Aplicação da transformada integral generalizada e da transformação conforme na solução de um problema de convecção forçada laminar em dutos de setor de anel circular

ResumoEste trabalho descreve uma solução híbrida analítico‐numérica aplicando a técnica da transformada integral generalizada (TTIG) na transferência de calor por convecção forçada de um escoamento laminar fluido dinamicamente desenvolvido e termicamente em desenvolvimento de um fluido Newtoniano em dutos de seção transversal com formato de setor de anel circular sob condições de contorno de Dirichlet, considerando um perfil de temperatura uniforme na entrada. Para facilitar o tratamento analítico e a aplicação das condições de contorno uma transformação conforme foi utilizada, visando alterar o domínio para um sistema de coordenadas mais apropriado. Feito isso, a TTIG foi aplicada na equação da energia para obtenção do campo de temperatura. Os resultados numéricos foram obtidos para parâmetros térmicos de interesse, tais como: temperatura média de mistura, números de Nusselt local e médio e comprimento de entrada térmica. Estes resultados foram comparados, quando possível, com os valores disponíveis na literatura e apresentaram uma ótima concordância.AbstractThis work describes a hybrid analytical‐numerical solution employing the Generalized Integral Transform Technique (GITT) to forced convection heat transfer in hydrodynamically fully developed and thermally non‐developed Newtonian laminar flow inside annular sector ducts under Dirichlet boundary conditions, considering uniform temperature entrance profile. In order to facilitate the analytical treatment and the application of the boundary conditions, a Conformal Transform was utilized to change the domain into a more suitable coordinate system. Thereafter, the GITT was applied on the energy equation to obtain the temperature field. Numerical results were obtained for quantities of practical interest, such as bulk mean temperature, local and average Nusselt number, and thermal entry length. These results were compared, as much as possible, with the parameter values available in the literature and they presented a good agreement

EXPERIMENTAL ANALYSIS OF A SCREEN-COVERED GROOVE HEAT PIPE

In this research, a heat pipe with screen-covered groove capillary structure was experimentally analyzed. The heat pipe was manufactured from a copper tube with the external diameter of 9.45mm, inner diameter of      6.20mm, and a total length of 200mm. A Wire Electrical Discharge Machining, or Wire-EDM, was used to manufacture axial microgrooves in the heat pipe. A layer of phosphor bronze mesh #100 completed the capillary structure. Distilled water was the working fluid and the loading filling ratio was 60% of the evaporator volume. The condenser was cooled by air forced convection, the adiabatic section was insulated with fiberglass, and the evaporator was heated by an electrical resistor and it was insulated from the environment with aeronautic insulation. The heat pipe was tested in horizontal position, under different heat loads varying from 5 up to 30W. The experimental results showed that the screen-covered groove worked satisfactorily as a capillary structure

THERMAL PERFORMANCE OF THERMOSYPHON FOR DIFFERENT WORKING FLUIDS

In this paper, an experimental investigation was performed of the thermal performance of different working fluids in thermosyphons that can be used in thermal control of electronic equipment. The working fluids were considered acetone, water, ethanol, and methanol. The thermosyphon are manufactured of copper with an outer diameter of 9.45 mm, an inner diameter of 7.75 mm, a total length of 200 mm, whereas an evaporator of 80 mm length, an adiabatic region of 20 mm in length and a condenser of 100 mm in length. They were loaded with 1.39 ml of the working fluid, corresponding to a filling ratio of 40% of the evaporator volume. Experimental tests were performed in a vertical position considering thermal loads between 5W and 25W. The thermosyphons operated satisfactorily in all the tests. The operating temperature distribution as a function of time and the heat resistance behavior as a function of power dissipation have been presented for each analyzed working fluid. These results indicated that acetone is the working fluid that has the best thermal performance

Post-intervention Status in Patients With Refractory Myasthenia Gravis Treated With Eculizumab During REGAIN and Its Open-Label Extension

OBJECTIVE: To evaluate whether eculizumab helps patients with anti-acetylcholine receptor-positive (AChR+) refractory generalized myasthenia gravis (gMG) achieve the Myasthenia Gravis Foundation of America (MGFA) post-intervention status of minimal manifestations (MM), we assessed patients' status throughout REGAIN (Safety and Efficacy of Eculizumab in AChR+ Refractory Generalized Myasthenia Gravis) and its open-label extension. METHODS: Patients who completed the REGAIN randomized controlled trial and continued into the open-label extension were included in this tertiary endpoint analysis. Patients were assessed for the MGFA post-intervention status of improved, unchanged, worse, MM, and pharmacologic remission at defined time points during REGAIN and through week 130 of the open-label study. RESULTS: A total of 117 patients completed REGAIN and continued into the open-label study (eculizumab/eculizumab: 56; placebo/eculizumab: 61). At week 26 of REGAIN, more eculizumab-treated patients than placebo-treated patients achieved a status of improved (60.7% vs 41.7%) or MM (25.0% vs 13.3%; common OR: 2.3; 95% CI: 1.1-4.5). After 130 weeks of eculizumab treatment, 88.0% of patients achieved improved status and 57.3% of patients achieved MM status. The safety profile of eculizumab was consistent with its known profile and no new safety signals were detected. CONCLUSION: Eculizumab led to rapid and sustained achievement of MM in patients with AChR+ refractory gMG. These findings support the use of eculizumab in this previously difficult-to-treat patient population. CLINICALTRIALSGOV IDENTIFIER: REGAIN, NCT01997229; REGAIN open-label extension, NCT02301624. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that, after 26 weeks of eculizumab treatment, 25.0% of adults with AChR+ refractory gMG achieved MM, compared with 13.3% who received placebo

Minimal Symptom Expression' in Patients With Acetylcholine Receptor Antibody-Positive Refractory Generalized Myasthenia Gravis Treated With Eculizumab

The efficacy and tolerability of eculizumab were assessed in REGAIN, a 26-week, phase 3, randomized, double-blind, placebo-controlled study in anti-acetylcholine receptor antibody-positive (AChR+) refractory generalized myasthenia gravis (gMG), and its open-label extension

Experimental Study of a Cu-Mo Alloy Vapor Chamber

In this research, the thermal behavior of a vapor chamber embedded in the base of a heat sink was experimentally analyzed considering the influence of the heat source position. The vapor chamber was produced by a copper and molybdenum alloy with length of 240 mm, width of 54 mm, thickness of 3 mm, and capillary structures composed by copper screen meshes. The working fluid used was de-ionized water. The pure aluminum heat sink was cooled by air forced convection and the evaporator vapor chamber was heated using an electrical resistor simulating integrated circuit power dissipation. The experimental tests were done in a suction type wind tunnel with open return for a heat load varying from 20 to 80 W, for an airflow velocity varying from 1 to 4 m/s, and for three different heat source positions. The experimental results showed that, independently of the heat source position, the considered vapor chamber worked successfully, maintaining low operating temperature