No abstract

Proton resonance frequency thermometry can be used in a variety of complex flow situations to address medical as well as engineering questions. This work makes it possible to gain new insights into fundamental heat transfer phenomena. Magn Reson Med 76:145-155, 2016. © 2015 Wiley Periodicals, Inc.

No abstract

No abstract

Cyclone cooling is a promising method to enhance heat-transfer processes in future internal turbine-blade leading-edge cooling-ducts. The basic component of such cooling channels is the swirl generator, which induces a swirling movement of the coolant. The angular momentum generates stable, complex and three-dimensional flow structures of helical shape with alternating axial flow directions. Full three-dimensional and three-component velocity measurements using magnetic resonance velocimetry (3D3C-MRV) were conducted, with the aim to understand the complex structure of pipe flows with strong swirl. In order to mimic the effect of different installation concepts of the cyclone-cooling ducts an idealized bend-duct swirl-tube configuration with variable exit orifices has been investigated. Pronounced helical flow structures and distinct velocity zones could be found in this swirl flow. One substantial result is the identification of stationary helix-shaped streaks of high axial velocity in the direct vicinity of the wall. These findings are in good agreement with mass-transfer measurements that also show helix-shaped structures with increased mass transfer at the inner surface of the tube. According to the Reynolds analogy between heat and mass transfer, augmented heat-transfer processes in these areas are to be expected.

No abstract

Mechanical seals play an important role in the reliability of a process. Currently, the condition monitoring of mechanical seals is restricted due to the limitations of the traditional monitoring methods, including classical vibration analysis. For this reason, the objective of the present work is the detection and analysis of friction mechanisms inside a mechanical seal that are unfavorable and induce fault conditions using the acoustic emission technique, which allows the measurement of high-frequency vibrations that arise due to material fatigue processes on a microscopic scale. For this purpose, several fault condition modes were induced on a test rig of an agitator vessel system with a double-acting mechanical seal and its buffer fluid system. It was possible to detect the presence of inadequate friction mechanisms due to the absence and limited use of lubrication, as well as the presence of abrasive wear, by measuring a change in the properties of the acoustic emissions. Operation under fault condition modes was analyzed using the acoustic emission technique before an increase in the leakage rate was evaluated using traditional monitoring methods. The high friction due to the deficient lubrication was characterized by a pattern in the high-frequency range that consisted of the harmonics of a fundamental frequency of about 33 kHz. These results demonstrate the feasibility of a condition monitoring system for mechanical seals using the acoustic emission technique.

No abstract