Search results

This paper aims to study the fluid flow and heat transfer through a spiral double-pipe heat exchanger. Nowadays using spiral double-pipe heat exchangers has become popular in different industrial segments due to its complex and spiral structure, which causes an enhancement in heat transfer.

In these heat exchangers, by converting the fluid motion to the secondary motion, the heat transfer coefficient is greater than that of the straight double-pipe heat exchangers and cause increased heat transfer between fluids.

The present study, by using the Fluent software and nanofluid heat transfer simulation in a spiral double-tube heat exchanger, investigates the effects of operating parameters including fluid inlet velocity, volume fraction of nanoparticles, type of nanoparticles and fluid inlet temperature on heat transfer efficiency.

After presenting the results derived from the fluid numerical simulation and finding the optimal performance conditions using a genetic algorithm, it was found that water–Al₂O₃ and water–SiO₂ nanofluids are the best choices for the Reynolds numbers ranging from 10,551 to 17,220 and 17,220 to 31,910, respectively.

In the present research, a numerical investigation is carried out to study the fluid flow and heat transfer in a double-pipe, counter-flow heat exchanger exploiting metal foam inserts partially in both pipes. The purpose of this study is to achieve the optimal distribution of a fixed volume of metal foam throughout the pipes which provides the maximum heat transfer rate with the minimum pressure drop increase.

The governing equations are solved using the finite volume method. The metal foams are divided into different number of parts and positioned at different locations. The number of metal foam parts, their placements and their volume ratios in each pipe are sought to reach the optimal conditions. The four-piece metal foam with optimized placement and partitioning volume ratios is selected as the best layout. The effects of the permeability of metal foam on the Nusselt number, the performance evaluation criteria (PEC) and the overall heat transfer coefficient are investigated.

It was observed that the heat transfer rate, the overall heat transfer coefficient and the effectiveness of the heat exchanger can be improved as high as 69, 124 and 9 per cent, respectively, while the highest value of PEC is 1.36.

Porous materials are widely used in thermo-fluid systems such as regenerators, heat sinks, solar collectors and heat exchangers.

Having less pressure drop than fully filled heat exchangers, partially filled heat exchangers with partitioned metal foams distributed optimally enhance heat transfer rate more economically.

This is a 3D numerical study of convective heat transfer through a micro concentric annulus governing non-uniform heat flux boundary conditions employing water-Al₂O₃ nanofluid. The nanofluid is modeled using two-phase mixture model, as it has a good agreement to experimental results.

Half of the inner pipe surface area of the annulus section of a double pipe heat exchanger is exposed to a constant heat flux which two models are considered to divide the exposing surface area to smaller ones considering the fact that in all cases half of the inner pipe surface area has to be exposed to the heat flux: in model (A), the exposing surface area is divided radially to two parts (A1), four parts (A2) and eight parts (A3) by covering the whole length of the annulus and in model (B) the exposing surface area is divided axially to two parts (B1), four parts (B2) and eight parts (B3) by covering half of the annulus radially.

The results reveal that model (B) leads to higher Nusselt numbers compared to model (A); however, at Reynolds number 10, model (A3) exceeds model (B3). The average Nusselt number is increased up to 142 and 83 per cent at models (A3) with Reynolds number 10 and model (B3) with Reynolds number 1000, respectively.

This paper is a two-phase investigation of water-Al₂O₃ nanofluid in a micro concentric annulus under non-uniform heat flux boundary conditions.

Academic coaching (AC) has gained a significant attention to support student success and achievement in higher education, management and psychology. This study aimed to conduct a comprehensive bibliometric analysis of AC literature to identify the top authors, research patterns, hotspots and research topics in the field.

The study utilized a bibliometric analysis of articles published between 1987 and 2023, using descriptive and network analysis methods with tools such as RStudio, Biblioshiny, Excel and VOSviewer. The study also conducted functional, mapping and content analysis, to identify AC literature's key themes and research areas.

The results revealed an increasing interest in AC, with increased publications. However, there are gaps in geographical diversity and authorship. Most studies were conducted in the United States of America and the UK, and were published in education, psychology and coaching journals. Common themes included coaching, professional development, higher education and mentoring. Emerging research areas include: coaching efficacy in education, AC as an online learning support and professional learning communities. More studies are needed in different contexts and with larger sample sizes.

This comprehensive bibliometric analysis adds to the existing literature by presenting a detailed analysis of the field of AC, filling a gap in the current literature. The study's unique contribution is its examination of emerging research areas and themes in AC literature, providing directions for future research. This study is particularly relevant for researchers, practitioners and policymakers interested in understanding AC's state of the art and identifying promising areas for future research.

The purpose of the study is to propose a novel implementation of twisted tape in sinusoidal wavy-walled tubes to enhance the rate of heat transfer without compromising thermal efficiency. The study numerically investigates the fluid flow characteristics and analyzes the effect of different geometrical configurations, including wall wave amplitude, tape twist angles and nanoparticle volume fractions, on heat transfer improvement and performance factor.

This problem is numerically investigated using computational fluid dynamics, and the method is the finite volume method. A two-phase mixture model is used for nanofluid modeling.

The study investigated the effect of wall waviness, twisted tape, and nanoparticles on forced convective heat transfer and friction factor behavior in laminar pipe flow in three different Reynolds number regimes. The results showed that implementing twisted tape in wavy tubes significantly increased the rate of heat transfer and the performance factor, with the best twist ratio between 90 and 180°. Adding nanoparticles also enhanced heat transfer and performance factor, but to a lesser extent than wavy wall-twisted tape combinations. The study suggests selecting a proper combination of wavy wall and twisted tape at each Reynolds number to achieve an optimum solution.

To the best of the authors’ knowledge, the implementation of the selected passive methods in sinusoidal wavy tubes has not been studied before, and no previous studies have taken into account such a mix of heat transfer improvement techniques.

The purpose of this paper is to evaluate higher education quality from the perspective of university graduates.

Based on Kaufman and Herman's model of education output as well as Yamani Doozi Sorkhabi, a researcher‐designed questionnaire is used to collect the data requiring response to five questions in the study. Research questions addressed such areas as: first, the adequacy of the curriculum; second, the status of the graduates in the job market; third, graduates' perception of their educational experience; fourth, desire to engage in future research; fifth, ability of graduates to interact with the university. For each research question, a group of indicators are defined. The validity of indicators is confirmed by experts in the field. Cronbach's alpha indicated a reliability of 79 percent. The population comprised 700 graduates holding BSc degree in basic sciences from a small‐sized university. A total of 250 of these students comprised a random sample. A total of 126 responses are received.

Results indicated a high degree of satisfaction with the curriculum, relative satisfaction with the educational experience, but low satisfaction with the acquisition of research abilities and research experience.

Universities need to be constantly rethinking, restructuring, and revitalizing their programs with employment skills in mind. In the case of a program in basic sciences, the ability to engage in some elements of research is a relevant employment skill yet, in the university under study, despite the fact that students generally enjoyed their educational experience; it seems they acquired little in the way of the skills required in the market place. Universities need to ensure that mechanisms are in place to obtain alumni and employer feedback to enable programs of study to not only be interesting, but also relevant to the community. However, despite the graduates' interest in an ongoing interaction with the university (83 percent of interest), the university under study did not emphasize such interaction. This is rather shortsighted given the need for modern universities to be responsive to the various stakeholders.

This paper should be of value to education leaders, educational planners, as well as university professors who are interested in ensuring that university curricula are current and relevant.

The purpose of this paper is the development of a multiscale model which simulates the effect of the dispersion, the waviness, the interphase geometry as well as the agglomerations of multi-walled carbon nanotubes (MWCNTs) on the Young’s modulus of a polymer filled with 0.4 Vol.% MWCNTs.

For the determination of the homogenized elastic properties of the hybrid material representative unit cells (RUCs) have been used. The predicted homogenized elastic properties were used for the prediction of the Young’s modulus of the filled material by simulating a finite element (FE) model of a tensile specimen. Moreover, the model has been validated by comparing the predicted values of the numerical analysis with experimental tensile results.

As the MWCNT agglomerates increase, the results showed a remarkable decrease of the Young’s modulus regarding the polymer filled with aligned MWCNTs while only slight differences on the Young’s modulus have been found in the case of randomly oriented MWCNTs. This might be attributed to the low concentration of the MWCNTs (0.4 Vol.%) into the polymer. For low MWCNTs concentrations, the interphase seems to have negligible effect on the Young’s modulus. Furthermore, as the MWCNTs waviness increases, a remarkable decrease of the Young’s modulus of the polymer filled with aligned MWCNTs is observed. In the case that MWCNTs are randomly dispersed into the polymer, both numerical and experimental results have been found to be consistent regarding the Young’s modulus.

The methodology used can be adopted by any system containing nanofillers.

Although several studies on the effect of the MWCNTs distribution on the Young’s modulus have been conducted, limited results exist by using a more realistic RUC including a periodic geometry of more than 20 MWCNTs with random orientation and a more realistic waviness of MWCNTs with aspect ratio exceeding 150.

This study aims to investigate the tensile strength and elastic modulus of custom-designed polymer composites developed using voxel-based design. This study also evaluates theoretical models, such as the rule of mixtures, Halpin–Tsai model, Cox–Krenchel model and the Young–Beaumont model and the ability to predict the mechanical properties of particle-reinforced composites based on changes in the design of rigid particles at the microscale within a flexible polymer matrix.

This study leverages the PolyJet process for voxel-printing capabilities and a design of experiments approach to define the microstructural design elements (i.e. aspect ratio, orientation, size and volume fraction) used to create custom-designed composites.

The comparison between the predictions and experimental results helps identify appropriate methods for determining the mechanical properties of custom-designed composites ensuring informed design decisions for improved mechanical properties.

This work centers on multimaterial additive manufacturing leveraging design freedom and material complexity to create a wide range of composite materials. This study highlights the importance of identifying the process, structure and property relationships in material design.