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"Sayed, Ahmed"
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Flow and heat transfer enhancement in tube heat exchangers
The performance of heat exchangers can be improved to perform a certain heat-transfer duty by heat transfer enhancement techniques. Enhancement techniques can be divided into two categories: passive and active. Active methods require external power, such as electric or acoustic field, mechanical devices, or surface vibration, whereas passive methods do not require external power but make use of a special surface geometry or fluid additive which cause heat transfer enhancement. The majority of commercially interesting enhancement techniques are passive ones. This paper presents a review of published works on the characteristics of heat transfer and flow in finned tube heat exchangers of the existing patterns. The review considers plain, louvered, slit, wavy, annular, longitudinal, and serrated fins. This review can be indicated by the status of the research in this area which is important. The comparison of finned tubes heat exchangers shows that those with slit, plain, and wavy finned tubes have the highest values of area goodness factor while the heat exchanger with annular fin shows the lowest. A better heat transfer coefficient h
a
is found for a heat exchanger with louvered finned and thus should be regarded as the most efficient one, at fixed pumping power per heat transfer area. This study points out that although numerous studies have been conducted on the characteristics of flow and heat transfer in round, elliptical, and flat tubes, studies on some types of streamlined-tubes shapes are limited, especially on wing-shaped tubes (Sayed Ahmed et al. in Heat Mass Transf 50: 1091–1102,
2014
; in Heat Mass Transf 51: 1001–1016,
2015
). It is recommended that further detailed studies via numerical simulations and/or experimental investigations should be carried out, in the future, to put further insight to these fin designs.
Journal Article
Foreign object debris and damage in aviation
\"The book discusses biological and non-biological Foreign Object Debris (FOD) and associated Foreign Object Damage (FOD) in aviation. Written for aviation industry personnel, aircraft transport and ground operators, and aircraft pilots, the reader will learn to manage FOD to guarantee air traffic safety with minimum costs to airlines and airports. Management control for the debris begins at the aircraft design phase, and the book includes numerical analyses for estimating damage caused by strikes. The book explores aircraft operation in adverse weather conditions and inanimate FOD management programs for airports, airlines, airframe, and engine manufacturers\"-- Provided by publisher.
Book
Experimental and numerical study on thermal-hydraulic performance of wing-shaped-tubes-bundle equipped with winglet vortex generators
The present work evaluates, experimentally and numerically, by the aid of commercial code FLUENT 6.3.26, the effects of relative locations (∆X or ∆Y), heights (h
w
), and span-angle (θ) of winglet-vortex-generators (WVGs) on thermal-hydraulic performance enhancement for down-stream and/or up-stream wing-shaped-tubes bundle heat exchangers for air Re ranging from 1.85 × 10
3
to 9.7 × 10
3
while water Re = 5 × 10
2
. h
w
is set as 5 mm, 7.5 mm and 10 mm. For tube down-stream, θ is set as 0
°
(Base-line-case) and from 5
°
to 45
°
clockwise common-flow up (CFUp) and counterclockwise common-flow down (CFDn) while for tube up-stream it is set as −5
°
, −10
°
and −15
°
CFUp. Results show that the increase of θ counterclockwise-(CFDn) or clockwise-(CFUp) leads to increase the values of Nu number. Using WVGs with (+5
°
≤ θ ≤ +45
°
) results in increasing Nu number by about from 34 to 48% comparing with that of base-line-case. The lowest values of drag coefficient (
f
) for tube down-stream are obtained at +5
°
CFDn and −15
°
CFUp with respect to the base-line case. For tube up-stream, Nu number increases by increasing θ from 0
°
to −5
°
and the values of Nu number for θ varying from −5
°
to −15
°
have no significant changes. (
f
) increases with h
w
and has negligible effect on h
a
. Furthermore, optimization analyses of θ and longitudinal fin (LF) are utilized, in four cases, for finding the optimum combination and maximum efficiency. The highest values of heat transfer parameters such as effectiveness (ε), area goodness factor (G) and efficiency index (η) and the lowest values of fluid-flow parameters like (
f
) and hence the best efficiency, are achieved for −15
°
CFUp down-stream, (“case 3” of −15
°
CFUp down-stream and 6 mm LF height) and +5
°
CFDn down-stream. Correlations of Nu number, (
f
) and (ε) as a function of θ and Re for the studied cases are performed.
Journal Article
Geography for supporting decision-making process : applied studies on Kuwait
This academic publication explores the vital role of modern geographical sciences in shaping and supporting public policy and strategic planning in the State of Kuwait. Edited by Dr. Ahmed Mohamed Elsayed Hassan Elkasaby, the book presents a collection of empirical studies that demonstrate how spatial analysis, Geographic Information Systems (GIS), and remote sensing can address complex national challenges. The research covers a diverse range of applications, including urban land-use planning, the optimization of transportation networks, environmental risk assessment, and the management of natural resources. By providing data-driven geographical insights, the book aims to bridge the gap between academic research and the practical needs of decision-makers in Kuwaiti governmental and private sectors. It serves as a specialized reference for geographers, urban planners, and policy analysts interested in the intersection of spatial science and sustainable development in the Arabian Gulf.
BOOK
Upgrading Common Wheat Pasta by Fiber-Rich Fraction of Potato Peel Byproduct at Different Particle Sizes: Effects on Physicochemical, Thermal, and Sensory Properties
Fiber-enriched food has numerous health benefits. This study develops functional fiber-enriched pasta (FEP) by partially substituting wheat flour for alcohol-insoluble residue prepared from potato peel byproducts (AIR-PPB) at various particle sizes (PS). The independent variables’ effects, AIR-PPB at 2–15% substitution levels, and PS 40–250 µm were investigated in terms of chemical, cooking, thermal, and sensory properties. AIR-PPB is rich in total dietary fibers (TDF) (83%), exhibiting high water-holding capacity (WHC) and vibrant colors. Different concentrations of AIR-PPB increase TDF content in FEPs by 7–21 times compared to the control pasta (CP). Although the optimal cooking time (OCT) decreases by 15–18% compared to CP, where a lower OCT should reduce cooking time and save energy, cooking loss (Cl) increases slightly but remains within an acceptable range of 8%. Additionally, AIR-PPB altered the texture properties of FEP, with a moderate decrease in mass increase index (MII), firmness, and stickiness. AIR-PPB impairs the gluten network’s structure in pasta due to AIR-PPB’s WHC, which competes with starch for water binding, increasing the starch gelatinization temperature. FEPs show an increased lightness and yellowness and improved sensory properties. Highly acceptable FEPs were obtained for the following substitution levels: FEP11 (AIR-PPB at 2% and PS of 145 µm), FEP9 (AIR-PPB 4% level with PS of 70 µm), FEP6 (AIR-PPB of 4% level with 219 µm PS), and FEP1 (AIR-PPB = 8.5% with 40 µm PS), as compared to other FEPs.
Journal Article
Bitcoin and blockchain : history and current applications
In recent years, blockchain development has grown quickly from the original Bitcoin protocol to the second-generation Ethereum platform, and to today's process of building third-generation blockchains. During this evolution, we can see how blockchain technology has evolved from its original form as a distributed database to becoming a fully fledged, globally distributed, cloud computing platform. This book traces the past, present, and future of blockchain technology. Presents the knowledge and history of Bitcoin; Offers blockchain applications; Discusses developing working code for real-world blockchain applications; Includes many real-life examples; Covers the original Bitcoin protocol to the second-generation Ethereum platform. Bitcoin and Blockchain: History and Current Applications is a useful reference for students, business schools, research scholars, practitioners, and business analytics professionals.
Book
Heat transfer characteristics and entropy generation for wing-shaped-tubes with longitudinal external fins in cross-flow
A numerical study is conducted to clarify heat transfer characteristics, effectiveness and entropy generation for a bundle of wingshaped-tubes attached to Longitudinal fins (LF) at downstream side. The air-side Rea ranged from 1.8 x 10
3
to 9.7 x 10
3
. The fin height (h
f
) and fin thickness (δ) have been changed as: (2 mm ≤ h
f
≤ 12 mm) and (1.5 mm ≤ δ ≤ 3.5 mm). The analysis of entropy generation is based on the principle of minimizing the rate of total entropy generation that includes the generation of entropy due to heat transfer and friction losses. The temperature field around the wing-shaped-tubes with (LF) is predicted using commercial CFD FLUENT 6.3.26 software package. Correlations of Nu
a
, St
a
, and Bejan number (
Be
), as well as the irreversibility distribution ratio (Φ) in terms of Re
a
and design parameters for the studied bundle are presented. Results indicated that, installing fins with heights from 2 to 12 mm results in an increase in Nua from 11 to 36% comparing with that of wing-shaped tubes without fins (NOF). The highest and lowest values of effectiveness (ε) at every value of the considered Re
a
range are occurred at h
f
= 6 mm and (NOF), respectively. The wing-shaped-tubes heat exchanger with h
f
= 6 mm has the highest values of (ε), efficiency index (η) and area goodness factor (
G
a
) and also the lowest values of Φ and hence the best performance comparing with other arrangements. The minimum values of Φ are occurred at h
f
= 6 mm. (
Be
) decreases with increasing Re
a
for all studied h
f
. The heat transfer irreversibility predominates for (1800 ≤ Re
a
≤ 4200) while the opposite is true for (6950 < Re
a
≤ 9700). δ has negligible effect on Nu
a
and heat transfer irreversibility. Comparisons between the experimental and numerical results of the present study and those, previously, obtained for similar available studies showed good agreements.
Journal Article
Colistin and its role in the Era of antibiotic resistance: an extended review (2000-2019)
Increasing antibiotic resistance in multidrug-resistant (MDR) Gram-negative bacteria (MDR-GNB) presents significant health problems worldwide, since the vital available and effective antibiotics, including; broad-spectrum penicillins, fluoroquinolones, aminoglycosides, and β-lactams, such as; carbapenems, monobactam, and cephalosporins; often fail to fight MDR Gram-negative pathogens as well as the absence of new antibiotics that can defeat these \"superbugs\". All of these has prompted the reconsideration of old drugs such as polymyxins that were reckoned too toxic for clinical use. Only two polymyxins, polymyxin E (colistin) and polymyxin B, are currently commercially available. Colistin has re-emerged as a last-hope treatment in the mid-1990s against MDR Gram-negative pathogens due to the development of extensively drug-resistant GNB. Unfortunately, rapid global resistance towards colistin has emerged following its resurgence. Different mechanisms of colistin resistance have been characterized, including intrinsic, mutational, and transferable mechanisms.
In this review, we intend to discuss the progress over the last two decades in understanding the alternative colistin mechanisms of action and different strategies used by bacteria to develop resistance against colistin, besides providing an update about what is previously recognized and what is novel concerning colistin resistance.
Journal Article