Microthermal sensors for determining fluid composition and flow rate in fluidic systems

B. Schmitt; C. Kiefer; A. Schütze

doi:10.1117/12.2017293

17 May 2013 Microthermal sensors for determining fluid composition and flow rate in fluidic systems

B. Schmitt, C. Kiefer, A. Schütze

Proceedings Volume 8763, Smart Sensors, Actuators, and MEMS VI; 87630O (2013) https://doi.org/10.1117/12.2017293
Event: SPIE Microtechnologies, 2013, Grenoble, France

Abstract

The analysis of fluid mixtures regarding their composition is still a major challenge, e.g. for Direct Methanol Fuel Cells (DMFC) to determine the concentration of methanol in water or for Selective Catalytic Reduction (SCR) to determine the amount of urea in water. A simple measurement method is realized with a microthermal sensor that introduces a short heat pulse into the fluid under test whilst the resulting temperature increase is measured reflecting thermal parameters of the fluid. For methanol in water this principle showed an almost linear dependence of the temperature increase on the methanol content for the concentration range 0 to 20 vol%. The sensitivity was determined to S = 0.12 K/vol% for methanol in water for a heat pulse of 0.5 s duration and a heater power of 60 mW. The accuracy achieved in single pulse measurements is approximately 2 %. By integrating additional temperature sensors in front and behind the microheater the flow rate of the liquid can also be determined using thermal anemometry. Because of the physical measurement principle to determine the chemical properties of the liquid the sensor promises better long-term stability than chemical principles. At the same time the low cost sensor construction and simple signal analysis make this principle promising for use in low cost mobile applications like DMFC power supplies for laptops.

Citation Download Citation

B. Schmitt, C. Kiefer, and A. Schütze "Microthermal sensors for determining fluid composition and flow rate in fluidic systems", Proc. SPIE 8763, Smart Sensors, Actuators, and MEMS VI, 87630O (17 May 2013); https://doi.org/10.1117/12.2017293

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