Some Experimental Investigations on Gas Turbine Cooling Performed with Infrared Thermography at Federico II

This paper reviews some experimental measurements of convective heat transfer coefficient distributions which are connected with the cooling of gas turbines, performed by the authors' research group at the University of Naples Federico II with infrared thermography. Measurements concern impinging jets, cooling of rotating disks, and gas turbine blades, which are either stationary or rotating. The heated thin foil sensor, associated with the detection of surface temperature by means of infrared thermography, is exploited to accurately measure detailed convective heat transfer coefficient maps. The paper also intends to show how to correctly apply the infrared technique in a variety of gas turbines cooling problems

Continuum approach to wide shear zones in quasi-static granular matter

Slow and dense granular flows often exhibit narrow shear bands, making them ill-suited for a continuum description. However, smooth granular flows have been shown to occur in specific geometries such as linear shear in the absence of gravity, slow inclined plane flows and, recently, flows in split-bottom Couette geometries. The wide shear regions in these systems should be amenable to a continuum description, and the theoretical challenge lies in finding constitutive relations between the internal stresses and the flow field. We propose a set of testable constitutive assumptions, including rate-independence, and investigate the additional restrictions on the constitutive relations imposed by the flow geometries. The wide shear layers in the highly symmetric linear shear and inclined plane flows are consistent with the simple constitutive assumption that, in analogy with solid friction, the effective-friction coefficient (ratio between shear and normal stresses) is a constant. However, this standard picture of granular flows is shown to be inconsistent with flows in the less symmetric split-bottom geometry - here the effective friction coefficient must vary throughout the shear zone, or else the shear zone localizes. We suggest that a subtle dependence of the effective-friction coefficient on the orientation of the sliding layers with respect to the bulk force is crucial for the understanding of slow granular flows.Comment: 11 pages, 7 figure

Experimental analysis of the performance of fractal stirrers for impinging jets heat transfer enhancement

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.A new passive method for the heat transfer enhancement of circular impinging jets is proposed and tested. The method is based on enhancing the mainstream turbulence of impinging jets using square fractal grids, i.e. a grid with a square pattern repeated at increasingly smaller scales. Fractal grids can generate much higher turbulence intensity than regular grids under the same inflow conditions and with similar blockage ratio, at the expense of a slightly larger pressure drop. An experimental investigation on the heat transfer enhancement achieved by impinging jets with fractal turbulence promoters is carried out. The heated-thin foil technique is implemented to measure the spatial distribution of the Nusselt number on the target plate. The heat transfer rates of impinging jets with a regular grid and a fractal grid insert are compared to that of a jet without any turbulator under the same condition of power input. A parametric study on the effect of the Reynolds number, the nozzle-to-plate distance and the position of the insert within the nozzle is carried out. The results show that a fractal turbulence promoter can provide a significant heat transfer enhancement for relatively small nozzle-to-plate separation (at distance equal to 2 diameters 63% increase with respect to the circular jet at the stagnation point, and 25% if averaged over an area of radius equal to 1 nozzle diameter; respectively, against 9% and 6% of the regular grid in the same conditions of power input).dc201

Heat Transfer Measurements on a Rotating Disk

Heat transfer to a rotating disk is measured for a wide range of Reynolds number values in the laminar, transitional and turbulent flow regimes. Measurements are performed by making use of the heated-thin-foil technique and by gauging temperature maps with an infrared scanning radiometer. The use of the IR radiometer is advantageous on account of its relatively good spatial resolution and thermal sensitivity and because it allows one to perform measurements down to very low local Reynolds numbers. Data is obtained on three disks, having an external diameter varying from 150mm to 450mm; the smallest disk is used only to measure the adiabatic wall temperature and can rotate up to 21,O00rpm. Heat transfer results are presented in terms of Nusselt and Reynolds numbers based on the local radius and show a substantial agreement with previous experimental and theoretical analyses. Transition to turbulent flow is found at about Re=250,000. A discussion about the role played by the adiabatic wall temperature is also included

New Lipidomic Approaches in Cystic Fibrosis

Lipid analysis has been a crucial source of information in cystic fibrosis (CF). New methodologies for qualitative and quantitative lipidomics allow evaluation of a large number of samples, of special interest in patient screening for diagnostic and prognostic biological markers, as well as in cell physiology. In this chapter, two new complementary approaches are described: matrix-assisted laser desorption coupled to time of flight (MALDI-TOF-ClinProTools™) and liquid chromatography coupled to ion trap mass spectrometry (LC-MS( n )). MALDI-TOF-ClinProTools™ offers a large unbiased screening for the discovery of potential lipid alterations in diseased patients. LC-MS( n ) represents a state-of-the-art lipidomic tool for the identification and quantification of such alterations. The combination of both may open new perspectives in the quest for lipids participating in CF pathogenesis, therapy targets, and biomarkers