Ahmed Al-Sammarraie Avatar

Ahmed Al-Sammarraie

PhD Candidate at UC Riverside

Experienced PhD Candidate and Researcher in Thermal Management at the University of California, Riverside with a demonstrated history of working in the higher education industry. Skilled in Research, Data Analysis, and Teaching. Strong research professional with a Master’s Degree focused in Mechanical Engineering (Thermofluids).

experience

Lecturer  
College of Engineering, Tikrit University, November 2002 to July 2013, Tikrit Iraq
(Education)
Developed and taught five courses: Heat Transfer, Industrial Engineering, Calculus, Engineering Drawing, Fundamentals of Power Plants. Administered and taught two laboratories: Fluid Mechanics, Heat Transfer. Mentored and supervised on four undergraduate research projects.

education

University of California, Riverside  
Doctor of Philosophy, Mechanical Engineering, Sep, 2014 to Present


Tikrit University  
Master Of Science, Mechanical Engineering, Oct, 1999 to Jul, 2002


Tikrit University  
Bachelor Of Science, Mechanical Engineering, Oct, 1995 to Jul, 1999


publications

Heat transfer augmentation through convergence angles in a pipe     
Published by (Numerical Heat Transfer; Part A: Applications)
Authors: Ahmed Al-Sammarraie and Kambiz Vafai.  Published August 07, 2017

Forced convection in a combined entry developing length of a convergent pipe under constant wall heat flux boundary condition is performed in this work. Influences of the convergence angle, Reynolds, and Prandtl numbers on the heat transfer and flow field have been investigated. The numerical results are obtained for a wide range of convergence angles (0°–25°), Reynolds numbers (700–2100), and Prandtl numbers (0.707, 5.83). Compared to a traditional pipe, a substantial increase in heat transfer has been achieved with an increase in the pressure drop as the convergence angle increases. In this work, the effect of convergence angle, Reynolds number, and Prandtl number on the overall flow and thermal performance for the aforementioned configuration is investigated. To the best of authors’ knowledge, this investigation has been done for the first time, and it provides new and significant information regarding heat transfer enhancement utilizing a convergent pipe.

Theoretical Study of Heat Transfer through a Sun Space Filled with a Porous Medium     
Published by (Tikrit Journal of Engineering Science (TJES))
Authors: Ahmed Al-Sammarraie and Manar Mahdi.  Published March 01, 2016

A theoretical study had been conducted to detect the effect of using a porous medium in sunspace to reduce heating load and overcoming coldness of winter in the cold regions. In this work, the heat transferred and stored in the storage wall was investigated. The mathematical model was unsteady, heat conduction equation with nonlinear boundary conditions was solved by using finite difference method and the solution technique of heat conduction had based on the Crank Nicholson method. The results had adopted on the aspect ratio (H/L=30), Darcy number (Da=10-3), porosity (φ=0.35) and particle to fluid thermal conductivity ratio (kp/kf=38.5). The results showed that using the porous medium had enhanced the heat transferred and stored in the storage wall. For the outside storage wall temperature, an increase of 19.7% was achieved by using the porous medium instead of the air, while it was 20.3% for the inside storage wall temperature.

Natural Convection Heat Transfer from Two Parallel Horizontal Cylinders Embedded in a Porous Medium inside a Horizontal     
Published by (Wulfenia)
Authors: Ahmed Al-Sammarraie.  Published March 01, 2013

Natural convection heat transfer from two parallel horizontal cylinders embedded in a porous medium inside a horizontal cylindrical enclosure has been experimentally studied, under constant surface temperature boundary condition. The study has investigated the effects of medium Rayleigh number, rotation angle and spacing between two cylinders on their heat loss ability. The experimental rig consists of water container, test section and two copper cylinders with 19 mm diameter. The two cylinders embedded in a porous medium (alumina granules), with a particle diameter rate (3.818 mm). The experiments were done at the range of medium Rayleigh numbers between (1.6 < Ra <18.1), cylinders rotation angles (th= 0, 45, 90) and spacing ratios (S/D= 2, 2.5, 3). The study has clearly shown that the heat loss ability is a function of medium Rayleigh number, cylinders rotation angle and spacing between them. It is noticed that this ability increased with increase of the medium Rayleigh number and reaches the maximum value at the first and second cylinder (th-, th+) at spacing ratio (S/D=3) and minimum value at spacing ratio (S/D=2) at rotation angle (th=-45, -90) for the first and (th= 0,+90) for second cylinder, respectively. The experimental results are related by two correlating equations each one explains the dimensionless relationship of natural convection heat transfer from each cylinder that represented by Nusselt number against medium Rayleigh number, rotation angle and spacing ratio.

Mixed Convection Heat Transfer in Inclined Tubes with Constant Heat Flux     
Published by (European Journal of Scientific Research)
Authors: Ahmed Al-Sammarraie, Raaid R. Jassem and Thamir K. Ibrahim.  Published February 01, 2013

Mixed convection heat transfer in inclined tubes of circular cross section has been experimentally studied for assisting, thermally developing and thermally fully developed laminar-to-turbulent air flows, under constant wall heat flux boundary condition, at Reynolds numbers (Re<2300) for the laminar and (2300<Re<4000) for transition-toturbulent air flows, and the heat flux is varied from 492 to 1442 W/m2. The mixed convection regime has been bounded by the convenient selection of Reynolds number range and the heat flux range so that the obtained Richardson number (Ri) is varied approximately from 0.146 to 1.058. The experimental rig consists of three copper tubes as test section with 600 mm heated length and length to diameter ratio (L/D= 11.8, 15.75 and 31.5). This study has investigated the effect of the heat flux, diameters and inclination angle of the tube on the mixed convection heat transfer process. In this search, the local Nusselt numbers (Nu) with the dimensionless axial distance (Z) are presented. The results have clearly shown that an increase in the Nusselt number values as the heat flux increases and as the tube inclination angle moves from (q = 60°) to (q = 30°), vice versa the Nusselt number decrease with effect of increase the length to diameter ratio (L/D). For the range of Reynolds numbers used in experiments, the maximum Nusselt number has occurred at about 30° inclination relative to the horizon. Present experimental results have a good agreement with previous results obtained for similarly tubes inclination angles. Based on the experimental results, the average Nusselt number ( Nu ) has been correlated in an empirical equation with the effect of the Rayleigh number, Reynolds number, length to diameter ratio and inclination angle. Good agreement can be seen between the experimental results and this equation.

Experimental Study on Natural Convection Heat Transfer From two Parallel Horizontal Cylinders in Horizontal Cylindrical     
Published by (Tikrit Journal of Engineering Science (TJES))
Authors: Ahmad T. Ahmad.  Published March 01, 2010

An experimental study on natural convection heat transfer from two parallel horizontal cylinders in horizontal cylindrical enclosure was carried out under condition of constant surfaces temperature for two cylinders and cylindrical enclosure. The study included the effect of Rayleigh number, rotation angle that represent the confined angle between the passing horizontal plane in cylindrical enclosure center and passing line in two cylinders centers, and the spaces between two cylinders on their heat loss ability. An experimental set-up was used for this purpose which consist water container, test section which is formed of plastic cylinder that represent the cylindrical enclosure, and two heating elements which are formed of two copper cylinders with (19 mm) in diameters heated internally by electrical sources that represents transfer and heat loss elements through this set-up. The experiments were done at the range of Rayleigh number between (3000 < Ra < 36000 ), cylinders rotation angle at (th= 0 ,45 ,90), and spacing ratio at ( S /D= 2,2.5,3). The study showed that the ability of heat loss from two cylinders is a function of Rayleigh number, cylinders rotation angle, and the spaces between them. This ability is increased by increasing of Rayleigh number and it was showed that this ability reaches maximum value at the first cylinder (th-) and minimum value at the second cylinder (th+) at spacing ratio (S/D=3) and rotation angle (th=-45 ,-90 ) for the first and (th=+45 ,+90 ) for the second cylinder respectively. The effective variables on natural convection heat transfer from the above two cylinders are related by two correlating equations, each one explains dimensionless relation of heat transfer from each cylinder that represented by Nusselt number against Rayleigh number, rotation angle, and the spacing ratio between two cylinders.

Numerical Study of Non-Darcian Natural Convection Heat Transfer in a Rectangular Enclosure Filled with Porous Medium Sat     
Published by (Tikrit Journal of Engineering Science (TJES))
Authors: Mahmood H. Ali, Ahmed Tawfiq Ahmed, and Khalaf Ibraheem Hamada.  Published June 01, 2008

A numerical study of non-Darcian natural convection heat transfer in a rectangular enclosure filled with porous medium saturated with viscous fluid was carried out. The effects of medium Rayleigh number, porosity, particle to fluid thermal conductivity ratio, Darcy number and enclosure aspect ratio on heat transfer were examined to demonstrate the ability of using this construction in thermal insulation of buildings walls. A modified Brinkman-Forchheimer-extended Darcy flow model was used and no-slip boundary conditions were imposed for velocity at the walls and the governing equations were expressed in dimensionless stream function, vorticity, and temperature formulation. The resulting algebraic equations obtained from finite difference discritization of vorticity and temperature equations are solved using (ADI) method which uses Three Diagonal Matrix Algorithm (TDMA) in each direction, while that of the stream function equation solved using successive iteration method.The study was done for the range of enclosure aspect ratio (2<H/L<30) which is in the tall layers region at medium Rayleigh number (5<Ram<2000), Darcy number (Da=10-3, 10-4, 10-5 ), porosity (e= 0.35, 0.45, 0.55), particle to fluid thermal conductivity (kS/kf=5.77, 38.5, 1385.5).The results showed that the Nusselt number is direct proportional to medium Rayleigh number and porosity and reversely proportional to Darcy number, ratio of particle to fluid thermal conductivity and enclosure aspect ratio. The variables that affect the heat transfer in the above arrangement was correlated in a mathematical equation that account better for their affects on heat transfer which is represented by mean Nusselt number (Nu).

An Experimental Study on Forced Convection Heat Transfer From An Embedded Horizontal Cylinders Array in A Porous Medium     
Published by (Tikrit Journal of Engineering Science (TJES))
Authors: Mohanad A. Al-Dhaher, Mohammed H. Al-Mosawi, and Ahmed T. Al-Sammarai.  Published June 01, 2007

An experimental study on forced convection heat transfer from an embedded horizontal cylinders array in a porous medium in cross flow was carried out under constant heated cylinder surface temperature condition. The study included the effect of Peclet number, heated cylinder location in array, and the spaces between cylinders on the heat loss ability from this cylinder, as well as the enhancement in heat transfer rate due to embedding the cylinders array in a porous medium. An experimental set-up was used for this purpose which consists of a blower, air duct, test section, and heating element which is represented by a copper cylinder with a diameter of (12.7 mm) heated internally by an electrical source, which represents transfer and heat loss element through this set-up. The experiments were done at the range of spacing ratios between (1.2 ≤ S / D ≤ 2 ) for the cylinders array consisting of five embedded horizontal cylinders in a porous medium consisted of Alumina granules with a particle diameter rate of (3.938 mm) in a turbulent flow at Peclet numbers between (15 < Pe < 56 ). The study showed that the ability of heated cylinder to heat loss is a function of Peclet number, its location in array, and the spaces between cylinders. This ability is increased by increasing Peclet number, and it was shown that this ability reaches maximum value at the third cylinder in array at a spacing ratio of (S/D=1.6) and also at the fourth cylinder in array at a spacing ratio of (S/D=1.4). Also, it was shown that the heated cylinder at any location in array for almost spacing ratios, there was an increase in the heat transfer as maximum (21%) in comparison with a single embedded cylinder in a porous medium. It was noticed that the maximum enhancement value of heat transfer from a heated cylinder in cylinders array (due to embedding it in a porous medium) was nearly five times the heat that transferred from the same free cylinders array or arrangement at the same flow velocity depending on available data from preceding experimental study.

An Experimental Study on Forced Convection Heat Transfer from a Horizontal Cylinders Array in Cross Flow     
Published by (Tikrit Journal of Engineering Science (TJES))
Authors: Mohanad A. Al-Dhaher, Mohammed H. Al-Mosawi, and Ahmed T. Al-Sammarai.  Published March 01, 2003

An Experimental Study On Forced Convection Heat Transfer From A Heated Cylinder In Free And Embedded Horizontal Cylinder     
Published by (Tikrit University; MSc Thesis)
Authors: Ahmed T. Al-Sammarai.  Published February 01, 2002

An experimental study on forced convection heat transfer from a heated cylinder in free and embedded horizontal cylinders array in a porous medium in cross flow was carried out under constant heated cylinder surface temperature condition. The study included the effect of flow velocity, heated cylinder location in array, and the spaces between cylinders on the heat loss ability from this cylinder, as well as the enhancement in heat transfer rate due to imbedding cylinders array in a porous medium. An experimental set-up was used for this purpose which consist of blower, air duct, test section, and heating element which is represented by a copper cylinder with a (12.7 mm) in diameter heated internally by an electrical source, which represents transfer and heat loss element through this set-up. The experiments were done on two stages, the first stage included the experiments of heat transfer by forced convection from heated cylinder in an array consisted of five free horizontal cylinders in cross flow at the range of spacing ratio between (1.2  S /D 2 ) in a turbulent flow at Reynolds number between (1200 Re  5100). The second stage included the experiments of heat transfer by forced convection from heated cylinder in an array consisted of five embedded horizontal cylinders in a porous medium consisted of Alumina granules with a particle diameter rate of (3.938 mm) in cross flow at the same range of spacing ratio in above, in a turbulent flow at Peclet number between (15 Pe  56). The study showed that the ability of heated cylinder to heat loss is a function of flow velocity, its location in array, and the spaces between cylinders. This ability is increased by increasing of flow velocity and it was showed that this ability reaches maximum value at the third cylinder in array at spacing ratio (S/D=1.6) in both cases of free and embedded cylinders in a porous medium. Also, it was showed that the heated cylinder at any location in array for all most spacing ratio in both cases of free and embedded cylinders there was increasing in heat transfer as maximum (21%) in comparison with a single free or embedded cylinder in a porous medium respectively. It was noticed that the maximum enhancement value of heat transfer from a heated cylinder in cylinders array, due to embedding it in a porous medium, was nearly five times more than heat transfer from the same array in case of free cylinders at the same flow velocity. The effective variables on forced convection heat transfer in the two arrangements above is related by two correlating equations, each one explains heat transfer dimensionless relation that represented by Nusselt number against the spacing ratio and heated cylinder location in array, in addition to Reynolds number in case of free cylinders in cross flow and Peclet number in case of embedded cylinders in a porous medium as the following:

Constructal Design of Circular Multilayer Microchannel Heat Sinks     
Published by (ASME Journal of Thermal Science and Engineering Applications)
Authors: Mohammad Reza Salimpour, Ahmed T. Al-Sammarraie, Azadeh Forouzandeh and Mahsa Farzaneh.  Published September 17, 2018

Based on the constructal theory concepts, an investigation is carried out to optimize circular multilayer microchannels embedded inside a rectangular heat sink with different numbers of layers and flow configurations. The lower surface of the heat sink is uniformly heated, while both pressure drop and length of the microchannel are fixed. Also, the volume of the heat sink is kept fixed for all studied cases, while the effect of solid volume fraction is examined. All the dimensions of microchannel heat sinks are optimized in a way that the maximum temperature of the microchannel heat sink is minimized. The results emphasize that using triple-layer microchannel heat sink under optimal conditions reduces the maximum temperature about 10.3 °C compared to the single-layer arrangement. Further, employing counter flow configuration in double-layer microchannel improves its thermal performance, while this effect is less pronounced in the triple-layer architecture. In addition, it is revealed that the optimal design can be achieved when the upper channels of a multilayer microchannel heat sink have bigger diameters than the lower ones. Finally, it is observed while using two layers of microchannels is an effective means for cooling improvement, invoking more layers is far less effective and hence is not recommended.

Awards

Letter of appreciation
Letter of appreciation from the University President for participating in the university day activities, University of Tikrit, Iraq (Apr. 2012)

Letter of appreciation
Letter of appreciation from the University President for the excellent performance in the 2008-2009 academic year, University of Tikrit, Iraq (Dec. 2009)

Letter of appreciation
Letter of appreciation from the University President for the excellent performance in the 2007-2008 academic year, University of Tikrit, Iraq (Jan. 2009)

Letter of appreciation
Letter of appreciation from the college of engineering Dean for the outstanding performance in the examinations committee, University of Tikrit, Iraq (Aug. 2008)

Letter of appreciation
Letter of appreciation from the college of engineering Dean for the outstanding performance in the examinations committee, University of Tikrit, Iraq (Nov. 2007)