An Investigation of Thermal Stratification in Horizontal Storage Tanks

1981 ◽  
Vol 103 (4) ◽  
pp. 286-290 ◽  
Author(s):  
M. F. Young ◽  
J. W. Baughn
Keyword(s):  
Thermal Stratification ◽  
Present Model ◽  
Temperature Gradients ◽  
Measured Temperature ◽  
Vertical Temperature ◽  
Makeup Water ◽  
One Dimensional ◽  
Test Conditions ◽  
Axial Temperature ◽  
Horizontal Tank

The thermal behavior of a horizontal storage tank has been investigated numerically and experimentally. The purpose of the present work is to compare a simple, one-dimensional model to the measured temperature stratification in this horizontal tank. For the test conditions used in these experiments, axial temperature gradients were found to be negligible compared to vertical temperature gradients. It was observed that significant mixing of the tank occurred when water was removed unless a diffuser manifold was placed on the makeup water inlet. The numerical model used was one-dimensional (vertical) with some degree of mixing at the inlet and outlet boundaries. The temperatures at the top of the tank were predicted fairly well, but the temperatures at the bottom deviated somewhat from the predictions. It appears that some additional interior mixing, not included in the present model, occurs.

Temperature and Moisture Distributions in a Clay Buffer Material Due to Thermal Gradients

1992 ◽  
Vol 294 ◽  
Author(s):  
A.M.O. Mohamed ◽  
R.N. Yong ◽  
B. Kjartanson
Keyword(s):  
Temperature Gradients ◽  
Thermal Gradients ◽  
Measured Temperature ◽  
Moisture Movement ◽  
Equilibrium Time ◽  
One Dimensional ◽  
Diffusion Parameters ◽  
Buffer Material ◽  
Heat And Moisture ◽  
Moisture Profiles

ABSTRACTSeveral series of one-dimensional tests were used to investigate the nature of transient heat and moisture movements in a clay buffer under different imposed temperature gradients. The measured temperature and moisture profiles were used to calculate the diffusion parameters governing heat and moisture movement in the buffer material. The diffusion parameters are shown to depend on the moisture content, temperature and moisture equilibrium time.

scholarly journals Stratification and equalization cycles in shallow maturation ponds with different operational configurations and at different periods of the year

2019 ◽  
Vol 14 (3) ◽  
pp. 682-694 ◽  
Author(s):  
Ricardo Gomes Passos ◽  
Daniel F. C. Dias ◽  
Valéria A. J. Rodrigues ◽  
Marcos von Sperling
Keyword(s):  
Thermal Gradient ◽  
Vertical Profile ◽  
Thermal Stratification ◽  
Significant Positive Correlation ◽  
Statistical Tests ◽  
Vertical Mixing ◽  
Temperature Gradients ◽  
Vertical Temperature ◽  
In Series ◽  
Temperature Equalization

Abstract This study aimed at evaluating the occurrence of stratification/equalization cycles in two full-scale shallow maturation ponds in Brazil, with different operational configurations and different periods of the year, through monitoring of temperature and other constituents in the vertical profile of the ponds. The study comprised two operational phases: one phase in which both ponds had no baffles and operated in parallel (one pond had sludge accumulated on the bottom while the other did not); and another phase in which the ponds operated in series, the first pond without baffles and with accumulated sludge on the bottom while the second pond had two longitudinal baffles, a shallower depth and no accumulated sludge. Overall, there were systematic daily periodic events of thermal stratification followed by temperature equalization and vertical mixing in both ponds and operating phases. Vertical temperature gradients were predominantly in the 0–7 °C m−1 range. Statistical tests showed a significant positive correlation between the thermal gradient in the pond and air temperature, but not between the thermal gradient and wind speed. Data suggested that ponds remained 56% of the time under thermal stratification and 44% in vertical mixing. The data also highlighted the importance of sludge in the thermal balance of ponds.

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

2020 ◽  
Author(s):  
Bart Schilperoort ◽  
Miriam Coenders-Gerrits ◽  
César Jiménez Rodríguez ◽  
Christiaan van der Tol ◽  
Bas van de Wiel ◽  
...  
Keyword(s):  
Thermal Stratification ◽  
Friction Velocity ◽  
Douglas Fir ◽  
Temperature Gradients ◽  
Temperature Profiles ◽  
Distributed Temperature Sensing ◽  
Vertical Temperature ◽  
Vertical Exchange ◽  
Flux Measurements ◽  
The Relationship

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), and was regularly decoupled from the atmosphere (50 % of the time at night). The relationship between the temperature gradients and the friction velocity (u*) showed a clear threshold between coupling regimes. In particular, decoupling occurred when u* 

scholarly journals Rolls of the internal gravity waves in the Earth's atmosphere

2014 ◽  
Vol 32 (2) ◽  
pp. 181-186 ◽  
Author(s):  
O. Onishchenko ◽  
O. Pokhotelov ◽  
W. Horton ◽  
A. Smolyakov ◽  
T. Kaladze ◽  
...  
Keyword(s):  
Nonlinear Dynamics ◽  
Gravity Waves ◽  
Closed System ◽  
Wind Shear ◽  
Internal Gravity Waves ◽  
Temperature Gradients ◽  
System Of Equations ◽  
Vertical Temperature ◽  
Earth’S Atmosphere ◽  
Earth's Atmosphere

Abstract. The effect of the wind shear on the roll structures of nonlinear internal gravity waves (IGWs) in the Earth's atmosphere with the finite vertical temperature gradients is investigated. A closed system of equations is derived for the nonlinear dynamics of the IGWs in the presence of temperature gradients and sheared wind. The solution in the form of rolls has been obtained. The new condition for the existence of such structures was found by taking into account the roll spatial scale, the horizontal speed and wind shear parameters. We have shown that the roll structures can exist in a dynamically unstable atmosphere.

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.

A Numerical Model of In-Channel Pebble Bed Thermal Storage for a Solar Chimney

2012 ◽  
Author(s):  
Brandon Schulte ◽  
O. A. Plumb
Keyword(s):  
Numerical Model ◽  
Present Model ◽  
Thermal Storage ◽  
Implicit Time ◽  
Heat Transfer Characteristics ◽  
Solar Chimney ◽  
Pebble Bed ◽  
One Dimensional ◽  
Time Stepping ◽  
Daily Energy

In this study, solar chimney performance is numerically modeled. Previously published models have considered water bags and natural earth as means to store daytime thermal energy for nighttime operation of the system. The present model considers in-channel pebble bed thermal storage. A one-dimensional, implicit time stepping numerical model is developed to predict solar chimney performance throughout a 24 hour period. The model is partially verified with available experimental data. The daily energy, daily efficiency and heat transfer characteristics of the solar chimney with pebble bed thermal storage are summarized. The numerical simulation showed that by introducing a pebble bed, nightly exit velocities reach 40% of the peak daytime velocity. However, the daily kinetic energy delivered by a solar chimney with pebble bed thermal storage is much less than a traditional solar chimney, suggesting pebble bed thermal storage is more practicable in building heating applications as opposed to power generation.

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>

The Thermal Regime of South Bay, Manitoulin Island

1967 ◽  
Vol 24 (1) ◽  
pp. 101-125 ◽  
Author(s):  
A. M. McCombie
Keyword(s):  
Thermal Regime ◽  
Thermal Stratification ◽  
Yellow Perch ◽  
Lake Trout ◽  
Smallmouth Bass ◽  
Lake Huron ◽  
Vertical Temperature ◽  
Class Strength ◽  
Influence Of Temperature On ◽  
History Of

The thermal regime of South Bay is described from records collected from 1953 to 1962 with thermometers, thermographs, and bathythermographs, the last being cast at 11 stations along the bay and one in Lake Huron. Warming begins in April and thermal stratification is established in June. Shallow areas warm more rapidly than deep in the spring and cool more quickly in autumn. The boundary between the epilimnion and the thermocline becomes sharper as summer advances but the transition from thermocline to hypolimnion remains gradual. The average seasonal trend of surface temperatures is a sine function with a maximum of 66 F in mid August and a minimum of 34 F in late March, though values outside this range occur frequently. At 180 ft the maximum of 47 F is attained in November. At the lake and outermost bay stations there is a temperature slump in June and July which may be due to an upwelling in the lake. Evidence of an exchange of water between the lake and bay is seen in vertical temperature sections and water movements Variations in epilimnial temperatures are correlated with those of the air temperature, but variations in epilimnial and hypolimnial temperatures appear to be unrelated. Finally, literature describing the influence of temperature on the year class strength of smallmouth bass, the distribution of lake trout, the growth of yellow perch, and the life history of Pontoporeia in South Bay is reviewed.

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