Development of a Transparent Heater to Measure Surface Temperature Fluctuations Under Spray Cooling Conditions

2008 ◽  
Vol 130 (11) ◽  
Author(s):  
A. R. Griffin ◽  
A. Vijayakumar ◽  
R.-H. Chen ◽  
K. B. Sundaram ◽  
L. C. Chow
Keyword(s):  
Surface Temperature ◽  
Indium Tin Oxide ◽  
High Speed ◽  
Quartz Substrate ◽  
Sampling Rate ◽  
Temperature Fluctuations ◽  
Spray Cooling ◽  
Fused Silica ◽  
Measure Surface Temperature ◽  
Lift Off

A heater designed to monitor surface temperature fluctuations during pool boiling and spray cooling experiments while the bubbles are simultaneously being observed has been fabricated and tested. The heat source was a transparent indium tin oxide (ITO) layer commercially deposited on a fused quartz substrate. Four copper-nickel thin film thermocouples (TFTCs) on the heater surface measured the surface temperature, while a thin layer of sapphire or synthetic fused silica provided electrical insulation between the TFTCs and the ITO. The TFTCs were microfabricated using the lift-off process to deposit the nickel and copper metal films. The TFTC elements were 50μm wide and overlapped to form a 25×25μm2 junction. A DAQ program recorded the TFTC voltages at a sampling rate of 50kHz and sent a trigger to a high-speed camera to synchronize bubble images with the surface temperature data. As the bubbles and their contact rings grew over the TFTC junction, correlations between bubble behavior and surface temperature changes were demonstrated.

Development of a Transparent Heater to Measure Surface Temperature Fluctuations for Pool Boiling and Spray Cooling

2007 ◽  
Author(s):  
Alison R. Griffin ◽  
Arun Vijayakumar ◽  
Ruey-Hung Chen ◽  
Kalpathy B. Sundaram ◽  
Louis C. Chow
Keyword(s):  
Surface Temperature ◽  
Indium Tin Oxide ◽  
High Speed ◽  
Pool Boiling ◽  
Sampling Rate ◽  
Temperature Fluctuations ◽  
Spray Cooling ◽  
Fused Silica ◽  
Outer Diameter ◽  
Measure Surface Temperature

A heater designed to monitor surface temperature fluctuations during pool boiling and spray cooling experiments while the bubbles are simultaneously being observed has been fabricated and tested. The heat source was a transparent indium tin oxide (ITO) layer commercially deposited on a fused quartz substrate. Four copper-nickel thin film thermocouples (TFTCs) on the heater surface measured the surface temperature, while a thin layer of sapphire or synthetic fused silica provided electrical insulation between the TFTCs and the ITO. The TFTCs were micro-fabricated using the liftoff process to deposit the nickel and copper metal films. The TFTC elements were 50 μm wide and overlapped to form a 25 μm by 25 μm junction. TFTC voltages were recorded by a DAQ at a sampling rate of 50 kHz. A high-speed CCD camera recorded bubble images from below the heater at 2000 frames/second. From these images, the bubble outer diameter and contact ring diameter were clearly visible. A trigger sent to the camera by the DAQ program synchronized the bubble images and the surface temperature data. As the bubbles and their contact rings grew over the TFTC junction, correlations between bubble behavior and surface temperature changes were made. The 1–2°C temperature drops occurred as the contact ring moved over the TFTC junction during bubble growth and as the contact ring moved back over the TFTC junction during bubble departure.

Study of Flow Boiling Characteristics of a Microchannel Using High Speed Visualization

2013 ◽  
Vol 135 (8) ◽  
Author(s):  
Rashid Ali ◽  
Björn Palm ◽  
Claudi Martin-Callizo ◽  
Mohammad H. Maqbool
Keyword(s):  
Heat Flux ◽  
Flow Pattern ◽  
Indium Tin Oxide ◽  
High Speed ◽  
Liquid Velocity ◽  
Flow Boiling ◽  
Fused Silica ◽  
Internal Diameter ◽  
Electrically Conductive ◽  
Heated Length

This paper presents the visualization results obtained for an experimental study of R134a during flow boiling in a horizontal microchannel. The microchannel used was a fused silica tube having an internal diameter of 781 μm, a heated length of 191 mm, and was coated with a thin, transparent, and electrically conductive layer of indium-tin-oxide (ITO) on the outer surface. The operating parameters during the experiments were: mass flux 100–400 kg/m2 s, heat flux 5–45 kW/m2, saturation temperatures 25 and 30 °C, corresponding to saturation pressures of 6.65 bar and 7.70 bar and reduced pressures of 0.163 and 0.189, respectively. A high speed camera with a close up lens was used to capture the flow patterns that evolved along the channel. Flow pattern maps are presented in terms of the superficial gas and liquid velocity and in terms of the Reynolds number and vapor quality plots. The results are compared with some flow pattern maps for conventional and micro scale channels available in the literature. Rigorous boiling and increased coalescence rates were observed with an increase in the heat flux.

Experimental Study of Nanofluids for Droplet Cooling Applications Using Temperature Microsensors

2006 ◽  
Author(s):  
John E. Guinn ◽  
Debjyoti Banerjee
Keyword(s):  
Experimental Study ◽  
Heat Flux ◽  
Surface Temperature ◽  
Heated Surface ◽  
Temperature Fluctuations ◽  
Spray Cooling ◽  
Nano Particles ◽  
Test Fluid ◽  
Spray Parameters ◽  
Nano Fluid

The use of nano-fluids in droplet cooling (boiling) was explored parametrically in this experimental study. The experimental parameters are: nanofluid composition, superheat, liquid subcooling, and spray parameters (nozzle diameter, injection distance, size of droplets, injection pressure, mass flow rate, etc.). Two test fluids were used in the experiments: de-ionized (DI) water and nanofluid. The nano-fluid consists of silica nano-particles with a nominal diameter of 10nm dissolved in water at 2% concentration by weight. An experimental apparatus was fabricated to measure the surface temperature fluctuations during spray cooling of a heated surface. An array of microthermocouples (Thin Film Thermocouples or "TFT") was micro-fabricated on a heated surface to measure the surface temperature fluctuations during spray cooling. The TFT are capable of measuring temperature fluctuations up to a speed of 100 MHz. In the experiments, the exit of the single droplet spray was set a distance of 10 mm away from the surface and was aligned with the location of the TFT array. The spray was produced by pumping test fluid using a syringe pump into a traversing spray head. Silicon wafers with surface micromachined TFT array were clamped on the top of the heater apparatus for measuring temperature changes on the surface of the heater. Wire bead K-Type thermocouples were embedded in the heater apparatus and were used to measure heat flux. The transient temperature data from the TFT were recorded by a data acquisition system connected to a computer. The nano-fluid spray was found to cause fouling of the heater surface due to precipitation of the constituent nano-particles during boiling. This caused the overall heat flux to decrease drastically when compared to spray cooling using water. The nano-fluid spray was found to enhance heat flux by 300% compared to the base heat flux without the spray.

scholarly journals Acute Effects of Handheld Loading on Standing Broad Jump in Youth Athletes

2021 ◽  
Vol 18 (9) ◽  
pp. 5046
Author(s):  
Wei-Hsun Tai ◽  
Ray-Hsien Tang ◽  
Chen-Fu Huang ◽  
Shin-Liang Lo ◽  
Yu-Chi Sung ◽  
...  
Keyword(s):  
High Speed ◽  
Center Of Mass ◽  
Reaction Force ◽  
Sampling Rate ◽  
Random Order ◽  
Horizontal Distance ◽  
Acute Effects ◽  
Vertical Ground Reaction Force ◽  
Strength And Conditioning ◽  
Peak Knee

The study aimed to investigate the acute effects of handheld loading on standing broad jump (SBJ) performance and biomechanics. Fifteen youth male athletes (mean age: 14.7 ± 0.9 years; body mass: 59.3 ± 8.0 kg; height: 1.73 ± 0.07 m) volunteered to participate in the study. Participants were assigned to perform SBJ with and without 4 kg dumbbells in a random order. Kinematic and kinetic data were collected using 10 infrared high-speed motion-capture cameras at a 250 Hz sampling rate and two force platforms at a 1000 Hz sampling rate. A paired t-test was applied to all variables to determine the significance between loading and unloading SBJs. Horizontal distance (p < 0.001), take-off distance (p = 0.001), landing distance (p < 0.001), horizontal velocity of center of mass (CoM; p < 0.001), push time (p < 0.001), vertical impulse (p = 0.003), and peak horizontal and vertical ground reaction force (GRF; p < 0.001, p = 0.017) were significantly greater in loading SBJ than in unloading SBJ. The take-off vertical velocity of CoM (p = 0.001), take-off angle (p < 0.001), peak knee and hip velocity (p < 0.001, p = 0.007), peak ankle and hip moment (p = 0.006, p = 0.011), and peak hip power (p = 0.014) were significantly greater in unloading SBJ than in loading SBJ. Conclusions: Acute enhancement in SBJ performance was observed with handheld loading. The present findings contribute to the understanding of biomechanical differences in SBJ performance with handheld loading and are highly applicable to strength and conditioning training for athletes.

scholarly journals Study on the effect of Weber Number to heat transfer of multiple droplets on hot stainless steel surface

2018 ◽  
Vol 154 ◽  
pp. 01114 ◽  
Author(s):  
Aria Riswanda ◽  
Indro Pranoto ◽  
Deendarlianto ◽  
Indarto ◽  
Teguh Wibowo
Keyword(s):  
Stainless Steel ◽  
Surface Temperature ◽  
Weber Number ◽  
Steel Surface ◽  
Cooling System ◽  
Spray Cooling ◽  
Stainless Steel Surface ◽  
Temperature Decrease ◽  
Evaporation Time ◽  
Decrease Rate

Multiple droplets are drops of water that continuously dropped onto a surface. Spray cooling is an application of the use of droplet on a cooling system. Spray cooling is usually used in a cooling system of electronic devices, and material quenching. In this study, correlations between Weber number and surface temperature decrease rate during multiple droplets impingement are investigated and analyzed. Visualization process is used to help determine the evaporation time of droplets impingement by using high speed camera. Induction stove is used to maintain a stainless steel surface temperature at 120°C, 140°C, and 160°C. The Weber number was varied at 15, and 52.5 to simulate low and medium Weber number. The result of this study shows that increase in Weber number does not increase the temperature decrease rate noticeably. Whereas the Weber number decrease the time required for surface temperature to reach its lowest surface temperature. It was also found that for low and medium Weber number, Weber number affect the evaporation time of multiple droplets after impingement.

scholarly journals Operating temperatures of oil-lubricated medium-speed gears: Numerical models and experimental results

2003 ◽  
Vol 217 (2) ◽  
pp. 87-106 ◽  
Author(s):  
H Long ◽  
A A Lord ◽  
D T Gethin ◽  
B J Roylance
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Rotational Speed ◽  
High Speed ◽  
Applied Load ◽  
Frictional Heat ◽  
Transfer Coefficients ◽  
Gear Teeth ◽  
Heat Transfer Coefficients

This paper investigates the effects of gear geometry, rotational speed and applied load, as well as lubrication conditions on surface temperature of high-speed gear teeth. The analytical approach and procedure for estimating frictional heat flux and heat transfer coefficients of gear teeth in high-speed operational conditions was developed and accounts for the effect of oil mist as a cooling medium. Numerical simulations of tooth temperature based on finite element analysis were established to investigate temperature distributions and variations over a range of applied load and rotational speed, which compared well with experimental measurements. A sensitivity analysis of surface temperature to gear configuration, frictional heat flux, heat transfer coefficients, and oil and ambient temperatures was conducted and the major parameters influencing surface temperature were evaluated.

Characterization of Fouled Flat Sheet Membranes by Infrared Thermography

2014 ◽  
Author(s):  
Kennethrex O. Ndukaife ◽  
George Agbai Nnanna
Keyword(s):  
Surface Temperature ◽  
Infrared Thermography ◽  
Spectral Power ◽  
Membrane Surface ◽  
Infrared Camera ◽  
Feed Solution ◽  
Feed Concentration ◽  
Ir Camera ◽  
Measure Surface Temperature

An Infrared thermography (IRT) technique for characterization of fouling on membrane surface has been developed. The emitted spectral power from the fouled membrane is a function of emissivity and surface morphology. In this work, a FLIR A320 IR camera was used to measure surface temperature and emissivity. The surface temperature and the corresponding emissivity value of various areas on the fouled membrane surface is measured by the infrared camera and recorded alongside its thermogram. Different fouling experiments were performed using different concentrations of aluminum oxide nanoparticle mixed with deionized water as feed solution (333 ppm, 1833 ppm and 3333 ppm) so as to investigate the effect of feed concentration on the degree of fouling and thus its effect on the emissivity values measured on the membrane surfaces. Surface plots in 3D and Line plots are obtained for the measured emissivity values and thickness of the fouling deposit on the membrane surface respectively. The results indicate that the IRT technique is sensitive to changes that occur on the membrane surface due to deposition of contaminants on the membrane surface and that emissivity is a function of temperature, surface roughness and thickness of the specimen under investigation.

scholarly journals Propellant Combustion Wave Studies by Embedded Thermocouple and Imaging Method at Ambient Pressure

2020 ◽  
Author(s):  
Rakesh Kumar Kalal ◽  
Himanshu Shekhar ◽  
Prashant Sudhir Alegaonkar ◽  
Shrikant Pande
Keyword(s):  
Surface Temperature ◽  
High Speed ◽  
Ambient Pressure ◽  
Combustion Mechanism ◽  
Imaging Method ◽  
Flame Zone ◽  
Sem Images ◽  
Propellant Combustion ◽  
Double Base ◽  
Zone Temperature

This paper discusses the method for propellant combustion studies with embedded thermocouple and imaging method at ambient pressure. In this study, three different propellant compositions are experimentally evaluated for surface temperature, flame zone temperature with embedded thermocouple, and reaction zone thickness with high-speed imaging of propellant during combustion at ambient pressure. Preheat zone and flame zone temperature profiles are recorded with time and surface temperature is determined with available models. Observation of these experiments gives the difference between combustion mechanism of double-base propellant with diethylene glycol dinitrate (DEGDN) and 2,4-dinitrotoluene (DNT), composite propellant (CP) and CP with energetic binder. Scanning electron microscope (SEM) images analysis for pristine and quenched sample is also presented.

Rotordynamic Performance of a Shaft With Large Overhung Mass Supported by Foil Bearings

2016 ◽  
Vol 139 (4) ◽  
Author(s):  
Nguyen LaTray ◽  
Daejong Kim
Keyword(s):  
High Speed ◽  
Foil Bearings ◽  
Speed Test ◽  
Foil Bearing ◽  
Stable Conditions ◽  
Bending Mode ◽  
Mode Vibration ◽  
Lift Off ◽  
Compact Design ◽  
Bearing System

This work presents the theoretical and experimental rotordynamic evaluations of a rotor–air foil bearing (AFB) system supporting a large overhung mass for high-speed application. The proposed system highlights the compact design of a single shaft rotor configuration with turbomachine components arranged on one side of the bearing span. In this work, low-speed tests up to 45 krpm are performed to measure lift-off speed and to check bearing manufacturing quality. Rotordynamic performance at high speeds is evaluated both analytically and experimentally. In the analytical approach, simulated imbalance responses are studied using both rigid and flexible shaft models with bearing forces calculated from the transient Reynolds equation along with the rotor motion. The simulation predicts that the system experiences small synchronous rigid mode vibration at 20 krpm and bending mode at 200 krpm. A high-speed test rig is designed to experimentally evaluate the rotor–air foil bearing system. The high-speed tests are operated up to 160 krpm. The vibration spectrum indicates that the rotor–air foil bearing system operates under stable conditions. The experimental waterfall plots also show very small subsynchronous vibrations with frequency locked to the system natural frequency. Overall, this work demonstrates potential capability of the air foil bearings in supporting a shaft with a large overhung mass at high speed.

THE QNDE USING IMAGE PROCESSING OF THE MAGNETIC CAMERA

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4625-4630 ◽  
Author(s):  
JINYI LEE ◽  
JISEONG HWANG ◽  
SEHO CHOI
Keyword(s):  
Image Processing ◽  
High Speed ◽  
Magnetic Hysteresis ◽  
High Sensitivity ◽  
Magnetic Sensors ◽  
Second Derivatives ◽  
Crack Volume ◽  
Lift Off ◽  
Magnetic Camera ◽  
Derivatives Of

A scan type magnetic camera was proposed to satisfy the following demands: to obtain high speed quantitative magnetic flux leakage (MFL) distribution with homogeneous lift-off by using 2-dimensionally arrayed high sensitivity magnetic sensors; to concentrate the MFL; and to ignore the residual magnetization and magnetic hysteresis by using a magnetic fluid lens. The magnetic field distribution (MFD) image obtained by using the scan type magnetic camera is inclined to the scanning direction (x-direction) because of the poles of the magnetizer. Also, the image shows a homogeneous trend relative to the x-direction, but there are small waves in the distribution in the sensor arraying direction (y-direction). The crack information in the MFD image can be extracted using image processing. The first and second derivatives of both x and y are used in this processing. These are "1st derivative of x, ∂B/∂x", "1st derivative of y, ∂B/∂y", "2nd derivative of x, ∂2B/∂x2", "2nd derivative of y, ∂2B/∂y2", and "2nd derivative of x and y, ∂2B/∂x∂y". The ∂B/∂x distribution shows the existence of the crack. Also, the crack volume can be evaluated quantitatively, regardless of the crack direction, by using ∂B/∂x and a cross type magnetic coil.

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