Abstract:
A method and apparatus for fluid analysis includes a sensor for determining the index of refraction of a fluid. Advanced methods of fluid analysis relate index of refraction and other measured physical characteristics of the fluid.

Description:
BACKGROUND OF INVENTION  
         [0001]    The present invention relates to measuring instruments, and more particularly to devices for analyzing fluids using measurements of index of refraction and other physical characteristics.  
           [0002]    Refrigerant gases containing chlorine, for example difluorodichloromethane (known as “R12”), have been phased out of use in new refrigeration systems for their harmful effects on the environment. Tight regulatory controls have been imposed governing the reuse and reclamation of such refrigerants.  
           [0003]    A device and method for refrigerant analysis is disclosed in our U.S. Pat. No. 5,870,185, the disclosure of which is incorporated herein by reference. The apparatus of U.S. Pat. No. 5,870,185 has been found to be particularly useful in analyzing refrigerant samples by determining index of refraction along with other physical parameters. A fluid sample is introduced into a sample chamber, then a laser is shown through the fluid in chamber and out a glass window into transparent positioner. The angle of the laser in the positioner as it exits the chamber through the window is directly related to the index of refraction.  
           [0004]    Our prior device&#39;s characterization of transparent fluids is based on the physical property of refractive index, correlated to temperature and pressure. By using these three variables, the microprocessing and physical sampling apparatus characterizes refrigerants and discriminates them from one another to within EPA standards of 0.5% of pure.  
           [0005]    Refrigerants (R-12, R-22, R134a, R-113, R-114, R-115, R-11, R-13, R-123, R-152a) are indexed and classified to 99.5% and to within 2% in binary mixtures such as 500,501,502 and all of the new 400 series. The current instrument can characterize any fluid, which is transparent, with refractive index (RI) in the range from 1.15000 to 1.4000+/−0.00002 and vapor pressure up to 350 Psia.  
           [0006]    The device can be programmed to be used as the discriminator between specific chemical groups, such as refrigerant analysis (pure and binary) or chemical characterization online in a chemical production facility. Online applications typically require a flow-through cell sampling technique. A computer, communicating via an existing RS232 port, would then query the analyzer at specified intervals to assess the current purity or status of the material in question. From this point, process functions can, be modified, automatically stopped, or reported in a variety of ways.  
           [0007]    The technology incorporated into the instrument for making refractive index measurement is extremely reliable since it requires no moving parts. Utilization of a laser light source and photo diode array provides an extremely accurate RI measurement and allows the instrument to obtain a resolution of 0.00002 RI units using advanced digital processing of the refracted beam. This technology, with an upward shift in the RI measurements, can also achieve an even larger cross-section of chemical processing capabilities. Identification of contamination levels, by monitoring changes, can reduce equipment downtime and increase the life of a system.  
           [0008]    Identifying and properly handling refrigerants is a major concern and the meeting of EPA standards and regulations is required. The device analyzes liquid refrigerant rather than vapor/gas samples and eliminates errors caused by other NDIR methods. The instrument is designed with optic refractometry using high-speed microprocessors. Despite the complexity of blended gases, which have challenged the refrigerant industry for years, the device and method of the prior patent are easy-to-use and provide the analysis in seconds. Experience has shown, however, that the physical construction of the refraction chamber shown in U.S. Pat. No. 5,870,185 is less than optimal. Potential problems with leakage, glass breakage, and gasket swelling have presented needs to be addressed. In particular, it has been found that it is difficult to manufacture a chamber with machining tolerances tight enough to seal the chamber yet loose enough to not break the glass window of the chamber. In addition, conventional gasketing materials tend to swell and block the laser beam. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0009]    A more complete understanding of the invention and its advantages will be apparent from a review of the Detailed Description in conjunction with the following Drawings, in which: FIG. 1 is a partially broken away top view of the improved refraction chamber of the present invention; FIG. 2 is perspective view of the refraction chamber; FIG. 3 is an end view of the refraction chamber; and FIG. 4 is a side view of the refraction chamber. 
     
    
     DETAILED DESCRIPTION  
       [0010]    Referring initially to FIGS.  1 - 4 , where like reference numerals indicate like and corresponding elements, a refraction chamber  10  is fitted to a transparent positioner  12 . Laser  14  is fixed to one side of chamber  10 , positioned to direct a beam into the chamber through passage  16  and out of the chamber through window  18 . As described in U.S. Pat. No. 5,870,185, a photo diode array (not shown) is fixed to the far end (not shown) of transparent positioner  12 .  
         [0011]    Chamber  10  is formed of two mating sections, outer section  20  and inner section  22 . Outer and inner sections  20 ,  22  are sealed by a gasket ring  24 . Outer and inner sections  20 ,  22  are preferably machined from aluminum, and gasket ring  24  is a polytetrafluoroethylene (Teflon®) material. Gasket ring  24  has rectangular cross-sections, with the height of the cross section about a third of the width. (height-width ratio 1:3). Gasket ring  24  is trapped in mating, rectangular grooves  26 ,  28  on opposite sides of outer and inner sections  20 ,  22 . When fasteners  30  on through bolts  32  are tightened, faces  34 ,  36  of outer and inner sections  20 ,  22 , respectively, meet to capture and compress gasket ring  24 , thereby sealing sections  20 ,  22  and preventing the gasket ring  24  from extruding into the chamber and from blocking the laser.  
         [0012]    Semi-hemispherical inner surfaces  38 ,  40  are machined in outer and inner sections  20 ,  22 , respectively, to form a void into which a sample fluid may be drawn and expelled though inlet  42  and outlet  44 . Inlet  42  and outlet  44  are at a right angle to each other, to improve flow and avoid impingement on window  18 . Ports  46 ,  48  are provided in outer section  20  to permit mounting of pressure and temperature transducers (not shown).  
         [0013]    Transparent positioner  12  and inner section  22  have complementary steps  50 ,  52  to improve the geometry of the device.  
         [0014]    Laser  14  may be mounted using pipe thread  54  or cylindrical pins  55  in mating holes  56 .  
         [0015]    Whereas, the present invention has been described with the respect to a specific embodiment thereof, it will be understood that various changes and modifications will be suggested to one skilled in the art, and it is intended to encompass such changes and modifications as fall within the scope of the appended claims.  
         [0016]    It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the type described above.  
         [0017]    While the invention has been illustrated and described as embodied in a refrigerant analyzer, it is not intended to be limited to that use or the details shown, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention.  
         [0018]    Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.  
         [0019]    What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.