 1100, 1150 and 1200°C. DTA and TGA analyzes were applied to the samples before sintering, and XRD analyzes were applied to the sintered samples. According to the test results, the addition of the synthesized BPO4 has shown that the anorthite phases are formed at temperatures well below the theoretical formation temperatures without swelling

Experimental investigation of nanolubricant usage in a cooling system at different nanoparticle concentrations

WOS:000551847100005Nanoparticles-containing working fluid utilization in thermal systems has been increasing day after day because of their capabilities of enhancing thermophysical properties of the base fluid. In this experimental study, influences of nanoparticle utilization inside the polyol ester compressor oil in a cooling system as a nanolubricant were investigated. Titanium dioxide nanoparticles were added to the polyol ester compressor oil, together with 350 g of an R134a refrigerant. A surface active agent was also used in order to prevent agglomerations of doped nanoparticles during operation of the system. Experiments were conducted at different nanoparticle concentrations (1.0 wt.%, 1.5 wt.%, and 2.0 wt.%) to show the effects of nanoparticle concentration on performance of the cooling system. Cooling coefficient of performance and power consumption of the compressor were analyzed. As a consequence of the experiments, the best results were obtained in the cases in which nanoparticle concentration of 1.0% nanolubricant was used. The cooling coefficient of performance of the system was increased up to 4.70, and the power consumption of the compressor was decreased to 26.28 kJ.h(-1).This study is part of PhD thesis of Mustafa Akkaya and the authors received support for nanoparticle analysis from the Scientific and Technological Researches Application and Research Center (Kmu-Biltem-Karaman/Turkey)