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3D numerical analysis of a Li-ion battery cooling system with honeycomb configuration in electrical vehicles
(Elsevier Science Inc, 2024) Nazli, Celal; Gurdal, Mehmet; Arslan, Kamil
This study focuses on the thermal challenges faced by lithium-ion batteries in electric vehicles and the importance of effective thermal management systems. It has been conducted a 3D numerical analysis to investigate the impact of different distances between batteries on heat transfer and flow characteristics in an air-cooled cooling module with an innovative honeycomb configuration. Boundary conditions and the study results were given with dimensionless parameters with longitudinal ratio (x/lambda), distance ratio (lambda), and height ratio (y/H). It was found that smaller distances between batteries let to higher temperatures at the beginning of the cooling channel due to the shorter channel width. However, as the distance between batteries increases, convective heat transfer performance improves, resulting in better temperature distributions and higher Nusselt numbers. The results shed light on the importance of optimizing the spatial arrangement of batteries in a cooling module to achieve efficient thermal management. This research contributes to bridging existing gaps in knowledge regarding battery thermal management in electric vehicles and provides insights for the design and development of more effective cooling strategies for lithium-ion batteries. In conclusion, according to the distance between batteries (S=1-3-5 mm) under a laminar flow regime, the best average Nussell numbers obtained for S=5 mm %17 and %7 heat enchantments compared to other S=1 mm and S=3mm cases, respectively. It can be observed that the convective heat transfer performance is optimal when all cases are located on the 9th battery. After the 9th battery column, the optimal heat transfer performance was observed for a thickness of 5 mm. The S=3 mm case exhibited a 7 % reduction in convective heat transfer performance compared to the S=5 mm case.
Application of nanofluid flow in entropy generation and thermal performance analysis of parabolic trough solar collector: experimental and numerical study
(Springer, 2023) Ekiciler, Recep; Arslan, Kamil; Turgut, Oguz
This study investigates numerically and experimentally the flow and heat transfer characteristics of ZnO/EG-H2O nanofluid flow in a parabolic trough solar collector at different flow rates (between 20 lit h(-1) and 80 lit h(-1)) and nanoparticle volume fractions (phi = 1%, 2%, 3%, 4%). The effects of changes in parameters such as absorbed and heat loss parameters, collector efficiency, useful energy, and temperature differences between outlet and inlet have been investigated in the context of experimental results. To obtain meaningful results in the numerical study, a non-uniform heat flux distribution on the collector absorber has been generated by the Monte Carlo Ray Tracing method (MCRT) using the commercial code SOLTRACE. Friction factor, entropy generation, PEC number, Nusselt number, and Bejan number are the parameters studied. The ZnO/EG-H2O nanofluid significantly improves the efficiency of the collector, based on the findings obtained. The highest usable energy has been obtained at the flow rate of 80 lit h(-1) with 4% ZnO/EG-H2O nanofluid. The results suggest that the temperature differential rises when ZnO/H2O has been used compared to EG-H2O. Moreover, when ZnO/EG-H2O is used with the flow rate of 80 lit h(-1) and a volume fraction of 4% of nanoparticles, the Nusselt number increases by about 100% compared to EG-H2O as the working fluid. There is a negligible increase in the overall entropy production when ZnO/EG-H2O is utilized as opposed to the base fluid. Thus, the greatest possible nf may be suggested for parabolic trough solar collector. The goal of this study is to use the findings of ZnO/EG-H2O nanofluid research to parabolic trough solar collectors. The experimental data show that compared to traditional fluid, utilizing nanofluid results in significantly improved thermal performance. In this situation, it seems that nanofluid would be the best option.
Bir hastanede ameliyathane klima santrali isıtma hattının ekserji analizi
(2015) Altundag, Ahmet; Gedık, Engin; Ergün, Alper; Arslan, Kamil; Ekıcıler, Recep
Bu çalışmada İstanbul Başkent Hastanesi?ne ait bir ameliyathane odası için kullanılan klima santrali ısıtma hattının ekserji analizi yapılmıştır. Klima Santrali (hijyenik klima) 3500 m3 /h debide olup ameliyathane için özel olarak tasarlanmıştır. Hastane binasını ısıtmak için doğalgaz yakıtlı kazan kullanılmaktadır. Isıtma sisteminde üretilen sıcak su, boylerler yardımıyla kullanım suyu, fan-coiller yardımıyla mahal ısıtma, klima santralleri yardımıyla da hijyenik alan ve mahal ısıtmasında kullanılmaktadır. Kazan 70/90 °C olarak çalışması planlanmıştır. Değişik zaman dilimleri için ölçümü yapılan kazan suyu giriş çıkış, klima santrali giriş çıkış su ve hava sıcaklıklarına bağlı olarak elde edilen termodinamik parametrelere göre seçilen tek bir ameliyathane odası için ekserji analizi hesaplamaları yapılmıştır. Yapılan hesaplamalara göre kazan ve klima santrali için ekserji kayıpları (yıkımları) ve ekserji verimleri sırasıyla 554.28 ve 3.11 kW, %21.92 ve %20.22 olarak hesaplanmıştır. Elde edilen verilere göre yapılması gereken iyileştirmeler için önerilerde bulunulmuştur.
Cfd analysis of laminar forced convective heat transfer for tio2/water nanofluid in a semi circular cross sectioned micro channel
(2019) Kaya, H.; Ekıcıler, Recep; Arslan, Kamil
In this study, forced convection flow and heat transfer characteristics of TiO2/water nanofluid flow with different nanoparticle volume fractions (1.0%, 2.0%, 3.0% and 4.0%) in semi circular cross sectioned microchannel was numerically investigated. The three dimensional study was conducted under steady state laminar flow condition where Reynolds number changing from 100 to 1000. CFD model has been generated by using ANSYS FLUENT 15.0 software based on finite volume method. The flow was under hydrodynamically and thermally developing flow condition. Uniform surface heat flux boundary condition was applied at the bottom surface of the micro channel. The average and local Nusselt number and Darcy friction factor values were obtained using numerical results. Also, the effects of using nanofluid on local values of Nusselt number and Darcy friction factor were investigated. Numerical results indicate that the increasing of nanoparticle volume fraction of nanofluid, the average Nusselt number increases; however, there is no significant variation in average Darcy friction factor.
Comparison of bi-directional multi-wave alternating magnetic field effect on ferromagnetic nanofluid flow in a circular pipe under laminar flow conditions
(Pergamon-Elsevier Science Ltd, 2020) Tekir, Mutlu; Taskesen, Edip; Aksu, Bahri; Gedik, Engin; Arslan, Kamil
Nanofluids have been attracting huge attention because of their heat transfer enhancement capabilities. Furthermore, magnetic field effect has been being researched recently. By reason of further heat transfer enhancement potential, constant and alternating magnetic fields have been utilized in the present work. Forced convection heat transfer of Fe3O4/water nanofluid flow in a straight pipe under constant and alternating magnetic field effect has been investigated experimentally. Experiments were performed under laminar flow regime (1122 < Re < 2124) and constant heat flux was applied externally on the pipe surface. It is aimed to study effect of different parameters such as Reynolds number, volume concentration of nanoparticle (0 <= phi <= 0.05), constant magnetic field (B = 0.3 T), alternating magnetic field with different wave types (sinus, square and triangle) and different frequencies (2, 5 and 15 Hz) of alternating magnetic field on the convective heat transfer. Experimental results showed that the constant magnetic field offers 13% convective heat transfer enhancement compared to the absence of a magnetic field. On the other hand, the alternating magnetic field increases the convective heat transfer in the pipe up to 35%. Furthermore, lower frequencies of the alternating magnetic field have been more effective in convective heat transfer enhancement. Square wave type alternating magnetic field steps forward in the aspect of convective heat transfer enhancement rate among the other wave types. The alternating magnetic field applications look promising in the future for increasing energy efficiency, and it can also be implemented in heat exchangers, solar collectors, emergency heat removal systems in nuclear power plants.
Convective Heat Transfer Investigation of a Confined Air Slot-Jet Impingement Cooling on Corrugated Surfaces With Different Wave Shapes
(Asme, 2019) Ekiciler, Recep; Cetinkaya, Muhammet Samet Ali; Arslan, Kamil
In this study, air jet impingement on flat, triangular-corrugated, and sinusoidal-corrugated surfaces was numerically investigated. Bottom surface was subjected to constant surface temperature. Air was the working fluid. The air exited from a rectangular shaped slot and impinged on the bottom surface. The Reynolds number was changed between 125 and 500. The continuity, momentum, and energy equations were solved using the finite volume method. The effect of the shape of bottom surface on heat and flow characteristics was investigated in detail. Average and local Nusselt number were calculated for each case. It was found out that Nusselt number increases by increasing the Reynolds number. The optimum conditions were established to get much more enhancement in terms of performance evaluation criterion (PEC). It was revealed that the shape of the cooling surface (bottom wall) influences the heat transfer substantially.
CuO/WATER NANOFLUID FLOW OVER MICROSCALE BACKWARD-FACING STEP AND ANALYSIS OF HEAT TRANSFER PERFORMANCE
(Begell House Inc, 2018) Ekiciler, Recep; Arslan, Kamil
Three-dimensional numerical simulation of steady-state laminar forced convection flow of a CuO/water nanofluid and heat transfer in a duct having a microscale backward-facing step (MBFS) are presented in this study. The study was conducted for determining the effects of nanoparticle volume fraction on the flow and heat transfer characteristics. The Reynolds number ranged from 100 to 1000. The step height and inlet height of the duct were 600 mu m and 400 mu m, respectively. The duct expansion ratio was 2.5. The downstream wall was subjected to a constant and uniform heat flux, whereas the other walls were insulated. The nanoparticle volume fraction varied from 1.0% to 4.0%. The Nusselt number and Darcy friction factor were obtained for each nanoparticle volume fraction. Plots of velocity streamlines were analyzed. It was found from the results of numerical simulation that the Nusselt number increases with increasing nanoparticle volume fraction and Reynolds number. The nanoparticle volume fraction does not exert any substantial effect on the Darcy friction factor and the length of the recirculation zone. Moreover, the performance evaluation criterion (PEC) was analyzed for nanoparticle volume fractions of 1.0%, 2.0%, 3.0%, and 4.0% of CuO. It was obtained that the volume fractions of 4.0% has the highest PEC in terms of heat transfer. It was obtained that while heat transfer for nanoparticle volume fraction of 30% and 4.0% the friction factor is superior for nanoparticle volume fraction of 1.0% and 2.0% due to the PEC number.
Effect of Al2O3-SiO2/Water Hybrid Nanofluid Filled in a Square Enclosure on the Natural Convective Heat Transfer Characteristics: A Numerical Study
(Amer Scientific Publishers, 2022) Dagdeviren, Abdullah; Gedik, Engin; Kecebas, Ali; Pazarlioglu, Hayati Kadir; Arslan, Kamil; Alsabery, Ammar I.
In this study, heat transfer enhancement by natural convection Al2O3/water mono and Al2O3-SiO2/water hybrid nanofluid in an enclosure cavity have been performed utilizing the finite element method. For numerical com-putations, the homogeneous nanofluid approach was considered. The cavity was heated from the left vertical wall and cooled from the right vertical wall while the top and bottom walls were taken as adiabatic. The effects of some related factors such as the Rayleigh number (10(3) <= Ra <= 10(6)) and nanoparticles' volume fraction IP: 182.75.148.10 On: Sat, 13 Aug 2022 10:11:41 (0 <= phi <= 0.05) on the heat transfer by natural convction were examined. To discuss fluid characteristics of mono Copyright: American Scientific Publishers and hybrid type nanofluid under natural convecton effect, the obtained results were presented as streamlines Delivered by Ingenta and isotherms. Also, variations of local and average Nusselt numbers were examined in detail. It was obtained that an increase in the nanoparticle volume fraction leads to the enhancement of convective heat transfer for all Rayleigh numbers. It was also indicated that the highest increment in heat transfer by convection occurs in the nanoparticle volume fraction of 2% for Al2O3/water and 4% for Al2O3-SiO2/water. The present study results are also consistent with the literature results.
Effect of constant magnetic field on Fe3O4-Cu/water hybrid nanofluid flow in a circular pipe
(Springer, 2022) Tekir, Mutlu; Taskesen, Edip; Gedik, Engin; Arslan, Kamil; Aksu, Bahri
The purpose of this study is to investigate experimentally the convective heat transfer of Fe3O4-Cu/water hybrid nanofluid flow and to obtain the optimum mixing ratio of the hybrid nanofluid in a straight pipe under the influence of a constant magnetic field, applied perpendicularly to the flow direction. An experimental test rig has been designed and built for this purpose followed by rigorous tests that were performed on it for various parameters such as flow rate (corresponding 994 < Re < 2337) and nanoparticle volume concentration (0 < phi < 0.02). The experimental data are consistent with the existing literature. Increasing flow rate has led to an increased Nu number. Furthermore, the addition of both Fe3O4 and Cu nanoparticles into the distilled water increases the convective heat transfer inside the pipe. A significant finding of the study is that the constant magnetic field enables up to 14% convective heat transfer enhancement as opposed to the absence of a magnetic field. Furthermore, 1.0 vol.% Fe3O4-1.0 vol.% Cu/Water hybrid nanofluid performs the best under the effect of the constant magnetic field. Accordingly, the constant magnetic field applied externally to the flow is a key factor to enhance the convective heat transfer.
Effect of hybrid nanofluid on heat transfer performance of parabolic trough solar collector receiver
(Springer, 2021) Ekiciler, Recep; Arslan, Kamil; Turgut, Oguz; Kursun, Burak
In this study, three-dimensional heat transfer and flow characteristics of hybrid nanofluids under turbulent flow condition in a parabolic trough solar collector (PTC) receiver has been investigated. Ag-ZnO/Syltherm 800, Ag-TiO2/Syltherm 800, and Ag-MgO/Syltherm 800 hybrid nanofluids with 1.0%, 2.0%, 3.0%, and 4.0% nanoparticle volume fractions are used as working fluids. Reynolds number is between 10,000 and 80,000. The temperature of the fluid is taken as 500 K. The C++ homemade code has been written for the nonuniform heat flux boundary condition for the outer surface of the receiver. Variations of thermal efficiency, heat transfer coefficient, friction factor, PEC number, Nusselt number, and temperature distribution are presented for three different types of hybrid nanofluids and four different nanoparticle volume fractions with different Reynolds numbers. Also, the graphs of the average percent increase according to Syltherm 800 are given for the working parameters. According to the results of the study, all hybrid nanofluids are found to provide superiority over the base fluid (Syltherm 800) with respect to heat transfer and flow features. Heat transfer augments with the growth of Reynolds number and nanoparticle volume fraction. Thermal efficiency, which is one of the important parameters for PTC, decreases with increasing Reynolds number and increases with the increasing volume fraction of nanoparticle. It is obtained that the most efficient working fluid for the PTC receiver is the Ag-MgO/Syltherm 800 hybrid nanofluid with 4.0% nanoparticle volume fraction.
Effect of magnetic field locations on thermo-magnetic convection performance of Fe3O4/H2O ferrofluid flowing in a novel dimpled tube: An experimental study
(Pergamon-Elsevier Science Ltd, 2023) Gursoy, Emrehan; Gurdal, Mehmet; Pazarlioglu, Hayati Kadir; Dagdeviren, Abdullah; Tekir, Mutlu; Arslan, Kamil; Gedik, Engin
The aim of this study is to examine the hydrothermal behavior of Fe3O4 Ferrofluid flowing under the effect of uniform magnetic field (0 T <= B <= 0.3 T). In addition, magnetic field locations were changed for each experiment to observe effect of the magnetic field locations (x/D = 20, 40, 60) on the hydrothermal behavior of the proposed system. Fe3O4 Ferrofluid was prepared in phi = 1.0% volume concentration in water and flows under the laminar regime (1131 <= Re <= 2102). Comparisons of the hydrothermal behavior of the novel proposed parameters were performed according to combinations of the different magnetic field locations and magnitudes. It is concluded that the highest Nusselt number was obtained using B = 0.3 T for the magnetic field location of x/D = 20 for both in smooth and dimpled tubes. Compared to B = 0 T, the Nusselt number enhancement was detected by 64.03% for smooth tube for the magnetic field location of x/D = 20 for B = 0.3 T whereas Nusselt number wasaugmented by 45.40% for dimpled tube for the same input parameters. Furthermore, no considerable changes in friction factor was determined under magnetic field effect when the application of magnetic field locations was changed. As a result of these findings, the highest increase in Performance Evaluation Criteria belonging dimpled tube was calculated by 33.54% at Re = 2102 for B = 0.16 T for the magnetic field location of x/D = 20. As a general conclusion, this study can shed light on investigating ferrofluids behavior under magnetic field applied in var-iable magnetic field locations.
The effect of MHD flow on hydrothermal characteristics of ferro-nano-fluid in circular pipe
(Taylor & Francis Inc, 2023) Taskesen, Edip; Tekir, Mutlu; Pazarlioglu, Hayati Kadir; Gurdal, Mehmet; Gedik, Engin; Arslan, Kamil
In this study, the effect of the constant magnetic field (MF) on the convective heat transfer characteristics of Fe3O4/H2O ferro-nano-fluid with different nano-fluid volumetric concentrations (1.0%, 2.0%, and 5.0%) flowing in a circular pipe has been studied experimentally. Experiments have been conducted under laminar flow regime (1000 <= Re <= 2300). Based on the experimental data, a good agreement has been found with the results and the well-known correlations in the literature. Also, it was obtained that increasing flow rate let to increase in Nusselt number. One of the most important results obtained is that the presence of MF offers up to 8.32% convective heat transfer enhancement compared with the absence of a MF. In addition, the constant MF applied externally to the flow is a key factor to control the convective heat transfer for such kind of geometry, which is widely used in thermal engineering systems.
Effect of nanoparticle shape of Al2O3/Pure Water nanofluid on evacuated U-Tube solar collector efficiency
(Pergamon-Elsevier Science Ltd, 2020) Kaya, Hueseyin; Alkasem, Mohanad; Arslan, Kamil
Evacuated U-tube solar collector (EUSC) using Al2O3/Pure Water (PW) as working fluid was investigated numerically in this research paper. The collector efficiency of the EUSC was analyzed for different operating conditions. Al2O3 nanoparticles suspended in the pure water (PW) with different nanoparticle volume concentrations and shapes were used as collector fluid. Four different nanoparticle volume concentrations (1.0, 2.0, 3.0 and 4.0 vol%) and three different nanoparticle shapes (blade, brick and platelet) were used for formation of nanofluid. Calculations were also performed with three different mass flow rates (0.01, 0.015 and 0.025 kg/s). The effect of volume concentration and shape of nano -particle on the collector efficiency of a EUSC was analyzed in detail. The highest collector efficiency was obtained at 67.1% for 4.0 vol% Al2O3/PW nanofluid with bricks nanoparticle shape which is 19.1% higher than PW as the working fluid in the system. (C) 2020 Elsevier Ltd. All rights reserved.
EFFECT OF NANOPARTICLE SHAPE ON NANOFLUID FLOW IN CONICAL HELICAL TUBE
(Begell House, Inc, 2022) Altunay, Fethi M.; Ali, Majdi A. M.; Gurdal, Mehmet; Pazarlioglu, Hayati Kadir; Arslan, Kamil; Gedik, Engin
The nanofluid flow in a conical helical tube was numerically investigated. The study has been carried out in three-dimensional laminar flow (85.73 <= De <= 175.55) condition. Al2O3-water nanofluid with different nanoparticle volume fractions (1.0%, 2.0%, 3.0%) has been used as the working fluid in the numerical analyzes. In addition, studies were carried out for blade, platelet, and cylindrical nanoparticle shapes. The average Nusselt numbers and the average Darcy friction factors have been used to estimate the flow and heat transfer performance of nanofluid flow in the conical helical tubes. Numerical results of the study have been presented as the variation of average Nusselt number and average Darcy friction factor with Dean number, nanoparticle shape, and nanoparticle volume fraction. As a result, the highest convective heat transfer performance has been obtained for the cylindrical nanoparticle shape of the %3.0 Al2O3-water nanofluid.
Effect of new design of elongated jet hole on thermal efficiency of solar air heater
(Elsevier, 2022) Pazarlioglu, Hayati Kadir; Tepe, Ahmet Umit; Tekir, Mutlu; Arslan, Kamil
Effect of new design of elongated jet hole on the thermal efficiency (eta th) of a solar air heater (SAH) has been numerically studied in this paper. Jet impingement technique, which is one of the important active techniques, has been implemented on the absorber plate of the SAH surface to increase the convective heat transfer per-formance. Several designs of elongated jet hole (EJH) technique (gradually increasing, gradually decreasing along the crossflow direction, and equally extended), which is highly effective application to get rid of cross-flow, has been inserted to the jet plate. The main interest of this paper is to investigate the effect of different EJH configurations on convective heat transfer performance and eta th of the SAH. 15 x 7 array of jets have been mounted on the confinement plate. Results have been compared with the conventional SAH, which has the jet impingement Case1. Numerical computations have been conducted using RNG k -epsilon turbulence model. Average Nusselt number (Nu) on the absorber plate surface, eta th of the SAH, and performance evaluation criteria (PEC) have been quantitatively investigated comprehensively. As a result of calculations, the Nu and eta th of SAH can be enhanced by 31.80 % and 2.46 %, respectively, using Case4 instead of Case1 at Re = 25000. Besides, the pressure drop of SAH dramatically rises by 10.26 %, when Case4 and Case1 compared with each other at Re = 25000. Despite increment in pressure drop, the PEC value achieves to 1.28. Finally, it is concluded that the equally extended EJH presents well performance compared to gradually increasing and decreasing EJH.
Effect of shape of nanoparticle on heat transfer and entropy generation of nanofluid-jet impingement cooling
(Taylor & Francis Inc, 2020) Ekiciler, Recep; Cetinkaya, Muhammet Samet Ali; Arslan, Kamil
Al2O3/water nanofluid has been numerically examined for the first time with different nanoparticle shapes including, cylindrical, blade, brick, platelet and spherical, on the flat and triangular-corrugated impinging surfaces. The volume fractions of 1.0%, 2.0% and 3.0% nanoparticles have been used. The Reynolds number is between 100-500 depending on the slot diameter. The finite volume method is utilized to determine the governing equations. The study is analyzed to determine how the flow features, heat transfer features and entropy production were affected by the diversity of nanoparticle shape, nanoparticle volume fraction, and shape of impinging surface. Darcy friction factor and Nusselt number are studied in detail for different conditions. The temperature contours are presented in the case of different nanoparticle volume fractions, nanoparticle shapes and both impinging surfaces. The results of the study suggest that the nanoparticle shape of the platelet shows the highest heat transfer development due to the thinner thermal boundary layer. Heat transfer augments with increasing volume fraction of nanoparticles. In addition, the study is consistent with the results of the literature on heat transfer and flow properties.
THE EFFECT OF VOLUME FRACTION OF SiO2 NANOPARTICLE ON FLOW AND HEAT TRANSFER CHARACTERISTICS IN A DUCT WITH CORRUGATED BACKWARD-FACING STEP
(Vinca Inst Nuclear Sci, 2018) Ekiciler, Recep; Aydeniz, Emre; Arslan, Kamil
In this paper, flow and heat transfer characteristics of SiO2-water nanofluid flow over a corrugated backward-facing step are numerically investigated. The numerical study is performed by solving governing equations (continuity, momentum, and energy) with finite volume method. The duct inlet and step heights are 4.8 mm. The expansion ratio is 2. The upstream wall, L-w and downstream wall, L-d, lengths are 48 cm and 96 cm, respectively. The downstream wall of the duct is subjected to a constant and uniform heat flux of 2000 W/m(2). The ranges of the volume fraction of nanoparticles and Reynolds number are 0%-3.0% and 135-240, respectively. The effects of the volume fraction of nanoparticles on the average Nusselt number, average Darcy friction factor, and velocity distribution are investigated under laminar forced convective nanofluid flow condition. It is revealed that the nanoparticle volume fraction substantially influences the heat transfer and flow characteristics. The volume fraction of 3.0% shows the highest heat transfer performance.
Effects of Extended Jet Holes to Heat Transfer and Flow Characteristics of the Jet Impingement Cooling
(Asme, 2019) Tepe, Ahmet Umit; Arslan, Kamil; Yetisken, Yasar; Uysal, Unal
In this study, effects of extended jet holes to heat transfer and flow characteristics of jet impingement cooling were numerically investigated. Cross-flow in the impinging jet cooling adversely affects the heat transfer on the target surface. The main purpose of this study is to reduce the negative effect of cross-flow on heat transfer by extending jet holes toward the target surface with nozzles. This study has been conducted under turbulent flow condition (15,000 <= Re <= 45,000). The surface of the turbine blade, which is the target surface, has been modeled as a flat plate. The effect of the ribs, placed on the target surface, on the heat transfer has been also investigated, and the results were compared with the flat surface. The parameters such as average and local Nusselt numbers on the target surface, flow characteristics, and compressor power have been examined in detail. It was obtained from the numerical results that the average Nusselt number increases with decreasing the gap between the target surface and the nozzle. In addition, the higher average Nusselt number was obtained on the flat surface than the ribbed surface. The lowest compressor power was achieved in the 5Dj nozzle gap for the flat surface and in the 4Dj nozzle gap for the ribbed surface.
Effects of using nanofluid, applying a magnetic field, and placing turbulators in channels on the convective heat transfer: A comprehensive review
(Pergamon-Elsevier Science Ltd, 2022) Gurdal, Mehmet; Arslan, Kamil; Gedik, Engin; Minea, Alina Adriana
Recent studies in the field of thermal engineering revealed that employing nanofluid as a working fluid in a specific channel, considering both turbulators and magnetic field effect is scarce. Studies on the convective heat transfer performance of the thermal systems focus mostly on the effect of using either nanofluid as a new fluid, magnetic field, or turbulators. This review highlights the single and combined effects of these parameters on the heat transfer enhancement of such systems. Nanofluid type, its volume fraction, channel and turbulator geometry, magnetic field type, and flow regime were considered as the base parameters while the enhancement in heat transfer is evaluated. From a state-of-the-art review, it was noticed that most studies reveal that increasing the volume fraction of nanofluid, magnetic field strength, and Reynolds number can attain an upsurge in the heat transfer in a specific channel. Nevertheless, drawbacks are poorly discussed in the open literature. Regarding the turbulator geometry, which actually limits the magnetohydrodynamic and thermal boundary layer development, its complexity boosts also the convective heat transfer. The maximum heat transfer enhancement was noticed for higher nanoparticle volume fractions, higher magnetic field strengths, and complex geometries in channel flow. The highest heat transfer improvement was obtained for the MWCNT/H2O nanofluid (i.e., between 70% and 190%). With the effect of magnetic field intensity of Ha = 30 applied to the Cu/H2O nanofluid flow, a thermal recovery of 76% was achieved. Concluding, this comprehensive review can be beneficial to researchers working in the field of flow and heat transfer applications with the use of nanofluid, turbulator, and magnetic field together.
Efficiency Assessment of an Evacuated U-Tube Solar Collector Using Silver Nanofluid
(Asme, 2019) Kaya, Huseyin; Eltugral, Nurettin; Kurukavak, Ali; Arslan, Kamil
A water-based silver nanofluid (Ag/PW) was prepared from gelatin-stabilized silver nanoparticles (Ag NPs) of about 15 nm and further used as a working fluid in an evacuated U-tube solar collector (EUSC) to investigate the variation in the collector efficiency. An Ag/PW nanofluid having 0.035 wt% was prepared and demonstrated a good promise of colloidal stability when dispersed in pure water. Collector efficiency measurements were carried out at outdoor conditions with four different mass flow rate values (0.063, 0.051, 0.033, and 0.02 kg/s). Results showed that Ag/PW have superior heat transfer properties than that of pure water as the base fluid. It was found that the efficiency of the collector was directly proportional to the mass flow rate of the working fluid until an optimum value was attained. Experimental results show that the highest collector efficiency was 72.2% at 0.051 kg/s mass flow rate, which is 21.3% higher than that of the pure water.

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