An experimental setup for the simultaneous measurement of thermoelectric power of two samples from 77 K to 500 K.

PubMed

Tripathi, T S; Bala, M; Asokan, K

2014-08-01

We report on an experimental setup for the simultaneous measurement of the thermoelectric power (TEP) of two samples in the temperature range from 77 K to 500 K using optimum electronic instruments. The setup consists of two rectangular copper bars in a bridge arrangement for sample mounting, two surface mount (SM) chip resistors for creating alternate temperature gradient, and a type E thermocouple in differential geometry for gradient temperature (ΔT) measurement across the samples. In addition, a diode arrangement has been made for the alternate heating of SM resistors using only one DC current source. The measurement accuracy of ΔT increases with the differential thermocouple arrangement. For the calibration of the setup, measurements of TEP on a high purity (99.99%) platinum wire and type K thermocouple wires Chromel and Alumel have been performed from 77 K to 500 K with respect to copper lead wires. Additionally, this setup can be utilized to calibrate an unknown sample against a sample of known absolute TEP.

An experimental setup for the simultaneous measurement of thermoelectric power of two samples from 77 K to 500 K

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tripathi, T. S.; Bala, M.; Asokan, K.

2014-08-01

We report on an experimental setup for the simultaneous measurement of the thermoelectric power (TEP) of two samples in the temperature range from 77 K to 500 K using optimum electronic instruments. The setup consists of two rectangular copper bars in a bridge arrangement for sample mounting, two surface mount (SM) chip resistors for creating alternate temperature gradient, and a type E thermocouple in differential geometry for gradient temperature (ΔT) measurement across the samples. In addition, a diode arrangement has been made for the alternate heating of SM resistors using only one DC current source. The measurement accuracy of ΔTmore » increases with the differential thermocouple arrangement. For the calibration of the setup, measurements of TEP on a high purity (99.99%) platinum wire and type K thermocouple wires Chromel and Alumel have been performed from 77 K to 500 K with respect to copper lead wires. Additionally, this setup can be utilized to calibrate an unknown sample against a sample of known absolute TEP.« less

Metallic Junction Thermoelectric Device Simulations

NASA Technical Reports Server (NTRS)

Duzik, Adam J.; Choi, Sang H.

2017-01-01

Thermoelectric junctions made of semiconductors have existed in radioisotope thermoelectric generators (RTG) for deep space missions, but are currently being adapted for terrestrial energy harvesting. Unfortunately, these devices are inefficient, operating at only 7% efficiency. This low efficiency has driven efforts to make high-figure-of-merit thermoelectric devices, which require a high electrical conductivity but a low thermal conductivity, a combination that is difficult to achieve. Lowered thermal conductivity has increased efficiency, but at the cost of power output. An alternative setup is to use metallic junctions rather than semiconductors as thermoelectric devices. Metals have orders of magnitude more electrons and electronic conductivities higher than semiconductors, but thermal conductivity is higher as well. To evaluate the viability of metallic junction thermoelectrics, a two dimensional heat transfer MATLAB simulation was constructed to calculate efficiency and power output. High Seebeck coefficient alloys, Chromel (90%Ni-10%Cr) and Constantan (55%Cu-45%Ni), produced efficiencies of around 20-30%. Parameters such as the number of layers of junctions, lateral junction density, and junction sizes for both series- and parallel-connected junctions were explored.

Thermocouple Errors when Mounted on Cylindrical Surfaces in Abnormal Thermal Environments.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakos, James T.; Suo-Anttila, Jill M.; Zepper, Ethan T.

Mineral-insulated, metal-sheathed, Type-K thermocouples are used to measure the temperature of various items in high-temperature environments, often exceeding 1000degC (1273 K). The thermocouple wires (chromel and alumel) are protected from the harsh environments by an Inconel sheath and magnesium oxide (MgO) insulation. The sheath and insulation are required for reliable measurements. Due to the sheath and MgO insulation, the temperature registered by the thermocouple is not the temperature of the surface of interest. In some cases, the error incurred is large enough to be of concern because these data are used for model validation, and thus the uncertainties of themore » data need to be well documented. This report documents the error using 0.062" and 0.040" diameter Inconel sheathed, Type-K thermocouples mounted on cylindrical surfaces (inside of a shroud, outside and inside of a mock test unit). After an initial transient, the thermocouple bias errors typically range only about +-1-2% of the reading in K. After all of the uncertainty sources have been included, the total uncertainty to 95% confidence, for shroud or test unit TCs in abnormal thermal environments, is about +-2% of the reading in K, lower than the +-3% typically used for flat shrouds. Recommendations are provided in Section 6 to facilitate interpretation and use of the results. .« less

Influence of argon pressure and current density on substrate temperature during magnetron sputtering of hot titanium target

NASA Astrophysics Data System (ADS)

Komlev, Anton A.; Minzhulina, Ekaterina A.; Smirnov, Vladislav V.; Shapovalov, Viktor I.

2018-01-01

The paper describes physical characteristics of the hot target sputtering process, which have not been known before. To switch a magnetron over to the hot target regime, a titanium disk of 1 mm thick with a 1-mm-gap was attached on a 4-mm-thick copper plate cooled by running water. A thermocouple sensor was used to investigate the thermal processes occurring in substrates. The study was performed at the discharge current density of 20-40 mA/cm2 and argon pressure of 3-7 mTorr. The accuracy of temperature measurement appeared to be within ± 5%, due the application of a chromel-copel thermocouple. The study reveals that under these conditions the heating curves have the inflection points positioned proportionally to the discharge current density and argon pressure on a time axis. The inflection point appears in the kinetic curves due to the finite value of the target heating time constant. The study shows that the substrate fixed temperature and substrate heating time constant depend on the argon pressure and relate to the current density by the polynomials of the first and second degrees, respectively. The influence of a target on the substrate heating kinetics is considered in an analytical description by the introduction of a multiplier in the form of an exponential function of time. The results of the research make a novel contribution to the field of the sputtering process.

High-performance coaxial EPR cavity for investigations at elevated temperatures and pressures

NASA Astrophysics Data System (ADS)

Goldberg, Ira B.; McKinney, Ted M.

1984-07-01

A microwave cavity suitable for heating a sample to temperatures above 800 °C within 15 s at gas pressures above 17.5 MPa is reported. The cavity is coaxial and operates in the TE011 mode at frequencies between 9 and 10 GHz. The heating element is constructed of nickel-chromium (i.e., Chromel) wire. It consists of two concentric helices wound in opposite senses (directions) and connected in series so as to minimize the magnetic field generated by the heater current. The heater is potted in magnesium oxide-phosphate ceramic and placed inside of a cylinder made from 50-μm copper foil which provides uniform temperature distribution and shields the heater from the microwave field. This assembly then serves as the heating element and the coaxial conductor of the cavity. The diameter of the coaxial heater assembly is approximately 7 mm. The sample is confined by a cylindrical quartz cuvette which surrounds the coaxial conductor. Sample thicknesses of 0.2 to 1.0 mm can be used. Heating from room temperature to 800 °C requires between 15 and 20 s. Operating pressures up to 17 MPa have been used, although the structural design limit of the brass or beryllium copper walls is greater than 22 MPa. Modulation coils are placed in recessed areas of the cavity walls and covered with a thin layer of copper. Cooling water flows through channels cut into the walls to maintain constant microwave parameters. Q factors of 8000 -12 000 can be obtained depending on the sample.

Aeroheating Measurement of Apollo Shaped Capsule with Boundary Layer Trip in the Free-piston Shock Tunnel HIEST

NASA Technical Reports Server (NTRS)

Hideyuki, TANNO; Tomoyuki, KOMURO; Kazuo, SATO; Katsuhiro, ITOH; Lillard, Randolph P.; Olejniczak, Joseph

2013-01-01

An aeroheating measurement test campaign of an Apollo capsule model with laminar and turbulent boundary layer was performed in the free-piston shock tunnel HIEST at JAXA Kakuda Space Center. A 250mm-diameter 6.4%-scaled Apollo CM capsule model made of SUS-304 stainless steel was applied in this study. To measure heat flux distribution, the model was equipped with 88 miniature co-axial Chromel-Constantan thermocouples on the heat shield surface of the model. In order to promote boundary layer transition, a boundary layer trip insert with 13 "pizza-box" isolated roughness elements, which have 1.27mm square, were placed at 17mm below of the model geometric center. Three boundary layer trip inserts with roughness height of k=0.3mm, 0.6mm and 0.8mm were used to identify the appropriate height to induce transition. Heat flux records with or without roughness elements were obtained for model angles of attack 28º under stagnation enthalpy between H(sub 0)=3.5MJ/kg to 21MJ/kg and stagnation pressure between P(sub 0)=14MPa to 60MPa. Under the condition above, Reynolds number based on the model diameter was varied from 0.2 to 1.3 million. With roughness elements, boundary layer became fully turbulent less than H(sub 0)=9MJ/kg condition. However, boundary layer was still laminar over H(sub 0)=13MJ/kg condition even with the highest roughness elements. An additional experiment was also performed to correct unexpected heat flux augmentation observed over H(sub 0)=9MJ/kg condition.

CORRELATION BETWEEN METAL-CERAMIC BOND STRENGTH AND COEFFICIENT OF LINEAR THERMAL EXPANSION DIFFERENCE

PubMed Central

Lopes, Stella Crosara; Pagnano, Valéria Oliveira; Rollo, João Manuel Domingos de Almeida; Leal, Mônica Barbosa; Bezzon, Osvaldo Luiz

2009-01-01

The purpose of this study was to evaluate the metal-ceramic bond strength (MCBS) of 6 metal-ceramic pairs (2 Ni-Cr alloys and 1 Pd-Ag alloy with 2 dental ceramics) and correlate the MCBS values with the differences between the coefficients of linear thermal expansion (CTEs) of the metals and ceramics. Verabond (VB) Ni-Cr-Be alloy, Verabond II (VB2), Ni-Cr alloy, Pors-on 4 (P), Pd-Ag alloy, and IPS (I) and Duceram (D) ceramics were used for the MCBS test and dilatometric test. Forty-eight ceramic rings were built around metallic rods (3.0 mm in diameter and 70.0 mm in length) made from the evaluated alloys. The rods were subsequently embedded in gypsum cast in order to perform a tensile load test, which enabled calculating the CMBS. Five specimens (2.0 mm in diameter and 12.0 mm in length) of each material were made for the dilatometric test. The chromel-alumel thermocouple required for the test was welded into the metal test specimens and inserted into the ceramics. ANOVA and Tukey's test revealed significant differences (p=0.01) for the MCBS test results (MPa), with PI showing higher MCBS (67.72) than the other pairs, which did not present any significant differences. The CTE (10-6 °C-1) differences were: VBI (0.54), VBD (1.33), VB2I (-0.14), VB2D (0.63), PI (1.84) and PD (2.62). Pearson's correlation test (r=0.17) was performed to evaluate of correlation between MCBS and CTE differences. Within the limitations of this study and based on the obtained results, there was no correlation between MCBS and CTE differences for the evaluated metal-ceramic pairs. PMID:19274398

U.S. Space Radioisotope Power Systems and Applications: Past, Present and Future

NASA Technical Reports Server (NTRS)

Cataldo, Robert L.; Bennett, Gary L.

2011-01-01

Radioisotope power systems (RPS) have been essential to the U.S. exploration of outer space. RPS have two primary uses: electrical power and thermal power. To provide electrical power, the RPS uses the heat produced by the natural decay of a radioisotope (e.g., plutonium-238 in U.S. RPS) to drive a converter (e.g., thermoelectric elements or Stirling linear alternator). As a thermal power source the heat is conducted to whatever component on the spacecraft needs to be kept warm; this heat can be produced by a radioisotope heater unit (RHU) or by using the excess heat of a radioisotope thermoelectric generator (RTG). As of 2010, the U.S. has launched 41 RTGs on 26 space systems. These space systems have ranged from navigational satellites to challenging outer planet missions such as Pioneer 10/11, Voyager 1/2, Galileo, Ulysses, Cassini and the New Horizons mission to Pluto. In the fall of 2011, NASA plans to launch the Mars Science Laboratory (MSL) that will employ the new Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) as the principal power source. Hundreds of radioisotope heater units (RHUs) have been launched to provide warmth to Apollo 11, used to provide heating of critical components in a seismic experiment package, Pioneer 10/11, Voyager 1/2, Galileo, Cassini, Mars Pathfinder, MER rovers, etc. to provide temperature control to critical spacecraft electronics and other mechanical devices such as propulsion system propellant valves. A radioisotope (electrical) power source or system (RPS) consists of three basic elements: (1) the radioisotope heat source that provides the thermal power, (2) the converter that transforms the thermal power into electrical power and (3) the heat rejection radiator. Figure 1 illustrates the basic features of an RPS. The idea of a radioisotope power source follows closely after the early investigations of radioactivity by researchers such as Henri Becquerel (1852-1908), Marie Curie (1867-1935), Pierre Curie (1859-1906) and R. J. Strut. Almost 100 years ago, in 1913, English physicist H. G. J. Moseley (1887-1915) constructed the first nuclear battery using a vacuum flask and 20 mCi of radium (Corliss and Harvey, 1964, Proceedings of the Royal Society, 1913). After World War II, serious interest in radioisotope power systems in the U.S. was sparked by studies of space satellites such as North American Aviation s 1947 report on nuclear space power and the RAND Corporation s 1949 report on radioisotope power. (Greenfield, 1947, Gendler and Kock, 1949). Radioisotopes were also considered in early studies of nuclear-powered aircraft (Corliss and Harvey, 1964). In 1951, the U.S. Atomic Energy Commission (AEC) signed several contracts to study a 1-kWe space power plant using reactors or radioisotopes. Several of these studies, which were completed in 1952, recommended the use of RPS. (Corliss and Harvey, 1964). In 1954, the RAND Corporation issued the summary report of the Project Feedback military satellite study in which radioisotope power was considered (Lipp and Salter, 1954, RAND). Paralleling these studies, in 1954, K. C. Jordan and J. H. Birden of the AEC s Mound Laboratory conceived and built the first RTG using chromel-constantan thermocouples and a polonium-210 (210Po or Po-210) radioisotope heat source (see Figure 2). While the power produced (1.8 mWe) was low by today s standards, this first RTG showed the feasibility of RPS. A second thermal battery was built with more Po-210, producing 9.4 mWe. Jordan and Birden concluded that the Po-210 thermal battery would have about ten times the energy of ordinary dry cells of the same mass (Jordan and Birden, 1954). The heat source consisted of a 1-cm-diameter sphere of 57 Ci (1.8 Wt) of Po-210 inside a capsule of nickel-coated cold-rolled steel all inside a container of Lucite. The thermocouples were silver-soldered chromel-constantan. The thermal battery produced 1.8 mWe.

Study of the heat-transfer crisis on heat-release surfaces of annular channels with swirl and transit flows

NASA Astrophysics Data System (ADS)

Boltenko, E. A.

2016-10-01

The results of the experimental study of the heat-transfer crisis on heat-release surfaces of annular channels with swirl and transit flow are presented. The experiments were carried out using electric heated annular channels with one and (or) two heat-release surfaces. For the organization of transit flow on a convex heat-release surface, four longitudinal ribs were installed uniformly at its perimeter. Swirl flow was realized using a capillary wound tightly (without gaps) on the ribs. The ratio between swirl and transit flows in the annular gap was varied by applying longitudinal ribs of different height. The experiments were carried out using a closed-type circulatory system. The experimental data were obtained in a wide range of regime parameters. Both water heated to the temperature less than the saturation temperature and water-steam mixture were fed at the inlet of the channels. For the measurement of the temperature of the heat-release surfaces, chromel-copel thermocouples were used. It was shown that the presence of swirl flow on a convex heatrelease surface led to a significant decrease in critical heat flows (CHF) compared to a smooth surface. To increase CHF, it was proposed to use the interaction of swirl flows of the heat carrier. The second swirl flow was transit flow, i.e., swirl flow with the step equal to infinity. It was shown that CHF values for a channel with swirl and transit flow in all the studied range of regime parameters was higher than CHF values for both a smooth annular channel and a channel with swirl. The empirical ratios describing the dependence of CHF on convex and concave heat-release surfaces of annular channels with swirl and transit flow on the geometrical characteristics of channels and the regime parameters were obtained. The experiments were carried out at the pressure p = 3.0-16.0 MPa and the mass velocity ρw = 250-3000 kg/(m2s).

Uncertainty analysis of thermocouple measurements used in normal and abnormal thermal environment experiments at Sandia's Radiant Heat Facility and Lurance Canyon Burn Site.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakos, James Thomas

2004-04-01

It would not be possible to confidently qualify weapon systems performance or validate computer codes without knowing the uncertainty of the experimental data used. This report provides uncertainty estimates associated with thermocouple data for temperature measurements from two of Sandia's large-scale thermal facilities. These two facilities (the Radiant Heat Facility (RHF) and the Lurance Canyon Burn Site (LCBS)) routinely gather data from normal and abnormal thermal environment experiments. They are managed by Fire Science & Technology Department 09132. Uncertainty analyses were performed for several thermocouple (TC) data acquisition systems (DASs) used at the RHF and LCBS. These analyses apply tomore » Type K, chromel-alumel thermocouples of various types: fiberglass sheathed TC wire, mineral-insulated, metal-sheathed (MIMS) TC assemblies, and are easily extended to other TC materials (e.g., copper-constantan). Several DASs were analyzed: (1) A Hewlett-Packard (HP) 3852A system, and (2) several National Instrument (NI) systems. The uncertainty analyses were performed on the entire system from the TC to the DAS output file. Uncertainty sources include TC mounting errors, ANSI standard calibration uncertainty for Type K TC wire, potential errors due to temperature gradients inside connectors, extension wire uncertainty, DAS hardware uncertainties including noise, common mode rejection ratio, digital voltmeter accuracy, mV to temperature conversion, analog to digital conversion, and other possible sources. Typical results for 'normal' environments (e.g., maximum of 300-400 K) showed the total uncertainty to be about {+-}1% of the reading in absolute temperature. In high temperature or high heat flux ('abnormal') thermal environments, total uncertainties range up to {+-}2-3% of the reading (maximum of 1300 K). The higher uncertainties in abnormal thermal environments are caused by increased errors due to the effects of imperfect TC attachment to the test item. 'Best practices' are provided in Section 9 to help the user to obtain the best measurements possible.« less

Enthalpy effects on hypervelocity boundary layers

NASA Astrophysics Data System (ADS)

Adam, Philippe H.

Shots with air and carbon dioxide were carried out in the T5 shock tunnel at GALCIT to study enthalpy effects on hypervelocity boundary layers. The model tested was a 1-meter long, 5-deg half-angle cone. It was instrumented with 51 chromel-constantan coaxial thermocouples and the surface heat transfer rate was computed to deduce the state of the boundary layer. Transitional boundary layers obtained confirm the stabilizing effect of enthalpy. As the reservoir enthalpy is increased, the transition Reynolds number evaluated at the reference conditions increases. This stabilizing effect is more rapid in gases with lower dissociation energy and it seems to level off when no further dissociation can be achieved. Normalizing the reservoir enthalpy with the edge enthalpy appears to collapse the data for all gases onto a single curve. A similar collapse is obtained when normalizing both the transition location and the reservoir enthalpy with the maximum temperature conditions obtained with BLIMPK, a nonequilibrium boundary layer code. The observation that reference conditions are more appropriate to normalize high enthalpy transition data was taken a step further by comparing the tunnel data with results from a reentry experiment. When the edge conditions are used, the tunnel and flight data are around an order of magnitude apart. This is commonly attributed to high disturbance levels in tunnels that cause the boundary layer to transition early. However, when the reference conditions are used instead, the tunnel and flight data come within striking distance of one another although the trends with enthalpy are reversed. This difference could be due to the cone bending and nose blunting. Experimental laminar heat transfer levels were compared to numerical results obtained with BLIMPK. Results for air indicate that the reactions are probably in nonequilibrium and that the wall is catalytic. The catalycity is seen to yield higher surface heat transfer rates than the noncatalytic and frozen chemistry models. The results for carbon dioxide, however, are inconclusive. This is, perhaps, because of inadequate modeling of the reactions. Experimentally, an anomalous yet repeatable, rise in the laminar heat transfer level can be seen at medium enthalpies in carbon dioxide boundary layers.

An Innovative Modeling and Measurement Approach to Improve Rice Water Use Efficiency in California

NASA Astrophysics Data System (ADS)

Montazar, A.; Little, C.; Rejmanek, H.; Tindula, G.; Snyder, R. L.

2014-12-01

California is amongst the top rice producing states in the USA, and more than 95 percent of California's rice is grown in the Sacramento Valley. Based on older literature, the rice water requirement (ETc), ranges between 914 and 1,100 mm. In this study, the actual rice water requirement was measured using the residual of the energy balance method over three paddy rice fields during 2011-2013 seasons in the Sacramento Valley. Net radiation and ground heat flux density were measured, and both eddy covariance (EC) and the surface renewal (SR) technique were employed to determine the sensible heat flux density. The surface renewal method uses high frequency temperature measurements from fine wire thermocouples above the canopy. Mean amplitude and duration of the ramps over half hour periods were determined using a structure function and the characteristics are employed to estimate the direction and magnitude of sensible heat flux using the ratio of the amplitude to the ramp duration as the change in temperature per unit time and the volumetric heat capacity of the air to estimate the magnitude of the heat flux. In the study, 76.2 mm diameter chromel-constantan thermocouples were used to measure high frequency temperature at 10 Hz. The results indicate that there is considerable variability in rice water use both spatially and temporally. The average three-year measured ET of the experimental fields located in Butte County was 734 and 725 mm; and in Colusa County was 771 mm. A typical crop coefficient (Kc) curve was derived from the measured ETc and reference ET (ETo) data. Spatial estimates of monthly climate data from the Sacramento Valley were used to calculate monthly mean ETo, and smooth curve fits of the monthly data gave estimates of typical daily ETo. The daily ETc was calculated as the product of ETo and Kc, and seasonal ETc was calculated by summing the daily ETc values. The results reveal that the seasonal rice ETc was less than earlier estimates. Surface renewal equipment is relatively inexpensive and it provides rice growers with remote monitoring of water consumption by tracking ETc of the paddy fields; and hence assists them to improve rice water use efficiency. The information provided here is useful for determining volumes of water for water transfers and insuring adequate water supplies for optimal production.