The thermophysical properties of nanofluids must be determined to evaluate
their thermal performances like heat transfer, convection heat transfer
coefficient, Nusselt number. The purpose of this study is to obtain the
thermophysical properties of nanofluids. Al2O3, TiO2, and ZnO are used as a
nanoparticle, while deionized water is used as base fluid. The solutions
included nanoparticles in a way to be each with 0.5%, 0.7%, and 1.0%
volumetric concentration were prepared. SDS was added to the solutions as a
surfactant to prevent instability that occurred due to agglomeration and
sedimentation. For thermal conductivity measurement, the device that works
by the transient hot-wire method was used between 30-60?C temperatures.
Also, for viscosity measurement, the device that works as based on the
vibrating plate method was used between 20-50?C temperatures. Density and
specific heat values are obtained with the help of the well-known equations
while thermal conductivity and viscosity are measured. Thanks to this study,
it is emphasized how thermophysical properties of nanofluids change
according to temperature and volumetric concentration. Moreover, their curve
fitting equations are obtained. All of the thermophysical properties
compared with the studies in the literature. It is established that the
thermal conductivity of nanofluids is proportional to temperature, and
viscosity of it is proportional to volumetric concentrations but inversely
with temperature. Finally, the effects of the augmentation in dynamic
viscosity on pumping power were considered as well as the increase in
thermal conductivity; thus, no abnormal heat transfer enhancement was
observed.
Yenilenebilir enerji kaynaklarıyla elektrik üretimi üzerine araştırmalar hızlı bir şekilde ilerlese de fosil yakıtlarla elektrik üretiminin hem dünyada hem Türkiye’de uzun bir süre daha sürmesi beklenmektedir. Hem çevrede oluşturduğu zararlı etkiler hem de tükenme riskinin yüksek olması, fosil yakıtların termik santrallerde verimli bir şekilde tüketilmesini zorunluluk haline getirmiştir. Fosil yakıtın bir türü olan kömür, elektrik üretmek amacıyla termik santrallerde yaygın olarak kullanılmaktadır. Kömür yakıtlı termik santrallerde kullanılan kazan, süper kritik bir kazan seçildiğinde santral verimi artırılabilir. Bu çalışmada Zonguldak ilinde bulunan Eren Enerji’ye ait kömür yakıtlı süper kritik termik santralin termodinamik performansı, enerji ve ekserji analiz metotlarıyla incelenmiştir. Santralde bulunan her bir elemana ait enerji kayıpları ve tersinmezlikler hesaplanmıştır. Enerji analizi, kömürün kimyasal enerjisinin %48.5’inin kondenserde soğutma suyuna aktarıldığını; ekserji analizi ise kömürün kimyasal ekserjisinin %49.2’sinin kazanda yok edildiğini göstermiştir. Santralin enerji verimi %33.65, ekserji verimi ise %31.42 olarak hesaplanmıştır.
N owadays, the cooling systems are used in various areas such as energy transfer, computer systems, electronic systems and heating. Cooling systems provide much more efficient results with recent technology. For decades, many studies include nanofluids that used as refrigerant for cooling systems.The nanoparticle is a solution formed by the suspension of the nanoparticles in the liquid homogeneously and allowing the transport of the particles through the base liquid. Generally, metal particles and oxides are suspended and transported in pure water or ethylene glycol. We anticipated the heat transfer will be increase by the thermodynamic properties of nanoparticles.In recent years there have been many studies on the use of nanofluids in cooling systems. Some of those;
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