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The popularity of the studies on improving the thermal properties of base fluids in thermal engineering applications is considerably increasing day by day. Recently, many researchers have proved that the use of nanoparticles along with the base fluids exhibits better thermal properties as well as better system performance. In line with this, it is noticed a respectful increase in the number of studies regarding nanoparticle use in refrigeration systems. Accordingly, the present paper aims to summarize the preparation of nanofluids, the variation of thermophysical properties, the stability of nanofluids, impacts on the system performances of nanofluid usage, limitations, and challenges of nanoparticle usage, particularly in the refrigeration systems. Previous studies revealed that the heat transfer mechanism of the lubricants and refrigerants is highly improved with nanoparticle addition. It is observed that the increase in thermal properties becomes more visible as nanoparticle fractions increase, but this case may worsen the viscosity of nanofluids. The enhanced thermal properties contribute to improving refrigeration system performance. Many papers emphasize that nanoparticle-doping triggers an increase in system performance by both reducing the compressor power input and increasing the cooling capacity of the refrigeration systems. However, some critical points such as stability, homogeneous distribution, agglomeration, and sedimentation considerably influence the sustainability of performance improvement. In conclusion, nanoparticle-doping for refrigeration systems can be accepted as a very promising way of improving the performance, nevertheless, some questions such as high cost, toxic effect, poor stabilization, erosion effect, high viscosity, clogging issues should be more addressed in the future.

In this paper, a concentrated photovoltaic-thermal solar dryer (CPV/TSD) using nano-enhanced PCM (Al2O3Paraffin wax) is experimentally studied. A comprehensive thermodynamic analysis of the system according to the first and second laws is discussed. Besides, the drying parameters (moisture content and moisture ratio) are predicted using the two machine learning algorithms (ANN and SVM) and compared the prediction success with four evaluation metrics (R2, rRMSE, MBE, and rMAE). The overall thermal energy efficiency and exergy efficiency of the CPV/TSD system are found to be 20% and 8%, respectively. Although solar radiation to the environment has decreased a lot, it has been found that the thermal energy transferred to the nano-enhanced PCM prevents the decrease in greenhouse temperature for the first 100 min. In the system, mushrooms are dried from the initial moisture content of 17.45 g water/g dry matter to the final moisture content of 0.0515 g water/g dry matter. Then the drying rate value for CPV/TSD system is calculated to be 0.436 g matter/g dry matter.min. On the other hand, even if both ANN and SVM algorithms have exhibited very satisfying results, ANN is coming to the fore in the prediction of the drying parameters considering all evaluation metrics together. WOS:000637191800006 2-s2.0-85102023951

Solar thermal systems are generally utilized for providing sustainable and environmentally friendly thermal energy that can be used in different applications. In the present study, a temperature-controlled fluidized bed solar drying system along with flat plate and plate with zigzag fins has been designed, manufactured, and experimentally tested. In the first step, the thermal behavior of designed solar air collectors has been numerically modeled. In the next step, the drying system's performance has been experimentally investigated. The overall efficiency of the system was found to be 64%. The maximum exergy efficiency of flat and zigzag plate solar air collectors was calculated as 7.2% and 11.6%, respectively. Then moisture content (MC) and moisture ratio (MR) values were modelled by response surface methodology (RSM), and the predicted results were compared with four metrics. It was found that the drying parameters were highly fitted with the mathematical models. MC metric was predicted with accurate values for performance criteria of R2, R-RMSE, and MBE as 0.9995, 1.94%, and ?0.0096, respectively. The general outcomes of numerical, experimental and modeling analyses of this research exhibited successfulness of the developed the fluidized bed solar drying system. © 2021 Elsevier Ltd 2-s2.0-85119097624

A comprehensive thermodynamic analysis of a refrigeration system with an internal heat exchanger was reported for four various refrigerants as an alternative to R134a. The preferred refrigerants in this paper have zero ozone-depleting potential and fairly low global warming potential value compared with reference R134a. These refrigerants are from both the HC group (R290 and R600a) and the HFO group (R1234yf and R1234ze(E)). Basically, the refrigeration system consists of a compressor, condenser, evaporator, expansion valve, and internal heat exchanger as well. Energy-exergy analyses and environmental impact assessments depending on the compressor energy consumptions are evaluated in the current study. The system performance was theoretically carried out at two different evaporation temperatures of 0 and -8 degrees C. Based on the obtained results from this study, the highest performance was achieved in R600a from HC group refrigerants and R1234ze(E) from HFO group refrigerants. As compared with R134a, in the COP value of R600a an increase of 3.2% at the evaporation temperature of 0 degrees C and 3.4% for the evaporation temperature of -8 degrees C was achieved. On the other hand, the COP value for R1234yf was decreased by 2% at the evaporation temperature of 0 degrees C and by 2.57% at the evaporation temperature of -8 degrees C. Considering the CO2 emissions, R600a was located at the first order in terms of the lowest CO2 emissions and R1234ze(E) follows R600a. In conclusion, R600a presented the highest performance compared with R134a in a refrigeration system with an internal heat exchanger. WOS:000557881000003 2-s2.0-85087983638

In this study, the effects of malfunctions and problems occurring in the system components of air handling units, which are the main elements of the air conditioning system, on the energy consumption were investigated. Investigations were carried out in 10 air handling units located in 5 different shopping centers of Turkey. The malfunctions and problems that may occur in operation of air handling units were determined and the problems causing the decrease in the efficiency prescribed by the design characteristics were determined. For this purpose, rod-type anemometer measuring the airflow in the air handling unit ducts, propeller-type anemometer, and thermal camera were used to measure air tightness and heat losses in the body structure. Also, the tension control of the belt of the fan motors, which is one of the main components of the energy consumption unit, and the pollution control of the air filter have also been carried out. The flow rate of water circulating in air handling units was determined, and losses were detected by energy and exergy analyses with thermodynamic parameters for summer and winter periods. As a result of the calculations, it was determined that the energy efficiency of the air handling units in the cooling period was 63.7% and the exergy efficiency was 59.6%. The energy loss is 471 kW and the exergy loss is 27 kW in the cooling period. The energy loss is 957 kW and the exergy loss is 127 kW in the heating period. The energy efficiency and the exergy efficiency during the heating period was calculated to be 75% and 41.7%, respectively. WOS:000557881000002 2-s2.0-85087968080

Deep learning (DL), Artificial Neural Network (ANN), Kernel Nearest Neighbor (k-NN), and Support Vector Machine (SVM) have been applied to numerous fields owing to their high-accuracy and ability to analyze the non-linear problems. In this study, these machine learning algorithms (MLAs) are used to predict emission and performance characteristics of a CI engine fuelled with various metal-oxide based nano particles (Al2O3, CuO, and TiO2) at a mass fractions of 200 ppm. Assessed parameters in the study are carbon dioxide (CO), nitrogen oxide (NOx), exhaust gas temperature (EGT), brake specific fuel consumption (BSFC), and brake thermal efficiency (BTE). To evaluate the success of algorithms, four metrics (R-2, RMSE, rRMSE, and MBE) are discussed in detail. Tests performed at varying engine speeds from 1500 rpm to 3400 rpm with the intervals of 100 rpm. The addition of nanoparticles simultaneously reduced CO and NOx emissions because they ensured more complete combustion thanks to their inherent oxygen, the higher surface to volume ratio, superior thermal conductivities and their catalytic activity role. Further, the nano-sized particles ensured an accelerated heat transfer from the combustion chamber. In comparison with that of neat diesel fuel, the reduction in NOx is found to be 3.28, 7.53, and 10.05%, and the reduction in CO is found to be 8.3, 11.6, and 15.5% for TiO2, Al2O3, and CuO test fuels, respectively. Moreover, the presence of nanoparticles in test fuels has improved engine performance. As compared with those of neat diesel fuel, the doping of nanoparticles drops the BSFC value by 5.54, 7.89, and 9.96% for TiO2, CuO, and Al2O3, respectively, and enhanced BTE value to be 6.15, 8.87, and 11.23% for TiO2, CuO, and Al2O3, respectively. On the other hand, it can be said that all algorithms presented very satisfying results in the prediction of CI engine responses. All R-2 has changed between 0.901 and 0.994, and DL has given the highest R-2 value for each engine response. In terms of rRMSE, all results (except for one result in k-NN) are categorized as excellent according to the classification in the literature. Considering all metrics together, DL is giving the best results in the prediction of engine responses for the dataset used in this paper. Then it is closely followed by ANN, SVM, and k-NN algorithms, respectively. In conclusion, this paper is proving that the nanoparticle addition for ICEs is significantly dropping the exhaust pollutants, and improving the engine performance, and further the results can be successfully predicted with the machine learning algorithms. (c) 2020 Elsevier Ltd. All rights reserved. Duzce University Scientific Research Projects Coordination UnitDuzce University [2020.07.04.1097, 2019.07.04.1049]; Duzce UniversityDuzce University This present work is being funded by Duzce University Scientific Research Projects Coordination Unit with the project numbers 2020.07.04.1097, and 2019.07.04.1049. The authors thank Duzce University for its financial support, and express special thanks to PhD Candidate Melahat Sevgul Bakay from Biomedical Engineering Department at Duzce University for her valuable suggestions in the prediction stages of the paper. WOS:000596172500006 2-s2.0-85094937244

This study aims to investigate the performance of R417A, R422A, R422D and R438A refrigerants as alternatives to R22, in a commercial type refrigeration system operating with R22 refrigerant. To this end, first of all, the cooling capacity and coefficient of performance (COP) values were calculated for all refrigerants used in the experimental setup. Then, two methods were proposed, Pearson's Correlation Similarity Analysis (PCSA) and surface temperature-based COP (COPST), to evaluate the success of each alternative refrigerants, and R22 with infrared image analysis, separately. The COP values obtained for the refrigerants with the mathematical method are R22 4.07, R438A 3.88, R417A 3.63, R422D 3.37, and R422A 3.18, respectively. Both the COP values and the PCSA values (R438A 0.9425, R417A 0.9343, R422D 0.9167 and R422A 0.9080) show the proximity between the R22 refrigerant and other refrigerants. Similarly, the COPST method revealed the values of R22 6.8865, R438A 5.9539, R417A 5.3273, R422D 4.9898 and R422A 4.3057, and the fact that it has the same order with the other two methods demonstrates its operability in the performance test application with the developed infrared image processing. The compatibility of the order in the experimental results obtained from the PCSA and COPST methods and the COP calculation method and has proved that thanks to infrared imaging, the remote performance analysis of the refrigeration system can be successfully performed. Scientific and Technological Research Council of Turkey (TuBTAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [218M936] This study was supported by The Scientific and Technological Research Council of Turkey (TuBTAK) with the project number 218M936. WOS:000663246300001 2-s2.0-85108228679

Soğutma sistemlerinde soğutucu akışkan kaçakları montaj ve servis hatalarından kaynaklanabildiği gibi, zaman içinde boru ve bağlantılardaki titreşime ve malzeme yıpranmasına bağlı olarak oluşabilmektedir. Bu durum, soğutma sisteminin çalışma verimini engelleyerek, soğutma/ısıtma kapasitesini düşürme ve sistemde kızgınlık artışına neden olmaktadır. Ayrıca, emme hattında vakum düşüşü gerçekleşeceği için sisteme hava ve nem girişinden dolayı iç kirlenme ve tıkanma oluşmaktadır. Soğutucu akışkan kaçaklarının tespitinde köpükleme ve akışkan kaçak dedektörü ile algılama kullanılan en yaygın yöntemlerdir. Bu çalışmada, bir soğutma sisteminde oluşabilecek kaçakların tespiti için, kızılötesi görüntü işleme tekniğine dayalı yeni bir yöntem önerilmiştir. Bunun için ilk olarak, R22 soğutucu akışkan kullanılarak hazırlanan deney düzeneğinde, 7 farklı noktada, farklı zamanlarda yapay kaçaklar oluşturulur. Daha sonra, sağlam sistem kızılötesi görüntüsü ile yapay kaçak yapılmış sistem görüntüleri üzerinden daha önceden tespit edilmiş 12 alt bölgeden öznitelik verileri çıkartılmaktadır. Öznitelik özellik verilerinin elde edilme işleminde, belirlenen 12 bölgenin yüzey sıcaklık bilgileri kullanılmıştır. Yüzey sıcaklık bilgileri minimum, maksimum, ortalama ve en yoğun sıcaklık bilgisi olarak dört farklı şekilde çeşitlendirilmiştir. Kızılötesi görüntü analizi işlemini gerçekleştirmek için elde edilen öznitelik verileri Pearson Korelasyon Benzerlik Analizi (PKBA) işlemine sokulmaktadır. Son olarak, izlenmesi gereken 12 alt bölgenin PKBA sonuçları bir eşik değere tabi tutularak, eşik değerin altında kalan bölgelerde “Kaçak vardır” tespiti yapılmaktadır. Diğer bir olası durum ise, eğer sağlam ve kaçak kızılötesi karşılaştırmasında, benzerlik değerinin çok yüksek bir değer oluşmasında, bu bölgeler için “Kaçak yoktur” sonucunu vermektedir. Kızılötesi görüntü işleme tekniği kullanılarak gerçekleştirilen PKBA ile kaçak tespit işlemi, kullanım kolaylığı, hızlı ve eş zamanlı kaçak tespit etme noktasında daha avantajlı olduğunu göstermiştir.

The globalising world, rapidly developing technology and growing population have brought many problems and led to disrupting the world ecological balance. Today, existing energy sources reached such a level that cannot meet the current needs of the world. Due to the fact that fossil fuels will run out in near future, it has made mankind tending to seek alternative energy sources. The main issues addressed in this paper are the history of greenhouse gas emissions (GHGe) and relations with nuclear energy policy, particularly in Turkey. Currently, nuclear has much less GHGe and high energy-efficiency, and also meets 10.6% of the world primary electiricty energy demand. Therefore, countries seriously began to evaluate nuclear energy instead of fossil-fuels. In line with this, Turkey started to build third nuclear plants and aims to meet at least 15% of its primary electiricity energy demand. Hereby, Turkey is not only reducing dependence on fossil-fuels but also planning to reach the undertaken GHGe level as a country of signed the Kyoto protocol. WOS:000684131100005 2-s2.0-85112330847

Agbulut, Umit/0000-0002-6635-6494 WOS: 000518657000001 The generation of electrical energy with photovoltaic modules is a highly useful and environmentally friendly method. For this reason, studies to increase the electrical energy production from photovoltaic (PV) modules have gained great importance. Concentrated PV systems constitute a significant part of these studies. The major problems with the concentrated PV systems are the risks of lowering the efficiency of the cells (i.e., concentration process increases PV cell temperature) and the thermal damage that can occur with sudden temperature increases. In order to avoid these risks, various applications are used to cool concentrated PV modules. In this study, an active system, which was developed for cleaning and cooling PV modules, was tested. The aim of the present study was to ensure that the surfaces were clean and free of external, contaminating factors such as dust and dirt, and that the PV cells were cooled. During the experiments, two different systems were compared: the system with the cleaning-cooling processes and the one without these processes. Prior to starting experiments, a hydrophobic liquid onto the surfaces of the PV modules was applied to facilitate the cleaning process. The results of the experiments revealed that the temperature of the PV module was 50 degrees C in the cleaning-cooling process and 67 degrees C in the system without the cleaning-cooling process. On the other hand, it was observed that the proposed design increased the power output of PV module up to 40%.

The interest in solar energy is increasing day by day because it is clean and limitless. Concentrated photovoltaic and thermal systems (CPV/T) are one of the systems that use in the winter and the summer, attract great attention among solar energy systems. The main purpose of this research is to discuss the capacity of a CPV/T to simultaneously convert solar energy into electrical energy and thermal energy, especially in winter seasons. While only thermal energy is obtained in many concentrated air collectors (CAC) used in the literature, in this study, energy is stored with the help of phase change material (PCM). Ethyl alcohol and water blend were utilized as a working fluid and paraffin wax was also utilized as a PCM. In this study, system performance was handled by applying energy, exergy and environmental economic analyzes. In the results, the average solar radiation was concentrated from 536 W/m(2) to 737 W/m(2). The average overall thermal efficiency and PV module efficiency of the CPV/T were calculated as 73% and 15%, respectively. In other words, the overall system efficiency of the CPV/T was obtained as 88%. The average exergy efficiency of the CPV/T was calculated as 10%. Concerning the environmental aspect, 1.11 kg of CO2 emission per hour into the atmosphere could be prevented by using such a system. In the conclusions, the present paper has reported that the integration of a PCM and air collector into a CPV/T system provided higher energy efficiency in the winter season. WOS:000689337400002 2-s2.0-85112469888

Gurel, Ali Etem/0000-0003-1430-8041 WOS: 000408180900008 In this study, we examined the effect of the use of paraffin wax on the panel temperature of concentrated solar panels. Some tests were performed on various days for three months (including spring, summer, and winter months). With the help of the experimental results, new approaches have been made as concentrator ratio, area ratio, concentrator efficiency and power coefficient. As a result of this approaches the concentrator ratio was found to be 3. When the concentrator ratio was 3, the panel temperature of the system with paraffin was found to be between 80 and 100 degrees C, while that of the other system was found to be above 100 degrees C. Panel efficiency might be reduced down to 10% at these temperatures. The study also included the development of a mathematical model of the changes in the panel temperature of the concentrated systems in which paraffin was not used. The temperature at the back of the panels could be calculated by this mathematical model, depending on the ambient temperature and the concentrated solar radiation. The correlation coefficient of the mathematical model was found to be 0.929. The test results of two days, which were not included in the model, were used to determine the reliability of the model, and the panel temperatures were calculated using the correlation coefficients of 0.933 and 0.966. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Due to some serious environmental problems like global warming and greenhouse effect, studies on solar energy systems are being conducted all over the world. The studies conducted in recent years are on hybrid designs in which solar energy systems can realize both electricity and heat production at the same time. In this way, both electrical energy and heat energy can be generated from the same system In this study, the design and analysis of a concentrated solar air collector with a heat storage unit were carried out.. In the solar air collector, heat energy was depot in paraffin wax, and the electrical energy which was stored in the battery using the PV (photovoltaic) modules in the system enabled the operation of the system fan. The experiments which aimed at determining system performance were carried out in winter when the ambient temperature was low. The experiments were performed with or without a heat storage unit, and a comparative analysis was made. It was found that the temperature of the air released from the collector ranged from 15 degrees C to 40 degrees C when the exterior temperature was -5 degrees C. The average efficiency of the concentrated system without the heat storage unit was calculated as 67%. The average efficiency of the concentrated system with the heat storage unit was calculated as 96%. Karabuk University Scientific Research Projects Coordination UnitKarabuk University [KBu-BAP-16/ 1-YL-137] Authors thank the Karabuk University Scientific Research Projects Coordination Unit for their support for this study. Our project number is KBu-BAP-16/ 1-YL-137. WOS:000521691600001 2-s2.0-85082192631

Today, it has been observed that with various protocols, halogenic chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) refrigerants will not be used in the future and various alternatives must be created. In the conventional cooling efficiency coefficient (COP) calculation method, thermodynamic property tables and pressure-enthalpy diagrams are used. Thanks to the proposed method, it will not be necessary to use these tables and diagrams when calculating the COP. It will be sufficient to take images from the regions indicated by the infrared imaging system. In this study, performance analysis of commercial refrigeration systems of R417A and R438A fluids that are alternative to R22 fluid, which are friendly to the ozone layer, has been performed. With the prohibition of the consumption of CFC gases, the use of HCFC gases, another gas group that damages the ozone layer, has been restricted and then banned. The most used of these gases is R22 gas. In order to perform the performances of reference R22 gas and R438A and R417A gases with infrared image analysis, two methods are proposed: COP with regional feature data acquisition and COP. In addition, on the two interfaces realized, the sizes obtained from infrared images are compared graphically and numerically. According to the obtained numerical and visual application results, R438A showed the closest performance to R22 gas. Compared to traditional computational performance tests, the ease of use of the system has shown that it is more advantageous in terms of remote measurement and simultaneous recording., Günümüzde çeşitli protokoller ile halojenik kloroflorokarbon (CFC) ve hidrokloroflorokarbon (HCFC) soğutucu akışkanlarının ilerleyen zamanlarda kullanılmayacağı ve bu akışkanlara çeşitli alternatiflerin oluşturulması gerektiği gözlemlenmiştir. Geleneksel soğutma etkinlik katsayısı (COP) hesaplama yönteminde, termodinamik özellik tabloları ve basınç-entalpi diyagramları kullanılmaktadır. Önerilen yöntem sayesinde, COP hesaplanırken, bu tablo ve diyagramların kullanılmasına gerek duyulmayacaktır. Kızılötesi görüntüleme sistemi ile belirtilen bölgelerden görüntü alınması yeterli olacaktır. Bu çalışmada, R22 akışkanına alternatif olan, ozon tabakasına dost R417A ve R438A akışkanlarının ticari soğutma sistemlerine yönelik performans analizi yapılmıştır. CFC gazların tüketiminin yasaklanması ile birlikte gelinen süreçte ozon tabakasına zarar veren diğer bir gaz grubu olan HCFC gazların da kullanımı önce sınırlandırılmış ardından tamamen yasaklanmıştır. Bu gazlardan en çok kullanılanı R22 gazıdır. Referans R22 gazı ile R438A ve R417A gazlarının performansları kızılötesi görüntü analizi ile gerçekleştirmek için bölgesel öz nitelik veri elde edinimi ile COP olmak üzere iki yöntem önerilmiştir. Ayrıca gerçekleştirilen iki ara yüz üzerinde, kızılötesi görüntülerden elde edilen büyüklükler, grafiksel ve sayısal olarak karşılaştırılmaktadır. Elde edilen sayısal ve görsel uygulama sonuçlarına göre, R22 gazına en yakın performansı R438A göstermiştir. Geleneksel hesaplamalı performans testlerine göre, uygulanan sistemin kullanım kolaylığı, uzaktan ölçüm ve eş zamanlı kayıt alma noktasında daha avantajlı olduğunu göstermiştir.

The importance of energy increases in human life with the development of technology. However, most of the world's energy needs are still met by fossil fuels. The interest in renewable energy is increasing due to the increase in demand for fossil fuels, their limitedness, and environmental damage. Solar energy, which is an unlimited and clean energy source, is among the most popular renewable energy sources. Solar energy is used by processes such as heating and electricity generation. In this study, the emission amount of polycrystalline and cadmium telluride (CdTe) photovoltaic (PV) panels to the environment during the life cycle were compared. During the life cycle, the amount of emission released to the environment during the production, recycling, and electricity generation of the panel was determined. In addition, energy payback times of these two PV types were calculated. The emission amount for both of 1 m2 polycrystalline and CdTe PV panel throughout the life cycle was determined to be 201.4 and 115.04 kg?CO2, respectively. Besides, the average energy payback period of the polycrystalline panel is 0.92 years, while it is 0.57 years for the CdTe panel. In addition, the emission amount of the solar panel and the natural gas-powered thermal power plant known as a clean energy source were compared. As a result, a huge difference was observed between the emission amount released by the PV panel to the environment and the emission released as a result of the energy produced by the thermal power plant under the same conditions during its 17-year lifetime. PV panel saves 1.72 tons of CO2 emissions compared to the thermal power plant, and so PV panels appear to be 9.52 times more environmentally friendly. © 2020 Elsevier B.V. 2-s2.0-85087972314

Agbulut, Umit/0000-0002-6635-6494 WOS: 000522876500084 This paper intended to investigate the impact of corn oil methyl-ester and diesel blends on performance, cornbustion and emission characteristics at varying injection pressure (210 and 230 bar). The tests were performed at a constant engine speed of 2000 rpm, and at two different engine loads of 5 and 10 Nm. Corn oil methyl-ester was produced by transesterification method in the study and then blended at 10%, 20% and 50% by volume into neat diesel fuel. The results presented that corn oil methyl-ester could improve combustion process owing to its high oxygen content in comparison with that of B0 fuel. High-injection pressure reduced the droplet diameter and accelerated the combustion process. This case has generally caused to high cylinder pressures. With respect to emissions, it was observed that CO (down to 66.67% at 230 bar) and HC (down to 52.38% at 230 bar) were sharply reduced depending on the increment of the blending rates of biodiesel while NOx (up to 22.45% at 230 bar) increased significantly. Depending on the increasing rate of corn oil methyl-ester in the blends, more fuel mass was injected into the combustion chamber and specific fuel consumption in biodiesel content-fuels were, therefore, higher than that of low injection pressure. Additionally, thermal efficiency decreased with the increment of biodiesel content owing to the lower heating value of biodiesel.

This study carried out in two stages. In the first stage, four different-sized layers were designed and manufactured for a concentrated photovoltaic system. These layers were used to change the concentration ratio and area ratio of the system. Furthermore, a new power coefficient equation with this paper is proposed to the literature for the determination of the system performance. In the second stage of the study, the power outputs measured in the study were predicted with four machine-learning algorithms, namely support vector machine, artificial neural network, kernel and nearest-neighbor, and deep learning. To evaluate the success of these machine learning algorithms, coefficient of determination (R-2), root mean squared error (RMSE), mean bias error (MBE), t-statistics (t-stat) and mean absolute bias error (MABE) have been discussed in the paper. The experimental results demonstrated that the double-layer application for the concentrator has ensured better results and enhanced the power by 16%. The average concentration ratio for the double-layer was calculated to be 1.8. Based on these data, the optimum area ratio was determined to be 9 for this V-trough concentrator. Furthermore, the power coefficient was calculated to be 1.35 for optimum area ratio value. R-2 of all algorithms is bigger than 0.96. Support vector machine algorithm has generally presented better prediction results particularly with very satisfying R-2, RMSE, MBE, and MABE of 0.9921, 0.7082 W, 0.3357 W, and 0.6238 W, respectively. Then it is closely followed by kernel-nearest neighbor, artificial neural network, and deep learning algorithms, respectively. In conclusion, this paper is reporting that the proposed new power coefficient approach is giving more reliable results than efficiency data and the power output data of concentrated photovoltaic systems can be highly predicted with the machine learning algorithms. (c) 2020 Elsevier Ltd. All rights reserved. Karabuk University Scientific Research Projects Coordination UnitKarabuk University [KBU-BAP-15/1-YL-019] This study is supported by Karabuk University Scientific Research Projects Coordination Unit. Project Number: KBU-BAP-15/1-YL-019. WOS:000561594800091 2-s2.0-85086895804

In this study, a solar meter was designed to measure high solar radiation. The solar meter uses the characteristic properties of a solar cell in order to measure solar radiation. In this way, measurements can be carried out without any limitations. The solar radiation equation was entered into the ARDUINO microcontroller in the solar meter, and the results were compared through another commercial solar meter. These results were entered into STATGRAPHIC software and three different functions with high regression values were obtained. These three functions were entered into the Arduino microcontroller and the experiments were repeated. According to the comparisons made using commercial device, R2 values were determined as 0.944, 0.936, 0.938, and 0.986 for the first equation and for three different functions, respectively. Based on the values obtained, it has been determined that the solar meter can make highly accurate measurements and after the development of appropriate functions, it can be employed especially in high solar radiation concentrated systems., Yapılan bu çalışmada, yüksek güneş ışınımını ölçmek için bir solar metre tasarlanmıştır. Solar metre bir solar hücrenin karakteristik özelliklerini kullanarak güneş ışınımı ölçebilmektedir. Bu sayede herhangi bir sınırlama olmadan ölçüm yapılabilmektedir. Güneş ışınımı eşitlikleri ARDUINO mikro kontrol kartı aracılığıyla tasarlanan solar metreye girilmiştir ve başka bir ticari solar metre ile karşılaştırılmıştır. Bu sonuçlar STATGRAPICH programına işlenerek yüksek regresyon oranına sahip 3 farklı fonksiyon elde edilmiştir. Bu 3 fonksiyon tekrar ARDUINO mikro kontrol kartına girilerek deneyler tekrarlanmıştır. Ticari cihaz ile karşılaştırıldığında elde edilen R2 değerleri birinci eşitlik için 0.944 ve 3 farklı fonksiyon içinse sırasıyla 0.936, 0.939 ve 0.986 olarak tespit edilmiştir. Elde edilen değerlere dayanarak, tasarlanan solar metrenin oldukça hassas ölçümler yapabileceği ve uygun fonksiyonların geliştirilmesinden sonra, özellikle yüksek güneş radyasyonlu yoğunlaştırıcılı sistemlerde kullanılabileceği belirlenmiştir.

Gurel, Ali Etem/0000-0003-1430-8041 WOS: 000381530600091 A new, mixed-mode, fluidized bed drying system was developed using a solar energy system. The system was comprised of a solar air collector, a parabolic trough collector, and a heat pump system. The performance of the fluidized bed drying system was assessed by conducting energy and exergy analyses. This fluidized bed dryer was used to investigate the drying kinetics of mint leaves. The temperatures of the air used for drying by the solar energy system and the heat pump system were 45 and 50 degrees C, respectively. The energy and exergy efficiencies of the system were found to be 50 and 26%, respectively. The heating coefficient of performance (HCOP) was suggested as a new performance parameter of a solar energy system. The heat pump system had a coefficient of performance (COP) value of five. In other words, the heating coefficient of performance of this solar energy system was 10. (C) 2016 Elsevier Ltd. All rights reserved.

Solar radiation (SR) knowledge plays a vital role in the design, modelling, and operation of solar energy conversion systems and future energy investment policies of the governments. However, these data are not measured for all regions due to the non-availability of SR measurement equipment at the weather stations. Therefore, SR has to be accurately predicted using various prediction models. In this research, four models from different classes are being used to predict monthly average daily global SR data. The models used in this study are based on a machine-learning algorithm (feed-forward neural network), empirical models (3 Angstrom-type models), time series (Holt-Winters), and mathematical model (RSM). As the prediction locations, four provinces (Ankara, Karaman, Kilis, and Sirnak) in Turkey are selected. The dataset including pressure, relative humidity, wind speed, ambient temperature, and sunshine duration is supplied from the Turkish State Meteorological Service and it covers the years 2008-2018. In the study, monthly average daily global SR data for the year 2018 is being predicted, and the performance success of the models is discussed in terms of the following benchmarks R-2, MBE, RMSE, MAPE, and t-stat. In the results, R-2 value for all models is varying between 0.952 and 0.993 and MAPE and RMSE value for all models is smaller than 10% and 2 MJ/m(2)-day, respectively. Evaluation in terms of t-stat value, no models exceed the t-critic limit. Considering all the models together, ANN has presented the best results with an average R-2, MBE, RMSE, MAPE, and t-stat of 0.9911, 0.1323 MJ/m(2)-day, 0.78 MJ/m(2)-day, 4.9263%, and 0.582, respectively. Then Holt-Winters, RSM, and empirical models closely followed it, respectively. (C) 2020 Elsevier Ltd. All rights reserved. Duzce University Research FundDuzce University [2019.07.04.1049]; Duzce UniversityDuzce University This study is supported by Duzce University Research Fund Project Number: 2019.07.04.1049. The authors are indebted to Duzce University for its financial support. WOS:000586917600008 2-s2.0-85087967783

Agbulut, Umit/0000-0002-6635-6494 WOS: 000494884000050 An experimental study was conducted to determine the effects of adding copper oxide (CuO) with 50 nm diameter into neat methanol (CH3OH) on the energetic and exergetic analysis of a concentrated air collector with vacuum tube heat pipe at different air velocities (1, 2 and 3 m/s). The experimental results clearly indicated that the nanofluid application enhanced the thermal properties and provided better performance for heat pipe applications. Considering all air velocities together, the average efficiency for neat methanol and CuO-Methanol nanofluid was achieved by 65% and 64%, respectively. Additionally, the average specific exergy outlet values for neat methanol and CuO-Methanol nanofluid were calculated as 206 J/kg and 298 J/kg, respectively. In the experiments, it is seen that the efficiency values of the system using the CuO-Methanol nanofluid reached higher values, as the solar radiation values were higher. In conclusions, this paper distinctly suggests that the presence of copper oxide in the base fluid can be used in a concentrated air collector with vacuum tube heat pipe particularly at the high radiation conditions and positively affects the performance of the system.

Ergun, Alper/0000-0003-0402-4088 WOS: 000466999400079 In this study, the efficiency of the rear-panel air velocity in cooling was investigated based on the temperature and solar radiation in the environment where the panels are located. During the cooling of the panels, the rear-panel temperature decreases, and accordingly, the open-circuit voltage of the panels increases. At present, the most important losses in panels are due to the increase in panel temperature depending on the solar radiation and outdoor air temperature. In this study, the rear-panel temperature changes were observed at 0-5 m/s air velocities and 10-40 degrees C. The calculations reveal that in winter weather conditions, the temperature of the panels did not increase at a level that would require cooling. This study investigated the heat transfer from the surface depending on the outdoor air temperature of the rear-panel air velocity and the changing rear-panel temperature. The effect of different outdoor air temperatures on the rear-panel heat transfer is minimal. When the air velocity was 5 m/s and the outdoor air temperature was 10-40 degrees C, the heat transfer in the Poly Crystal Solar panel was calculated as 11.6 W/m(2)K. (C) 2019 Elsevier Ltd. All rights reserved. Karabuk University Scientific Research Projects Unit, Karabuk/TURKEYKarabuk University The authors would like to thank the Karabuk University Scientific Research Projects Unit, Karabuk/TURKEY for providing the financial supports for this study.

Gurel, Ali Etem/0000-0003-1430-8041 WOS: 000358483200040 Photovoltaic (PV) module converts the incoming solar radiation into heat and electric energy. Due to this heating feature of photovoltaic modules, it is likely to produce heat energy from PV modules as well. Such systems are known as photovoltaic and thermal systems in the literature. In this study, a new design PV/T system was experimentally analyzed for cooling photovoltaic modules while heating water at the same time. PV/Tis a forced circulation system without pump. Therefore, these systems are different from those described in the literature. For all PV/T system, step-by-step exergy analysis has been performed according to obtained experimental results. PV module thermal exergy, solar collector thermal exergy, and PV module electrical exergy variations have been calculated for this exergy analysis. Overall, exergy efficiency was obtained as about 17% for 45 degrees C set temperature and 21% for 55 degrees C set temperature. (c) 2015 American Institute of Chemical Engineers Environ Prog, 34: 1249-1253, 2015

Merkezi ısıtma ve soğutma sistemlerinin en önemli parçası olan klima santrallerinde soğutucu serpantinüzerinden büyük miktarda su yoğuşmakta ve bu su genellikle en yakın gidere verilmektedir. Uygulamada da busu, büyük bir atık olarak nitelendirilmektedir. Hâlbuki özellikle %100 dış hava ile çalışan sistemlerdeki bu soğuksu depolanarak evaporatif soğutma da dâhil olmak üzere birçok uygulamada değerlendirilebilir. Bu çalışmada,klima santrallerinde yoğuşan suyun yeniden kullanımına yönelik farklı tasarımlar önerilmiştir. Çalışmada üçfarklı sistem üzerinde incelemeler gerçekleştirilmiştir. Birinci sistemde %100 taze havalı bir klima santralindenelde edilen yoğuşma suyunun, karışım havalı bir klima santralinin serpantininde ön soğutucu olarak kullanılmasıincelenmiştir. İkinci sistemde ise %100 taze havalı veya karışım havalı klima santralinin soğutucu serpantinindeyoğuşan suyun, bir soğutma kuleli chiller cihazında besleme suyu olarak değerlendirilmesi araştırılmıştır.Üçüncü sistemde ise %100 taze havalı veya karışım havalı klima santralinin soğutucu serpantininde yoğuşansuyun, hava soğutmalı kondenserli bir chiller cihazında kullanımı incelenmiştir. Yapılan psikrometrikhesaplamalar, %100 taze hava ile çalışan bir klima santralinde yaklaşık 80 kW’lık gizli ısının, tasarlanan busistemler aracılığıyla duyulur ısı olarak kullanılabileceğini göstermiştir The most important parts of central heating and cooling systems are air handling units. In the air handling units,large amounts of water condense from the cooling coil and this water is usually given to the waste water line. Inpractice this water is described as a major waste. Whereas, this cold water in systems operating with 100%outside air can be stored and it can be evaluated in many applications including evaporative cooling. In thisstudy, different designs were proposed for the recovery of condensed water in air handling units. Studies havebeen carried out on three different systems. In the first system, the using of the condensed water obtained from the 100 % fresh air handling units as a precooler in a coil of an air-handling unit with a mixture air wasinvestigated. In the second system, the condensing water in the cooling coil of the 100% fresh air or mixed airhandling unit was investigated as feeding water in a chiller device with cooling tower. In the third system, theusing of the water, which was condensed in the 100% fresh-air or mixed air handling units, in the chiller devicewith air cooled condenser was examined. Psychrometric calculations show that a latent heat of about 80 kW inan air conditioning unit operating with 100% fresh air can be used as sensible heat through these designedsystems.

Gurel, Ali Etem/0000-0003-1430-8041 WOS: 000415930200035 This study investigates convective-infrared drying characteristics of timber. The biggest disadvantage of infrared heating systems is the uncontrollable rise of the surface temperature up to extremely high values, which causes damage to the product. In this study, the power of an infrared system was controlled and adjusted according to the surface temperature of the product. In doing so, the surface temperature of the infrared heater was prevented from reaching up to values that could damage the product. During the analysis, the surface temperature of the timbers was kept at an average of 65 degrees C, while the bottom temperature was kept at an average of 45 degrees C. The air collector used in the system was found to be 50% efficient. At the end of a 13-h drying period, the moisture content of pine timbers could be reduced from 1.42 to 0.0948 g water/g dry matter. During the system analysis, parameters such as moisture content, mass diffusion coefficient, and useful energy rate were taken into consideration. (c) 2017 American Institute of Chemical Engineers Environ Prog, 36: 1875-1881, 2017 Scientific Research Projects Coordination Unit of Karabuk UniversityKarabuk University [KBU-BAP-16/1-BM-007] This work was supported by Scientific Research Projects Coordination Unit of Karabuk University (Project Number: KBU-BAP-16/1-BM-007).

Gurel, Ali Etem/0000-0003-1430-8041 WOS: 000335877200012 The efficiency of photovoltaic modules decreases with heating, so there has been an increase with regard to the solution of the problem. Photovoltaic module converts the incoming solar radiation into heat and electric energy. Due to this heating feature of photovoltaic modules, it is likely to produce heat energy from PV modules as well. Such systems are called as both a photovoltaic and thermal systems in the literature. A lot of experimental studies were done by special processing on the PV module. Since the studies require special processing on the module, they remain as laboratory work only. In this study, different PV/T systems were experimentally analyzed for the cooling photovoltaic modules. A simple pipe was placed on PV module as a spiral heat exchanger in order to provide active cooling. Also, the system can easily be applied to large-scale systems. As a result of experimental research, the module efficiencies with cooling were calculated as 13%, and the module efficiencies without cooling were about 10%. As the set temperature increased, module temperature can be increased or decreased. The module temperature was changed according to solar radiation and set temperature. As the solar radiation increased the module temperature decreased in this experimental system. The solar radiation has nothing to do with set temperature for this system. (C) 2014 Elsevier B.V. All rights reserved.

ÖzetBina dış duvarlarında yapılacak ısı yalıtım uygulamaları, yakıt tüketimini düşürerek enerji tasarrufu sağlamanın yanında, fosil kaynaklı yakıt kullanımından kaynaklanan ve hava kirliliğine neden olan emisyonların düşürülmesinde de son derece etkilidir. Bu çalışmada Karabük’te kömür ve doğalgaz kullanımında dış duvar optimum yalıtım kalınlığı tespitinin ekonomik ve çevresel analizi yapılmıştır. Çalışmanın ekonomik boyutu, yaşam döngüsü maliyet analizine (LCCA) dayanan P1-P2 yöntemi ile gerçekleştirilmiştir. Çalışmanın sonuçları, yakıt olarak kömür kullanıldığında optimum yalıtım kalınlığı ve enerji tasarrufunun sırasıyla 0.134 m ve 117.14 TL/m² olduğunu göstermiştir. Yakıt olarak doğalgaz kullanımında ise bu değerler sırasıyla 0.116 m ve 88.39 TL/m² olarak bulunmuştur. Optimum yalıtım kalınlığının hava kirliliğine olan etkileri incelendiğinde, yalıtımsız bina dış duvarında hesaplanan CO2 ve SO2 emisyonlarının yakıt tipine bağlı olarak optimum yalıtım kalınlığı noktasında %85.4’e kadar azaldığı hesaplanmıştır.AbstractHeat insulation applications carried out on external walls of building provides energy saving by decreasing fuel consumption and also quite important in decreasing emission which results from fossil-based fuel usage and causes air pollution. In this study, economic and environmental analyses were done for determination of external wall optimum thickness in using coal and natural gas usage in Karabük. Economic extent of the study was done with P1-P2 method which is based on life cycle cost analysis (LCCA). The results show that optimum insulation thickness and energy saving are 0.134 m and 117.14 TL/m² respectively when coal is used as a fuel. These values are 0.116 m and 88.39 TL/m² when natural gas is used as fuel. When the effects of optimum insulation thickness on air pollution are observed, CO2 and SO2 emissions calculated on external wall of uninsulated building decreased up to 85.4% at the point of optimum insulation thickness according to fuel type.

Gurel, Ali Etem/0000-0003-1430-8041 WOS: 000317851600027 In this study, optimum insulation thicknesses, energy savings, and payback periods have been investigated based on life-cycle cost analysis for an external wall in four various cities from four climate zones of Turkey. Also, the study have been analyzed the effect of insulation thickness on release of CO2 and SO2 emissions. The results show that insulation thicknesses vary between 0.045 and 0.195 m, life-cycle energy savings between 13.26 and 248.9 $/m2, payback periods between 1.19 and 1.97 years when used extruded polystyrene as insulation material. When the optimum insulation thickness was used, emissions were reduced by 6292% depending on the city, fuel type, and insulation material. (c) 2012 American Institute of Chemical Engineers Environ Prog, 32: 365-372, 2013

Gurel, Ali Etem/0000-0003-1430-8041 WOS: 000373866800020 The purpose of the present study is PV/T system, which designed and implemented in order to reuse of thermal energy while increasing of electric production. Solar radiation was increased with the concentrator about two folds and electrical power gains were increased. A paraffin wax was used to store latent heat as a thermal energy storage. Thermal energy was combined with a greenhouse like air drier and used to dry the product. Thermal and electrical energy gain in the concentrated and non-concentrated panels were compared and total system efficiency was analyzed. The maximum temperature obtained at the back of the panel was calculated as 37 degrees C and the panel efficiency was 11% at mean solar radiation was 2000 W/m(2). (C) 2016 Elsevier Ltd. All rights reserved.

Gurel, Ali Etem/0000-0003-1430-8041 WOS: 000364808500004 The aim of the current study was to investigate how to use hot water obtained by parabolic trough collector (PTC) in an air handling unit. The system consisted of a PTC, a water depot, a pump, an air handling unit, a fan, and control equipments. The purpose of the system was to maintain the set value without using an additional heater in the air handling unit. During the process, +/- 0.36 degrees C accuracy was achieved in a 40 degrees C set temperature. Uncertainty analyses were made for the measured temperature value and they were obtained as +/- 0.44 degrees C. The energy and exergy efficiency were calculated for the system. The heating performance coefficient (HPC) was defined as the ratio of the obtained energy from the system to the compulsory energy supplied to the system. The HPC was calculated as 3 on average. Heat energy of the water in the depot was converted to heat energy of the air in the system with an average 52 % exergy efficiency. Karabuk University Scientific Research Projects UnitKarabuk University The authors are grateful for the support of the Karabuk University Scientific Research Projects Unit.

Artificial neural network (ANN) is a useful tool that using estimates behavior of the most of engineering applications. In the present study, ANN model has been used to estimate the temperature, efficiency and power of the Photovoltaic module according to outlet air temperature and solar radiation. An experimental system consisted photovoltaic module, heating and cooling sub systems, proportional integral derivative (PID) control unit was designed and built. Tests were realized at the outdoors for the constant ambient air temperatures of photovoltaic module. To preserve ambient air temperature at the determined constant values as 10, 20, 30 and 40 °C, cooling and heating subsystems which connected PID control unit were used in the test apparatus. Ambient air temperature, solar radiation, back surface of the photovoltaic module temperature was measured in the experiments. Obtained data were used to estimate the photovoltaic module temperature, efficiency and power with using ANN approach for all 7 region of the Turkey. The study dealing with this paper not only will beneficial for the limited region but also in all region of Turkey which will be thought established of photovoltaic panels by the manufacturer, researchers and etc. © 2014 Elsevier B.V. All rights reserved., Firat University Scientific Research Projects Management Unit: KBÜ-BAP-13/2-YL-037, The authors would like to thank the Karabük University Scientific Research Projects Unit, Karabük/TURKEY for providing the financial supports for this study under the KBÜ-BAP-13/2-YL-037 project.

A closed-type water source heat pump dryer integrated with a drying programme (DP) was designed and tested. The DP was developed using psychometric conditions of desired drying air and thermodynamic balance of heat pump. A drying algorithm was developed according to the technical specification of the dryer. Drying air temperature, relative humidity and drying air volumetric flow rate were entered from a programmable logic controller (PLC) screen. In this study, the drying of mint leaves was examined. Mint leaves were dried at different temperatures (35°C, 40°C and 45°C) and at different volumetric flow rates 300 m3/h for a velocity of 0.75 m/s and 600 m3/h for a velocity of 1.5 m/s in the PLC-controlled heat pump dryer. The relative humidity of the drying air entering the dryer chamber was kept between 13.88% and 6.81% and the two air dampers were controlled according to predetermined value. The coefficient of performance ($$\rm CO{\rm P_{{\rm{hp}}}}$$) values obtained were between 3.81 and 2.29. The specific moisture extraction rate for the whole system ($$\rm SME{\rm R_{{\rm{ws}}}}$$) was between the 0.034 and 0.044 kg/kWh. The drying air temperatures were controlled with an accuracy of ±0.41°C to ±0.76°C depending on the mode of operation.