Laser-Driven Calorimetry Measurements of Petroleum and Biodiesel Fuels
Cary Presser, Ashot Nazarian, Amit Millo
The thermochemical characteristics were determined for several National Institute of Standards and Technology Standard Reference Material petroleum-based and biodiesel fuels, using a novel laser-heating calorimetry technique. Measurements focused on the sample endothermic/ exothermic behavior, specific heat release rate, and total specific heat release. The experimental apparatus consists of a copper sphere-shaped reactor mounted within a vacuum chamber, along with laser-beam-steering optical components, gas-supply manifold, and a computer-controlled data- acquisition system. At the center of the reactor, the liquid sample was injected into a copper pan substrate that rests and is in contact with a fine-wire thermocouple. The reactor is heated from opposing sides by a near-infrared laser to achieve nearly uniform sample temperature. The change in sample temperature with time (i.e., thermogram) is recorded and compared to a baseline (no sample) thermogram, and then processed (using an equation for thermal energy conservation) for the thermochemical information of interest. The results indicated that the energy reaching the pan is dominated by radiative heat transfer processes, while the change in the internal energy is the dominant process at the reactor sphere. Sufficient laser power is necessary for detecting the fuel thermal-related characteristics, and the required power can differ from one fuel to another. With sufficient laser power, the results can detect the preferential vaporization of the lighter and heavier fuel fractions. The total specific heat release obtained for the different conventional and biodiesel fuels used in this investigation were similar to the expected values available in the literature.
biodiesel fuels, calorimetry, heating value, laser-driven thermal reactor, standard reference materials, petroleum fuels, total specific heat release