New Approach for Airflow Measurement Using Thermal Resistance Simulation

Abstract

<p>This paper presents a new model-based approach to detect and compensate errors of positive temperature coefficient (PTC) sensors used for airflow measurement. From modeling and simulation, it can be shown that the thermal resistance of the sensor at self-heating mode was influenced by air flow magnitude. The sensor of type EPCOS-AG B59010 in a steel case, length 20 mm, diameter 2 mm was characterised over the flow rate range between 0 and 6 m/s and modeled to determine coupling thermal resistance interaction R<sub>th</sub> between the medium surrounding and sensor’s structure. Soiling caused by dust transported with the air on the sensor surface changing in the thermal resistance has observed and simulated in an experiment using a cylindrical sheath of PTFE – <em>Polytetrafluorethylen</em> with known heat conductivity λ<sub>S</sub> = 0.24 W/Km and diameter D. Parameters of model were then calibrated by evaluating current-voltage I(U)-characteristic at air velocity of v = 0m/s, and recalibration is then also used to correct the model parameters for v ¹ 0m/s. Result shows the soiling has exceeded critical thickness at D/d = 9 wherein the thermal resistance tends to be constant meaning cleaning sensor surface or replacing are needed.</p>

A Thermal Flow Sensor Based on Printed Circuit Technology in Constant Temperature Mode for Various Fluids

“…Thermal flow sensors [6] are particularly appealing because of their simple construction and robust operation principle which meets the requirements of HVAC applications. There are existing thermal sensor technologies presented by Abegaz et al [7], by Umar et al [8] or others [9,10,11], but there is a lack of cost-effective sensors, which can measure over the whole diameter with sufficient precision. A sensor based on printed circuit board (PCB) technology was already developed, manufactured, and characterised for air ducts by the authors [12].…”