scholarly journals Influence of probe geometry on measurement results of non-ideal thermal conductivity sensors

2016 ◽  
Vol 5 (2) ◽  
pp. 383-401 ◽  
Author(s):  
Patrick Tiefenbacher ◽  
Norbert I. Kömle ◽  
Wolfgang Macher ◽  
Günter Kargl
Keyword(s):  
Thermal Conductivity ◽  
Thermal Evolution ◽  
Temperature Response ◽  
Electrical Current ◽  
Diameter Ratio ◽  
The Body ◽  
Ir Radiation ◽  
Contact Points ◽  
Planetary Bodies ◽  
Length To Diameter Ratio

Abstract. The thermal properties of the surface and subsurface layers of planets and planetary objects yield important information that allows us to better understand the thermal evolution of the body itself and its interactions with the environment. Various planetary bodies of our Solar System are covered by so-called regolith, a granular and porous material. On such planetary bodies the dominant heat transfer mechanism is heat conduction via IR radiation and contact points between particles. In this case the energy balance is mainly controlled by the effective thermal conductivity of the top surface layers, which can be directly measured by thermal conductivity probes. A traditionally used method for measuring the thermal conductivity of solid materials is the needle-probe method. Such probes consist of thin steel needles with an embedded heating wire and temperature sensors. For the evaluation of the thermal conductivity of a specific material the temperature change with time is determined by heating a resistance wire with a well-defined electrical current flowing through it and simultaneously measuring the temperature increase inside the probe over a certain time. For thin needle probes with a large length-to-diameter ratio it is mathematically easy to derive the thermal conductivity, while this is not so straightforward for more rugged probes with a larger diameter and thus a smaller length-to-diameter ratio. Due to the geometry of the standard thin needle probes they are mechanically weak and subject to bending when driven into a soil. Therefore, using them for planetary missions can be problematic. In this paper the thermal conductivity values determined by measurements with two non-ideal, ruggedized thermal conductivity sensors, which only differ in length, are compared to each other. Since the theory describing the temperature response of non-ideal sensors is highly complicated, those sensors were calibrated with an ideal reference sensor in various solid and granular materials. The calibration procedure and the results are described in this work.

scholarly journals Influence of probe geometry on measurement results of non-ideal thermal conductivity sensors

2016 ◽  
Author(s):  
P. Tiefenbacher ◽  
N. I. Kömle ◽  
W. Macher ◽  
G. Kargl
Keyword(s):  
Thermal Conductivity ◽  
Thermal Evolution ◽  
Temperature Response ◽  
Electrical Current ◽  
Diameter Ratio ◽  
The Body ◽  
Ir Radiation ◽  
Contact Points ◽  
Planetary Bodies ◽  
Length To Diameter Ratio

Abstract. The thermal properties of the surface and subsurface layers of planets and planetary objects yield important information that allows us to better understand the thermal evolution of the body itself and its interactions with the environment. Various planetary bodies of our Solar System are covered by so-called regolith, a granular and porous material. On such planetary bodies the dominant heat transfer mechanism is heat conduction via IR radiation and contact points between particles. In this case the energy balance is mainly controlled by the effective thermal conductivity of the top surface layers, that can be directly measured by thermal conductivity probes. A traditionally used method for measuring the thermal conductivity of solid materials is the needle-probe method. Such probes consist of thin steel needles with an embedded heating wire and temperature sensors. For the evaluation of the thermal conductivity of a specific material the temperature change with time is determined by heating a resistance wire with a well-defined electrical current flowing through it and simultaneously measuring the temperature increase inside the probe over a certain time. For thin needle probes with a large length-to-diameter ratio it is mathematically easy to derive the thermal conductivity, while this is not so straightforward for more rugged probes with a larger diameter and thus a smaller length-to-diameter ratio. Due to the geometry of the standard thin needle probes they are mechanically weak and subject to bending when driven into a soil. Therefore, using them for planetary missions can be problematic. In this paper the thermal conductivity values determined by measurements with two non-ideal, ruggedized thermal conductivity sensors, which only differ in length, are compared to each other. Since the theory describing the temperature response of non-ideal sensors is highly complicated, those sensors were calibrated with an ideal reference sensor in various solid and granular materials. The calibration procedure and the results are described in this work.

scholarly journals Calibration of non-ideal thermal conductivity sensors

2013 ◽  
Vol 2 (1) ◽  
pp. 151-156 ◽  
Author(s):  
N. I. Kömle ◽  
W. Macher ◽  
G. Kargl ◽  
M. S. Bentley
Keyword(s):  
Thermal Conductivity ◽  
Granular Material ◽  
Temperature Measurement ◽  
Temperature Response ◽  
Electrical Current ◽  
Diameter Ratio ◽  
Conductivity Sensor ◽  
Highly Nonlinear ◽  
Wide Range ◽  
Length To Diameter Ratio

Abstract. A popular method for measuring the thermal conductivity of solid materials is the transient hot needle method. It allows the thermal conductivity of a solid or granular material to be evaluated simply by combining a temperature measurement with a well-defined electrical current flowing through a resistance wire enclosed in a long and thin needle. Standard laboratory sensors that are typically used in laboratory work consist of very thin steel needles with a large length-to-diameter ratio. This type of needle is convenient since it is mathematically easy to derive the thermal conductivity of a soft granular material from a simple temperature measurement. However, such a geometry often results in a mechanically weak sensor, which can bend or fail when inserted into a material that is harder than expected. For deploying such a sensor on a planetary surface, with often unknown soil properties, it is necessary to construct more rugged sensors. These requirements can lead to a design which differs substantially from the ideal geometry, and additional care must be taken in the calibration and data analysis. In this paper we present the performance of a prototype thermal conductivity sensor designed for planetary missions. The thermal conductivity of a suite of solid and granular materials was measured both by a standard needle sensor and by several customized sensors with non-ideal geometry. We thus obtained a calibration curve for the non-ideal sensors. The theory describing the temperature response of a sensor with such unfavorable length-to-diameter ratio is complicated and highly nonlinear. However, our measurements reveal that over a wide range of thermal conductivities there is an almost linear relationship between the result obtained by the standard sensor and the result derived from the customized, non-ideal sensors. This allows for the measurement of thermal conductivity values for harder soils, which are not easily accessible when using standard needle sensors.

scholarly journals Calibration of non-ideal thermal conductivity sensors

2012 ◽  
Vol 2 (2) ◽  
pp. 685-701
Author(s):  
N. I. Kömle ◽  
W. Macher ◽  
G. Kargl ◽  
M. S. Bentley
Keyword(s):  
Thermal Conductivity ◽  
Granular Material ◽  
Temperature Measurement ◽  
Temperature Response ◽  
Electrical Current ◽  
Diameter Ratio ◽  
Conductivity Sensor ◽  
Highly Nonlinear ◽  
Wide Range ◽  
Length To Diameter Ratio

Abstract. A popular method for measuring the thermal conductivity of solid materials is the transient heated needle method. It allows to evaluate the thermal conductivity of a solid or granular material to be evaluated simply by combining a temperature measurement with a well-defined electrical current flowing through a resistance wire enclosed in a long and thin needle. Standard laboratory sensors that are typically used in laboratory work consist of very thin steel needles with a large length-to-diameter ratio. This type of needles is convenient since it is mathematically easy to derive the thermal conductivity of a soft granular material from a simple temperature measurement. However, such a geometry often results in a mechanically weak sensor, which can bend or fail when inserted into a material that is harder than expected. For deploying such a sensor on a planetary surface, with often unknown soil properties, it is necessary to construct more rugged sensors. These requirements can lead to a design which differs substantially from the ideal geometry, and additional care must be taken in the calibration and data analysis. In this paper we present the performance of a prototype thermal conductivity sensor designed for planetary missions. The thermal conductivity of a suite of solid and granular materials was measured both by a standard needle sensor and by several customized sensors with non-ideal geometry. We thus obtained a calibration curve for the non-ideal sensors. The theory describing the temperature response of a sensor with such unfavorable length-to-diameter ratio is complicated and highly nonlinear. However, our measurements reveal that over a wide range of thermal conductivities there is an almost linear relationship between the result obtained by the standard sensor and the result derived from the customized, non-ideal sensors. This allows to measure thermal conductivity values for harder soils, which are not easily accessible when using standard needle sensors.

Stagnant lid convection with temperature-dependent thermal conductivity and the thermal evolution of icy worlds

2020 ◽  
Vol 224 (3) ◽  
pp. 1870-1889
Author(s):  
Frédéric Deschamps
Keyword(s):  
Thermal Conductivity ◽  
Thermal Evolution ◽  
Heat Fluxes ◽  
The Body ◽  
Temperature Dependent ◽  
Temperature Dependent Conductivity ◽  
Icy Bodies ◽  
Main Component ◽  
The Impact ◽  
Temperature Dependent Thermal Conductivity

SUMMARY Convection is an efficient process to release heat from planetary interiors, but its efficiency depends on the detailed properties of planetary mantles and materials. A property whose impact has not yet been studied extensively is the temperature dependence of thermal conductivity. Because thermal conductivity controls heat fluxes, its variations with temperature may alter heat transfer. Here, I assess qualitatively and quantitatively the influence of temperature-dependent thermal conductivity on stagnant lid convection. Assuming that thermal conductivity varies as the inverse of temperature $(k \propto 1/T)$, which is the case for ice Ih, the main component of outer shells of solar System large icy bodies, I performed numerical simulations of convection in 3-D-Cartesian geometry with top-to-bottom viscosity and conductivity ratios in the ranges 105 ≤ Δη ≤ 108 and 1 ≤ Rk ≤ 10, respectively. These simulations indicate that with increasing Rk, and for given values of the Rayleigh number and Δη, heat flux is reduced by a factor Rk0.82, while the stagnant lid is thickening. These results have implications for the structures and thermal evolutions of large icy bodies, the impact of temperature-dependent conductivity being more important with decreasing surface temperature, Tsurf. The heat fluxes and thermal evolutions obtained with temperature-dependent conductivity are comparable to those obtained with constant conductivity, provided that the conductivity is fixed to its value at the bottom or in the interior of the ice shell, that is, around 2.0–3.0 W m−1 K−1, depending on the body. By contrast, temperature-dependent conductivity leads to thicker stagnant lids, by about a factor 1.6–1.8 at Pluto (Tsurf = 40 K) and a factor 1.2–1.4 at Europa (Tsurf = 100 K), and smaller interior temperatures. Overall, temperature-dependent thermal conductivity therefore provides more accurate descriptions of the thermal evolutions of icy bodies.

scholarly journals Rolling Moment of Slender Body at High Incidence for Air to Air Missile Rocket Applications

2020 ◽  
Vol 70 (1) ◽  
pp. 18-22
Author(s):  
Priyank Kumar
Keyword(s):  
Diameter Ratio ◽  
The Body ◽  
Slender Body ◽  
Control Technique ◽  
Angle Of Incidence ◽  
Rolling Moment ◽  
Side Force ◽  
High Incidence ◽  
Nose Shape ◽  
Length To Diameter Ratio

Measurements of moments were carried out on a slender body having a pointed forebody at lower velocities. The slender body had an ogive nose shape and an overall length to diameter ratio of 16. The angle of incidence was varied from low to moderate angles of attack in the pitch plane. The main objective of the present investigation was to measure the rolling moments on the slender body with and without the control technique. The side force was reduced using a rectangular cross-sectioned ringplaced suitably on the body, however, the slender body was found to experience rolling moments which may be catastrophic.

The Role of Computer Modeling in Electrocardiography

1990 ◽  
Vol 29 (04) ◽  
pp. 282-288 ◽  
Author(s):  
A. van Oosterom
Keyword(s):  
Electrical Activity ◽  
Computer Modeling ◽  
Body Surface ◽  
Electrical Current ◽  
The Body ◽  
Volume Conductor ◽  
Current Generator ◽  
Cardiac Electrical Activity ◽  
Source Models

AbstractThis paper introduces some levels at which the computer has been incorporated in the research into the basis of electrocardiography. The emphasis lies on the modeling of the heart as an electrical current generator and of the properties of the body as a volume conductor, both playing a major role in the shaping of the electrocardiographic waveforms recorded at the body surface. It is claimed that the Forward-Problem of electrocardiography is no longer a problem. Several source models of cardiac electrical activity are considered, one of which can be directly interpreted in terms of the underlying electrophysiology (the depolarization sequence of the ventricles). The importance of using tailored rather than textbook geometry in inverse procedures is stressed.

Optimized growth of high length-to-diameter ratio Lu2O3 single crystal fibers by the LHPG method

CrystEngComm ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 1657-1662
Author(s):  
Na Zhang ◽  
Yuqing Yin ◽  
Jian Zhang ◽  
Tao Wang ◽  
Siyuan Wang ◽  
...  
Keyword(s):  
Solid State ◽  
Single Crystal ◽  
High Power ◽  
Diameter Ratio ◽  
Solid State Lasers ◽  
Crystal Fibers ◽  
High Length ◽  
Length To Diameter Ratio

Lu2O3 crystals have attracted intense attention due to their great potential in the field of high power solid-state lasers.

EXPERIMENTAL STUDY ON FLAME PROPAGATION IN A STRAIGHT PIPE

2016 ◽  
Vol 78 (8-3) ◽  
Author(s):  
Siti Zubaidah Sulaiman ◽  
Rafiziana Md Kasmani ◽  
A. Mustafa
Keyword(s):  
Experimental Study ◽  
Flame Propagation ◽  
Experimental Work ◽  
Diameter Ratio ◽  
Straight Pipe ◽  
Pipe Length ◽  
Operating Condition ◽  
Consistent Trend ◽  
Length To Diameter Ratio

Flame propagation in a closed pipe with diameter 0.1 m and 5.1 m long, as well as length to diameter ratio (L/D) of 51, was studied experimentally. Hydrogen/air, acetylene/air and methane/air with stoichiometric concentration were used to observe the trend of flame propagation throughout the pipe. Experimental work was carried out at operating condition: pressure 1 atm and temperature 273 K. Results showed that all fuels are having a consistent trend of flame propagation in one-half of the total pipe length in which the acceleration is due to the piston-like effect. Beyond the point, fuel reactivity and tulip phenomenon were considered to lead the flame being quenched and decrease the overpressures drastically. The maximum overpressure for all fuels are approximately 1.5, 7, 8.5 barg for methane, hydrogen, and acetylene indicating that acetylene explosion is more severe. 

Roller Skewing Behavior in Roller Bearings

1982 ◽  
Vol 104 (3) ◽  
pp. 311-320
Author(s):  
L. J. Nypan
Keyword(s):  
Diameter Ratio ◽  
Radial Load ◽  
Outer Race ◽  
Roller Bearings ◽  
Length To Diameter Ratio

Measurements of roller skewing of a 1.15 length to diameter ratio roller in 118 mm bore roller bearings of 0.18 and 0.21 mm (0.0073 and 0.0083 in.) clearance operating with a 4450 N (1000 lb) radial load at shaft speeds of 4000, 8000, and 12,000 rpm with outer race misalignment of 0, 0.5, and −0.5 deg are reported.

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