scholarly journals A Numerical Model to Estimate the Soil Thermal Conductivity Using Field Experimental Data

2019 ◽  
Vol 9 (22) ◽  
pp. 4799 ◽  
Author(s):  
Leugim Corteze Romio ◽  
Débora Regina Roberti ◽  
Lidiane Buligon ◽  
Tamires Zimmer ◽  
Gervásio Annes Degrazia
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Numerical Model ◽  
Soil Temperature ◽  
Field Experiments ◽  
Soil Heat Flux ◽  
Soil Thermal Conductivity ◽  
Empirical Parameter ◽  
Soil Temperature Gradient

Soil thermal conductivity is an important parameter for understanding soil heat transfer. It is difficult to measure in situ with available instruments. This work aims to propose a numerical model to estimate the thermal conductivity from the experimental measurements of soil heat flux and soil temperature. The new numerical model is based on the Fourier Law adding a constant empirical parameter to minimize the uncertainties contained in the data from field experiments. Numerically, the soil thermal conductivity is obtained by experimental linear data fitting by the Least Squares Method (LSM). This method avoids numerical indetermination when the soil temperature gradient or soil heat flux is very close to zero. The new model is tested against the different numerical methodology to estimate the soil heat flux and validated with field experimental data. The results indicate that the proposed model represents the experimental data satisfactorily. In addition, we show the influence of the different methodologies on evaluating the dependence of the thermal conductivity on the soil water content.

scholarly journals Sub-soil temperature variation and estimation of soil heat flux at Pune

MAUSAM ◽  
2021 ◽  
Vol 42 (4) ◽  
pp. 357-360
Author(s):  
A. CHOWDHURY ◽  
H. P. DAS ◽  
A. D. PUJARI
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Soil Temperature ◽  
Temperature Variation ◽  
Heat Balance ◽  
Thermal Wave ◽  
Heat Storage ◽  
Soil Heat Flux ◽  
Temperature Ranges ◽  
Maximum Minimum

Utilising experimental data from 23 November to 8.December 1989. temperature and heat storage variations at Pune have been studied, based on 3 hourly observations.. pattern of penetration of .thermal wave within the soil has been examined and time of occurrence of maximum/minimum temperatures discussed for various depths. Temperature ranges in different layers have been theoretically computed and compared with those based on actual observations. Heat balance at various depths has also been presented and discussed.

scholarly journals The Ability of a Soil Temperature Gradient-Based Methodology to Detect Leaks from Pipelines in Buried District Heating Channels

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5712
Author(s):  
Matjaž Perpar ◽  
Zlatko Rek
Keyword(s):  
Thermal Conductivity ◽  
Temperature Gradient ◽  
Soil Temperature ◽  
District Heating ◽  
Leak Detection ◽  
Operating Conditions ◽  
Channel Cross Section ◽  
Soil Thermal Conductivity ◽  
Soil Temperature Gradient ◽  
Gradient Based

We carried out several numerical experiments to analyze how different boundary conditions affect the ability to detect small pipeline leaks. Our method is based on determining the soil temperature gradient above a buried district heating channel. The equivalent thermal conductivity of a wet insulation (λeq) value of 0.5 W/(m·K) was used to mimic a small water leakage. To evaluate the heat loss through the channel cross section, the heat conduction model was used for the pipe insulation, the concrete, and the soil, while the convection model was considered within the channel. The following effects were used to simulate different operating conditions: heat convection at the soil surface, leakage only from the supply or return pipe, soil height above the channel, soil thermal conductivity, and pipe diameter. With the exception of leakage only from the return pipe and low soil thermal conductivity 0.4 W/(m·K), the results showed a doubling of the soil temperature gradient when compared with the no-leakage case. This fact undoubtedly confirms the potential of the method, which is particularly suitable for leak detection in old pipelines that have priority for renovation. A key added value of this research is that the soil temperature gradient-based leak detection technique was found useful in most foreseeable DH operating situations.

The effect of soil temperature and soil water content on thermal properties in an artificial forestland and a natural regrowth grassland

2020 ◽  
Author(s):  
Tangtang Zhang ◽  
Xin Ma
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Soil Temperature ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Condition ◽  
Soil Thermal Conductivity ◽  
Soil Thermal Properties ◽  
Increasing Temperature

<p>Soil temperature, soil water content and soil thermal properties were measured in an artificial forestland and a natural regrowth grassland from November in 2017 to July in 2019. The results show that the effects of soil temperature and soil water content on thermal properties are different in different soil condition. Soil thermal conductivity (K) and soil volumetric heat capacity (C) increase with increasing temperature in unfrozen period, but soil diffusivity (D) has no significant dynamic cycle and it almost keeps a constant level in a certain time. Soil thermal conductivity (K) decreases with increasing temperature during soil frozen period. The C and K increase with increasing soil water content in unfrozen period, while the D decrease with increasing soil water content.</p>

Correlation of Theoretical Analysis With Experimental Data on The Performance of Charring Ablators

1976 ◽  
Vol 98 (1) ◽  
pp. 139-143 ◽  
Author(s):  
K. Mastanaiah
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Theoretical Analysis ◽  
Experimental System ◽  
Wall Heat Flux ◽  
System Response ◽  
Exponential Dependence ◽  
Cold Wall ◽  
Static Test

Experimental data are obtained for surface recession, char depth, and temperatures in silica phenolic and carbon phenolic ablators from static test conducted on rocket nozzles. In an attempt to correlate the theoretical analysis with the experimental observations, it is found that the effective thermal conductivity of char is strongly dependent on the wall heat flux. An hypothesis is postulated that the char conductivity can best be correlated by cold wall heat flux treated as a generalized variable that includes the effects of other factors like temperature and chemical composition of the char. Exponential dependence of char conductivity on the cold wall heat flux is observed for both the ablators, and has offered excellent comparison between the theoretical and the experimental system response.

Effect of Soil Moisture on Soil Temperature Field Near Buried Pipe

2012 ◽  
Vol 204-208 ◽  
pp. 650-653
Author(s):  
Jiang Li ◽  
Jun Ping Fu ◽  
Wu Gang Xie
Keyword(s):  
Thermal Conductivity ◽  
Temperature Field ◽  
Soil Moisture ◽  
Heat Exchanger ◽  
Moisture Content ◽  
Field Experiment ◽  
Soil Temperature ◽  
Soil Moisture Content ◽  
Thermal Conductivity Coefficient ◽  
Soil Thermal Conductivity

System effectiveness and useful life of heat pump are directly affected by whether the design of ground heat exchanger is reasonable or not. The efficiency of heat exchanger has a close relationship with soil thermal conductivity coefficient and heat diffusivity, while soil moisture content affects soil thermal conductivity coefficient and soil temperature field. In this paper, we perform numerical simulation on CFD software. Then we study the soil temperature changes through field experiment in different soil moisture content on field experiment and finally obtained the relationships of the moisture content with the single U ground soil temperature field.

scholarly journals Fluxo de calor no solo modelado a partir de dados de temperatura em dois níveis de profundidade em uma floresta tropical na Amazônia Ocidental

2018 ◽  
Vol 40 ◽  
pp. 138
Author(s):  
Antônio Vinicius do Prado Rodrigues ◽  
Nelma Tavares Dias Soares ◽  
Renata Gonçalves Aguiar ◽  
Alberto Dresch Webler ◽  
Bruno Soares de Castro
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Soil Temperature ◽  
Tropical Forest ◽  
Large Scale ◽  
Energy Exchange ◽  
Global Climate ◽  
Soil Heat Flux ◽  
Measured Data ◽  
Biological Reserve

The global climate is dependent of ecological balance of forests, especially tropical. The heat flux in the soil is an important factor in studies of energy balance representing the main form of energy exchange between soil and atmosphere. The aim of the present work was to estimate soil heat flux using soil temperature measurements at two depth levels in a tropical forest in the Western Amazon, in order to obtain coherent data for both the use of the values and for the filling of failures in database. Had been used data on temperature and soil heat flux collected in a micrometeorological tower belonging to the towers network of the Large Scale Biosphere-Atmosphere Program in the Amazon, located in the Jaru Biological Reserve. The estimated data presented 94% agreement with the measured data, the two have similar behaviors that allow the use in filling of failures in a demonstrative way. However, there is a delay in the estimated values of the heat flux in the soil in relation to the measured one, which interferes in the result of the model, provoking more studies to improve it.

scholarly journals Nova abordagem para a estimativa do fluxo de calor no solo para o Bioma Pampa

2018 ◽  
Vol 40 ◽  
pp. 76
Author(s):  
Leugim Corteze Romio ◽  
Tamíres Zimmer ◽  
Débora Regina Roberti ◽  
Lidiane Buligon
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Surface Energy Balance ◽  
Soil Heat Flux ◽  
Modeling Error ◽  
Experimental Site ◽  
Coefficient Of Thermal Conductivity ◽  
Fourier Heat Conduction ◽  
The City ◽  
Modified Equation

The study of the thermal properties of the soil and the variables dependent on these properties is very important for the understanding of the surface energy balance. Among the main variables, there is the soil heat flux, especially because it allows the verification of the influences that occur in the biome of a region as temperature variation occurs. This work intend to estimate the coefficient of thermal conductivity and, thus, to obtain the values for the soil heat flux. The data used to estimate the parameters were obtained from an experimental site located in the city of Pedras Altas-RS. Two equations were used, the first one defined by the Fourier Heat Conduction Law (discretized) and the second one a modification of the first one including a k coefficient, named “modeling error”. Based on the results obtained it can be verified that the modified equation presented better results, when compared with the classical solution.

Numerical determination of pressure-dependent effective thermal conductivity in Berea sandstone

2021 ◽  
Author(s):  
Mirko Siegert ◽  
Marcel Gurris ◽  
Erik Hans Saenger
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Numerical Model ◽  
Effective Thermal Conductivity ◽  
Rock Sample ◽  
Rock Physics ◽  
Contact Phase ◽  
Data Set ◽  
Computed Tomography Images ◽  
Thermal Conductivities

<p>Within the scope of the present work, the pressure-dependent effective thermal conductivity of rock samples is simulated. Our workflow can be assigned to the field of digital rock physics. In a first step, a 3D micro-CT scan of a rock sample is taken. Subsequently, the resulting greyscale images are analysed and segmented depending on the occurring phases. Based on this data set, a computational mesh is created and the corresponding thermal conductivities are assigned to each phase. Finally the numerical simulations can be carried out.<br>For the representation of the pressure dependency we use the approach proposed by Saenger [1]. By making use of the watershed algorithm, boundaries between the individual grains of the rock sample are detected and assigned to an artificial contact phase. In the course of several simulations, the thermal conductivity of the contact phase is continuously increased. Starting with the thermal conductivity of the pore phase and ending with the thermal conductivity of the grain phase. A linear correlation is used to match the thermal conductivity of the contact phase with the pressure of a given experimental data set. This enables a direct comparison between simulation and measurement.<br>In a further step, the numerical model is calibrated to optimise the agreement between experimental data and simulation results. In particular, starting from two calibration points of the experimental data set, an adjustment of the thermal conductivities in the numerical model is carried out. While the thermal conductivity of the pore phase is held constant during the whole calibration process, thermal conductivities of the grain and contact phase are adjusted.</p><p>References<br>[1] Saenger et al. 2016. Analysis of high-resolution X-ray computed tomography images of Bentheim sandstone under elevated confining pressures. Geophysical Prospecting, 64(4), 848–859.</p><p> </p>

Sign in / Sign up

Export Citation Format

Share Document