Publications

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Physical property measurements including viscosity, density, thermal conductivity, and heat capacity of low-molecular weight polydimethylsiloxane (PDMS) fluids were measured over a wide temperature range (-50°C to 150°C when possible). Properties of blends of 1 cSt and 20 cSt PDMS fluids were also investigated. Uncertainties in the measurements are cited. These measurements will provide greater fidelity predictions of environmental sensing device behavior in hot and cold environments.

Remote temperature sensing is essential for applications in enclosed vessels, where feedthroughs or optical access points are not possible. A unique sensing method for measuring the temperature of multiple closely spaced points is proposed using permanent magnets and several three-axis magnetic field sensors. The magnetic field theory for multiple magnets is discussed and a solution technique is presented. Experimental calibration procedures, solution inversion considerations, and methods for optimizing the magnet orientations are described in order to obtain low-noise temperature estimates. The experimental setup and the properties of permanent magnets are shown. Finally, experiments were conducted to determine the temperature of nine magnets in different configurations over a temperature range of 5 °C to 60 °C and for a sensor-to-magnet distance of up to 35 mm. To show the possible applications of this sensing system for measuring temperatures through metal walls, additional experiments were conducted inside an opaque 304 stainless steel cylinder.

The Waste Isolation Pilot Plant (WIPP) is a U.S. Department of Energy geological repository for the permanent disposal of defense-related transuranic (TRU) waste. Industrial-grade MgO consisting mainly of the mineral periclase is the only engineered barrier certified by U.S. EPA for emplacement in the WIPP in the U.S. An Mg(OH)2-based engineered barrier consisting mainly of the mineral brucite is to be employed in the Asse repository in Germany. The WIPP is located in a bedded salt formation, and the Asse repository is located in a domal salt formation. Colloids would facilitate transport of contaminants including actinides. The regulator for the WIPP, U.S. Environmental Protection Agency (EPA), expressed its interest that possible formation of mineral colloids by MgO and its hydration and carbonation products under the WIPP-relevant conditions be evaluated. In this presentation, we report a systematic experimental study to address U.S. EPA's interest. We evaluated the possible formation of mineral colloids by using two approaches. In the first approach, as the hydration products, Mg(OH)2 (brucite), and(Mg)3Cl(OH)5′4H2O (phase 5), and the carbonation product, (Mg)5(CO3)4(OH)2•4H2O (hydromagnesite), contain magnesium, should mineral fragment colloids exist, magnesium concentrations in solution samples from MgO hydration and carbonation experiments would show a dependence on ultrafiltration, i.e., a decrease in magnesium concentrations as a function of ultrafiltration with decreasing molecular weight (MW) cut-offs. Therefore, we investigated magnesium concentrations from solutions samples in hydration and carbonation experiments as a function of ultrafiltration. We ultrafiltered solutions with a series of MW cut-off filters at 100 κD, 50 κD, 30 κD and 10 κD. Our results demonstrate that the magnesium concentrations remain constant with decreasing MW cut-offs, implying the absence of mineral fragment colloids. In the second approach, because Cs+ is easily absorbed by colloids, we spiked MgO hydration and carbonation experiments under the WIPP-relevant conditions with Cs+. Then, we ultra-filtered solutions with a series of MW cut-off filters at 100 κD, 50 κD, 30 κD and 10 κD. The concentrations of Cs do not change as a function of MW cut-offs, indicating the absence of colloids from MgO hydration and carbonation products. Therefore, both approaches demonstrate that the absence of mineral fragment colloids from MgO hydration and carbonation products.

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Sandia National Laboratories has begun developing modeling and analysis tools of flow through the cemented port ion of a cemented annulus in a Strategic Petroleum Reserve (SPR) well since August of 201 5 . The goal of this work is to develop model s and testing procedures to diagnose the health of cemented annuli at SPR sites. In Fiscal Year 2016 (FY16), we have developed several tests and associated models that we believe are sufficient for this purpose. This report outlines progress made in FY16 and future work.

Mixing of injected raw (undersaturated) water with brine in Strategic Petroleum Reserve (SPR) salt caverns affects the shape of cavern walls due to leaching. Cavern shape impacts cavern geomechanical stability and available volume for oil storage. Raw water injection occurs during initial solution mining of caverns, remedial leaching of caverns, and oil drawdown. Of interest are factors that control the degree of raw water-brine mixing and thereby the concentration of the aqueous fluid mixture that contacts the salt cavern walls. It is hypothesized that poorly-mixed fresh water could potentially cause undesirable and non-uniform leaching , for example, if buoyant poorly-mixed fresh water collects and preferentially leaches under the oil-brine interface . This report presents current understanding of controls on incomplete-to-complete mixing of raw water and brine, focusing on implications for SPR cavern leaching. In the context of mixing, we review the following: SPR leaching operations; models of leaching; field measurements of leaching and cavern shapes; and previous laboratory experiments of mixing and /or leaching performed at Sandia National Laboratories. We present recent laboratory experiments in 2014-2016 that focused explicitly on understanding controls of poor-to-well mixed conditions. We find that well-mixed conditions are expected for typical operating conditions of the SPR.

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Temperature monitoring is essential in automation, mechatronics, robotics and other dynamic systems. Wireless methods which can sense multiple temperatures at the same time without the use of cables or slip-rings can enable many new applications. A novel method utilizing small permanent magnets is presented for wirelessly measuring the temperature of multiple points moving in repeatable motions. The technique utilizes linear least squares inversion to separate the magnetic field contributions of each magnet as it changes temperature. The experimental setup and calibration methods are discussed. Initial experiments show that temperatures from 5 to 50 °C can be accurately tracked for three neodymium iron boron magnets in a stationary configuration and while traversing in arbitrary, repeatable trajectories. This work presents a new sensing capability that can be extended to tracking multiple temperatures inside opaque vessels, on rotating bearings, within batteries, or at the tip of complex endeffectors.

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A study was undertaken to determine the viscosity of liquefied 20 lb/ft³ poly methylene diisocyanate (PMDI) foam and the stress required to puncture solid PMDI foam at elevated temperatures. For the rheological measurements the foam was a priori liquefied in a pressure vessel such that the volatiles were not lost in the liquefaction process. The viscosity of the liquefied PMDI foam was found to be Newtonian with a power law dependence on temperature log₁₀(μ/Pa s) = 20.6 – 9.5 log₁₀(T/°C) for temperatures below 170 °C. Above 170 °C, the viscosity was in the range of 0.3 Pa s which is close to the lower measurement limit (≈ 0.1 Pa s) of the pressurized rheometer. The mechanical pressure required to break through 20lb/ft³ foam was 500-800 psi at temperatures from room temperature up to 180 °C. The mechanical pressure required to break through 10 lb/ft³ was 170-300 psi at temperatures from room temperature up to 180 °C. We have not been able to cause gas to break through the 20 lb/ft³ PMDI foam at gas pressures up to 100 psi.

This report consolidates technical information on several materials and material classes for a fire assessment. The materials include three polymeric materials, wood, and hydraulic oil. The polymers are polystyrene, polyurethane, and melamine- formaldehyde foams. Samples of two of the specific materials were tested for their behavior in a fire - like environment. Test data and the methods used to test the materials are presented. Much of the remaining data are taken from a literature survey. This report serves as a reference source of properties necessary to predict the behavior of these materials in a fire.

A model system was developed for enabling a multiscale understanding of centrifugal-contactor liquid–liquid extraction.The system consisted of Nd(III) + xylenol orange in the aqueous phase buffered to pH =5.5 by KHP, and dodecane + thenoyltrifluroroacetone (HTTA) + tributyphosphate (TBP) in the organic phase. Diffusion constants were measured for neodymium in both the organic and aqueous phases, and the Nd(III) partition coefficients were measured at various HTTA and TBP concentrations. A microfluidic channel was used as a high-shear model environment to observe mass-transfer on a droplet scale with xylenol orange as the aqueous-phase metal indicator; mass-transfer rates were measured quantitatively in both diffusion and reaction limited regimes on the droplet scale. Lastly, the microfluidic results were comparable to observations made for the same system in a laboratory scale liquid–liquid centrifugal contactor, indicating that single drop microfluidic experiments can provide information on mass transfer in complicated flows and geometries.

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