GB2483293A

GB2483293A - Steam flow meter with thermoelectric power source

Info

Publication number: GB2483293A
Application number: GB1014666.0A
Authority: GB
Inventors: Rajan Deep Singh; Benjamin Edward Frisby; Neil Lee Squires
Original assignee: Spirax Sarco Ltd
Current assignee: Spirax Sarco Ltd
Priority date: 2010-09-03
Filing date: 2010-09-03
Publication date: 2012-03-07
Also published as: GB2483369A; GB201115190D0; GB201014666D0

Abstract

An apparatus for measuring the flow of steam through a steam line 16 comprises a flow meter 12 and a power source 14. The power source 14, in use, generates electricity from energy within the steam. The power source may comprise a thermoelectric device and may charge a re-chargeable battery to ensure that the flow meter will operate even if the supply of steam fails.

Description

Field of the Invention

This invention relates to an apparatus for measuring the flow of steam through a steam line and to a steam line having such an apparatus mounted thereon..

Background of the Invention

In order to control most industrial processes involving steam it is necessary to monitor the flow of the steam. This is achieved by using a flow meter. The output of the flow meter is normally relayed to a computer display in a control room which can be a considerable distance from the flow meter itself Typically a power cable and a data cable are associated with each flow meter to supply power to the flow meter and to pass its output to the control room. In a typical industrial plant there can be significant lengths of cable taking power to flow meters and conveying data from the flow meters to the control room. This cable has to be able to withstand the ambient conditions and has to be carefully laid and marked which is a time consuming and expensive process.

Technical Problem The object of the present invention is to reduce the cabling associated with a flow meter for measuring the flow of steam through a steam line.

Prior Art

One of the previous approaches to this problem has been to fit the flow meter with batteries. Depending on the flow meter and the capacity of such batteries the flow meter can typically be relied upon for about a year. However, the batteries do have to be checked and replaced regularly and this can easily be overlooked, particularly if the flow meter is mounted in a location which is relatively difficult to access.

Statements of Invention

One aspect of the present invention provides an apparatus for measuring the flow of steam through a steam line which apparatus comprises a flow meter and a power source therefor, which power source, in use, generates electricity from energy within the steam.

Preferably, the apparatus includes a re-chargeable battery, which can be charged by the power source. This helps ensure that the monitoring device will operate even if the supply of steam fails.

The power source preferably comprises a thermoelectric device which, in use, will provide electrical energy when subject to a temperature differential between the steam and the ambient air.

In a preferred embodiment one side of said thermoelectric device is in thermal communication with a solid base which is mountable on a steam pipe.

In this embodiment another side of said thermoelectric device is in contact with a heat sink via a heat pipe.

Preferably the apparatus comprises a wireless transmitter which, in use, transmits data from the flow meter to a receiver which will typically be located in a control room via relay stations if necessary.

The present invention also provides a steam line having an apparatus in accordance with the present invention mounted thereon.

Although they could conceivably be accommodated in the same physical housing it is envisaged that the flow meter and the power source will comprise separate and distinct unit which are disposed adjacent one another, for example the power source could be mounted on the steam pipe within 10cm to 30cm of the flow meter..

Brief Description of the Drawings

For a better understanding of the present invention and to show how the same may be carried into effect reference will now be made, by way of example, to the accompanying drawing in which:-Fig. 1 is a simplified front view, partly in section, of one embodiment of an apparatus in accordance with the present invention mounted on a steam line; Fig. 2 is a perspective view showing the rear of the apparatus shown in Fig. 1; and Fig. 3 shows the components within the circle III in Figure 1 on an enlarged scale.

Detailed Description of the Preferred Embodiment

Referring to Figure 1 of the drawings there is shown an apparatus for measuring the flow of steam through a steam line. The apparatus, which is generally identified by reference number 10 comprises a flow meter 12 and a power source 14.

The flow meter 12 is mounted in a steam line 16 whilst the power source 14 is clamped to the steam pipe 16 immediately upstream of the flow meter 12. In the embodiment shown the distance between the centre line of the flow meter 12 and the centre line of the power source 14 is about 10 cms.

The flow meter 12, which includes a hollow upstand 18 and a control box 20, comprises a strain gauge and cantilever connected by a spring to a shaft. The shaft is then connected to a cone. As flow increases the drag of the cone bends the cantilever on which the strain gauge rests, which in turn induces strain and communicates with the control box 20 to give a flow output. A wireless transmitter 22 mounted on the control box 20 transmits a signal to a receiver in a remote control room.

Power for the electronics in the control box 20 and the wireless transmitter 22 is provided by a re-chargeable battery 24 which is connected to the power source 14 by a cable housed in an armoured sleeve 26.

The power source 14 comprises an array 28 of thermo electric devices one side of which, in use, is exposed to heat from the steam in the steam line 16 and the other side of which is exposed to the temperature of the ambient air. The array 28 is square and has a ceramic frame 29 around its periphery.

In particular, the power source 14 comprises a solid base 30 which is made from aluminium. The solid base 30 has a concave lower surface which engages and is held tightly against the outer surface of the steam line 16 by a U-bolt 32 arranged as shown. A thermally conductive paste 34 may be placed between the steam line 16 and the solid base 30 at the time of assembly to enhance heat transfer therebetween.

As better shown in Figure 3 the array 28 is sandwiched between the solid base 30 and an upper member 36 which is secured to the solid member 30 by a multiplicity of set screws each of which is made of a material of relatively low conductivity, in this case stainless steel and two of which are shown.

The upper member 36 is made of a thermally conductive material and forms the base of a heat sink which comprises a hollow upstand 38 which accommodates a heat pipe 40 which, in use, transmits heat to a heat exchanger 42 which comprises a multiplicity of discs which are secured to the periphery of the hollow upstand 38 close to its upper extremity.

In use steam at 9 bar and 180°C was passed through steam line 16 in the direction of arrow 50. Heat from the steam passed through the solid base 30 and subjected the bottom of the array 28 of thermoelectric devices to a temperature of around 171°C.

The heat exchanger 42 dissipated heat so that the temperature at the top of the array 28 of thermoelectric devices was approximately 85°C thereby creating a temperature differential of about 86°C across the array 28 of thermo electric devices.

The array 28 of thermoelectric devices 28 generated a current of approximately 1 5rnA at 3.2 volts and continuously trickle charged the re-chargeable battery 24.

For the purposes of our tests the array 28 of thermoelectric devices which we used was a 4Ox4Omm thermoelectric generator model number GM-127-14-16-S purchased from European Thermodynamics Ltd. However, it is envisages that other thermoelectric devices could also be used, for example the high temperature models from TE Technology Inc. Various modifications to the embodiment described are envisaged. For example the flow meter could be a turbine flow meter, a variable area flow meter, a spring loaded variable area flowmeter, a direct in-pipe variable area flow meter, a pitot tube or a vortex shedding flowmeter. Key:

Apparatus 12 Flow meter 14 Power source 16 Steam line 18 Hollow upstand Control box 22 Wireless transmitter 24 Re-chargeable battery 26 Armoured sleeve 28 Array 29 Ceramic frame Solid Base 32 U-bolt 34 Thermally conductive paste 36 Upper member 38 Hollow upstand Heat pipe 42 Heat exchanger 50 Arrow

Claims

Claims: 1. An apparatus for measuring the flow of steam through a steam line (16) which apparatus comprises a flow meter (12) and a power source (14) therefor, which power source (14), in use, generates electricity from energy within the steam.
2. An apparatus as claimed in Claim 1, further comprising a re-chargeable battery (24) which can be charged by the power source (14).
3. An apparatus as claimed in Claim 1 or 2, wherein said power source (14) comprises a thermoelectric device (28) which, in use, will provide electrical energy when subject to a temperature differential between the steam and the ambient air.
4. An apparatus as claimed in Claim 3, wherein one side of said thermoelectric device (28) is in thermal communication with a solid base (30) which is mountable on a steam pipe (16).
An apparatus as claimed in Claim 4, wherein another side of said thermoelectric device is in contact with a heat exchanger (42) via a heat pipe (40).
6. An apparatus as claimed in Claim any preceding Claim, further comprising a wireless transmitter (22) which, in use, transmits data from said flow meter (12) to a receiver.
7. A steam line having with an apparatus as claimed in any preceding claim mounted thereon.
8. A steam line as claimed in Claim 7, wherein said power source (14) is mounted on the steam line (16) within 10cm to 30cm of said flow meter (12).