scholarly journals EXTRAPOLATION OF THE VERTICAL TEMPERATURE PROFILES DURING NOCTURNAL RADIATION INVERSION FROM SCREEN TEMPERATURE

MAUSAM ◽  
2021 ◽  
Vol 50 (1) ◽  
pp. 108-110
Author(s):  
B. PADMANABHAMURTY ◽  
INDU JAIN
Keyword(s):  
Temperature Profiles ◽  
Vertical Temperature ◽  
Screen Temperature

Prediction of Temperature Profiles in Fluid Bed Boilers

1978 ◽  
Vol 100 (3) ◽  
pp. 508-513 ◽  
Author(s):  
J. L. Hodges ◽  
R. C. Hoke ◽  
R. Bertrand
Keyword(s):  
Large Scale ◽  
Solid Material ◽  
Temperature Gradients ◽  
Temperature Profiles ◽  
Mixing Height ◽  
Vertical Temperature ◽  
Bed Temperature ◽  
Fluid Bed ◽  
Solids Mixing ◽  
Vertical Tubes

Data acquired in the Exxon Research and Engineering Company’s fluid bed boiler program indicate that the arrangement and orientation of internal boiler tubes has a strong effect on the measured bed temperature profile. Horizontally oriented tubes yield much steeper temperature gradients than do vertical tubes. Excessive vertical temperature gradients in coal fired fluid bed boilers can either limit coal feed rates or result in the formation of agglomerates of solid material which are destructive of bed internals. This study represents an attempt to understand the influence of orientation on vertical temperature profiles in fluid bed boilers. A back-mixing model for solids recirculation was developed and applied to the prediction of bed temperatures. Bubbling bed theory is not suitable for estimating solids circulation rates in pressurized beds of large particles with immersed tubes. However, by introducing the concept of a solids mixing height it was possible to estimate solid movement. The solids mixing height and vertical boiler tube dimensions were correlated in a manner which resulted in good agreement between theoretical and experimental bed temperature profiles. It is felt that this simple model may prove quite useful in the design of large scale commercial fluid bed boilers.

Wireless probes for measuring vertical temperature profiles in borehole heat exchangers (BHEs)

2021 ◽  
Author(s):  
Simon Schüppler ◽  
Roman Zorn ◽  
Hagen Steger ◽  
Philipp Blum
Keyword(s):  
Measurement Uncertainty ◽  
Fiber Optics ◽  
Heat Exchangers ◽  
Measurement Errors ◽  
High Reliability ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Distributed Temperature Sensing ◽  
Vertical Temperature ◽  
Borehole Heat Exchangers

<p>The measurement of the undisturbed ground temperature (UGT) serves to design low-temperature geothermal systems, in particular borehole heat exchangers (BHEs), and to monitor shallow aquifers. Wireless and miniaturized probes such as the Geosniff (GS) measurement sphere, which are characterized by an autarkic energy supply and equipped with pressure and temperature sensors, are increasingly being used for the measurement of highly resolved vertical temperature profiles. The measurement probe sinks along the course of the BHE with a selectable measurement frequency to the bottom of the BHE and is useable for initial measurements as well as long term groundwater monitoring. To ensure quality assurance and further improvement of this emerging technology, the analysis of measurement errors and uncertainties of wireless temperature measurements (WTMs) is indispensable. Thus, we provide an empirical laboratory analysis of random, systematic, and dynamic measurement errors, which lead to the measurement uncertainty of WTMs using the GS as a representative device. We subsequently transfer the analysed uncertainty to measured vertical temperature profiles of the undisturbed ground at a BHE site in Karlsruhe, Germany. The precision and accuracy of 0.011 K and -0.11 K, respectively, ensure a high reliability of the GS measurements. The largest measurement uncertainty is obtained within the first five meters of descent resulting from the thermal time constant τ of 4 s. The measured temperature profiles are qualitatively compared with common Distributed Temperature Sensing (DTS) using fiber optic cables and punctual Pt-100 sensors. Wireless probes are also suitable to correct temperature profiles recorded with fiber optics with systematic errors of up to -0.93 K. Various boundary conditions such as the inclination of the BHE pipes or changes of the viscosity and density of the BHE fluid effect the descent rate of the GS of up to 40 %. We additionally provide recommendations for technical implementations of future measurement probes and contribute to an improved understanding and further development of WTMs.</p>

scholarly journals Decoupling of a Douglas fir canopy: a look into the subcanopy with continuous vertical temperature profiles

2020 ◽  
Vol 17 (24) ◽  
pp. 6423-6439
Author(s):  
Bart Schilperoort ◽  
Miriam Coenders-Gerrits ◽  
César Jiménez Rodríguez ◽  
Christiaan van der Tol ◽  
Bas van de Wiel ◽  
...  
Keyword(s):  
Forest Floor ◽  
Thermal Stratification ◽  
Douglas Fir ◽  
Temperature Profiles ◽  
Distributed Temperature Sensing ◽  
Vertical Temperature ◽  
Vertical Exchange ◽  
Forest Sites ◽  
Flux Measurements ◽  
Atmosphere Interaction

Abstract. Complex ecosystems such as forests make accurately measuring atmospheric energy and matter fluxes difficult. One of the issues that can arise is that parts of the canopy and overlying atmosphere can be turbulently decoupled from each other, meaning that the vertical exchange of energy and matter is reduced or hampered. This complicates flux measurements performed above the canopy. Wind above the canopy will induce vertical exchange. However, stable thermal stratification, when lower parts of the canopy are colder, will hamper vertical exchange. To study the effect of thermal stratification on decoupling, we analyze high-resolution (0.3 m) vertical temperature profiles measured in a Douglas fir stand in the Netherlands using distributed temperature sensing (DTS). The forest has an open understory (0–20 m) and a dense overstory (20–34 m). The understory was often colder than the atmosphere above (80 % of the time during the night, >99 % during the day). Based on the aerodynamic Richardson number the canopy was regularly decoupled from the atmosphere (50 % of the time at night). In particular, decoupling could occur when both u*<0.4 m s−1 and the canopy was able to cool down through radiative cooling. With these conditions the understory could become strongly stably stratified at night. At higher values of the friction velocity the canopy was always well mixed. While the understory was nearly always stably stratified, convection just above the forest floor was common. However, this convection was limited in its vertical extent, not rising higher than 5 m at night and 15 m during the day. This points towards the understory layer acting as a kind of mechanical “blocking layer” between the forest floor and overstory. With the DTS temperature profiles we were able to study decoupling and stratification of the canopy in more detail and study processes which otherwise might be missed. These types of measurements can aid in describing the canopy–atmosphere interaction at forest sites and help detect and understand the general drivers of decoupling in forests.

scholarly journals A new method to derive middle atmospheric temperature profiles using a combination of Rayleigh lidar and O<sub>2</sub> airglow temperatures measurements

2012 ◽  
Vol 30 (1) ◽  
pp. 27-32 ◽  
Author(s):  
A. Taori ◽  
A. Jayaraman ◽  
K. Raghunath ◽  
V. Kamalakar
Keyword(s):  
Temperature Profile ◽  
Atmospheric Temperature ◽  
New Method ◽  
Temperature Profiles ◽  
Vertical Temperature ◽  
Lidar System ◽  
Mesospheric Temperature ◽  
Simultaneous Measurements ◽  
Rayleigh Lidar ◽  
First Time

Abstract. The vertical temperature profiles in a typical Rayleigh lidar system depends on the backscatter photon counts and the CIRA-86 model inputs. For the first time, we show that, by making simultaneous measurements of Rayleigh lidar and upper mesospheric O2 temperatures, the lidar capability can be enhanced to obtain mesospheric temperature profile up to about 95 km altitudes. The obtained results are compared with instantaneous space-borne SABER measurements for a validation.

scholarly journals Temperature profiles measurements in turbulent Rayleigh-Bénard convection by optical fibre system at the Barrel of II-menau

2018 ◽  
Vol 180 ◽  
pp. 02020
Author(s):  
Jakub Drahotský ◽  
Pavel Hanzelka ◽  
Věra Musilová ◽  
Michal Macek ◽  
Ronald du Puits ◽  
...  
Keyword(s):  
Turbulent Flows ◽  
Optical Fibre ◽  
Large Scale ◽  
Temperature Profiles ◽  
Vertical Temperature ◽  
Thin Glass ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

Modelling of large-scale natural (thermally-generated) turbulent flows (such as the turbulent convection in Earth’s atmosphere, oceans, or Sun) is approached in laboratory experiments in the simplified model system called the Rayleigh-Bénard convection (RBC). We present preliminary measurements of vertical temperature profiles in the cell with the height of 4:7 m, 7:15m in diameter, obtained at the Barrel of Ilmenau (BOI), the worldwide largest experimental setup to study highly turbulent RBC, newly equipped with the Luna ODiSI-B optical fibre system. In our configuration, the system permits to measure the temperature with a high spatial resolution of 5mm along a very thin glass optical fibre with the length of 5m and seems to be perfectly suited for measurement of time series of instantaneous vertical temperature profiles. The system was supplemented with the two Pt100 vertically movable probes specially designed by us for reference temperature profiles measurements.

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