Methods and Results of Experimental Researches of Thermal Conductivity of Soils (original) (raw)
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Laboratory Techniques to Evaluate Thermal Conductivity for Some Soils
Heat and Mass Transfer Journal., 2003
The thermal conductivity of two soils was investigated through laboratory studies. These laboratory experiments used the single probe and dual probe methods to measure and compare thermal conductivities. The soils used were classified as sand and loam. Thermal conductivity measured using single probe method ranged from 0.95 to 2.11 for sand and from 0.49 to 0.76 W/m K for loam. Thermal conductivity measured using dual probe method ranged from 0.98 to 2.17 for sand and from 0.51 to 0.78 W/m K for loam. Finally, it was found that sand had higher values of thermal conductivity than loam for all soil conditions studied.
Development of Experimental Setup for Measuring Thermal Conductivity Characteristics of Soil
October 2018
Thermal conductivity displays a key role in design of engineering structures where, thermal stresses resulting from heat and temperatures are of concern. Significant efforts were made to measure the thermal conductivity of different materials. For thermal conductivity characterization of soil samples it is essential to have very flexible set-up. Hence, this paper provides details about indigenously developed experimental setup for thermal conductivity measurement. The design of this newly developed setup is based on the basic principle of steady state heat flow. This experimental setup is designed in order to measure the thermal conductivity of various materials such as soils, rocks, concrete and any type of unbonded and bonded materials. In this paper, initially the theoretical background of the measurement techniques and the principle of heat flow are described, followed by design description and working procedure. The design has been kept very simple, adjustable for varying type ...
Development of correlations for soil thermal conductivity
International Communications in Heat and Mass Transfer, 1992
Soil thermal conductivity is significantly influenced by saturation and dry density. In this paper, a family of empirical correlations are presented which relate soil thermal conductivity to saturation for five soil types, namely, gravel, sand, silt, clay and peat, in both the frozen and unfrozen states. These correlations were developed from a soil thermal conductivity database which was constructed from measured data available in the literature. The effects of dry density are also examined.
A Theoretical Model of the Thermal Conductivity of Idealized Soil
HVAC&R Research, 1995
Accurate prediction of soil thermal conductivity is of prime importance in the numerical simulation of heat transmission through soils. This paper focuses upon empirical and semi-empirical prediction methods for soil thermal conductivity. A family of empirical correlations are presented which relate soil thermal conductivity to saturation for five soil types: gravel, sand, silt, clay, and peat. These correlations are developed from a database of measured data available in the literature. Also, a theoretical model of soil thermal conductivity is developed for granular materials composed of rotund particles in an almost dry state. This theoretical model includes the effects of the micro-structure and the conductivity of the solid phase. It explicitly relates soil thermal conductivity to dry density and agrees well with experimental data. This paper also presents a review and discussion of those factors which affect soil thermal conductivity, previously reported prediction methods, and conductivity measurement techniques.
Thermal conductivity and diffusivity of soil
International Communications in Heat and Mass Transfer, 1990
The thermal conductivity and diffusivity of soil has been experimentally measured using the line heat source transient method. Representative samples of different textures were collected and analyzed from different localities and depths. The effect of temperatures, in the range of -10°C â 35°C and moisture content up to 40% on the conductivity and diffusivity were investigated. The results of this
Thermal Conductivity of Disturbed Soils Under Laboratory Conditions
Transactions of the ASAE, 2000
oil thermal properties are required in many areas of engineering, agronomy, and soil science. In recent years, considerable effort has gone into developing techniques to determine these properties. Predicting the transport of water, heat, and solute in soil would help manage soil and water resources in irrigated agriculture. The propagation of heat in a soil is governed by its thermal characteristics (De Vries 1963). The thermal conductivity of a soil depends on several factors. These factors can be arranged into two broad groups, those which are inherent to the soil itself, and those which can be managed or controlled to a certain extent. Those factors or properties that are inherent to the soil include the mineralogical composition and the organic component of the soil (Wierenga et al., 1969). Factors influencing soil thermal conductivity that can be managed externally include water content and soil management (De Vries, 1952; Wierenga et al., 1969; Yadav and Saxena, 1973). Water content plays a major role in soil thermal conductivity but is the most difficult to manage. Soil management affects conductivity because practices that cause soil compaction will increase bulk density and decrease porosity of a soil. This in turn will have a significant effect on thermal conductivity. The effect of water content on thermal conductivity has received more attention than the effect of salts on thermal conductivity of soil (Riha et al., 1980). Noborio and McInnes (1993) found that apparent soil thermal conductivity decreased with an increase in the salt concentration of the soil solution with concentrations of CaCl 2 , MgCl 2 , NaCl, or Na 2 SO 4 from 0.1 mol kg-1 to solubility limits. On the other hand, Van Rooyen and Winterkorn (1959) found no noticeable effect of salt on thermal conductivity of quartz sand at high solution contents with concentrations of CaCl 2 up to 0.18 mol kg-1 or with NaCl up to 0.34 mol kg-1. Globus and Rozenshtok (1989) concluded that thermal conductivity of quartz sand moistened with 0.25 mol kg-1 solution of the base KOH was lower than that of quartz sand moistened with water. Thermal properties can be determined indirectly by measuring the rise or fall in temperature of the soil (Jackson and Taylor, 1965). De Vries (1952, 1963) developed models that allow estimation of thermal
Study of the thermal conductivity of a clay-based building material
2019
Local soil materials have been extensively used in North Africa in the construction of buildings where thermal comfort is well ensured without having recourse to the installations, neither of heating nor of air conditioning (buildings with the lowest energy consumption). This study deals with the determination of the thermal conductivity of these earthen materials and for achieving this, straw was added in different quantities to a type of soil from an agricultural region of M'Sila in Algeria. The ratio of the mass of the soil to the mass of the straw R is the criterion utilized in this investigation to inquire on the effect of the addition of straw on the thermal properties of the adobe material. Five samples were studied with namely R=20, R=40, R=50, and R=60 and also one without straw for comparison. The samples were obtained by drying in the sun the manageable paste made of soil, straw and water. The estimation of their thermal conductivity was based on the analysis of transient temperature measurements (0 to 180s) performed by placing a heating film between two identical samples of the material to be tested (transient hot wire method). The soil holding straw and the strawless one present a thermal anisotropy as the thermal conductivity measured in the longitudinal direction is higher than that in the transverse one (p<0.05). A reduction of thermal conductivity is observed subsequent to the amount of straw placed in, the latter also having a significant effect on the conductivity direction. Indeed, the thermal conductivity of a clay mass of m kg is diminished by more than 50% in both directions by adding a straw mass of m/20 kg (more straw) while the thermal conductivity of the same mass is reduced by more than 30% in both directions by adding a straw mass of m/60 (less straw). It was found that an addition of straw mass equivalent to one-twentieth of the mass of the agricultural soil (5% by mass) gives to the formed adobe a minimum thermal conductivity. As a fact, when making building bricks, the inhabitants of M'Sila use this proportion of 1/20 or 5% (empirical knowledge).
Soil and Tillage Research, 2000
Soil thermal conductivity determines how a soil warms or cools with exchange of energy by conduction, convection, and radiation. The ability to monitor soil thermal conductivity is an important tool in managing the soil temperature regime to affect seed germination and crop growth. In this study, the temperature-by-time data was obtained using a single probe device to determine the soil thermal conductivity. The device was used in the ®eld in some Jordanian clay loam and loam soils to estimate their thermal conductivities under three different tillage treatments to a depth of 20 cm. Tillage treatments were: notillage, rotary tillage, and chisel tillage. For the same soil type, the results showed that rotary tillage decreased soil thermal conductivity more than chisel tillage, compared to no-tillage plots. For the clay loam, thermal conductivity ranged from 0.33 to 0.72 W m À1 K À1 in chisel plowed treatments, from 0.30 to 0.48 W m À1 K À1 in rotary plowed treatments, and from 0.45 to 0.78 W m À1 K À1 in no-till treatments. For the loam, thermal conductivity ranged from 0.40 to 0.75 W m À1 K À1 in chisel plowed treatments, from 0.34 to 0.57 W m À1 K À1 in rotary plowed treatments, and from 0.50 to 0.79 W m À1 K À1 in no-till treatments. The clay loam generally had lower thermal conductivity than loam in all similar tillage treatments. The thermal conductivity measured in this study for each tillage system, in each soil type, was compared with independent estimates based on standard procedures where soil properties are used to model thermal conductivity. The results of this study showed that thermal conductivity varied with soil texture and tillage treatment used and that differences between the modeled and measured thermal conductivities were very small. #
The thermal conductivities of twenty-six (26) agricultural soils in Trinidad were measured in the field and the laboratory with a KD2 sensor and probe. The effect of compacting four of the soils (two clayey and two sandy) to five bulk densities (1.2 to 1.6 Mg m-3) with zero and 4% peat content at four water contents (5, 12, 19 and 26%) on thermal conductivity was further investigated in the laboratory. The thermal conductivity measured in the field ranged from 0.73 to 1.69 W m-1 o C-1 and were within 0.11 W m-1 o C-1 of the corresponding laboratory-measured values for the individual soils. Thermal conductivity of the laboratory-compacted soils ranged from 0.25 to 2.00 W m-1 o C-1 , increased with increasing bulk density and water contents but decreased with the addition of peat. The clay soils exhibited lower values of thermal conductivity than the sandy soils, at given values of bulk density, water content and peat content. Good agreement was found between the laboratory and field measurements of thermal conductivity and the corresponding predicted values using the Campbell model of thermal conductivity. The results obtained are discussed in relation to pipe laying and agricultural operations in Trinidad and Tobago. Apart from soils with appreciable sand contents, most soils would require standard backfills during cable laying.