Refrigeration – Storage of solidified or liquified gas – Liquified gas transferred as liquid
Reexamination Certificate
2000-04-10
2002-02-12
Capossela, Ronald (Department: 3744)
Refrigeration
Storage of solidified or liquified gas
Liquified gas transferred as liquid
C060S618000, C060S648000
Reexamination Certificate
active
06345508
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a multiphase heat exchanger that provides radial thermal heat transfer between a plurality of individually contained fluids.
BACKGROUND OF THE RELATED ART
Numerous operations are performed on oil and gas wells which require large volumes of nitrogen gas or other cryogenic fluids. These operations may be performed on both onshore and offshore wells. Such operations include foam fracturing operations, acidizing services, jetting down the tubing or down the tubing-casing annulus, nitrogen cushions for drill stem testing, pressure testing, insulation of the tubing-casing annulus to prevent such problems as paraffin precipitation, jetting with proppant for perforating and cutting operations, reduction of density of well workover fluids, displacement of well fluid from tubing during gun perforation operations to prevent excess hydrostatic pressure in the hole from pushing perforation debris into the formation, placing corrosion inhibitors by misting the inhibitor with nitrogen, extinguishing well fires, and other operations. Other operations that require cryogenic fluids at an ambient temperature include pipeline and vessel purging operations and refinery operations such as, recharging catalysts.
Nitrogen is typically stored in its liquid state because of the volume used however, liquid nitrogen will damage most carbon steel pipes used in oil and gas wells. Thus, various heating systems have been developed to raise the nitrogen to an ambient temperature. Typically, 185 BTUs per pound of nitrogen are required to heat the nitrogen to an ambient temperatures of 70° F.
One particular such operation is the fracturing of a subsurface formation of the well by pumping a fluid under very high pressure into the formation. The fracturing fluid which is pumped into the well often comprises a foamed gel which is produced by the use of nitrogen gas. The nitrogen for the foam fracturing operation is generally stored in a fluid form at temperatures of approximately −320° F.
At pressures encountered in these foam fracturing operations, the nitrogen changes state from a liquid to a gas at approximately −200° F. It is, therefore, desirable to heat up the nitrogen gas to a superheated state so that the foam fracturing fluid being pumped down the well will be at an essentially ambient temperature. This is because of the numerous adverse affects upon mechanical equipment of very low temperature which would otherwise be presented by the nitrogen foam.
With regard to land based wells, the nitrogen heating equipment generally includes open flame heaters. A problem is however, presented when performing foam fracturing operations on offshore wells. For safety and environmental reasons, open flames are generally not allowed on an offshore drilling platform. Therefore, it is necessary to provide a heater for the nitrogen which does not have an open flame.
Such flameless nitrogen heaters have previously been provided by utilizing the heat generated by an internal combustion engine and mechanical components driven thereby to heat a coolant fluid which transferred that heat to the nitrogen through a coolant fluid-to-nitrogen heat exchanger.
Numerous problems are encountered with prior art devices mainly because of the use of air as a heat transfer medium. Air is a notoriously poor heat transfer medium as compared to a liquid and the use of ambient air causes the system to be dependent upon ambient air conditions for proper operation. Additionally, due to the large bulky nature of the plenum chamber required for the use of air as a heat transfer medium, the air systems are typically very bulky and heavy. Therefore, there is a need for a flameless nitrogen unit that is compact in size, efficient in the heat transfer process, and economical.
SUMMARY OF THE INVENTION
The present invention provides a heat exchanger that collects heat from three sources generated by a drive system using an internal combustion engine and uses the heat to warm a fluid stream. The heat exchanger has three preferably cylindrical chambers one inside the other in coaxial alignment. The second chamber is positioned inside the first, and the third chamber is inside the second. Helical tubes are positioned inside the chambers to carry fluids for the heat exchange process. A first portion of a first helical tube is positioned inside the second chamber, and the second portion of the first helical tube is positioned in the third chamber. The second chamber has a hole in the wall to allow the passage of the second portion of the first tube into the third chamber. A second helical tube is positioned inside the first chamber.
Preferably, the first tube has a first fluid flow therethrough such as nitrogen or some other cryogenic fluid. The second tube has a second fluid flow therethrough, such as hydraulic fluid from the drive system. The second chamber has a third fluid flow therethrough, such as engine coolant, that also flows through the first chamber. Finally, the third chamber has a fourth fluid flow therethrough, such as exhaust from the engine. Preferably, the walls of the second and third chambers are made of a heat conducting material such as stainless steel or copper, so that the fluids flowing therethrough can benefit from radial heat transfer from one chamber to the next.
Alternatively, a third helical tube may be positioned inside the first chamber in parallel with the second helical tube. The third helical tube has a fifth fluid flow therethrough such as hydraulic fluid from the casing of the various pumps used in the drive system. In addition, the fifth fluid flow is preferably in a counter-flow relationship with the fluid flow inside the first chamber.
In a preferred embodiment, all of the fluids traveling through the heat exchanger are in a counter-flow relationship, such that, i.) the first fluid flow through the first portion of the first tube is in a counter-flow arrangement with the third fluid flow in the second chamber, ii.) the first fluid flow through the second portion of the first tube is in a counter-flow arrangement with the fluid flow in the third chamber, and iii) the second fluid flow through the second tube is in a counter-flow arrangement with the fluid flow in the first chamber.
In order to maximize the available surface area, the individual chambers of the heat exchanger may be equipped with spiral fins. The fins are positioned such that they spiral in the same orientation as the helical tubes within the chambers and they are positioned between the turns of the helical tubes. The spiral effect of the fins causes the fluid flow through the individual chambers to come into contact with all sides of the helical tubes. The fins can be positioned between each turn or some of the turns of the helical tubes.
The fourth fluid flow or exhaust passes through the third chamber and exposes the second portion of the first tube to the heat from the exhaust. The exhaust then exits through one end of the heat exchanger. In order to direct the flow from the exhaust, a cylindrical core with spiral fins may be positioned inside the third chamber. The cylindrical core acts to reduce sparks from the exhaust and disperse the flow of the exhaust gases to maximize the surface area of the tube exposed to the exhaust. The unit may also be equipped with a diffuser at each end and a cone shaped inlet and outlet for the exhaust gases to reduce engine noise.
Auxiliary pumps may be used to conduct the fluids through the helical tubes and the coolant through the chambers to compensate for the pressure drop that is incurred as the fluids flow through the heat exchanger.
In another embodiment, a system is provided for converting a liquid to a gas. The system includes a liquid source such as liquid nitrogen or other cryogenic fluid, a drive system including a pump, such as a triplex nitrogen pump connected to the liquid source. The drive system includes an internal combustion engine such as a diesel engine from Detroit, Caterpillar or other commercially available source for driving a hydrau
Bodhaine Jim
Hassanein Hany E.
Capossela Ronald
Seal Cynthia G.
Vita International, Inc.
Wisner Mark
LandOfFree
Heat exchanger does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Heat exchanger, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Heat exchanger will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2982514