Thin-Film Heat-Flux Microsensor for Heat-Transfer Measurement in Micro-Heat Exchangers/Microreactors

2012 ◽  
Author(s):  
Houssein Ammar ◽  
David Hamadi ◽  
Bertrand Garnier ◽  
Ahmed Ould El Moctar ◽  
Hassan Peerhossaini ◽  
...  
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Heat Flux ◽  
Heat Exchangers ◽  
Measurement Techniques ◽  
Heat Transfer Analysis ◽  
Heat Flux Sensor ◽  
Transfer Measurement ◽  
Heat Transfer Measurement ◽  
Flux Sensor

Heat-transfer analysis in microfluidic devices is of great importance in applications such as micro-heat exchangers and microreactors. This work reports on improvements in temperature measurement techniques, which can be the source of large errors due to their intrusiveness and the unreliability of conventional thermal sensors. Gold thin films were deposited on a borosilicate substrate to realize a 2D heat flux sensor for heat-transfer measurement along the main flow within microchannels. Two applications are shown, one related to micro-heat exchangers and the other to microreactors. For the micro-heat exchanger, the effect of length scale on heat transfer in a straight microchannel was investigated and the validity of macroscale correlations for convective heat transfer was checked for deionized water flowing in microchannels of heights 12 to 52 μm. For the microreactor, the reaction enthalpy of an acid–base reaction measured using the new heat-flux sensor had only a 5% discrepancy from the standard value, showing the efficiency of the new thin-film device.

Heat Flux Sensor With Minimal Impact on Boundary Conditions

2003 ◽  
Author(s):  
Arash Saidi ◽  
Jungho Kim
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Heat Flux Sensor ◽  
Inverse Heat Conduction ◽  
Minimal Impact ◽  
Sensor Performance ◽  
Flow Through ◽  
Flux Sensor ◽  
The Ideal

A technique for determining the heat transfer on the far surface of a wall based on measuring the heat transfer and temperature on the near wall is presented. Although heat transfer measurements have previously been used to augment temperature measurements in inverse heat conduction methods, the sensors used alter the heat flow through the surface, disturbing the very quantity that is desired to be measured. The ideal sensor would not alter the boundary condition that would exist were the sensor not present. The innovation of this technique in that it has minimal impact on the wall boundary condition. Since the sensor is placed on the surface of the wall, no alteration of the wall is needed. The theoretical basis for the experimental technique as well as experimental results showing the heat flux sensor performance is presented.

Time-Resolved Heat Transfer Measurements on the Tip Wall of a Ribbed Channel Using a Novel Heat Flux Sensor: Part II — Heat Transfer Results

2006 ◽  
Author(s):  
Sean Jenkins ◽  
Jens von Wolfersdorf ◽  
Bernhard Weigand ◽  
Tim Roediger ◽  
Helmut Knauss ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Flux Sensor ◽  
Internal Cooling ◽  
Time Resolved ◽  
Mean Values ◽  
Cooling Channels ◽  
Ribbed Channel ◽  
Detailed Surface ◽  
Flux Sensor

Measurements using a novel heat flux sensor were performed in an internal ribbed channel representing the internal cooling passages of a gas turbine blade. These measurements allowed for the characterization of heat transfer turbulence levels and unsteadiness not previously available for internal cooling channels. In the study of heat transfer, often the fluctuations can be equally as important as the mean values for understanding the heat loads in a system. In this study comparisons are made between the time-averaged values obtained using this sensor and detailed surface measurements using the transient thermal liquid crystal technique. The time-averaged heat flux sensor and transient TLC results showed very good agreement, validating both methods. Time-resolved measurements were also corroborated with hot film measurements at the wall at the location of the sensor to better clarify the influence of unsteadiness in the velocity field at the wall on fluctuations in the heat flux. These measurements resulted in turbulence intensities of the velocity and heat flux of about 20%. The velocity and heat flux integral length scales were about 60% and 35% of the channel width respectively, resulting in a turbulent Prandtl number of about 1.7 at the wall.

Evaluation of response characteristics of thin film gauge for conductive heat transfer mode

2020 ◽  
pp. 014233122096066
Author(s):  
Tanweer Alam ◽  
Rakesh Kumar
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Heat Flux ◽  
Short Duration ◽  
Temperature Data ◽  
Heat Transfer Analysis ◽  
Transient Temperature ◽  
Conductive Heat ◽  
Sensing Element ◽  
Element Analysis

Heat transfer analysis is the one of the most important designing aspects for many engineering systems. The design prospect in the preview of heat transfer focuses on the prediction of heat flux with the help of measured transient temperature data. Thin film gauges are one of the most predominant method for the heat flux prediction especially for short duration transient temperature measurement. Thin film gauges are usually exposed to the heated environment for the measurement purpose. However, there are some prominent research areas like ablation phenomenon met to spacecraft thermal shields during re-entry to the atmosphere, for which direct exposure of the thin film gauge to the heated environment causes the functional and working difficulties associated with the gauge. In the present study, it is aimed to investigate the suitability of thin film gauge for the conduction-based short duration measurement. An experimental set up is fabricated, which is used to supply the heat load to the hand-made thin film gauge using platinum as sensing element and quartz as a substrate. The transient temperature data is recorded during experiment is further compared with the simulated temperature histories obtained through finite element analysis. The heat flux estimation for both the analysis is made using measured transient temperature data by convolute integral of one- dimensional heat conduction equation. The estimated heat flux value for the experimental and numerical result is found to be in excellent agreement.

Noninvasive Method to Measure Thermal Energy Flow Rate in a Pipe

2020 ◽  
Vol 13 (3) ◽  
Author(s):  
Mohammed A. Alanazi ◽  
Thomas E. Diller
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Energy ◽  
Thermal Contact ◽  
Heat Flux Sensor ◽  
Accurate Estimation ◽  
Fluid Temperature

Abstract A noninvasive, thermal energy flowrate sensor based on a combination of heat flux and temperature measurements is developed for measuring the volume flowrate and the fluid temperature in a pipe. The sensor is covered by a thin-film heater and clamped onto the outer surface of the pipe. Two types of thin-film thermocouple elements are compared to minimize the thermal contact resistance R″ between the thermocouple and the surface of the pipe. A thin, flexible thermopile heat flux sensor (PHFS) is mounted over the thermocouples. A one-dimensional transient thermal model is applied before and during activation of the external heater to provide estimates of the fluid heat transfer coefficient h. The results are correlated with the volume flowrate Q and the fluid temperature Twc. Several different parameter estimation codes are used to estimate the optimal parameters by using the minimum root-mean-square (rms) error between the analytical and experimental sensor temperature values. The experiments are completed over a range of volume flowrates—1.3 gallons/min to 14.5 gallons/min. Encouraging measurement results give good correlation, repeatability, and sensitivity between the heat transfer coefficient h and the volume flowrate Q with an accurate estimation of the fluid temperature Twc. The resulting noninvasive thermal energy flowrate sensor can be used to estimate the volume flowrate and the fluid temperature in a variety of applications.

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