Ihsan Dagtekin - Academia.edu (original) (raw)
Papers by Ihsan Dagtekin
DergiPark (Istanbul University), Feb 1, 2001
Bu çalışmada, L şeklindeki bir oyukta doğal taşınımla ısı transferi sayısal olarak incelenmiştir.... more Bu çalışmada, L şeklindeki bir oyukta doğal taşınımla ısı transferi sayısal olarak incelenmiştir. Oyuğun bir tarafı soğuk, diğer taraf ise sıcak olarak alınmıştır. Tavan ve taban kısımları yalıtımlıdır. Doğal taşınım ısı transferini yöneten denklemler, bir sonlu hacim üzerinden integre edilerek tekil denklemler elde edilmiştir. SIMPLEM çözüm algoritmasını kullanan bir bilgisayar programı yapılmıştır. Hesaplamalar, Rayleigh sayısının 10 4 < Ra < 10 6 değerleri için elde edilmiştir. L şeklinin boyutları değiştirilerek hesaplamalar gerçekleştirilmiştir.
World Academy of Science, Engineering and Technology, International Journal of Energy and Power Engineering, Oct 29, 2015
This research presents the design and analysis of solar air-conditioning systems particularly sol... more This research presents the design and analysis of solar air-conditioning systems particularly solar chimney which is a passive strategy for natural ventilation, and demonstrates the structures of these systems’ using Computational Fluid Dynamic (CFD) and finally compares the results with several examples, which have been studied experimentally and carried out previously. In order to improve the performance of solar chimney system, highly efficient sub-system components are considered for the design. The general purpose of the research is to understand how efficiently solar chimney systems generate cooling, and is to improve the efficient of such systems for integration with existing and future domestic buildings. Keywords—Solar cooling system, solar chimney, active and passive solar technologies, natural ventilation, cavity depth, CFD models for solar chimney.
International Communications in Heat and Mass Transfer, Apr 1, 2007
This study deals with the prediction of entropy generation (EG) for natural convection in a Γ-sha... more This study deals with the prediction of entropy generation (EG) for natural convection in a Γ-shaped enclosure. Heat removal is achieved from cooler vertical sides while the horizontal walls are insulated perfectly. The results are reported with streamlines, isotherms, mean Nusselt numbers, EG due to heat transfer and fluid friction for Ra number ranging from 10 3 to 10 6 , irreversibility distribution ratio ϕ, ranging from 10 − 5 to 10 − 3 , different step height (h) and step width (w) values. It is observed that at a fixed Ra number, with an increase in aspect ratio (AR = h/w) mean Nusselt number values increase. For Ra numbers ranging from 10 3 to 10 4 , the total EG is mostly due to heat transfer because of relatively low velocities, but for Ra N 10 4 the contribution to due to fluid friction becomes effective even has comparable values from Ra = 10 5 to Ra = 10 6 .
DOAJ (DOAJ: Directory of Open Access Journals), Feb 1, 2001
Bu çalışmada, L şeklindeki bir oyukta doğal taşınımla ısı transferi sayısal olarak incelenmiştir.... more Bu çalışmada, L şeklindeki bir oyukta doğal taşınımla ısı transferi sayısal olarak incelenmiştir. Oyuğun bir tarafı soğuk, diğer taraf ise sıcak olarak alınmıştır. Tavan ve taban kısımları yalıtımlıdır. Doğal taşınım ısı transferini yöneten denklemler, bir sonlu hacim üzerinden integre edilerek tekil denklemler elde edilmiştir. SIMPLEM çözüm algoritmasını kullanan bir bilgisayar programı yapılmıştır. Hesaplamalar, Rayleigh sayısının 10 4 < Ra < 10 6 değerleri için elde edilmiştir. L şeklinin boyutları değiştirilerek hesaplamalar gerçekleştirilmiştir.
International Journal of Heat and Mass Transfer, Apr 1, 2004
This study aims to analyze mixed convection in a square cavity with two moving vertical walls by ... more This study aims to analyze mixed convection in a square cavity with two moving vertical walls by finite volume method. The cavity filled with Non-Newtonian fluid of Bingham model is heated from below and cooled by the other walls. This study has been conducted for certain parameters of Reynolds number (Re=1-100), Richardson number (Ri=1-20), Prandtl number (Pr=1-500), and Bingham number has been studied from 0 to 10. The results indicate that the increase in yield stress drops the heat transfer and the flow become flatter, while increasing Reynolds number augments it. The convective transport is dominant when increasing Richardson number which leads to enhance heat transfer in the cavity for both Newtonian and Non-Newtonian fluid. A correlation of Nusselt number is given in function of different parameters.
Proceeding of Energy and the Environment, 1998
DergiPark (Istanbul University), Jun 1, 2014
International Journal of Heat and Mass Transfer, 2004
This study aims to analyze mixed convection in a square cavity with two moving vertical walls by ... more This study aims to analyze mixed convection in a square cavity with two moving vertical walls by finite volume method. The cavity filled with Non-Newtonian fluid of Bingham model is heated from below and cooled by the other walls. This study has been conducted for certain parameters of Reynolds number (Re=1-100), Richardson number (Ri=1-20), Prandtl number (Pr=1-500), and Bingham number has been studied from 0 to 10. The results indicate that the increase in yield stress drops the heat transfer and the flow become flatter, while increasing Reynolds number augments it. The convective transport is dominant when increasing Richardson number which leads to enhance heat transfer in the cavity for both Newtonian and Non-Newtonian fluid. A correlation of Nusselt number is given in function of different parameters.
International Communications in Heat and Mass Transfer, 2007
This study deals with the prediction of entropy generation (EG) for natural convection in a Γ-sha... more This study deals with the prediction of entropy generation (EG) for natural convection in a Γ-shaped enclosure. Heat removal is achieved from cooler vertical sides while the horizontal walls are insulated perfectly. The results are reported with streamlines, isotherms, mean Nusselt numbers, EG due to heat transfer and fluid friction for Ra number ranging from 10 3 to 10 6 , irreversibility distribution ratio ϕ, ranging from 10 − 5 to 10 − 3 , different step height (h) and step width (w) values. It is observed that at a fixed Ra number, with an increase in aspect ratio (AR = h/w) mean Nusselt number values increase. For Ra numbers ranging from 10 3 to 10 4 , the total EG is mostly due to heat transfer because of relatively low velocities, but for Ra N 10 4 the contribution to due to fluid friction becomes effective even has comparable values from Ra = 10 5 to Ra = 10 6 .
Thermal Science
In this study, heating performances of horizontal and vertical earth-air heat exchangers with equ... more In this study, heating performances of horizontal and vertical earth-air heat exchangers with equal pipe lengths were evaluated in ANSYS FLUENT 19.2 simulation program based on CFD for the winter period of Bitlis, Turkey. Thermal per?formance analyses regarding vertical and horizontal 3-D-modeled earth-air heat exchangers were evaluated in steady-state condition of the simulation program for different values of Re = 5?103, 104, 2?104, 4?104, 6?104, 8?104, and 105 numbers by using standard k-? turbulence model. Numerical results obtained from CFD based simulation program were compared with a numerical study in the literature, and it was determined that there was a consistency between the results. The pressure loss and fan power values of horizontal and vertical earth-air heat exchangers were also investigated in addition their thermal performances. A good agreement was found between the pressure loss values obtained from the theoretical and simulation calculations of both earth-air h...
Proceeding of Energy and the Environment, 1998, 2023
Arabian Journal for Science and Engineering, 2018
Today, earth–air heat exchangers (EAHEs) are important heat exchangers used in the air-conditioni... more Today, earth–air heat exchangers (EAHEs) are important heat exchangers used in the air-conditioning of buildings and can be seen in different types and capacities. Thermal comfort is perceived as the comfort of human beings under given room conditions, namely average temperature and relative humidity. For example, the value of average comfort temperature in a room is between 294 and 296 K. The main objective of this analysis is not to obtain the lower air temperature of medium, rather to obtain comfort temperature interval of 294–296 K. This thermal comfort temperature has been achieved at nearly all channel outlets in 1 m depth. For the numerical analysis of EAHE, the maximum mean air temperature of July of the city of Elazığ was used. Computational fluid dynamics ANSYS FLUENT 12.1 program was chosen to examine the thermal comfort condition of a typical building. In the analysis of the thermal performance of the EAHE, examinations were made for different earth depths ($$H = 1$$H=1, 2, 3 m). PVC was chosen as the EAHE channel material. The numerical model was solved in three dimensions in the steady-state condition using different Reynolds number values ($$Re = 5\times 10^{3}, 10^{4}, 15\times 10^{3}, 2\times 10^{4}, 4\times 10^{4}, 6\times 10^{4}, 10^{5}$$Re=5×103,104,15×103,2×104,4×104,6×104,105) in the turbulent flow. It was determined that the best thermal performance is at the smallest air inlet velocity. According to the numerical results, it was found that the cooling energy consumption required to provide thermal comfort condition for the typical building is reduced.
International Journal of Energy Research, 2004
Second law analysis of heat transfer in laminar flow for hexagonal cross-section duct was analyse... more Second law analysis of heat transfer in laminar flow for hexagonal cross-section duct was analysed analytically. Geometrical effect of hexagonal duct was considered. The variation of total entropy generation was studied along the duct length. As a working fluid water and unused engine oil were used to compare the effect of fluid in the duct. Results were compared with circular cross-section duct. It is found that the non-dimensional entropy generation in a hexagonal cross-section duct can be as high as a factor of four than that for a circular duct. Further, the unused engine oil gives up to about ten times lower nondimensional entropy generation values than that of water but needs about ten times more pumping power to heat transfer ratio.
International Journal for Numerical Methods in Fluids, 2011
Skip to Main Content. Wiley Online Library will be disrupted 3 Mar from 10-13 GMT for monthly mai... more Skip to Main Content. Wiley Online Library will be disrupted 3 Mar from 10-13 GMT for monthly maintenance. ...
International Communications in Heat and Mass Transfer, 2009
... Spiga and Dall&amp;amp;amp;#x27;Olio [2] made a numerical experiment to investigate N... more ... Spiga and Dall&amp;amp;amp;#x27;Olio [2] made a numerical experiment to investigate Newtonian fluid flow and heat transfer characteristics in flat tubes with rounded edges. ... He made a comparison between these ducts to find an optimum shape. ...
International Communications in Heat and Mass Transfer, 2008
In this study, heat transfer due to double impinging vertical slot jets onto an isothermal wall w... more In this study, heat transfer due to double impinging vertical slot jets onto an isothermal wall was investigated numerically for laminar flow regime. Navier-Stokes and energy equations were discretized with a finite volume procedure on a non-staggered grid arrangement using SIMPLEM (SIMPLE-Modified) algorithm. The effect of the jet Reynolds number, the jet-isothermal bottom wall spacing, and the distance between two jets on heat transfer and flow field was examined. Air was chosen as the working fluid (Pr = 0.71). It is found that multi-cellular flow is formed in the impingement region due to interaction between two jets and entrainment effects in the duct. The mean Nusselt number increases almost linearly with increasing of Reynolds number at isothermal surface. When Reynolds number of the first jet is higher than second one the heat transfer is enhanced significantly.
DergiPark (Istanbul University), Feb 1, 2001
Bu çalışmada, L şeklindeki bir oyukta doğal taşınımla ısı transferi sayısal olarak incelenmiştir.... more Bu çalışmada, L şeklindeki bir oyukta doğal taşınımla ısı transferi sayısal olarak incelenmiştir. Oyuğun bir tarafı soğuk, diğer taraf ise sıcak olarak alınmıştır. Tavan ve taban kısımları yalıtımlıdır. Doğal taşınım ısı transferini yöneten denklemler, bir sonlu hacim üzerinden integre edilerek tekil denklemler elde edilmiştir. SIMPLEM çözüm algoritmasını kullanan bir bilgisayar programı yapılmıştır. Hesaplamalar, Rayleigh sayısının 10 4 < Ra < 10 6 değerleri için elde edilmiştir. L şeklinin boyutları değiştirilerek hesaplamalar gerçekleştirilmiştir.
World Academy of Science, Engineering and Technology, International Journal of Energy and Power Engineering, Oct 29, 2015
This research presents the design and analysis of solar air-conditioning systems particularly sol... more This research presents the design and analysis of solar air-conditioning systems particularly solar chimney which is a passive strategy for natural ventilation, and demonstrates the structures of these systems’ using Computational Fluid Dynamic (CFD) and finally compares the results with several examples, which have been studied experimentally and carried out previously. In order to improve the performance of solar chimney system, highly efficient sub-system components are considered for the design. The general purpose of the research is to understand how efficiently solar chimney systems generate cooling, and is to improve the efficient of such systems for integration with existing and future domestic buildings. Keywords—Solar cooling system, solar chimney, active and passive solar technologies, natural ventilation, cavity depth, CFD models for solar chimney.
International Communications in Heat and Mass Transfer, Apr 1, 2007
This study deals with the prediction of entropy generation (EG) for natural convection in a Γ-sha... more This study deals with the prediction of entropy generation (EG) for natural convection in a Γ-shaped enclosure. Heat removal is achieved from cooler vertical sides while the horizontal walls are insulated perfectly. The results are reported with streamlines, isotherms, mean Nusselt numbers, EG due to heat transfer and fluid friction for Ra number ranging from 10 3 to 10 6 , irreversibility distribution ratio ϕ, ranging from 10 − 5 to 10 − 3 , different step height (h) and step width (w) values. It is observed that at a fixed Ra number, with an increase in aspect ratio (AR = h/w) mean Nusselt number values increase. For Ra numbers ranging from 10 3 to 10 4 , the total EG is mostly due to heat transfer because of relatively low velocities, but for Ra N 10 4 the contribution to due to fluid friction becomes effective even has comparable values from Ra = 10 5 to Ra = 10 6 .
DOAJ (DOAJ: Directory of Open Access Journals), Feb 1, 2001
Bu çalışmada, L şeklindeki bir oyukta doğal taşınımla ısı transferi sayısal olarak incelenmiştir.... more Bu çalışmada, L şeklindeki bir oyukta doğal taşınımla ısı transferi sayısal olarak incelenmiştir. Oyuğun bir tarafı soğuk, diğer taraf ise sıcak olarak alınmıştır. Tavan ve taban kısımları yalıtımlıdır. Doğal taşınım ısı transferini yöneten denklemler, bir sonlu hacim üzerinden integre edilerek tekil denklemler elde edilmiştir. SIMPLEM çözüm algoritmasını kullanan bir bilgisayar programı yapılmıştır. Hesaplamalar, Rayleigh sayısının 10 4 < Ra < 10 6 değerleri için elde edilmiştir. L şeklinin boyutları değiştirilerek hesaplamalar gerçekleştirilmiştir.
International Journal of Heat and Mass Transfer, Apr 1, 2004
This study aims to analyze mixed convection in a square cavity with two moving vertical walls by ... more This study aims to analyze mixed convection in a square cavity with two moving vertical walls by finite volume method. The cavity filled with Non-Newtonian fluid of Bingham model is heated from below and cooled by the other walls. This study has been conducted for certain parameters of Reynolds number (Re=1-100), Richardson number (Ri=1-20), Prandtl number (Pr=1-500), and Bingham number has been studied from 0 to 10. The results indicate that the increase in yield stress drops the heat transfer and the flow become flatter, while increasing Reynolds number augments it. The convective transport is dominant when increasing Richardson number which leads to enhance heat transfer in the cavity for both Newtonian and Non-Newtonian fluid. A correlation of Nusselt number is given in function of different parameters.
Proceeding of Energy and the Environment, 1998
DergiPark (Istanbul University), Jun 1, 2014
International Journal of Heat and Mass Transfer, 2004
This study aims to analyze mixed convection in a square cavity with two moving vertical walls by ... more This study aims to analyze mixed convection in a square cavity with two moving vertical walls by finite volume method. The cavity filled with Non-Newtonian fluid of Bingham model is heated from below and cooled by the other walls. This study has been conducted for certain parameters of Reynolds number (Re=1-100), Richardson number (Ri=1-20), Prandtl number (Pr=1-500), and Bingham number has been studied from 0 to 10. The results indicate that the increase in yield stress drops the heat transfer and the flow become flatter, while increasing Reynolds number augments it. The convective transport is dominant when increasing Richardson number which leads to enhance heat transfer in the cavity for both Newtonian and Non-Newtonian fluid. A correlation of Nusselt number is given in function of different parameters.
International Communications in Heat and Mass Transfer, 2007
This study deals with the prediction of entropy generation (EG) for natural convection in a Γ-sha... more This study deals with the prediction of entropy generation (EG) for natural convection in a Γ-shaped enclosure. Heat removal is achieved from cooler vertical sides while the horizontal walls are insulated perfectly. The results are reported with streamlines, isotherms, mean Nusselt numbers, EG due to heat transfer and fluid friction for Ra number ranging from 10 3 to 10 6 , irreversibility distribution ratio ϕ, ranging from 10 − 5 to 10 − 3 , different step height (h) and step width (w) values. It is observed that at a fixed Ra number, with an increase in aspect ratio (AR = h/w) mean Nusselt number values increase. For Ra numbers ranging from 10 3 to 10 4 , the total EG is mostly due to heat transfer because of relatively low velocities, but for Ra N 10 4 the contribution to due to fluid friction becomes effective even has comparable values from Ra = 10 5 to Ra = 10 6 .
Thermal Science
In this study, heating performances of horizontal and vertical earth-air heat exchangers with equ... more In this study, heating performances of horizontal and vertical earth-air heat exchangers with equal pipe lengths were evaluated in ANSYS FLUENT 19.2 simulation program based on CFD for the winter period of Bitlis, Turkey. Thermal per?formance analyses regarding vertical and horizontal 3-D-modeled earth-air heat exchangers were evaluated in steady-state condition of the simulation program for different values of Re = 5?103, 104, 2?104, 4?104, 6?104, 8?104, and 105 numbers by using standard k-? turbulence model. Numerical results obtained from CFD based simulation program were compared with a numerical study in the literature, and it was determined that there was a consistency between the results. The pressure loss and fan power values of horizontal and vertical earth-air heat exchangers were also investigated in addition their thermal performances. A good agreement was found between the pressure loss values obtained from the theoretical and simulation calculations of both earth-air h...
Proceeding of Energy and the Environment, 1998, 2023
Arabian Journal for Science and Engineering, 2018
Today, earth–air heat exchangers (EAHEs) are important heat exchangers used in the air-conditioni... more Today, earth–air heat exchangers (EAHEs) are important heat exchangers used in the air-conditioning of buildings and can be seen in different types and capacities. Thermal comfort is perceived as the comfort of human beings under given room conditions, namely average temperature and relative humidity. For example, the value of average comfort temperature in a room is between 294 and 296 K. The main objective of this analysis is not to obtain the lower air temperature of medium, rather to obtain comfort temperature interval of 294–296 K. This thermal comfort temperature has been achieved at nearly all channel outlets in 1 m depth. For the numerical analysis of EAHE, the maximum mean air temperature of July of the city of Elazığ was used. Computational fluid dynamics ANSYS FLUENT 12.1 program was chosen to examine the thermal comfort condition of a typical building. In the analysis of the thermal performance of the EAHE, examinations were made for different earth depths ($$H = 1$$H=1, 2, 3 m). PVC was chosen as the EAHE channel material. The numerical model was solved in three dimensions in the steady-state condition using different Reynolds number values ($$Re = 5\times 10^{3}, 10^{4}, 15\times 10^{3}, 2\times 10^{4}, 4\times 10^{4}, 6\times 10^{4}, 10^{5}$$Re=5×103,104,15×103,2×104,4×104,6×104,105) in the turbulent flow. It was determined that the best thermal performance is at the smallest air inlet velocity. According to the numerical results, it was found that the cooling energy consumption required to provide thermal comfort condition for the typical building is reduced.
International Journal of Energy Research, 2004
Second law analysis of heat transfer in laminar flow for hexagonal cross-section duct was analyse... more Second law analysis of heat transfer in laminar flow for hexagonal cross-section duct was analysed analytically. Geometrical effect of hexagonal duct was considered. The variation of total entropy generation was studied along the duct length. As a working fluid water and unused engine oil were used to compare the effect of fluid in the duct. Results were compared with circular cross-section duct. It is found that the non-dimensional entropy generation in a hexagonal cross-section duct can be as high as a factor of four than that for a circular duct. Further, the unused engine oil gives up to about ten times lower nondimensional entropy generation values than that of water but needs about ten times more pumping power to heat transfer ratio.
International Journal for Numerical Methods in Fluids, 2011
Skip to Main Content. Wiley Online Library will be disrupted 3 Mar from 10-13 GMT for monthly mai... more Skip to Main Content. Wiley Online Library will be disrupted 3 Mar from 10-13 GMT for monthly maintenance. ...
International Communications in Heat and Mass Transfer, 2009
... Spiga and Dall&amp;amp;amp;#x27;Olio [2] made a numerical experiment to investigate N... more ... Spiga and Dall&amp;amp;amp;#x27;Olio [2] made a numerical experiment to investigate Newtonian fluid flow and heat transfer characteristics in flat tubes with rounded edges. ... He made a comparison between these ducts to find an optimum shape. ...
International Communications in Heat and Mass Transfer, 2008
In this study, heat transfer due to double impinging vertical slot jets onto an isothermal wall w... more In this study, heat transfer due to double impinging vertical slot jets onto an isothermal wall was investigated numerically for laminar flow regime. Navier-Stokes and energy equations were discretized with a finite volume procedure on a non-staggered grid arrangement using SIMPLEM (SIMPLE-Modified) algorithm. The effect of the jet Reynolds number, the jet-isothermal bottom wall spacing, and the distance between two jets on heat transfer and flow field was examined. Air was chosen as the working fluid (Pr = 0.71). It is found that multi-cellular flow is formed in the impingement region due to interaction between two jets and entrainment effects in the duct. The mean Nusselt number increases almost linearly with increasing of Reynolds number at isothermal surface. When Reynolds number of the first jet is higher than second one the heat transfer is enhanced significantly.