Papers by Asif Ahmed
In the present study, three-dimensional numerical simulation of two shell-and-tube heat exchanger... more In the present study, three-dimensional numerical simulation of two shell-and-tube heat exchangers (STHXs) with conventional segmental baffles (STHXsSB) and continuous helical baffle (STHXsHB) is carried out and a comparative study is performed based on the simulation results. Both of the STHXs contain 37 tubes inside a 500 mm long and 200 mm diameter shell and mass flow rate of shell-side fluid is varied from 0.5 kg/s to 2 kg/s. At first, physical and mathematical models are developed and numerically simulated using finite element method (FEM). For the validation of the computational model, shell-side average nusselt number (Nus) is calculated from the simulation results and compared with the available experimental results. The comparative study shows that STHXsHB has 72-127% higher heat transfer coefficient per unit pressure drop compared to the conventional STHXsSB for the same shell-side mass flow rate. Moreover, STHXsHB has 59-63% lower shell-side pressure drop than STHXsSB.
In the present study, three-dimensional numerical simulations of two segmentally baffled shell-an... more In the present study, three-dimensional numerical simulations of two segmentally baffled shell-and-tube heat exchangers (STHXs) with plain tube bundle (STHXsPT) and annular-finned tube bundle (STHXsFT) are carried out using finite element method (FEM). A comparative study is performed to evaluate the thermal performance and energy efficiency of both types of STHXs based on the simulation results. The results show that STHXsFT has higher shell-side heat transfer coefficient and improved shell-side cross flow characteristics, while STHXsPT has lower shell-side pressure drop. However, STHXsFT has slightly higher heat transfer coefficient per unit pressure drop compared to STHXsPT.
In the present study, three-dimensional numerical simulation of four shell-and-tube heat exchange... more In the present study, three-dimensional numerical simulation of four shell-and-tube heat exchangers (STHXs) with similar dimensions but different baffle configurations is carried out using finite element method (FEM). A comparative study is performed on shell-and-tube heat exchanger with conventional segmental baffles (STHXsSB) and continuous helical baffle (STHXsHB) with different helix angles (ϕ = 25.52̊ , 17.66̊ and 10.81̊) based on the simulation results. At first, validation of the mathematical model is performed by comparing the shell side average Nusselt number with the available experimental data. Reasonably good agreement is obtained and the reasons causing the discrepancy are analyzed. On the other hand, the comparative study shows that STHXsHB with helix angle, ϕ = 25.52̊ has the highest energy efficiency (heat transfer coefficient per unit pressure drop) among the four configurations of STHXs for the same shell-side mass flow rate. However, with decreasing helix angle, performance of STHXsHB deteriorates. Moreover, STHXsSB has the highest heat transfer coefficient and average energy efficiency among all configurations.
Conference Presentations by Asif Ahmed
In the present study, three-dimensional numerical simulations of two segmentally baffled shell-an... more In the present study, three-dimensional numerical simulations of two segmentally baffled shell-and-tube heat exchangers (STHXs) with plain tube bundle (STHXsPT) and annular-finned tube bundle (STHXsFT) are carried out using finite element method (FEM). A comparative study is performed to evaluate the thermal performance and energy efficiency of both types of STHXs based on the simulation results. The results show that STHXsFT has higher shell-side heat transfer coefficient and improved shell-side cross flow characteristics, while STHXsPT has lower shell-side pressure drop. However, STHXsFT has slightly higher heat transfer coefficient per unit pressure drop compared to STHXsPT.
In the present study, three-dimensional numerical simulation of two shell-and-tube heat exchanger... more In the present study, three-dimensional numerical simulation of two shell-and-tube heat exchangers (STHXs) with conventional segmental baffles (STHXsSB) and continuous helical baffle (STHXsHB) is carried out and a comparative study is performed based on the simulation results. Both of the STHXs contain 37 tubes inside a 500 mm long and 200 mm diameter shell and mass flow rate of shell-side fluid is varied from 0.5 kg/s to 2 kg/s. At first, physical and mathematical models are developed and numerically simulated using finite element method (FEM). For the validation of the computational model, shell-side average nusselt number (Nus) is calculated from the simulation results and compared with the available experimental results. The comparative study shows that STHXsHB has 72-127% higher heat transfer coefficient per unit pressure drop compared to the conventional STHXsSB for the same shell-side mass flow rate. Moreover, STHXsHB has 59-63% lower shell-side pressure drop than STHXsSB.
Reports by Asif Ahmed
For last some decades unmanned aerial vehicles (UAV) are being used to a great extent in many
pur... more For last some decades unmanned aerial vehicles (UAV) are being used to a great extent in many
purposes like military surveillance, remote sensing, accident investigation etc. In recent years
UAVs are getting popular in inspection of structural damage specially after earth-quake like disasters.
Our quadcopter is controlled by RF joystick and equipped camera and an on-board controller.
Images captured by flying quadcopter with corresponding loaction have been processed to detect
the crack and damage condition. With available damage condition and location further steps can
be taken.
Thesis Chapters by Asif Ahmed
In the present thesis, three-dimensional numerical simulations of shell-and-tube heat exchangers ... more In the present thesis, three-dimensional numerical simulations of shell-and-tube heat exchangers (STHXs) with conventional segmental baffle, continuous helical baffle and annular-finned tube bundle are carried out using finite element method (FEM). Three comparative studies are performed based on the simulation results. In the first study, performance comparison of shell-and-tube heat exchanger with conventional segmental baffles (STHXsSB) and continuous helical baffle (STHXsHB) is done. In the second study, performance comparison of STHXsSB with plain tube bundle (STHXsPT) and annular-finned tube bundle (STHXsFT) is done. In the third study, number of turns of continuous helical baffle (1, 1.5 and 2.5 turns), mainly helix angle (ϕ = 25.52̊, 17.66̊ and 10.81̊ respectively), is varied for STHXsHB to analyze the effect of it on shell-side fluid flow and find the optimum helix angle. At first, physical and mathematical models are developed and numerically simulated using FEM. For the validation of the computational model, shell-side average Nusselt number (Nus) is calculated from the simulation results and compared with the available experimental results, and reasonably good agreement is obtained. The first comparative study shows that STHXsHB has 72-127% higher heat transfer coefficient per unit pressure drop compared to the conventional STHXsSB for the same shell-side mass flow rate. Moreover, STHXsHB has 59-63% lower shell-side pressure drop than STHXsSB. The second study shows that STHXsFT has 15% higher heat transfer coefficient as well as slightly higher heat transfer coefficient per unit pressure drop compared to STHXsPT. In the third study, it has been observed that ϕ = 25.52̊ shows the best performance and with the decrease of helix angle (i.e. increase of number of turns of helical baffle) the overall thermal performance and energy efficiency of STHXsHB decreases.
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Papers by Asif Ahmed
Conference Presentations by Asif Ahmed
Reports by Asif Ahmed
purposes like military surveillance, remote sensing, accident investigation etc. In recent years
UAVs are getting popular in inspection of structural damage specially after earth-quake like disasters.
Our quadcopter is controlled by RF joystick and equipped camera and an on-board controller.
Images captured by flying quadcopter with corresponding loaction have been processed to detect
the crack and damage condition. With available damage condition and location further steps can
be taken.
Thesis Chapters by Asif Ahmed
purposes like military surveillance, remote sensing, accident investigation etc. In recent years
UAVs are getting popular in inspection of structural damage specially after earth-quake like disasters.
Our quadcopter is controlled by RF joystick and equipped camera and an on-board controller.
Images captured by flying quadcopter with corresponding loaction have been processed to detect
the crack and damage condition. With available damage condition and location further steps can
be taken.