Alumel Thermocouples Research Articles

Temperature and velocity properties of a ceiling jet impinging on an unconfined inclined ceiling

Understanding the characteristics of ceiling jet flow is important because most fire detectors and suppression devices are designed to operate within the ceiling jet; the increases in temperature and smoke concentration within the ceiling jet become trigger occupants to begin fire-fighting action or to evacuation. A series of pool fire tests was conducted using a flat, unconfined model ceiling with dimensions of 2.5m (D)×3.0m (L) and changing the ceiling inclination angle of up to 40°. A single ceiling height is used. Two fire heat release rates were used to evaluate the effects: one with and the other without the flame tip touching the inclined ceiling under a steady-state condition. Maximum temperature and its position were determined based on the measurement using a rake consisting of 0.2-mm-diameter chromel–alumel thermocouples. The maximum velocity and its position were obtained by the particle image velocimetry method. These data were compared with the velocities obtained using a bi-directional flow probe and the relationship between them was clarified. Empirical formulae for the temperature rise and velocity versus the radial distance from the plume impingement point along the steepest run in the upward direction were developed considering the effect of the inclination angle. Variations in the Froude number and the Richardson number with radial distance were clarified with and without the flame tip touching the inclined ceiling.

Synthesis of WO3 nanorods by the oxidation of bulk tungsten samples with supercritical water

dT/dt = 2 K min -1 . A cell with a specified amount of water and a cell with the 〈W〉 sample were loaded in the reactor. In entries 2—4, only a cell with the 〈W〉 sample was loaded in the reactor and water at the supercritical parameters (Т > 647 K, P > 22.1 MPa) was sprayed in the preheated reactor through a highperformance gate from a prereac� tor. After water was sprayed, the temperature of the reac� tor was maintained constant. The volume of the prereac� tor is ∼20 times of the volume (VR) of the reactor occupied with water. The pressure (P) was measured by membrane tensiosensors, whose accuracy in the range from 1 to 40 MPa was 0.25%. The temperature regime of the reactor was established by a thermoregulator using ohmic heaters and chromel—alumel thermocouples. The temperature dependence of the hydrogen pressure was measured in en� try 1, and the time dependence of the hydrogen pressure was measured in entries 2—4. At the end of experiments the reactor was rapidly cooled. Water and Н 2 , which was formed upon oxidation, were collected in a collector cooled with liquid nitrogen. The amount of hydrogen NH2 was determined from the results of measurements of the H2 pressure in a volumetric cylinder of a known volume, and the gas composition in the cylinder was measured on a quadrupole mass spectrometer. 6 In addition, the weights m0 of the 〈W〉 samples were measured before and after oxidation, and the difference indicated the weight increase Δm. The values of the above parameters are given in Table 1

Packaging of Surface Micromachined Thin Film Thermocouples (TFT): Comparison of the Resistance Arc Microwelding Technique With Wire Bonding

In this paper, we report the packaging of thin film thermocouples (TFT) using resistance arc welding technique. Parallel gap welding and spot welding have been reported in the literature for attaching thin wires to metal thin films. To the knowledge of the authors, this is the first time resistance arc welding has been reported as a packaging technique for microfabricated devices. A brief description of the microfabrication process and chemical analysis using X-ray photoelectron spectroscopy (XPS) of the vapor deposited alloy constituents for the TFT are reported in this study. K-type (chromel and alumel) thermocouple wires were used as targets for physical vapor deposition of the component layers of the TFT. The calibration of the TFT using high-speed data acquisition is reported. The calibration curves of TFT packaged using ultrasonic wire bonding of Al wires are compared with TFT packaged using resistance arc welding of K-type thermocouple wires. TFT packaged using resistance arc welding is found to have better temperature response under steady-state conditions.

Characteristics of Micro-Thermoelectric Mass Flow Sensors with Si3N4/SiO2/Si3N4 Thermal Isolation Membrane

Two different kinds of thermoelectric mass flow sensor were fabricated and their characteristics were discussed. A meandering Pt-heater and Bi–Sb or chromel–alumel thermocouple hot junctions were realized on a stress-compensated 150 nm Si3N4/300 nm SiO2/150 nm Si3N4 membrane thermally isolated from the silicon substrate using silicon bulk micromachining. To investigate the flow-induced variations of temperature distribution quantitatively, four thermocouple hot junctions were located symmetrically at each side of a Pt-heater along the flow direction. The flow path tube was prepared on the back of the sensor. The N2-flow sensitivity value for the sensor with the Bi–Sb thermocouples was found to be much higher than that for the sensor with the chromel–alumel thermocouples. However, the linear range of the N2-flow sensitivity for the sensor with the chromel–alumel thermocouples was wider than that for the sensor with the Bi–Sb thermocouples.

Effect of electric fields on oxygen exchange reactions during sodium perchlorate thermolysis

Alkali metal perchlorates are known as oxidizers widely used in propellants, pyrotechnics, catalysts, and other fields [1]. These compounds contain significant proportions of oxygen, so they can also be successfully employed as solid oxidizers in the self-propagating high-temperature synthesis (SHS) of functional oxide materials (ferrites, ferroelectrics, high- T c superconductors, and others) [2]. In the combustion synthesis of complex oxides, the quality of the ultimate product is significantly affected by the degree of coincidence of the peak of perchlorate decomposition with oxygen gas evolution and the peak of metal fuel oxidation [3]. Usually, numerous test-and-trial experiments are needed to solve this problem and to find an optimal batch composition. In this context, it is pertinent to search for means of controlling such processes, especially for distant control means. It was discovered that, for example, strong electric fields generated by a condenser under SHS conditions substantially change the combustion process parameters [4]. The magnetic parameters of some ferrites are substantially modified during SHS in electric fields. To explain the effect of external physical actions on combustion and phase formation during the synthesis of complex oxide materials, it was hypothesized that electromagnetic fields applied to the zone of intense chemical reactions affect the kinetics of the decomposition of solid intrareaction oxidizers [5]. In addition, it cannot be ruled out that such actions affect oxygen exchange during the formation of complex oxides. In order to elucidate possible effects of electric fields, we believed it important to recognize the major SHS stages and to analyze the field effects on each stage. In this context, by way of example we studied the decomposition kinetics in electric fields for pure sodium perchlorate. The experimental setup used to study sodium perchlorate thermolysis (Fig. 1) was a vertical furnace equipped with a kanthal wire heater, with two tubular chambers 20 mm in inner diameter. The furnace was mounted between two copper plates, which were isolated with Teflon liners 1 mm thick and to which voltage up to 25 kV could be applied. Crucibles 18 × 24 mm in size, one containing powdered sodium perchlorate and the other containing a reference (NaCl), were simultaneously inserted into the chambers preheated to the required temperature ( 750°C ). Chromel‐ Alumel thermocouples were embedded beforehand into the powder to a depth of about 3 mm. Thermocouple signals were recorded with a potentiometer equipped with an xy plotter. Sodium perchlorate (99+%) from Acros Organics pounded in an agate mortar with a pestle was used in the experiments.

Thermal processes in electroslag surfacing of rolling rolls in a current-conducting solidification mould

Electroslag surfacing in a current-conducting solidification mould is one of the promising methods of reconditioning rolling rolls. The production of highquality metal is determined by the treatment of deposited metal with high-activity and refining slags, by the electromagnetic effect on the liquid metal, and by the accelerated cooling of the solidifying deposited layer. Nevertheless, the final result of surfacing, i.e. production of high-quality bimetallic components, is controlled by the thermal processes taking place in the melting space of the solidification mould. In this work, investigations were carried out into the thermal state of blanks of rolls in long-term surfacing. Surfacing trials were carried out on blanks of rolls of 2000 OAO NLMK rolling mill, with the diameter of 810 mm, the length of the barrel 2000 mm, the total length of approximately 5000 mm, weight approximately 13 t. The temperature changes in the bank in surfacing were estimated for two cases: with the heating of the blanks in the furnace prior to surfacing and in an additional application of heating during surfacing. Measurements were taken of the surface temperature of the barrel and the neck of the roll, and the temperature of the slag pool on the surface and in the depth was measured. Temperature was measured with measuring devices of four types: a contact chromel–alumel thermocouple, a Hefest optical pyrometer with the maximum measured temperature of 600 oC, a Cyclops infrared thermometer with the measurement range 600–1600 oC, and using TPR-91-1200 thermoelectric block with the tungsten–rhenium immersion thermocouples. Surfacing was carried out in a modernized electroslag furnace EShP-10VG. Modernization consisted of organizing the working area carrying a currentconducting solidification mould and devices form supplying surfacing shot (figure 1), and also devices for centring the roll and supplying current to the lower part of the roll. Prior to surfacing, the roll was preheated in a shaft furnished to a temperature of 600 oC, which was reduced during technological operations: extraction of the role from the heating furnace, transport by a shop crane to the surfacing equipment, insertion into the solidification mould, centring and securing in the strictly vertical position. The main task of preheating the roll was to ensure price surfacing (prior to pouring the slag into the solidification mould) of the surface temperature not lower than 250–300 oC. As shown by experience in practice, Thermal processes in electroslag surfacing of rolling rolls in a current-conducting solidification mould

Autonomous and forced oscillations during methane oxidation over cobalt catalysts

Abstract Oscillatory behaviour during methane oxidation over a cobalt foil has been studied using on-line mass-spectrometry and video recording of the colour of the catalyst surface. It was demonstrated that during oscillatory behaviour, periodic transitions of the catalyst surface from an oxidised state (dark colour) to a reduced state (light colour) occurred together with the variation of the catalyst temperature. Oscillations over the cobalt foil appeared at higher temperatures (860–950 °C), and had longer periods, in comparison with oscillatory behaviour which was observed earlier over a nickel foil. The application of TGA in combination with TPR experiments revealed the differences in nickel and cobalt redox properties which are responsible for the variation in the properties of the oscillations. Forced oscillations could be obtained in a low temperature region (700–860 °C), if bare chromel and alumel wires were spot-welded separately to the cobalt foil. It was shown that in this case the chromel wire induced oscillatory behaviour of the whole cobalt foil. Complicated mixed mode oscillations detected at higher temperatures were shown to be the result of the coupling of high frequency oscillations produced by the unshielded chromel–alumel thermocouple and low frequency oscillations appearing over the cobalt foil.

Dynamic behaviour of Ni-containing catalysts during partial oxidation of methane to synthesis gas

Complex dynamic phenomena—oscillations and temperature waves—are observed during partial oxidation of methane to synthesis gas over Ni-containing metal catalysts (Ni metal foam and chromel–alumel thermocouple). Kinetic analysis of oscillatory process shows that a substantial amount of oxygen and carbon is stored and evolved by catalysts during the cycle. A sharp splash of activity is observed when amounts of stored oxygen and carbon are minimal. It was concluded that the oscillatory behaviour could be due to a difference in the activities of C- and O-covered and clean metal. A “direct” mechanism of CO and H2 formation without intermediate total oxidation is more probable than a “sequential” one.

Irradiation effects on temperature sensors for ITER application

The effect of neutron and gamma irradiation and magnetic fields on temperature sensors has been reviewed for the particular environment of the International Tokamak Experimental Reactor (ITER). Both Chromel–Alumel and Nicrosil–Nisil thermocouples are expected to be unaffected by neutron irradiation over the entire life time of ITER. Based on the available data, no significant radiation-induced electromotive force effects are to be expected. Magnetic field effects on Chromel–Alumel thermocouples could under certain conditions become important and, in this case, Nicrosil–Nisil thermocouples are recommended. For high temperature measurements (T>1200 °C) in ITER conditions, tungsten–rhenium thermocouples are the most appropriate choice. Resistance thermometers, on the other hand, were found not to be usable in a reactor environment.

Thermoelectric power measurement under hydrostatic pressure using a self-clamped pressure cell

A thermoelectric power (TEP) measurement technique in a self-clamped pressure cell is presented. Thermal and electrical contacts were glued to heaters by Stycast epoxy, which enhances thermal integration. The pressure effect of Chromel–Constantan and Chromel–AuFe0.07% thermocouples are compared to Chromel–Alumel thermocouples, which are known to be pressure insensitive between 4.2 and 300 K. The investigated thermocouples are found to have a small pressure effect; ∼±4% at maximum in the measured temperature and pressure range. Any pressure effect on Au wires was also found to be very small from the pressure-dependent TEP measurement of YBCO superconductor below Tc.

Rate oscillations during partial oxidation of methane over chromel-alumel thermocouples

A chromel–alumel thermocouple has been found to catalyse the methane/oxygen reaction, the main products being CO, H2 with some CO2 and H2O. Regular oscillations in both reactants, products and temperature have been observed at temperatures around 700 ○C. Similar behaviour has been obtained using nickel wires.

INVESTIGATION OF IGNITION OF THERMOPLASTICS THROUGH THE HOT WIRE IGNITION TEST

The purpose of this study was to investigate the ignition phenomena of selected polymeric materials—Plexiglas® (PMMA), polyethylene, Lexan® (polycarbonate), and nylon using the Hot Wire Ignition Test. Underwriters' Laboratories (UL) prescribe this test for polymeric materials used in enclosures or insulation systems of electrical equipment. The main objective of this study was to identify the effect of specimen thickness on the ignition time. In addition, temperature changes at the surface of selected polymeric materials during the different phases of the ignition process were also investigated. The apparatus used for this test was specified by ASTM D 3874–90a—Standard Test Method for Ignition of Materials by Hot Wire Sources. It consisted of a supply circuit capable of maintaining a continuous 60-Hz power density of 0.26 W/mm over 12 in. (304.8 mm) of No. 24 AWG, Nichrome V wire and a variable transformer for adjustment of the voltage to achieve the desired current. Temperature measurements were also performed using a Cole-Parmer Digi Source® 12-channel scanning thermometer and 30 AWG chromel–alumel (type K) thermocouples. A linear relationship between time to ignition and thickness was verified for the four polymers of thicknesses 1/16 in., 1/8 in., 3/16 in., and 1/4 in. The different polymers evaluated in terms of ease of ignition from most ignitable to least ignitable were in the order: Plexiglas, polyethylene, Lexan, and nylon. From the temperature measurements performed in tests with Plexiglas, it appears that the major factor affecting the time to ignition is the rate of temperature rise during the decomposition process. One important recommendation is that temperature measurements similar to those performed with four thicknesses of Plexiglas should be performed with Lexan (polycarbonate), nylon, and polyethylene. These data would confirm the principal role played by the rate of temperature rise during the decomposition process on the time to ignition of thermoplastic materials.

Leaf temperature error from heat conduction along thermocouple wires

Heat conduction through the wires is one source of thermocouple (TC) error. Leaf temperature measurement may be affected by this error if the leaf-to-air temperature difference is large and contact between TC and leaf is inadequate. Selection of small diameter TCs with low thermal conductivity, as well as good contact with the leaf, are possible solutions to the problem. A laboratory experiment was carried out to determine conduction error as a function of TC-type, wire diameter, insulation and length of contact between wire and leaf. Most of the tests were conducted with a thin plastic plate, as a leaf-substitute, to ensure repetitiveness. Some measurements were also made with in vivo pepper and tomato leaves, to determine a correction factor. Different lengths of the TC wires were glued to the plate, or leaf, to ensure good contact. Controllable temperature differences were established with a thermo-electric cooler. A conduction error, τ, of 1% (relative to the leaf-to-air temperature difference) is to be expected when a length of about 22 mm of AWG 40 (0.08 mm diameter), teflon-insulated type-T (copper–constantan) thermocouple is glued to a leaf. Removing the insulation reduces this length to 14 mm, and replacing the insulated type-T thermocouple by an insulated type-K (chromel–alumel) thermocouple of the same gage, requires about 10 mm for the same 1% error. An approximate theoretical solution was obtained, which relates relative measurement error, τ, to normalized glued length, ξ, in the form τ = exp{− ξ}. This relationship can be used to estimate errors with other TCs.

Electron Beam Evaporation of Nickel Manganite Thin-film Negative Temperature Coefficient Thermistors

Thermistors (i.e., temperature-sensitive resistors) were introduced in the late 1940s [1] as sensors relying on the large temperature dependence of the resistivity of transition-metal oxides. These metal oxides, typically with spinel-type crystal structure, may be classi®ed in terms of chemical composition, temperature range, etc. [2]. In particular, negative temperature coef®cient (NTC) thermistors are devices whose resistance decreases with increasing temperature. They are usually ceramic materials and often possess a very high temperature dependence of electrical resistance. Generally, these materials consist of transition metal (for example, Cu, Co, Ni) spinel manganites and form an important part of the general technology of electroceramics (infrared bolometers, temperature captors, etc.). Although NTC thermistors have been produced commercially for some time, problems with stability, reproducibility and the ease of production still persist. These problems are inherent in powder processing, where control of porosity and stoichiometry are dif®cult and lead to poor run-to-run reproducibility and irregularities in the resulting devices. Such dif®culties should be less severe in dense thin ®lms, where there are no pores and where control of deposition parameters is better, at least in principle. In addition, the uniform incorporation of dopants is generally more straightforward, offering greater exibility. Nickel manganite is a signi®cant compound within the series of solid solutions formed from the solidstate reaction in air between nickel oxide and manganese oxide. Several investigations have reported on the measurements of electrical and magnetic properties [3±6], X-ray photoelectron spectroscopy [7] and microstructural studies [8]. In the literature, however, most NTC studies are for thick-®lm or ceramic pill structures [9], and there has been little reported on thin-®lm thermistors. Fau et al. reported the fabrication of the thin ®lms of nickel manganese oxide using RF reactive sputtering [10], and more recently Kao et al. reported on the preparation of (Mn0:5Co0:6Ni0:1)3O4 NTC thin ®lms by RF reactive sputtering [11]. In this study, the source powders were made by calcining a 1:1 molar-weighted mixture of NiO and Mn2O3 powders at 900 8C for 2 h. After calcination, the source material was placed into specially designed graphite crucibles, 13 mm in diameter, and mounted on a water-cooled movable pedestal in the e-beam evaporation system, comprising a variety of substrates including chemically cleaned glass, alumina with a pre-printed platinum comb electrode structure for electrical measurements and Si wafers for X-ray diffraction (XRD) studies. They were placed on a substrate holder 15 cm above the source, and during the deposition, substrate temperature was monitored using a chromel±alumel thermocouple and a Eurotherm Cal 9900 temperature controller. Deposition was carried out in a conventional oilpumped vacuum system capable of achieving pressures of 10y5 mbar. The source was heated by a beam of energetic electrons emitted from a tungsten ®lament and focused onto the surface of the source by applying a high negative voltage ( 3 kV) between the ®lament housing and the source, which was grounded. In this study, there was no intentional heating of substrates, although substrate temperatures were observed to rise to 80 8C during growth. Structural analysis of the thin ®lms was carried out using a Philips PW 2273 powder X-ray diffractometer, while a Cambridge Instruments S180 scanning electron microscope (SEM) equipped with a Link System energy dispersive X-ray (EDX) facility was used to determine the composition of the ®lms. Finally, the temperature-dependent resistance was measured between room temperature and 600 K in a purpose-built controlled oven using a Keithley 195A digital multimeter, a Eurotherm Cal 9900 temperature controller and a chromel±alumel thermocouple. The thickness of the thin ®lms, measured using a Tencor 200 alpha step pro®leometer, were found to be 1 im. The EDX analysis of the thin ®lms showed that all the deposited thin ®lms contained Mn and Ni (Fig. 1), and no peaks due to other elements were observed in any of the spectra. The ratio of the Ni to the Mn peaks, was found to be different, however, when the source material and thin ®lms were compared: the Ni=Mn EDX peak ratio for the source powder was around 0.15, while in the thin ®lms it was 0.45. Post-growth annealing did not appear to change this ratio in any of the thin ®lms. The XRD results are presented in Fig. 2, which shows XRD traces from an as-deposited ®lm, a layer annealed at 500 8C for 30 min and from a layer

Study on Thermal Shock in Si3N4/SiC platelets

Intensive investigations have been carried out to improve the mechanical behavior of silicon nitride. Studies show an increase of mechanical resistance and creep resistance through the incorporation of reinforcement compounds such as ®bers, whiskers and platelets [1±6], as well as through the use of additives, which lead to a partial crystallization of the grain boundary vitreous phase [7±9]. In recent years, platelets have been used more than whiskers due to the toxicity of the latter. Alumina and silicon carbide platelets have been used to reinforce monolithic ceramic matrices [1±3, 10±12] and vitreous ceramics [13]. In both cases, the mechanical properties showed an improvement over the base material. Silicon nitride is a material with great potential under high temperatures. It is therefore important that it should resist thermal gradients. While there are several works in the literature related to thermal shock resistance of pure silicon nitride, none report the effects caused by sudden temperature changes on the residual mechanical resistance of silicon nitride reinforced by silicon carbide platelets. The purpose of this work is to investigate the damage occurring in this composite material when submitted to thermal shock. The material studied was fabricated by conventional hot-pressing of a silicon nitride powder (SNE 10, Ube Corp., Japan) containing as sintering additives 5 and 2 wt % of aluminum and yttrium oxide, respectively. As the reinforced phase, 20 v=o of monocrystalline silicon carbide platelets were added (32±50 im, American Matrix, Knoxville, USA). Fig. 1 shows a scanning electronic microscope (SEM) micrograph of monocrystalline silicon carbide platelets used in this work. One can easily notice that the platelets present a hexagonal format. The powder mixture of silicon nitride and silicon carbide platelets was pressed at 1800 8C in graphite dies. Details on the preparation of this composite have been described elsewhere [1, 14]. Thermal shock treatment was undertaken by heating the samples in a vertical tubular furnace to a particular temperature. The temperature was measured by a cromel±alumel thermocouple beside the samples. The samples (having dimensions of 4 3 4 3 50 mm) considered for mechanical resistance measurement were ground and polished and had rounded edges. After 10 min under constant temperature, the samples were released and allowed to fall into a water reservoir at 25 8C. After thermal shock, residual exure strength tests by the four-point bending test were performed using a cross-head speed of 0.05 mm miny1 and a standard testing machine (Instron), with inner and outer spans of 20 (e) and 40 mm (l), respectively (Fig. 2). To evaluate the thermal shock behavior of the composite, two parameters, R and R, were calculated. The determination of these two parameters are based on Hasselman's theory [15]. After the rupture, the width and length of the samples were measured in the region of the fracture.

An experimental study of natural convection in a volumetrically heated spherical pool bounded on top with a rigid wall

Flooding of the reactor cavity is being considered as a cooling strategy to prevent vessel thermal failure in the case of severe core damage accidents in which relocation of core material into lower vessel head occurs. A recent study carried out at UCLA showed that the flooding of cavity could indeed be a viable option. However, one important factor contributing to uncertainty in that study was the internal natural convection heat transfer coefficient. In the present work, experiments were conducted to examine natural convection heat transfer in internally heated hemispherical pools with external cooling. In the experiments, Freon-113 contained in a Pyrex bell jar, was used as a test liquid and the vessel was cooled from the outside with water. The pool was bounded with a rigid wall at the top, and was heated with a 750 W magnetron taken from a conventional microwave oven. The vessel inner wall temperature was not held constant and varied from the stagnation point to the equator. A series of chromel alumel thermocouples was used to measure the pool and wall temperatures at different locations.Experiments were performed for pools with nearly insulated and cold rigid walls at the top. The depth of the pool was varied parametrically. Both local and average heat transfer coefficients based on maximum pool temperature were obtained. The results have been compared with the correlations obtained for pools with free surface.

Experimental Investigation of Natural Convection Heat Transfer in Volumetrically Heated Spherical Segments

External cooling of a light water reactor vessel by flooding of the concrete cavity with subcooled water is one of several management strategies currently being considered for accidents in which significant relocation of core material is predicted to occur. At present, uncertainty exists with respect to natural convection heat transfer coefficients between the pool of molten core material and the reactor vessel wall. In the present work, experiments were conducted to examine natural convection heat transfer in internally heated partially filled spherical pools with external cooling. In the experiments, Freon-113 was contained in a Pyrex bell jar, which was cooled externally with subcooled water. The pool was heated using a 750 W magnetron taken from a conventional microwave. The pool had a nearly adiabatic free surface. The vessel wall temperature was not uniform and varied from the stagnation point to the free surface. A series of chromel–alumel thermocouples was used to measure temperatures in both steady-state and transient conditions. Each thermocouple was placed in a specific vertical and radial location in order to determine the temperature distribution throughout the pool and along the inner and outer walls of the vessel. In the experiments, pool depth and radius were varied parametrically. Both local and averages heat transfer coefficients based on pool maximum temperature were obtained. Rayleigh numbers based on pool height were varied from 2 × 1010 to 1.1 × 1014. Correlations for the local heat transfer coefficient dependence on pool angle and for the dependence of average Nusselt number on Rayleigh number and pool depth have been developed.

Microsecond time scale thermocouple temperature measurements in solid penetrated by a shaped charge jet

The development of microsecond time scale temperature measurements in shock-loaded solids is briefly reviewed. The feasibility of making thermocouple temperature measurements near a cavity created by a shaped charge jet in medium carbon steel and glass fiber reinforced epoxy composite solid targets has been studied. Thermal diffusion calculations demonstrated that these measurements were feasible if the foil thermocouple was on the order of 600 Å thick. Chromel–alumel thermocouples were used because of the anticipated temperature measurement range and also because they have a small pressure correction. The thermocouple fabrication method is discussed in this article. By embedding the thermocouples in the target plates at different distances from the shaped charge generated cavity, temperature distributions were obtained in the steel and composite materials. These temperature distributions were shown to be consistent with temperatures for melting at the cavity in the steel and for epoxy degradation in the composite material.

On the temperature distribution in liquid–vapor phase change between plane liquid surfaces

The problem of temperature distribution in liquid-vapor phase change between plane liquid surfaces is considered both analytically and experimentally. Classical kinetic theory calculations indicate that for a monatomic vapor, large temperature jumps exist at the interfaces, large enough possibly to cause the temperature distribution to be anomalous. Surprisingly, no experimental results have been reported so far. A continuum analysis, with special consideration of the Knudsen layers, clearly establishes the adverse roles played by polyatomic molecules and the presence of a contaminant gas. The need to work with monatomic vapors under low levels of contamination is clearly indicated. An experimental setup was constructed to measure temperature distributions in the vapor between an evaporating liquid surface and a cooler condensing surface. Temperature distributions were measured using Chromel–Alumel thermocouples. Measurements were made in water, Freon 113, and mercury. The temperature profiles obtained in mercury, over a wide range of temperatures, clearly show large temperature jumps at the interfaces, as large as almost 50% of the applied temperature difference. These results appear to be the first to confirm this important phenomenon.

Controlling thermal stresses in I-beams during their cooling after rolling

The temperature in elements of the I-beam during its cooling was measured by attaching Chromel--Alumel thermocouples i0 mm apart to the middle of the shape about its perimeter. A lO00-mm-10ng specimen with thermocouples connected to 12-channel automatic potentiometers was placed in a gas-fired furnace and heated to 1000~ The specimen and thermocouples were then extracted from the furnace and placed on the hot bed of the rolling mill. The specimen was cooled by one of two methods: I) At room temperature, with natural aeration of the ambient air; 2) accelerated cooling with compressed air delivered from slit-type nozzles to the middle of the flanges of the I-beam.