PO-86-04-3 -- Real-Time In-Situ Refractometer for Concentration Measurements in Absorption Machines PDF

An in-situ, real-time refractometer has been developed for the measurement of absorbent concentration in absorption machines. The refractive index of the absorber fluid is determined by measuring light loss from optical fiber cables that are immersed in the solution. The optical fibers have been modified by removing a portion of the cladding from the center of hard clad fiber optics to expose a segment of the core. The exposed portions of the fiber cores are placed at points within an absorption machine for which the measurement of absorbent concentration is desired. The entrance face of all modified fibers is illuminated with a light source. The amount of light lost from the core of each fiber to the absorber solution surrounding the fiber is measured and is directly related to the refractive index of the solution. Because the refractive index of a solution is a function of temperature, a thermocouple junction is placed adjacent to each of the exposed fibers to measure and compensate for local solution temperature. The composition of the absorber fluid is determined from the refractive index through use of an independently determined equation.

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