DOWNHOLE ENTHALPY MEASUREMENT WITH FIBER OPTICS
Studies investigating ways to measure enthalpy down hole have been in progress at Stanford University for the last three years. So far, the void fraction and the dispersed-phase velocity, which are the two essential factors required for calculation of flowing enthalpy, were determined by using resistivity and photosensors. Currently, research efforts have been oriented toward measuring down hole enthalpy by fiber optics. After discussing the applicability of using horizontal or vertical fiber tips, this paper describes the usage of normal reflection probe with the tip surface cut at a right angle to the fiber axis to investigate the void fraction initially in water-air flow then in water-steam flow. The calibration curve was obtained by correlating the void fraction given by the fractional flow ratio detector (FFRD) and the calculated local void fraction. Successful results were obtained for the slow bubble flow case. Future work includes determining the bubble velocity, and testing the device in a model wellbore.
Optical fiber probe to measure local void fraction profiles.
A fiber optic probe for measuring the local void fraction in a two-phase (air-water) flow has been developed. The liquid-gas and gas-liquid interfaces are detected by the normal reflections of IR laser light at the tip of a multimode fiber. The probe and its associated electronic circuitry were calibrated by using the averaged void fraction measured by a quick closing valve system. The void profiles obtained by this method were compared with those obtained by a conductivity local probe. The proposed optical system shows a better sensitivity at high void fractions.
Calculation of Complex Radiant Heat Load From Surrounding Radiator Surface Temperatures
Abstract A method for calculating the radiant heat exchange between an absorber and individual radiating components in its surroundings is reported. Radiator surface temperatures, ambient and absorber temperatures, and configuration factors for radiating components in the surroundings are used in the customary radiant heat exchange formulae. Simplified methods for calculating or estimating configuration factors for radiators of various shapes solely from angles, subtended at the absorber by the radiators are presented. The method has been verified in the laboratory under controlled conditions and has been used to advantage in the field studies. The method has advantages over the globe therometer method in certain applications.