A NUMERICAL-EXPERIMENTAL STUDY OF THE AIR ENTRAINMENT FOR SELF ASPIRING BURNERS

This work presents an experimental and numerical study addressing the effects of air entrainment for self aspiring burners. Within this framework, the work focus on the analysis of four different burners tested with four different nozzles, resulting in a total of sixteen different configurations. The gas used for the tests was methane. Each nozzle diameter provided a different flow rate, which also resulted in a different entrainment, therefore a different oxygen concentration on the ports area, which was measured using an oxygen sensor. The level of oxygen decreased with the increase of the flow rate of the gas, and had a linear behavior with the nozzle diameter. The finite volume method with the realizable k-ε model was then applied to numerically investigate this phenomenon using the commercial software STARCCM+. The results shows that for the sixteen points tested the worst correlation had a relative error of 2.95%, while for the best one was of 0.04%

POLYMER MELT FLOW IN SUDDEN EXPANSIONS: THE EFFECTS OF VISCOUS HEATING

Sudden expansion is a typical geometry found at the entrance of a mould cavity and is generally known in industry as ‘gate’. Flow simulation of this class of problems poses some difficulties owing to coupling of momentum and energy laws, existence of re-circulation and steep pressure variations. This work focuses on the physical analysis of the laminar and incompressible polymer melt flow inside channels with sudden expansions aimed at mapping the viscous heating effect. The mathematical model comprises the mass, momentum and energy conservation laws. The pressure-velocity coupling is treated on solving a Poisson equation for pressure. The Cross constitutive model is adopted to describe the non-Newtonian behavior of the flow. The governing equations are discretized using the finite difference method based on central, second order accurate formulae for both convective and diffusive terms. Artificial smoothing terms are added to control the odd-even decoupling problem. The main results demonstrate that the flow parameters, such as pressure drop along the channel and Nusselt number at the walls, are affected by viscous heating. It has been found that, in such problems, any reliable solution must account for the non-isothermal effects

AN EXPERIMENTAL STUDY OF THE CONVECTIVE HEAT TRANSFER ENHANCEMENT: APPLICATION OF TURBULENCE PROMOTERS

This work presents an experimental study addressing the effects of turbulence promoters on heat transfer rate at circular cylinder in external cross flow. Within this framework, the work focuses on assessing the effects of three kind of turbulence promoters (with circular, square and hexagonal cross sections) on convective heat transfer enhancement. The distance from turbulence promoters to the circular cylinder (50, 100 and 150mm upstream), as well as the free stream velocity inside the wind tunnel (Reynolds number) were the parameters investigated. The validation of the experimental methodology was performed by comparing the present results with empiric correlations available in the literature. The main results indicate that the convective heat transfer coefficient was enhanced when using turbulence promoters. The highest heat transfer enhancement obtained was around 25% correponding to the case of square turbulence promoter placed closely (50mm) to the circular cylinder. Finally, it is worth mentioning that all the experimental results for the convective coefficient were condensed in a new empirical correlation with good accuracy

Conjugated Heat and Mass Transfer in Convective Drying in Compact Wood Kilns: A System Approach

Drying is a required operation in timber manufacturing industries. Most drying processes utilise convective kilns, which involve coupling between transient heat and mass (moisture content) transfer in solids and convection in a flowing medium. In the present work, the flow field in the kiln is determined using a system approach based on a general head loss equation, whereas the coupling between transient heat and mass transfer in the timber is accomplished by a solution of a local differential model across the timber stack. The scheme is applied to study the effects of distinct geometric kiln configurations and air flow temperatures upon drying rates and moisture content

International Pediatric Otolaryngology Group (IPOG) consensus recommendations: Management of suprastomal collapse in the pediatric population.

Suprastomal Collapse (SuStCo) is a common complication of prolonged tracheostomy in children. There is a paucity of literature on this subject, especially regarding how to manage significant suprastomal collapse that prevents safe decannulation. Provide a definition, classification system, and recommend management options for significant suprastomal collapse in children with tracheostomy. Members of the International Pediatric Otolaryngology Group (IPOG) who are experts in pediatric airway conditions were surveyed and results were refined using a modified Delphi method. Consensus was defined as > 70% agreement on a subject. The experts achieved consensus: CONCLUSION: This consensus statement provides recommendations for medical specialists who manage infants and children with tracheostomies with significant Suprastomal Collapse. It provides a classification system to facilitate diagnosis and treatment options for this condition

IVORY Guidelines (Instructional Videos in Otorhinolaryngology by YO-IFOS): A Consensus on Surgical Videos in Ear, Nose, and Throat

Objectives/Hypothesis: Otolaryngology instructional videos available online are often of poor quality. The objective of this article was to establish international consensus recommendations for the production of educational surgical videos in otolaryngology. Study Design: DELPHI survey. Methods: Twenty-seven international respondents participated in this study from 12 countries. Consensus was reached after three rounds of questionnaires following the Delphi methodology. The proposals having reached the 80% agreement threshold in the third round were retained. Results: The main recommendations are as follows: 1) Ethics: patients must be anonymized and unrecognizable (apart from plastic surgery if necessary). A signed authorization must be obtained if the person is recognizable. 2) Technical aspects: videos should be edited and in high-definition (HD) quality if possible. Narration or subtitles and didactic illustrations are recommended. 3) Case presentation: name of pathology and procedure must be specified; the case should be presented with relevant workup. 4) Surgery: surgical procedures should be divided into several distinct stages and include tips and pitfalls. Pathology should be shown if relevant. Key points should be detailed at the end of the procedure. 5) Organ-specific: type of approach and bilateral audiometry should be specified in otology. Coronal plane computed tomography scans should be shown in endonasal surgery. It is recommended to show pre- and postoperative videos in voice surgery and preoperative drawings and photos of scars in plastic surgery, as well as the ventilation method in airway surgery. Conclusions: International recommendations have been determined to assist in the creation and standardization of educational surgical videos in otolaryngology and head and neck surgery. Level of Evidence: 5 Laryngoscope, 2020

Competency-Based Assessment Tool for Pediatric Tracheotomy: International Modified Delphi Consensus.

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163458/2/lary28461.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/163458/1/lary28461_am.pd