MCBÜ Açıkerişim Sistemi :: Browsing by Author "Abuska, M"

Browsing by Author "Abuska, M"

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Energy, exergy, economic and environmental (4E) analyses of flat-plate and V-groove solar air collectors based on aluminium and copper
Abuska, M; Sevik, S
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.
A comparative experimental performance evaluation of solar air collector having absorber plate with convex oval-trench dimple
Abuska, M; Sevik, S; Özdilli, Ö
The purpose of this research is to examine how convex oval-trench dimples placed staggered on a solar air collector's absorber improved vortex heat transfer. At air mass flow rates of 0.013, 0.027, and 0.036 kg/s, convex oval-trench dimple absorbers with relative roughness heights, e/D=0.2 and e/D=0.4, as well as a flat plate absorber, were evaluated for back-pass and front-pass applications. The oval-trench dimpled absorber plates in the back-pass and front-pass achieved the maximum energy efficiency of 37.5% and 50.6%, respectively, with e/D=0.4 and 0.036 kg/s. The increase in the number of Nu in e/D=0.4 was 26% and 31% more than that of the flat plate for the examined parameter ranges of back-pass and front-pass, respectively. (e/D=0.4)/(flat plate) and (e/D=0.4)/(e/D=0.2) increased by an average of 28% and 24% in back-pass for (Nu(otd) /Nu(0))/(f(otd) /f(0)), respectively. In front-pass, (e/D=0.4)/(flat plate) and (e/D=0.4)/(e/D=0.2) improved by 35% and 25%, respectively. The collector with a relative roughness height of 0.4 has the optimal structure for this examination of collectors with an oval-trench dimple. The results indicated that collectors with convex oval-trench dimples outperform flat plates in terms of surface area expansion and turbulence generation, which boosts thermal efficiency substantially. In addition, when the experiment results were compared, the front-pass implementation outperformed the back-pass approach. As a result, thermal systems may benefit from utilizing the convex oval-trench dimple.
Comparative energy and exergy performance investigation of forced convection solar air collectors with cherry stone powder
Abuska, M; Sevik, S; Kayapunar, A
The purpose of this study is to design new solar air collectors (SACs), to ensure that designed SACs continue to operate in cloudy weather and after sunset and to evaluate in terms of energy and exergy whether the cherry stone/powder will be appropriate to use as a sensible thermal energy storage (STES) material. The experiments were performed for a powdered cherry stones SAC (Type I), a cherry stones SAC (Type II), and a flat plate SAC (Type III) at seven different air mass flow rates (from 0.004 kg/s to 0.048 kg/s). Average thermal efficiency fluctuated between 6.05% and 39.99%, depending on the air mass flow rates under which the experiments were performed and whether the collectors have heat storage. The maximum difference in daily collector efficiency is in Type II, with a slight difference from Type I, which was 18.7% higher than the Type III. The inlet -outlet air temperatures of Type I and Type II were equaled 5 and 4 h after sunset, respectively, compared to the flat plate collector. The exergy efficiency ranged from 1% to 7% during the charging period. As a result, it can be seen that the use of cherry stone/ powder as a STES material is promising in contributing to the collector sustainability. (C) 2019 Elsevier Ltd. All rights reserved.
Experimental and numerical investigation of thermal performance in solar air heater with conical surface
Abuska, M; Kayapunar, A
The absorber plate surface modifications of a solar air heater (SAH) increase the convective heat transfer rate of the inlet air. Forced convection heat transfer of air in a SAH with a staggered arrangement of conical obstacles has been carried out experimentally and numerically at mass flow rates (0.04, 0.08, and 0.1 kg/s) under ambient conditions for the aim of to enhance the thermal efficiency and to create proper volume for heat storage material in terms of the effectiveness of the SAH. The thermal efficiency for the absorber with conical obstacles was 14.0, 14.6, and 11.8% higher than the flat absorber plate for the mass flow rates, respectively. The results show that the number of Nusselt obtained in conical surface experiments was highest for all cases tested regardless of Reynolds number. The experimental results are compared with the numerical results obtained by the CFD method. The model results indicate good agreement with the experimental results. Also, the results show that the heat transfer in front of the conical elements is high, and the back is low; in the smooth absorber, a linear velocity distribution is seen along the channel; however, in the conical surface absorber, the velocity distribution due to turbulence is very variable.
Drying of Sultana seedless (Vitis vinifera L.) grape variety in indirect drying chamber using solar air collector with conic dimpled absorber: The case of end-season drying
Coban, H; Abuska, M
The main functions of mechanical drying are to extend the drying season, prevent reduction in dry product mass due to immature harvest, and obtain high-quality products without exposure to rainy weather conditions. A SAC with a conic dimpled absorber-assisted indirect solar dryer was designed, manufactured, and tested for the Sultana Seedless grapes under the end-season conditions. Also, the effect of medicinal chamomile oils on the color quality of raisins was investigated. While the first three days of the drying experiment were reminiscent of summer, the remaining days were characteristic of autumn. The thermal efficiency of the collector at a flow rate of 0.05 kg/s was realized as 66.33 % and 48.27 % on average during the days (between hours of 10:00-15:00), depending on the psychrometric conditions. The moisture content of the grapes (22.5 brix) decreased from 3.37 to 0.22 kgw/kgsm and lasted for 272 h/12 days. It has been revealed that the collector efficiency and drying time were significantly affected by the psychrometric conditions, and the use of medicinal chamomile oil in dipping pretreatment increased the color quality of raisins. Effective use of the SAC in the end-season drying process should be increased by techniques such as serial connection and heat storage.
Experimental investigation of relative roughness height effect in solar air collector with convex dimples
Sevik, S; Özdilli, Ö; Abuska, M
This study focuses on the effect of dimple depth on improving thermal performance in a solar air collector (SAC) with huge convex dimples placed staggered on an absorber. In this regard, convex dimple absorbers with two different types of relative roughness heights, 3/D = 0.16 and 3/D = 0.32, and a flat plate absorber were tested for back-pass and front-pass applications at air mass flow rates of 0.013, 0.027, and 0.036 kg/s. The highest average energy efficiency of 37.9% and 53.5% were achieved for dimpled absorber plates in back-pass and front-pass, respectively, with 3/D = 0.32 at an air mass flow rate of 0.036 kg/s. The exergy efficiency ranged from 8.1% to 12.4% for the back-pass application, whereas it fluctuated from 14.6 to 19.7 in the front-pass application. In comparing 3/D = 0.32 with the flat plate in the back-pass application, Nud/Nufvaried from 1.2 to 1.48 with an increase in Re, while in the front-pass Nud/Nuf changed from 1.13 to 1.37. In the back-pass, Nud/Nuf/(fd/ff) achieved 1.24 in favor of 3/D = 0.32 at Re = 4000, on the other hand, it reached 1.15 in the front-pass. Similarly, the highest Colburn factor values in all Re numbers were obtained in the case of relative roughness height of 3/D = 0.32. As a result, a relative roughness height equal to 0.32 is the optimal geometry for this investigation of a dimpled collector. Accordingly, the results showed that SACs with convex dimples are more successful than the flat plates, thanks to the surface area expansion and turbulence generating ability, which significantly increases the thermal efficiency. This study also recommends the use of a front-pass application. (c) 2022 Elsevier Ltd. All rights reserved.
Experimental and numerical investigation on the thermal performance of linear LED housings under forced convection
Abuska, M; Sevik, S; Özdilli, Ö
This study aims to experimentally and numerically test the thermal performances of three different linear housings (Model 1-without fin, Model 2-with inner fin, and Model 3-with inner and outer fin) with medium power light-emitting diode (LED) arrays at 30 degrees C and 40 degrees C ambient temperatures under forced convection for 25 W and 35 W. Although the mass of Model-3 was reduced by 54.2% and 34.67% compared to Model-1 and Model-2, its surface area was increased by 46.3% and 9.11%, resulting in an improvement in junction temperature (T-j) up to 4.4 degrees C and 7.75 degrees C, respectively. Thermal resistance (Rth) for Model-3 is approximately 1.38-3.1% and 7.85-9.72% smaller than that of Model-1 for 25 W at ambient air temperature (T-aa = 30 degrees C and T-aa = 40 degrees C), respectively. The Rth for Model-3 is approximately 1.39-2.6% and 8.65-6.07% smaller than that of Model-1 for 35 W at the same T-aa, respectively. The Model-3 offers lower junction temperature, lower cost, and safe operating temperature range by inner and outer fins compared to the others. The results demonstrated that all of the temperatures reduced with the increase in air mass flow rate; however, it was found that as the LED power and ambient temperature increased, the junction temperature increased. Experiment and simulation results show that adding a fan to the luminaire significantly lowers the LED junction temperature, in which case it provides a safe operating range and protects the luminaire against thermal shocks. The forced application allows using of comparatively smaller housing as it provides a lower junction temperature.
Thermal performance of flexible air duct using a new absorber construction in a solar air collector
Sevik, S; Abuska, M
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.
Enhancing the thermal performance of a solar air heater by using single-pass semi-flexible foil ducts
Sevik, S; Abuska, M
This study focused on improving the thermal performance of a solar air heater (SAH) using a single-pass semi-flexible foil duct that can be applied directly as an absorber without requiring any surface modification. In this regard, a series of tests were performed at the air mass flow rate of 0.013 kg/s, 0.03 kg/s, and natural convection to determine the effect of the new material on the performance of the heater, and results were compared to a heater with a flat plate absorber. The maximum and average thermal efficiency of the heater with single-pass semi-flexible ducts were found as 65.48% and 53.08% for 0.03 kg/s, respectively. The SAH with single-pass semi-flexible foil ducts provides an enhancement in the thermal efficiency of 18.82% compared to the heater with a flat absorber plate. The exergy efficiency ranged from 10% to 15% for the new design heater. The increase in the number of Nu in the new design heater was found 3.02 times higher than that of the flat plate heater for the studied parameter range. The heat transfer coefficient was augmented of 2.03 times in the single-pass semi-flexible duct. Accordingly, the results showed that the single-pass semi-flexible foil duct is more successful than the flat plate because it significantly increases thermal efficiency due to its unique curved inner surface structure and high surface area. However, it is recommended that the absorber be applied as multiple cycles to achieve higher efficiency and outlet air temperature.
Sun-infrared heating film drying analysis of Sultana seedless grapes: Operating modes
Çoban, H; Sevik, S; Abuska, M
In contrast to the technique of utilizing infrared heating films (IRHFs) as the main or auxiliary heating source in the dryer, this study investigated the quality and performance parameters of sun drying the Sultana seedless grapes (Vitis Vinifera L.) on IRHFs without using a dryer system. In this context, sun drying with four IRHF operating modes was analyzed: sun drying (Model-1), sun + daytime IRHF (Model-2), sun + 24 h IRHF (Model3), and sun + night IRHF (Model-4). Model 1 used no electricity, whereas the other models consumed 7.21, 10.38, and 9.80 kWh of electricity. The average drying efficiency of all drying models varied between 5.25 % and 16.48 %. Considering all experiments, average De values changed from 4.2837E-07 to 5.443E-07 m2/s. The drying times were significantly shortened (2-3 times faster) in Models 2 and 3, and the color quality was highest in Model 4. Moreover, grapes dried using sun + IRFH gave the best results regarding physicochemical and bioactive quality properties such as pH, total phenol, total tannin, vitamin C, and total sugar compared to Model1, which requires a long drying period. This study's findings indicate that sun drying with IRHF, which shortens drying time and offers higher quality in terms of color and food content, may be an alternative method that can be adapted to the traditional sun drying method.
THE EFFECT OF BLOWING DIRECTION ON HEAT SINK PERFORMANCE BY THERMAL IMAGING
Abuska, M; Sevik, S; Altintas, V
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.
Experimental Study on Thermal Performance of a Novel Solar Air Collector Having Conical Springs on Absorber Plate
Abuska, M; Akgül, MB
This study presents a thermal analysis for a novel type of solar air heater. The thermal performance of a solar air collector having conical springs on the absorber plate is determined experimentally. A flat absorber plate (Type I) and the absorber plate with mounted conical springs (Type II) are designed and constructed, and their thermal performance is tested in the collectors. Experiments are performed for air mass flow rates of 0.06 and 0.07 kg/s. Thermal efficiency and collector outlet temperature are the main indicator for determining thermal performance. The efficiencies and energy distribution ratios are determined and compared for the collectors. The results of the experiments show that a substantial enhancement in the thermal efficiency is obtained with conical springs. Also, to this thermal efficiency increases with the rise of mass flow rate.
Energy and exergy analysis of solar air heater having new design absorber plate with conical surface
Abuska, M
Solar air heater is used to heat air for space heating and drying process but it has low thermal efficiency because of low thermal conductivity between absorber plate and air. Artificial surface geometry is a very effective method for increasing the efficiency of air heaters. In this study, the thermal performance of a new design absorber plate with conical surface investigated and compared to flat absorber plate in single front pass conventional solar air heater. The experiments were performed for three mass flow rates of 0.04, 0.08, and 0.10 kg/s in outdoor conditions. The average thermal efficiency is obtained as 63.2-57.2% for 0.04, 71.5-61.7% for 0.08, and 74.6-64.0% for 0.1 kg/s in conical and flat absorber plate, respectively. The highest thermal efficiency was determined for the solar air heater with conical surface for all operating conditions. The average exergy efficiency is obtained as 19.3-16.1% for 0.04, 15.1-11.5% for 0.08, and 12.5-9.2% for 0.1 kg/s in conical and flat absorber plate, respectively. A significant increase in the thermal efficiency was obtained for conical absorber plate comparing with a flat one. The conical surface provides a smooth air flow above the absorber plate, increased surface area, and relatively less shading and decreasing the dead surface in the duct. The new design absorber plate with the conical surface can be as energy efficient option for SAHs. Moreover, the results showed that the efficiency of solar air heater mainly depends on mass flow rate, solar radiation, and surface structure of absorber plate. (C) 2017 Elsevier Ltd. All rights reserved.
A comparative experimental thermal performance analysis of conical pin fin heat sink with staggered and modified staggered layout under forced convection
Abuska, M; Corumlu, V
In contrast to the common practice of evaluating heat sinks with inline or standard staggered fin placement, this research investigated the thermo-hydraulic performance of conical pin-fin heat sinks with staggered-(CPFHSst) and modified staggered-(CPFHSmst) fin placements. The heat sinks with cross-cut pin-fins oriented parallel-(CCPFHSpar) and perpendicular-(CCPFHSperp) to the airflow and a flat heat sink (FHS) are also used for com-parison. The effect of heat sink fin placement on the parameters became remarkable with increasing Re, so the modified staggered fin placement was 2-7 degrees C lower than the staggered surface and junction temperatures. Rth of the modified model compared to the staggered was 5.3 %, 5.8 %, and 3.5 % lower, while the highest Delta P is in CCPFHSperp with 6.7, 6.9, and 7.4 Pa. CCPFHSperp provided a 29.9 % advantage of Nu to the modified model, whereas the modified model provided a 6.4 % over CCPFHSperp and a 17.4 % over the staggered model for the test powers. The modified model provides the highest THP performance, with a 13.3 % advantage over CCPFHSperp, 12 %, and 10.9 % over the staggered model for the test powers. The CPFHSmst is superior regarding thermo-hydraulic performance and is an appropriate option among many heat sink models in the literature.
Evaluation of prediction and modeling performance using machine learning methods for thermal parameters of heat sinks under forced convection: The case of external validation
Çorumlu, V; Altintas, V; Abuska, M
The capability of ML models in thermal systems is generally determined by internal validation, while this study investigates the prediction performance of ML models with external validation. ANN, XGBoost, and RF models were created with the training-test data set obtained from the results of flat, conical, and cross-cut pin fin heat sinks. Data of 33, 66, and 99 W for the training-test data set were used for training and internal validation, while data of 49.5 W for conic Model-I and 82.5 W for conic Model-II were used for external validation. The RF showed the highest performance on the test data-internal validation and the ANN on the external validation. According to the test data not used in training, the lowest MSE is 0.0270-(RF), 1.7437-(ANN), and 14.7140-(XGBoost). In RF and XGBoost, the external validation performance decreased significantly compared to the internal validation. The MSE of the models are 8.0683-ANN, 214.4047-XGBoost, and 300.6012-RF for external validation. The thermal resistance provides more realistic results than the Nusselt number for the thermal performance evaluation of heat sinks with ML methods. The ANN based on external validation may be used to predict heat sinks' thermal performance and save money, labor, and time compared to CFD simulations.
The Fuzzy Logic Modeling of Solar Air Heater Having Conical Springs Attached on the Absorber Plate
Abuska, M; Akgül, MB; Altintas, V
Solar air collectors (SAC) are usually used for space heating and drying of agricultural products. In SACs, thermal efficiency is low due to the low heat transfer between the absorber plate and fluid. In this study, a novel absorber plate geometry is designed and manufactured for enhancing the thermal efficiency. A comparative test system consisting of a flat absorber plate with staggered conical springs and a collector with flat absorber plate was established. It is aimed to increase the thermal efficiency by increasing the turbulence effect of the surface area, the interaction between the fluid and the absorber plate with the staggered conical springs. The performance of the systems was tested experimentally. In the experiments, inlet and outlet temperature of the collectors, global radiation, the exit velocity of air from the collectors, the absorber plate temperatures, backside surface temperature and transparent cover temperatures were measured. The thermal efficiency was calculated based on the measurements. Consisting of the fuzzy logic model of the system with the experimental data obtained, the outlet air temperature of the collector and thermal efficiency is modeled based on the input parameters according to three different membership functions (Triangle-Gaussian-Trapeze). As a result, it is concluded that the model based on the triangular membership function with fuzzy logic is 96% for the outlet temperature and 94-95% for the thermal efficiency.
Experimental Investigation of Thermal Efficiency of Solar Air Collector with Trapeze Absorber Plate
Abuska, M; Akgül, MB
In this study, thermal efficiency of solar air collectors with trapezoidal and flat plate absorber is experimentally investigated. In the experiments, outside air temperature, global radiation, temperatures of the two different points on the absorber plate, air velocity and temperature at the collector outlet are measured. The thermal efficiency is calculated based on the measurements. Average thermal efficiency of solar air collector with trapezoidal absorber plate is 28.5 % while avarage thermal efficiency of solar air collector with flat absorber plate is 23.1 %. As a result, thermal efficiency of solar air collector with trapezoidal absorber plate is higher than that of solar air collector with flat absorber plate.
Thermal performance analysis of a novel linear LED housing with inner and outer fins
Sevik, S; Abuska, M; Özdilli, Ö
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.
A comparative investigation of the effect of honeycomb core on the latent heat storage with PCM in solar air heater
Abuska, M; Sevik, S; Kayapunar, A
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 degrees 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.
Experimental performance analysis of sensible heat storage in solar air collector with cherry pits/powder under the natural convection
Abuska, M; Sevik, S; Kayapunar, A
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.

Browsing by Author "Abuska, M"

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