T-type Thermocouples Research Articles

Solidification of a Liquid Super-Eutectic Binary Alloy in an Enclosure with a Slanted Side Cooling Wall

This study considers the effect of a slanted side cooling wall that has varying inclination angles on the development of thermosolutal convection during the solidification of a super-eutectic aqueous ammonium chloride (NH4Cl-H2O) solution. The shadowgraph and particle image velocimetry techniques were employed to observe the flow development and measure the flow velocity during solidification. The transient temperature distribution within the test cell was also measured by type-T thermocouples. Experimental results reveal that a more slanted side cooling wall accelerated the “filling-box” process, thus it could cause more serious A-segregates and material defects in the solidified ingot.

Real-time monitoring of high-intensity focused ultrasound ablations with photoacoustic technique: Anin vitrostudy

The purpose of this study is to apply photoacoustic imaging (PAI) to monitor high intensity focused ultrasound (HIFU) process in real-time for accurate evaluation of thermal ablation outcomes. A photoacoustic (PA) imaging system was used to monitor HIFU ablation process in this study. Single-element, spherically focused ultrasonic transducers with center frequencies of 5 and 10 MHz were used to generate HIFU lesions and detect PA signals in beef kidney during HIFU treatments, respectively. A 25-μm diameter, T-type thermocouple was used to measure the temperature rise during the treatment as well. Thermal dose, which was used to indicate the coagulation of soft tissue, was calculated with the temperature measured by the thermocouple. Detected PA signals were then related to the coagulation of soft tissue through thermal dose calculations. In addition, PA signals from beef kidney coagulating under a constant temperature was obtained to show the changes of PA signals under a constant temperature during soft tissue coagulation. PA amplitude increases during the HIFU process and tends to have a saturation stage after the soft tissue is completely coagulated, which is indicated by a 240 or more TD(43) minutes. Also, a linear relation between the PA signal amplitude changes and temperature was observed when monitoring the sole effect of temperature. In addition, PA amplitude changes finally reached a constant value during soft tissue coagulation under a constant temperature. Through measurement of the photoacoustic signal, the authors demonstrated that monitoring thermal dose may be a more appropriate method in HIFU treatment than monitoring temperature.

Investigation of heat transfer and fluid flow behavior between straight and inclined fins in tall duct

This paper describes the flow behavior and flow patterns developed by straight and inclined fins and their affect on heat transfer characteristics. A detailed experimental investigation of the heat transfer and flow characteristics of finned surfaces was conducted for airflow (Re = 3824–12,747) in a tall duct corresponding to 200 mm height. In this experiment short rectangular fins were attached in 7 × 7 arrays to a heating surface and exposed to airflow. T-type thermocouples and an infrared camera with a 160 × 120-point In–Sb sensor were used to measure the wall temperature and to get the detailed heat transfer coefficient over the endwall and fin base. A thermal image and the iso-heat transfer coefficient contour give a complete picture of the heat transfer characteristics of the endwall surface. Smoke flow visualization reveals the longitudinal vortex generated by the inclined fins which significantly enhances the heat transfer in the inter-fin region and the fin surfaces. From the time averaged velocity profiles and spanwise velocity distributions a non-continuous curve caused by the detachment or reattachment of the flow was observed which confirms the existence of a longitudinal vortex in the case of inclined fins. But the horseshoe vortex appeared for both straight and inclined fins. The Nusselt number shows that heat transfer enhancement at a factor of more than three times than the finless duct is achieved for the inclined fins whereas straight fins could reach upto an enhancement of more than two times.

Overall Heat Transfer Coefficient of a Korean Traditional Building Envelope Estimated Through Heat Flux Measurement

The objective of this research is to determine overall heat transfer coefficients (U-value) of the exterior walls, floors, and roof of a Korean traditional residence via field measurement of transient heat flow and temperature difference across each envelope. The acquired U-values are compared with other existing values and those for current residential buildings. As for the field measurement, heat flux sensors and T-type thermocouple are attached on the internal and the external surfaces of each building component. Real-time measurement data are logged for three consecutive summer days. Acquired U-values agree well with other existing values for traditional building envelopes found in the open literature, but they are higher than U-values of current buildings. From this result one may conclude that the Korean traditional building has uncompetitive thermal performance compared with today's buildings. However, the energy simulation performed in this research shows that the traditional building can provide moderate cooling load competitive to current buildings. It comes mainly from the inherent characteristic of the traditional residence including relatively high infiltration rate and reduced solar radiation penetrating the windows.

ABSOLUTE THERMOELECTRIC POWER OF Pb–Sn ALLOYS

In this work, absolute thermoelectric power (ATP) of Pb , Sn , Pb -20 wt.% Sn , Pb -40 wt.% Sn , Pb -60 wt.% Sn , Pb -80 wt.% Sn are measured. Measurements are performed in a temperature gradient furnace from 20°C to 500°C, for both solid and liquid states. Temperatures are measured with T-type copper-constantan thermocouples, while voltage signal between copper electrodes of those thermocouples is recorded in order to calculate ATP of the sample metal.

Transient buoyancy-driven ventilation: Part 2. Modelling heat transfer

A new mathematical model for buoyancy-driven ventilation [Sandbach SD, Lane-Serff GF. Transient buoyancy-driven ventilation: Part 1. Modelling advection. Building and Environment, 2011] is modified to include heat transfer at the boundaries. Heat transfers at the ceiling and floor are included, using Newton’s law of cooling to model convective heat transfer between the air and the solid boundaries, Fourier’s law to model conductive heat transfer through the floor and ceiling, and a linear version of the Stefan–Boltzmann law to model radiative heat transfer from the ceiling to the floor. The effectiveness of the model was assessed using experimental results obtained in a full-scale test room. In these experiments, the vertical temperature stratification was measured using an array of T-type thermocouples. Speed measurements were obtained to estimate the ventilation flow rate (for displacement ventilation) and the velocity profile across the doorway (for doorway ventilation). Buoyancy was introduced using a twin-hob (∼2.35 kW) heat source, and in most cases a diffuse two-layer temperature stratification developed. The results from these experiments are compared with the model and existing adiabatic models. Our results indicate that the effect of heat transfer at the boundaries on the final stratification is significant and should not be ignored. Furthermore, direct comparisons between the measured and modelled results are in general very good.

Dry-out CHF correlation for R134a flow boiling in a horizontal helically-coiled tube

An experimental study was carried out to investigate the R134a dry-out critical heat flux (CHF) characteristics in a horizontal helically-coiled tube. The test section was heated uniformly by DC high-power source, and its geometrical parameters are the outer diameter of 10 mm, inner diameter of 8.4 mm, coil diameter of 300 mm, helical pitch of 75 mm and valid heated length of 1.89 m. The experimental parameters are the outlet pressures of 0.30–0.95 MPa, mass fluxes of 60–500 kg m −2 s −1, inlet qualities of −0.36–0.35 and heat fluxes of 7.0 × 10 3–5.0 × 10 4 W m −2. A method based on Agilent BenchLink Data Logger Pro was developed to determine the occurrence of CHF with a total of 68 T-type thermocouples (0.2 mm) set along the tube for accurate temperature measurement. The characteristics of wall temperatures and the parametric effect on dry-out CHF showed that temperature would jump abruptly at the point of CHF, which usually started to form at the front and offside (270° and 90°) of the outlet cross-section. The CHF values decrease nearly linearly with increasing inlet qualities, while they decrease more acutely with increasing critical qualities, especially under larger mass flux conditions. The mass flux has a positive effect on CHF enhancement, but the pressure has negative one. A new dimensionless correlation was developed to estimate dry-out CHF of R134a flow boiling in horizontal helically-coiled tubes under current experimental conditions and compared to calculated results from Bowring and Shah correlations.

Cooling Profile Following Prosthetic Preparation of 1-Piece Dental Implants

The aim of this study was to evaluate the effect of water irrigation on heat dissipation kinetics following abutment preparation of 1-piece dental implants. UNO 1-piece dental implants were mounted on Plexiglas apparatus clamping the implant at the collar. T-type thermocouple was attached to the first thread of the implant and recorded thermal changes at 100 millisecond intervals. Implants were prepared using highspeed dental turbine at 400,000 RPM with a coarse diamond bur. Once temperature reached 47 degrees C, abutment preparation was discontinued. Thirty implants were divided into 2 groups. Group A: Passive cooling without water irrigation. Group B: Cooling with turbine's water spray adjacent to the implant (30 mL/min). The following parameters were measured: T47 (time from peak temperature to 47 degrees C), T50%, T75% (time until the temperature amplitude decayed by 50% and 75%, respectively), dTemp50%/dt decay, and dTemp75%/dt decay (cooling rate measured at 50% and 75% of amplitude decay, respectively). Water spray irrigation significantly reduced T47 (1.37+/-0.29 seconds vs 19.97+/-3.06 seconds, P<0.0001), T50% (3.04+/-0.34 seconds vs 27.37+/-2.56 seconds, P<0.0001), and T75% (5.71+/-0.57 seconds vs 57.61+/-5.47 seconds, P<0.0001). Water spray irrigation also increased cooling capacity ninefold: dTemp50%/dt decay (4.14+/-0.61 degrees C/s vs 0.48+/-0.06 degrees C/s, P<0.0001), and dTemp50%/dt decay (1.70+/-0.29 degrees C/s vs 0.19+/-0.03 degrees C/s, P<0.0001). The continuous use of water spray adjacent to the abutment following the cessation of implant preparation might prove beneficial for rapid cooling of the implant.

Effect of Shear and Thermal Characteristics on Chemical Mechanical Polishing

Chemical mechanical polishing has been widely used to achieve global planarization of wafers. In this paper, an improved designed test rig is used to acquire the signals on chemical mechanical polishing. The shear force and temperature-rise are measured during chemical mechanical polishing process. The polishing temperature is measured by T-type thermocouples screwed behind the polishing interface of the carrier. The shear force is measured by a load transducer mounted on the lever and connected with the polishing head. The parameters including down force, rotation speed, particle size and volume flow rate of slurry are investigated. The experimental results provide a good index to end-point-detection. The theoretical simulation by the average lubrication equation coincides with the experimental results. This study contributes to the understanding of chemical mechanical polishing mechanism.

Thermal and Shear Characteristics Study of Various Mechanical Polishing Materials

Mechanical polishing is a primary technique for planarization of material surface in manufacture fabrication. Because the theoretical polishing mechanism is inadequately understood and because higher levels of polishing performance are desired, the investigation of experiment becomes more important. In this paper, a high precision polishing machine has established. With an improved design, a test rig can be easily used to simulate the mechanical polishing process and acquire the signals of polishing. The temperature-rise and shear force are measured for three different materials (i.e. copper, aluminum and silicon wafer) during mechanical polishing process. For the self-design test rig in the mechanical polishing process, its surface temperature is measured by T-type thermocouples screwed behind the polishing interface of the carrier. And shear force is measured by a load transducer mounted on the lever and connected with the polishing head. Furthermore, the roughness and particle size effects during polishing are demonstrated. The experimental results not only provide a good index to end-point-detection, but also increase the understanding of mechanical polishing process.

Quantification of in situ temperature measurements on a PBI-based high temperature PEMFC unit cell

The temperature is a very important operating parameter for all types of fuel cells. In the present work distributed in situ temperature measurements are presented on a polybenzimidazole based high temperature PEM fuel cell (HT-PEM). A total of 16 T-type thermocouples were embedded on both the anode and cathode flow plates. The purpose of this study is to investigate the feasibility of the proposed temperature characterization method and to identify the temperature distribution on an operating HT-PEM in various modes of operation, including a 700 h sensors durability test. The embedded sensors showed minimal influence on cell performance, this difference seen in performance is believed to be caused by different bipolar plate materials. The measurement method is suitable for obtaining detailed data for validation of computational models, moreover the results indicate that the method can be used as a degradation tool, as it is possible to locate areas exposed to degradation, both in plane and between the anode and cathode.

Heat Transfer Behavior of Molten Iron and Nickel during the First 0.2 Seconds of Solidification

This study aims at developing a fundamental understanding of the factors controlling strip casting. Heat transfer behavior of molten iron and nickel during the first 0.2 s of solidification has been clarified experimentally. The transient phenomena during solidification were successfully observed using a photo-sensor to measure cast surface temperatures and one wire thermocouple technique to measure the copper plate temperatures. T-type thermocouples were employed as one wire thermocouple method. The following results were obtained by this study.The molten metal ejected from a silica tube was kept as liquid state during the first 0.02 s along with undercooling after which recallescence took place. In addition, fluctuations in temperatures of the cast surface and inside the copper plate, that were co-related each other, were observed during recallescence. The copper plate temperature could catch up with the cast surface temperatures at the plate side thanks to one wire thermocouple technique where one constantan wire was set inside the copper plate. The peak values of heat fluxes were found to be higher with higher superheat of the molten metal. Almost constant values of 10000 (kW/m2) were obtained over 55°C while 3500 (kW/m2) at 40°C in superheat.According to the results comparing the temperatures of the cast surface and the copper plate, the peak point of the heat flux physically implies how long molten metal state is kept as for solidification of metal.

Forced Convective Cooling of Foils in a Repetitively Pulsed Electron-Beam Diode

Electron-beam (e-beam)-pumped high-power gas lasers require the use of a transmission window/foil to separate the vacuum diode from the laser cell. Under repetitive operation, the foil is subject to an e-beam heat load and would eventually fail without cooling. This paper investigates forced convective cooling of a foil in the main amplifier of the Electra KrF laser by flowing the laser gas around a closed loop. The experimental data were taken with one of the two diodes operating at 500 kV, 110 kA, a full-width at half-maximum of 140 ns, and with an external axial magnetic field of 0.14 T. Type-T thermocouples are used to measure the temperature of the foil under a variety of conditions including flow-velocity enhancement due to louver inserts, repetition rate, cathode configuration, gas composition, and height along the foil. A first-order model that considers cooling due to turbulent flow, as well as internal foil thermal conduction and radiation, reproduces the general trends observed in the data. The goal is to keep the temperature of a 25-mum-thick stainless steel foil below the tensile strength and long-term thermal fatigue limits when operating at 5 Hz. The data, in combination with the model, predict that this goal can be achieved by diverting the laser gas to flow at high velocity along the foil surface.

Heat Transfer Enhancement from a Surface Affixed with Rectangular Fins of Different Patterns and Arrangement in Duct Flow

Experiments were performed to investigate the heat transfer and fluid flow characteristics of a surface with arrays (7 × 7) of short rectangular plate fins of four different fin patterns — co-angular, zigzag, co-rotating, and co-counter rotating — for air flow (Re = 15,700-104,500) in a duct. T-type thermocouples and an infrared camera with a 160 × 120 point In−Sb sensor were used to measure the temperature and the detailed heat transfer at the end-wall along with the fin base. A flow behavior and its effect on heat transfer were observed from smoke flow visualization and oil titanium oxide film flow techniques. Horseshoe vortices were formed in front of the fins and longitudinal vortices were generated by the side top edges of the fins while behind the fins rolled-up vortices appeared in every fin pattern. Among the four patterns, the largest friction factor occurred for the co-rotating pattern at a smaller pitch ratio owing to strong flow interactions and combined vortex attack on the end wall and fin surface whereas the least friction developed for the co-angular pattern. The heat transfer result shows that the co-rotating pattern has the highest Nusselt number and the co-angular pattern has the least Nusselt number. Considering the thermal performance, the co-rotating pattern with a smaller pitch ratio is found to be the most recommended pattern as the heat transfer augmentation with the co-rotating pattern is more than three times the finless duct.

Thermal Modeling and Testing of a Nanosatellite's Avionics Board

A lumped-capacitance thermal model of an avionics board within the Miniature Autonomous Extravehicular Robotic Camera was developed to predict component temperatures. Subsequently, a thermal vacuum test was conducted to determine the board's measured thermophysical properties and validate temperature predictions. A functional prototype of the board was instrumented with 24 type-T thermocouples and placed in a thermal vacuum chamber. The board was then subjected to two power conditions while the temperature response was recorded. Analysis of the data shows that the measured values of the in-plane thermal conductivity are dominated by the dielectric material. Pretest analysis underpredicted the through-plane thermal conductivity by 63% and the in-plane thermal conductivity was overpredicted by approximately 740%. Additionally, the bulk emissivity of the board was determined using an average temperature of the thermocouples on the back side of the board. The emissivity calculated from measured temperature data, 0.95, was approximately 19% higher than the assumed emissivity used in pretest models, 0.80. Incorporation of the thermophysical properties based on measured data allows the updated model to predict temperatures of the LED board within an uncertainty of ±10°C and to capture the transient response of the board with considerable accuracy.

Combined effect of grid turbulence and unsteady wake on convective heat transfer around a heated cylinder

Experiments are conducted to investigate the effects of free stream turbulence and unsteady wake on convective heat transfer of a heated cylinder. To serve as a heater, a stainless steel needs to be pasted on exterior surface of the bakelite test cylinder. In order to determine the heat transfer coefficient, 17 T-type thermocouples are placed in unequal distance around the circumference at the mid-span of the test cylinder. The range of Reynolds number is 30,000 to 120,000. The results and contributions of this study display that the higher wake passing frequency produces more frequent velocity fluctuations, more broad velocity profiles, and stronger degree of turbulence intensity which are caused by the upstream wake generator and turbulence grid to enhance the heat transfer.

Nonlinear flow and heat transfer dynamics of impinging jets onto slightly-curved surfaces

The nonlinear flow and heat transfer characteristics for a slot-jet impinging on slightly-curved surfaces are experimentally studied here. The effects of curved surface geometry and jet Reynolds number on the jet velocity distribution and circumferential Nusselt numbers are examined. Two different slightly-curved surface geometries of convex and concave are used as target surfaces. The nozzle geometry is a rectangular slot, and the dimensionless nozzle-to-surface distance equals to L ∗ = 8. The constant heat fluxes are accordingly applied to the surfaces to obtain an impingement cooling by the air jet at ambient temperature. The measurements are made for the jet Reynolds numbers of Re = 8617, Re = 13 350 and Re = 15 415 for both curved surfaces. The velocity distributions of issuing jet from the nozzle exit to the target surface are obtained by a highly sensitive hot-wire anemometer. The T-type thermocouples are used to measure local temperatures of both the air jet and the plates. Two-dimensional velocity measurements show that the surfaces are remained out of the potential core region for all Re tested here. New correlations for local, stagnation point, and average Nusselt numbers as a function of jet Reynolds number and dimensionless circumferential distance are reported. The correlations reveal that the impinging cooling rate is higher with the concave surface and increase with increasing Re.

Fluctuating temperature measurement by a fine-wire thermocouple probe: influences of physical properties and insulation coating on the frequency response

Theoretical analysis of the frequency response of a fine-wire thermocouple probe has been further developed to investigate influences of the difference in physical properties between the two wires composing a butt-welded fine-wire thermocouple. The solution obtained demonstrates complex behaviour of the frequency response of the copper–constantan (type-T) thermocouple whose physical properties differ greatly between the two constitutive wires. It was also shown that, in an air flow, the frequency response is almost uniform in the cross-section of the thermocouple wire, but, in a water flow, it becomes remarkably nonuniform. The present theoretical analysis provides useful information for improving the reliability of fluctuating temperature measurement in high-temperature turbulent flows.

Development and testing of a heat–cool methodology to automate oyster shucking

A heat/cool methodology was developed to facilitate oyster shucking. Eastern oysters Crassostrea virginica from several locations were used. Two methods were designed to shuck oysters, which incorporated various heat–cool regimes. The first was a combination of low-pressure steam and cryogenic CO 2, the second a combination of steam and cooling, either from cryogenic N 2 or ice water. The oysters were instrumented with T-type thermocouples connected to a datalogger to monitor and record process temperatures. Methods also were developed to quantify meat detachment, shelf-life and textural changes. The methods developed allowed for the measurement and optimization of the shucking process. Advantages of the steam–ice water combination include availability of facilities and low cost. Additionally, under selected regimes, meat quality was similar to that of raw oysters, while some reduction in microbial activity was recorded. Results indicated quantifiable methods, which yielded oyster meat detachments in excess of 85%.

A Fast-Response Thermopile Photodetector Fabricated by a Photolithography Technique Combined with Laser-Beam Machining

A micrometer-scale thermopile formed on Si substrate using a photolithography technique combined with laser-beam machining is described. Initially, the surface of an 11-mm-square and 0.3-mm-thick Si substrate was oxidized to grow a SiO2 thin-film. A 300-μm-long, 100-μm-wide and 0.5-μm-thick SiO2 air bridge was then formed on the Si substrate using a photolithography technique. Next, copper and constantan were evaporated in layers on the middle of the air bridge. This evaporated thin film functioned as a type-T thermocouple. Then, in order to improve the sensitivity of the thermocouple, three of the type-T thin-film thermocouples were shaped by cutting the evaporated film into three regions using a laser-beam machining technique. Finally, the thermopile was completed by connecting the three thermocouples in series, locating their hot junctions on the center of the air bridge and cold junctions on the pad areas used as electrodes. Because the heat capacity and the heat dissipation of the hot junction areas differ from those of the cold junction area, a temperature difference occurs between the hot and cold junctions when the thermopile receives radiation. This temperature difference generates a thermo-electromotive force between the cold and hot junctions, which is a measure of the intensity of the incident radiation. Due to a small heat capacity combined with a relatively large radiation reception area, the time-constant of this type of thermopile for light-illumination was found to be less than 1 ms, which was more than ten times faster than that of conventional thermopiles presently on the market.