BR102014015502A2 - subsea heat exchanger - Google Patents

Abstract

submarine heat exchanger. it is an underwater heat exchanger, wherein the heat exchanger has a tube bundle (1) comprising at least one tube winding (2) arranged to operate submerged in water and efficient to guide a fluid (f) to be cooled by surrounding water in contact with the pipe, wherein the pipe bundle has a longitudinal extension (1) and a perimeter (o). several nozzles (3) are spatially distributed to said perimeter (o), wherein the nozzles are efficient for the discharge of water jets that collide with the pipes, in the nozzles oriented to induce a displacement in the ambient water volume. (r) passing the perimeter (o) in various locations and directions.

Description

Field of the Art The present invention relates to forced convection heat exchangers for underwater use.

Background and Prior Art In the recovery and production of gas and oil from subsea wells, heat exchangers are often required to control the temperature in the production fluid or cooling medium used in production equipment, for example.

[003] Submarine heat exchangers are often based on natural seawater convection and can be classified as passive or forced convection chillers. Basically, a passive convection chiller comprises a series of pipes that are exposed to seawater that can move freely between the pipes. Passive convection chillers are generally bulky and heavy structures and suffer from uncontrollable operating parameters, such as variations in seawater currents and temperature, which result in poor control or complete lack of control over the cooling process.

A forced convection cold typically comprises a bundle of tubes bounded by an outer casing or duct that is associated with a driven pump or a propellant that generates a forced water / seawater flow through the duct. Examples of forced convection chillers can be found in WO2010 / 002272A1, WO2012 / 141599A1 or WO2013 / 004277A1, for example, conducted forced convection chillers have improved control over the target fluid temperature, but may still suffer from biofouling and material deposition in the heat exchanger tubes. Brief Description of the Invention The present invention aims to provide a forced convection heat exchanger with improved control over the cooling process.

Another object of the present invention is to provide a forced convection heat exchanger that is less susceptible to biological or particulate fouling of heat exchanger tubes.

Still another object of the present invention is to provide effective cooling by forced convection in a compact model heat exchanger.

These and other objects are assembled into a heat exchanger according to the present invention, wherein a turbulent flow of water originates above the heat exchanger tubes by means of a plurality of nozzles arranged to discharge jets of heat. water towards the pipes.

More precisely, an underwater heat exchanger is provided which has a tube bundle comprising at least one tube winding arranged to operate submerged in water and efficient to guide a fluid to be cooled by surrounding water in contact with. the tube, wherein the tube bundle has a longitudinal extension and a perimeter and a plurality of nozzles distributed in spatial relation to the parameter, wherein the nozzles are efficient for discharging water jets that collide with the tubes, the nozzles being They are oriented to induce in the ambient water flow a displacement that passes through the perimeter in various locations and directions.

[010] Nozzles are configured to generate turbulent water displacement near the pipes.

Turbulent flow can be achieved when, as preferred, the nozzles are arranged at an angle on a piano transversely to a longitudinal extent of the beam tube to discharge water jets from the tangential direction at a 90 ° impact angle with the perimeter of the pipe bundle.

In this regard, the invention may be embodied in different embodiments and configurations with respect to the arrangement of nozzles relative to the tube bundle.

In one embodiment, the nozzles are arranged radially outside the tube bundle. More precisely, the nozzles may be arranged radially outside the circular parameter of a helical tube bundle, wherein the nozzle mouths are directed internally to a center of the tube bundle. In this embodiment, the nozzles may be directed to generate, in seawater surrounding the heat exchanger, an internally directed displacement extending substantially tangential to the perimeter or substantially radial to the center of the helical tube bundle as seen. in a radial plane of the heat exchanger.

In another embodiment, the nozzles are disposed within the tube bundle. More precisely, the nozzles may be arranged radially within a helical tube bundle, wherein the nozzle mouths are directed externally to a perimeter of the tube bundle. In this embodiment, the nozzles may be directed to generate in seawater within the helical tube bundle an externally directed displacement which may be radial or non-radial with respect to the radial plane of the tube bundle.

[015] Nozzle angle orientation can be used to create a rotating motion and ambient seawater displacement within and over the pipe bundle.

[016] In each of the above embodiments, the nozzles may be additionally arranged in a slope to generate or withstand a displacement of seawater through the heat exchanger. Thus, alternatively or in addition to the nozzle angle orientation in radial planes, the nozzles may be arranged at an inclination on the longitudinal geometrical axis in the axial plane to discharge jets of seawater from an angle of 30 ° to 90 °. ° of impact with the perimeter of the pipe bundle.

[017] Nozzles may be arranged in assemblies, wherein nozzles are commonly supplied with seawater from an underwater engine and pump assembly that discharges seawater at high pressure and flow rate into a manifold. In preferred embodiments, a manifold provides seawater to a plurality of rising pipes extending from the manifold in the longitudinal direction of the pipe bundle, each rising pipe carrying a set of nozzles respectively.

[018] Seawater is supplied to the nozzles by means of an underwater engine and pump assembly. By regulating the output from the motor and pump assembly and / or closing / opening nozzles by means of valves, it is possible to achieve active temperature control in the target fluid. To this end, a variable speed drive (VSD) motor that drives the seawater pump allows common nozzle control.

Alternatively, the nozzles may be controllable together through a pressure regulating device in the water supply pipe.

Additionally, one nozzle assembly may be controllable separately from the other nozzle assemblies. For example, nozzle assemblies may be controlled for intermittent discharge of water jets on an alternating scale and in consecutive order. This accomplishment effectively reduces the capacity required by the motor and pump assembly.

[021] In one embodiment, it is possible to obtain the pulsating water jets of the nozzles by installing a flow pulse generator upstream of the nozzles.

[022] Nozzles may be made as holes formed in the rising pipes that are supplied with seawater through the manifold.

Alternatively, the nozzles may be made as venturi tubes or ejectors operating according to the Bernoulli principle.

Short Description of the Figures The embodiments of the invention will be further explained below with reference to the schematic and accompanying figures. In the Figures, [025] Figure 1 is a side view showing a first embodiment of a heat exchanger according to the present invention. [026] Figure 2 is a top view of the heat exchanger of Figure 1, [ 027] Figure 3 is a top view corresponding to Figure 2 showing a second embodiment of the heat exchanger, [028] Figure 4 is a larger scale broken detail showing the arrangement of nozzles in the heat exchanger, [029] Figure 5 is a corresponding detail showing the alternative arrangement of nozzles on the heat exchanger. [030] Figure 6 is a side view showing another embodiment of the heat exchanger, and [031] Figure 7 is a top view showing shows yet another embodiment of the heat exchanger.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS It is intended to point out that while the invention is described herein with reference to a vertically oriented seaward heat exchanger, the teachings given can be similarly applied to submerged heat exchangers horizontal or inclined orientation. Accordingly, any term used in the description to define spatial relationships should be understood to include equivalent terms applicable to heat exchangers of other major orientations than illustrated vertically.

A forced convection heat exchanger 1 for subsea use utilizes a tube bundle comprising at least one tube coil 2 through which a fluid flow F is advanced under heat transfer through the tube wall to water. from the surrounding sea SW. Then, heat exchanger 1 operates submerged in seawater, as shown in Figure 1.

[034] Fluid flow F can be a hydrocarbon production fluid flow that needs cooling before reaching downstream equipment such as pumps or compressors, etc. However, heat exchanger 1 is not limited to cooling production fluid, but may similarly serve to cool another fluid involved in subsea hydrocarbon production, such as refrigerant, lubricant or barrier fluid, for example.

Additionally, the heat exchanger 1 comprises a plurality of nozzles 3 which are spatially distributed at a perimeter O of the pipe bundle 2. In this context, as used in the disclosure, "spatial relation to the perimeter" must be understood. such as nozzles 3 which are distributed along perimeter O or at least along substantial portions of the perimeter and externally or internally at a distance from perimeter O, as seen in a side view or a top or bottom view of the heat exchanger. heat.

[036] Nozzles 3 are efficient for discharging seawater jets towards tube bundle 2. Nozzles 3 are arranged in risers 4 so that each riser 4 carries a set of nozzles 3. The pipes upstream 4 are supplied with seawater via a manifold 5 which distributes seawater at high pressure and at the flow rate generated through an underwater engine 6 and a pump 7.

[037] The operation of motor and pump assembly 6, 7 can be controlled by a variable speed drive (VSD) 8 and a heat exchanger control unit (HXC) 9 that adjusts the water supply of the for nozzles 3 in response to the temperature of the target fluid F, detected by a temperature sensor (TS) 10. Thus HXC and VSD adjust the operation of the nozzles together in response to a cooling effect and a reduction in temperature. required temperature in target fluid F.

Additionally or alternatively, the operation of the nozzles 3 may be controlled by the valves 11 arranged to allow or cut the water flow through the risers 4, thereby controlling the operation of one nozzle assembly 3 separately from the other nozzle assemblies. .

[039] Valves 11 can be realized as on / off valves and can be controlled from the HXC. By opening the valves 11 one at a time, in consecutive order, for example, a pulsating jet discharge can be achieved towards the pipe bundle 2. This arrangement also considerably reduces the required capacity of the motor and pump. which are installed to provide seawater to the nozzles. Alternatively, the pulsating jets may be generated by means of a pulse generator installed in the seawater supply upstream of the nozzles (not shown in the Figures).

Alternatively, operational control of the plurality of nozzles may be achieved from a pressure regulating device 11 'arranged to adjust the flow rate in the seawater manifold 5 as illustrated in Figure 1.

In a structurally non-complex manner, the nozzles may be made as holes produced through the wall of the risers.

[042] The most efficient water jets can be generated from nozzles produced in the form of venturi tubes or ejectors that operate according to the well-known Bernoulli principle. A corresponding ejector is shown in Figure 4, wherein this ejector comprises a nozzle 3 which is installed in a Venturi tube 12 provided with a high radius diffuser section 13. The nozzle 3 communicates with the rising pipe 4 by way of a passage 14 through the rising pipe wall. A high velocity jet J is discharged from the converging mouth of the nozzle 3, creating within the tube 12 a low pressure zone that pulls seawater through an open inlet to the tube. The incorporated seawater is mixed with the jet in the pipe, and the mixed flows are discharged from the discharge end towards the pipe bundle 2.

[043] Nozzles 3 are oriented for the discharge of water jets that collide with heat exchanger tubes 2, including in the ambient volume of water from a flow or a displacement R passing perimeter O of the heat exchanger tubes. heat 2. The water jets are divided by the tubes and assembled into zones of turbulent water T in the leeward of the tubes substantially, as shown schematically in Figure 4. Both the collision jets in the windward tube and the turbulent flow in the leeward tube contribute to reduce fouling such as particle deposition, scaling and biological fouling in the heat exchanger tubes.

While the partial view of Figure 4 illustrates nozzles 3 which are oriented transversely or at right angles to the perimeter O, the partial view of Figure 5 illustrates nozzles that are angled relative to the perimeter and, more precisely, nozzles that are inclined upwards at an angle α relative to the perimeter O. The inclined nozzle orientation 3 can be used to improve an upward displacement U of seawater through the pipe bundle 2, added to the natural upward displacement in the form of currents. convection due to the heat that is absorbed by the ambient water. It is understood that the angle α may range from about 30 ° to 90 ° in practice.

[045] Returning to the embodiment shown in Figures 1 and 2, a heat exchanger model is illustrated, wherein a plurality of nozzles 3 are disposed along and radially outside the circular perimeter of a bundle of coils. More precisely, several risers 4 are distributed over the pipe bundle, wherein the risers 4 rise from a circular manifold 5 which connects the risers to the motor and pump assembly 6, 7 (shown in Figure 1 only). Preferably, the risers may also be angularly spaced in the pipe bundle 2 as illustrated.

Each rising pipe 4 carries a set of nozzles 31 to 36. While the nozzles 31 - 33 on the left side of the Figure in Figure 2 are oriented radially towards the center C of the beam tube, the nozzles 34 - 36 on the right side of the Figure are oriented substantially in a tangential direction relative to the perimeter of the pipe bundle 2. Arranging the nozzles in different orientations on the same heat exchanger as shown in Figure 2 is possible. This option is shown in the present document by way of illustration and it is assumed that a more frequent practice will involve nozzles that are equally oriented to the perimeter or center of the heat exchanger. However, different combinations of nozzle numbers and orientations may be conceivable.

It is noted that the external location of the nozzles 31 - 33 in Figure 2 will induce in the ambient water volume a displacement where the main steering component is radial toward the center of the pipe bundle 2. In the same way as the external location of the tangentially oriented nozzles 34 - 36 in Figure 2 will induce in the ambient water volume a displacement comprising a tangential direction member which is deflected towards the interior of the heat exchanger by the jet is discharged from the adjacent downstream nozzle. In either case, the tangentially and internally and externally located open nozzles 31 to 36 will generate a displacement R of ambient water passing at the perimeter O of the beam tube at various locations and directions, producing turbulence near the tubes. Additionally, displacement of water from the outside to the interior of the tube bundle will produce an axial displacement and replacement above the volume of water that is surrounded by the tube winding 2. Additionally, the non-radially or substantially tangentially oriented nozzles 34 - 36 will generate a water rotation displacement surrounding the heat exchanger tubes 2 (i.e. a clockwise rotation according to the configuration of Figure 2), [048] An inverted heat exchanger model is illustrated in Figure 3. The embodiment of Figure 3 differs from the previous one in that the risers 4 and the nozzles 3 are located along a circular perimeter of a helical tube bundle 2 and radially within it, wherein the nozzles open externally at direction to the perimeter of the pipe bundle. While nozzles 31 - 33 on the right side of the Figure are oriented substantially radially from center C, nozzles 34 - 36 on the left side of the Figure are oriented in non-radial directions relative to Center C. Again, arrange the nozzles at Different orientations on the same heat exchanger as illustrated in Figure 3 is possible. This option is shown in the present document by way of illustration and it is assumed that a more frequent practice will involve nozzles which are equally oriented to the perimeter or center of the heat exchanger. However, different combinations of nozzle numbers and orientations may be conceivable.

It is noticed that the internal location of the nozzles 31 - 33 in Figure 3 will induce, in the ambient water volume surrounded by the pipe winding 2, a displacement where the main steering component is radial and external to the center. C. It is appreciated in the same way that the internal location of the nozzles 34 - 36 in Figure 3 will induce in the ambient water volume a displacement comprising a tangential component of direction.

[050] In both cases, the externally, radially or non-radially and internally located open nozzles 31 to 36 will generate, in the ambient water volume, a displacement R passing perimeter O in various locations and directions, producing near turbulence. to the pipes. Additionally, the displacement of water from inside the tube bundle will cause a replacement below the volume of water that is displaced from the interior of the tube winding 2. In addition, the non-radially oriented nozzles 34 - 36 may generate a water rotation displacement surrounding the heat exchanger tubes 2 (i.e. counterclockwise rotation according to the configuration of Figure 3).

[051] The invention is not limited to any specific number of risers 4, number of nozzles 3 or number of turns in a pipe winding. Other models besides the circular configuration shown in Figures 1-5 are also possible.

An alternative model is illustrated in Figure 6 which shows in a side view a heat exchanger comprising a flat or substantially flat serpentine tube winding. Several nozzles 3 are distributed along the largest parts of a perimeter. Rectangular O and externally thereto, the nozzles in operation perform a displacement R of ambient water passing perimeter O in various locations and directions, producing turbulence near the pipes 2.

Yet another alternative embodiment is illustrated in Figure 7, which shows in a top view the highest tube layer of a heat exchanger comprising a bundle of tubes, including various coiled or flattened or substantially flat tube windings. 2. A plurality of nozzles 3 are distributed along the largest portions of a rectangular perimeter O and externally thereto, wherein the nozzles are disposed together on pipes 4 that rise from a manifold 5. Note that in the top view of Figure 7 only the highest nozzle 3 in each nozzle assembly is shown.

[054] Other nozzle models other than the polished Venturi tube are viable, such as a fluid nozzle designed to generate a self-oscillating jet. The self-oscillating jet nozzles do not involve moving parts and are basically maintenance-free, making them attractive for subsea use and deployment in the forced convection heat exchanger. Using nozzles that generate self-oscillating jets results in a higher heat transfer coefficient and larger coverage area, so fewer nozzles are required compared to standard jet nozzles.

[055] Another group of nozzles, which may be contemplated for use in submerged forced convection heat exchangers, are nozzles designed to create synthetic jets formed of ambient water by periodically sucking and ejecting fluid out of a hole for a cavity. A diaphragm that is built into a cavity wall is brought in a periodic time motion driven by a piezoelectric generator or an electromagnetically driven piston, for example.

Based on the teachings herein, further modifications will be possible without departing from the scope of the invention as defined by the appended claims.

Claims

Claims (15)

Underwater heat exchanger, characterized in that it comprises: - a tube bundle (1) comprising at least one tube winding (2) arranged to operate submerged in water and efficient to guide a fluid (F) to be cooled by surrounding water in contact with the pipe, wherein the pipe bundle has a longitudinal extension (L) and a perimeter (O), - a plurality of nozzles (3) distributed in spatial relation to the perimeter (O), wherein the nozzles are efficient for discharging water jets (j) which collide with the pipes, wherein the nozzles are oriented to induce in the ambient water volume a displacement (R) passing perimeter (O) in a plurality of locations and directions. Heat exchanger according to claim 1, characterized in that the nozzles (3) are configured to generate a turbulent displacement (R) of water close to the pipes (2). Heat exchanger according to any preceding claim, characterized in that the nozzles (3) are arranged in a plane transversely to the longitudinal extension (L) for discharging water jets (J) from a tangential direction to 90 ° impact angle with the perimeter (O) of the pipe bundle. Heat exchanger according to Claims 1 to 3, characterized in that the nozzles (3) are arranged at a slope in a plane parallel to the longitudinal extension (L) for discharging water jets (J) from from an angle of 30 ° to 90 ° of impact with the perimeter (O) of the tube bundle. Heat exchanger according to any preceding claim, characterized in that the nozzles (3) are arranged radially outside the perimeter (O) of a helical tube bundle, wherein the nozzle mouths are directed internally to a nozzle. center (C) of the pipe bundle. Heat exchanger according to any one of claims 1 to 5, characterized in that the nozzles (3) are arranged radially within a helical tube bundle, wherein the nozzle mouths are directed externally to the perimeter. (O) of pipe bundle. Heat exchanger according to any preceding claim, characterized in that it further comprises a manifold (5) and a plurality of rising pipes (4) extending from the manifold in the longitudinal direction (L) of the manifold. tube bundle, each rising pipe supporting a set of nozzles (3). Heat exchanger of any preceding claim, characterized in that the nozzles (3) are controllable together by a VSD motor (6) driving a seawater pump (7). Heat exchanger according to any preceding claim, characterized in that the nozzles (3) are controllable together by a pressure regulating device (11 ') in the water supply pipe (5). Heat exchanger according to any preceding claim, characterized in that one nozzle assembly (3) is controllable separately from other nozzle assemblies. Heat exchanger according to Claim 9, characterized in that the nozzle assemblies are alternately operable in consecutive order. Heat exchanger according to any preceding claim, characterized in that the nozzles (3) are ejectors (12) operating according to the Bernoulli principle. Heat exchanger according to any preceding claim, characterized in that a flow pulse generator is installed upstream of the nozzles. Heat exchanger according to Claim 1, characterized in that it comprises: - a non-conducting, vertically oriented, coiled spiral heat exchanger tubing open to the surrounding seawater; a circular manifold disposed at the lower end of the heat exchanger, wherein the manifold is supplied with seawater from a motor and pump assembly; - several ascending pipes rising vertically from the circular manifold, angularly spaced in the coiled and coiled heat exchanger tubing, and - a nozzle assembly in each rising pipe, where the nozzle mouths are directed radially and internally to the center of the heat exchanger tubing. Heat exchanger according to Claim 1, characterized in that it comprises: - a non-conducting, vertically oriented, coiled spiral heat exchanger tubing open to the surrounding seawater; a circular manifold disposed at the lower end of the heat exchanger, wherein the manifold is supplied with seawater from a motor and pump assembly; - several ascending pipes rising vertically from the circular manifold, angled spaced within the coiled and spiral heat exchanger tubing, and - a nozzle assembly in each rising pipe, wherein the nozzle mouths radially and externally to the periphery of the heat exchanger tubing.