Muhsin Kiliç | Uludag University (original) (raw)
Papers by Muhsin Kiliç
Discs rotating at different speeds are found in the internal cooling-air systems of most gas turb... more Discs rotating at different speeds are found in the internal cooling-air systems of most gas turbines. Defining Γ as the ratio of the rotational speed of the slower disc to that of the faster one then Γ = −1, 0 and +1 represents the three important cases of contra-rotating discs, rotor-stator systems and co-rotating discs, respectively. A finite-volume, axisymmetric, elliptic, multigrid solver, employing a low-Reynolds-number k-ε turbulence model, is used for the fluid-dynamics computations in these systems. The complete Γ region, −1 ≤ Γ ≤ +1, is considered for rotational Reynolds numbers of up to Reφ = 1.25 × 106, and the effect of a radial outflow of cooling air is also included for nondimensional flow rates of up to Cw = 9720. As Γ → −1, Stewartson-flow occurs with radial outflow in boundary layers on both discs and between which is a core of nonrotating fluid. For Γ ≈ 0, Batchelor-flow occurs, with radial outflow in the boundary layer on the faster disc, inflow on the slower one, and between which is a core of rotating fluid. As Γ → +1, Ekman-layer flow dominates with nonentraining boundary layers on both discs and a rotating core between. Where available, measured velocity distributions are in good agreement with the computed values.
Uludağ University Journal of The Faculty of Engineering, Apr 1, 2013
Son yıllarda dünyadaki enerji gereksinimi, belirgin bir artış göstermektedir. Buna bağlı olarak t... more Son yıllarda dünyadaki enerji gereksinimi, belirgin bir artış göstermektedir. Buna bağlı olarak temiz ve sürdürülebilir enerji kaynakları üzerindeki bilimsel araştırmalar ivme kazanmıştır. Bir enerji kaynağının var olması tek başına yeterli değildir aynı zamanda bu enerji kaynağının kapasitesi, çevreyle olan uyumu, ekonomik faktörler, devamlılığı gibi parametrelerde dikkate alınmalıdır. Bu parametreler göz önünde bulundurulduğunda "sürdürülebilirlik" ve "yenilenebilir" kavramları önem kazanmaktadır. Bu çalışmada, öncelikle sürdürülebilirliği değerlendirme araçları literatürde mevcut bilgilerle genel olarak ifade edilmiş ve indeks ve göstergelere dayanan sürdürülebilirlik araçları literatürde yer alan örneklerle açıklanmaya çalışılmış ve Türkiye şartları için örnek uygulamalar yapılmıştır. Daha sonra bazı yenilenebilir enerji kaynakları için küresel sürdürülebilirlik indeks ve göstergelerine değinilerek enerji kaynaklarının sürdürülebilirliğine ilişkin sonuç ve önerilerde bulunulmuştur.
A detailed literature review is presented for the applications of the heat pump technologies on t... more A detailed literature review is presented for the applications of the heat pump technologies on the electric vehicles Heating, Ventilation and Air Conditioning (HVAC) system. Due to legal regulations, automotive manufacturers have to produce more efficient and low carbon emission vehicles. Electric vehicles can be provided these requirements but the battery technologies and energy managements systems are still developing considering battery life and vehicle range. On the other hand, energy consumption for HVAC units has an important role on the energy management of these vehicles. Moreover, the energy requirement of HVAC processes for different environmental conditions are significantly affect the total energy consumption of these vehicles. For the heating process, the coolant of internal combustion (IC) engine can be utilized but in electric vehicles, we have not got any adequate waste heat source for this process. The heat pump technology is one of the alternative choices for the industry due to having high coefficient of performance (COP), but these systems have some disadvantages which can be improved with the other technologies. In this study, a literature review is performed considering alternative refrigerants, performance characteristics of different heat pump systems for electric vehicles and thermal management systems of electric vehicles.
Uludağ University Journal of The Faculty of Engineering, Apr 1, 2007
Son yıllarda, günümüzdeki ağır bataryaların yerini alacak hafif ve kompakt bir güç kaynağı gelişt... more Son yıllarda, günümüzdeki ağır bataryaların yerini alacak hafif ve kompakt bir güç kaynağı geliştirilmesi yönünde çalışmalar devam etmektedir. Güç üretimi için mikro-gaz türbinlerinden faydalanma üzerine artan ilgi, bu sistemlerin geniş bir aralıkta işletme şartlarını sağlayabilmesi için, araştırmacıları çok etkin sistemler tasarlamaya yönlendirmektedir. Mikro güç üretim sistemlerini önemli kılan neden, yakıt bazlı güç üretim sistemlerinin hala en iyi şarj edilebilir güç üretim sistemlerinden 100 kat daha fazla enerji yoğunluğu içermesidir. Yakıt pillerinden beklenen yüksek verim iken mikro gaz türbinlerinden umulan yüksek güç yoğunluğunu sunmasıdır. Bu çalışmada, bir mikro gaz türbininin, belirli termal ve mekanik yüklemeler altında çalışma durumu bir benzetim programı kullanarak incelenmiştir ayrıca komponent geometrilerinin multidisipliner optimizasyon sonucu elde edilmesi anlatılmıştır.
Bu çalışmada yapılardaki yangın güvenlik önlemleri ve yangınları söndürmek amacıyla kullanılan ya... more Bu çalışmada yapılardaki yangın güvenlik önlemleri ve yangınları söndürmek amacıyla kullanılan yangın söndürme sistemleri tanıtılmakta ve muhtemel yangın risklerinde yangın tipi ve şartlarına bağlı olarak yangın söndürme sisteminin seçim esasları verilmektedir.
Nucleation and Atmospheric Aerosols, 2018
In this study cooling of a LED unit with heatsink and liquid cooling block which is used in autom... more In this study cooling of a LED unit with heatsink and liquid cooling block which is used in automotive head lamp applications has been investigated numerically and experimentally. Junction temperature of a LED which is cooled with heatsink and liquid cooling block obtained in the experiment. 23°C is used both in the simulation and the experiment phase. Liquid cooling block material is choosed aluminium (Al) and polyamide. All tests and simulation are performed with three different flow rate. Temperature distribution of the designed product is investigated by doing the numerical simulations with a commercially software. In the simulations, fluid flow is assumed to be steady, incompressible and laminar and 3 dimensional (3D) Navier-Stokes equations are used. According to the calculations it is obtained that junction temperature is higher in the heatsink design compared to block cooled one. By changing the block material, it is desired to investigate the variation on the LED junction temperature. It is found...
Elsevier eBooks, 2018
Abstract Relatively low-temperature renewable energy and industrial waste heat resources can be u... more Abstract Relatively low-temperature renewable energy and industrial waste heat resources can be used to configure a solid adsorption refrigeration or cooling system that has no destructive or harmful effects on the environment. Therefore, such a system has attracted much interest for researchers across the world. The physical adsorption phenomenon is a reversible process realized mainly within the cavities and pore surfaces of the solid adsorbent. It is known that the adsorption characteristics of an adsorbent–adsorbate pair are strongly related to variations in temperature and pressure. The objective of the current study was to investigate experimentally the adsorption characteristics of the refrigerants R134a and R404a onto activated carbon. An experimental setup working with a constant-volume variable pressure method was used in the experimental measurements. During the adsorption processes, data from experimental isotherms were obtained at different constant temperatures ranging from 293K to 323K while pressure varied from 0 to about 500 kPa. These data are useful for designing adsorption cooling and refrigeration systems. Commercially available granular and pellet-type activated carbon (AC) samples were considered in this work. Experimental measurements were performed for four different adsorbent–adsorbate pairs obtained by combining the adsorbents (granulated AC and pellet AC) and adsorbates (R134a and R404a). Adsorption parameters were evaluated from the measured isotherms to obtain correlations in the form of the Dubinin–Astakhov equation. The pressure and temperature dependence of the isosteric enthalpies of adsorption were computed by evaluating the measured data and the derived equations. Furthermore, the parameters of the correlations are provided for each adsorbent–adsorbate pair. Results are compared and discussed in detail.
The paper describes a combined experimental and Cµ D ,C E1,Ce2 constants in turbulence model comp... more The paper describes a combined experimental and Cµ D ,C E1,Ce2 constants in turbulence model computational study of laminar and turbulent flow between term in k equation
International Journal of Heat and Fluid Flow, Dec 1, 1994
ABSTRACT This paper describes a combined computational and experimental study of the flow between... more ABSTRACT This paper describes a combined computational and experimental study of the flow between two contrarotating discs for −1 ≤ Γ ≤ 0 (where Γ is the ratio of the speed of the slower disc to that of the faster one) for the case where there is a superposed radial outflow of air. The computations were conducted using an elliptic solver and a low-Reynolds-number k-ϵ turbulence model, and velocity measurements were made using a laser-Doppler anenometry system. Two basic flow structures can occur: Batchelor-type flow, where there are separate boundary layers on each disc with a rotating core of fluid between, and Stewartson-type flow, where there is virtually no core rotation. The main effect of a superposed flow is to reduce the core rotation and to promote the transition from Batchelor-type flow to Stewartson-type flow. For most of the results, there is good agreement between the computed and measured velocities. Computed moment coefficients show that, for Γ = −1, superposed flow has little effect on Cm: an accepted correlation of Cm for a free disc should provide a useful estimate for design purposes.
... alan faktörü h Isı geçiş katsayısı, W/(m2.K) hfg Suyun buharlaşma gizli ısısı, J/kg i Buhar g... more ... alan faktörü h Isı geçiş katsayısı, W/(m2.K) hfg Suyun buharlaşma gizli ısısı, J/kg i Buhar geçirgenlik verimi K İç vücut ile deri arasında etkin iletim katsayısı, W/(m2.K) LR Lewis oranı, °C/Pa m Vücut kütlesi, kg M Toplam metabolik ısı üretim oranı, W/m2 mx Kütlesel debi, kg/(sm2) ...
International Journal of Vehicle Design, 2010
Automobile compartments are exposed to unstable heat loads due to solar radiation, combined conve... more Automobile compartments are exposed to unstable heat loads due to solar radiation, combined convection, conduction and radiation heat transfer through the cabin surfaces, air exchange and metabolic heat production of the occupants. In this study, a dynamic model of the heat loads that affect the thermal behaviour of the automobile compartment was developed in a Matlab-Simulink environment. Solar irradiation on cabin surfaces and thermal interactions between the driver and cabin interior can be calculated by the model. In order to determine mean radiant temperature and direct solar irradiation absorbed by the driver, view factors between the person and the interior surrounding surfaces were obtained by using a 3-D CFD model of cabin and driver. Experiments were also performed and the simulation results were compared with the measured and the obtained experimental data available in the literature. The effects of colour (white and black) and windows' optical properties (transmissivity, reflectivity and absorptivity coefficients) on the thermal comfort were also investigated.
Journal of Fluid Mechanics, Dec 25, 1994
This paper describes a combined computational and experimental study of the flow between contra-r... more This paper describes a combined computational and experimental study of the flow between contra-rotating disks for-1 6 r < 0 and Re, = lo5, where r is the ratio of the speed of the slower disk to that of the faster one and Re, is the rotational Reynolds number of the faster disk. For r = 0, the rotor-stator case, laminar and turbulent computations and experimental measurements show that laminar Batchelor-type flow occurs: there is radial outflow in a boundary layer on the rotating disk, inflow on the stationary disk and a rotating core of fluid between. For r=-1, the laminar computations produce Batchelor-type flow : there is radial outflow on both disks and inflow in a free shear layer in the mid-plane, on either side of which is a rotating core of fluid. The turbulent computations and the velocity measurements for r =-1 show Stewartson-type flow: radial outflow occurs in laminar boundary layers on the disks and inflow occurs in a non-rotating turbulent core between the boundary layers. For intermediate values of I-, transition from Batchelor-type flow to Stewartson-type flow is associated with a two-cell structure, the two-cells being separated by a streamline that stagnates on the slower disk; Batchelor-type flow occurs radially outward of the stagnation point and Stewartson-type flow radially inward. The turbulent computations are mainly in good agreement with the measured velocities for r = 0 and r =-1, where either Batchelor-type flow or Stewartson-type flow occurs; there is less good agreement at intermediate values of r, particularly for r =-0.4 where the double transition of Batchelor-type flow to Stewartson-type flow and laminar to turbulent flow occurs in the two-cell structure.
International Journal of Vehicle Design, 2022
International Communications in Heat and Mass Transfer, Jul 1, 2010
In this study, the temperature dependence of effective thermal conductivity (ETC) for samples of ... more In this study, the temperature dependence of effective thermal conductivity (ETC) for samples of binary, ternary, and quadruple glass wools reinforced with aluminium foil was examined. The experiments were realized by the guarded hot plate in temperature differences of 5, 10 and 15°C and the temperatures of 25 and 40°C. The results revealed that in the case of reinforcing the aluminium foil, ETC increased with increasing the temperature or changing of temperature difference (5, and 15°C). Also, an increase of additional layers decrease its' influence on low temperature. Consequently, reflectivity materials may increase or reduce ETC.
Heat and Mass Transfer, Feb 19, 2012
Energy Conversion and Management, Oct 1, 2020
Combined-cycle pulse detonation engines are promising contenders for hypersonic propulsion system... more Combined-cycle pulse detonation engines are promising contenders for hypersonic propulsion systems. In the present study, design and propulsive performance analysis of combined-cycle pulse detonation turbofan engines (PDTEs) is presented. Analysis is done with respect to Mach number at two consecutive modes of operation: (1) Combined-cycle PDTE using a pulse detonation afterburner mode (PDA-mode) and (2) combined-cycle PDTE in pulse detonation ramjet engine mode (PDRE-mode). The performance of combined-cycle PDTEs is compared with baseline afterburning turbofan and ramjet engines. The comparison of afterburning modes is done for Mach numbers from 0 to 3 at 15.24 km altitude conditions, while that of pulse detonation ramjet engine (PDRE) is done for Mach 1.5 to Mach 6 at 18.3 km altitude conditions. The analysis shows that the propulsive performance of a turbine engine can be greatly improved by replacing the conventional afterburner with a pulse detonation afterburner (PDA). The PDRE also outperforms its ramjet counterpart at all flight conditions considered herein. The gains obtained are outstanding for both the combined-cycle PDTE modes compared to baseline turbofan and ramjet engines.
International Journal of Energy Research, 2006
In this study, a theoretical approach is proposed for the prediction of time and temperature duri... more In this study, a theoretical approach is proposed for the prediction of time and temperature during the heat charge and discharge in the latent heat storage of phase changed materials (PCM). By the use of the average values of the mean specific heat capacities for the phase-changed materials, analytical solutions are obtained and compared with the available experimental data in the literature. It is shown that decreasing the entry temperature of the working fluid from À4 to À158C has a very dominant and strong effect on the PCM solidification time. The effect of the working fluid flow rate and the material of PCM capsules on the time for complete solidification and total charging is also investigated. The agreement between the present theoretical model results and the experimental data related to the cooling using small spheres and the heat storage using rectangle containers is very good. The largest difference between the present results and the experimental data becomes about 10% when the fluid temperature approaches the phase change temperature at high temperatures.
International Communications in Heat and Mass Transfer, Nov 1, 2008
In this study a combined computational model of a room with virtual thermal manikin with real dim... more In this study a combined computational model of a room with virtual thermal manikin with real dimensions and physiological shape was used to determine heat and mass transfer between human body and environment. Three dimensional fluid flow, temperature and moisture distribution, heat transfer (sensible and latent) between human body and ambient, radiation and convection heat transfer rates on human body surfaces, local and average convection coefficients and skin temperatures were calculated. The radiative heat transfer coefficient predicted for the whole-body was 4.6 W m−2 K−1, closely matching the generally accepted whole-body value of 4.7 W m−2 K−1. Similarly, the whole-body natural convection coefficient for the manikin fell within the mid-range of previously published values at 3.8 W m−2 K−1. Results of calculations were in agreement with available experimental and theoretical data in literature.
IOP conference series, Feb 23, 2021
This study presents the effects of duct design on thermo-fluidic characteristics of ventilated cl... more This study presents the effects of duct design on thermo-fluidic characteristics of ventilated clutch pressure plate via validated numerical model. Two different duct designs are considered. Moreover, variation of duct width and airfoil shaped duct designs are investigated. Compared to non-ventilated conventional clutch pressure plate, results show that implementing duct shape enhances the overall cooling performance by up to 154% at idle speed 550 rpm, 137% at 1200 rpm, and 142% at 2000 rpm. Once only the duct shapes are considered, it is found that the variation of inlet and outlet duct width has negligible effect on overall cooling performance. Further, radial airfoil shaped duct design shows the best cooling performance in overall among all duct shapes, and enhances the overall cooling performance by up to 11% at 550 rpm idle speed compared to non-airfoil radial duct design. In addition, implementation of ventilated design results weight reduction up to 25%. Heat transfer enhancement mechanisms clarified in the present study are helpful to motivate further innovative lightweight solutions in order to overcome the challenges related to the recent CO2 regulation for Heavy Duty Vehicles.
Discs rotating at different speeds are found in the internal cooling-air systems of most gas turb... more Discs rotating at different speeds are found in the internal cooling-air systems of most gas turbines. Defining Γ as the ratio of the rotational speed of the slower disc to that of the faster one then Γ = −1, 0 and +1 represents the three important cases of contra-rotating discs, rotor-stator systems and co-rotating discs, respectively. A finite-volume, axisymmetric, elliptic, multigrid solver, employing a low-Reynolds-number k-ε turbulence model, is used for the fluid-dynamics computations in these systems. The complete Γ region, −1 ≤ Γ ≤ +1, is considered for rotational Reynolds numbers of up to Reφ = 1.25 × 106, and the effect of a radial outflow of cooling air is also included for nondimensional flow rates of up to Cw = 9720. As Γ → −1, Stewartson-flow occurs with radial outflow in boundary layers on both discs and between which is a core of nonrotating fluid. For Γ ≈ 0, Batchelor-flow occurs, with radial outflow in the boundary layer on the faster disc, inflow on the slower one, and between which is a core of rotating fluid. As Γ → +1, Ekman-layer flow dominates with nonentraining boundary layers on both discs and a rotating core between. Where available, measured velocity distributions are in good agreement with the computed values.
Uludağ University Journal of The Faculty of Engineering, Apr 1, 2013
Son yıllarda dünyadaki enerji gereksinimi, belirgin bir artış göstermektedir. Buna bağlı olarak t... more Son yıllarda dünyadaki enerji gereksinimi, belirgin bir artış göstermektedir. Buna bağlı olarak temiz ve sürdürülebilir enerji kaynakları üzerindeki bilimsel araştırmalar ivme kazanmıştır. Bir enerji kaynağının var olması tek başına yeterli değildir aynı zamanda bu enerji kaynağının kapasitesi, çevreyle olan uyumu, ekonomik faktörler, devamlılığı gibi parametrelerde dikkate alınmalıdır. Bu parametreler göz önünde bulundurulduğunda "sürdürülebilirlik" ve "yenilenebilir" kavramları önem kazanmaktadır. Bu çalışmada, öncelikle sürdürülebilirliği değerlendirme araçları literatürde mevcut bilgilerle genel olarak ifade edilmiş ve indeks ve göstergelere dayanan sürdürülebilirlik araçları literatürde yer alan örneklerle açıklanmaya çalışılmış ve Türkiye şartları için örnek uygulamalar yapılmıştır. Daha sonra bazı yenilenebilir enerji kaynakları için küresel sürdürülebilirlik indeks ve göstergelerine değinilerek enerji kaynaklarının sürdürülebilirliğine ilişkin sonuç ve önerilerde bulunulmuştur.
A detailed literature review is presented for the applications of the heat pump technologies on t... more A detailed literature review is presented for the applications of the heat pump technologies on the electric vehicles Heating, Ventilation and Air Conditioning (HVAC) system. Due to legal regulations, automotive manufacturers have to produce more efficient and low carbon emission vehicles. Electric vehicles can be provided these requirements but the battery technologies and energy managements systems are still developing considering battery life and vehicle range. On the other hand, energy consumption for HVAC units has an important role on the energy management of these vehicles. Moreover, the energy requirement of HVAC processes for different environmental conditions are significantly affect the total energy consumption of these vehicles. For the heating process, the coolant of internal combustion (IC) engine can be utilized but in electric vehicles, we have not got any adequate waste heat source for this process. The heat pump technology is one of the alternative choices for the industry due to having high coefficient of performance (COP), but these systems have some disadvantages which can be improved with the other technologies. In this study, a literature review is performed considering alternative refrigerants, performance characteristics of different heat pump systems for electric vehicles and thermal management systems of electric vehicles.
Uludağ University Journal of The Faculty of Engineering, Apr 1, 2007
Son yıllarda, günümüzdeki ağır bataryaların yerini alacak hafif ve kompakt bir güç kaynağı gelişt... more Son yıllarda, günümüzdeki ağır bataryaların yerini alacak hafif ve kompakt bir güç kaynağı geliştirilmesi yönünde çalışmalar devam etmektedir. Güç üretimi için mikro-gaz türbinlerinden faydalanma üzerine artan ilgi, bu sistemlerin geniş bir aralıkta işletme şartlarını sağlayabilmesi için, araştırmacıları çok etkin sistemler tasarlamaya yönlendirmektedir. Mikro güç üretim sistemlerini önemli kılan neden, yakıt bazlı güç üretim sistemlerinin hala en iyi şarj edilebilir güç üretim sistemlerinden 100 kat daha fazla enerji yoğunluğu içermesidir. Yakıt pillerinden beklenen yüksek verim iken mikro gaz türbinlerinden umulan yüksek güç yoğunluğunu sunmasıdır. Bu çalışmada, bir mikro gaz türbininin, belirli termal ve mekanik yüklemeler altında çalışma durumu bir benzetim programı kullanarak incelenmiştir ayrıca komponent geometrilerinin multidisipliner optimizasyon sonucu elde edilmesi anlatılmıştır.
Bu çalışmada yapılardaki yangın güvenlik önlemleri ve yangınları söndürmek amacıyla kullanılan ya... more Bu çalışmada yapılardaki yangın güvenlik önlemleri ve yangınları söndürmek amacıyla kullanılan yangın söndürme sistemleri tanıtılmakta ve muhtemel yangın risklerinde yangın tipi ve şartlarına bağlı olarak yangın söndürme sisteminin seçim esasları verilmektedir.
Nucleation and Atmospheric Aerosols, 2018
In this study cooling of a LED unit with heatsink and liquid cooling block which is used in autom... more In this study cooling of a LED unit with heatsink and liquid cooling block which is used in automotive head lamp applications has been investigated numerically and experimentally. Junction temperature of a LED which is cooled with heatsink and liquid cooling block obtained in the experiment. 23°C is used both in the simulation and the experiment phase. Liquid cooling block material is choosed aluminium (Al) and polyamide. All tests and simulation are performed with three different flow rate. Temperature distribution of the designed product is investigated by doing the numerical simulations with a commercially software. In the simulations, fluid flow is assumed to be steady, incompressible and laminar and 3 dimensional (3D) Navier-Stokes equations are used. According to the calculations it is obtained that junction temperature is higher in the heatsink design compared to block cooled one. By changing the block material, it is desired to investigate the variation on the LED junction temperature. It is found...
Elsevier eBooks, 2018
Abstract Relatively low-temperature renewable energy and industrial waste heat resources can be u... more Abstract Relatively low-temperature renewable energy and industrial waste heat resources can be used to configure a solid adsorption refrigeration or cooling system that has no destructive or harmful effects on the environment. Therefore, such a system has attracted much interest for researchers across the world. The physical adsorption phenomenon is a reversible process realized mainly within the cavities and pore surfaces of the solid adsorbent. It is known that the adsorption characteristics of an adsorbent–adsorbate pair are strongly related to variations in temperature and pressure. The objective of the current study was to investigate experimentally the adsorption characteristics of the refrigerants R134a and R404a onto activated carbon. An experimental setup working with a constant-volume variable pressure method was used in the experimental measurements. During the adsorption processes, data from experimental isotherms were obtained at different constant temperatures ranging from 293K to 323K while pressure varied from 0 to about 500 kPa. These data are useful for designing adsorption cooling and refrigeration systems. Commercially available granular and pellet-type activated carbon (AC) samples were considered in this work. Experimental measurements were performed for four different adsorbent–adsorbate pairs obtained by combining the adsorbents (granulated AC and pellet AC) and adsorbates (R134a and R404a). Adsorption parameters were evaluated from the measured isotherms to obtain correlations in the form of the Dubinin–Astakhov equation. The pressure and temperature dependence of the isosteric enthalpies of adsorption were computed by evaluating the measured data and the derived equations. Furthermore, the parameters of the correlations are provided for each adsorbent–adsorbate pair. Results are compared and discussed in detail.
The paper describes a combined experimental and Cµ D ,C E1,Ce2 constants in turbulence model comp... more The paper describes a combined experimental and Cµ D ,C E1,Ce2 constants in turbulence model computational study of laminar and turbulent flow between term in k equation
International Journal of Heat and Fluid Flow, Dec 1, 1994
ABSTRACT This paper describes a combined computational and experimental study of the flow between... more ABSTRACT This paper describes a combined computational and experimental study of the flow between two contrarotating discs for −1 ≤ Γ ≤ 0 (where Γ is the ratio of the speed of the slower disc to that of the faster one) for the case where there is a superposed radial outflow of air. The computations were conducted using an elliptic solver and a low-Reynolds-number k-ϵ turbulence model, and velocity measurements were made using a laser-Doppler anenometry system. Two basic flow structures can occur: Batchelor-type flow, where there are separate boundary layers on each disc with a rotating core of fluid between, and Stewartson-type flow, where there is virtually no core rotation. The main effect of a superposed flow is to reduce the core rotation and to promote the transition from Batchelor-type flow to Stewartson-type flow. For most of the results, there is good agreement between the computed and measured velocities. Computed moment coefficients show that, for Γ = −1, superposed flow has little effect on Cm: an accepted correlation of Cm for a free disc should provide a useful estimate for design purposes.
... alan faktörü h Isı geçiş katsayısı, W/(m2.K) hfg Suyun buharlaşma gizli ısısı, J/kg i Buhar g... more ... alan faktörü h Isı geçiş katsayısı, W/(m2.K) hfg Suyun buharlaşma gizli ısısı, J/kg i Buhar geçirgenlik verimi K İç vücut ile deri arasında etkin iletim katsayısı, W/(m2.K) LR Lewis oranı, °C/Pa m Vücut kütlesi, kg M Toplam metabolik ısı üretim oranı, W/m2 mx Kütlesel debi, kg/(sm2) ...
International Journal of Vehicle Design, 2010
Automobile compartments are exposed to unstable heat loads due to solar radiation, combined conve... more Automobile compartments are exposed to unstable heat loads due to solar radiation, combined convection, conduction and radiation heat transfer through the cabin surfaces, air exchange and metabolic heat production of the occupants. In this study, a dynamic model of the heat loads that affect the thermal behaviour of the automobile compartment was developed in a Matlab-Simulink environment. Solar irradiation on cabin surfaces and thermal interactions between the driver and cabin interior can be calculated by the model. In order to determine mean radiant temperature and direct solar irradiation absorbed by the driver, view factors between the person and the interior surrounding surfaces were obtained by using a 3-D CFD model of cabin and driver. Experiments were also performed and the simulation results were compared with the measured and the obtained experimental data available in the literature. The effects of colour (white and black) and windows' optical properties (transmissivity, reflectivity and absorptivity coefficients) on the thermal comfort were also investigated.
Journal of Fluid Mechanics, Dec 25, 1994
This paper describes a combined computational and experimental study of the flow between contra-r... more This paper describes a combined computational and experimental study of the flow between contra-rotating disks for-1 6 r < 0 and Re, = lo5, where r is the ratio of the speed of the slower disk to that of the faster one and Re, is the rotational Reynolds number of the faster disk. For r = 0, the rotor-stator case, laminar and turbulent computations and experimental measurements show that laminar Batchelor-type flow occurs: there is radial outflow in a boundary layer on the rotating disk, inflow on the stationary disk and a rotating core of fluid between. For r=-1, the laminar computations produce Batchelor-type flow : there is radial outflow on both disks and inflow in a free shear layer in the mid-plane, on either side of which is a rotating core of fluid. The turbulent computations and the velocity measurements for r =-1 show Stewartson-type flow: radial outflow occurs in laminar boundary layers on the disks and inflow occurs in a non-rotating turbulent core between the boundary layers. For intermediate values of I-, transition from Batchelor-type flow to Stewartson-type flow is associated with a two-cell structure, the two-cells being separated by a streamline that stagnates on the slower disk; Batchelor-type flow occurs radially outward of the stagnation point and Stewartson-type flow radially inward. The turbulent computations are mainly in good agreement with the measured velocities for r = 0 and r =-1, where either Batchelor-type flow or Stewartson-type flow occurs; there is less good agreement at intermediate values of r, particularly for r =-0.4 where the double transition of Batchelor-type flow to Stewartson-type flow and laminar to turbulent flow occurs in the two-cell structure.
International Journal of Vehicle Design, 2022
International Communications in Heat and Mass Transfer, Jul 1, 2010
In this study, the temperature dependence of effective thermal conductivity (ETC) for samples of ... more In this study, the temperature dependence of effective thermal conductivity (ETC) for samples of binary, ternary, and quadruple glass wools reinforced with aluminium foil was examined. The experiments were realized by the guarded hot plate in temperature differences of 5, 10 and 15°C and the temperatures of 25 and 40°C. The results revealed that in the case of reinforcing the aluminium foil, ETC increased with increasing the temperature or changing of temperature difference (5, and 15°C). Also, an increase of additional layers decrease its' influence on low temperature. Consequently, reflectivity materials may increase or reduce ETC.
Heat and Mass Transfer, Feb 19, 2012
Energy Conversion and Management, Oct 1, 2020
Combined-cycle pulse detonation engines are promising contenders for hypersonic propulsion system... more Combined-cycle pulse detonation engines are promising contenders for hypersonic propulsion systems. In the present study, design and propulsive performance analysis of combined-cycle pulse detonation turbofan engines (PDTEs) is presented. Analysis is done with respect to Mach number at two consecutive modes of operation: (1) Combined-cycle PDTE using a pulse detonation afterburner mode (PDA-mode) and (2) combined-cycle PDTE in pulse detonation ramjet engine mode (PDRE-mode). The performance of combined-cycle PDTEs is compared with baseline afterburning turbofan and ramjet engines. The comparison of afterburning modes is done for Mach numbers from 0 to 3 at 15.24 km altitude conditions, while that of pulse detonation ramjet engine (PDRE) is done for Mach 1.5 to Mach 6 at 18.3 km altitude conditions. The analysis shows that the propulsive performance of a turbine engine can be greatly improved by replacing the conventional afterburner with a pulse detonation afterburner (PDA). The PDRE also outperforms its ramjet counterpart at all flight conditions considered herein. The gains obtained are outstanding for both the combined-cycle PDTE modes compared to baseline turbofan and ramjet engines.
International Journal of Energy Research, 2006
In this study, a theoretical approach is proposed for the prediction of time and temperature duri... more In this study, a theoretical approach is proposed for the prediction of time and temperature during the heat charge and discharge in the latent heat storage of phase changed materials (PCM). By the use of the average values of the mean specific heat capacities for the phase-changed materials, analytical solutions are obtained and compared with the available experimental data in the literature. It is shown that decreasing the entry temperature of the working fluid from À4 to À158C has a very dominant and strong effect on the PCM solidification time. The effect of the working fluid flow rate and the material of PCM capsules on the time for complete solidification and total charging is also investigated. The agreement between the present theoretical model results and the experimental data related to the cooling using small spheres and the heat storage using rectangle containers is very good. The largest difference between the present results and the experimental data becomes about 10% when the fluid temperature approaches the phase change temperature at high temperatures.
International Communications in Heat and Mass Transfer, Nov 1, 2008
In this study a combined computational model of a room with virtual thermal manikin with real dim... more In this study a combined computational model of a room with virtual thermal manikin with real dimensions and physiological shape was used to determine heat and mass transfer between human body and environment. Three dimensional fluid flow, temperature and moisture distribution, heat transfer (sensible and latent) between human body and ambient, radiation and convection heat transfer rates on human body surfaces, local and average convection coefficients and skin temperatures were calculated. The radiative heat transfer coefficient predicted for the whole-body was 4.6 W m−2 K−1, closely matching the generally accepted whole-body value of 4.7 W m−2 K−1. Similarly, the whole-body natural convection coefficient for the manikin fell within the mid-range of previously published values at 3.8 W m−2 K−1. Results of calculations were in agreement with available experimental and theoretical data in literature.
IOP conference series, Feb 23, 2021
This study presents the effects of duct design on thermo-fluidic characteristics of ventilated cl... more This study presents the effects of duct design on thermo-fluidic characteristics of ventilated clutch pressure plate via validated numerical model. Two different duct designs are considered. Moreover, variation of duct width and airfoil shaped duct designs are investigated. Compared to non-ventilated conventional clutch pressure plate, results show that implementing duct shape enhances the overall cooling performance by up to 154% at idle speed 550 rpm, 137% at 1200 rpm, and 142% at 2000 rpm. Once only the duct shapes are considered, it is found that the variation of inlet and outlet duct width has negligible effect on overall cooling performance. Further, radial airfoil shaped duct design shows the best cooling performance in overall among all duct shapes, and enhances the overall cooling performance by up to 11% at 550 rpm idle speed compared to non-airfoil radial duct design. In addition, implementation of ventilated design results weight reduction up to 25%. Heat transfer enhancement mechanisms clarified in the present study are helpful to motivate further innovative lightweight solutions in order to overcome the challenges related to the recent CO2 regulation for Heavy Duty Vehicles.
Progress in Exergy, Energy, and the Environment 2014, pp 553-558
Nowadays the focus of the power sector is on renewable energy sources. Even so, in Turkey, the mo... more Nowadays the focus of the power sector is on renewable energy sources. Even so, in Turkey, the most preferred power plants are still co-generation
power plants. Considering installed power, gas turbine power plants are the most used type. In gas turbine power cycles, both power and efficiency are
highly affected by atmospheric temperature. In this study, the degree-day method is used to expose the variation of the electric power of a gas turbine with
respect to atmospheric conditions. The installed capacity of the gas turbine is 237 MW. The operating data were supplied by Ovaakça Power Plant
Administration of Bursa/Turkey. In this paper it is indicated that, for a 45 °C increment of atmospheric temperature, mass flow through the compressor at a
unit time decreases by about 85.2 kg. Therefore, the compression work decreased by about 11.45 %. In addition, by means of the atmospheric
temperature increment, both the total energy input via natural gas and intake airflow rate were decreased by 17.1 % and this resulted in a reduction in net
electric power production.