Ahmet Koca - Academia.edu (original) (raw)

Papers by Ahmet Koca

Expert Systems With Applications, 2011

An artificial neural network (ANN) model was used to estimate the solar radiation parameters for ... more An artificial neural network (ANN) model was used to estimate the solar radiation parameters for seven cities from Mediterranean region of Anatolia in Turkey. As well known that Turkey is a bridge between Asia and Europe and it lies in a sunny belt, between 36°and 42°N latitudes. Indeed, the country has sufficient solar radiation intensities for solar applications. In order to make estimation of solar radiation, the data from the Turkish State and Meteorological Service were used. Data of 2006 were used for testing and data of 2005, 2007, and 2008 were estimated. Effects of number of input parameters were tested on solar radiation that was output layer. With this aim, number of input layer parameters changed from 2 to 6. The obtained results indicated that the method could be used by researchers or scientists to design high efficiency solar devices. It was also found that number of input parameters was the most effective parameter on estimation of future data on solar radiation.

Expert Systems With Applications, 2010

The performance of a solar collector system using sodium carbonate decahydrate ðNa 2 CO 3 Á10H 2 ... more The performance of a solar collector system using sodium carbonate decahydrate ðNa 2 CO 3 Á10H 2 OÞ as Phase Change Material (PCM) was experimentally investigated during March and collector efficiency was compared with those of convectional system including no PCM. We also made a series of predictions by using three different soft computing techniques as Artificial Neural Networks (ANN), Adaptive-Network-Based Fuzzy Inference System (ANFIS) and Support Vector Machines (SVM). It was found that the solar collector system with PCM is more effective than convectional systems. Soft computing techniques can be used to model of a solar collector with PCM. Furthermore, analysis of soft computing showed that SVM technique gives the best results than that of ANFIS and ANN.

Building and Environment, 2007

Buoyancy induced natural convection is investigated with a numerical technique in Gambrel roofs. ... more Buoyancy induced natural convection is investigated with a numerical technique in Gambrel roofs. The geometry adapted to both winter day conditions, the bottom is hot temperature while top is cold, and summer day conditions, bottom is cold and inclined top wall is hot temperature. Governing equations in streamfunction-vorticity form are solved with finite difference technique and algebraic equations are solved using successive under relaxation (SUR) method. Rayleigh number is taken as parameter which affects the flow and heat transfer. Its value changes between 10 3 and 10 7 . It is found that winterlike boundary conditions are more effective than summerlike boundary conditions on the flow field and heat transfer in the roof. r

International Communications in Heat and Mass Transfer, 2007

The effect of Prandtl number on natural convection heat transfer and fluid flow in triangular enc... more The effect of Prandtl number on natural convection heat transfer and fluid flow in triangular enclosures with localized heating has been analyzed by solving governing equations of natural convection in streamfunction-vorticity form with finite-difference technique. Solution of linear algebraic equations was made by Successive Under Relaxation (SUR) method. Bottom wall of triangle is heated partially while inclined wall is maintained at a lower uniform temperature than heated wall while remaining walls are insulated. Computations were carried out for dimensionless heater locations (0.15 ≤ s ≤ 0.95), dimensionless heater length (0.1 ≤ w ≤ 0.9), Prandtl number (0.01 ≤ Pr ≤ 15) and Rayleigh number (10 3 ≤ Ra ≤ 10 6 ). Aspect ratio of triangle was chosen as unity. It is observed that both flow and temperature fields are affected with the changing of Prandtl number, location of heater and length of heater as well as Rayleigh number.

Journal of Applied Sciences, 2006

Applied Thermal Engineering, 2009

The phenomena of natural convection in an inclined square enclosure heated via corner heater have... more The phenomena of natural convection in an inclined square enclosure heated via corner heater have been studied numerically. Finite difference method is used for solving momentum and energy equations in the form of stream function-vorticity. One wall of the enclosure is isothermal but its temperature is colder than that of heaters while the remaining walls are adiabatic. The numerical procedure adopted in this analysis yields consistent performance over a wide range of parameters; Rayleigh number, Ra (10 3 6 Ra 6 10 6 ); Prandtl number, Pr (0.07 6 Pr 6 70); dimensionless lengths of heater in x and y directions (0.25 6 hx 6 0.75, 0.25 6 hy 6 0.75); and inclination angle, / (0°6 / 6 270°). It is observed that heat transfer is maximum or minimum depending on the inclination angle and depending on the length of the corner heaters. The effect of Prandtl number on mean Nusselt number is more significant for Pr < 1.

International Journal of Heat and Mass Transfer, 2009

Numerical analyses of the flow and heat transfer due to buoyancy forces in a square enclosure div... more Numerical analyses of the flow and heat transfer due to buoyancy forces in a square enclosure divided by an impermeable partition between air and water filled chests were carried out using a finite difference technique. The enclosure was heated from left wall and cooled from right, isothermally. Horizontal walls were adiabatic. The partition divided the enclosure into air and water regions. Thus, two cases were examined: left side of partition was filled with air and right side was filled with water (Case I, air-partition-water) and left side was filled with water and right side with air (Case II, water-partition-air). Epoxy was chosen as partition material. Results were obtained for different Grashof numbers (10 3 6 Gr 6 10 6 ), thickness of the partition (0.05 6 e 6 0.2) and location of the partition (0.25 6 c 6 0.75). An analytical treatment has been performed for low Grashof numbers. Numerical and analytical results gave an acceptable agreement. It was found that filling of fluid into chests is important for obtaining maximum heat transfer and energy saving. When left chest was filled with air (Case I), higher heat transfer was formed. It was an interesting result that heat transfer decreased with increasing of location of the partition for all values of partition thickness at Case I. On the contrary, heat transfer was a decreasing function of increasing value of location of the partition.

Computers & Mathematics With Applications, 2008

A numerical study has been carried out on partially heated triangular enclosures with eave. The e... more A numerical study has been carried out on partially heated triangular enclosures with eave. The eave and inclined wall has a cold temperature. The laminar, two-dimensional, steady governing equations of natural convection are solved in the streamfunction-vorticity form using a finite difference technique. Streamline, isotherm and Nusselt number are presented for different parameters such as aspect ratio AR = H/L from 0.25 to 1, ratio of eave length E = L/n where n changes from 3 to 7 and Rayleigh number from 10 3 to 10 6 . It is observed that the heat transfer decreases with increasing aspect ratio for small Rayleigh number but increases for higher Rayleigh number. Heat transfer also increases with decreasing eave length.

Journal of Applied Sciences, 2007

In the practical applications, roofs of buildings can be in different shapes depending on archite... more In the practical applications, roofs of buildings can be in different shapes depending on architectural design of building or climate. Some of these building roofs can be classified as gambrel, saltbox and gable roofs. In the present study, we investigated the natural convection heat transfer and fluid flow inside the gambrel, gable and saltbox roofs for winter boundary conditions. With this aim, the identified roofs are compared with each other from the heat transfer and flow field point of view. Effects of Rayleigh number also tested in each type. Results are presented with streamlines, isotherms, local and mean Nusselt numbers. It is aimed that this study will help for designer to show more efficient ways of saving energy.

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International Communications in Heat and Mass Transfer, 2009

International Communications in Heat and Mass Transfer, 2010

Laminar natural convection in inclined enclosures filled with different fluids was studied by a n... more Laminar natural convection in inclined enclosures filled with different fluids was studied by a numerical method. The enclosure was divided by a solid impermeable divider. One side of partition of enclosure was filled with air and the other side had water. The enclosure was heated from one vertical wall and cooled from the other while horizontal walls were adiabatic. The governing equations which were written in stream function-vorticity form were solved using a finite difference technique. Results were presented by streamlines, isotherms, mean and local Nusselt numbers for different thermal conductivity ratios of solid impermeable material (plywood or concrete), inclination angle (0°≤ ϕ ≤ 360°) and Grashof numbers (10 3 ≤ Gr ≤ 10 6 ). The code was validated by earlier studies, which are available in the literature on conjugate natural convection heat transfer. Analytical solutions were obtained for low Grashof numbers. Obtained results showed that both heat transfer and flow strength strongly depended on thermal conductivity ratio of the solid material of partition, inclination angle and Grashof numbers. The heat transfer was lower in the air side of the enclosure than that of the water side.

Applied Thermal Engineering, 2008

A numerical analysis of the entropy production has been performed due to natural convection heat ... more A numerical analysis of the entropy production has been performed due to natural convection heat transfer and fluid flow in isosceles triangular enclosures with partially heated from below and symmetrically cooled from sloping walls. Governing equations are solved by finite difference method. Governing parameters on flow and temperature fields are Rayleigh number (10 3 6 Ra 6 8.8 · 10 5 ), dimensionless length of heater (0.25 6 (' 0 = '/L) 6 1.0), dimensionless location of heater (0.25 6 (c 0 = c/L) 6 0.75) and inclination angle of slopping walls (30°6 b 6 60°). Heat transfer results are presented in terms of local and mean Nusselt numbers (Nu) while entropy production results are shown with entropy production number (N s ) and Bejan number (Be). Isotherms, streamlines, contours of entropy production due to heat transfer and fluid friction irreversibility are plotted. It is observed that entropy production number increases but Bejan number decreases with increasing of Rayleigh number. However, both entropy production due to heat transfer and fluid friction irreversibility are affected by higher inclination angle of triangle and length of heater.

International Communications in Heat and Mass Transfer, 2010

A numerical work has been performed to analyze the heat transfer and fluid flow in a pent-roof ty... more A numerical work has been performed to analyze the heat transfer and fluid flow in a pent-roof type combustion chamber. Dynamic mesh model was used to simulation piston intake stroke. Revolution of piston (1000 ≤ n ≤ 5000) is the main governing parameter on heat and fluid flow. k-ε turbulence model was used to predict the flow in the cylinder of a non-compressing fluid. They were solved with finite volume method and FLUENT 12.0 commercial code. Velocity profiles, temperature distribution, pressure distribution and velocity vectors are presented. It is found that the inclined surface of pent-roof type of combustion chamber reduces the swirl effect and it can be a control parameter for heat and fluid flow.

Renewable Energy, 2008

Analysis of energy and exergy has been performed for a latent heat storage system with phase chan... more Analysis of energy and exergy has been performed for a latent heat storage system with phase change material (PCM) for a flat-plate solar collector. CaCl 2 Á 6H 2 O was used as PCM in thermal energy storage (TES) system. The designed collector combines in single unit solar energy collection and storage. PCMs are stored in a storage tank, which is located under the collector. A special heat transfer fluid was used to transfer heat from collector to PCM. Exergy analysis, which is based on the second law of thermodynamics, and energy analysis, which is based on the first law, were applied for evaluation of the system efficiency for charging period. The analyses were performed on 3 days in October. It was observed that the average net energy and exergy efficiencies are 45% and 2.2%, respectively.

International Communications in Heat and Mass Transfer, 2006

Natural convection heat transfer has been analyzed numerically in a triangle enclosure with flush... more Natural convection heat transfer has been analyzed numerically in a triangle enclosure with flush mounted heater on vertical wall. Finite difference method is used in solution of governing equations in streamfunction-vorticity form and linear algebraic equations were solved via Successive Under Relaxation (SUR). Governing parameters on heat transfer and flow fields are aspect ratio of triangle, location of heater, length of heater and Rayleigh number. It is observed that the most important parameter on heat transfer and flow field is the position of heater which can be a control parameter for the present system.

International Communications in Heat and Mass Transfer, 2008

Entropy generation due to conjugate natural convection heat transfer and fluid flow has been stud... more Entropy generation due to conjugate natural convection heat transfer and fluid flow has been studied inside an enclosure with bounded by two solid massive walls from vertical sides at different thicknesses. Enclosure is differentially heated from vertical walls and horizontal walls are adiabatic. Governing equations which are written in streamfunction-vorticity form solved by finite difference technique for the governing parameters as Rayleigh number, 10 3 ≤ Ra ≤ 10 6 , length ratio of solid walls as ɛ 1 (for left vertical wall) and ɛ 2 (for right vertical wall) and thermal conductivity ratio of solid to fluid (k), 1 ≤ k ≤ 10. Entropy generation contours due to fluid friction and heat transfer irreversibility, isotherms, streamlines, Nusselt numbers and velocity profiles were obtained. It is found that entropy generation increases with increasing of thermal conductivity ratio and thicknesses of the walls. Entropy generation due to heat transfer is more significant than that of fluid flow irreversibility for all values of thickness of the solid vertical walls.

International Communications in Heat and Mass Transfer, 2011

Heat and Mass Transfer, 2011

Natural convection heat transfer in an inclined fin attached square enclosure is studied both exp... more Natural convection heat transfer in an inclined fin attached square enclosure is studied both experimentally and numerically. Bottom wall of enclosure has higher temperature than that of top wall while vertical walls are adiabatic. Inclined fin has also adiabatic boundary conditions. Numerical solutions have been done by writing a computer code in Fortran platform and results are compared with Fluent commercial code and experimental method. Governing parameters are Rayleigh numbers (8.105 ≤ Ra ≤ 4 × 106) and inclination angle (30° ≤ and ≤ 120°). The temperature measurements are done by using thermocouples distributed uniformly at the wall of the enclosure. Remarkably good agreement is obtained between the predicted results and experimental data. A correlation is also developed including all effective parameters on heat transfer and fluid flow. It was observed that heat transfer can be controlled by attaching an inclined fin onto wall.

Heat Transfer Engineering, 2011

The main purpose of this numerical study is to investigate the effects of inclination angle and n... more The main purpose of this numerical study is to investigate the effects of inclination angle and non-isothermal wall boundary conditions in a partially open cavity filled with a porous medium.

Expert Systems With Applications, 2011

An artificial neural network (ANN) model was used to estimate the solar radiation parameters for ... more An artificial neural network (ANN) model was used to estimate the solar radiation parameters for seven cities from Mediterranean region of Anatolia in Turkey. As well known that Turkey is a bridge between Asia and Europe and it lies in a sunny belt, between 36°and 42°N latitudes. Indeed, the country has sufficient solar radiation intensities for solar applications. In order to make estimation of solar radiation, the data from the Turkish State and Meteorological Service were used. Data of 2006 were used for testing and data of 2005, 2007, and 2008 were estimated. Effects of number of input parameters were tested on solar radiation that was output layer. With this aim, number of input layer parameters changed from 2 to 6. The obtained results indicated that the method could be used by researchers or scientists to design high efficiency solar devices. It was also found that number of input parameters was the most effective parameter on estimation of future data on solar radiation.

Expert Systems With Applications, 2010

The performance of a solar collector system using sodium carbonate decahydrate ðNa 2 CO 3 Á10H 2 ... more The performance of a solar collector system using sodium carbonate decahydrate ðNa 2 CO 3 Á10H 2 OÞ as Phase Change Material (PCM) was experimentally investigated during March and collector efficiency was compared with those of convectional system including no PCM. We also made a series of predictions by using three different soft computing techniques as Artificial Neural Networks (ANN), Adaptive-Network-Based Fuzzy Inference System (ANFIS) and Support Vector Machines (SVM). It was found that the solar collector system with PCM is more effective than convectional systems. Soft computing techniques can be used to model of a solar collector with PCM. Furthermore, analysis of soft computing showed that SVM technique gives the best results than that of ANFIS and ANN.

Building and Environment, 2007

Buoyancy induced natural convection is investigated with a numerical technique in Gambrel roofs. ... more Buoyancy induced natural convection is investigated with a numerical technique in Gambrel roofs. The geometry adapted to both winter day conditions, the bottom is hot temperature while top is cold, and summer day conditions, bottom is cold and inclined top wall is hot temperature. Governing equations in streamfunction-vorticity form are solved with finite difference technique and algebraic equations are solved using successive under relaxation (SUR) method. Rayleigh number is taken as parameter which affects the flow and heat transfer. Its value changes between 10 3 and 10 7 . It is found that winterlike boundary conditions are more effective than summerlike boundary conditions on the flow field and heat transfer in the roof. r

International Communications in Heat and Mass Transfer, 2007

The effect of Prandtl number on natural convection heat transfer and fluid flow in triangular enc... more The effect of Prandtl number on natural convection heat transfer and fluid flow in triangular enclosures with localized heating has been analyzed by solving governing equations of natural convection in streamfunction-vorticity form with finite-difference technique. Solution of linear algebraic equations was made by Successive Under Relaxation (SUR) method. Bottom wall of triangle is heated partially while inclined wall is maintained at a lower uniform temperature than heated wall while remaining walls are insulated. Computations were carried out for dimensionless heater locations (0.15 ≤ s ≤ 0.95), dimensionless heater length (0.1 ≤ w ≤ 0.9), Prandtl number (0.01 ≤ Pr ≤ 15) and Rayleigh number (10 3 ≤ Ra ≤ 10 6 ). Aspect ratio of triangle was chosen as unity. It is observed that both flow and temperature fields are affected with the changing of Prandtl number, location of heater and length of heater as well as Rayleigh number.

Journal of Applied Sciences, 2006

Applied Thermal Engineering, 2009

The phenomena of natural convection in an inclined square enclosure heated via corner heater have... more The phenomena of natural convection in an inclined square enclosure heated via corner heater have been studied numerically. Finite difference method is used for solving momentum and energy equations in the form of stream function-vorticity. One wall of the enclosure is isothermal but its temperature is colder than that of heaters while the remaining walls are adiabatic. The numerical procedure adopted in this analysis yields consistent performance over a wide range of parameters; Rayleigh number, Ra (10 3 6 Ra 6 10 6 ); Prandtl number, Pr (0.07 6 Pr 6 70); dimensionless lengths of heater in x and y directions (0.25 6 hx 6 0.75, 0.25 6 hy 6 0.75); and inclination angle, / (0°6 / 6 270°). It is observed that heat transfer is maximum or minimum depending on the inclination angle and depending on the length of the corner heaters. The effect of Prandtl number on mean Nusselt number is more significant for Pr < 1.

International Journal of Heat and Mass Transfer, 2009

Numerical analyses of the flow and heat transfer due to buoyancy forces in a square enclosure div... more Numerical analyses of the flow and heat transfer due to buoyancy forces in a square enclosure divided by an impermeable partition between air and water filled chests were carried out using a finite difference technique. The enclosure was heated from left wall and cooled from right, isothermally. Horizontal walls were adiabatic. The partition divided the enclosure into air and water regions. Thus, two cases were examined: left side of partition was filled with air and right side was filled with water (Case I, air-partition-water) and left side was filled with water and right side with air (Case II, water-partition-air). Epoxy was chosen as partition material. Results were obtained for different Grashof numbers (10 3 6 Gr 6 10 6 ), thickness of the partition (0.05 6 e 6 0.2) and location of the partition (0.25 6 c 6 0.75). An analytical treatment has been performed for low Grashof numbers. Numerical and analytical results gave an acceptable agreement. It was found that filling of fluid into chests is important for obtaining maximum heat transfer and energy saving. When left chest was filled with air (Case I), higher heat transfer was formed. It was an interesting result that heat transfer decreased with increasing of location of the partition for all values of partition thickness at Case I. On the contrary, heat transfer was a decreasing function of increasing value of location of the partition.

Computers & Mathematics With Applications, 2008

A numerical study has been carried out on partially heated triangular enclosures with eave. The e... more A numerical study has been carried out on partially heated triangular enclosures with eave. The eave and inclined wall has a cold temperature. The laminar, two-dimensional, steady governing equations of natural convection are solved in the streamfunction-vorticity form using a finite difference technique. Streamline, isotherm and Nusselt number are presented for different parameters such as aspect ratio AR = H/L from 0.25 to 1, ratio of eave length E = L/n where n changes from 3 to 7 and Rayleigh number from 10 3 to 10 6 . It is observed that the heat transfer decreases with increasing aspect ratio for small Rayleigh number but increases for higher Rayleigh number. Heat transfer also increases with decreasing eave length.

Journal of Applied Sciences, 2007

In the practical applications, roofs of buildings can be in different shapes depending on archite... more In the practical applications, roofs of buildings can be in different shapes depending on architectural design of building or climate. Some of these building roofs can be classified as gambrel, saltbox and gable roofs. In the present study, we investigated the natural convection heat transfer and fluid flow inside the gambrel, gable and saltbox roofs for winter boundary conditions. With this aim, the identified roofs are compared with each other from the heat transfer and flow field point of view. Effects of Rayleigh number also tested in each type. Results are presented with streamlines, isotherms, local and mean Nusselt numbers. It is aimed that this study will help for designer to show more efficient ways of saving energy.

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International Communications in Heat and Mass Transfer, 2009

International Communications in Heat and Mass Transfer, 2010

Laminar natural convection in inclined enclosures filled with different fluids was studied by a n... more Laminar natural convection in inclined enclosures filled with different fluids was studied by a numerical method. The enclosure was divided by a solid impermeable divider. One side of partition of enclosure was filled with air and the other side had water. The enclosure was heated from one vertical wall and cooled from the other while horizontal walls were adiabatic. The governing equations which were written in stream function-vorticity form were solved using a finite difference technique. Results were presented by streamlines, isotherms, mean and local Nusselt numbers for different thermal conductivity ratios of solid impermeable material (plywood or concrete), inclination angle (0°≤ ϕ ≤ 360°) and Grashof numbers (10 3 ≤ Gr ≤ 10 6 ). The code was validated by earlier studies, which are available in the literature on conjugate natural convection heat transfer. Analytical solutions were obtained for low Grashof numbers. Obtained results showed that both heat transfer and flow strength strongly depended on thermal conductivity ratio of the solid material of partition, inclination angle and Grashof numbers. The heat transfer was lower in the air side of the enclosure than that of the water side.

Applied Thermal Engineering, 2008

A numerical analysis of the entropy production has been performed due to natural convection heat ... more A numerical analysis of the entropy production has been performed due to natural convection heat transfer and fluid flow in isosceles triangular enclosures with partially heated from below and symmetrically cooled from sloping walls. Governing equations are solved by finite difference method. Governing parameters on flow and temperature fields are Rayleigh number (10 3 6 Ra 6 8.8 · 10 5 ), dimensionless length of heater (0.25 6 (' 0 = '/L) 6 1.0), dimensionless location of heater (0.25 6 (c 0 = c/L) 6 0.75) and inclination angle of slopping walls (30°6 b 6 60°). Heat transfer results are presented in terms of local and mean Nusselt numbers (Nu) while entropy production results are shown with entropy production number (N s ) and Bejan number (Be). Isotherms, streamlines, contours of entropy production due to heat transfer and fluid friction irreversibility are plotted. It is observed that entropy production number increases but Bejan number decreases with increasing of Rayleigh number. However, both entropy production due to heat transfer and fluid friction irreversibility are affected by higher inclination angle of triangle and length of heater.

International Communications in Heat and Mass Transfer, 2010

A numerical work has been performed to analyze the heat transfer and fluid flow in a pent-roof ty... more A numerical work has been performed to analyze the heat transfer and fluid flow in a pent-roof type combustion chamber. Dynamic mesh model was used to simulation piston intake stroke. Revolution of piston (1000 ≤ n ≤ 5000) is the main governing parameter on heat and fluid flow. k-ε turbulence model was used to predict the flow in the cylinder of a non-compressing fluid. They were solved with finite volume method and FLUENT 12.0 commercial code. Velocity profiles, temperature distribution, pressure distribution and velocity vectors are presented. It is found that the inclined surface of pent-roof type of combustion chamber reduces the swirl effect and it can be a control parameter for heat and fluid flow.

Renewable Energy, 2008

Analysis of energy and exergy has been performed for a latent heat storage system with phase chan... more Analysis of energy and exergy has been performed for a latent heat storage system with phase change material (PCM) for a flat-plate solar collector. CaCl 2 Á 6H 2 O was used as PCM in thermal energy storage (TES) system. The designed collector combines in single unit solar energy collection and storage. PCMs are stored in a storage tank, which is located under the collector. A special heat transfer fluid was used to transfer heat from collector to PCM. Exergy analysis, which is based on the second law of thermodynamics, and energy analysis, which is based on the first law, were applied for evaluation of the system efficiency for charging period. The analyses were performed on 3 days in October. It was observed that the average net energy and exergy efficiencies are 45% and 2.2%, respectively.

International Communications in Heat and Mass Transfer, 2006

Natural convection heat transfer has been analyzed numerically in a triangle enclosure with flush... more Natural convection heat transfer has been analyzed numerically in a triangle enclosure with flush mounted heater on vertical wall. Finite difference method is used in solution of governing equations in streamfunction-vorticity form and linear algebraic equations were solved via Successive Under Relaxation (SUR). Governing parameters on heat transfer and flow fields are aspect ratio of triangle, location of heater, length of heater and Rayleigh number. It is observed that the most important parameter on heat transfer and flow field is the position of heater which can be a control parameter for the present system.

International Communications in Heat and Mass Transfer, 2008

Entropy generation due to conjugate natural convection heat transfer and fluid flow has been stud... more Entropy generation due to conjugate natural convection heat transfer and fluid flow has been studied inside an enclosure with bounded by two solid massive walls from vertical sides at different thicknesses. Enclosure is differentially heated from vertical walls and horizontal walls are adiabatic. Governing equations which are written in streamfunction-vorticity form solved by finite difference technique for the governing parameters as Rayleigh number, 10 3 ≤ Ra ≤ 10 6 , length ratio of solid walls as ɛ 1 (for left vertical wall) and ɛ 2 (for right vertical wall) and thermal conductivity ratio of solid to fluid (k), 1 ≤ k ≤ 10. Entropy generation contours due to fluid friction and heat transfer irreversibility, isotherms, streamlines, Nusselt numbers and velocity profiles were obtained. It is found that entropy generation increases with increasing of thermal conductivity ratio and thicknesses of the walls. Entropy generation due to heat transfer is more significant than that of fluid flow irreversibility for all values of thickness of the solid vertical walls.

International Communications in Heat and Mass Transfer, 2011

Heat and Mass Transfer, 2011

Natural convection heat transfer in an inclined fin attached square enclosure is studied both exp... more Natural convection heat transfer in an inclined fin attached square enclosure is studied both experimentally and numerically. Bottom wall of enclosure has higher temperature than that of top wall while vertical walls are adiabatic. Inclined fin has also adiabatic boundary conditions. Numerical solutions have been done by writing a computer code in Fortran platform and results are compared with Fluent commercial code and experimental method. Governing parameters are Rayleigh numbers (8.105 ≤ Ra ≤ 4 × 106) and inclination angle (30° ≤ and ≤ 120°). The temperature measurements are done by using thermocouples distributed uniformly at the wall of the enclosure. Remarkably good agreement is obtained between the predicted results and experimental data. A correlation is also developed including all effective parameters on heat transfer and fluid flow. It was observed that heat transfer can be controlled by attaching an inclined fin onto wall.

Heat Transfer Engineering, 2011

The main purpose of this numerical study is to investigate the effects of inclination angle and n... more The main purpose of this numerical study is to investigate the effects of inclination angle and non-isothermal wall boundary conditions in a partially open cavity filled with a porous medium.