1,720,958 research outputs found
Effect of Cross Nanowall Surface on the Onset Time of Explosive Boiling: A Molecular Dynamics Study
No full textExplosive boiling is a fast-phase transition from an ultra-thin liquid film to vapor under an extremely high heat flux, which typically has been studied using the molecular dynamics simulation (MDS) method. The present MDS study investigated the explosive boiling of a liquid argon nanofilm over different solid copper surfaces with different nanowall patterns, including parallel and cross nanowalls. For each surface, atomic motion trajectories, the number of liquid and vapor argon atoms, heat flux, and, mainly, the onset time of explosive boiling were investigated. The simulation results indicated that explosive boiling occurs earlier on parallel and cross nanowall surfaces than on an ideally smooth surface, regardless of the topology and configuration of the nanowalls. Moreover, the results revealed that by using the cross nanowall surfaces, the onset time of explosive boiling decreased by 0.7–4% compared to the parallel nanowall surfaces. In addition, it was found that the onset time of explosive boiling strongly depends on the potential energy barrier and the movement space between nanowalls for both parallel and cross nanowall surfaces. Furthermore, the simulation findings showed that even though increasing the height of cross nanowalls increases the heat flux and temperature of the fluid argon domain, it does not necessarily result in a shorter onset time for explosive boiling. These findings demonstrate the capability of cross nanowall surfaces for explosive boiling, thereby being utilized in future surface design for thermal management applications
Scambiatoti Microscambiatori per l’industria farmaceutica e alimentare
No full textThe thesis aims to discuss the application and optimization of conventional and micro heat exchangers within the pharmaceutical and food industries, focusing on their critical roles in enhancing process efficiency and product quality. By examining traditional heat exchangers, which are integral to large-scale operations for maintaining consistent temperature control, and comparing them with advanced micro heat exchangers, which offer precision and compactness for smaller-scale or specialized processes. The research investigates how these technologies contribute to enhancing energy efficiency, regulatory compliance, and overall process optimization, providing insights into their design, operational performance, and potential for innovation in high-demand environments. Moreover, this thesis also offers valuable recommendations for the effective implementation of heat exchange systems to the specific needs of the pharmaceutical and food sectors.
Heat transfer enhancement is crucial in the food and pharmaceutical industries to enhance process efficiency, product quality, and energy savings. To improve the local convective heat transfer coefficient, this research introduces an inverse study approach using an experimental infrared camera to measure temperature data obtained within a corrugated pipe. Specifically, six pipes with different corrugation profiles were studied to investigate the effects of various designs, including helical, transversal, and cross-helical types, with pitch sizes of 16 mm and 32 mm. To evaluate their effect on heat transfer performance, the findings were examined and presented from both local and average viewpoints. The results indicate that pitch size and corrugation type/design play a significant role in enhancing the performance of the tested pipe. The result of this research in turbulent regime has shown that transversal corrugation generates the highest improvement in heat transfer performance. Consequently, the single helix solution is the preferred one in heat exchangers adopted in the food and pharmaceutical industries, and these helical corrugations are the easiest to manufacture. A merger solution between them is represented by the cross-helix profile. The cross-helix profile with the bigger pitch size performs better than all other corrugated pipes, especially in the low/intermediate Reynolds number range (i.e., 100-1000). The estimation process (for local heat transfer) proposed in this study employs the external surface temperature of the tube, acquired with an infrared thermal camera, as starting data for the inverse heat conduction problem inside the pipe wall region. The calculation of its Laplacian was finally achieved by a filtering technique applied to the infrared temperature acquisitions
Local heat-transfer coefficient estimation in cross-helix corrugated tubes under turbulent regime
No full textIn a wide variety of engineering applications, convection heat transfer enhancement plays a major role in reducing the heat exchanger's size and costs and increasing their efficiency. The passive methods for increasing convective heat transfer are the most interesting since they don't require any external power to achieve the desired enhancement. For this reason, this approach is preferred in the industrial sector of heat exchangers. For the enhancement of the performances of these apparatuses, in particular, the tubular ones used in the pharmaceutical, food, and chemical, the most adopted passive solution is the corrugation of their tube walls. Two pipes characterized by cross-helix corrugation have been experimentally analyzed both investigating the global heat transfer performance and studying the local heat transfer coefficient distribution to profoundly examine the thermal performance enhancement mechanisms of this passive technique. It has been observed that at Re = 16,000, the heat transfer rate in the smaller pitch tube is 18.18% higher than that in the larger pitch tube. The inverse heat conduction problem in the tube wall is addressed to achieve the local coefficient distribution method by using temperature readings collected from an infrared camera on the outer surface of the tube as the initial data
Transient analysis of an efficient solar assisted air-conditioning system for subtropical climate with various solar thermal collectors
No full textPerformance investigation of solar assisted desiccant integrated Maisotsenko cycle cooler in subtropical climate conditions
No full textInfrared thermography applied to the study of the local heat transfer enhancement in a wall corrugated tubular heat exchanger for food applications
No full textThe combination of global and local performance analysis represents a powerful tool for the optimal design and sizing of heat exchangers, especially when wall corrugations are employed to enhance inner convection. In this paper, both approaches are applied to a transversely corrugated pipe to propose a thermal correlation and investigate the effects of corrugation on the local heat transfer performance. For the local analysis, infrared thermographic measurements, combined with the solution of the inverse heat conduction problem in the solid wall domain, were used to evaluate the internal convective heat transfer coefficient. The combined approach offers a valuable tool for the optimal design of heat exchangers and related thermal processes, particularly in applications where knowledge or prediction of the local temperature-time history of fluid particles is critical. This is especially relevant in the food industry, where such passive heat transfer enhancement solutions are widely used
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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