European Archives of Oto-rhino-laryngology, Jun 29, 2013
The aim of the study was to compare device life of more recent indwelling voice prostheses Provox... more The aim of the study was to compare device life of more recent indwelling voice prostheses Provox Vega and Blom-Singer Dual Valve to device life of wellknown standard devices (Provox 2, Blom-Singer Classic). In a prospective, non-randomised study, device life of Blom-Singer Classic, Blom-Singer Dual Valve, Provox2, Provox Vega and Provox ActiValve voice prostheses was recorded in a group of 102 laryngectomised patients. In total 749 voice prosthesis were included. Average overall life time was 108 days, median 74 days. The prosthesis with the longest dwell time was the Provox ActiValve (median 291 days). Provox Vega had longer device life compared with Provox2 (median 92 days vs 66 days; p = 0.006) and compared with Blom-Singer Classic (median 92 days vs 69 days; p = 0.004). In conclusion, device lifetimes of Provox Vega and ActiValve were better than those of Provox2 and the Blom-Singer Classic. New voice prostheses, with a defined valve opening pressure (Provox Vega, Provox ActiValve, Blom-Singer Dual Valve) had longer lifetimes than prostheses without a defined opening pressure (Blom-Singer Classic and Provox 2).
Unterdruckbedingte Ventilöffnung bei Stimmprothesen – Echtzeitmessung des intraluminalen Ösophagusdruckes in vivo
Einleitung: Unterdruck im intrathorakalen Ösophagus während der Inspiration wird als Ursache für ... more Einleitung: Unterdruck im intrathorakalen Ösophagus während der Inspiration wird als Ursache für unerwünschte Ventilöffnungen von Stimmprothesen diskutiert. Ein messtechnischer Nachweis dieser negativen Druckdifferenz zwischen dem Ösophaguslumen dorsal der Stimmprothese[for full text, please go to the a.m. URL]
Heat transfer limitation in a vertical annular closed two-phase thermosyphon with small fill rates
Heat Recovery Systems and CHP, 1987
Abstract A thermosyphon with R113 as the working fluid employing fill ratios between 0.02 and 0.4... more Abstract A thermosyphon with R113 as the working fluid employing fill ratios between 0.02 and 0.4, i.e. 2 and 40% of the evaporator volume, was experimentally and theoretically investigated. A critical heat flux (for which dry-out occurs) was measured which increases from about 104W m−2 at 5% fill ratio to about 5 × 104W m−2 at 40% fill ratio. The theoretical predictions are in close agreement with the experimental results.
Ab~trlct-ln this paper the porous medium concept is adopted to build up a fundamental model for t... more Ab~trlct-ln this paper the porous medium concept is adopted to build up a fundamental model for two-phase flows inside mini channels. The capillary force which appears important for those problems is rigorously included in the model by following the same treatment as for porous media. Various applications of the developed model are demonstrated, among which are adiabatic co-and counter-current flows and heated forced and natural convective flows. Some fundamental results such as the two-phase pressure drop in a downflow, the flooding limit in a counter-current flow and dryout heat flux in natural convection boiling, are achieved and compared with previous studies available in the literature. With the main emphasis on the application to micro heat pipes, the model is used to predict the capillary limit of an operating micro heat pipe, to explain the liquid holdup phenomenon and to imply the onset and origin of the plug flow pattern. Future research needs are pointed out to refine this first version of a two-phase model and to apply it to additional practical applications.
Within the frame of the “JOULE” r & d programme of the Commission of the European Communities... more Within the frame of the “JOULE” r & d programme of the Commission of the European Communities a project is carried out to develop and investigate novel enhanced evaporation heat transfer surfaces with the aim to employ them in improved industrial two-phase heat exchangers. Main surfaces which are investigated are structured and covered planar and tubular surfaces and planar surfaces with narrow channels. Typical results obtained so far are presented which demonstrate the excellent evaporation heat transfer characteristics of these surfaces.
The velocity of nanoparticle agglomerates and 1 μm latex spheres approaching an impaction surface... more The velocity of nanoparticle agglomerates and 1 μm latex spheres approaching an impaction surface from a free gas jet was measured by LDA at pressures of 7.4 and 1.8 kPa, respectively. The "aerodynamically transparent" carbon nano-agglomerates gave sufficient LDA signal while the drag force was dominated by the size of the individual primary particles (diameter about 11 nm). The particle velocity as a function of distance from the impaction plate was also modelled on the basis of a CFD simulation of the flow field and subsequent numerical integration of the equation of motion with the slip correction factor as an adjustable parameter. For a pressure of 7.4 kPa the measured and calculated velocities agreed very well, when using the Stokes formula with classical parameters for the slip correction. Surprisingly however, at 1.8 kPa the effective drag on the nanoparticles was lower than predicted by a factor of 17 and on the 1 μm latex sphere by a factor of 6, respectively. The physical reason for this reduction of the drag is not known so far. The predicted particle impact velocity at 1.8 kPa was 54% of the maximum gas velocity. This factor is much lower than the often used factor of 0.85 derived by Marple.
European Archives of Oto-rhino-laryngology, Jun 29, 2013
The aim of the study was to compare device life of more recent indwelling voice prostheses Provox... more The aim of the study was to compare device life of more recent indwelling voice prostheses Provox Vega and Blom-Singer Dual Valve to device life of wellknown standard devices (Provox 2, Blom-Singer Classic). In a prospective, non-randomised study, device life of Blom-Singer Classic, Blom-Singer Dual Valve, Provox2, Provox Vega and Provox ActiValve voice prostheses was recorded in a group of 102 laryngectomised patients. In total 749 voice prosthesis were included. Average overall life time was 108 days, median 74 days. The prosthesis with the longest dwell time was the Provox ActiValve (median 291 days). Provox Vega had longer device life compared with Provox2 (median 92 days vs 66 days; p = 0.006) and compared with Blom-Singer Classic (median 92 days vs 69 days; p = 0.004). In conclusion, device lifetimes of Provox Vega and ActiValve were better than those of Provox2 and the Blom-Singer Classic. New voice prostheses, with a defined valve opening pressure (Provox Vega, Provox ActiValve, Blom-Singer Dual Valve) had longer lifetimes than prostheses without a defined opening pressure (Blom-Singer Classic and Provox 2).
Unterdruckbedingte Ventilöffnung bei Stimmprothesen – Echtzeitmessung des intraluminalen Ösophagusdruckes in vivo
Einleitung: Unterdruck im intrathorakalen Ösophagus während der Inspiration wird als Ursache für ... more Einleitung: Unterdruck im intrathorakalen Ösophagus während der Inspiration wird als Ursache für unerwünschte Ventilöffnungen von Stimmprothesen diskutiert. Ein messtechnischer Nachweis dieser negativen Druckdifferenz zwischen dem Ösophaguslumen dorsal der Stimmprothese[for full text, please go to the a.m. URL]
Heat transfer limitation in a vertical annular closed two-phase thermosyphon with small fill rates
Heat Recovery Systems and CHP, 1987
Abstract A thermosyphon with R113 as the working fluid employing fill ratios between 0.02 and 0.4... more Abstract A thermosyphon with R113 as the working fluid employing fill ratios between 0.02 and 0.4, i.e. 2 and 40% of the evaporator volume, was experimentally and theoretically investigated. A critical heat flux (for which dry-out occurs) was measured which increases from about 104W m−2 at 5% fill ratio to about 5 × 104W m−2 at 40% fill ratio. The theoretical predictions are in close agreement with the experimental results.
Ab~trlct-ln this paper the porous medium concept is adopted to build up a fundamental model for t... more Ab~trlct-ln this paper the porous medium concept is adopted to build up a fundamental model for two-phase flows inside mini channels. The capillary force which appears important for those problems is rigorously included in the model by following the same treatment as for porous media. Various applications of the developed model are demonstrated, among which are adiabatic co-and counter-current flows and heated forced and natural convective flows. Some fundamental results such as the two-phase pressure drop in a downflow, the flooding limit in a counter-current flow and dryout heat flux in natural convection boiling, are achieved and compared with previous studies available in the literature. With the main emphasis on the application to micro heat pipes, the model is used to predict the capillary limit of an operating micro heat pipe, to explain the liquid holdup phenomenon and to imply the onset and origin of the plug flow pattern. Future research needs are pointed out to refine this first version of a two-phase model and to apply it to additional practical applications.
Within the frame of the “JOULE” r & d programme of the Commission of the European Communities... more Within the frame of the “JOULE” r & d programme of the Commission of the European Communities a project is carried out to develop and investigate novel enhanced evaporation heat transfer surfaces with the aim to employ them in improved industrial two-phase heat exchangers. Main surfaces which are investigated are structured and covered planar and tubular surfaces and planar surfaces with narrow channels. Typical results obtained so far are presented which demonstrate the excellent evaporation heat transfer characteristics of these surfaces.
The velocity of nanoparticle agglomerates and 1 μm latex spheres approaching an impaction surface... more The velocity of nanoparticle agglomerates and 1 μm latex spheres approaching an impaction surface from a free gas jet was measured by LDA at pressures of 7.4 and 1.8 kPa, respectively. The "aerodynamically transparent" carbon nano-agglomerates gave sufficient LDA signal while the drag force was dominated by the size of the individual primary particles (diameter about 11 nm). The particle velocity as a function of distance from the impaction plate was also modelled on the basis of a CFD simulation of the flow field and subsequent numerical integration of the equation of motion with the slip correction factor as an adjustable parameter. For a pressure of 7.4 kPa the measured and calculated velocities agreed very well, when using the Stokes formula with classical parameters for the slip correction. Surprisingly however, at 1.8 kPa the effective drag on the nanoparticles was lower than predicted by a factor of 17 and on the 1 μm latex sphere by a factor of 6, respectively. The physical reason for this reduction of the drag is not known so far. The predicted particle impact velocity at 1.8 kPa was 54% of the maximum gas velocity. This factor is much lower than the often used factor of 0.85 derived by Marple.
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