Water Air Bubble Grid Turbulence

The interaction of a swarm of bubbles with the isotropic grid turbulence generated in a vertical water channel has been studied experimentally. Measurements of local void fraction, mean velocity and all three turbulence intensity components are presented at a distance from the grid where isotropic turbulence prevails in single‐phase flow. At low gas flow rate the interaction is rather mild with minor redistribution of the void but significant increase of the turbulence intensity. High gas flow rates result in significant modifications of the flow structure. Void distribution presents maxima at locations between the center of the channel and the wall reminiscing of the Segre‐Sielberberg effect. Similar maxima are observed in mean velocity measurements at values much higher than the corresponding single‐phase flow. Turbulence intensity components increase is following different trends in longitudinal and transverse direction and the isotropy of the flow is destroyed.     

Optimal design and placement of serpentine heat exchangers for indirect heat withdrawal,inside flat plate integrated collector storage solar water heaters (ICSSWH)

Parameters that affect the temperature at which service hot water (SHW) is offered by an immersed tube heat exchanger (HX), inside a flat plate Integrated Collector Storage Solar Water Heater (ICSSWH), are examined numerically, by means of Computational Fluid Dynamics (CFD) analysis. The storage water is not refreshed and serves for heat accumulation. Service hot water is drawn off indirectly, through an immersed serpentine heat exchanger. For the intensification of the heat transfer process, the storage water is agitated by recirculation through a pump, which goes on only when service water flows inside the heat exchanger. Three main factors, which influence the performance, are optimized: The position of the HX relative to tank walls, the HX length and the tube diameter. All three factors are explored so that to maximize the service water outlet temperature. The settling time of the optimum configuration is also computed. Various 3-D CFD models were developed using the FLUENT package. The heat transfer rate between the two circuits of the optimum configuration is maintained at high levels, leading to service water outlet temperatures by 1–7 °C lower than tank water temperatures, for the examined SHW flow rates. The settling time is retained at sufficient law values, such as 20 s. The optimal position was found to lay the HX in contact with the front and back walls of the tank, with an optimum inner tube diameter of 16 mm, while an acceptable HX length was found to be about 21.5 m.     

Cone Calorimeter and Thermogravimetric Analysis of Glass Phenolic Composites Used in Aircraft Applications

The increasing use of composite materials in aircraft cabins and structures poses significant challenges in order to maintain and improve the fire safety of aviation. In this work, the flammability characteristics of a commercial glass-fibre reinforced phenolic composite (GFRP) used for aircraft cabin partitions and furnishing are investigated experimentally. Thermogravimetric analysis under inert atmosphere at several heating rates provided information on the thermal decomposition process. The degradation process is modelled with one and two-step mechanisms using the Ozawa–Flynn–Wall iso-conversional method and the GPYRO numerical code which utilizes a genetic algorithm optimization scheme. The estimated activation energy and pre-exponential factor values, especially in the two-step case (77.18 and 104.69 kJ/mol and 2.60 × 106 and 3.19 × 106 min−1 for the first and the second step respectively), recover reasonably well the conversion degree and its derivative. Tests with a cone calorimeter (CC), performed at different incident heat fluxes, provided information on the reaction to fire characteristics of the material and the influence of the heat flux on the combustion process. In general, combustion proceeds in two stages, flaming and smoldering combustion. The CC results assisted by scanning electron microscopy photos provide information on the charring characteristics of the material. The critical heat flux for ignition and the corresponding ignition temperature are estimated, correlating heat fluxes with time to ignition. Thermally thin and thick models are considered, as well as a modified technique bridging the gap between these limit cases and therefore valid for thermally thin and thick but also intermediate conditions (more pertinent in the present case). The results for this latter approach are $$\dot{q}^{\prime\prime}_{ig,cr}$$ ~ 20 kW/m2 and Tig = 469°C, providing also complementing information on thermophysical properties, such as thermal diffusivity, α = 1.23 × 10−7 m2/s, thermal conductivity, k = 0.325 W/(m K) and specific heat capacity, c = 1.330 kJ/(kg K). This work provides information on the reaction to fire characteristics of GFRP, but also on physical and flammability properties in a form suitable to be used in numerical codes, for the prediction of fire and evacuation scenarios. The influence of the reinforcement structure on the fire behaviour of the composite is also illustrated and discussed.     

Unexpected increase of the CA 19-9 tumour marker in patients with endometriosis

The purpose of this study was to investigate whether the ovarian function of women with endometriosis could be identified by serologic concentration of the oncofetal antigen CA 19-9 before, during and after treatment for 6 months with danazol. A total of 15 women with endometriosis, 20-40 years old, were studied. The serum CA 19-9 antigen was measured by immunoradiometric assay. The measurement of CA 19-9 was repeated during the last 15 days of a 6-month therapy period with danazol and after 3 months from the end of the therapy in only seven women. It was found that: 1) Eight out of 15 women (53.3%) showed higher CA 19-9 values than the upper normal limit. 2) Danazol caused a significant decrease in the antigen values which remained stable after the cessation of therapy. This data suggests that endometriosis should be classified among other diseases which cause an increase in the serum levels of CA 19-9 and that ovarian function is related to antigen levels.     

Subfertility associated with minimal to mild endometriosis. Main mechanisms

Our knowledge of the relationship between minimal to mild endometriosis and subfertility is limited. The main reason for this lack of progress is most probably that the mechanism of subfertility remains to be determined. It has been claimed that mild endometriosis causes subfertility in a variety of ways--ovulation disturbances, inhibition of ovum uptake, dysfunction of the oviducts, recurrent abortions, decrease in implantation, modified response to the immune system and endoperitoneal inflammation. Currently, minimal to mild endometriosis is associated with subfertility of unknown etiology.     

Decreased sensitivity to insulin during treatment with danazol in women with endometriosis

Reconstruction techniques for major vessels and intracardiac defect repair use synthetic grafts or autogenic pericardium. Here, autologous abdominal parietal peritoneum with the overlying posterior rectus sheath as a biologic membrane are evaluated. Twelve adult canines were used. Via a midline subumbilical incision, the parietal peritoneum and overlying posterior rectus sheath were harvested. In the first group of six, the membrane was used to repair the right ventricular infundibulum and perform pulmonary artery annuloplasty. In the second group of six, under cardiopulmonary bypass and moderate hypothermia, the right atrium was opened and a secundum type defect was created. Autopsies performed 90 days after surgery revealed mild intrapericardial adhesions and moderate pericardial reaction over the cardiotomy incisions. The right ventricular outflow tract patch was nonaneurysmal. The interatrial patch was intact without thrombi. Histologic examination revealed intact membrane morphology, fibroblasts, smooth muscle cells, and endothelialization. Proline C14 uptake and autoradiography detected cellular viability of implanted membranes. These findings suggest that the peritoneum with overlying sheath repaired vascular and intracardiac defects and substituted for pericardium. Future studies are needed before clinical use.