The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Christian Schmidt - One of the best experts on this subject based on the ideXlab platform.
-
Sand box experiments to evaluate the influence of subsurface Temperature Probe design on Temperature based water flux calculation
Hydrology and Earth System Sciences, 2011Co-Authors: Mathias Munz, Sascha E. Oswald, Christian SchmidtAbstract:Abstract. Quantification of subsurface water fluxes based on the one dimensional solution to the heat transport equation depends on the accuracy of measured subsurface Temperatures. The influence of Temperature Probe setup on the accuracy of vertical water flux calculation was systematically evaluated in this experimental study. Four Temperature Probe setups were installed into a sand box experiment to measure temporal highly resolved vertical Temperature profiles under controlled water fluxes in the range of ±1.3 m d−1. Pass band filtering provided amplitude differences and phase shifts of the diurnal Temperature signal varying with depth depending on water flux. Amplitude ratios of setups directly installed into the saturated sediment significantly varied with sand box hydraulic gradients. Amplitude ratios provided an accurate basis for the analytical calculation of water flow velocities, which matched measured flow velocities. Calculated flow velocities were sensitive to thermal properties of saturated sediment and to Temperature sensor spacing, but insensitive to thermal dispersivity equal to solute dispersivity. Amplitude ratios of Temperature Probe setups indirectly installed into piezometer pipes were influenced by thermal exchange processes within the pipes and significantly varied with water flux direction only. Temperature time lags of small sensor distances of all setups were found to be insensitive to vertical water flux.
-
Sand box experiments to evaluate the influence of subsurface Temperature Probe design on Temperature based water flux calculation
Hydrology and Earth System Sciences Discussions, 2011Co-Authors: Mathias Munz, Sascha E. Oswald, Christian SchmidtAbstract:Abstract. Quantification of subsurface water fluxes based on the one dimensional solution to the heat transport equation depends on the accuracy of measured subsurface Temperatures. The influence of Temperature Probe setup on the accuracy of vertical water flux calculation was systematically evaluated in this experimental study. Four Temperature Probe setups were installed into a sand box experiment to measure temporal highly resolved vertical Temperature profiles under controlled water fluxes in the range of ±1.3 m d−1. Pass band filtered time series provided amplitude and phase of the diurnal Temperature signal varying with depth depending on water flux. Amplitude ratios of setups directly installed into the saturated sediment significantly varied with sand box hydraulic gradients. Amplitude ratios provided an accurate basis for the analytical calculation of water flow velocities, which matched measured flow velocities. Calculated flow velocities were sensitive to thermal properties of saturated sediment and to Probe distance, but insensitive to thermal dispersivity equal to solute dispersivity. Amplitude ratios of Temperature Probe setups indirectly installed into piezometer pipes were influenced by thermal exchange processes within the pipes and significantly varied with water flux direction only. Temperature time lags of small Probe distances of all setups were found to be insensitive to vertical water flux.
Mathias Munz - One of the best experts on this subject based on the ideXlab platform.
-
Sand box experiments to evaluate the influence of subsurface Temperature Probe design on Temperature based water flux calculation
Hydrology and Earth System Sciences, 2011Co-Authors: Mathias Munz, Sascha E. Oswald, Christian SchmidtAbstract:Abstract. Quantification of subsurface water fluxes based on the one dimensional solution to the heat transport equation depends on the accuracy of measured subsurface Temperatures. The influence of Temperature Probe setup on the accuracy of vertical water flux calculation was systematically evaluated in this experimental study. Four Temperature Probe setups were installed into a sand box experiment to measure temporal highly resolved vertical Temperature profiles under controlled water fluxes in the range of ±1.3 m d−1. Pass band filtering provided amplitude differences and phase shifts of the diurnal Temperature signal varying with depth depending on water flux. Amplitude ratios of setups directly installed into the saturated sediment significantly varied with sand box hydraulic gradients. Amplitude ratios provided an accurate basis for the analytical calculation of water flow velocities, which matched measured flow velocities. Calculated flow velocities were sensitive to thermal properties of saturated sediment and to Temperature sensor spacing, but insensitive to thermal dispersivity equal to solute dispersivity. Amplitude ratios of Temperature Probe setups indirectly installed into piezometer pipes were influenced by thermal exchange processes within the pipes and significantly varied with water flux direction only. Temperature time lags of small sensor distances of all setups were found to be insensitive to vertical water flux.
-
Sand box experiments to evaluate the influence of subsurface Temperature Probe design on Temperature based water flux calculation
Hydrology and Earth System Sciences Discussions, 2011Co-Authors: Mathias Munz, Sascha E. Oswald, Christian SchmidtAbstract:Abstract. Quantification of subsurface water fluxes based on the one dimensional solution to the heat transport equation depends on the accuracy of measured subsurface Temperatures. The influence of Temperature Probe setup on the accuracy of vertical water flux calculation was systematically evaluated in this experimental study. Four Temperature Probe setups were installed into a sand box experiment to measure temporal highly resolved vertical Temperature profiles under controlled water fluxes in the range of ±1.3 m d−1. Pass band filtered time series provided amplitude and phase of the diurnal Temperature signal varying with depth depending on water flux. Amplitude ratios of setups directly installed into the saturated sediment significantly varied with sand box hydraulic gradients. Amplitude ratios provided an accurate basis for the analytical calculation of water flow velocities, which matched measured flow velocities. Calculated flow velocities were sensitive to thermal properties of saturated sediment and to Probe distance, but insensitive to thermal dispersivity equal to solute dispersivity. Amplitude ratios of Temperature Probe setups indirectly installed into piezometer pipes were influenced by thermal exchange processes within the pipes and significantly varied with water flux direction only. Temperature time lags of small Probe distances of all setups were found to be insensitive to vertical water flux.
Sascha E. Oswald - One of the best experts on this subject based on the ideXlab platform.
-
Sand box experiments to evaluate the influence of subsurface Temperature Probe design on Temperature based water flux calculation
Hydrology and Earth System Sciences, 2011Co-Authors: Mathias Munz, Sascha E. Oswald, Christian SchmidtAbstract:Abstract. Quantification of subsurface water fluxes based on the one dimensional solution to the heat transport equation depends on the accuracy of measured subsurface Temperatures. The influence of Temperature Probe setup on the accuracy of vertical water flux calculation was systematically evaluated in this experimental study. Four Temperature Probe setups were installed into a sand box experiment to measure temporal highly resolved vertical Temperature profiles under controlled water fluxes in the range of ±1.3 m d−1. Pass band filtering provided amplitude differences and phase shifts of the diurnal Temperature signal varying with depth depending on water flux. Amplitude ratios of setups directly installed into the saturated sediment significantly varied with sand box hydraulic gradients. Amplitude ratios provided an accurate basis for the analytical calculation of water flow velocities, which matched measured flow velocities. Calculated flow velocities were sensitive to thermal properties of saturated sediment and to Temperature sensor spacing, but insensitive to thermal dispersivity equal to solute dispersivity. Amplitude ratios of Temperature Probe setups indirectly installed into piezometer pipes were influenced by thermal exchange processes within the pipes and significantly varied with water flux direction only. Temperature time lags of small sensor distances of all setups were found to be insensitive to vertical water flux.
-
Sand box experiments to evaluate the influence of subsurface Temperature Probe design on Temperature based water flux calculation
Hydrology and Earth System Sciences Discussions, 2011Co-Authors: Mathias Munz, Sascha E. Oswald, Christian SchmidtAbstract:Abstract. Quantification of subsurface water fluxes based on the one dimensional solution to the heat transport equation depends on the accuracy of measured subsurface Temperatures. The influence of Temperature Probe setup on the accuracy of vertical water flux calculation was systematically evaluated in this experimental study. Four Temperature Probe setups were installed into a sand box experiment to measure temporal highly resolved vertical Temperature profiles under controlled water fluxes in the range of ±1.3 m d−1. Pass band filtered time series provided amplitude and phase of the diurnal Temperature signal varying with depth depending on water flux. Amplitude ratios of setups directly installed into the saturated sediment significantly varied with sand box hydraulic gradients. Amplitude ratios provided an accurate basis for the analytical calculation of water flow velocities, which matched measured flow velocities. Calculated flow velocities were sensitive to thermal properties of saturated sediment and to Probe distance, but insensitive to thermal dispersivity equal to solute dispersivity. Amplitude ratios of Temperature Probe setups indirectly installed into piezometer pipes were influenced by thermal exchange processes within the pipes and significantly varied with water flux direction only. Temperature time lags of small Probe distances of all setups were found to be insensitive to vertical water flux.
Terry V. Jones - One of the best experts on this subject based on the ideXlab platform.
-
Transient Temperature Probe measurements in a Mach 4 nitrogen jet
Experiments in Fluids, 2004Co-Authors: David R. Buttsworth, Terry V. JonesAbstract:Stagnation Temperature measurements have been obtained in a Mach 4 free jet of nitrogen using a technique based on transient thin film heat flux Probe measurements. The uncertainty in the stagnation Temperature measurements depends on the Probe location within the jet but is typically around ±5 K at the centre of the jet. The thin film heat flux Probe technique also provides a measurement of the heat transfer coefficient of the thin film Probes with an uncertainty of around ±4% at the centre of the jet. Pitot pressure measurements were also obtained within the jet. Analysis of the heat transfer coefficient results yields the Mach number and velocity profiles which are compared with results from the pitot Probe measurements. Jet velocities identified using the thin film Probe and the pitot Probe techniques produce results with uncertainties of less than ±2% at the centre of the jet. Measurements of RMS stagnation Temperature fluctuations indicate values of around 3 K at the centre of the jet to more than 10 K in the shear layer.
-
A Fast-Response High Spatial Resolution Total Temperature Probe Using a Pulsed Heating Technique
Journal of Turbomachinery, 1998Co-Authors: David R. Buttsworth, Terry V. JonesAbstract:This paper discusses the operation of fast-response total Temperature Probe based on transient thin film heat flux gage technology. The Probe utilizes two thin film gages located close to the stagnation point of hemispherically blunted fused quartz cylinder. Development of the present total Temperature Probe was motivated by the need for a fast-response device with a high spatial resolution. The diameter of the Probe was 2.8 mm and the two films were separated by a distance of less than 1 mm. Measurement of the flow total Temperature requires the films to operate at different Temperatures. In the present work, the Temperature difference was generated using a current pulse (approximately 70 mA with a duration of around 1 s) to heat one of the thin film resistance gages. With this technique, Temperature differences between the hot and cold films of around 120 K were achieved. The interpretation of the transient surface Temperature measurements is discussed, and the validity and utility of the technique are demonstrated with reference to total Temperature and convective heat transfer coefficient measurements in a compressible free jet. The results demonstrate that accurate total Temperature and convective heat transfer coefficient measurements with high spatial and temporal resolution can be obtained with the present device.
-
A Fast-Response High Spatial Resolution Total Temperature Probe Using a Pulsed Heating Technique
Volume 4: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls Diagnostics and Instrumentation; Education; IGTI Scholar, 1997Co-Authors: David R. Buttsworth, Terry V. JonesAbstract:This paper discusses the operation of a fast-response total Temperature Probe based on transient thin film heat flux gauge technology. The Probe utilizes two thin film gauges located close to the stagnation point of a hemispherically-blunted fused quartz cylinder. Development of the present total Temperature Probe was motivated by the need for a fast-response device with a high spatial resolution. The diameter of the Probe was 2.8 mm and the two films were separated by a distance of less than 1 mm. Measurement of the flow total Temperature requires the films to operate at different Temperatures. In the present work, the Temperature difference was generated using a current pulse (approximately 70 mA with a duration of around 1 s) to heat one of the thin film resistance gauges. With this technique, Temperature differences between the hot and cold films of around 120 K were achieved. The interpretation of the transient surface Temperature measurements is discussed, and the validity and utility of the technique are demonstrated with reference to total Temperature and convective heat transfer coefficient measurements in a compressible free jet. The results demonstrate that accurate total Temperature and convective heat transfer coefficient measurements with high spatial and temporal resolution can be obtained with the present device.Copyright © 1997 by ASME
Merdim Sonmez - One of the best experts on this subject based on the ideXlab platform.
-
mri active guidewire with an embedded Temperature Probe and providing a distinct tip signal to enhance clinical safety
Journal of Cardiovascular Magnetic Resonance, 2012Co-Authors: Merdim Sonmez, Christina E Saikus, Jamie A Bell, Dominique N Franson, Majdi Halabi, Anthony Z Faranesh, Richard J. Lederman, Cengizhan Ozturk, Ozgur KocaturkAbstract:The field of interventional cardiovascular MRI is hampered by the unavailability of active guidewires that are both safe and conspicuous. Heating of conductive guidewires is difficult to predict in vivo and disruptive to measure using external Probes. We describe a clinical-grade 0.035” (0.89 mm) guidewire for MRI right and left heart catheterization at 1.5 T that has an internal Probe to monitor Temperature in real-time, and that has both tip and shaft visibility as well as suitable flexibility. The design has an internal fiberoptic Temperature Probe, as well as a distal solenoid to enhance tip visibility on a loopless antenna. We tested different tip-solenoid configurations to balance heating and signal profiles. We tested mechanical performance in vitro and in vivo in comparison with a popular clinical nitinol guidewire. The solenoid displaced the point of maximal heating (“hot spot”) from the tip to a more proximal location where it can be measured without impairing guidewire flexion. Probe pullback allowed creation of lengthwise guidewire Temperature maps that allowed rapid evaluation of design prototypes. Distal-only solenoid attachment offered the best compromise between tip visibility and heating among design candidates. When fixed at the hot spot, the internal Probe consistently reflected the maximum Temperature compared external Probes. Real-time Temperature monitoring was performed during porcine left heart catheterization. Heating was negligible using normal operating parameters (flip angle, 45°; SAR, 1.01 W/kg); the Temperature increased by 4.2°C only during high RF power mode (flip angle, 90°; SAR, 3.96 W/kg) and only when the guidewire was isolated from blood cooling effects by an introducer sheath. The tip flexibility and in vivo performance of the final guidewire design were similar to a popular commercial guidewire. We integrated a fiberoptic Temperature Probe inside a 0.035” MRI guidewire. Real-time monitoring helps detect deleterious heating during use, without impairing mechanical guidewire operation, and without impairing MRI visibility. We therefore need not rely on prediction to ensure safe clinical operation. Future implementations may modulate specific absorption rate (SAR) based on Temperature feedback.
-
mri active guidewire with an embedded Temperature Probe and providing a distinct tip signal to enhance clinical safety
Journal of Cardiovascular Magnetic Resonance, 2012Co-Authors: Merdim Sonmez, Christina E Saikus, Jamie A Bell, Dominique N Franson, Majdi Halabi, Anthony Z Faranesh, Richard J. Lederman, Cengizhan Ozturk, Ozgur KocaturkAbstract:Background: The field of interventional cardiovascular MRI is hampered by the unavailability of active guidewires that are both safe and conspicuous. Heating of conductive guidewires is difficult to predict in vivo and disruptive to measure using external Probes. We describe a clinical-grade 0.035” (0.89 mm) guidewire for MRI right and left heart catheterization at 1.5 T that has an internal Probe to monitor Temperature in real-time, and that has both tip and shaft visibility as well as suitable flexibility. Methods: The design has an internal fiberoptic Temperature Probe, as well as a distal solenoid to enhance tip visibility on a loopless antenna. We tested different tip-solenoid configurations to balance heating and signal profiles. We tested mechanical performance in vitro and in vivo in comparison with a popular clinical nitinol guidewire. Results: The solenoid displaced the point of maximal heating (“hot spot”) from the tip to a more proximal location where it can be measured without impairing guidewire flexion. Probe pullback allowed creation of lengthwise guidewire Temperature maps that allowed rapid evaluation of design prototypes. Distal-only solenoid attachment offered the best compromise between tip visibility and heating among design candidates. When fixed at the hot spot, the internal Probe consistently reflected the maximum Temperature compared external Probes. Real-time Temperature monitoring was performed during porcine left heart catheterization. Heating was negligible using normal operating parameters (flip angle, 45°; SAR, 1.01 W/kg); the Temperature increased by 4.2°C only during high RF power mode (flip angle, 90°; SAR, 3.96 W/kg) and only when the guidewire was isolated from blood cooling effects by an introducer sheath. The tip flexibility and in vivo performance of the final guidewire design were similar to a popular commercial guidewire. Conclusions: We integrated a fiberoptic Temperature Probe inside a 0.035” MRI guidewire. Real-time monitoring helps detect deleterious heating during use, without impairing mechanical guidewire operation, and without impairing MRI visibility. We therefore need not rely on prediction to ensure safe clinical operation. Future implementations may modulate specific absorption rate (SAR) based on Temperature feedback.
