Parallel path Coriolis mass flow rate meter

An apparatus for measuring the mass flow rate of a fluid, comprising:

• (A) an inlet manifold and an outlet manifold;
• (B) two U-shaped flow tubes which
• (i) are free of pressure sensitive joints,
• (ii) are mounted in an essentially parallel fashion and fixedly attached, in a fluid tight manner, at the open ends of said U-shaped flow tubes to said inlet manifold and said outlet manifold,
• (iii) extend from said inlet manifold and outlet manifold in a cantilever fashion,
• (iv) each have an bending axis located near said fixedly attached ends and located in the same plane as and perpendicular to the side legs of said U-shaped flow tube, and a torsion axis located in the same plane as the side legs of said U-shaped flow tube, essentially parallel to and midway between said side legs, and perpendicular to said bending axis,
• (v) have essentially equal moments of inertia and essentially equal spring constants about said bending axes, and essentially equal moments of inertia and essentially equal spring constants about said torsion axes, and
• (vi) have a resonant frequency of oscillation about said torsion axes which is both different from the resonant frequency of oscillation about said bending axes, and different from the odd harmonic values of said resonant frequency of oscillation about said bending axes;
• (C) means for inputting to each of said U-shaped flow tubes essentially equal amounts of fluid from an inlet plenum, formed in part by said inlet manifold so that fluid flows through said U-shaped flow tubes in an essentially parallel fashion;
• (D) means for draining fluid from both of said U-shaped flow tubes through an exit plenum formed in part by said outlet manifold;
• (E) means attached to said U-shaped flow tubes to sinusoidally drive said U-shaped flow tubes at the resonant frequency about said bending axes, and as the tines of a tuning fork;
• and,
• (F) means to measure the time interval between the passage of the first side legs of each of said U-shaped flow tubes through the respective midplanes of oscillation, and the passage of the second side legs, caused by Coriolis forced deflection about said torsion axes, to pass through the respective mid-planes of oscillation at a later time;
• whereby the total fluid mass flow rate passing through both of said U-shaped flow tubes is determined from the magnitude of said measured time interval.