Thermal performance evaluation of a conical solar water heater integrated with a thermal storage system

Imtiaz Hussain, M.,Lee, G.H. Pergamon ; Elsevier Science Ltd 2014 Energy conversion and management Vol.87 No.-

In the present research, a conical solar water heater (CSWH) with an attached thermal storage tank, with or without a vacuum glass absorber, was analyzed under different operating conditions. For maximum solar radiation of the system, the collector was equipped with a dual-axis tracking system and sun sensor, which kept the system oriented towards the sun at every instant during its operation. A forced cooling system circulated fluid to remove the solar heat from the absorber surface. Performance analyses with and without the vacuum glass absorber were conducted at different mass flow rates, inlet temperatures, and solar irradiation values. The influence of the vacuum glass cover and all operational parameters on the collector efficiency, outlet temperature, and thermal stratification were investigated. The efficiency increased with increasing inlet flow rate, and the maximum efficiency was obtained at a critical flow rate of 6L/min. When the flow rate was increased beyond this critical value, the efficiency began to decrease. The temperature rise of the working fluid with vacuum glass at a high rate of insolation was considerably higher than without a vacuum glass for all flow rates. Use of a high flow rate deteriorated the thermal stratification process in the storage tank, while it increased the efficiency of the conical solar water-heating system. It can be concluded that the CSWH operates more efficiently if the fluid is heated slightly at a critical flow rate.

Hierarchical structure parameters in three dimensional turbulence: She-Leveque model

Imtiaz Ahmad,Lamjed Hadj-Taieb,Muzamal Hussain,Mohamed A. Khadimallah,Muhammad Taj,Adil Alshoaibi 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.29 No.5

Hierarchical structure parameters, proposed in She-Leveque model, are investigated for velocity components obtained from different flow types over a large range of Reynolds numbers 255 < < 720. The values of intermittency parameter , with respect to a fixed velocity component, are observed nearly same for all four types of turbulence. The parameter , for streamwise velocity components is nearly the same but significantly different for vertical components in different flows. It is also observed that for both parameters, an obvious relation between the longitudinal and transverse components < (and < ) always holds. However, the difference between and is found very small in all types of turbulent flows, we studied here. It is evidenced that at low Reynolds numbers, the deviations from K41 scaling are mainly due to the most intense structures and slightly because of more heterogeneous hierarchy of fluctuation structures. However, at higher Reynolds numbers the deviations seem as a consequence of the most intense structures only. Over all, the study suggests that the hierarchy parameter may be consider as a universal constant.

After Cancún:G21, WTO, and Multilateralism

Imtiaz Hussain 서울대학교 국제학연구소 2004 Journal of International and Area Studies Vol.11 No.2

Why did the Cancún WTO meeting collapse? What is expected next? A content analysis finds G21 at the interface of 1) less developed countries (LDCs) protesting the uneven playing field; 2) long-standing substantive fissures; 3) increasing unilateralism by developed countries (DCs); and 4) farm protection haunting multilateralism. US competitive liberalization emerges most coherently from the WTO wreckage (Feinberg 2003). Based on discrimination and asymmetrical reciprocity, it aggressively targets the European Union (EU), seeks LDC bandwagoning, discourages regime reconstruction (Krasner 1982), defies neorealist/neoliberalist/constructivist tendencies (Waltz 1979; Keohane 1989; Hopf 1998), and predicts future trade turbulence (Rosenau 1997).

``The Crisis posed by discovery`` in common law civil justice system: some proposals for solution

( Imtiaz Mohammad Morshed ) 고려대학교 법학연구원 2011 Korea University Law Review Vol.10 No.-

There is a growing crisis in common law civil justice system due to increasing cost, complexity and delay. The process of discovery is cited by most of the critic as one of the key barrier to justice. The common criticisms of discovery are that the objectives of the process are being achieved only at great cost where delay has become a common phenomenon. Sometimes, it is being used as a tactical weapon to harass other party. Several Intensive and extensive reforms already took place in different jurisdictions. Things had not improved, much rather they are getting even more chronic. This study begins with a description of the very concept and history of discovery of common law system. The study tries to figure out the problems associated with discovery and their potential source. A brief overview of the latest development in different jurisdiction is also examined. This study comes up with some solution that leads to functional as well as value driven change. Discrete procedural reforms or mere existence of principle do not bring success. Appropriate functional change combined with the application of relevant principle may render an expeditious and efficient system. A number of procedural measures driven by specific objectives are likely to bring a considerable outcome in the pursuit of the ultimate goal of achieving justice. This is the key message explored in the article. Therefore, this study proposes some solution.

Wireless Powered Decode-and-Forward Relaying with a Low-Altitude UAV

Imtiaz Akber Chowdhury(임티아즈 아크바르 초우두리),Changgyu Lee(이창규),Yun Hee Kim(김윤희) 한국통신학회 2020 한국통신학회 학술대회논문집 Vol.2020 No.2

Numerical and experimental heat transfer analyses of a novel concentric tube absorber under non-uniform solar flux condition

Imtiaz Hussain, M.,Lee, Gwi Hyun Pergamon 2017 RENEWABLE ENERGY Vol.103 No.-

<P><B>Abstract</B></P> <P>The thermal performance of a novel concentric tube absorber for a conical solar collector (CSC) under forced convection was investigated by numerical and experimental analyses. In this system, the CSC assembly is mounted on dual axis tracking platform that can accurately track the sun position to get maximum concentrated solar radiation over the entire circumference of the absorber. Due to conical-shape reflector, the non-uniformity of the solar flux distribution along the absorber length is high; therefore, the non-uniform concentrated solar flux was applied to the absorber surface as boundary condition in Fluent software. To evaluate the heat transfer characteristics and performance of the system, heat loss and gain factors were derived from the novel concentric tube absorber while varying the flow rate. The concentric tube absorber of the CSC system was developed and analyzed with different operational parameters. The double-tube design provides the uniformly distributed flow and temperature symmetricity along the absorber length. The predicted results of the CSC system were in good agreement with the measured results.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A numerical thermal analysis of a concentric tube absorber was performed. </LI> <LI> Non-uniform solar flux was applied by dividing the absorber into different parts. </LI> <LI> CSC with dual axis tracker got concentrated flux on whole absorber circumference. </LI> <LI> The numerical model of the absorber was validated with experimental results. </LI> </UL> </P>

Thermal performance comparison of line- and point-focus solar concentrating systems: Experimental and numerical analyses

Imtiaz Hussain, M.,Lee, G.H. Association for Applied Solar Energy ; Elsevier Sc 2016 SOLAR ENERGY -PHOENIX ARIZONA THEN NEW YORK- Vol.133 No.-

The purpose of this study was to analyze and compare the thermal performances of a line-focus and a point-focus solar concentrators (LFSC and PFSC, respectively) under similar operating and weather conditions in South Korea. Both concentrator systems had Fresnel lenses of the same surface area. To reduce heat loss, absorber pipes of the LFSC and PFSC systems were covered with borosilicate glass tube and foamed polyethylene insulation, respectively. Collector temperature (inlet and outlet temperature differential), collected energy, and thermal efficiency over experimental test time were calculated while the solar radiation, volumetric flow rate, and inlet temperature of the thermal fluid were varied. Good harmony was observed between the experimental and predicted results. Calibration of the both models reduced the deviation between the experimental and predicted temperature results compared to the uncalibrated models. Although both solar collectors showed similar trends in the variations of the average efficiency and total collected energy, these parameters were about 7% and 8% higher, respectively, in the PFSC compared to the LFSC. Overall, the results indicate that the PFSC performs slightly better than the LFSC in terms of the thermal efficiency, total collected energy, and heat loss.

Advances in solar thermal harvesting technology based on surface solar absorption collectors: A review

Imtiaz Hussain, M.,Mé,né,zo, Christophe,Kim, Jun-Tae Elsevier 2018 Solar energy materials and solar cells Vol.187 No.-

<P><B>Abstract</B></P> <P>This study presents a critical review of the major research and development work that has advanced surface solar absorption technology and also discusses the applications of this technology in the last 15 years. In a surface solar absorption collector (SSAC), solar radiation is first absorbed on the surface of the collector and then transferred to the circulating fluid. This article reviews a wide range of studies on different SSAC systems with the aim of identifying research gaps to prepare this technology for commercial availability. Moreover, qualitative and quantitative research information on non-concentrating and concentrating SSACs was collected and evaluated in the context of a performance-based assessment, environmental issues, and sustainability concerns. The performance of these collectors mainly relies on the receiver design and thermal storage tanks with different heat transfer fluids. For high concentration collectors, there is an urgent need for new heat transfer and storage fluids to withstand elevated temperatures to minimize the flow instability. A review of the literature suggests that ongoing high quality research on this technology, especially on medium and high concentration collectors, will soon overcome the existing problems bringing this technology into temperature ranges that will make it commercially available. Finally, the scientific challenges and opportunities relevant to this technology are also discussed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Various types of surface solar absorption systems have been critically discussed. </LI> <LI> Report trends of research and development of the technology advancements. </LI> <LI> Recently developed application advancements have been highlighted. </LI> <LI> Based on literature reviewed, opportunities and challenges have been proposed. </LI> </UL> </P>

Modeling of Wire Electrical Discharge Machining of Alloy Steel (HCHCr)

Imtiaz Ali Khan,Tikam Singh Rajput 한국정밀공학회 2012 International Journal of Precision Engineering and Vol. No.

This study provides predictive models for the functional relationship between input and output variables of wire cut electrical discharge machine (WEDM) environment using alloy steel (HCHCr). Multi- objective optimization of the process parametric combinations is attempted by modeling WEDM process by use of artificial neural networks (ANN). This work provide an optimized input data set to WEDM system and the results show improvement with better productivity, reduced cutting time and product cost at the cutting speed and surface finish. At experimental result, the surface quality decreases as cutting speed increases and 1.371 mm/min becomes the maximum cutting speed obtained with good surface finish of 0.387 micron. The results show the potential to improve production efficiency and part quality.

Performance Comparison and Model Validation of a Conical Solar Reflector and a Linear Fresnel Concentrator

Imtiaz Hussain, M.,Hyun Lee, Gwi ASME International 2016 Journal of Solar Energy Engineering Vol.138 No.6