Subsea Flow Meter

Abstract

A subsea flow meter 100 for determining a flow rate of a flow of fluid through a subsea pipe is disclosed. The flow meter comprises a solid body 102 arranged for attachment to the pipe; a conduit thro

Description

Technical Field The present invention relates to flowmeters, more particularly to subsea flowmeters with temperature sensors which use temperature data to calculate the rate of flow of a fluid through a pipe below the surface of the sea. It also relates to methods of performing these calculations. Background Offshore pipes are used beneath the surface of the sea, for example on the seabed, to transport various types of fluids. This can include the transport of fluids such as oil, gas and water from a source, as well as transportation to or from a storage facility. More recently, there has also been interest in capturing carbon dioxide and storing it under the sea (“offshore carbon capture and storage”) in order to offset carbon emissions. This typically involves pumping gaseous or liquid carbon dioxide from the surface to a reservoir on the seabed, via subsea pipes. In each of these applications, there is a need to quantify the amount of substance being transported, and more specifically to calculate the rate of flow of fluid through the pipes. In order to measure the rate of flow of a fluid through a pipe, various types of flow meters are used. Some flow meters provide regions of different fluid pressures, e.g. by providing a constriction in the flow path, and sense the difference in pressure between the two regions in order to determine the rate of flow of the fluid. However, other properties of the fluid also need to be determined in order to perform this calculation. For example, whilst certain properties of the fluid may be known, the temperature of the fluid as it flows through the pipe needs to be actively measured in order to accurately calculate the flow rate. Subsea pipes are normally situated in remote locations under the sea, and surrounded by seawater. Therefore, there are various technical challenges associated with accurately and cost effectively measuring the flow rate and temperature of fluid flowing through them. For example, it may be difficult to measure the temperature at the same location and using the same device as that which is used to measure the differential pressure. In addition, if 14 02 24 a temperature sensor is introduced into the flow path of the pipe, this may obstruct the flow of the fluid. Summary of Invention Embodiments of the present invention aim to address at least some of the above problems. In an aspect there is provided a subsea flow meter for determining a flow rate of a flow of fluid through a subsea pipe, the flow meter comprising: a solid body arranged for attachment to the pipe; a conduit through the solid body arranged to provide a flow path for said flow of fluid, for measurement of the flow rate; a non-wetted temperature sensor disposed in the solid body and arranged to sense a temperature of the solid body; a pressure sensor configured to sense a differential pressure of the fluid flowing through the conduit, and for example a static line pressure of said fluid; and a calculator arranged to obtain an indication of the ambient temperature outside of the solid body, an indication of the sensed temperature, and an indication of the sensed differential pressure; and to determine the temperature of the fluid in the pipe based on the sensed temperature and the indication of ambient temperature. The calculator may be configured to determine the temperature of the fluid based on the difference between the sensed temperature and the indicated ambient temperature. The flowmeter may further comprise a second temperature sensor positioned externally of the solid body and may be arranged to provide the indication of ambient temperature to the calculator. The second temperature sensor may be configured to sense the temperature of electronics of the subsea flow meter, and provide the indication of the ambient temperature based on the sensed temperature of the electronics. The non-wetted temperature sensor is arranged not to contact and / or obstruct the fluid flow. The subsea flow meter may further comprise a housing coupled to the solid body, wherein the temperature sensor is positioned within the housing. The housing may comprise a thermowell which surrounds the temperature sensor or a portion of it. The housing may be configured to seal the temperature sensor. The housing may provide or define a cavity in which the temperature sensor or a portion of the temperature sensor is positioned. The housing, e.g. the cavity, may contain (e.g. be filled with) an inert fluid, which may be a liquid ora gas. The inert fluid may be nitrogen gas. The inert fluid may be an oil such as silicone oil. The housing may comprise a port e.g. an opening for purging and / or introducing and / or removing the inert fluid to or from the housing. The housing may be configured to inhibit the ingress of water to the temperature sensor. The housing may be sealed against the solid body. The temperature sensor may be mechanically coupled to the housing via at least one coupling member. The at least one coupling member may comprise a resilient coupling member and / or it may comprise a rigid coupling member. The coupling member may be arranged to couple the housing to the temperature sensor to provide a radial spacing between the temperature sensor and the outer surface of the solid body. The temperature sensor may extend (e.g. within a part of the housing such as a thermowell) from a first end radially external to the solid body, to a second end disposed in the solid body. The temperature sensor may be connected to the calculator at the first end, and may be configured to sense a temperature of the solid body adjacent to the second end. The temperature sensor may comprise a detecting rod which extends to a tip disposed in the solid body, for sensing a temperature of the solid body adjacent to the tip. The solid body may comprise an indentation on its outer surface for accommodating the temperature sensor. The indentation may comprise a notch in which the temperature sensor is seated. For example, the housing of the temperature sensor may be seated in the notch. The solid body and / or the indentation of the solid body may comprise a hole into which the temperature sensor, e.g. the detecting rod, protrudes. The temperature sensor may comprise a temperature transmitter arranged to transmit an indication of a detected temperature to the calculator. The temperature sensor may be electrically coupled to the calculator via a connector, and the connector may be mechanically coupled to the housing. The conduit may comprise a first section having a first diameter, and a second section having a second diameter smaller than the first diameter. The temperature sensor may be longitudinally aligned with the second section. Alternatively the temperature sensor may 06 03 24 be longitudinally aligned with the second section. The flow pressure may be measured at a first point in the first section and a second point in the second section. The temperature sensor may be longitudinally positioned between the first point and the second point, or upstream of the first point and the second point, or downstream of the first point and the second point. The conduit may comprise or be in the form of a venturi tube, e.g. the solid body may define a venturi tube. The pressure sensor and the calculator may be provided in a common housing, for example as part of the same integrated unit. The temperature sensor may be electrically connected to the calculator via (e.g. through) a glass-to-metal seal. The temperature sensor may be connected (e.g. mechanically and / or electrically) to the calculator via an oil filled hose. For example, an electrical connection between the temperature sensor and the calculator may be provided through the hose. The calculator may be provided as part of a pressure sensor unit. The temperature sensor may be connected (mechanically and / or electrically) to the calculator via a metal tube. The calculator may comprise an electrical input. An electrical connector, e.g. one or more wires, may be provided between the temperature sensor and the electrical housing. The temperature sensor, the electrical input and the electrical connector may be provided in a common housing, for example in a single cavity, which may contain (e.g. be filled) with an inert fluid such as those described above. In another aspect there is provided a method of calculating the rate of flow of fluid through a subsea pipe, the computer-implemented method comprising: obtaining a first temperature signal indicating the temperature of a subsea solid body, wherein the solid body surrounds a conduit of a flow meter to which the subsea pipe is attached and through which the fluid is flowing; obtaining a second temperature signal indicating the ambient temperature outside the flow meter; obtaining a differential pressure value of the fluid flowing through the conduit; determining the temperature of the fluid in the conduit based on the first temperature signal and the second temperature signal; determining the rate of flow of the fluid in the pipe based on the determined temperature and the differential pressure value. A computer program product may comprise instructions which, when the program is executed by a computer, cause the computer to carry out the method. Brief Description of Figures Some examples of the present disclosure will now be described, by way of example only, with reference to the figures, in which: Figure 1 shows a schematic cross-sectional view of an example subsea flow meter; Figure 2 shows an example temperature sensor, for use in a subsea flowmeter; Figure 3 shows another example of a temperature sensor for use in a subsea flow meter; Figure 4 shows a further example of a temperature sensor for use in a subsea flow meter; Figure 5 illustrates an example method. In the drawings like reference numerals are used to indicate like elements. Specific Description The present disclosure relates to a subsea flow meter that includes a non-wetted temperature sensor. The temperature sensor enables the temperature of the body of the flow meter to be measured without the need to interrupt the flow of fluid. Based on this data, a value for the temperature of the fluid can be determined, which can be combined with obtained pressure data to determine the rate of flow of the fluid through a subsea pipe to which the flowmeter is attached. The temperature sensor is included as part of the flow meter, which may avoid the need to obtain an indication of the fluid temperature from other external sources, and allow the flow rate to be determined based on measurements from a single device. It may also enable the temperature of the fluid to be sensed without obstructing the fluid flow. Figure 1 shows a schematic cross-sectional view of an example subsea flow meter 100. The flow meter 100 is arranged for connection to a subsea pipe (not shown) in order to determine the flow rate of fluid in the pipe. The flow meter 100 includes a solid body 102 which surrounds a conduit 104. Both ends of the flow meter are arranged to be attached to a pipe or sections of a pipe, so that fluid flowing through the pipe enters the flow meter 100 at one end and flows through the conduit 104 to the other end where it exits the flow meter. The flow meter 100 includes a pressure drop provider, which, in the example shown in Figure 1, takes the form of a venturi tube. In particular, the solid body 102 and conduit 104 are arranged to provide a constriction (a section with a reduced diameter) in a central portion (B) of the conduit 104. This causes the flow of fluid to have a greater relative velocity at the constriction (B), than at the wide section (A) - where the diameter of the conduit 104 at A is substantially the same as that of the pipe to which the flow meter 100 is attached. The increase in velocity in turn means that the static line pressure of the fluid flow at the constriction to be lower than it is at wider section A (and the pipe). The flow meter 100 further comprises a pressure sensor 106, arranged to sense the stati c line pressure of the fluid in the conduit 104. Specifically, the pressure sensor 106 is arranged sense the differential pressure between constriction B and wider section A, as well as the line pressure at the constriction B and at the wider section A. In particular, at each of points A and B a small hole is provided, e.g. drilled, in the flow meter body 102, which transmits the pressures up to a pressure sensing diaphragm. In this way the differential pressure between points B and A can be determined, as well as the static line pressure of the fluid and point A and / or point B. The pressure sensor 106 is also arranged to provide a signal indicating the sensed fluid pressure(s) to a flow calculator 110. Although in Figure 1 the pressure sensor 106 is shown to sense the line pressure at two points in the conduit A and B, it will be appreciated that additional elements may be provided in order to sense the line pressure at additional points in the conduit 104. For example, a plurality of sensor arrangements may be positioned around the circumference of the conduit 104. The flowmeter further comprises a temperature sensor 108. The temperature sensor 108 is non-wetted, that is, it is not positioned in the conduit itself and so does not sense the temperature of the fluid flow directly. Instead, the temperature sensor 108 arranged (at least partially) in the solid body 102 and is configured to sense a temperature of the solid body 102. The temperature sensor 108 is also configured to provide a signal indicating of the sensed temperature sensor to the flow calculator 110. As shown in Figure 1, the temperature sensor 108 is aligned with the constriction of the conduit 104 (the section with a reduced diameter in a central portion (B) of the conduit 104). However, in other examples the temperature sensor may be arranged in other sections of the tube, e.g. it may be aligned with the wider portion, or at any point along the length of the conduit 104, or even outside of the region in which the pressure is sensed. The temperature sensor 108 is coupled to the flow calculator 110 and / or the pressure sensor 106 by a connector 112. The structure and function of different example temperature sensors is described in more detail below, with reference to Figures 2 to 4. The flow calculator 110 is configured to determine a temperature of the fluid in the conduit 104 (also known as the process temperature), based on the temperature signal obtained from the temperature sensor 108. In particular, the flow calculator 110 may also receive an indication of the ambient temperature, and use this temperature in conjunction with the obtained temperature signal from the temperature sensor 108 (which indicates a temperature of the solid body 102) to determine the temperature of the fluid in the conduit itself. The flow calculator 110 is arranged externally of the solid body and is in thermal equilibrium with the surrounding seawater. The flow calculator may therefore comprise its own internal temperature sensor for sensing the ambient temperature. This internal temperature sensor may be provided within the electronics of the flow calculator 110 and / or the pressure sensor 106, e.g. as part of the transmitter electronics. Without wishing to be bound by theory, the flow calculator 110 may be configured to determine the temperature of the fluid in the conduit (process temperature) according to the relationship: Tp = k(Tm — Ta) + Ta Where: TP is the process temperature Tm is the temperature measured by the temperature sensor 108 Ta is the ambient temperature, e.g. as measured by the flow calculator’s internal temperature sensor k is a predetermined coefficient corresponding to a measure of how closely the temperature measured by the temperature sensor 108 tracks the process temperature. The flow calculator 110 is also configured to calculate a flow rate of the fluid in the pipe based on the obtained pressure and temperature signals. It will be appreciated that although shown separately in Figure 1, in some examples, the pressure sensor 106 and the flow calculator 110 may be integrated into a single unit. For example, the flow calculator 110 may be a processor of the pressure sensor 106 or vice versa, and / or the pressure sensor 106 and flow calculator 110 may be provided within a shared housing. E-d2 2 * fluiddensity * &P The flow calculator 110 may be configured to use the calculated process temperature, the sensed line pressure and differential pressure, and stored values, to calculate the flow rate according to the equation: where: • qm is the mass flow rate. • C is the discharge coefficient of the pressure drop provider (e.g. the venturi tube of flow meter 100). 1 • is the velocity of approach factor, and / ? is the ratio of the smaller diameter (at B) to the larger diameter (at A). • c is the expansibility for the pressure drop provider. • d is the diameter of the pressure drop provider. • AP is the measured differential pressure across the pressure drop provider. The calculated process temperature is used in the determination of the above fluid density and p factor. The flow calculator 110 is configured to provide at least one output signal 114 to a user terminal, e.g. at the surface. The signals may indicate at least one of the calculated flow rate, calculated flow temperature, the calculated differential pressure, and the measured pressure and temperature values. Diagnostic signals, e.g. which may indicate an error or the proper functioning of the flow meter and / or its constituent components may also be provided. With reference to Figures 2 to 4, some examples of temperature sensors 108 will now be described in more detail. Figure 2a illustrates a cross sectional view of a first example of a temperature sensor 300 mounted on a solid body 102 of a flow meter, such as the flow meter 100 described above with reference to Fig. 1. The temperature sensor 300 includes a housing 302 which is coupled to the solid body 102 via coupling means 304. The coupling means 304 may comprise resilient and / or rigid coupling members, for example it may be a screw (e.g. an M6 cap head screw) as shown in Figure 2a. The housing 302 includes an integral thermowell which protrudes into a hole in the solid body 102, from the outer surface of the solid body 102 towards the conduit in the centre of the flow meter (not shown). The thermowell surrounds a temperature detector 306 (e.g. a resistance temperature detector), which also protrudes into the solid body 102. In the example shown in Fig. 2a, the temperature detector 306 has a diameter of 6mm. The temperature detector 306 is electrically coupled to a temperature transmitter 308, which is mechanically coupled to the housing, e.g. via further screws as shown. The temperature transmitter 308 is arranged to transmit a signal indicating a temperature to another device, e.g. a calculator such as the flow calculator 110. At least a portion of the temperature sensor 300, e.g. the transmitter 308, is arranged in a first cavity 310 within the housing 302. The first cavity 310 is filled with an inert fluid, such as nitrogen gas N2 or silicone oil. The housing 302 is coupled, e.g. screwed as shown, into an oil-filled connector assembly, via a connector 320. The temperature sensor 300 is electrically connected to the connector 320 via electrical connections provided through a glass-to-metal seal 314 (e.g. a 6-pin glass to metal seal). The housing of the connector 312 defines a second cavity 316 which is in fluid communication with the rest of the oil-filled connector assembly, which is filled with an inert fluid such as silicone oil. A fill port 318 is provided via which the oil can be introduced into the second cavity 316 and the rest of the oil-filled assembly. Figure 2b shows the temperature sensor 300 and a portion of the oil-filled connector assembly in plan view. The section denoted as Y-Y indicates the sectional view shown in Figure 2a. Figure 2b shows the connector 320 mechanically coupled to a hose 330. The end of hose 330 proximal to the temperature sensor 300 is surrounded by a bend restrictor 332, which may be formed of a stiffer material than the hose 330 and arranged to inhibit bending of the hose 330 proximal to the temperature sensor 300. The oil-filled connector assembly provides an electrical connection between the temperature sensor 300 and a unit (not shown) which includes the flow calculator. For example, the unit may include the flow calculator and the pressure sensor. In this way a signal indicative of the temperature sensed by the temperature sensor can be provided to the flow calculator. Figure 3 illustrates a cross sectional view of another example temperature sensor 400 mounted on a solid body 102 of a flow meter, such as the flow meter 100 described above with reference to Fig. 1. This example temperature sensor 400 shares several similarities with the first example sensor 300. For example, as described above with reference to Figure 2a, the temperature sensor includes a detector 306 which protrudes into a solid body 102 for sensing the temperature of the body 102, and is connected to transmitter 308. The temperature sensor also includes a housing 402 which is coupled to the solid body 102 via coupling means 304. The temperature transmitter 308 is coupled to the housing 402, and the housing 402 is also coupled to a connector 412 via further coupling means. The temperature sensor 400 is seated within an indentation on the surface of the solid body 102. In particular the housing 402 of the temperature sensor 400 is secured to the solid body 102 within the indentation e.g. a notch. The temperature transmitter 308 is positioned within an inert cavity 410 within the housing 402, for example the cavity 410 may be filled with an inert fluid such as nitrogen gas or silicone oil. The cavity 410 is in fluid communication with a first end of a conduit 420 through the connector 412. The conduit 420, or at least a section thereof (such as a first section proximal to the cavity 410 which extends in the direction away from the solid body 102) may have a width of around 18mm. The conduit 420 comprises a corner or bend, e.g. a right angle bend, and extends to an opening on a side face of the cap 412. A second section of the conduit 420 downstream of the bend may have a diameter less than the first section. The connector 412 is coupled, e.g. welded, to an instrument tube 430, such that the cavity 410, the conduit 420 and a lumen of the instrument tube 430 are in fluid communication with each other. The connector412 further comprises a port 418 which is operable to fill the cavity and conduit with an inert fluid such as nitrogen gas. At its second end, the conduit 420 is in fluid communication with the lumen of the instrument tube 430. An end of the tube 430 is seated in the housing of the cap 412, e.g., in a notch at the second end of the conduit 420. The notch may extend approximately e.g. 10mm in from the edge of the cap housing, to enable the tube to extend a corresponding distance into the housing. The instrument tube 430 may be made of metal and welded to the housing of the connector 430, e.g. via a socketweld 432. In the example shown in Figure 4, the instrument tube 430 has an outer diameter 12mm, and an inner diameter of 8mm, although it will be understood that these values are merely exemplary. The other end of the instrument tube 430 (not shown) is connected to a unit containing the flow calculator. The unit may include the both the flow calculator and the pressure sensor. The instrument tube further provides an electrical connection between the temperature sensor 400 and the flow calculator. In this way a signal indicative of the temperature sensed by the temperature sensor can be provided to the flow calculator. Figure 4 illustrates a cross sectional view of another example temperature sensor 500 mounted on a solid body 102 of a flow meter. The temperature sensor 500 shares some similarities with the temperature sensors described above with reference to Figures 2 and 3. However, in this example the temperature sensor 500 is integral with the differential pressure sensor, e.g. they are provided in a common unit or housing. The unit may also contain the flow calculator. The temperature sensor 500 comprises a housing 502, a temperature detector 306 protruding into the solid body 102, and a temperature transmitter 308, arranged and coupled together substantially as described above with reference to figures 2 and 3, for sensing a temperature of the flow meter body. The housing 502 of the temperature sensor 500 forms a part of the housing of a larger integrated unit, which includes a pressure sensor unit 540 and an input-output connection 530. The housing 502 of the temperature sensor is coupled to corresponding housing of the pressure sensor unit 540 and the input-output connection 550 via connecting housing 530. The housing defines a cavity 510 in which the temperature sensor is provided. The cavity 510 can be filled with an inert material. For example, the cavity 510 can be purged with nitrogen gas, or filled with oil such as silicone oil, via a port (not shown) as described above with reference to the apparatus of figures 2 and 3. The pressure sensor unit 540 includes a pressure sensor and a flow calculator for determining the rate of flow of fluid through the pipe as described above. The temperature sensor 500 is electrically connected to the pressure sensor unit 540 and thereby to the flow calculator via an electrical connector 522 and a glass-to-metal seal 520. The pressure sensor unit 540 is also electrically coupled to the input-output connector 550 via electrical connectors 524, 526. The pressure sensor unit 540 is arranged to provide signals indicating the measured temperature and pressure values and the calculated flow rate to the input-output connector 550. The input-output connector 550 is arranged to provide this data to a user interface, e.g. at the surface. The input-output connector is also arranged to receive signals, such as control signals, from such a user interface and provide them to the pressure sensor unit 540. Figure 5 is a flowchart which illustrates an example method 10 of calculating the rate of fluid through a subsea pipe. Such a method may be performed by one of the flow calculators described above. The method comprises, at a first step 11 obtaining a first temperature signal indicating the temperature of a subsea solid body, wherein the solid body surrounds a conduit of a flow meter to which the subsea pipe is attached and through which the fluid is flowing. A next step 12 comprises obtaining a second temperature signal indicating the ambient temperature outside the flow meter. A further step 13 comprises obtaining a static line pressure and a differential pressure value of the fluid flowing through the conduit. The method further comprises determining 14 the temperature of the fluid in the conduit based on the first temperature signal and the second temperature signal. As a final step, the method comprises determining 15 the rate of flow of the fluid in the pipe based on the determined temperature and the indication of static line pressure and differential pressure. For example the determination of the temperature of the fluid and the determination of the rate of flow of fluid in the pipe may be achieved using the temperature and mass flow equations described above. The steps of the method 10 may be performed in a different order from that shown in Figure 5. For example, obtaining a pressure value 14 may be performed before one or both temperature measurements 11 and 12. The measurement of the ambient temperature may be performed before the other steps of the method 10, and for example a value of the ambient temperature may be stored. Determining the temperature of the fluid 14 may be performed before obtaining a static line pressure ora differential pressure value 13. The method 10 and / or any of the steps of the method may be performed periodically or continuously, and each step of the method may be performed concurrently. Although in each of the examples above the temperature sensor has been described as including a temperature transmitter, it will be appreciated that this component is not essential. For example, in some examples the temperature detectors described are directly connected to the remaining circuitry. Although the flow meter of figure 1 is described as including a venturi tube, it will be appreciated that in other examples other forms of pressure drop providers are envisaged, e.g. orifice or cone. Other types of flow meter, aside from the pressure-based meters described are also envisaged. For example, the temperature sensor could also be implemented with other types of flowmeters including but not limited to ultrasonic, turbine and Coriolis flow meters. It will be appreciated from the discussion above that the examples shown in the figures are merely exemplary, and include features which may be generalised, removed or replaced as described herein and as set out in the claims. With reference to the drawings in general, it will be appreciated that schematic functional block diagrams are used to indicate functionality of systems and apparatus described herein. In addition, the processing functionality may also be provided by devices which are supported by an electronic device. It will be appreciated however that the functionality need not be divided in this way, and should not be taken to imply any particular structure of hardware other than that described and claimed below. The function of one or more of the elements shown in the drawings may be further subdivided, and / or distributed throughout apparatus of the disclosure. In some examples the function of one or more elements shown in the drawings may be integrated into a single functional unit. As will be appreciated by the skilled reader in the context of the present disclosure, each of the examples described herein may be implemented in a variety of different ways. Any feature of any aspects of the disclosure may be combined with any of the other aspects of the disclosure. For example, method aspects may be combined with apparatus aspects, and features described with reference to the operation of particular elements of apparatus may be provided in methods which do not use those particular types of apparatus. In addition, each of the features of each of the examples is intended to be separable from the features which it is described in combination with, unless it is expressly stated that some other feature is essential to its operation. Each of these separable features may of course be combined with any of the other features of the examples in which it is described, or with any of the other features or combination of features of any of the other examples described herein. Furthermore, equivalents and modifications not described above may also be employed without departing from the invention. Certain features of the methods described herein may be implemented in hardware, and one or more functions of the apparatus may be implemented in method steps. It will also be appreciated in the context of the present disclosure that the methods described herein need not be performed in the order in which they are described, nor necessarily in the order in which they are depicted in the drawings. Accordingly, aspects of the disclosure which are described with reference to products or apparatus are also intended to be implemented as methods and vice versa. The methods described herein may be implemented in computer programs, or in hardware or in any combination thereof. Computer programs include software, middleware, firmware, and any combination thereof. Such programs may be provided as signals or network messages and may be recorded on computer readable media such as tangible computer readable media which may store the computer programs in non-transitory form. Hardware includes computers, handheld devices, programmable processors, general purpose processors, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), and arrays of logic gates. Other examples and variations of the disclosure will be apparent to the skilled addressee in the context of the present disclosure.

Claims

1. A subsea flow meter for determining a flow rate of a flow of fluid through a subsea pipe the flow meter comprising:a solid body arranged for attachment to the pipe;a conduit through the solid body arranged to provide a flow path for said flow of fluid, for measurement of the flow rate;a non-wetted temperature sensor disposed in the solid body and arranged to sense a temperature of the solid body;a pressure sensor configured to sense a differential pressure of the fluid flowing through the conduit; anda calculator arranged to obtain:an indication of the ambient temperature outside of the solid body, an indication of the sensed temperature, andan indication of the sensed differential pressure;and to determine the temperature of the fluid in the pipe based on the sensed temperature and the indication of ambient temperature.

2. The subsea flow meter of any preceding claim, wherein the calculator is configured to determine the temperature of the fluid based on the difference between the sensed temperature and the indicated ambient temperature.

3. The subsea flow meter of claim 2, further comprising a second temperature sensor positioned externally of the solid body and arranged to provide the indication of ambient temperature to the calculator.

4. The subsea flow meter of claim 3, wherein the second temperature sensor is configured to sense the temperature of electronics of the subsea flow meter, and provide the indication of the ambient temperature based on the sensed temperature of the electronics.

5. The subsea flow meter of any preceding claim, further comprising a housing coupled to the solid body, wherein the temperature sensor is positioned within the housing.

6. The subsea flow meter of claim 5, wherein the housing is configured to seal the temperature sensor.

7. The subsea flow meter of claim 6, wherein the housing contains an inert fluid.

8. The subsea flow meter of any of claims 5 to 7, wherein the housing is configuredto inhibit the ingress of water to the temperature sensor.

9. The subsea flow meter of any of claims 5 to 8, wherein the temperature sensor is mechanically coupled to the housing via at least one coupling member.

10. The subsea flow meter of claim 9, wherein the at least one coupling member comprises a resilient coupling member.

11. The subsea flow meter of claim 9 or 10, wherein the at least one coupling member comprises a rigid coupling member.

12. The subsea flow meter of any of claims 5 to 9, wherein the temperature sensor extends from a first end at which the sensor is connected to the calculator, to a second end disposed in the solid body, for sensing a temperature of the solid body adjacent to the tip.

13. The subsea flow meter of any preceding claim, wherein the solid body comprises an indentation on its outer surface for accommodating the temperature sensor.

14. The subsea flow meter of claim 13, wherein the indentation comprises a notch in which the temperature sensor is seated.

15. The subsea flow meter of any preceding claim, wherein the temperature sensor comprises a temperature transmitter arranged to transmit an indication of a detected temperature to the calculator.

16. The subsea flow meter of any preceding claim, wherein the temperature sensor is06 03 24electrically coupled to the calculator via a connector, and wherein the connector is mechanically coupled to the housing.

17. The subsea flow meter of any preceding claim, wherein the conduit comprises a 5 first section having a first diameter, and a second section having a second diameter smaller than the first diameter.

18. The subsea flow meter of claim 17, wherein the temperature sensor is longitudinally aligned with the second section.1019. The subsea flow meter of any preceding claim, wherein the pressure sensor and the calculator are provided in a common housing.

20. The subsea flow meter of any preceding claim, wherein the temperature sensor is 15 electrically connected to the calculator via a glass-to-metal seal.

21. The subsea flow meter of any preceding claim, wherein the temperature sensor is connected to the calculator via an oil filled hose.20 22. The subsea flow meter of any of claims 1 to 21, wherein the temperature sensor is connected to the flow meter via a metal tube.

23. The subsea flow meter of any of claims 1 to 22, wherein the calculator comprises an electrical input, wherein an electrical connector is provided between the temperature 25 sensor and the electrical housing, and wherein the temperature sensor, the electrical input and the electrical connector are provided in a common housing.

24. A computer-implemented method of calculating the rate of flow of fluid through a subsea pipe, the method comprising:30 obtaining a first temperature signal indicating the temperature of a subsea solid body, wherein the solid body surrounds a conduit of a flow meter to which the subsea pipe is attached and through which the fluid is flowing;obtaining a second temperature signal indicating the ambient temperature outside the flow meter;CMobtaining a differential pressure value of the fluid flowing through the conduit;determining the temperature of the fluid in the conduit based on the first temperature signal and the second temperature signal;determining the rate of flow of the fluid in the pipe based on the determined5 temperature and the differential pressure value.

25. A computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method of claim 24.

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