Refrigeration – Storage of solidified or liquified gas – Liquified gas transferred as liquid
Reexamination Certificate
1999-07-29
2001-04-24
Capossela, Ronald (Department: 3744)
Refrigeration
Storage of solidified or liquified gas
Liquified gas transferred as liquid
C417S901000
Reexamination Certificate
active
06220037
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to manifolds for pumps used in handling cryogenic liquids, and more particularly, to a cryogenic pump manifold that utilizes a subcooler and heat exchanger to cool liquid entering the pump.
2. Description of the Prior Art
Cryogenic liquids are those which must be greatly refrigerated to keep them in a liquid state under reasonable pressures. Liquid nitrogen is one example. Various equipment has been developed for the handling and storage of such liquids, including pumps for transferring the liquid from one location to another, such as from a storage container to another area in which the liquid will be utilized. One type of pump which has been used for this purpose is a reciprocating piston or plunger pump, such as the Halliburton Triplex pump. Typically, an inlet or suction manifold is mounted on the pump connecting the pump suction to a source of the cryogenic liquid. It is desirable to provide the coldest possible cryogenic liquid to the pump inlet because this is necessary to meet the most efficient net positive suction head (NPSH) requirements of the pump. In all cryogenic pumps, the lower the suction fluid temperature the better will be the overall performance of the pump.
Insulating the suction manifold and inlet piping for the pump keeps the incoming liquid cool. This has the limitation of the capabilities of the insulation depending upon ambient conditions, and, of course, provides no additional cooling. One device which has been developed and which has had success in providing some cooling is a cryogenic subcooler on the pump inlet. A cryogenic subcooler is a device that takes the pressurized cryogenic liquid and uses a portion of it to produce a low temperature within the subcooler. This subcooler temperature is lower than the inlet liquid temperature because the portion of the inlet liquid that is released from the liquid flow to the subcooler is passed through an expansion device. This expansion usually causes the liquid to evaporate or “flash.” The expansion and evaporation of the liquid into a gaseous state causes the temperature to drop and lowers the subcooler temperature. The lower temperature expanded gas reduces the temperature of the pressurized inlet liquid entering the pump, producing a refrigerated or “conditioned” liquid.
Previous subcoolers may not be able to create enough heat transfer in some cases, so that the liquid entering the pump is not adequately cooled to meet the pump NPSH requirements to obtain optimum pump performance. Therefore, there is a need for greater subcooling.
The present invention solves these problems by incorporating a heat exchanger in conjunction with the subcooler to increase heat transfer and provide more cooling of the liquid entering the pump through the suction manifold.
Another problem with inadequate subcooling is that prolonged ambient heat gain may mean that the pump cannot function for a long period of time. Therefore, there is also a need for more cooling to overcome this problem. The present invention addresses this in that the greater exchange of heat in the apparatus results in an elimination of, or at least reduction in, ambient heat gain that provides longer running periods for the pump.
An alternate embodiment of the present invention increases the cooling even more by increasing the evaporation of liquid through the subcooler and heat exchanger through use of a fluid ejector or jetting device.
SUMMARY OF THE INVENTION
The present invention is an inlet or suction manifold or system for a cryogenic pump. The manifold comprises a subcooler and a heat exchanger which uses expanded gas to cool the cryogenic liquid entering the suction of the pump.
The invention may be described as an inlet system for a cryogenic pump which comprises an inlet header connectable to an inlet of the pump and a heat exchanger having a cooling side and a coolant side. The cooling side is in communication with the inlet header. The apparatus further comprises an expansion device in communication with the inlet header and the coolant side of the heat exchanger, such that some cryogenic liquid may be flowed out of the inlet header to the expansion device, expanded or evaporated into a gas through the expansion device whereby a temperature of the gas is lowered, and flowed through the coolant side of the heat exchanger, thereby lowering a temperature of the cryogenic liquid flowing thorough the cooling side of the heat exchanger.
The heat exchanger is preferably a shell and tube heat exchanger. The tube side of the heat exchanger is the cooling side. The shell side of the heat exchanger is the coolant side.
The system further comprises a jacket disposed around the inlet header forming a subcooler, and the jacket is in communication with the expansion device and the coolant side of the heat exchanger. The jacket and shell side are preferably integrally attached, and the inlet header and the tube side are also preferably integrally attached.
The system further comprises a coolant outlet in communication with the coolant side of the heat exchanger through which evaporated gas may be discharged. In one embodiment, the gas is exhausted or vented through the coolant outlet to the atmosphere.
In an alternate embodiment, the system further comprises an ejector having an inlet port or fluid inlet in communication with the coolant outlet, a jetting port or inlet connectable to a secondary gas source, and an ejector outlet port or fluid outlet. The secondary gas may be air, another gas from a separate gas source, or waste gas vented from the pump.
The expansion device may comprises an orifice or may be characterized by other devices such as a valve.
The present invention may also be described as a method of cooling liquid flowing through a cryogenic pump inlet header, the method comprising the steps of (a) connecting a cooling side of a heat exchanger to the inlet header, (b) diverting a portion of the liquid through an expansion device, (c) expanding the gas through the expansion device and expanding the liquid into a gas, thereby reducing a temperature of the gas, and (d) flowing cooled gas from the expansion device through a coolant side of the heat exchanger such that liquid flowing through the cooling side thereof is cooled. Step (d) preferably comprises flowing the cooled gas through a shell side of a shell and tube heat exchanger and flowing liquid to the inlet header through a tube side of the heat exchanger.
The method may further comprise the step of (e) exhausting the gas from the heat exchanger. Step (e) may comprise venting the gas to the atmosphere and/or increasing exhausted gas flow using a gas ejector. Step (e) also may comprise connecting the ejector to a secondary gas supply. The secondary gas is preferably selected from the group consisting of air or nitrogen. The secondary gas may also be supplied by venting the secondary gas from the pump.
In the method, step (d) may additionally comprise flowing the cooled liquid through a subcooler in communication with the coolant side of the heat exchanger.
Numerous objects and advantages of the invention will become apparent as the following detailed description of the invention is read in conjunction with the drawings that illustrate such embodiment.
REFERENCES:
patent: 2632302 (1953-03-01), Steele
patent: 2657541 (1953-11-01), Schilling
patent: 3131713 (1964-05-01), Kelley
patent: 3309883 (1967-03-01), Waterman
patent: 4932214 (1990-06-01), Nieratscher
patent: 5477691 (1995-12-01), White
Capossela Ronald
Halliburton Energy Service,s Inc.
Kennedy Neal R.
Kent Robert A.
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