Design and Calibration of a Local Heat-Flux Measurement System for Unsteady Flows

1989 ◽  
Vol 111 (2) ◽  
pp. 552-557 ◽  
Author(s):  
D. S. Campbell ◽  
M. Gundappa ◽  
T. E. Diller
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Heat Flux ◽  
Measurement System ◽  
Radiant Energy ◽  
Unsteady Flows ◽  
Flux Measurement ◽  
Local Heat ◽  
Heat Flux Measurement ◽  
Local Heat Flux

A local heat–flux measurement system was built, calibrated, and tested for use in unsteady flows. The system was designed to maintain constant-wall-temperature boundary conditions. The measuring element is a thin-film heat flux gage made by sputter-coating gold onto a substrate. A constant-temperature anemometer is used to maintain the thin-film gage at a specified temperature under fluctuating conditions. A separate temperature control system maintains the surrounding boundary at the gage temperature. The system was calibrated for both steady and unsteady flows using a specially designed calibrator for local heat flux gages. The steady calibration was done with predominantly convective heat transfer. The unsteady calibration was achieved by adding oscillating radiant energy to the surface. Consequently, quantitative results can be obtained for both the mean and fluctuating components of the heat transfer. The frequency response was good to over 90 Hz. Sample results are presented of the unsteady heat transfer over a circular cylinder caused by natural vortex shedding at 70 to 80 Hz.

Local Heat Flux Measurement in a Permanent Magnet Motor at No Load

2013 ◽  
Vol 60 (11) ◽  
pp. 4852-4860 ◽  
Author(s):  
Hanne K. Jussila ◽  
Andrey V. Mityakov ◽  
Sergey Z. Sapozhnikov ◽  
Vladimir Y. Mityakov ◽  
Juha Pyrhonen
Keyword(s):  
Heat Flux ◽  
Permanent Magnet ◽  
Flux Measurement ◽  
Local Heat ◽  
Permanent Magnet Motor ◽  
Heat Flux Measurement ◽  
Local Heat Flux

Study on Heat Transfer Mechanism of Isolated Bubble Nucleate Boiling With MEMS Sensors

2010 ◽  
Author(s):  
Tomohide Yabuki ◽  
Osamu Nakabeppu
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Heat Flux ◽  
Bubble Growth ◽  
Local Heat ◽  
Nucleate Boiling ◽  
Heat Transfer Mechanism ◽  
Mems Sensors ◽  
Local Heat Flux ◽  
Dry Out

This paper describes an experimental investigation of heat transfer mechanism beneath isolated bubble during nucleate boiling with MEMS sensors having high temporal and spatial resolution in temperature measurement. The MEMS sensor fabricated for the boiling research includes eight thin film thermocouples and an electrolysis trigger on the topside of 20 × 20 mm2 silicon substrate and thin film heater on the backside. The electrolysis trigger initiates bubble growth by supplying hydrogen gasses as bubble nuclei with the electrolysis of the water by two electrodes. In the experiment, temperature fluctuation beneath an isolated bubble during saturated nucleate boiling of water was measured with the sensor. The measurement data presented strong evaporation and dry-out of the microlayer in the bubble growth phase and rewetting of the dry-out area in the bubble departure phase. Moreover, heat transfer induced by the boiling bubble was evaluated by computing local heat flux through a transient heat conduction simulation in the sensor substrate using the measured data as boundary condition. The heat transfer analysis shows that the local heat flux in the microlayer evaporation area has high value of the order of MW/m2, and the maximum value of about 2 MW/m2 is indicated near the center in an early phase of the bubble growth. On the other hand, the heat flux is very low of around zero at the dry-out area, where microlayer had disappeared completely, and slight increase was observed at the rewetting area. Total heat transferred from the surface reached to about half of latent heat in the bubble until the bubble departure. Finally, initial thickness of the microlayer under the bubble was estimated by integrating the derived local heat flux. As the result, it was distributed in a few μm within the measurement area.

scholarly journals New technique of the local heat flux measurement in combustion chambers of steam boilers

2011 ◽  
Vol 32 (3) ◽  
pp. 103-116 ◽  
Author(s):  
Jan Taler ◽  
Dawid Taler ◽  
Tomasz Sobota ◽  
Piotr Dzierwa
Keyword(s):  
Heat Flux ◽  
Flux Measurement ◽  
Local Heat ◽  
New Technique ◽  
Combustion Chambers ◽  
Heat Flux Measurement ◽  
Water Wall ◽  
Steam Boilers ◽  
Local Heat Flux ◽  
Heat Flux Meter

New technique of the local heat flux measurement in combustion chambers of steam boilers A new method for measurement of local heat flux to water-walls of steam boilers was developed. A flux meter tube was made from an eccentric tube of short length to which two longitudinal fins were attached. These two fins prevent the boiler setting from heating by a thermal radiation from the combustion chamber. The fins are not welded to the adjacent water-wall tubes, so that the temperature distribution in the heat flux meter is not influenced by neighbouring water-wall tubes. The thickness of the heat flux tube wall is larger on the fireside to obtain a greater distance between the thermocouples located inside the wall which increases the accuracy of heat flux determination. Based on the temperature measurements at selected points inside the heat flux meter, the heat flux absorbed by the water-wall, heat transfer coefficient on the inner tube surface and temperature of the water-steam mixture was determined.

Heat flux measurement techniques

1999 ◽  
Vol 213 (7) ◽  
pp. 655-677 ◽  
Author(s):  
P R N Childs ◽  
J R Greenwood ◽  
C A Long
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Heat Flux ◽  
Measurement Technique ◽  
Measurement Techniques ◽  
Flux Measurement ◽  
Thin Film Deposition ◽  
Temperature Sensors ◽  
Film Deposition ◽  
Heat Flux Measurement

Heat flux measurement is used in the field of fluid mechanics and heat transfer to quantify the transfer of heat within systems. Several techniques are in common use, including: differential temperature sensors such as thermopile, layered resistance temperature devices or thermocouples and Gardon gauges; calorimetric methods involving a heat balance analysis and transient monitoring of a representative temperature, using, for example, thin-film temperature sensors or temperature sensitive liquid crystals; energy supply or removal methods using, for example, a heater to generate a thermal balance; and, finally, by measurement of mass transfer which can be linked to heat transfer using the analogy between the two. No one method is suitable to all applications because of the differing considerations of accuracy, sensitivity, size, cost and robustness. Recent developments including the widespread availability and application of thin-film deposition techniques for metals and ceramics, allied with advances in microtechnology, have expanded the range of devices available for heat flux measurement. This paper reviews the various types of heat flux sensors available, as well as unique designs for specific applications. Critical to the use of a heat flux measurement technique is accurate calibration. Use of unmatched materials disturbs the local heat flux and also the local convective boundary layer, producing a potential error that must be compensated for. The various techniques in common use for calibration are described. A guide to the appropriate selection of a heat flux measurement technique is provided according to the demands of response, sensitivity, temperature of operation, heat flux intensity, manufacturing constraints, commercial availability, cost, thermal disturbance and acceleration capability for vibrating, rotating and reciprocating applications.

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