Design, Fabrication and Calibration of Heat Transfer Gauges for Transient Measurement

2010 ◽  
Author(s):  
Rakesh Kumar ◽  
Niranjan Sahoo ◽  
Vinayak Kulkarni
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
High Speed ◽  
Internal Combustion Engines ◽  
Fast Response ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Temperature History ◽  
Heating Rates ◽  
Experimental Conditions

Transient measurements of surface heating rates are very important in many applications in the field of internal combustion engines, gas turbine engines, fluidized beds and high-speed flow environments. In most surface heat transfer mapping, very fast response sensors are used for dynamic temperature measurements in the flow. The surface heat fluxes are then estimated from the temperature history, analytically/numerically by various heat transfers modeling. Thin film gauges and thermocouples are most cost effective temperature sensors for dynamic measurements because the response time of these sensors are in the range of microseconds. The production of heat transfer gauges in the laboratory has always been an art rather than a method of manufacture. The present work is aimed at design and fabrication of fast response thermocouples and thin film gauges (TFG) in the laboratory. Three types of thermocouples have been fabricated (E-type, T-type and K-type) whereas platinum film is deposited on the insulating substrate (Pyrex and Macor) for thin film heat transfer gauge. Both thermocouples and thin film gauges are calibrated under same experimental conditions.

scholarly journals Dynamic calibration of temperature sensors from light rays for transient measurement

2019 ◽  
Vol 23 (3 Part B) ◽  
pp. 1901-1910
Author(s):  
Rishikesh Goswami ◽  
Rakesh Kumar
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Flux ◽  
Short Duration ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Transient Temperature ◽  
Element Analysis ◽  
Radiation Mode

Measurement of transient heat fluxes in the applications involving very short duration of a heating environment which has been promised for the candidate by measurement of surface heating rates with thin film gauges (TFG). They are basically resistance temperature detectors having to measure in a very short duration of time. In the present study, a platinum based TFG has been fabricated and dynamically calibrated (radiation based) in the laboratory with a view to assessing the performance of platinum thin film gauges (PTFG) in the dynamic environment. These examinations are focusing to explore the probability of using TFG for small duration transient measurements with pure radiation mode of heat transfer. Radiation based heat flux is applied on the gauge by using the halogen bulb in a square box and its response is obtained through measured transient temperature. Subsequently, the surface heat fluxes are estimated by using radiation-based heat transfer. The purpose of this work is to statically calibrate each handmade heat transfer gauges by using quartz as substrate material deposited on platinum paste. This experiment has been carried out by oil bath based experimental technique. The similar experimental environment is also studied to observe the transient temperature response by using numerical simulation. The experiments are carried out by exposing the platinum TFG to various known step heat load of known input wattage, for the duration of 10 seconds. Then, the voltage signals are recorded due to change in temperature of air-flow past the TFG. The numerical simulation (ANSYS-Fluent v. 14.5) is performed in the similar experimental environmental conditions, for the same heating loads. Experimentally recorded temperature signals from the gauges are compared with simulated temperature histories obtained through finite element analysis. Cubic spline methods of the 1-D heat conduction equation are used to predict surface heat flux and compared with input heat loads. The presently developed calibration set-up is seen to very useful for radiation-based measurements of TFG.

Laser Based Calibration Technique of Thin Film Gauges for Short Duration Transient Measurements

2011 ◽  
Vol 3 (4) ◽  
Author(s):  
Rakesh Kumar ◽  
Niranjan Sahoo ◽  
Vinayak Kulkarni ◽  
Anugrah Singh
Keyword(s):  
Thin Film ◽  
High Speed ◽  
Internal Combustion Engines ◽  
Cooling System ◽  
Cost Effective ◽  
Analytical Models ◽  
Temperature History ◽  
Transient Temperature ◽  
Convective Heating ◽  
Thin Film Sensors

Surface temperature history and determination of convective heating rate are the important activity in many research programs for devising an effective cooling system in internal combustion engines or for typical high speed aerodynamic reentry vehicles. Thin film sensors have high response time (∼ few microseconds) and are invariantly used for these applications due to their precision measurement. Moreover, they can be fabricated in-house and thus cost effective. Present investigations are focused on the fabrication of such sensors and establishment of an experimental setup for calibration. Thin film sensors are prepared in-house by platinum ink mounted on an insulated substrate (Pyrex). Experiments are carried out by applying step heat load on the thin film sensor using laser light of known wattage. Recorded transient temperature data are processed for estimation of laser wattage using numerical and analytical models. For the known heating load, temperature signal is also predicted using one-dimensional transient heat conduction solver using ansys. Encouraging agreement of these predictions has demonstrated the success of the designed calibration set up and cost-effective means of in-house fabrication of thin film sensors.

Effects of Rotation on Blade Surface Heat Transfer: An Experimental Investigation

1997 ◽  
Author(s):  
Roger W. Moss ◽  
Roger W. Ainsworth ◽  
Tom Garside
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Experimental Investigation ◽  
Turbine Blade ◽  
Time History ◽  
Surface Heat ◽  
Blade Surface ◽  
Surface Heat Transfer ◽  
Effects Of Rotation ◽  
Wake Passing

Measurements of turbine blade surface heat transfer in a transient rotor facility are compared with predictions and equivalent cascade data. The rotating measurements involved both forwards and reverse rotation (wake free) experiments. The use of thin-film gauges in the Oxford Rotor Facility provides both time-mean heat transfer levels and the unsteady time history. The time-mean level is not significantly affected by turbulence in the wake; this contrasts with the cascade response to freestream turbulence and simulated wake passing. Heat transfer predictions show the extent to which such phenomena are successfully modelled by a time-steady code. The accurate prediction of transition is seen to be crucial if useful predictions are to be obtained.

Stall Inception in a High Speed Centrifugal Compressor During Speed Transients

2017 ◽  
Author(s):  
Fangyuan Lou ◽  
John C. Fabian ◽  
Nicole L. Key
Keyword(s):  
Heat Transfer ◽  
Centrifugal Compressor ◽  
High Speed ◽  
Flow Instability ◽  
Leading Edge ◽  
Fast Response ◽  
Rotating Stall ◽  
Transient Performance ◽  
Stall Inception ◽  
Pressure Transducers

The inception and evolution of rotating stall in a high-speed centrifugal compressor are characterized during speed transients. Experiments were performed in the Single Stage Centrifugal Compressor (SSCC) facility at Purdue University and include speed transients from sub-idle to full speed at different throttle settings while collecting transient performance data. Results show a substantial difference in the compressor transient performance for accelerations versus decelerations. This difference is associated with the heat transfer between the flow and the hardware. The heat transfer from the hardware to the flow during the decelerations locates the compressor operating condition closer to the surge line and results in a significant reduction in surge margin during decelerations. Additionally, data were acquired from fast-response pressure transducers along the impeller shroud, in the vaneless space, and along the diffuser passages. Two different patterns of flow instabilities, including mild surge and short-length-scale rotating stall, are observed during the decelerations. The instability starts with a small pressure perturbation at the impeller leading edge and quickly develops into a single-lobe rotating stall burst. The stall cell propagates in the direction opposite of impeller rotation at approximately one third of the rotor speed. The rotating stall bursts are observed in both the impeller and diffuser, with the largest magnitudes near the diffuser throat. Furthermore, the flow instability develops into a continuous high frequency stall and remains in the fully developed stall condition.

Heat Transfer and Pressure Drop for Flow Boiling of Water in Narrow Vertical Rectangular Channels

2003 ◽  
Author(s):  
Jianyun Shuai ◽  
Rudi Kulenovic ◽  
Manfred Groll
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Boiling ◽  
Bubbly Flow ◽  
High Heat ◽  
Flow Patterns ◽  
Industrial Applications ◽  
Heat Fluxes ◽  
Experimental Conditions ◽  
Rectangular Channels

Flow boiling in small-sized channels attracted extensive investigations in the past two decades due to special requirements for transfer of high heat fluxes from narrow spaces in various industrial applications. Experiments on various aspects of flow boiling in narrow channels were carried out and theoretical attempts were undertaken. But these investigations showed large differences, e.g. up till now the knowledge on the development of flow patterns in small non-circular flow passages is very limited. This paper deals with investigations on flow boiling of water in two rectangular channels with dimensions (width×depth) 2.0×4.0 mm2 and 0.5×2.0 mm2 (corresponding hydraulic diameters are 2.67 mm and 0.8 mm). The pressure at the test section exit is atmospheric. For steady-state experimental conditions the effects of heat flux, mass flux and inlet subcooling on the boiling heat transfer coefficient and the pressure drop are investigated. Flow patterns and the transition of flow patterns along the channel axis are visualized and documented with a video-camera. Bubbly flow, slug flow and annular flow are distinguished in both channels. Preliminary flow pattern maps are generated.

Incipient Flow Boiling in a Vertical Channel With a Wavy Wall

2010 ◽  
Author(s):  
T. Netz ◽  
R. Shalem ◽  
J. Aharon ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
High Speed ◽  
Flow Boiling ◽  
Heated Surface ◽  
Vertical Channel ◽  
Infrared Camera ◽  
Heat Fluxes ◽  
Heated Wall ◽  
Boiling Incipience

In the present study, incipient flow boiling of water is studied experimentally in a square-cross-section vertical channel. Water, preheated to 60–80 degrees Celsius, flows upwards. The channel has an electrically heated wall, where the heat fluxes can be as high as above one megawatt per square meter. The experiment is repeated for different water flow rates, and the maximum Reynolds number reached in the present study is 27,300. Boiling is observed and recorded using a high-speed digital video camera. The temperature field on the heated surface is measured with an infrared camera and a software is used to obtain quantitative temperature data. Thus, the recorded boiling images are analyzed in conjunction with the detailed temperature field. The dependence of incipient boiling on the flow and heat transfer parameters is established. For a flat wall, the results for various velocities and subcooling conditions agree well with the existing literature. Furthermore, three different wavy heated surfaces are explored, having the same pitch of 4mm but different amplitudes of 0.25mm, 0.5mm and 0.75mm. The effect of surface waviness on single-phase heat transfer and boiling incipience is shown. The differences in boiling incipience on various surfaces are elucidated, and the effect of wave amplitude on the results is discussed.

Modeling and Experimental Validation of a Reed Check Valve for Hydraulic Applications

2016 ◽  
Author(s):  
Anthony L. Knutson ◽  
James D. Van de Ven
Keyword(s):  
Internal Combustion Engines ◽  
Check Valve ◽  
Maximum Error ◽  
Fast Response ◽  
Single Element ◽  
Hydraulic Systems ◽  
Test Bed ◽  
Experimental Conditions ◽  
Wide Range ◽  
Reed Valve

Reed valves are a type of check valve commonly found in a wide range of applications including air compressors, internal combustion engines, and even the human heart. While reed valves have been studied extensively in these applications, published research on the modeling and application of reed valves in hydraulic systems is severely lacking. Because the spring and mass components of a reed valve are contained in a single element, it is light and compact compared to traditional disc, poppet, or ball style check valves. These advantages make reed valves promising for use in high frequency applications such as piston pumps, switch-mode hydraulics, and digital hydraulics. Furthermore, the small size and fast response of reed valves provide an opportunity to design pumps capable of operating at higher speeds and with lower dead volumes, thus increasing efficiency and power density. In this paper, a modeling technique for reed valves is presented and validated in a hydraulic piston pump test bed. Excellent agreement between modeled and experimentally measured reed valve opening is demonstrated. Across the range of experimental conditions, the model predicts the pump delivery with an error typically less than 1% with a maximum error of 2.2%.

Nucleate Boiling From Micro-Machined Surfaces

2003 ◽  
Author(s):  
Adrian M. Holland ◽  
Colin P. Garner
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Imaging System ◽  
Laser System ◽  
Ccd Camera ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Frame Rate ◽  
High Speed Imaging ◽  
Machined Surfaces

This paper discusses the production and use of laser-machined surfaces that provide enhanced nucleate boiling and heat transfer characteristics. The surface features of heated plates are known to have a significant effect on nucleate boiling heat transfer and bubble growth dynamics. Nucleate boiling starts from discrete bubbles that form on surface imperfections, such as cavities or scratches. The gas or vapours trapped in these imperfections serve as nuclei for the bubbles. After inception, the bubbles grow to a certain size and depart from the surface. In this work, special heated surfaces were manufactured by laser machining cavities into polished aluminium plates. This was accomplished with a Nd:YAG laser system, which allowed drilling of cavities of a known diameter. The size range of cavities was 20 to 250 micrometers. The resulting nucleate pool boiling was analysed using a novel high-speed imaging system comprising an infrared laser and high resolution CCD camera. This system was operated up to a 2 kHz frame rate and digital image processing allowed bubbles to be analysed statistically in terms of departure diameter, departure frequency, growth rate, shape and velocity. Data was obtained for heat fluxes up to 60 kW.m−2. Bubble measurements were obtained working with water at atmospheric pressure. The surface cavity diameters were selected to control the temperature at which vapour bubbles started to grow on the surface. The selected size and spacing of the cavities was also explored to provide optimal heat transfer.

Subcooled Flow Boiling on Micro-Porous Structured Copper Surface in a Vertical Mini-Gap Channel

2019 ◽  
Author(s):  
Junye Li ◽  
Kan Zhou ◽  
Wei Li
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Flow Boiling ◽  
Copper Surface ◽  
Heat Fluxes ◽  
High Speed Flow ◽  
Subcooled Flow Boiling ◽  
Mass Fluxes ◽  
Speed Flow ◽  
Subcooled Flow

Abstract An experimental investigation of subcooled flow boiling in a large width-to-height-ratio, one-sided heating rectangular mini-gap channel was conducted with deionized water as the working fluid. The super-hydrophobicity micro-porous structured copper surface was utilized in the experiments. High speed flow visualization was conducted to illustrate the effects of heat flux and mass rate on the heat transfer coefficient and flow pattern on the surfaces. The mass fluxes were in the range of 200–500 kg/m2s, the wall heat fluxes were spanned from 40–400 kW/m2. With increments of imposed heat flux, the slopes of boiling curves for superhydrophobic micro-porous copper surfaces increased rapidly, indicating the Onset of Nucleate Boiling. Heat transfer characteristics were discussed with variation of heat fluxes and mass fluxes, the trends of which were analyzed with the aid of high speed flow visualization.

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