Heat Pulse Method Research Articles

Comparison of the Argon Triple-Point Temperature in Small Cells of Different Construction

The argon triple point (T_{90} = 83.8058,hbox {K}) is a fixed point of the International Temperature Scale of Preston-Thomas (Metrologia 27:3, 1990). Cells for realization of the fixed point have been manufactured by several European metrology institutes (Pavese in Metrologia 14:93, 1978; Pavese et al. in Temperature, part 1, American Institute of Physics, College Park, 2003; Hermier et al. in Temperature, part 1, American Institute of Physics, College Park, 2003; Pavese and Beciet in Modern gas-based temperature and pressure measurement, Springer, New York, 2013). The Institute of Low Temperature and Structure Research has in its disposal a few argon cells of various constructions used for calibration of capsule-type standard platinum resistance thermometers (CSPRT) that were produced within 40 years. These cells differ in terms of mechanical design and thermal properties, as well as source of gas filling the cell. This paper presents data on differences between temperature values obtained during the realization of the triple point of argon in these cells. For determination of the temperature, a heat-pulse method was applied (Pavese and Beciet in Modern gas-based temperature and pressure measurement, Springer, New York, 2013). The comparisons were performed using three CSPRTs. The temperatures difference was determined in relation to a reference function W(T)=R(T_{90})/R(271.16hbox {K}) in order to avoid an impact of CSPRT resistance drift between measurements in the argon cells. Melting curves and uncertainty budgets of the measurements are given in the paper. A construction of measuring apparatus is also presented in this paper.

Single-tree water use and water-use efficiencies of selected indigenous and introduced species in the Southern Cape region of South Africa

In South Africa, the development of a plantation tree industry using fast-growing introduced species was accelerated by the limited extent of indigenous forests. However, concerns about the impacts of plantations on the country’s limited water resources has initiated forest hydrology research and subsequent regulation of the industry since 1972. The forestry industry’s continued efforts to sustainably meet fibre and timber demands for the country’s growing economy have prompted questions whether indigenous tree species can provide an additional low water-use form of forestry. Single-tree water use and water-use efficiencies of three indigenous species (Ilex mitis, Ocotea bullata and Podocarpus latifolius) and one introduced species (Pinus radiata) in the Southern Cape region of South Africa were quantified. The heat-pulse velocity method was used to collect hourly sap flow data over a 12-month period. Hourly weather and soil-water data were concurrently recorded and tree growth rates were determined for the year. Biophysical water-use efficiency was calculated as the ratio of utilisable biomass gained per volume of water transpired. Patterns of water use through the year were different for the different species. Pinus radiata had higher transpiration volumes and water-use efficiency levels than the indigenous species. The most transpiring Pinus radiata tree had a transpiration volume that was 4.7 times that of the most transpiring indigenous tree. Indigenous species’ relatively lower water-use efficiencies were more a consequence of slow growth rates and not high water-use rates, which could be attributed to competition for resources in the dense indigenous forest. Potential implications for further hydrological research on the development of water-use-efficient tree production systems are discussed.

Advances in Heat-Pulse Methods: Measuring Near-Surface Soil Water Content

Advances in Heat-Pulse Methods: Measuring Near-Surface Soil Water Content

Advances in Heat-Pulse Methods: Measuring Soil Water Evaporation with Sensible Heat Balance

Advances in Heat-Pulse Methods: Measuring Soil Water Evaporation with Sensible Heat Balance

Evidence for Argon Content in Pure Oxygen from Thermal Data

Since many years it is known that argon impurities in oxygen change the temperature of the oxygen triple point by \(+12 \hbox { K}{\cdot }\mathrm{mol}^{-1}\) (positive, while most impurities decrease the temperature) without any effect on the melting range of this transition, for the impurity concentrations usually encountered in nominally pure gases. It has been hypothesized that thermal measurements on the \(\alpha -\beta \) solid-to-solid transition at 23.8 K or the \(\beta -\gamma \) solid-to-solid transition at 43.8 K may give reliable evidence regarding the argon content. However, such measurements require very long times for full completion of each transition (with prohibitive costs if liquid helium is used) and for the \(\alpha -\beta \) solid-to-solid transition the heat pulse method cannot be applied reliably. The availability of closed-cycle refrigerators permits the first obstacle to be surmounted. The automatic system earlier developed at INRIM during the EU Multicells project and used extensively for the project on the isotopic effect in neon is perfectly suited for such measurements. Thus, the uncertainties of the temperature measurements are similar to those obtained previously (of the order of 0.1 mK or less). Three argon-in-oxygen mixtures were prepared gravimetrically and certified at KRISS, just as was previously done for the work on the neon isotopic compositions. Results of continuous-current measurements on the \(\alpha -\beta \) solid-to-solid transition, along with the triple-point data obtained with the heat pulse method, are presented for one cell with a known doped argon content, to be compared with similar data from a cell with oxygen of very high purity. In addition, some preliminary data for the \(\beta -\gamma \) solid-to-solid transition are given. The measurements on the mixture with the highest argon content, about \(1002\, \upmu \hbox {mol}{\cdot } \mathrm{mol}^{-1}\), imply a (linear) sensitivity of \((116 \pm 7) \hbox {K}{\cdot }\mathrm{mol}^{-1}\) for the \(\alpha -\beta \) transition. This sensitivity may be different at much lower argon contents, and follow-up measurements with the other (smaller) mixtures will shed light on the linearity of this dependence.

Effects of Biochar Amendment on Soil Thermal Properties in the North China Plain

Core Ideas Biochar may change the surface soil heat balance. Biochar significantly decreased soil thermal conductivity and thermal diffusivity. Changes were mainly attributed to soil bulk density and the biochar itself. Few studies have examined the effects of biochar amendment on soil thermal properties. Soil thermal properties dominate the storage and conduction of heat in soil, affect soil temperature and water and heat movement, and consequently influence plant growth and soil biochemical processes. A 7‐yr field experiment was performed to investigate the effects on soil thermal properties of biochar amendment at three application rates: 0 (control), 4.5 t ha−1 yr−1 (B4.5), and 9.0 t ha−1 yr−1 (B9.0). Soil heat capacity (C), thermal conductivity (λ), and thermal diffusivity (α) of the 0‐ to 5‐cm‐depth topsoil were determined throughout a corn (Zea mays L.)–wheat (Triticum aestivum L.) growing period using a heat pulse method. The results showed that soil bulk density was decreased significantly by biochar (P < 0.05). There was no significant difference in soil water content between the control and biochar treatments. There was no significant difference in the soil volumetric heat capacity between the control and biochar treatments. Soil thermal conductivity and thermal diffusivity were decreased significantly by biochar (P < 0.05). There was a strong positive relationship between soil thermal conductivity and bulk density, and between soil thermal conductivity and water content (P < 0.001, n = 99). In contrast, there was a strong negative relationship between soil thermal conductivity and biochar amount (P < 0.001, n = 99). The reduction in soil thermal diffusivity may be attributed largely to the low thermal diffusivity of biochar and the decrease in soil bulk density caused by biochar.

Single‐Probe Heat Pulse Method for Soil Water Content Determination: Comparison of Methods

Core Ideas Six methods to obtain soil water content by single probe are presented and compared. Errors of estimated soil water content by six methods increase with water content. Heating duration affects soil water content estimation errors. Four of the six methods are probe dependent but can be easily calibrated. Each method works for some soils, and combining different methods is a solution. The estimation of soil thermal conductivity (λ) using the single‐probe heat pulse (SPHP) method is well known, but estimation of soil water content (θ) using the SPHP is poorly understood. In this study, we examined six methods—λ, normalized cumulative temperature increase (TNcum), normalized maximum temperature increase (TNmax), and the reciprocals of each—for θ estimation using the SPHP. The temperature response curves of four soils at different θ were measured following 600‐s heat pulses with heating strengths of about 6 W m−1, from which λ, TNcum, and TNmax values were determined. The maximum measurement errors of these three methods were 0.11 m3 m−3 for the coarse sand and 0.01 m3 m−3 for the fine sand, sandy loam, and silty clay, except for 0.05 m3 m−3 for the fine sand by the λ(θ) method. The predicted θ from all of the λ, TNcum, and TNmax methods agreed well with that from the oven‐dry method for all soils with the exception of the TNcum(θ) and TNmax(θ) methods for the coarse sand for θ > 0.20 m3 m−3. The measurement errors and θ predictions of the 1/λ(θ) method were similar to that of the TNcum(θ) and TNmax(θ) methods, and that of the 1/TNcum(θ) and 1/TNmax(θ) methods were similar to that of the λ(θ) method. Because each of the six methods worked well for only some soils, improved estimations were obtained when the λ(θ) method was combined with the 1/TNcum(θ) [or 1/TNmax(θ)] method for coarse‐textured soils and the 1/λ(θ) method was combined with the TNcum(θ) [or TNmax(θ)] method for fine‐textured soils.

Detection of volatile impurities in turbine oils by the heat-pulse testing method

The research is aimed at development and implementation of methods and devices to control critical sections of the oil system of the power equipment that operates in the real time mode. The task was to develop a method for rapid detection of volatile impurities in turbine oils. The approach to the study is based on quantitative assessment of the short-term thermal stability of the substance that is formally associated with the content of the volatile impurity. The approach was selected on the basis of the results of search experiments taking into consideration the formulation of requirements for the method and the device, viz., (1) the method should reliably determine the moisture content in the range of 10–150 g of the impurity per ton of oil and (2) the device is to be applicable “in situ.” For this purpose, a variant of the method of the controlled pulse heating of a wire probe, a resistance thermometer, has been developed. The advantages of the method are its speed, sensitivity to small contents of volatile impurities regardless of the nature of the impurity, and smallness of methodologically contributed perturbation. The heating conditions of the probe most sensitive to the appearance of moisture— including its trace amounts—in the system, has been defined. The duration of the measurement is on the order of milliseconds; the heat flux density through the surface of the probe reaches 1 MW/m2. The essence of the method consists in measuring, in the characteristic time interval, the temperature of the thermal instability onset associated with the content of the volatile impurity. The approach proposed by the authors is aimed at increasing the lifetime of the oil and preventing unpredictable failures of the operating equipment.

A general in situ probe spacing correction method for dual probe heat pulse sensor

The dual probe heat pulse (DPHP) method is gaining popularity for measuring soil thermal properties. However, because of the fact that the DPHP measured heat capacity (c) of soil is hyper-sensitive to probe spacing variation, probe deflection causes large error in the measured c. To deal with probe deflection, recently, Liu et al. (2013) has proposed an in situ probe spacing correction method, but, their method was based on the inline deflection assumption. Wen et al. (2015) found that for non-inline deflected DPHP sensors, the method of Liu et al. (2013) provided poor reduction of the error in c. To cope with the non-inline deflection, in this study, we introduce a new DPHP sensor design by using three thermistors within the same temperature probe. A related probe spacing correction method for non-inline deflected probes was also presented. Both numerical simulation and experiment were conducted to test the new model. We define θ as the inclination angle of the probe deviation from the vertical direction. For experiment of the outward deflection (5.8°<θ<6.8°), the error in c is in the range from −23% to −76%; after inline in situ correction, the error decreases to the range of 12% to 44%; after using our non-inline in situ correction, the error is between 1% and 8%. Our three-dimensional finite element numerical simulation also demonstrates that, compared with the method of Liu et al. (2013), the new sensor and correcting method can significantly eliminate errors in c caused by probe deflections. The new DPHP sensor design and the non-inline deflection model have the potential to replace the method of Liu et al. (2013), and become the standard method for correcting probe spacing in situ.

Low-temperature heat capacities and thermodynamic functions of four-ring chain difluoromethyleneoxy liquid crystalline compounds with different alkyl terminal chain

The heat capacities of three difluoromethyleneoxy liquid crystalline compounds (n-BB(F)B(F,F)XB(F,F)-F; n = 3, 4, 5) were measured using a quantum design physical properties measurement system (PPMS) based on a heat-pulse relaxation method in the temperature range from 1.9 to 300 K. The experimental results showed that the heat capacities of these three compounds increased with the temperature increment and none of the thermal anomalies were observed in the entire temperature region; and also the heat capacity values of n-BB(F)B(F,F)XB(F,F)-F (n = 3, 5) are larger than those of 4-BB(F)B(F,F)XB(F,F)-F due to the odd–even carbon effect below 21 K. The standard molar entropies at 298.15 K and 0.1 MPa were determined to be (631.14 ± 6.31), (650.21 ± 6.50), and (697.49 ± 6.97) J K−1 mol−1 for n-BB(F)B(F,F)XB(F,F)-F (n = 3, 4, 5), respectively.

Testing the water balance model criteria using TDR measurements, micrometeorological data and satellite-based information

Aiming at developing real time water balance modelling for irrigation scheduling, this study assesses the accuracy of the soil water balance model CRITERIA, developed by the hydro-meteorological service of the Emilia-Romagna region (Italy). The model consists of (i) an algorithm for coupling the surface flow components (i.e. Richards equation), and (ii) various modules which may be applicable to different topographical and environmental conditions. In this study, CRITERIA was applied to simulate the soil water balance for an orange orchard in semi-arid Mediterranean conditions (Eastern Sicily, insular Italy) during the cropping season 2011.The model was implemented by varying the evapotranspiration rates (ET) as input; ET fluxes were estimated by using satellite-based approach and the Penman–Monteith expression for reference rates, or were directly measured by the eddy covariance technique and the sap flow heat pulse method for transpiration. Model outputs, in term of soil moisture, were validated with direct measures of volumetric soil water content obtained by time domain reflectrometry (TDR) probes. Results of the study proved the reliability of CRITERIA to reproduce the soil moisture profile at the experimental site. The model performance was significantly high when direct measurements of crop water demand were included as input for model application. The satellite-based approach provided reliable crop evapotranspiration estimates, confirming the utility of the remote sensing techniques as support for water management in agriculture.

The dual probe heat pulse method: interaction between probes of finite radius and finite heat capacity

We analyze the dual-probe heat-pulse (DPHP) method for measuring the thermal properties of soil or other media. The method involves measuring the temperature rise of a receiver probe that is parallel to, and a known distance from, an emitter probe from which a pulse of heat is released. Under the assumption that the probes are perfect conductors, we derive a semi-analytical solution for this method that accounts for the finite radius and finite conductivity of the probes and contact resistance between probe and soil. The solution in the Laplace domain is obtained by writing solutions of the Helmholtz equation around each probe as infinite series of terms involving Bessel and trigonometric functions. Addition theorems are then used to write the solutions centred at each probe in terms of solutions centred at the other probe. Truncating the series and solving a system of linear equations gives numerical values for the series coefficients, which in turn gives values of the Laplace transforms for numerical inversion. We use the solution to investigate the validity of a simpler approximate solution that is being used in conjunction with the DPHP method for thermal property determination. For what we define as typical implementations of the method, our results show that error resulting from use of the approximate solution is sufficiently small that its effect on estimated thermal properties will be negligible. The same general approach can be used to investigate a growing number of DPHP applications for which the approximate solution may be of questionable accuracy.

Evaluation of TDR for Quantifying Heat-Pulse-Method-Induced Ice Melting in Frozen Soils

The heat pulse (HP) method is the standard for measuring thermal properties of unfrozen soils, but its application in partially frozen soils is confounded by melting and refreezing of ice that changes the properties being measured, and the most widely used data analysis models do not account for these latent heat fluxes. This study combined time domain reflectometry (TDR) and HP methods to quantify HP-induced ice melting through: (i) TDR-estimated liquid water content (θl) before and after the HP; and (ii) heat capacity (Cv) calculated from TDR-estimated θl and ice content (θi) and HP-estimated apparent heat capacity (Ca). Different heat pulse durations (8–60 s) and strengths (280–2100 J m−1) during soil thawing and freezing (−35 to 25 to −35°C) were investigated on loamy sand soil samples with a water content of 0.25 m3 m−3. The results showed that the first approach was restricted by the TDR measurement uncertainty and the difficulty in synchronizing TDR measurements with the peak ice melting. Comparison of Cv and Ca showed: (i) ice melting is limited below −5°C and the HP-estimated Ca may approach the real values; (ii) application of the HP method between −5 and 0°C is largely affected by ice melting, the amount of melting ice is largest between −1.5 and −0.5°C during soil thawing but small during freezing; (iii) the maximum estimated ice melting was 0.005 to 0.02 m3 m−3 but caused significant problems in estimating heat capacity; (iv) Cv and Ca are hysteretic because of different θi at the same temperature during freezing and thawing; and (v) a good relationship between Cv and Ca and energy input was found, which may guide the optimized heat application for frozen soil and extend the possibilities for estimating frozen soil heat capacity.

Determining Soil Ice Contents during Freezing and Thawing with Thermo‐Time Domain Reflectometry

Core Ideas An optimum heat application strategy was established for measuring thermal properties with the heat pulse method in partially frozen soils. At temperatures ≤ −5°C, T‐TDR probes were able to measure soil ice content changes with acceptable accuracy. At temperatures between −5 and 0°C, soil ice contents could be estimated from water content before freezing, TDR measured unfrozen water content, and T‐TDR measured total water content at temperatures below −5°C. Determining soil ice content during freezing and thawing is important and challenging for both engineering and environmental issues. The thermo‐time domain reflectometry (T‐TDR) probe, which can monitor unfrozen soil water content and soil thermal properties simultaneously, has the potential to measure ice content in partially frozen soils. The objective of this study was to identify an optimum heat application strategy for measuring soil thermal properties with T‐TDR probes in partially frozen soil while minimizing ice melting during the process. The optimized heating schemes were then applied for monitoring soil ice content dynamics during freezing and thawing. The results indicated that the heat pulse method failed at temperatures between −5 and 0°C because of temperature field disturbances from latent heat of fusion. When soil temperatures were ≤ −5°C, ice melting during heat pulse applications could be limited effectively with a combination of 60‐s heat‐pulse duration and 450 J m−1 heating strength, or a 90‐s heat‐pulse duration and heating strength of 450 to 900 J m−1. With the optimized heating scheme, T‐TDR probes were able to measure soil ice content changes at ≤ −5°C during freezing and thawing, and the errors were within ±0.05 m3 m−3 in sandy loams and within ±0.1 m3 m−3 in soils with high clay content. At temperatures between −5 and 0°C, soil ice contents could not be measured accurately with the heat‐pulse method directly, but they could be estimated coarsely from water content before freezing, TDR measured unfrozen water content, and T‐TDR measured total water content at temperatures below −5°C.

A Dual‐Probe Heat‐Pulse Sensor with Rigid Probes for Improved Soil Water Content Measurement

The dual-probe heat-pulse (DPHP) method is attractive for measuring soil thermal properties and volumetric water content. The purpose of this study was to develop and test a DPHP sensor having rigid probes made from thick-walled stainless steel tubing (2.38-mm outside diameter). The probes of this sensor are much more resistant to deflection than those of conventional DPHP sensors, decreasing measurement error caused by probe deflection during insertion into the soil. Laboratory experiments were conducted across a wide range of saturation levels with glass beads and three soils of different textures. For inferring soil properties from the proposed sensor, we applied the recently developed identical cylindrical perfect conductors (ICPC) model instead of the infinite line source (ILS) model that is typically used. The ICPC model improves solution for heat transport through the probe–soil system by accounting for the heat capacity and radius of the probes. Our results show a root mean square error of 1.4% volumetric water content and elimination of the measurement bias typically encountered with DPHP measurements. We conclude that the improved sensor, in combination with the ICPC model, provides a general, soil-independent water content estimate that is especially suitable for field soil water content monitoring because of its robust design with rigid probes. Because of its simplicity and measurements independent of soil type, we propose the presented DPHP method as an excellent alternative to other available measurement techniques for soil water content.

Note: Inverted heat pulse method to measure heat capacity during cooling: A counterpart of conventional quasi-adiabatic heat pulse method.

A simple method to extract known amount of heat from a sample within a given time interval has been proposed. Using this method, which we call inverted heat pulse (IHP) method, absolute values of heat capacity (C(P)) during cooling can be measured in a manner similar to conventional quasi-adiabatic heat pulse method of measuring C(P) during warming. Absolute accuracy of the measured C(P) using IHP method is found to be better than 2% in the temperature range 100-300 K. Applicability of this method to a broad and hysteretic first order transition is tested by measuring C(P) of Rh doped FePt sample, which shows a antiferromagnetic to ferromagnetic first order transition with a transition width of ∼35 K and hysteresis of ∼6 K. The peak value of the measured C(P) using IHP during cooling as well as entropy change calculated from measured data is found to be in good agreement with that measured during warming using conventional quasi-adiabatic heat pulse method.

A Simple Rational Approximation for Heat Capacity Determination with the Dual-Probe Heat-Pulse Method

A number of mathematical expressions are available for calculating soil volumetric heat capacity from data obtained with the dual-probe heat-pulse (DPHP) method. One of the more attractive options is a polynomial approximation that is simple to evaluate and yields estimates of heat capacity with error no greater than about 2% for typical DPHP measurement configurations (i.e., configurations with a probe spacing of approximately 6 mm and a heating duration in the range of 8–15 s). Unfortunately, the polynomial approximation is less accurate for measurement configurations with relatively small probe spacing or a relatively long heating duration. In this note we present a rational approximation that is more accurate, has a wider range of applicability, and is even simpler in mathematical form than the polynomial approximation. The rational approximation has error no greater than 0.015% for typical DPHP measurement configurations, but its primary advantage is that it yields heat capacity estimates with error no greater than 0.03% for a wide range of measurement configurations.

Consolidation of Oil Sands Mature Fine Tailings using the Heat Pulse Probe

CSA NewsVolume 60, Issue 2 p. 15-15 Science Consolidation of Oil Sands Mature Fine Tailings using the Heat Pulse Probe First published: 03 February 2015 https://doi.org/10.2134/csa2015-60-2-6 Adapted from Min, L., S.L. Barbour, and B.C. Si. 2015. Measuring solid percentage of oil sands mature fine tailings using the dual probe heat pulse method. J. Environ. Qual. 44:293–298. View the full article online at https://doi.org/10.2134/jeq2014.06.0262 Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume60, Issue2February 2015Pages 15-15 RelatedInformation

Measuring solid percentage of oil sands mature fine tailings using the dual probe heat pulse method.

The reclamation of mature fine tailings (MFT) is a critical challenge for the oil sands industry in western Canada, and a nonradioactive, automated, and inexpensive method to monitor the MFT solidification is needed. The objective of this paper is to evaluate the feasibility of a dual-probe heat pulse (DPHP) method to measure MFT solid percentage. Dual-probe heat pulse measurements were performed on three MFT samples, each at various solid percentages. A linear relationship ( = 0.9495 + 0.0558) was established between the DPHP-measured solid percentage () and that of oven-dry method (). Six additional MFT samples were collected and measured to validate the DPHP method. The specific heats of the six MFT solids were measured independently using a modulated differential scanning calorimetry method, and the sensitivity of DPHP-measured MFT solid percentage to the specific heat of MFT solids was evaluated. The result shows that the DPHP method can be used to accurately measure MFT solid percentages, and the accuracy can be further improved if the specific heat of the MFT solids is measured independently.

Evaluation of a self-correcting dual probe heat pulse sensor

The dual probe heat pulse method (DPHP) can be used to measure soil thermal properties. However, in situ probe spacing is prone to change resulting in large errors of measured soil heat capacity c. A newly designed DPHP sensor has two thermistors in the temperature probe which can be used to calculate in situ changes in probe spacing. This new sensor has been tested under the limited condition of linear coplanar probe deflection. i.e., probes were deflected in-line but were not bent in different directions. However, actual probe deflections may not always be coplanar linear. In this study the applicability of the new DPHP sensor is evaluated in fine sand and in silica sand for a variety of probe deflections. Probes are deflected at the bottom end (bottom) or top end (top) of probes. Results indicate that the new sensor can significantly eliminate errors in c caused by coplanar and non-coplanar probe deflections. Compared with bottom deflections, top deflections have larger errors in c. Thus, theory used to correct for deflections is more applicable to bottom deflections than to top deflections. The errors in c for saturated soil materials are larger than the errors in c for dry soil materials, because of the finite response times of the thermistors used in the probes. Clearly, the newly designed DPHP sensors have the potential for reducing errors caused by various kinds of probe deflections that may be encountered in the field.