Purpose Using suspended nanoparticles in the base fluid is known as one of the most efficient ways for heat transfer augmentation and improving the thermal efficiency of various heat exchangers. Different types of nanofluids are available and used in different applications. The main purpose of this study is to investigate the effects of using hybrid nanofluid and number of plates on the performance of plate heat exchanger. In this study, TiO 2 /water single nanofluid and TiO 2 -Al 2 O 3 /water hybrid nanofluid with 1% particle weight ratio have been used to prepare hybrid nanofluid to use in plate type heat exchangers with three various number of plates including 8, 12 and 16. Design/methodology/approach The experiments have been conducted with the aim of examining the impact of plates number and used nanofluids on heat transfer enhancement. The performance tests have been done at 40°C, 45°C, 50°C and 55°C set outlet temperatures and in five various Reynolds numbers between 1,600 and 3,800. Also, numerical simulation has been applied to verify the heat and flow behavior inside the heat exchangers. Findings The results indicated that using both nanofluids raised the thermal performance of all tested exchangers which have a various number of plates. While the major outcomes of this study showed that TiO 2 -Al 2 O 3 /water hybrid nanofluid has priority when compared to TiO 2 /water single type nanofluid. Utilization of TiO 2 -Al 2 O 3 /water nanofluid led to obtaining an average improvement of 7.5%, 9.6% and 12.3% in heat transfer of heat exchangers with 8, 12 and 16 plates, respectively. Originality/value In the present work, experimental and numerical analyzes have been conducted to investigate the influence of using TiO 2 -Al 2 O 3 /water hybrid nanofluid in various plate heat exchangers. The attained findings showed successful utilization of TiO 2 -Al 2 O 3 /water nanofluid. Based on the obtained results increasing the number of plates in the heat exchanger caused to obtain more increment by using both types of nanofluids.
Space heating and hot water supplying were usually done by utilizing combi boilers. Various kinds of combi boilers are available. In the last years condensing type combi boilers have been introduced that have high efficiency in comparison to conventional one. In the present study the impact of combi boiler type on pollutant gas emissions was experimentally investigated. Three various combi boiler including condensing, full condensing and conventional type combi boilers were utilized in the experiments. Moreover, the experiments were conducted in various outlet hot water temperatures to determine the effect of temperature. The achieved findings indicated that in all temperatures utilizing condensing and full condensing combi boilers decreased NO, NO x and SO 2 , gas emissions considerably.
Solar energy is a safe and clean source of energy, available on the Earth throughout the year. A photovoltaic/thermal (PV/T) system is a device designed to take solar energy and convert it into electrical/thermal energy. Photovoltaic/ thermal systems can also be useful to produce hot fluid (usually water) along with the generation of electrical energy. In addition, the electric generating performance of PVs increases with heat discharging ability of thermal system, which also prevents overheating in PV systems. Nanofluid is a new generation heat transfer fluid that delivers higher thermal conductivity and heat transfer rate compared to conventional fluids. The thermal conductivity of the nanofluid depends on the size of the nanoparticles, concentration of the nanofluid, and the method of its preparation. In this study, it is aimed to increase the thermal heat transfer of the PV/T system by using hybrid nanofluids, manufactured by adding 0.5% Fe<sub>2</sub>O<sub>3</sub> and Fe<sub>3</sub>O<sub>4</sub> nanoparticles to the water as a working fluid. By using hybrid nanofluids, increase in bidirectional performance along with enhanced cooling is achieved. In the experimental study, more heat was withdrawn from the heated PV panels by utilizing the high thermal conductivity of the hybrid nanofluid, and the best improvement in total efficiency was obtained as 86% for the hybrid nanofluid. With the use of hybrid nanofluids in the cooling circuit, the electrical and thermal efficiency of the PV panel has reached to overall 81% on average basis.
In recent years, solar water collectors are commonly preferred for supplying heated water to be utilized in various processes. In the present study, a solar water collector equipped with a helically coiled absorbing surface has been manufactured and experimented under various working conditions to determine its general behavior. The main goal of using a helically coiled absorber is enhancing energy harvest in the collector by ensuring vertical angle between the absorbing area and incident radiation. In addition, for providing greater increase in thermal efficiency, magnetic type nanofluid has been used as a working fluid. In this context, NiFe<sub>2</sub>O<sub>4</sub> nano-sized particles have been mixed with water at the ratio of 2% (wt./wt.). Accordingly, the performance of the collector has been empirically examined using both water and magnetic nanofluid at two different flow rates. The overall results of the present survey exhibited successful use of magnetic type nanofluid in a solar collector equipped with a helically coiled absorbing surface. Utilizing magnetic nanofluid in the collector as circulating fluid raised the thermal efficiency on an average of 20.29% and 23.59% at volumetric flow rates of 0.5 lpm, and 0.9 lpm, respectively. Moreover, utilizing NiFe<sub>2</sub>O<sub>4</sub>/water nanofluid in the water collector enhanced the exergy efficiency on an average of 44.53% and 40.04% at volumetric flow rates of 0.5 lpm and 0.9 lpm, respectively.
In this paper, thermal performance of the diatomite-deionized water nanofluid usage as the working fluid in a wickless loop heat pipe at varying operating conditions was experimentally and numerically investigated. A straight copper tube with an inner diameter of 13 mm, which is of 1 mm wall thickness and 1 m in-length, was used as the thermosyphon in the experimental work. The pipe was charged with deionized water and diatomite-based nanofluid respectively, by one-third of the overall volume of the heat pipe. Diatomite has high absorption capability and thus it can be considerably absorbed by the deionized water. Herewith, the disadvantages of the nanofluids, flocculation and sedimentation, are remarkably annihilated. Moreover, by using a surface-active agent, Triton X-100, these disadvantages were tried to be removed. The experiments were conducted for varying heat loads in evaporator section and cooling water mass flow rates in condenser section of the heat pipe in order to determine the operating parameters under maximum efficiency conditions of the heat pipe. Using experimental findings such performance parameters as efficiency, thermal conductivity, improvement rates in heat transfer were determined and then numerical analysis were performed. The maximum efficiency and the improvement in thermal resistance of the heat pipe when it is filled up with diatomite-based nanofluid in place of deionized water were obtained from the recurrent tests as 14.57%and 43.4%, respectively. Consequently, the experimental and numerical findings were compared to each other and it is pointed out that they are in a good agreement.
Bu çalışmada, düz ve hapsedici yüzeyli emici plakalı kurutma fırınları tasarlanmış, imal edilmiş ve performansları deneysel olarak karşılaştırılmıştır. Deneylerde kivi kurutulmuştur. Kiviler, kabukları soyulduktan sonra 4 - 6 mm kalınlığında dilimlenerek 100 g olacak şekilde deneye hazırlanmıştır. Kurutma sisteminde kiviler başlangıç nem miktarından (0.83 g su/g yaş madde) son nem miktarına (0.056 g su/g yaş madde) kadar kurutulmuştur. Deneyler, 2.5 – 3.0 ve 3.5 m/s hava hızlarında gerçekleştirilmiştir. Yapılan deneylerde; düz yüzeyli kurutma fırınının kurutma odası ortalama sıcaklığı 41.6 °C iken hapsedici yüzeyli kurutma fırınının kurutma odası ortalama sıcaklığı 44.1 °C olarak tespit edilmiştir. Üç farklı hız ile yapılan deneylerde; düz yüzeyli kurutma fırınında kurutma süresi 390 dakika sürer iken hapsedici yüzeyli kurutma fırını ile yapılan deneylerde; 2.5 m/s’de kurutma süresi 390 dakika, 3.0 m/s’de kurutma süresi 360 dakika ve 3.5 m/s’de kurutma süresi 330 dakika sürmüştür. Hapsedici yüzeyli kurutma fırını, düz yüzeyli kurutma fırınına göre ortalama 30 dakika daha kısa sürede kurutma işlemini gerçekleştirdiği sonucuna varılmıştır.
As wiring up the many thermoelectric generators in serial, voltage can be increased and wiring up the parallel the current can be increased. In this work, experiment set has occured with thermoelectric generators. The generator surface which is need to keep warm is heated by waste gases produced in stove pipe and cooled water is passed through the cold surface to keep cool. Electricty production has occured because of the temperature differences. During operation the changing of voltage range is observed between 5,11V and 8,69V. When the flowrate is 0,083 lt/s, the maximum performance has observed with 8,69V and 1,45A. Varying the cooling water flowrate in experiment, changing of electricty production has observed and the results has shown graphical
