Numerical Study on the Wall to Bed Heat Transfer in a Conical Fluidized Bed Combustor

Hamada Mohamed Abdelmotalib,Mahmoud Abdelftah Youssef,Ali Ahmed Hassan,윤석범,임익태 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

In this work a numerical investigation of wall to bed heat transfer, and the related flow characteristics, was conducted along a conical fluidized bed combustor with a height of 0.8 m and a cone angle of 30o. A two-fluid Eulerian-Eulerian model was used while applying Kinetic Theory for Granular Flow (KTGF) to a wall-to-bed FB reactor. The heat transfer coefficient and hydrodynamics are discussed for two different drag models, namely the Gidaspow and Syamlal-O’Brien models. Furthermore, computational calculations were carried out for a variety of inlet velocities(1.4Umf~4 Umf) and different particle sizes. The heat transfer coefficient in the bed region was evaluated and compared with that calculated by penetration theory. The bed expansion for the two models was compared with that calculated using correlations from literature in order to validate the numerical calculations. The heat transfer coefficient was found to be increasing with increasing gas velocity and decreasing with increasing particle diameter.

Experimental Investigation of Mechanical and Tribological Characteristics of Al 2024 Matrix Composite Reinforced by Yttrium Oxide Particles

Hamada, Mohanad Lateef,Alwan, Ghazwan Saud,Annaz, Abdulkader Ahmed,Irhayyim, Saif Sabah,Hammood, Hashim Shukur Materials Research Society of Korea 2021 한국재료학회지 Vol.31 No.6

Composite materials offer distinct and unique properties that are not naturally inherited in the individual materials that make them. One of the most attractive composites to manufacture is the aluminum alloy matrix composite, because it usually combines easiness of availability, light weight, strength, and other favorable properties. In the current work, Powder Metallurgy Method (PMM) is used to prepare Al2024 matrix composites reinforced with different mixing ratios of yttrium oxide (Y₂O₃) particles. The tests performed on the composites include physical, mechanical, and tribological, as well as microstructure analysis via optical microscope. The results show that the experimental density slightly decreases while the porosity increases when the reinforcement ratio increases within the selected range of 0 ~ 20 wt%. Besides this, the yield strength, tensile strength, and Vickers hardness increase up to a 10 wt% Y₂O₃ ratio, after which they decline. Moreover, the wear results show that the composite follows the same paradigm for strength and hardness. It is concluded that this composite is ideal for application when higher strength is required from aluminum composites, as well as lighter weight up to certain values of Y₂O₃ ratio.

Design Method of 2-D Lattice Digital Filters Using the Genetic Algorithm

Hamada, Nozomu,Kishida, Masahiko 대한전자공학회 1994 ISPACS:Intelligent Signal Processing and Communica Vol.1 No.1

This paper proposes design method of 2-D lattice digital filters using the Genetic Algorithm(GA). By using the GA, they are derived directly from the desired frequency response, and 2-D stable nonseparable-denominator transfer functions can be obtained. In our method, ARMA transfer functions are designed by two algorithms. One is to optimize AR and MA parameters simultaneously, and the other is to search an optimal AR parameters with fixed MA parameters, and then search an optimal MA parameters separately. Both are done by the GA, and the simulation shows that they give the simillar results.

An Instance-Oriented Modeling Method for Shipbuilding Applications

Hamada, Shinro,Konaka, Kiyoshi The Society of Naval Architects of Korea 2001 Journal of ship and ocean technology Vol.5 No.2

Data in one Product Model for shipbuilding is inevitably referenced and manipulated during each phase of design or production activities, and data or manipulation status naturally varies from the original with the advance of each activities. For Object-Oriented approach, it is hard to identify classes dealing with those variations, and even if once a product model is developed, it might be getting much harder to modify it to cope with a new additional phase of activities. This paper proposes an Instance-Oriented Modeling Method, temporarily named “Concept-Relationship Modeling Approach”, which handles Data structure and Behavior independently of each other in order to resolve the difficulties above.

Numerical Modeling of Conical Fluidized Bed Combustors Considering Particle Slip on Wal

Hamada Abdelmotalib,Ik-Tae Im(임익태) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11

In this paper, the hydrodynamics and wall to bed heat transfer of a gas?solid flow in a conical fluidized bed were simulated using the Eulerian-Eulerian model. Sand with a particle diameter of 560 μm was used as a bed material, and its properties were calculated by applying the kinetic theory of granular flow (KTGF). Different amounts of slip between the particle and wall were shown by varying the specularity coefficient. The effects of specularity (0, 0.2, 0.5, and 1.0) on hydrodynamic and wall to bed heat transfer at a superficial gas velocity of 2 m/s were investigated. It was found that the wall to bed heat transfer coefficient decreases with increasing specularity coefficient. Different values of the specularity coefficient resulted in almost the same hydrodynamic behavior near the wall and the center of the bed.

Numerical Study on Heat Transfer According to Different Flow Regimes in Fluidized Bed Reactors

Hamada M. Abdelmotalib,Ik-Tae Im(임익태) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.4

Computational study of serpentine nozzle performance with annular mixer

Hamada Mohamed(하마다 모하메드),Changwook Lee(이창욱),Heeju Choi(최희주),Jeekeun Lee(이지근) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.8

The suppression of the infrared radiation emitted from the exhaust system and high temperature walls can increase the survivability of fighter aircraft. Anon-symmetric nozzle such as serpentine nozzle is one method can be used to minimize the infrared radiation. A serpentine nozzle can reduce infrared radiation by 70%. Utilization of aft-deck decreases the external jet length and helps in shielding the high temperature sections of the turbine and engine exhaust nozzle that can reduce the IR radiation by 90%. The appropriate understanding of flow characteristics of a nozzle with aft-deck is important for the design process of the engine exhaust nozzle. To study the effect of aft-deck the flow characteristics were compared to those of nozzle without aft-deck. The simulations were carried out using the STAR CCM+ software. The grid system consists of 8,364,993 polyhedral cells was used in simulations. The bypass where cold air enters was treated as stagnation inlet subjected to pressure and temperature of 48963 Pa and 334.8 K, respectively. Core where hot gases enter, was also considered as stagnation inlet with temperature and pressure of 45023 Pa and 811.8 K, respectively. The outlet of the nozzle was treated as a pressure outlet suspected to the atmospheric temperature of 288 K. The results showed that the presence of aft-deck resulted in a slight increase of pressure along the nozzle length, decreasing the temperature of upper and lower nozzle walls, and reduce the size and length of the external jet that can reduce the infrared radiation. Moreover, the velocity at aft-deck decreased that lead to the reduction of the nozzle noise.

The Anatomy of Bubble Economy in Japan

Hamada, Yasuyuki 연세대학교 산업경영연구소 1992 산업과경영 Vol.10 No.1

"Bubble Economy," describes well the scene of Japanese economy since the end of 1980's. The purpose of this paper is to try to find the core of Bubble. It leads us to some explanations to the following questions: 1. Why did "Bubble" occur in Japan typically? 2. Why did "Bubble" emerge in the second half of 1980's, especially after 1987? 3. Why did "Bubble" emerge as a stock-inflation?

Finite element modelling of transmission line structures under tornado wind loading

Hamada, A.,El Damatty, A.A.,Hangan, H.,Shehata, A.Y. Techno-Press 2010 Wind and Structures, An International Journal (WAS Vol.13 No.5

The majority of weather-related failures of transmission line structures that have occurred in the past have been attributed to high intensity localized wind events, in the form of tornadoes and downbursts. A numerical scheme is developed in the current study to assess the performance of transmission lines under tornado wind load events. The tornado wind field is based on a model scale Computational Fluid Dynamic (CFD) analysis that was conducted and validated in a previous study. Using field measurements and code specifications, the CFD model data is used to estimate the wind fields for F4 and F2 full scale tornadoes. The wind forces associated with these tornado fields are evaluated and later incorporated into a nonlinear finite element three-dimensional model for the transmission line system, which includes a simulation for the towers and the conductors. A comparison is carried between the forces in the members resulting from the tornadoes, and those obtained using the conventional design wind loads. The study reveals the importance of considering tornadoes when designing transmission line structures.

Vitamin D status after colorectal cancer diagnosis and patient survival according to immune response to tumour

Hamada, Tsuyoshi,Liu, Li,Nowak, Jonathan A.,Mima, Kosuke,Cao, Yin,Ng, Kimmie,Twombly, Tyler S.,Song, Mingyang,Jung, Seungyoun,Dou, Ruoxu,Masugi, Yohei,Kosumi, Keisuke,Shi, Yan,da Silva, Annacarolina,G Elsevier 2018 European journal of cancer Vol.103 No.-

<P><B>Abstract</B></P> <P><B>Background</B></P> <P>High-level plasma 25-hydroxyvitamin D [25(OH)D] has been associated with lower colorectal cancer incidence and mortality. Considering evidence indicating immunomodulatory effects of vitamin D, we hypothesised that survival benefits from high systemic vitamin D level might be stronger for colorectal carcinoma with lower immune response to tumour.</P> <P><B>Methods</B></P> <P>Using 869 colon and rectal cancer cases within the Nurses' Health Study and Health Professionals Follow-up Study, we assessed the prognostic association of postdiagnosis 25(OH)D score [derived from diet and lifestyle variables to predict plasma 25(OH)D level] in strata of levels of histopathologic lymphocytic reaction. The Cox proportional hazards regression model was adjusted for potential confounders, including microsatellite instability, CpG island methylator phenotype, LINE-1 methylation, <I>PTGS2</I> (cyclooxygenase-2) expression and <I>KRAS</I>, <I>BRAF</I> and <I>PIK3CA</I> mutations.</P> <P><B>Results</B></P> <P>The association of postdiagnosis 25(OH)D score with colorectal cancer-specific mortality differed by levels of peritumoural lymphocytic reaction (<I>p</I> <SUB>interaction</SUB> = 0.001). Multivariable-adjusted mortality hazard ratios for a quintile-unit increase of 25(OH)D score were 0.69 [95% confidence interval (CI), 0.54–0.89] in cases with negative/low peritumoural lymphocytic reaction, 1.08 (95% CI, 0.93–1.26) in cases with intermediate peritumoural reaction and 1.25 (95% CI, 0.75–2.09) in cases with high peritumoural reaction. The survival association of the 25(OH)D score did not significantly differ by Crohn's-like lymphoid reaction, intratumoural periglandular reaction or tumour-infiltrating lymphocytes.</P> <P><B>Conclusions</B></P> <P>The association between the 25(OH)D score and colorectal cancer survival is stronger for carcinomas with lower peritumoural lymphocytic reaction. Our results suggesting interactive effects of vitamin D and immune response may contribute to personalised dietary and lifestyle intervention strategies.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The survival association of vitamin D is stronger in cancer with fewer lymphocytes. </LI> <LI> Vitamin D and peritumoural lymphocytes interact to modify cancer progression. </LI> <LI> Vitamin D may exert anti-tumour immune-enhancing effects. </LI> <LI> Peritumoural lymphocytic reaction may be a biomarker for benefits from vitamin D. </LI> <LI> Our data support immunomodulatory lifestyle interventions for cancer patients. </LI> </UL> </P>