Measurement of Input Energy of LNG-based Gaseous Fuels with Capillary-typed Thermal Mass Flowmeter for Fuel Cells

Abstract

With capillary-typed thermal mass flowmeters (ctMFM) primarily calibrated with methane, it was investigated to measure input energy of LNG-based gaseous fuels to fuel cell systems. Energy flow rate can be expressed as <i>Q× CLNG× FR</i> where <i>Q</i> is heating value, <i>CLNG</i> is conversion factor from CH4 to the fuels, and <i>FR</i> is reading of ctMFM expressed as CH4 flow rate. Strong and negative correlation was observed between <i>Q</i> and <i>CLNG</i>, which will reduce deviation of the term "<i>Q× CLNG</i>" to 20% of deviation of <i>Q</i>. Calibration of ctMFM with an average composition of the fuels is necessary to obtain the correction factor <i>Q× CLNG</i>. It was found that input energy of LNG-based fuels can be measured with 40-100% range of ctMFM within {plus minus}1.5% uncertainty even if heating value of the fuels deviates by {plus minus}4.0%.