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Experimental and numerical analysis of the splay impact on the performance of splayed cross-cut fin heat sink
(Elsevier France-Editions Scientifiques Medicales Elsevier, 2021) Şevik, Seyfi; Özdilli, Özgür
In this study, splayed effects on the thermal performance of standard cross-cut heat sink (S-CCHS), fixed-array splayed (FAS-CCHS), and full splayed (FS-CCHS) under natural and forced conditions are studied experimentally and numerically. For this purpose, variable parameters such as splayed ratio, different powers of LEDs, natural and forced conditions, and blowing direction have been studied. The results showed that the thermal performance is significantly impacted by the spread position of the fins, blowing direction, natural and forced conditions of the CCHS but is not very sensitive to LEDs' powers. The results show that the full splayed heat sink occupies the highest physical volume, thus, provides the highest thermal performance by efficiently dissipating heat compared to other heat sinks designs. Experimental and numerical results show that the full splayed effect provides 5.46% and 2.59% lower junction temperature in natural and forced, respectively. Also, FS-CCHS achieved a 7.09% reduction in thermal resistance at natural convection 3 W and a 2.62% reduction at 10 W, respectively, compared to the flat fins and the fixed array wide fin heat sink. For this study, while the most suitable flow direction was determined as push, the most suitable orientation was found to be upward, and the splayed impact was also beneficial.
Thermal performance analysis of a novel linear LED housing with inner and outer fins
(Pergamon-Elsevier Science Ltd, 2020) Şevik, Seyfi; Abuşka, Mesut; Özdilli, Özgür
There is an inverse relationship between the junction temperature of the light-emitting diode (LED) and its lifetime therefore, it is significant to operate it at low junction temperature. In this study, three different natural convection linear housing models were developed to cool mid-powered LED arrays, focusing on basic parameters such as fin structure, surface area, and wall thickness in the design of the models and thermal performance has been tested numerically and experimentally. The performance tests were carried out at five different ambient temperatures, 20, 25, 30, 35, and 40 degrees C. Compared to Model-1 (standard housing without fin) and Model-2 (thin housing with inner fin), the cooling effect of Model-3 (thin housing with inner + outer fin) is remarkably high, and this effect was more evident with the increase in ambient temperature. This impact has been achieved by increasing the surface area of Model-3 by almost 50%, although its mass has decreased more than twice. The maximum junction temperatures of Model-3 were approximately 2 degrees C lower than Model-1 and 5 degrees C lower than Model-2 in all experiments, with the presence of fins and the development of geometry. When the maximum allowable temperature rise is 94.68-101.25 degrees C and the 35 watts dissipated in the package, the average thermal resistances were found to be 1.12-1.38 degrees C/W. It is thought that these new-generation LED-based linear designs can be used to illuminate the work areas and they can replace compact lamp-based luminaires that work with direct and indirect lighting principles.
Ankara ve ilçeleri için Güneş kolektörü optimum eğim açısının belirlenmesi
(Bursa Uludağ Üniversitesi, 2016) Koçer, Abdülkadir; Şevik, Seyfi; Güngör, Afşin
Öz: Ankara merkez ve ilçeleri bazlı olan bu çalışma, güneş kolektörü ve güneş paneli performanslarını en üst düzeye çıkarmak için optimum eğim açısının belirlenmesi ile ilgilidir. Ankara ilinde sabit güneş kolektörleri genellikle yaklaşık 40? eğim açısında yerleştirilmektedir. Bu çalışmada, Ankara il ve ilçeleri için yıllık optimum eğim açısı 34°?1 olarak hesaplanmış buna karşın yıl içerisindeki optimum eğim açılarının 1-67° arasında değiştiği hesaplanmıştır. Bu çalışmanın sonuçları literatürdeki benzer çalışmalar ile karşılaştırıldığında bu çalışmaların sonuçları ile uyumlu olduğu görülmüştür. Ayrıca, altı aylık periyotlar için 15? ve 56?, mevsimlik (kış, ilkbahar, yaz, sonbahar) periyotlar için ise sırasıyla 62?, 23?, 6? ve 49? olarak hesaplanmıştır ve optimum eğim açıları için güneş ışınım değerleri bulunmuştur. Sadece yılda iki kez eğim açısı değiştirildiğinde birim alana düşen enerji miktarı arttırıldığından yıllık eğim açısı sabit olanlara göre yaklaşık % 5 verim artışı sağlar. Diğer taraftan eğim açısı her ay değiştirildiğinde ise bu oran yaklaşık % 8’e ulaşabilir. Güneş kolektörleri ve panellerin kullanım verimliliğini arttırmak için, eğim açısını ayda bir kez veya yılda en az iki kez ayarlanması tavsiye edilir.
İl bazında enerji dengesi analizi: Karabük örneği
(Gazi Üniversitesi, 2017) Şevik, Seyfi
Bu çalışmanın amacı; Karabük ilinin enerji arz-talep dengesini ortaya koymak, bu denge içerisinde kahverengi ve yeşil enerjilerin payını ve bunların genel eğilimini değerlendirmek ve bir enerji akış şeması oluşturmaktır. Karabük ilinde, kurulu gücü 122 MW olan 4 adet lisanslı ve 1 adet lisanssız olmak üzere toplamda 5 adet aktif elektrik enerji santrali ile yıllık yaklaşık 530 GWh elektrik üretimi yapılmaktadır. Bu üretim ile, kendi elektrik tüketiminin % 45'i karşılanabilmektedir. Karabük ili elektrik kurulu gücünün Türkiye kurulu gücüne oranı % 0.17 iken Türkiye tüketimine oranı % 0.21'dir. Yenilenebilir enerjinin toplam kurulu güç içerisindeki payı % 58.8 iken toplam enerji üretimi içerisindeki payı ise % 32'dir. Karabük, yeterli enerji kaynaklarına sahip olmayıp bununla birlikte, fosil yakıt tüketimi de oldukça yüksektir. Karabük, yerli olmayan enerji kaynaklarının ağır bir sömürüsü ile karşı karşıyadır. Yenilenebilir enerji ve etkili enerji verimliliği programları, yerli olmayan enerji kaynakları üzerindeki ülkenin bağımlılığını azaltabilir
Analysis of drying of melon in a solar-heat recovery assisted infrared dryer
(Elsevier Ltd, 2016) Aktaş, Mustafa; Şevik, Seyfi; Amini, Ali; Khanlari, Ataollah
Infrared drying systems are popular in terms of high heat and mass transfer. By using an infrared dryer, it is possible to catch fast heating and short drying time in comparison to the other drying methods. But it consumes a high amount of energy. Therefore, a new type solar air collector (SAC) and air to air heat recovery unit were added to the infrared dryer to reduce specific energy consumption. The general aim of this study is to analyze heat and mass transfer characteristics of the dryer and three-dimensional (3-D) computational fluid dynamic (CFD) simulation and to investigate drying kinetics of melon slices. Experiments were performed at 50 °C and 60 °C melon’s surface temperature and 0.5 m/s air velocity. Melon slices were dried from 9 g water/g dry matter to 0.044 g water/g dry matter moisture content. The effective moisture diffusivity (De) values varied from 8.25 × 10?10 to 1.24 × 10?9 m2/s. The average mass transfer coefficient (hm) values increase from 8.53 × 10?8 m/s at 50 °C to 1.47 × 10?7 m/s at 60 °C. Heat recovery unit has a key role in this system and it provides 23–28% of total input energy. Average solar air collector efficiency was calculated as 50.6%. Obtained theoretical and experimental results are in line with each other. This study shows the successful and efficient combination of solar energy, infrared energy and heat recovery in food processing.
Energy, exergy, economic and environmental (4E) analyses of flat-plate and V-groove solar air collectors based on aluminium and copper
(Elsevier Ltd, 2017) Abuşka, Mesut; Şevik, Seyfi
An experimental investigation has been carried out to study the effect of energy, economic, and environment of SACs which are smooth and roughened by v-groove protrusions arranged made of copper and aluminium materials. In this context; energy, exergy, economic, and environment (4E) analyses are investigated using data obtained from experimental studies at air mass flow rates of 0.04, 0.06, 0.08 and 0.1 kg/s. Thermal, economic, and environmental impacts for performance enhancement of the SACs have been determined. It reveals that the average thermal and exergy efficiencies of the SACs, for the installed region of collectors, were 43–60% and 6–12%, respectively. Among all others with copper v-groove showed that the highest heat transfer enhancements with friction factors high than those of flat, thermal performance of copper v-groove are among the highest of the SACs tested in this study. The payback period was found to be between average 4.3 and 4.6 years when calculated on a yearly basis, which was significantly less than estimated lifetime of the system. The enviro-economic cost values were obtained between 4.5 and 5.77 $/year. Consequently, the results show that the v-groove collectors to be preferable due to their performance despite the price disadvantage. The v-groove SACs, although slightly higher friction factors and cost, produce much higher heat transfer coefficients compared with flat SACs. © 2017 Elsevier Ltd
Experimental performance analysis of sensible heat storage in solar air collector with cherry pits/powder under the natural convection
(Elsevier Ltd, 2020) Abuşka, Mesut; Şevik, Seyfi; Kayapunar, Arif
It is important to enhance the availability of SACs either in cloudy weather or after sunset for space heating and agricultural drying process. In this context, this study aims to determine experimentally thermal performance of cherry pits as sensible heat storage material under natural convection conditions. In the first collector (Type I), powdered cherry pits (32 kg) were used as heat storage material and cherry pits (24 kg) were used in the second (Type II). The third collector (Type III) with a flat absorber plate is for comparison. Although the maximum thermal efficiencies were found 26.54% and 27.03% for Type I and Type II respectively, average thermal efficiency of Type I is higher than Type II. According to the test results, the inlet-outlet temperatures were equalized 46 min for the Type III, 200 min for Type II, and 270 min for Type I collector after sunset. As a result, it can be said that the use of cherry pits and powder as sensible heat storage material is promising. © 2018 Elsevier Ltd
Performance analysis of solar and solar-infrared dryer of mint and apple slices using energy-exergy methodology
(Elsevier Ltd, 2019) Şevik, Seyfi; Aktaş, Mustafa; Dolgun, Ekin Can; Arslan, Erhan; Tuncer, Azim Doğuş
In this study, double-pass solar air dryer (DPSAD) and infrared assisted double-pass solar air dryer (DPSAIRD) were designed and tested. The effects of using infrared energy have been experimentally investigated to ensure continuity in climatic conditions (cloudy, etc.) where solar energy is insufficient. Comparative experiments were carried out in the summer and autumn. Energy and exergy analysis, mass and heat transfer, performance coefficient, specific energy consumption, drying efficiency, energy efficiency and error bars have been used as criteria for evaluating thermal and structural performance of solar dryer and to see the effects of infrared energy on dried products (apple slices and mint leaves). The highest thermal efficiency of the collector was obtained as 83.56%. For DPSAIRD and DPSAD, exergy efficiency values were calculated as 49.17%, 59.07%, 59.06% and 69.35%, respectively. Energy efficiencies varied between 1.15% and 8.59% for DPSAIRD, 2.20% and 26.46% for DPSAD. Despite the low radiation values in autumn and the lower ambient temperature, it was found that the drying times are almost the same as in the summer months, thanks to the use of infrared energy. The IR lamp significantly increased energy consumption; however, in cases where the collector was insufficient, it supported both the collector and protected the products against deterioration. © 2019
The effect of blowing direction on heat sink performance by thermal imaging
(Yildiz Technical University, 2018) Abuşka, Mesut; Şevik, Seyfi; Altıntaş, Volkan
Heat sinks (HSs) are designed for the mechanical, electrical and electronic components that generate heat in considerable amount. For this purpose, an aluminum conical pin fin heat sink is designed. Aluminum conical pin-fins geometry has been experimentally investigated for the blowing direction (pushing or pulling) which is the energy efficient option for the heat sink. The heat sink was tested at the same fan power for pushing and pulling conditions for 25, 50, 75 and 100 W resistance heater power. Designed aluminum conical pin fin heat sink can be easily used in heat sweeping processes. It has found that pushing configuration of the fan is more efficient for this design. © 2018 Yildiz Technical University.
Thermal performance of flexible air duct using a new absorber construction in a solar air collector
(Elsevier Ltd, 2019) Şevik, Seyfi; Abuşka, Mesut
This paper presents the comparative experimental energy and exergy analysis of a solar air collector (SAC) with flexible aluminum foil duct and conventional flat plate SAC, with and without glazing. Effect on performance enhancement of the aluminum foil duct has been determined at air mass flow rates of 0.013, 0.03 and 0.044 kg/s. It reveals that the average energy and exergy efficiency of the flexible duct SAC were 81.3% and 25% at glazed experiments for 0.044 kg/s, respectively. The experimental results with and without glass demonstrated that designed collector has 15.9–41.2% higher efficiency than the flat collector and the designed collector to be preferable due to its performance and cost advantage for sustainable competitiveness. As expected, the performance of the SAC with glazing is better than those of the unglazed collector. The new application of flexible air duct as an absorber plate can be used as an energy and cost-efficient option for SACs. Moreover, the results showed that the higher thermal efficiency of SAC mainly depends on glazing, absorber structure, and the circulation time of the air. © 2018 Elsevier Ltd
A comparative investigation of the effect of honeycomb core on the latent heat storage with PCM in solar air heater
(Elsevier Ltd, 2019) Abuşka, Mesut; Şevik, Seyfi; Kayapunar, Arif
The aims of this study were to comparatively investigate the effect of using PCM and honeycomb as the internal fin structure in the PCM panel on the thermal performance of solar air heater. The tests performed at six air mass flow rates from 0.008 to 0.048 kg/s. The heat storage material was tested in two forms, PCM with honeycomb core in the first heater (Type I) and only PCM in the second heater (Type II). The third heater (Type III) with a flat absorber plate (without PCM) was used for comparison. The average day-time thermal efficiency of the Type I-II heaters with PCM increased from 8.4% to 9.0% for the mass flow rates of 0.032, 0.04, and 0.048 kg/s, while from 0.8% to 8.0% decreased for the mass flow rates of 0.008, 0.016 and 0.024 kg/s. The use of honeycomb as the internal fin structure significantly reduces the charge-discharge time, while slightly reducing the instantaneous-daily thermal efficiency, and provides a temperature increase of up to 8.8 °C at the PCM-temperature. The daily thermal efficiency comparison between heaters with PCM was in favor of the heater without honeycomb at values ranging from 0.1% to 4.4%. Taking into consideration the daily thermal efficiency, the Type I-II heaters with PCM are more efficient between from 2.6 to 22.3%, especially at high mass flow rates. It took approximately one hour to equal the outlet air temperature of the Type-III with the inlet air temperature. In PCM heaters, the inlet-outlet temperatures are approximately equal to 6 to 10 h. © 2018 Elsevier Ltd
Experimental analysis of solar air collector with PCM-honeycomb combination under the natural convection
(Elsevier B.V., 2019) Abuşka, Mesut; Şevik, Seyfi; Kayapunar, Arif
Phase change material (PCM) is at the head of materials commonly used in latent heat storage. However, usually the main problem is that the heat conductivity of PCMs is low. Therefore, a novel solar air collector (SAC) combined the PCM-Rubitherm RT54HC with aluminum honeycomb was manufactured and investigated the effect of using honeycomb core on the collector thermal performance regarding heat storage with PCM under natural convection conditions. In the experiments, the heat storage material was tested in two forms with 26 kg capacity, PCM with honeycomb core in the first collector (type I) and only PCM in the second collector (type II), and also the third collector (type III) with a flat absorber plate for comparison. The first collector reached the PCM melting point about 50 min ago. Also, when we consider the peak point, an apparent 10 °C advantage is achieved in sensible heat storage in favor of type I. It is observed that the honeycomb core used as a heat transfer enhancer is effective in shortening the charge-discharge times, also a noticeable difference in sensible heat storage during the noon. The production of useful energy in Type I lasted 469 min and 539 min longer than type III, respectively. The thermal efficiencies under daylight were calculated as 10.1%, 10.9% and 13.6%, respectively. As a result, it can be said that the use of honeycomb core as heat conductivity enhancer material is very functional, in particular during the discharge period. © 2019 Elsevier B.V.
Heat pump drying of grape pomace: Performance and product quality analysis
(Taylor and Francis Inc., 2019) Aktaş, Mustafa; Taşeri, Levent; Şevik, Seyfi; Gülcü, Mehmet; Uysal Seçkin, Gamze; Dolgun, Ekin Can
Grape is one of the most popular fruits and various types of grape have been cultivated by more than 100 countries around the World. The wine and juice industry produces large quantities of by-product, called grape pomace (GP) as an industrial waste and it consists of skins, seeds, and stems. Various processes such as separation, pressing, drying, and milling are applied to benefit from its health effects. In this study, the seeded black GP Kalecik karası (Vitis vinifera) was dried in an assisted closed cycle heat pump dryer (HPD) designed for high-moisture products to investigate the drying behaviors of GP. The effects of drying air temperature on bioactive properties and the drying characteristics of GP, and performance of system have discussed. Experiments were carried out at two different temperatures (45 and 50°C) and air velocity of 1.0 m/s. It was seen that increasing temperature decreased the drying time, coefficient of performance of whole system (COPws), and specific energy consumption (SEC). The average values of COPws for temperatures 45°C and 50°C were calculated as 3.28 and 3.10, respectively. The drying efficiencies (DE) at drying air temperature of 45°C and 50°C ranged from 2 to 12% and from 2 to 15%, respectively. Additionally, result of analysis has indicated that using a HPD at lower temperatures increases performance of system despite of higher energy input. Bioactive properties of dried samples at drying air temperature of 45°C are better than 50°C. The results show that drying the GP at low temperature is more suitable for product quality. For this reason, heat pump may be preferred. It shows that this drying system with higher capacities in the future can be recommended as an alternative technique in terms of energy usage, drying time, and performance of system. © 2018, © 2018 Taylor & Francis Group, LLC.
Drying of grape pomace with a double pass solar collector
(Taylor and Francis Inc., 2019) Aktaş, Mustafa; Şevik, Seyfi; Dolgun, Ekin Can; Demirci, Burhan
This study aims to analyze the performance of a novel design of the double pass solar air collector (DPSAC)-assisted drying system and investigate the drying kinetics of grape pomace which is an agricultural by-product. The samples were dried to a moisture content of 0.01 g water/g dry matter between 100 and 250 min depending on the weather conditions. The average thermal efficiencies of DPSAC were calculated as 79.77, 79.85, and 69.46%. Average values of the coefficient of performance of DPSAC were determined as 5.32, 5.13, and 4.32. The highest specific moisture extraction rate value was achieved as 617.18 g water/kWh. Whereas the mass transfer coefficient (h m ) values ranged from 9.15E?11 to 1.04E?7 m/s, the effective moisture diffusivity (D e ) values were obtained between 3.04E?13 and 1.02E?10 m 2 /s. The qualitative analysis showed that the drying using DPSAC may be an alternative for drying applications in terms of short drying time and energy usage. Nevertheless, these results clearly suggest a complex and effective interplay between thermal performance and drying kinetics. © 2018, © 2018 Taylor & Francis.
Modeling of a convective-infrared kiwifruit drying process
(Elsevier Ltd, 2017) Özdemir, M. Bahadır; Aktaş, Mustafa; Şevik, Seyfi; Khanlari, Ataollah
This paper aims to evaluate the experimental performance of a convective-infrared system with heat recovery (CIRHR) at different drying temperatures (40, 45, 50 and 55 °C) and 0.5 m/s air velocity and also to discuss and predict the performance of system on energy consumption and drying kinetics of sliced kiwifruit using artificial neural networks (ANNs). The energy efficiency values were obtained between 2.85% and 32.17%. The ANN model was used to predict the energy consumption of the system and moisture content of the kiwifruit. The back-propagation learning algorithm with Levenberg–Marquardt (LM) and Fermi transfer function were used in the network. The coefficient of determination (R2), the root means square error (RMSE) and the mean absolute percentage error (MAPE) were calculated as 0.99, 0.001 and 0.34, respectively. It can be concluded that predicted values are in good agreement with experimental results. © 2017 Hydrogen Energy Publications LLC
Determination of drying kinetics and quality parameters of grape pomace dried with a heat pump dryer
(Elsevier Ltd, 2018) Taşeri, Levent; Aktaş, Mustafa; Şevik, Seyfi; Gülcü, Mehmet; Uysal Seçkin, Gamze; Aktekeli, Burak
Pomace of Hamburg Muscat was dried at temperature of drying air 45 °C and different air velocity (1.5, 2.0 and 2.5 m/s) in open-loop heat pump (HP) and laboratory-type closed-loop dryer (as a control). In the HP dryer, it was concluded that drying air velocity was slightly effective on drying time however there is no significant effect on the power consumption of the change in the drying air velocity at the same temperature. When comparing the energy consumption of the HP dryer and convective dryer, the energy consumption was reduced by up to 51%. In HP drying, the increase of air velocity from 1.5 m/s to 2.5 m/s caused a reduction in drying time by 69%. It was observed that part of the bioactive properties was lost in pomace samples but there were fewer losses in all bioactive properties than the others except the total anthocyanin at 2 m/s. © 2018 Elsevier Ltd
Development of heat pump and infrared-convective dryer and performance analysis for stale bread drying
(Elsevier Ltd, 2016) Aktaş, Mustafa; Şevik, Seyfi; Aktekeli, Burak
This experimental study aims to develop a heat pump dryer (HPD) and an infrared dryer (IRD) also the comparative empirical analyses of these two methods and to analyze the drying kinetic of stale bread sliced 15 mm thickness and effectiveness on the drying kinetics of the stale bread of dryers. Dryers have been developed by using different techniques such as heat recovery unit, proportional control (PC) of drying air temperature, simultaneous control of the relative humidity-temperature-air flow rate, water cycle dehumidifier and closed-loop cycle to increase the drying efficiency of industrial drying applications. The highest coefficient of performance of the whole heat pump system (COPws,HP) was calculated as 3.7 and drying efficiencies of the IRD and HPD systems were calculated as 39% and 25%, respectively. When the HPD and IRD systems were compared in terms of drying time and energy consumption, it was observed that the IRD system did not only shortened the drying time up to 69%, but also decreased the energy consumption of the system by 43.2%. Based on the obtained results the effective moisture diffusivity (De) was calculated in the range from 8.3 × 10-8 to 3.2 × 10-7 m2/s and mass transfer coefficient (hm) was varied from 1.17 × 10-5 to 4.52 × 10-5 m/s. It was concluded that both dryers have significant effect in reduction of water content; the relative humidity controlled HPD can be applied efficiently for dryers and the dried stale bread can be reused as bread crumb by food industry. © 2016 Elsevier Ltd. All rights reserved.
Performance analysis of heat pump and infrared–heat pump drying of grated carrot using energy-exergy methodology
(Elsevier Ltd, 2017) Aktaş, Mustafa; Khanlari, Ataollah; Amini, Ali; Şevik, Seyfi
In this study, a hybrid drying system that combines all of the advantages of different drying methods was developed. This study aims to compare experimental results of a heat pump dryer (HPD) and an infrared assisted heat pump dryer (IRAHPD), to determine the energy and exergy efficiency of dryers and to analyze the drying kinetic of grated carrot for observing the effectiveness of the dryers. Samples were dried at 45 °C and 50 °C set temperatures and 0.5 m/s air velocity. According to dry basis calculation, initial moisture content amount was 7.06 g water/g dry matter and amount of final moisture content of dry matter was obtained as 0.14 g water/g dry matter. Energy efficiency varied between 5.3% and 50%. Minimum and maximum coefficients of performance for the whole system (COPws) were 2.11 and 2.96 respectively. Maximum exergy efficiency was obtained 66.8% while minimum exergy efficiency was 31.6%. It was concluded that during the time to reach a stable state of system, the exergy efficiency increased in response to exergy loss decreases. This study shows a successful and efficient combination of heat pump and infrared heater in food drying. © 2016 Elsevier Ltd

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