OLA KAMIYO | University Of Lagos, Akoka, Nigeria (original) (raw)

Papers by OLA KAMIYO

West Indian Journal of Engineering

In this study, a finite volume analysis of the aerodynamics and heat transfer in attics of a cler... more In this study, a finite volume analysis of the aerodynamics and heat transfer in attics of a clerestory roof design with pitch angles 14o, 18o, 30o and 45o and Rayleigh number range 3 x 105≤ Ra ≤ 2 x 107 is carried out. The shape of the enclosure has strong influence on the structure of the flow and temperature fields. The flow field is characterised by counter-rotating vortices enclosed by aerodynamic boundary layers. The size, strength and direction of rotation of the cells are controlled by the forces propelling the thermal plumes and the cold jets. The reduction of the number and size of the counter-rotating cells and their formation within the enclosures provide an analogous reduction of the total heat transfer rate as the roof pitch angle increases. The velocity and temperature profiles across midheight and midlength of the enclosures enable the prediction of appropriate position in the attic with the right condition to place sensitive items. On the heat transfer, the relation...

World Scientific News, 2020

Investigation on thermal responses of different materials subjected to variant environmental cond... more Investigation on thermal responses of different materials subjected to variant environmental condition has been a subject of ever-increasing research interest for decades. As such, research studies have shown different materials exhibiting peculiar characteristics of commercially used heat enhancement devices. Therefore, this work presents an investigation on thermal behaviour of a convective porous moving fins with temperature dependent thermal conductivity for five different materials. These materials include copper, Aluminium, Silicon nitride, Silicon carbide and Stainless steel. A hybrid method, viz-Laplace-variational iterative method (LVIM) is used to solve the model equation developed. And a perfect agreement is achieved when the result obtained from LVIM is verified with the exact solution. The result obtained shows that silicon carbide compete favourably with copper as the most efficient material in heat enhancement, while stainless steel shows the least performance. It is hoped that this work will serve as a template and a helpful tool for both scientist and engineers' in future design of fins.

World Scientific News, 2019

Journal of Engineering and Technology, Mar 31, 2011

Sandcrete blocks have been in used in many nations of the world including Nigeria, playing a majo... more Sandcrete blocks have been in used in many nations of the world including Nigeria, playing a major role in the building industry. The material constituents, their mix, presence of admixtures and the manufacturing process are important factors that determine the properties of sandcrete blocks. This paper investigates the effects of a partial replacement of cement with rice husk ash (RHA) on some engineering properties of hollow sandcrete blocks with 1:6 cement-sand mix ratios. Single block size 225 x 225 x 450 mm, is produced with a vibrating machine. Results show that the addition of RHA produces blocks of lower density. Particularly, the density of the blocks decreases as the RHA content increases. The compressive strength of the block is also not enhanced. Results also reveal that the thermal and hygrothermal properties of the blocks are significantly affected.

Most buildings in many nations of the world including African countries are built with porous mat... more Most buildings in many nations of the world including African countries are built with porous materials especially sandcrete blocks. It has been observed that various factors including presence of admixtures affect the engineering properties of the blocks. Recent reports show that admixtures are being introduced into these blocks to achieve different purposes including cost reduction and strength enhancement. In the process, some vital properties are traded-off. Prominent among these traded-off properties apply to the thermal characteristics of the blocks which determine the thermal comfort within the built space in addition to energy conservation and other environmental consequences. This paper reports the effects of percentage substitution of the constituents of sandcrete block with coconut husk ash, crushed glass, and granite fines on its thermophysical properties. It was observed that the presence of the admixtures slightly increases the thermal conductivity and the thermal diff...

ithin the framework of occupational prestige assessment, a survey was carried out amongst future ... more ithin the framework of occupational prestige assessment, a survey was carried out amongst future engineers in Nigeria to determine their perception of engineering profession relative to a range of occupations. A questionnaire was administered to 100 undergraduate gineering students. Eight occupations were rated on six dimensions, i.e. levels of _ telligence required, income, social status, responsibility, relevance or usefulness to the iety, and the proportion of women. The results indicate that future engineers in Nigeria lieve their profession possesses relatively high social status, together with Bank Manager d Medical Doctor, and is differentiated from the proximate professions of Engineering echnologist and Motor Mechanic. These results lead to the conclusion that engineering in .zeria is held in high esteem it has a clear identity and professional status, and, with the easing proportion of women, it is likely to be regarded as an equally desirable future .cupation for both gen...

Most buildings in many nations of the world including African countries are built with porous mat... more Most buildings in many nations of the world including African countries are built with porous materials especially sandcrete blocks. It has been observed that various factors including presence of admixtures affect the engineering properties of such blocks. Recent reports show that admixtures are being introduced into these blocks for different purposes including cost reduction and strength enhancement. In the process, some vital properties are traded-off. Prominent among the trade-offs are their thermal characteristics which indirectly determine the thermal comfort within the built space in addition to energy conservation and other environmental consequences. This paper therefore reports the experimental investigation of the effects of substitution of the constituents of sandcrete block with admixtures such as coconut husk ash, crushed glass, and granite fines on its thermal properties. It was observed that the presence of the admixtures slightly increases the thermal conductivity ...

Engineering and Applied Science Letters, 2019

The performance of fins, commonly used as heat enhancement devices are greatly affected by both t... more The performance of fins, commonly used as heat enhancement devices are greatly affected by both the geometry and material properties. These consideration in fin design has stimulated an extensive research interest in the recent time. In this study, investigation on the thermal responses of moving irregular porous fins with trapezoidal, concave and convex profiles of copper, aluminium, silicon nitrides and stainless steel materials is examined. The developed thermal model is solved using differential transform method (DTM). On the verification of result obtained with numerical method using Runge-Kutta, a good agreement with the solution of approximate method is achieved. In the parametric studies carried out, the effect of physical parameters such as convective-conductive, convective-radiative term, internal heat generation, porosity, surface emissivity, power index of heat transfer coefficient, Peclet number and Darcy number on the thermal behaviour of fins are examined and discussed. The comparative analysis carried out on the effect of materials on non-dimensional temperature distribution reveals that copper obtains the highest temperature while the stainless steel gets the lowest. More-so, the fins with concave geometry gives the highest volume adjusted efficiency with increase in Peclet number while that with convex profile has the least. These result output are essential and would be useful in the future design of fins with optimum size reduction and high efficiency.

Thermal Science and Engineering Progress, 2017

In this study, thermal performance analysis of a natural convection porous fin with temperaturede... more In this study, thermal performance analysis of a natural convection porous fin with temperaturedependent thermal conductivity and internal heat generation operating is carried out using Galerkin's method of weighted residual. The developed symbolic heat transfer models were used to investigate the effects of various parameters on the thermal performance of the porous fin.It is found that increase in porosity parameter, Nusselt, Darcy and Rayleigh numbers and the thickness-length ratio of the fin increase the rate of heat transfer from the base of the fin and consequently improve the efficiency of the fin. Also, decreasing thermal conductivity parameter results in an increase in the rate of heat transfer from the base of the fin. However, an optimum value is reached beyond which further increase in porosity, Nusselt, Darcy and Rayleigh numbers, thermal conductivity ratio and thickness-length ratio has no significant influence on the rate of heat transfer. For the purpose of validation of the results, exact analytical solutions were developed. The results of the Galerkin's method for the second-order approximation function are found to be in excellent agreements with the results of the exact analytical solutions and also with that of the numerical methods and homotopy perturbation method.

International Journal of Thermal Sciences, 2010

The main mechanisms of transition of buoyancy-induced flows in the horizontal annulus between cir... more The main mechanisms of transition of buoyancy-induced flows in the horizontal annulus between circular cylinders are reviewed, based on the available literature. Both experimental and theoretical studies are considered. The different scenarios for the evolution of the flow regimes and temperature patterns are tracked, for increasing values of the Rayleigh number, Ra. The occurrence of various instability and bifurcative phenomena is pointed out, and linked to other relevant parameters, such as the radius ratio R and the Prandtl number, Pr. Although most of the relevant literature is on 2D cases, the effect of the third dimension is considered as far as possible. Studies on the influence of the eccentricity of the inner cylinder on the laminar flow and the thermal asset are also reviewed. Finally, open questions and topics for future research are hinted at.

Open Journal of Mathematical Sciences, 2020

The present study is based on the nonlinear analysis of unsteady magnetohydrodynamics squeezing f... more The present study is based on the nonlinear analysis of unsteady magnetohydrodynamics squeezing flow and heat transfer of a third grade fluid between two parallel disks embedded in a porous medium under the influences of thermal radiation and temperature jump boundary conditions are studied using Chebyshev spectral collocation method. The results of the non-convectional numerical solutions verified with the results of numerical solutions using fifth-order Runge-Kutta Fehlberg-shooting method and also the results of homotopy analysis method as presented in literature. The parametric studies from the series solutions show that for a suction parameter greater than zero, the radial velocity of the lower disc increases while that of the upper disc decreases as a result of a corresponding increase in the viscosity of the fluid from the lower squeezing disc to the upper disc. An increasing magnetic field parameter, the radial velocity of the lower disc decreases while that of the upper disc increases. As the third-grade fluid parameter increases, there is a reduction in the fluid viscosity thereby increasing resistance between the fluid molecules. There is a recorded decrease in the fluid temperature profile as the Prandtl number increases due to decrease in the thermal diffusivity of the third-grade fluid. The results in this work can be used to advance the analysis and study of the behaviour of third grade fluid flow and heat transfer processes such as found in coal slurries, polymer solutions, textiles, ceramics, catalytic reactors, oil recovery applications etc.

Kufa Journal of Engineering

In this study, thermal performance of different pitched roofs with elevated ceiling configuration... more In this study, thermal performance of different pitched roofs with elevated ceiling configuration is analyzed and compared. Three different ceiling shapes, viz., cathedral, barrel-vault and A-frame, at the same pitch angle and ceiling material, under winter heating are examined numerically by solving the steady-state air and heat flow problems simultaneously. In all the roofs, the airflow fields show counter-rotating recirculating cells. The multicellular flow field promotes uniform temperature distribution within the enclosures. Heat loss to the attic from the space below increases with the closeness of the hot ceiling to the cold inclined walls. In the A-frame roof, there is uniform convective heat transfer. But in the cathedral and barrel-vault roofs, near the bottom corners, conductive heat exchange predominates. In all, the thermal performance of the barrel-vault is least while that of the cathedral is best. This observation is useful on the application of insulation when using...

Applied Mechanics Reviews, 2010

Natural convection in triangular enclosures is an important problem. It displays well the generic... more Natural convection in triangular enclosures is an important problem. It displays well the generic attributes of this class of convection, with its dependence on enclosure geometry, orientation and thermal boundary conditions. It is particularly rich in its variety of flow regimes and thermal fields as well as having significant practical application. In this paper, a comprehensive view of the research area is sought by critically examining the experimental and numerical approaches adopted in studies of this problem in the literature. Different thermal boundary conditions for the evolution of the flow regimes and thermal fields are considered. Effects of changes in pitch angle and the Rayleigh number on the flow and thermal fields are examined in detail. Although most of the past studies are in the laminar regime, the review extends up to the recent studies of the low turbulent regime. Finally, areas of further research are highlighted.

Nigerian Journal of Engineering, 2021

THE IRAQI JOURNAL FOR MECHANICAL AND MATERIALS ENGINEERING

Analysis of airflow and thermal characteristics of attics of bobtail-shaped pitched roofs heated ... more Analysis of airflow and thermal characteristics of attics of bobtail-shaped pitched roofs heated through a horizontally suspended ceiling is numerically carried out in this study. Pitch angles of 14o, 18o, 30o, and 45o within the standard pitch roof range are selected. The configuration falls within Rayleigh number 3.19 x 105  Ra  2.04 x 107. A finite-volume CFD code was used to solve the mass, momentum, and energy conservation equations governing the problem. The results obtained indicate a strong influence on the shape and angle of the roof. At lower roof pitches, the flow field is characterized by multiple counter-rotating vortices asymmetrically arranged within the enclosures. Eight cells in the 14o enclosure were reduced to five in the 45o roof pitch. The size and rotating strength of a vortex increase from the left corner to the middle of the enclosures. At higher pitch angles, the vertical wall obstructed the flow leading to a number of distorted cells. The maximum velocity...

Kufa Journal of Engineering, 2021

Natural convective heat transfer in M-shaped roofs has been investigated using CFD approach with ... more Natural convective heat transfer in M-shaped roofs has been investigated using CFD approach with the aim of determining the flowfield and thermal characteristics of the attic when heated through the ceiling for pitch angles 14o, 20o, 25o and 35o and Rayleigh number between 106 and 107. The results show that the ‘M’ shape of the roof has strong influence on the airflow pattern and heat transfer. For all the roof pitches, counterrotating cells with varying intensities and thermal plumes are obtained. The air velocity variation laterally across the attic forms a sequence that mimics the flowfield thus enabling the relative size of a cell and its intensity at a position in an attic of a particular pitch to be predicted. The size of the twin vortices at the central area is found to increase by 4% with the roof pitch. As the pitch increases, the thermal plumes get thicker while their number reduces and heat transfer rate decreases.

Hollow sandcrete blocks are widely used in many countries of the world. In recent years, cement c... more Hollow sandcrete blocks are widely used in many countries of the world. In recent years, cement content is being partially substituted by admixtures especially agricultural wastes. Modeling of heat transfer characteristics of these modified blocks is essential in order to predict their thermal performance. This study focuses on this modeling with the aid of a finite-volume based computer code. Specifically, for regular, two-cavity blocks produced with the cement partially substituted with rice husk ash (RHA). The result showed that as the percentage substitution of RHA increased, thermal gradient across the width of the block increased, while the rate of heat flow reduced. The second part of the study examined the effect of heat transfer through the air-gap as compared to a similar study regarding it as vacuum. The heat flow through the air-gaps of the building bricks affected the pattern of heat flow within the bricks, hence, they could not be regarded as a vacuum. The results of t...

Journal of Physics: Conference Series, 2014

†Prof. Michael Wesley Collins passed on 2014 August 24 th. Among a number of scientific topics he... more †Prof. Michael Wesley Collins passed on 2014 August 24 th. Among a number of scientific topics he cultivated in his brilliant academic career, convection heat transfer was the first and the most beloved.

In this study, by using the finite volume method, the heat transfer in a convective straight fin ... more In this study, by using the finite volume method, the heat transfer in a convective straight fin with temperature-dependent thermal properties and an internal heat generation under multi-boiling heat transfer modes are analyzed. In this regard, the local heat transfer coefficient is considered to vary within a power-law function of temperature. In the present study, the coexistence of all the boiling modes is taken into consideration. The developed heat transfer models and the corresponding numerical solutions are used to investigate the effects of various thermo-geometric parameters on the thermal performance of the longitudinal rectangular fin. The results shows that the fin temperature distribution, the total heat transfer, and the fin efficiency are significantly affected by the thermo-geometric parameters of the fin and the internal heat generation within the fin. The obtained results can provide a platform for improvements in the design of the fin in the heat transfer equipment.

West Indian Journal of Engineering

In this study, a finite volume analysis of the aerodynamics and heat transfer in attics of a cler... more In this study, a finite volume analysis of the aerodynamics and heat transfer in attics of a clerestory roof design with pitch angles 14o, 18o, 30o and 45o and Rayleigh number range 3 x 105≤ Ra ≤ 2 x 107 is carried out. The shape of the enclosure has strong influence on the structure of the flow and temperature fields. The flow field is characterised by counter-rotating vortices enclosed by aerodynamic boundary layers. The size, strength and direction of rotation of the cells are controlled by the forces propelling the thermal plumes and the cold jets. The reduction of the number and size of the counter-rotating cells and their formation within the enclosures provide an analogous reduction of the total heat transfer rate as the roof pitch angle increases. The velocity and temperature profiles across midheight and midlength of the enclosures enable the prediction of appropriate position in the attic with the right condition to place sensitive items. On the heat transfer, the relation...

World Scientific News, 2020

Investigation on thermal responses of different materials subjected to variant environmental cond... more Investigation on thermal responses of different materials subjected to variant environmental condition has been a subject of ever-increasing research interest for decades. As such, research studies have shown different materials exhibiting peculiar characteristics of commercially used heat enhancement devices. Therefore, this work presents an investigation on thermal behaviour of a convective porous moving fins with temperature dependent thermal conductivity for five different materials. These materials include copper, Aluminium, Silicon nitride, Silicon carbide and Stainless steel. A hybrid method, viz-Laplace-variational iterative method (LVIM) is used to solve the model equation developed. And a perfect agreement is achieved when the result obtained from LVIM is verified with the exact solution. The result obtained shows that silicon carbide compete favourably with copper as the most efficient material in heat enhancement, while stainless steel shows the least performance. It is hoped that this work will serve as a template and a helpful tool for both scientist and engineers' in future design of fins.

World Scientific News, 2019

Journal of Engineering and Technology, Mar 31, 2011

Sandcrete blocks have been in used in many nations of the world including Nigeria, playing a majo... more Sandcrete blocks have been in used in many nations of the world including Nigeria, playing a major role in the building industry. The material constituents, their mix, presence of admixtures and the manufacturing process are important factors that determine the properties of sandcrete blocks. This paper investigates the effects of a partial replacement of cement with rice husk ash (RHA) on some engineering properties of hollow sandcrete blocks with 1:6 cement-sand mix ratios. Single block size 225 x 225 x 450 mm, is produced with a vibrating machine. Results show that the addition of RHA produces blocks of lower density. Particularly, the density of the blocks decreases as the RHA content increases. The compressive strength of the block is also not enhanced. Results also reveal that the thermal and hygrothermal properties of the blocks are significantly affected.

Most buildings in many nations of the world including African countries are built with porous mat... more Most buildings in many nations of the world including African countries are built with porous materials especially sandcrete blocks. It has been observed that various factors including presence of admixtures affect the engineering properties of the blocks. Recent reports show that admixtures are being introduced into these blocks to achieve different purposes including cost reduction and strength enhancement. In the process, some vital properties are traded-off. Prominent among these traded-off properties apply to the thermal characteristics of the blocks which determine the thermal comfort within the built space in addition to energy conservation and other environmental consequences. This paper reports the effects of percentage substitution of the constituents of sandcrete block with coconut husk ash, crushed glass, and granite fines on its thermophysical properties. It was observed that the presence of the admixtures slightly increases the thermal conductivity and the thermal diff...

ithin the framework of occupational prestige assessment, a survey was carried out amongst future ... more ithin the framework of occupational prestige assessment, a survey was carried out amongst future engineers in Nigeria to determine their perception of engineering profession relative to a range of occupations. A questionnaire was administered to 100 undergraduate gineering students. Eight occupations were rated on six dimensions, i.e. levels of _ telligence required, income, social status, responsibility, relevance or usefulness to the iety, and the proportion of women. The results indicate that future engineers in Nigeria lieve their profession possesses relatively high social status, together with Bank Manager d Medical Doctor, and is differentiated from the proximate professions of Engineering echnologist and Motor Mechanic. These results lead to the conclusion that engineering in .zeria is held in high esteem it has a clear identity and professional status, and, with the easing proportion of women, it is likely to be regarded as an equally desirable future .cupation for both gen...

Most buildings in many nations of the world including African countries are built with porous mat... more Most buildings in many nations of the world including African countries are built with porous materials especially sandcrete blocks. It has been observed that various factors including presence of admixtures affect the engineering properties of such blocks. Recent reports show that admixtures are being introduced into these blocks for different purposes including cost reduction and strength enhancement. In the process, some vital properties are traded-off. Prominent among the trade-offs are their thermal characteristics which indirectly determine the thermal comfort within the built space in addition to energy conservation and other environmental consequences. This paper therefore reports the experimental investigation of the effects of substitution of the constituents of sandcrete block with admixtures such as coconut husk ash, crushed glass, and granite fines on its thermal properties. It was observed that the presence of the admixtures slightly increases the thermal conductivity ...

Engineering and Applied Science Letters, 2019

The performance of fins, commonly used as heat enhancement devices are greatly affected by both t... more The performance of fins, commonly used as heat enhancement devices are greatly affected by both the geometry and material properties. These consideration in fin design has stimulated an extensive research interest in the recent time. In this study, investigation on the thermal responses of moving irregular porous fins with trapezoidal, concave and convex profiles of copper, aluminium, silicon nitrides and stainless steel materials is examined. The developed thermal model is solved using differential transform method (DTM). On the verification of result obtained with numerical method using Runge-Kutta, a good agreement with the solution of approximate method is achieved. In the parametric studies carried out, the effect of physical parameters such as convective-conductive, convective-radiative term, internal heat generation, porosity, surface emissivity, power index of heat transfer coefficient, Peclet number and Darcy number on the thermal behaviour of fins are examined and discussed. The comparative analysis carried out on the effect of materials on non-dimensional temperature distribution reveals that copper obtains the highest temperature while the stainless steel gets the lowest. More-so, the fins with concave geometry gives the highest volume adjusted efficiency with increase in Peclet number while that with convex profile has the least. These result output are essential and would be useful in the future design of fins with optimum size reduction and high efficiency.

Thermal Science and Engineering Progress, 2017

In this study, thermal performance analysis of a natural convection porous fin with temperaturede... more In this study, thermal performance analysis of a natural convection porous fin with temperaturedependent thermal conductivity and internal heat generation operating is carried out using Galerkin's method of weighted residual. The developed symbolic heat transfer models were used to investigate the effects of various parameters on the thermal performance of the porous fin.It is found that increase in porosity parameter, Nusselt, Darcy and Rayleigh numbers and the thickness-length ratio of the fin increase the rate of heat transfer from the base of the fin and consequently improve the efficiency of the fin. Also, decreasing thermal conductivity parameter results in an increase in the rate of heat transfer from the base of the fin. However, an optimum value is reached beyond which further increase in porosity, Nusselt, Darcy and Rayleigh numbers, thermal conductivity ratio and thickness-length ratio has no significant influence on the rate of heat transfer. For the purpose of validation of the results, exact analytical solutions were developed. The results of the Galerkin's method for the second-order approximation function are found to be in excellent agreements with the results of the exact analytical solutions and also with that of the numerical methods and homotopy perturbation method.

International Journal of Thermal Sciences, 2010

The main mechanisms of transition of buoyancy-induced flows in the horizontal annulus between cir... more The main mechanisms of transition of buoyancy-induced flows in the horizontal annulus between circular cylinders are reviewed, based on the available literature. Both experimental and theoretical studies are considered. The different scenarios for the evolution of the flow regimes and temperature patterns are tracked, for increasing values of the Rayleigh number, Ra. The occurrence of various instability and bifurcative phenomena is pointed out, and linked to other relevant parameters, such as the radius ratio R and the Prandtl number, Pr. Although most of the relevant literature is on 2D cases, the effect of the third dimension is considered as far as possible. Studies on the influence of the eccentricity of the inner cylinder on the laminar flow and the thermal asset are also reviewed. Finally, open questions and topics for future research are hinted at.

Open Journal of Mathematical Sciences, 2020

The present study is based on the nonlinear analysis of unsteady magnetohydrodynamics squeezing f... more The present study is based on the nonlinear analysis of unsteady magnetohydrodynamics squeezing flow and heat transfer of a third grade fluid between two parallel disks embedded in a porous medium under the influences of thermal radiation and temperature jump boundary conditions are studied using Chebyshev spectral collocation method. The results of the non-convectional numerical solutions verified with the results of numerical solutions using fifth-order Runge-Kutta Fehlberg-shooting method and also the results of homotopy analysis method as presented in literature. The parametric studies from the series solutions show that for a suction parameter greater than zero, the radial velocity of the lower disc increases while that of the upper disc decreases as a result of a corresponding increase in the viscosity of the fluid from the lower squeezing disc to the upper disc. An increasing magnetic field parameter, the radial velocity of the lower disc decreases while that of the upper disc increases. As the third-grade fluid parameter increases, there is a reduction in the fluid viscosity thereby increasing resistance between the fluid molecules. There is a recorded decrease in the fluid temperature profile as the Prandtl number increases due to decrease in the thermal diffusivity of the third-grade fluid. The results in this work can be used to advance the analysis and study of the behaviour of third grade fluid flow and heat transfer processes such as found in coal slurries, polymer solutions, textiles, ceramics, catalytic reactors, oil recovery applications etc.

Kufa Journal of Engineering

In this study, thermal performance of different pitched roofs with elevated ceiling configuration... more In this study, thermal performance of different pitched roofs with elevated ceiling configuration is analyzed and compared. Three different ceiling shapes, viz., cathedral, barrel-vault and A-frame, at the same pitch angle and ceiling material, under winter heating are examined numerically by solving the steady-state air and heat flow problems simultaneously. In all the roofs, the airflow fields show counter-rotating recirculating cells. The multicellular flow field promotes uniform temperature distribution within the enclosures. Heat loss to the attic from the space below increases with the closeness of the hot ceiling to the cold inclined walls. In the A-frame roof, there is uniform convective heat transfer. But in the cathedral and barrel-vault roofs, near the bottom corners, conductive heat exchange predominates. In all, the thermal performance of the barrel-vault is least while that of the cathedral is best. This observation is useful on the application of insulation when using...

Applied Mechanics Reviews, 2010

Natural convection in triangular enclosures is an important problem. It displays well the generic... more Natural convection in triangular enclosures is an important problem. It displays well the generic attributes of this class of convection, with its dependence on enclosure geometry, orientation and thermal boundary conditions. It is particularly rich in its variety of flow regimes and thermal fields as well as having significant practical application. In this paper, a comprehensive view of the research area is sought by critically examining the experimental and numerical approaches adopted in studies of this problem in the literature. Different thermal boundary conditions for the evolution of the flow regimes and thermal fields are considered. Effects of changes in pitch angle and the Rayleigh number on the flow and thermal fields are examined in detail. Although most of the past studies are in the laminar regime, the review extends up to the recent studies of the low turbulent regime. Finally, areas of further research are highlighted.

Nigerian Journal of Engineering, 2021

THE IRAQI JOURNAL FOR MECHANICAL AND MATERIALS ENGINEERING

Analysis of airflow and thermal characteristics of attics of bobtail-shaped pitched roofs heated ... more Analysis of airflow and thermal characteristics of attics of bobtail-shaped pitched roofs heated through a horizontally suspended ceiling is numerically carried out in this study. Pitch angles of 14o, 18o, 30o, and 45o within the standard pitch roof range are selected. The configuration falls within Rayleigh number 3.19 x 105  Ra  2.04 x 107. A finite-volume CFD code was used to solve the mass, momentum, and energy conservation equations governing the problem. The results obtained indicate a strong influence on the shape and angle of the roof. At lower roof pitches, the flow field is characterized by multiple counter-rotating vortices asymmetrically arranged within the enclosures. Eight cells in the 14o enclosure were reduced to five in the 45o roof pitch. The size and rotating strength of a vortex increase from the left corner to the middle of the enclosures. At higher pitch angles, the vertical wall obstructed the flow leading to a number of distorted cells. The maximum velocity...

Kufa Journal of Engineering, 2021

Natural convective heat transfer in M-shaped roofs has been investigated using CFD approach with ... more Natural convective heat transfer in M-shaped roofs has been investigated using CFD approach with the aim of determining the flowfield and thermal characteristics of the attic when heated through the ceiling for pitch angles 14o, 20o, 25o and 35o and Rayleigh number between 106 and 107. The results show that the ‘M’ shape of the roof has strong influence on the airflow pattern and heat transfer. For all the roof pitches, counterrotating cells with varying intensities and thermal plumes are obtained. The air velocity variation laterally across the attic forms a sequence that mimics the flowfield thus enabling the relative size of a cell and its intensity at a position in an attic of a particular pitch to be predicted. The size of the twin vortices at the central area is found to increase by 4% with the roof pitch. As the pitch increases, the thermal plumes get thicker while their number reduces and heat transfer rate decreases.

Hollow sandcrete blocks are widely used in many countries of the world. In recent years, cement c... more Hollow sandcrete blocks are widely used in many countries of the world. In recent years, cement content is being partially substituted by admixtures especially agricultural wastes. Modeling of heat transfer characteristics of these modified blocks is essential in order to predict their thermal performance. This study focuses on this modeling with the aid of a finite-volume based computer code. Specifically, for regular, two-cavity blocks produced with the cement partially substituted with rice husk ash (RHA). The result showed that as the percentage substitution of RHA increased, thermal gradient across the width of the block increased, while the rate of heat flow reduced. The second part of the study examined the effect of heat transfer through the air-gap as compared to a similar study regarding it as vacuum. The heat flow through the air-gaps of the building bricks affected the pattern of heat flow within the bricks, hence, they could not be regarded as a vacuum. The results of t...

Journal of Physics: Conference Series, 2014

†Prof. Michael Wesley Collins passed on 2014 August 24 th. Among a number of scientific topics he... more †Prof. Michael Wesley Collins passed on 2014 August 24 th. Among a number of scientific topics he cultivated in his brilliant academic career, convection heat transfer was the first and the most beloved.

In this study, by using the finite volume method, the heat transfer in a convective straight fin ... more In this study, by using the finite volume method, the heat transfer in a convective straight fin with temperature-dependent thermal properties and an internal heat generation under multi-boiling heat transfer modes are analyzed. In this regard, the local heat transfer coefficient is considered to vary within a power-law function of temperature. In the present study, the coexistence of all the boiling modes is taken into consideration. The developed heat transfer models and the corresponding numerical solutions are used to investigate the effects of various thermo-geometric parameters on the thermal performance of the longitudinal rectangular fin. The results shows that the fin temperature distribution, the total heat transfer, and the fin efficiency are significantly affected by the thermo-geometric parameters of the fin and the internal heat generation within the fin. The obtained results can provide a platform for improvements in the design of the fin in the heat transfer equipment.