Thermophysical Properties Of Soil Research Articles

Estimating the impact of the thermo-physical properties of the multilayer soil on earth-air heat exchanger system performance

This study developed a new method for experimentally measuring and estimating multilayer soil thermo-physical properties. It also tested how multi-layered soil influences an earth-air heat exchanger (EAHE) system in Gödöllő, Hungary. Thus, this research has introduced these combination characteristics that increase EAHE system performance by properly estimating soil multi-layer properties and thermal gradients and their thermal performance effects. New laboratory and theoretical methods can evaluate multilayer soil thermal and physical properties depending on moisture content and density. The first layer had the lowest soil moisture content (6.10 %), the fifth layer had the highest (12.8 %), and the mixed layer had the middle value (9.12 %). The densities of these soil types ranged from 930.49 to 1184.03 kg/m3. When installing the EAHE system, the second layer is better for cooling purposes. Third-layer soil pipe air is 3.74 % hotter than second-layer air. Mixed soil heats and cools moderately. It is 1.74 % hotter and 2 % colder than the second and third layers of soil, respectively.

Numerical simulation of temperature field around buried pipes of ground source heat pumps based on mathematical models

The author established a physical and mathematical model for the heat exchange of a ground source heat pump buried heat exchanger under the co-operation of heat and seepage, including the soil and fluid inside the pipe surrounding the heat exchanger. Using ANSYS finite element APDL language for programming, based on the line heat source model, simulate the temperature field around the vertical double U-tube underground heat exchanger, the effects of soil thermophysical properties, temperature outside the pipe, soil type and backfill material on soil temperature field were obtained through simulation analysis. The experimental results indicate that, the changes in soil temperature are also significant with different backfill materials. Therefore, it is necessary to conduct serious research and optimization on backfill materials, develop new types of backfill materials, improve backfill construction techniques, and conduct in-depth research by combining theoretical analysis with practical engineering to ultimately find efficient and economical backfill materials. The change in equivalent pipe diameter has little effect on soil temperature, and the linear heat source model is used for calculation without causing significant errors. It has been proven that the soil itself has strong resilience and has reference value for the design of buried heat exchangers in practical engineering.

Experimental analysis on thermophysical properties of clay found in geographical areas of India and their ability to cool water for semi-arid climate regions

The Thermo physical behaviour of soil is the fundamental behaviour and plays significant position in its “utilization” as “electrical and heat insulation”. However, numerous “researchers have studied” thermo-physical properties of soil. Still, the study on the relationship between soil's properties and its cooling effect through evaporation has not been investigated in detail. In this analysis, soil samples and earthen pots were collected from four states of India: Haryana, Delhi, Rajasthan, and Uttar Pradesh. The performance parameters used to evaluate the cooling effect of the soil, and earthen pot samples are “water-holding capacity”, porosity, “thermal-conductivity”, texture, and particle and bulk density. The application of “high temperature” fluctuate the “internal microstructure” of clay/soil and subsequently disturbs its “physical and thermal properties”. The sand/clay is converted into an earthen pot by applying high temperatures in kilns. The pot samples collected are heated in kilns to bring them to the final form for the study. We are studying the properties after that treatment. In this paper, the impact of “firing temperature” (maximum 900°C) on the “thermo-physical properties” of earthen pots made up of soil of a similar kind as the soil samples collected and the impact of thermo-physical properties on the cooling of the earthen pots has been examined via experiments. The results specify that the “thermal conductivity” of soil/clay samples is less compared to earthen pot. The “porosity and water-holding capacity” of the soil are greater than earthen pots because pore space or pore volume has decreased due to the heating effect. From the experimental analysis, it was found that the soil of the Sohna location in Haryana state has a high water cooling capacity due to its high water-holding (49.28%) capacity and porosity (48.75%). The pot made out of clay, having higher porosity, and water-holding capacity, gives the maximum cooling temperature.

Analysis of the method for estimation of the lunar soil thermophysical properties under solar radiation heating

Представлен анализ способа определения теплофизических характеристик лунного грунта проникающим зондом при использовании в качестве нагревателя солнечного тепла. В качестве прототипа использовался зонд, применявшийся в миссиях «Аполлон».

Effect of Wheat Straw Biochar on Thermophysical Properties of Loessial Soil

Soil thermophysical properties are the key factors affecting the internal heat balance of soil. In this paper, biochars (BC300, BC500 and BC700) were produced with wheat straw at the temperatures of 300, 500 and 700°, respectively. The effects of biochar amendment at the rates of 0%, 1%, 3%, and 5% on the thermophysical properties (thermal conductivity, heat capacity, and thermal diffusivity) of a loessial soil were investigated with and without water content respectively. Although the bulk density of soil significantly decreased with biochar amendment, due to enhancing soil porosity and organic matter content, the thermophysical properties of soil did not change largely with biochar amendment rate and pyrolysis temperature. Water content exhibited significant effects on the thermophysical properties of soils added with biochars, where the thermal conductivity and heat capacity of soil were linearly proportional to water content, the thermal diffusivity initially increased and then decreased with the increase of water content. In the meanwhile, there was no significant correlation between the biochar amendment rate or pyrolysis temperature and thermophysical properties. The results show that water content should be mainly concerned as a factor when the internal heat balance of loess soil is evaluated, even though the soil is amended with biochar.

Influence of soil thermophysical properties on the flow of thermal energy taken by the energy pile

The depletion of traditional fossil energy sources leads to an increasing development of non-traditional energy sources. One of the promising directions of alternative energy is the use of low-potential energy of the soil for heating buildings and structures for various purposes. Heat extraction is possible through the use of energy foundation. However, their rational design is impossible without a careful assessment of a large number of factors that affect the potential value of thermal energy extracted from the soil. The purpose of this work was to build a whole methodology to assess the degree of influence of soil thermophysical properties, in particular, such as heat capacity and thermal conductivity, on the amount of heat energy selected energy pile. The formulation and analysis of the numerical experiment to identify the desired dependencies. The matrix of experiment planning is made. The numerical simulation of the energy pile of different geometric parameters in different soil conditions is performed. Statistical processing of the obtained experimental data was carried out. A quadratic regression equation was developed to determine the amount of heat through the side surface of the pile depending on the length of the pile, its diameter, heat capacity and thermal conductivity of the soil. The analysis of this equation for the purpose of estimation of degree of influence of initial thermophysical parameters of soil on value of thermal energy of the selected pile is carried out.

Modifications to the conventional design methods for borehole heat exchangers based on a novel response factor model

For ground source heat pumps with boreholes, the rule-of-thumb and thermal performance test (TPT) methods are commonly adopted for borehole design but suffer from inaccuracy. The response factor model can calculate the time-varying soil heat transfer of boreholes fast and accurately. Based on the response factor model, the characteristic diagrams of borehole heat transfer are summarized to show the influential laws of different factors (borehole inlet temperature, velocity of fluid inside the pipe, initial soil temperature, soil thermophysical properties, and operation time). The characteristic diagrams can be used as a new design method that improves the accuracy of the rule-of-thumb method by considering different influential factors and avoiding the subjective errors of designers. For different soils, the borehole design errors of the new diagram method are −5% to 10%, which are much less than the errors (−15% to 72%) of the conventional rule-of-thumb method. In addition, a modification to the TPT method is also proposed using the response factor model. The borehole design errors of the conventional TPT method (48 h testing) can be reduced by 13%–20% using the derived correction factors. The proposed modification methods contribute to more reasonable borehole design, improved heating reliability as well as increased energy efficiency.

Features of soil thermophysical properties of the southern variant of ravine biogeocenoses of the Ukrainian steppe zone

Thermophysical properties are an important characteristic of the general condition of soils, which determine the peculiarities of the distribution of heat flow in them. Today studies of thermophysical properties of soils, including the steppe zone of Ukraine, are practically not performed. This determines the relevance of the work, which is devoted to establishing the characteristics of the thermal properties of various soils. As a result of the study of thermal diffusivity, heat capacity and thermal conductivity of soils of northern and southern exposures, as well as the thalweg of the Voyskovoy Bayrak (located near the village of Voyskovoe Solonyansky district of Dnipropetrovsk region), it was found that the most important soil factors particles of physical clay and organic matter content. It was found that the eluvial horizons of the chernozem of the forest of the northern exposure differ in the reduced values ​​of heat capacity and thermal conductivity in comparison with the illuvial horizons. Eluvial horizons of forest-meadow soil of thalweg are characterized by increased values ​​of thermal diffusivity and thermal conductivity, as well as reduced values ​​of heat capacity compared to illuvial horizons. Eluvial horizons of forest chernozem of southern exposure are characterized by lower values ​​of thermal diffusivity, heat capacity and thermal conductivity compared to illuvial horizons. The most significant boundary between eluvial and illuvial horizons in terms of thermophysical properties is characteristic of the chernozem of forest southern exposure, which is manifested in a sharp increase in the values ​​of thermophysical properties in the first illuvial horizon. Cluster analysis revealed that the most similar in terms of thermal diffusivity are forest chernozems of southern and northern exposures, and in terms of heat capacity and thermal conductivity – forest chernozems of northern exposure and forest-meadow soil of thalweg ravine.

Study on the Thermophysical Properties of Clay Under Repeated Freezing and Thawing

The thermophysical properties of soil are crucial factors for understanding the heat distribution in soil layers, especially in cold regions. Therefore, to analyze the effect of freezing and thawing action on soil thermophysical properties, here, samples with varying water content were subjected to different numbers of freezing and thawing cycles from 0 to 11 in a laboratory setting, and the thermal conductivity, thermal diffusion coefficient and volume heat capacity were measured and analyzed. Five previously proposed thermal conductivity models were evaluated, and a novel thermal conductivity model was developed based on the concept of the tortuosity and parallel model. The results showed that the thermal conductivity and volume heat capacity vary in direct proportion with the number of freezing and thawing cycles up to seven cycles. Beyond seven cycles, with repeated freezing and thawing action, samples with varying water content reach a residual porosity ratio of 0.5142–0.5345. Both the water content and freezing and thawing action influence the soil thermophysical properties, with water content playing a more important role than freeze–thaw cycles. Among these five models, the Kersten model was found to be the best, followed by the Johansen model, Lu et al. model, parallel model, and serial model. respectively. The Cote and Konrad model demonstrated the poorest performance. In addition, the tortuosity–parallel model was able to efficiently calculate the thermal conductivity of clay under freezing and thawing action.

Influence of an improved surrounding soil on the energy performance and the design length of earth-air heat exchanger

European directive 31/2010/EU imposes a reduction of primary energy consumption in the building sector. An Earth-air heat exchanger (EAHE) is a renewable energy system that can respond in part to this problem. This system uses soil temperature to cool or heat ventilated air for a building. However, the design of the EAHE depends on thermo-physical characteristics of the surrounding soil. A numerical study is carried out to investigate the energy performance and the design length under influence on an improved surrounding soil. Six EAHE configurations, of three different lengths (20 m, 40 m and 60 m) and two different types of surrounding soils, are simulated: the standard soil used (fine sand, sand) and an improved surrounding soil (a mix between fine sand and 3% of bentonite, named bent-sand). Weather conditions and soil thermo-physical properties used in the simulations are derived from the measurements recorded in an experimental EAHE. The results show that the addition of bentonite in the sand surrounding soil improves the EAHE’s energy performance and that the design length of an EAHE can be reduced for a defined power.

Experimental Investigation of Thermo-Physical Properties of Soil Using Solarisation Technology

Soil Thermo-Physical Properties (TPP) depend on heat transfer in the soil. This paper presents a study on different soil solarisation technologies influenced by soil TPP. This study evaluates three factors: The tillage depth for soil at three levels (15, 25 and 45 cm), the number of plastic film at three levels (single, double and without plastic film) and three cases of fertilizers (chemical fertilizer, organic fertilizer and without fertilizer). The parameters explored in this study include soil bulk density (Mg/cm3), soil porosity (%), soil volumetric moisture content (cm3/cm3) and soil thermal diffusivity (m2/sec). Data management and analysis were performed using SAS 9.1 statistical software and the spilt-plot under Randomized Complete Block Design (RCBD). The results show that soil Tillage Depth (TD) strongly influences TPP, as well as a significant effect on soil bulk density (ρb), porosity (Φ), volumetric moisture content (θ) and thermal diffusivity (D). The results also reveal that a tillage depth of 15 cm produces lower values of ρb, θ and D (1.25 Mg/cm3, 0.131 cm3/cm3 and 1.24×10-6 m2/sec, respectively) and a higher value of Φ (52.78%). In addition, the finding indicates that ρb is increased by increasing TD. There was a significant positive correlation between the number of plastic film and parameters studied. The soil double plastic film produced lower values of ρb and D for soil (1.253 Mg/cm3, 7.76×10-7m2/sec). However, it recorded higher values for Φ and θ for soil (52.70% and 0.231 cm3/cm3, respectively). Furthermore, the current study shows significant differences between the types of fertilizers on ρb. Organic Fertilizer (OF) obtained a lower value of ρb (1.2 Mg/m3), compared with chemical fertilizer and without fertilizer (1.28 and 1.31 Mg/m3, respectively). In contrast, contrary to expectations, this study did not find significant differences between the types of fertilizer on D and θ for soil. A positive correlation was found in the interaction between the studied factors in the parameters. Furthermore, D increased with increasing soil bulk density (pb) and tillage depth.

Lunar phase function at 1064 nm from Lunar Orbiter Laser Altimeter passive and active radiometry

We present initial calibration and results of passive radiometry collected by the Lunar Orbiter Laser Altimeter onboard the Lunar Reconnaissance Orbiter over the course of 12 months. After correcting for time- and temperature-dependent dark noise and detector responsivity variations, the LOLA passive radiometry measurements are brought onto the absolute radiance scale of the SELENE Spectral Profiler. The resulting photometric precision is estimated to be ∼5%. We leverage the unique ability of LOLA to measure normal albedo to explore the 1064 nm phase function’s dependence on various geologic parameters. On a global scale, we find that iron abundance and optical maturity (quantified by FeO and OMAT) are the dominant controlling parameters. Titanium abundance (TiO2), surface roughness on decimeter to decameter scales, and soil thermophysical properties have a smaller effect, but the latter two are correlated with OMAT, indicating that exposure age is the driving force behind their effects in a globally-averaged sense. The phase function also exhibits a dependence on surface slope at ∼300 m baselines, possibly the result of mass wasting exposing immature material and/or less space weathering due to reduced sky visibility. Modeling the photometric function in the Hapke framework, we find that, relative to the highlands, the maria exhibit decreased backscattering, a smaller opposition effect (OE) width, and a smaller OE amplitude. Immature highlands regolith has a higher backscattering fraction and a larger OE width compared to mature highlands regolith. Within the maria, the backscattering fraction and OE width show little dependence on TiO2 and OMAT. Variations in the phase function shape at large phase angles are observed in and around the Copernican-aged Jackson crater, including its dark halo, a putative impact melt deposit. Finally, the phase function of the Reiner Gamma Formation behaves more optically immature than is typical for its composition and OMAT, suggesting the visible-to-near-infrared spectrum and phase function respond differently to the unusual regolith evolution and properties at this location.

H133 熱応答試験による土壌熱物性評価(一般講演(5))

H133 熱応答試験による土壌熱物性評価(一般講演(5))

Effect of a controlled burn on the thermophysical properties of a dry soil using a new model of soil heat flow and a new high temperature heat flux sensor

Some fires can be beneficial to soils but, if a fire is sufficiently intense, soil can be irreversible altered. We measured soil temperatures and heat fluxes at several soil depths before, during, and after a controlled surface burn at Manitou Experimental Forest (southern Colorado, USA) to evaluate its effects on the soil’s thermophysical properties (thermal conductivity and volumetric specific heat capacity). During the burn the soil was heated to over 400°C at a depth of 0.02 m and to almost 100°C at 0.30 m. Relatively high temperatures persisted for several hours to days even over 1 m deep into the soil. At these intensities and durations significant changes in soil chemistry, structure, and nutrient cycling are likely. However, soil thermophysical properties, estimated before and after the fire with a new model of periodic heat flow in soils, were not significantly changed between the times shortly after sensor installation (October 2001) and 1 month after the fire (February 2002). Estimates of the soil thermophysical properties derived with the new model underestimate laboratory analyses performed on soil samples obtained after the fire. Also presented in this study are some of the first soil heat flux measurements made during a surface fire. Furthermore, data and analyses of the type discussed in this study should aid modeling studies of the soil thermal pulse associated with fire. The ultimate goal of this experiment was to provide tools to assist land managers in the use of prescribed fire to benefit ecosystems and to reduce the potential for harm by examining how the soil’s physical properties and different fuel amounts, geometries, and loading densities influence soil recovery and forest regeneration after fires.

Recent gullies on Mars and the source of liquid water

Geologic features resembling terrestrial water‐carved gullies imply that liquid water has flowed recently on the surface of Mars and challenge our views of the present‐day low‐temperature environment. We evaluate two possible mechanisms for the formation of liquid water under environmental conditions that we expect to have existed on Mars in its recent past. First, we examine the stability of ground ice in the permafrost and the potential for melting near‐surface ground ice (in the top few meters of soil) by solar heating and subsurface conduction. Second, we examine the potential for melting and refreezing of ice at shallow depths due to geothermal heating. We find that near‐surface ground ice does not reach the melting point of water under a range of conditions of soil thermophysical properties, latitudes, obliquities, and surface slopes. The atmosphere remains too dry for the ground ice to melt, even at high obliquity; instead, ice sublimates before reaching melting temperatures. However, the presence of salts in concentrations of 15–40% can adequately lower the melting point to allow melting to occur. We also find that a combination of a global average geothermal heat flux and a thick, low‐conductivity, unconsolidated regolith raises the depth of the melting isotherm to less than a few hundred meters from the surface. Orbitally induced oscillations in the mean annual surface temperature can cause freezing cycles in a confined aquifer at this depth. Freezing pressures generated are adequate to fracture ice‐cemented ground and allow water to escape to the surface, similar to the formation and evolution of terrestrial pingos in shallow permafrost. Both mechanisms are possible; however, the geothermal mechanism is consistent with the observations of the distribution of gullies, while the salty near‐surface ground ice mechanism is not. Further observational tests that can be performed with existing and future spacecraft are suggested.

Estimation of the soil composition by IR observation of the Earth by satellites

A number of missions are in progress for Earth resources satellites to perform soil diagnosis by observing the bare soil thermal response to the heat input from the surrounding atmosphere. Heat capacity missions (and similar missions) are accomplished by measuring the soil temperature at the times of the satellite passes over the soil site. The models which are usually adopted assume that, for atmospheric conditions periodically changing during the day, the surface temperature time dependence is a function of the soil thermal inertia alone (for a dry soil). The present author has shown elsewhere that a more appropriate, two dimensional finite element modelling of the thermal behaviour of the soil, exhibits a dependence of the surface temperature time evolution on both the thermal conductivity ( k) and on the volume heat capacity ( ϱc) (for no evaporation at the interface). At least two independent temperature measurements are necessary in order to get information about k and ϱc. It is shown that, within the range of values of k and ϱc of the usual soils, temperature measurements taken at two successive satellite passes may yield the necessary information on the soil thermophysical properties. Charts can be constructed which will provide information on k and ϱc when two soil temperatures are measured at proper times.