Detlef Lazik - Academia.edu (original) (raw)
Papers by Detlef Lazik
Sensors
A knowledge of the moisture in soils/soil litter allows for the estimation of irrigation needs or... more A knowledge of the moisture in soils/soil litter allows for the estimation of irrigation needs or the risk of forest fire. A membrane-based humidity sensor (MHS) can measure the relative humidity (RH) as an average value in such heterogeneous substrates via its sensitive tubular silicone membrane. This RH corresponds to the moisture-dependent water potential of the substrate. For humid conditions in soil, however, the RH is already larger than 98% and hence is insensitively correlated with the water potential. For such conditions, a step-like response of the MHS was found, which occurs if the silicone membrane is wetted with water. This appears to correspond to oversaturated water vapor and must be attributed to a phase-dependent sorption mechanism of the membrane. This effect allows the expansion of the range of applications of the MHS in the detection of liquid water, such as in dew point detection. Based on this, the dependency of the measurement signal on the mean water saturati...
2016 IEEE SENSORS, 2016
A 400 m2 soil test field with gas injection system was built up, which enables an experimental va... more A 400 m2 soil test field with gas injection system was built up, which enables an experimental validation of linear gas sensors for specific applications and gases in an application-relevant scale. Several injection and soil watering experiments with carbon dioxide (CO2) at different days with varying boundary conditions were performed indicating the potential of the method for, e. g., rapid leakage detection with respect to Carbon Capture and Storage (CCS) issues.
tm - Technisches Messen, 2016
A 400 m2 soil test field with gas injection system was built up for the purpose of large-scale va... more A 400 m2 soil test field with gas injection system was built up for the purpose of large-scale validation, optimization, and characterization of a novel comprehensive monitoring method for underground gas storage areas. The method combines gas sensing technology with linear form factor for in-situ monitoring of gases in soil with the mapping capabilities of Computed Tomography (CT) to reconstruct time-series of gas distribution maps based on samples of orthogonally-aligned linear gas sensors. Several injection experiments with carbon dioxide (CO2) at different days with varying boundary conditions indicates the potential of the method for, e.g., rapid leakage detection with respect to Carbon Capture and Storage (CCS) issues.
Based on a multi-gas solution-diffusion problem for a dense symmetrical membrane this paper prese... more Based on a multi-gas solution-diffusion problem for a dense symmetrical membrane this paper presents a transient theory of a planar, membrane-based sensor cell for measuring gas from both initial conditions: dynamic and thermodynamic equilibrium. Using this theory, the ranges for which previously developed, simpler approaches are valid will be discussed; these approaches are of vital interest for membrane-based gas sensor applications. Finally, a new theoretical approach is introduced to identify varying gas components by arranging sensor cell pairs resulting in a concentration independent gas-specific critical time. Literature data for the N 2 , O 2 , Ar, CH 4 , CO 2 , H 2 and C 4 H 10 diffusion coefficients and solubilities for a polydimethylsiloxane membrane were used to simulate gas specific sensor responses. The results demonstrate the influence of (i) the operational mode; (ii) sensor geometry and (iii) gas matrices (air, Ar) on that critical time. Based on the developed theory the case-specific suitable membrane materials can be determined and both operation and design options for these sensors can be optimized for individual applications. The results of mixing experiments for different gases (O 2 , CO 2) in a gas matrix of air confirmed the theoretical predictions.
Sensors, 2022
A knowledge of the moisture in soils/soil litter allows for the estimation of irrigation needs or... more A knowledge of the moisture in soils/soil litter allows for the estimation of irrigation needs or the risk of forest fire. A membrane-based humidity sensor (MHS) can measure the relative humidity (RH) as an average value in such heterogeneous substrates via its sensitive tubular silicone membrane. This RH corresponds to the moisture-dependent water potential of the substrate. For humid conditions in soil, however, the RH is already larger than 98% and hence is insensitively correlated with the water potential. For such conditions, a step-like response of the MHS was found, which occurs if the silicone membrane is wetted with water. This appears to correspond to oversaturated water vapor and must be attributed to a phase-dependent sorption mechanism of the membrane. This effect allows the expansion of the range of applications of the MHS in the detection of liquid water, such as in dew point detection. Based on this, the dependency of the measurement signal on the mean water saturation in a substrate along the tubular membrane is demonstrated. A comparison of the measurement signal with an internal reference signal according to the MHS measurement principle makes it possible to distinguish this new, saturation-dependent measurement scale from the one used for RH measurement.
Most studies in the past focus on the measurement of CO2 release from the soil surface, which is ... more Most studies in the past focus on the measurement of CO2 release from the soil surface, which is the parameter of interest for balancing carbon fluxes. However, for advancing our mechanistic understanding measurement of CO2 concentration within the soil are required. Soil CO2 concentrations do not only relate directly to local production of CO2 by plants and soil biota, but are also a key for understanding soil solution chemistry (in particular pH dynamics). The relationship between soil CO2 concentration and CO2 flux at the soil surface will depend on the chemical gradients, the size and connectivity of air filled pore space (related to soil structure and actual water content), and temperature gradients in the system. CO2 production as well as soil water content and temperature show temporal variation directly or indirectly related to day night cycle and related plant growth. It was the aim of the present study to test a recently developed linear membrane-based gas sensor (line sen...
The invention concerns a column closure cap and a method of preparing and carrying out column inv... more The invention concerns a column closure cap and a method of preparing and carrying out column investigations using caps of this type, the method being applicable in particular for extracting undisturbed soil and rock samples for preparing and carrying out migration investigations in circulatory or continuous flow columns under water-saturated and unsaturated flow conditions. The column closure cap according to the invention is characterized in that the column closure cap is in two parts and comprises a cap (7) and at least one clamping ring (5), an O-ring (4) being disposed between the cap and the clamping ring and providing a sealed connection to the liner (12). The method according to the invention enables the conventional columns of double-flange construction to be dispensed with.
IAHS-AISH publication, 1998
In the Bitterfeld lignite seam aquitard we have observed asymmetric Gaussian-like concentration p... more In the Bitterfeld lignite seam aquitard we have observed asymmetric Gaussian-like concentration profiles of organic contaminants. Similar concentration profiles were observed in a clayey groundwater aquitard at Dover Air Force Base, Delaware. For a diffusion-based interpretation of these concentration profiles Ball et al. (1997) have derived an analytical solution for the two-aquitard diffusion problem. Applying this general solution, we derived for the first time an analytical expression for the contaminant release function f(t). The knowledge of this function is necessary both for forensic modelling of the case history and for predictive modelling of the future contaminant release of the aquitard.
The invention relates to a modular multichannel sample-taking and measuring system for automatic ... more The invention relates to a modular multichannel sample-taking and measuring system for automatic long-term analysis of fluids for hydrogeological field trials and laboratory tests. The inventive system can be used in environmental technology, especially in process monitoring in the field or in a laboratory. The modular expandable automatic multichannel measuring system provides a central measurement of physical, chemical and biological parameters for a selectable number of gaseous or liquid samples according to defined constant conditions.
Sensors, 2016
Linear membrane-based gas sensors that can be advantageously applied for the measurement of a sin... more Linear membrane-based gas sensors that can be advantageously applied for the measurement of a single gas component in large heterogeneous systems, e.g., for representative determination of CO 2 in the subsurface, can be designed depending on the properties of the observation object. A resulting disadvantage is that the permeation-based sensor response depends on operating conditions, the individual site-adapted sensor geometry, the membrane material, and the target gas component. Therefore, calibration is needed, especially of the slope, which could change over several orders of magnitude. A calibration-free approach based on an internal gas standard is developed to overcome the multi-criterial slope dependency. This results in a normalization of sensor response and enables the sensor to assess the significance of measurement. The approach was proofed on the example of CO 2 analysis in dry air with tubular PDMS membranes for various CO 2 concentrations of an internal standard. Negligible temperature dependency was found within an 18 K range. The transformation behavior of the measurement signal and the influence of concentration variations of the internal standard on the measurement signal were shown. Offsets that were adjusted based on the stated theory for the given measurement conditions and material data from the literature were in agreement with the experimentally determined offsets. A measurement comparison with an NDIR reference sensor shows an unexpectedly low bias (<1%) of the non-calibrated sensor response, and comparable statistical uncertainty.
BAM Federal Institute for Materials Research and Testing, in cooperation with the company MeGaSen... more BAM Federal Institute for Materials Research and Testing, in cooperation with the company MeGaSen UG carries out a research project to enhance and validate an innovative approach for distributed subsurface monitoring of gas storage areas. The concept combines different measurement technologies to one multifunctional sensor: membrane-based gas measurement technology for in-situ monitoring of gases in soil and fiber optical sensing of temperature and strain (as a measure for structural change). Key aspect of the research project is the first-time validation of the system in an application relevant dimension. For this purpose a 20 x 20 m 2 test field is build. A comprehensive validation of the system is carried out by systematic variation of different parameters like position-dependent gasinjection, temperature and mechanical impact.
International Journal of Greenhouse Gas Control, 2016
Abstract Geogenic gases from natural sources, carbon dioxide (CO2) from a geological repository (... more Abstract Geogenic gases from natural sources, carbon dioxide (CO2) from a geological repository (carbon capture and storage—CCS) or a leaking gas pipeline can present serious risks in industrial and urban areas. To extend the lead time for risk treatment in such critical regions, reliable detection of gases within the shallow subsurface is required to observe critical gas accumulations before degassing into the atmosphere. A near real-time monitoring approach is introduced to determine the volumetric expansion of a leaking gas in the subsurface. Considering the pressure relaxation with the ambient air pressure, the approach enables the forecasting of the final size of a pressurized gas body in terms of characteristic lengths. According to theoretical basics, such a characteristic length, which enables us to perform a gas (safety) measurement based on a purely geometrical measure, behaves independently of subsurface properties, i.e., it enables a reliable quantification of the escaping gas irrespective of its heterogeneous or changing flow path distribution. A field test for a 10 l/min pinhole leakage injected into a 10 m long, 0.4 m wide, 0.95 m deep soil-filled trench that was equipped with linear sensors shows the lateral-vertical volumetric gas expansion along these sensors, and demonstrates the applicability of the characteristic length approach.
Sensors, 2009
The representative measurement of gas concentration and fluxes in heterogeneous soils is one of t... more The representative measurement of gas concentration and fluxes in heterogeneous soils is one of the current challenges when analyzing the interactions of biogeochemical processes in soils and global change. Furthermore, recent research projects on CO 2-sequestration have an urgent need of CO 2-monitoring networks. Therefore, a measurement method based on selective permeation of gases through tubular membranes has been developed. Combining the specific permeation rates of gas components for a membrane and Dalton's principle, the gas concentration (or partial pressure) can be determined by the measurement of physical quantities (pressure or volume) only. Due to the comparatively small permeation constants of membranes, the influence of the sensor on its surrounding area can be neglected. The design of the sensor membranes can be adapted to the spatial scale from the bench scale to the field scale. The sensitive area for the measurement can be optimized to obtain representative results. Furthermore, a continuous time-averaged measurement is possible where the time for averaging is simply controlled by the wall-thickness of the membrane used. The measuring method is demonstrated for continuous monitoring of O 2 and CO 2 inside of a sand filled Lysimeter. Using three sensor planes inside the sand pack, which were installed normal to the gas flow direction and a reference measurement system, we demonstrate the accuracy of the gas-detection for different flux-based boundary conditions.
Sensors, 2009
The representative measurement of gas concentration and fluxes in heterogeneous soils is one of t... more The representative measurement of gas concentration and fluxes in heterogeneous soils is one of the current challenges when analyzing the interactions of biogeochemical processes in soils and global change. Furthermore, recent research projects on CO 2-sequestration have an urgent need of CO 2-monitoring networks. Therefore, a measurement method based on selective permeation of gases through tubular membranes has been developed. Combining the specific permeation rates of gas components for a membrane and Dalton's principle, the gas concentration (or partial pressure) can be determined by the measurement of physical quantities (pressure or volume) only. Due to the comparatively small permeation constants of membranes, the influence of the sensor on its surrounding area can be neglected. The design of the sensor membranes can be adapted to the spatial scale from the bench scale to the field scale. The sensitive area for the measurement can be optimized to obtain representative results. Furthermore, a continuous time-averaged measurement is possible where the time for averaging is simply controlled by the wall-thickness of the membrane used. The measuring method is demonstrated for continuous monitoring of O 2 and CO 2 inside of a sand filled Lysimeter. Using three sensor planes inside the sand pack, which were installed normal to the gas flow direction and a reference measurement system, we demonstrate the accuracy of the gas-detection for different flux-based boundary conditions.
A multi-scale optical imaging technique was developed allowing for the 2D observation of two phas... more A multi-scale optical imaging technique was developed allowing for the 2D observation of two phase flow in porous media at two different scales simultaneously: Using two coupled cameras, a 2D flow cell (0.5 × 0.5m2) is recorded entirely at the bench scale and at the pore scale with a spatial resolution of 0.5 and 0.01 mm, respectively. The technique is applied to
A multi-scale optical imaging technique was developed allowing for the 2D observation of two phas... more A multi-scale optical imaging technique was developed allowing for the 2D observation of two phase flow in porous media at two different scales simultaneously: Using two coupled cameras, a 2D flow cell (0.5 × 0.5m2) is recorded entirely at the bench scale and at the pore scale with a spatial resolution of 0.5 and 0.01 mm, respectively. The technique is applied to
Materials Today: Proceedings
Materials Today: Proceedings
Materials Today: Proceedings
Sensors
A knowledge of the moisture in soils/soil litter allows for the estimation of irrigation needs or... more A knowledge of the moisture in soils/soil litter allows for the estimation of irrigation needs or the risk of forest fire. A membrane-based humidity sensor (MHS) can measure the relative humidity (RH) as an average value in such heterogeneous substrates via its sensitive tubular silicone membrane. This RH corresponds to the moisture-dependent water potential of the substrate. For humid conditions in soil, however, the RH is already larger than 98% and hence is insensitively correlated with the water potential. For such conditions, a step-like response of the MHS was found, which occurs if the silicone membrane is wetted with water. This appears to correspond to oversaturated water vapor and must be attributed to a phase-dependent sorption mechanism of the membrane. This effect allows the expansion of the range of applications of the MHS in the detection of liquid water, such as in dew point detection. Based on this, the dependency of the measurement signal on the mean water saturati...
2016 IEEE SENSORS, 2016
A 400 m2 soil test field with gas injection system was built up, which enables an experimental va... more A 400 m2 soil test field with gas injection system was built up, which enables an experimental validation of linear gas sensors for specific applications and gases in an application-relevant scale. Several injection and soil watering experiments with carbon dioxide (CO2) at different days with varying boundary conditions were performed indicating the potential of the method for, e. g., rapid leakage detection with respect to Carbon Capture and Storage (CCS) issues.
tm - Technisches Messen, 2016
A 400 m2 soil test field with gas injection system was built up for the purpose of large-scale va... more A 400 m2 soil test field with gas injection system was built up for the purpose of large-scale validation, optimization, and characterization of a novel comprehensive monitoring method for underground gas storage areas. The method combines gas sensing technology with linear form factor for in-situ monitoring of gases in soil with the mapping capabilities of Computed Tomography (CT) to reconstruct time-series of gas distribution maps based on samples of orthogonally-aligned linear gas sensors. Several injection experiments with carbon dioxide (CO2) at different days with varying boundary conditions indicates the potential of the method for, e.g., rapid leakage detection with respect to Carbon Capture and Storage (CCS) issues.
Based on a multi-gas solution-diffusion problem for a dense symmetrical membrane this paper prese... more Based on a multi-gas solution-diffusion problem for a dense symmetrical membrane this paper presents a transient theory of a planar, membrane-based sensor cell for measuring gas from both initial conditions: dynamic and thermodynamic equilibrium. Using this theory, the ranges for which previously developed, simpler approaches are valid will be discussed; these approaches are of vital interest for membrane-based gas sensor applications. Finally, a new theoretical approach is introduced to identify varying gas components by arranging sensor cell pairs resulting in a concentration independent gas-specific critical time. Literature data for the N 2 , O 2 , Ar, CH 4 , CO 2 , H 2 and C 4 H 10 diffusion coefficients and solubilities for a polydimethylsiloxane membrane were used to simulate gas specific sensor responses. The results demonstrate the influence of (i) the operational mode; (ii) sensor geometry and (iii) gas matrices (air, Ar) on that critical time. Based on the developed theory the case-specific suitable membrane materials can be determined and both operation and design options for these sensors can be optimized for individual applications. The results of mixing experiments for different gases (O 2 , CO 2) in a gas matrix of air confirmed the theoretical predictions.
Sensors, 2022
A knowledge of the moisture in soils/soil litter allows for the estimation of irrigation needs or... more A knowledge of the moisture in soils/soil litter allows for the estimation of irrigation needs or the risk of forest fire. A membrane-based humidity sensor (MHS) can measure the relative humidity (RH) as an average value in such heterogeneous substrates via its sensitive tubular silicone membrane. This RH corresponds to the moisture-dependent water potential of the substrate. For humid conditions in soil, however, the RH is already larger than 98% and hence is insensitively correlated with the water potential. For such conditions, a step-like response of the MHS was found, which occurs if the silicone membrane is wetted with water. This appears to correspond to oversaturated water vapor and must be attributed to a phase-dependent sorption mechanism of the membrane. This effect allows the expansion of the range of applications of the MHS in the detection of liquid water, such as in dew point detection. Based on this, the dependency of the measurement signal on the mean water saturation in a substrate along the tubular membrane is demonstrated. A comparison of the measurement signal with an internal reference signal according to the MHS measurement principle makes it possible to distinguish this new, saturation-dependent measurement scale from the one used for RH measurement.
Most studies in the past focus on the measurement of CO2 release from the soil surface, which is ... more Most studies in the past focus on the measurement of CO2 release from the soil surface, which is the parameter of interest for balancing carbon fluxes. However, for advancing our mechanistic understanding measurement of CO2 concentration within the soil are required. Soil CO2 concentrations do not only relate directly to local production of CO2 by plants and soil biota, but are also a key for understanding soil solution chemistry (in particular pH dynamics). The relationship between soil CO2 concentration and CO2 flux at the soil surface will depend on the chemical gradients, the size and connectivity of air filled pore space (related to soil structure and actual water content), and temperature gradients in the system. CO2 production as well as soil water content and temperature show temporal variation directly or indirectly related to day night cycle and related plant growth. It was the aim of the present study to test a recently developed linear membrane-based gas sensor (line sen...
The invention concerns a column closure cap and a method of preparing and carrying out column inv... more The invention concerns a column closure cap and a method of preparing and carrying out column investigations using caps of this type, the method being applicable in particular for extracting undisturbed soil and rock samples for preparing and carrying out migration investigations in circulatory or continuous flow columns under water-saturated and unsaturated flow conditions. The column closure cap according to the invention is characterized in that the column closure cap is in two parts and comprises a cap (7) and at least one clamping ring (5), an O-ring (4) being disposed between the cap and the clamping ring and providing a sealed connection to the liner (12). The method according to the invention enables the conventional columns of double-flange construction to be dispensed with.
IAHS-AISH publication, 1998
In the Bitterfeld lignite seam aquitard we have observed asymmetric Gaussian-like concentration p... more In the Bitterfeld lignite seam aquitard we have observed asymmetric Gaussian-like concentration profiles of organic contaminants. Similar concentration profiles were observed in a clayey groundwater aquitard at Dover Air Force Base, Delaware. For a diffusion-based interpretation of these concentration profiles Ball et al. (1997) have derived an analytical solution for the two-aquitard diffusion problem. Applying this general solution, we derived for the first time an analytical expression for the contaminant release function f(t). The knowledge of this function is necessary both for forensic modelling of the case history and for predictive modelling of the future contaminant release of the aquitard.
The invention relates to a modular multichannel sample-taking and measuring system for automatic ... more The invention relates to a modular multichannel sample-taking and measuring system for automatic long-term analysis of fluids for hydrogeological field trials and laboratory tests. The inventive system can be used in environmental technology, especially in process monitoring in the field or in a laboratory. The modular expandable automatic multichannel measuring system provides a central measurement of physical, chemical and biological parameters for a selectable number of gaseous or liquid samples according to defined constant conditions.
Sensors, 2016
Linear membrane-based gas sensors that can be advantageously applied for the measurement of a sin... more Linear membrane-based gas sensors that can be advantageously applied for the measurement of a single gas component in large heterogeneous systems, e.g., for representative determination of CO 2 in the subsurface, can be designed depending on the properties of the observation object. A resulting disadvantage is that the permeation-based sensor response depends on operating conditions, the individual site-adapted sensor geometry, the membrane material, and the target gas component. Therefore, calibration is needed, especially of the slope, which could change over several orders of magnitude. A calibration-free approach based on an internal gas standard is developed to overcome the multi-criterial slope dependency. This results in a normalization of sensor response and enables the sensor to assess the significance of measurement. The approach was proofed on the example of CO 2 analysis in dry air with tubular PDMS membranes for various CO 2 concentrations of an internal standard. Negligible temperature dependency was found within an 18 K range. The transformation behavior of the measurement signal and the influence of concentration variations of the internal standard on the measurement signal were shown. Offsets that were adjusted based on the stated theory for the given measurement conditions and material data from the literature were in agreement with the experimentally determined offsets. A measurement comparison with an NDIR reference sensor shows an unexpectedly low bias (<1%) of the non-calibrated sensor response, and comparable statistical uncertainty.
BAM Federal Institute for Materials Research and Testing, in cooperation with the company MeGaSen... more BAM Federal Institute for Materials Research and Testing, in cooperation with the company MeGaSen UG carries out a research project to enhance and validate an innovative approach for distributed subsurface monitoring of gas storage areas. The concept combines different measurement technologies to one multifunctional sensor: membrane-based gas measurement technology for in-situ monitoring of gases in soil and fiber optical sensing of temperature and strain (as a measure for structural change). Key aspect of the research project is the first-time validation of the system in an application relevant dimension. For this purpose a 20 x 20 m 2 test field is build. A comprehensive validation of the system is carried out by systematic variation of different parameters like position-dependent gasinjection, temperature and mechanical impact.
International Journal of Greenhouse Gas Control, 2016
Abstract Geogenic gases from natural sources, carbon dioxide (CO2) from a geological repository (... more Abstract Geogenic gases from natural sources, carbon dioxide (CO2) from a geological repository (carbon capture and storage—CCS) or a leaking gas pipeline can present serious risks in industrial and urban areas. To extend the lead time for risk treatment in such critical regions, reliable detection of gases within the shallow subsurface is required to observe critical gas accumulations before degassing into the atmosphere. A near real-time monitoring approach is introduced to determine the volumetric expansion of a leaking gas in the subsurface. Considering the pressure relaxation with the ambient air pressure, the approach enables the forecasting of the final size of a pressurized gas body in terms of characteristic lengths. According to theoretical basics, such a characteristic length, which enables us to perform a gas (safety) measurement based on a purely geometrical measure, behaves independently of subsurface properties, i.e., it enables a reliable quantification of the escaping gas irrespective of its heterogeneous or changing flow path distribution. A field test for a 10 l/min pinhole leakage injected into a 10 m long, 0.4 m wide, 0.95 m deep soil-filled trench that was equipped with linear sensors shows the lateral-vertical volumetric gas expansion along these sensors, and demonstrates the applicability of the characteristic length approach.
Sensors, 2009
The representative measurement of gas concentration and fluxes in heterogeneous soils is one of t... more The representative measurement of gas concentration and fluxes in heterogeneous soils is one of the current challenges when analyzing the interactions of biogeochemical processes in soils and global change. Furthermore, recent research projects on CO 2-sequestration have an urgent need of CO 2-monitoring networks. Therefore, a measurement method based on selective permeation of gases through tubular membranes has been developed. Combining the specific permeation rates of gas components for a membrane and Dalton's principle, the gas concentration (or partial pressure) can be determined by the measurement of physical quantities (pressure or volume) only. Due to the comparatively small permeation constants of membranes, the influence of the sensor on its surrounding area can be neglected. The design of the sensor membranes can be adapted to the spatial scale from the bench scale to the field scale. The sensitive area for the measurement can be optimized to obtain representative results. Furthermore, a continuous time-averaged measurement is possible where the time for averaging is simply controlled by the wall-thickness of the membrane used. The measuring method is demonstrated for continuous monitoring of O 2 and CO 2 inside of a sand filled Lysimeter. Using three sensor planes inside the sand pack, which were installed normal to the gas flow direction and a reference measurement system, we demonstrate the accuracy of the gas-detection for different flux-based boundary conditions.
Sensors, 2009
The representative measurement of gas concentration and fluxes in heterogeneous soils is one of t... more The representative measurement of gas concentration and fluxes in heterogeneous soils is one of the current challenges when analyzing the interactions of biogeochemical processes in soils and global change. Furthermore, recent research projects on CO 2-sequestration have an urgent need of CO 2-monitoring networks. Therefore, a measurement method based on selective permeation of gases through tubular membranes has been developed. Combining the specific permeation rates of gas components for a membrane and Dalton's principle, the gas concentration (or partial pressure) can be determined by the measurement of physical quantities (pressure or volume) only. Due to the comparatively small permeation constants of membranes, the influence of the sensor on its surrounding area can be neglected. The design of the sensor membranes can be adapted to the spatial scale from the bench scale to the field scale. The sensitive area for the measurement can be optimized to obtain representative results. Furthermore, a continuous time-averaged measurement is possible where the time for averaging is simply controlled by the wall-thickness of the membrane used. The measuring method is demonstrated for continuous monitoring of O 2 and CO 2 inside of a sand filled Lysimeter. Using three sensor planes inside the sand pack, which were installed normal to the gas flow direction and a reference measurement system, we demonstrate the accuracy of the gas-detection for different flux-based boundary conditions.
A multi-scale optical imaging technique was developed allowing for the 2D observation of two phas... more A multi-scale optical imaging technique was developed allowing for the 2D observation of two phase flow in porous media at two different scales simultaneously: Using two coupled cameras, a 2D flow cell (0.5 × 0.5m2) is recorded entirely at the bench scale and at the pore scale with a spatial resolution of 0.5 and 0.01 mm, respectively. The technique is applied to
A multi-scale optical imaging technique was developed allowing for the 2D observation of two phas... more A multi-scale optical imaging technique was developed allowing for the 2D observation of two phase flow in porous media at two different scales simultaneously: Using two coupled cameras, a 2D flow cell (0.5 × 0.5m2) is recorded entirely at the bench scale and at the pore scale with a spatial resolution of 0.5 and 0.01 mm, respectively. The technique is applied to
Materials Today: Proceedings
Materials Today: Proceedings
Materials Today: Proceedings