Patent Application
20160158900
1. Field of the Invention
This invention is directed to the field of vortex tubes. More particularly, the present invention relates to a manufacture using a method of a vortex tube design, which provides a vortex tube having a high efficiency by eliminating freeze up in operations with natural gas.
2. Description of the Prior Art
A vortex tube (VT) comprises a slender tube with a diaphragm with a discharge hole in the center of the diaphragm, closing one end of the tube, one or more tangential inlet nozzles piercing the tube just inside of the diaphragm and, depending on the vortex tube's desirable performance, a controlled discharge opening (throttle valve) or plug (U.S. Pat. No. 5,911,740) on the other end of the slender tube.
In the vortex tube, the inlet high-pressure gas passes through the tangential nozzles resulting in a pressure decrease and velocity increase of the gas. The low pressure highly rotating gas then undergoes energy separation (vortex phenomenon) forming two internal low-pressure currents. One current is cold and the other is hot. Under some circumstances a cold fraction or cold gas discharged from the vortex tube through the diaphragm opening may freeze up and reduce the diameter of the discharge orifice due to the formation of ice, resulting in the vortex tube's performance deterioration.
It is known to use a vortex tube's hot fraction to prevent freezing in the discharge diaphragm (U.S. Pat. No. 5,749,231 and U.S. Pat. No. 5,937,654) as well as, as it is practiced in the vortex tubes of the present invention to use the hot fraction to warm up the vortex tube's inlet nozzles.
The present invention provides for improving the reliability of the vortex tubes designed per U.S. Pat. Nos. 5,749,231 and 5,937,654 in operation with compressed natural gas. The improvement is achieved by specifying the VT diaphragm hole preferably in a range of 0.25 to 0.80 of the slender tube's diameter, the vortex tube's length, preferably, as no less than 3 diameters of the slender tube and the vortex tube's uncontrolled opening diameter as no greater than 0.60 of the slender tube's diameter.
The present invention will now be described in terms of the presently preferred embodiment thereof as illustrated in the drawings. Those of ordinary skill in the art will recognize that this embodiment is merely exemplary of the present invention and many obvious modifications may be made thereto without departing from the spirit or scope of the present invention as set forth in the appended claims.
The flow diagram in
It is known that a small portion of the vortex tube's inlet gas flow doesn't participate in the vortex energy division but moves alongside the diaphragm inward surface directly into the diaphragm hole. The existence of such a bypass flow is due to the presence of the radial pressure gradient uncompensated by the centrifugal forces in the stationary boundary layer on the wall of the diaphragm. Mixture of the bypass flow that keeps the original inlet gas temperature with the cold gas passing through the diaphragm hole increases the vortex cold outlet temperature. Such thermal influence, at times noticeable, doesn't affect the vortex tube operations unless compressed natural gas is used as the vortex tube's working medium.
Here the gas passing through the VT's pressure reducing nozzles, generally, carries some liquid (water and hydrocarbons) condensed under the depressurized gas low thermodynamic temperatures and Joule-Thomson temperature drop. The condensed liquid, due to its gravity, provides for a substantial portion of the by-pass flow. The two-phase chilled mixture mixing up with the vortex tube's cold outlet or with the vortex tube's single discharge flow (per U.S. Pat. No. 5,911,740) results in freezing of the diaphragm hole which reduces the interior diameter of the orifice 16 and accordingly the vortex tube performance deteriorates.
Reduction of the diaphragm's hole 16 diameter is an efficient way to reduce the by-pass stream flow rate. However, a smaller diaphragm hole increases the gas pressure in the vortex tube. This results in decreasing the vortex pressure ratio (ratio of the inlet gas pressure to the gas pressure in the vortex tube). This, in turn, reduces the intensity of the vortex energy division in the gas flow. The best results with the present invention can be achieved by specifying the diaphragm's hole diameter 16, preferably, in a range of 0.25 to 0.80 of the slender tube diameter D. The length of the vortex tube shall allow for completing the vortex energy division, thus to efficiently warm the diaphragm in a heat exchanger as described U.S. Pat. No. 6,289,679. The uncontrolled opening 32 in a heat exchanger shall allow for efficient circulation of just the vortex hot (peripheral) flow without blending it with the vortex cold (central) flows. The optimal results with the present invention can be achieved by specifying the length of the vortex tube as no less than 3.0 diameters (D) of the slender tube and the uncontrolled opening's diameter as no greater than 0.60 diameter (D) of the slender tube.
