Installation for measuring the temperature of the external wall of a pipe

Abstract

The invention relates to an installation for measuring the temperature of an external wall of a pipe, the device comprising: a pipe configured to allow the circulation of a fluid; a heat-to-thermoelectricity conversion device, configured to generate a potential difference when there is a temperature difference between an external wall of the pipe and the ambient air; an electronic circuit electrically connected to the heat-to-thermoelectricity conversion device, being configured to extract electrical energy from the potential difference and being configured to measure the temperature of the external wall of the pipe.

Description

Title of the invention: Installation for measuring the temperature of an external wall of a pipeline

[0001] The present invention relates to an installation for measuring the temperature of an external wall of a pipeline.

[0002] Gas supply installations from liquefied products at cryogenic temperature present a particular risk linked to the embrittlement of steel at cryogenic temperatures. Carbon steel, unlike stainless steel alloys, is in fact very fragile at very low temperatures.

[0003] Areas normally in contact with cryogenic products are treated specifically, in particular by using stainless steel. A significant residual risk arises when the product at cryogenic temperature reaches areas where it is not supposed to be. This is particularly the case when the evaporators whose function is to vaporize the cryogenic liquid and raise its temperature to a value close to ambient temperature are covered with a thick layer of frost or ice which are thermal insulators. The problem to be solved is therefore the detection of icing intended to trigger a reheating operation or possibly the closing of a valve to interrupt or reduce the flow of cryogenic product.

[0004] Several devices are known for detecting icing, in particular: - devices based on image analysis with, for example, an analysis of the evolution of the contour by various artificial intelligence methods. These techniques, which can give good results, have the disadvantage of being expensive and not necessarily economically justified, for example, with regard to an electric defrosting system. They are problematic in an industrial environment due to dust, rain and humidity, which can render an optical system inoperative in atmospheric conditions which precisely favor icing; - devices based on a temperature probe placed on the evaporator or the pipeline, the disadvantage of this approach is the need to wire a probe to a system having an input for the supplied signal; - devices based on a valve placed on the gas circuit and closing below a certain temperature. The disadvantage of such a device, apart from its cost, is the fact that it does not allow any anticipation and will purely and simply interrupt the gas supply circuit, without it it is possible to take preventive measures.

[0005] The present invention aims to effectively remedy these drawbacks by proposing an installation for measuring the temperature of an external wall of a pipeline, in particular to detect the presence of a cryogenic fluid in the pipeline, the device comprising: - a pipeline in particular configured to allow the circulation of a fluid; - a device for converting heat into thermoelectricity, such as a Seebeck effect module, the device being configured to generate a potential difference when there is a temperature difference between an external wall of the pipe and the ambient air, the conversion device being for example mounted on the pipe by being in contact by one of its faces with the external wall of the pipe and by being in contact by the other of its faces with a metallic element in heat exchange with the ambient air; - an electronic circuit electrically connected to the heat-to-thermoelectricity conversion device, being configured to extract electrical energy from the potential difference and being configured to measure the temperature of the external wall of the pipe, the electronic circuit being in particular configured to trigger an alarm when the temperature is below a determined temperature threshold.

[0006] Such an invention makes it possible to provide a device which, without wiring or an on-board energy source (battery or battery), can detect the presence of a product at very low temperature, such as a cryogenic liquid, in a pipeline which is not intended for this, which can present risks linked to the embrittlement of steels.

[0007] The presence of a very low temperature makes it possible both to power a device using the Seebeck effect and to measure the temperature. Where appropriate, the collected thermoelectric power makes it possible to transmit one or more low temperature alarms, in particular by radio transmission.

[0008] The invention will be better understood upon reading the following description.

[0009] This provides an installation for measuring the temperature of an external wall. of a pipeline, in particular to detect the presence of a cryogenic fluid in the pipeline.

[0010] This device comprises: - a pipeline in particular configured to allow the circulation of a fluid; - a heat-to-thermoelectricity conversion device, such as a Seebeck effect module, the device being configured to generate a potential difference when there is a temperature difference between an external wall of the pipeline and the ambient air, the conversion device being for example mounted on the pipeline while being in contact by one of its faces with the external wall of the pipeline and being in contact by the other of its faces with a metallic element in heat exchange with the ambient air; - an electronic circuit electrically connected to the heat-to-thermoelectricity conversion device, being configured to extract electrical energy from the potential difference and being configured to measure the temperature of the external wall of the pipe, the electronic circuit being in particular configured to trigger an alarm when the temperature is below a determined temperature threshold.

[0011] The Seebeck effect module makes it possible to provide both a temperature indication, via the Seebeck voltage supplied, and also the energy necessary to power a device ensuring on the one hand the detection of the exceeding of a threshold and on the other hand the transmission of an alarm by radio.

[0012] The Seebeck effect module is installed so as to have one face in thermal contact with the arrival of the very cold fluid, the other face being in contact with a metallic element itself in contact with the ambient air or any structure which can serve as a thermal drain, the thermal resistances are calculated to ensure guaranteed operation in all cases where detection must be carried out, this taking into account both the ambient temperatures, which can be very low in winter, and the risk of icing. The very low temperatures characterizing cryogenic liquids are sufficiently low to ensure that there is always a sufficient temperature differential to supply a Seebeck effect module.

[0013] In the presence of a large temperature difference between its two faces, the Seebeck effect module provides a significant electrical voltage which can reach, for example, 1 to 3 volts; this voltage, compared to a threshold, can be the criterion for switching the instrumentation into an accelerated mode.

[0014] An energy recovery integrated circuit such as the reference integrated circuit "BQ25504" makes it possible to ensure energy recovery with a temperature differential much lower than that characteristic of icing. Such an integrated circuit, like equivalent circuits, also makes it possible, by means of a simple arrangement, to determine the thermoelectric voltage in the absence of load, which is directly proportional to the temperature difference between the cold face and the warm face of the module.

[0015] We can thus, indirectly, measure the temperature of the cold face, knowing that of the warm face.

[0016] Under the same conditions, the module provides sufficient electrical power to supply the electrical circuit ensuring the comparison and also, when the threshold has been crossed, transmission by wire or even by radio transmission. Indeed, even if the electrical power supplied by the Seebeck effect module is modest, the radio transmission is typically of short duration (from a few milliseconds to a few seconds using BLE, SIGFOX or LORa technologies), with a power limited by radio regulations, which means that an energy limited to less than one Joule is more than sufficient to transmit several messages.

[0017] By definition, the Seebeck effect module provides energy based on the temperature difference between the cold source and the warm source.

[0018] The energy supplied therefore tends to decrease when the ambient temperature drops. This could render the system inoperable at very low ambient temperatures.

[0019] This can be limited by implementing the following measures: - taking into account a sufficient safety margin in thermal calculations, which is possible for air gases or hydrogen (but not for CO2) due to the extremely low temperatures involved; and / or - taking into account the temperature of the warm source so that the alarm trigger threshold is compensated according to variations in ambient temperature so that the threshold is constant, without depending on the Seebeck voltage, which will in fact be a function of the ambient temperature.

[0020] The power available at the terminals of a Seebeck module is substantially proportional to the square of the temperature difference between the warm and cold source. This induces both the risk of not having the power necessary to ensure alarm transmission and also the impossibility of having periodic transmission for the purpose of checking the operational nature of the detection device.

[0021] This can be limited by implementing the following measures: - sizing the device to be able to accumulate energy from as small a temperature difference as possible, much lower than the temperature difference symptomatic of significant icing; and / or - control of the radio message transmission period according to the available power, itself a (quadratic) function of the temperature difference between the hot and cold source.

[0022] Seebeck effect modules are now widely available and used in comparable applications, such as thermoelectric module-powered radiator control valves.

[0023] Some devices called "Systems on Chip" or "SOC" integrate on a single silicon chip the capacity to make measurements, including a temperature measurement and a voltage measurement, digital processing and radio transmission. In the case of using LoRa radio technology for transmission, the processor STMicroelectronics' "STM32WL" reference is an example of a processor that can be used to implement the device described.

[0024] Similarly, when using “BLE” radio technology, the STMicroelectronics “STM32WB” reference processor includes both the ability to measure a temperature and transmit a radio message while being able to operate with very low consumption, less than 100 micro watts on average.

[0025] The proposed device makes it possible to very easily put in place a safety element for cryogenic storage, making it possible to prevent in advance a risk of the presence of cryogenic liquid in organs which cannot withstand very low temperatures.

Claims

[Claim 1] Claims Installation for measuring the temperature of an external wall of a pipeline, in particular to detect the presence of a cryogenic fluid in the pipeline, the device comprising: - a pipeline particularly configured to allow the circulation of a fluid; - a device for converting heat into thermoelectricity, such as a Seebeck effect module, the device being configured to generate a potential difference when there is a temperature difference between an external wall of the pipe and the ambient air, the conversion device being for example mounted on the pipe by being in contact by one of its faces with the external wall of the pipe and by being in contact by the other of its faces with a metallic element in heat exchange with the ambient air; - an electronic circuit electrically connected to the heat-to-thermoelectricity conversion device, being configured to extract electrical energy from the potential difference and being configured to measure the temperature of the external wall of the pipe, the electronic circuit being in particular configured to trigger an alarm when the temperature is below a determined temperature threshold.