Calorimeter
阅读说明:本技术 量热仪 (Calorimeter ) 是由 阿尔夫-贝恩德·阿姆波斯 于 2019-02-25 设计创作,主要内容包括:本发明涉及改进量热技术领域。本发明特别是提出一种量热仪(1),其具有压力容器(2),该压力容器设有应变计(8)。本发明的目的在于通过执行量热测量期间压力容器(2)的变形至少间接推断出压力容器(2)内的内压。(The invention relates to the technical field of improved calorimetry. The invention proposes, in particular, a calorimeter (1) having a pressure vessel (2) which is provided with a strain gauge (8). The aim of the invention is to at least indirectly infer the internal pressure in the pressure vessel (2) by deformation of the pressure vessel (2) during the execution of calorimetric measurements.)
1. Calorimeter (1) for determining the calorific value of a sample (4), wherein the calorimeter (1) has a pressure vessel (2) and an digestion vessel (3) arranged in the pressure vessel (2) for accommodating the sample (4),
it is characterized in that the preparation method is characterized in that,
the calorimeter (1) has at least one strain gauge (8) which is arranged at least indirectly on the pressure vessel (2) and can determine the pressure-induced deformation of the pressure vessel (2).
2. The calorimeter (1) according to claim 1, characterised in that the calorimeter (1) has a shut-off device (18a) which prevents the use and/or the continued use of the calorimeter (1) when it is concluded, in particular using the at least one strain gauge (8), that the pressure vessel (2) is overloaded, and/or when a pressure limit value is exceeded, and/or when it is concluded that an inadmissible deformation of the pressure vessel (2) has occurred.
3. The calorimeter (1) according to claim 1 or 2, characterized in that the at least one strain gauge (8) is arranged on an outer side (9) of the pressure vessel (2) facing away from the digestion vessel (3).
4. The calorimeter (1) according to any one of claims 1 to 3, wherein the at least one strain gauge (8) is arranged directly at the pressure vessel (2); or the strain gauge (8) is arranged on a holding means, in particular a holding plate, placed on the pressure vessel (2).
5. The calorimeter (1) according to any one of claims 1 to 4, characterised in that the calorimeter (1) has a measurement circuit (10) by means of which the temperature error of the at least one strain gauge (8) can be compensated.
6. Calorimeter (1) according to one of claims 1 to 5, characterised in that the measurement circuit (10) comprises at least one strain gauge (8) and at least one second strain gauge (11), in particular a temperature-compensated strain gauge (11), wherein the at least one second strain gauge (11) is connected to the pressure vessel (2) in order to allow heat transfer from the pressure vessel (2) to the at least one second strain gauge (11) without the at least one second strain gauge (11) experiencing a compressive load and/or a change in length.
7. The calorimeter (1) according to claim 6, wherein the measurement circuit (10) is configured to output a measurement value representative of the pressure in the pressure vessel (2); and/or the at least one strain gauge (8) and the at least one second strain gauge (11) are the same strain gauge.
8. Calorimeter (1) in accordance with one of claims 1 to 7, characterised in that the pressure vessel (2) is made of a material that conducts heat well, in particular aluminium.
9. The calorimeter (1) according to any one of claims 1 to 8, wherein the calorimeter (1) has at least one temperature sensor (14) arranged within the pressure vessel (2).
10. The calorimeter (1) according to any one of claims 1 to 9, characterised in that the calorimeter (1) has a control unit (18) which prevents operation of the calorimeter (1) when an impermissible deformation, in particular a plastic deformation, of the pressure vessel (2) is detected using the at least one strain gauge (8) and/or using the measuring circuit (10).
11. The calorimeter (1) according to any one of claims 1 to 10, wherein the pressure vessel (2) has an inflow (12) through which the pressure vessel (2) can be filled with a liquid, in particular water (7), and an overflow (13), wherein at least a liquid sensor (13a) is arranged in the overflow (13) or a liquid sensor (12a, 13a) is arranged in the overflow (13) and in the inflow (12), respectively.
12. The calorimeter (1) according to any one of claims 1 to 11, characterised in that the calorimeter (1) has an information output device (19), in particular a display device, by means of which information about the calorimetric measurements and/or the state of the calorimeter (1), in particular of its pressure vessel (2), can be output.
Technical Field
The invention relates to a calorimeter for determining the calorific value of a sample, comprising a pressure vessel and an digestion vessel arranged therein for accommodating the sample.
Background
Disclosure of Invention
In view of the above, the object of the present invention is to provide a calorimeter of the aforementioned type, the operation of which is simplified and which allows tests to be carried out as required, possibly with replacement of the pressure vessel as appropriate. With respect to the aforementioned type of calorimeter, the solution of the invention to achieve the above object comprises the means and features described in the independent claims for such a calorimeter. In order to achieve the stated object, the invention proposes, in particular, a calorimeter having a strain gauge which is arranged at least indirectly on the pressure vessel and by means of which strain gauge the pressure-induced deformation of the pressure vessel can be determined. Preferably, in addition to the pressure-induced deformation of the pressure vessel, the pressure within the pressure vessel may also be determined at least indirectly or indirectly by means of the at least one strain gauge.
In this way, the pressure vessel can be monitored during the calorimetric measurement. Based on the pressure-induced deformation of the pressure vessel, the pressure within the pressure vessel may be inferred, at least indirectly. Once the maximum allowable pressure in the vessel and/or the maximum allowable deformation of the vessel is exceeded, there is a fear of damage to the pressure vessel, it can be concluded that continued use of the pressure vessel on the calorimeter is not permitted, testing needs to be performed, and the pressure vessel needs to be replaced if necessary.
In this connection, it is conceivable for the calorimeter to have a shut-off device which organizes the use and/or the continued use of the calorimeter, in particular of the pressure vessel, when an overload of the pressure vessel is detected, in particular using at least one strain gauge, and/or when a pressure limit value is exceeded, and/or when an inadmissible deformation of the pressure vessel is detected. The cut-off device can be connected to the at least one strain gauge and output a blocking signal, which for example prevents the ignition device of the calorimeter from continuing to ignite, depending on the corresponding signal from the at least one strain gauge. The shut-off device can be part of the control unit of the calorimeter or be connected to the control unit of the calorimeter on the basis of signal technology.
As soon as an overload of the pressure vessel due to an overpressure or an inadmissible deformation is detected, the calorimeter can be prevented from further operation with the overloaded pressure vessel by means of the shut-off device and/or the control unit of the calorimeter.
A particular advantage of the calorimeter according to the invention is that, by means of the at least one strain gauge, it is also possible to easily ascertain the plastic deformation of the pressure vessel. Once the plastic deformation of the pressure vessel is ascertained by means of the at least one strain gauge, it can be ascertained that the plastically deformed pressure vessel is no longer suitable for further calorimetric measurements. Before this, the plastically deformed pressure vessel should first be checked at least for its further load capacity and, if necessary, should even be replaced.
In general, the calorimeter according to the invention provides a possible solution: even if the pressure vessel has not actually been overloaded, the inspection is carried out first and the pressure vessel is replaced as appropriate, instead of after a certain number of calorimetric measuring processes.
The calorimeter according to the invention has the advantage here in respect of its at least one strain gauge that it is not even necessary to preset specific pressure limit values which should not be exceeded. As soon as an inadmissible deformation, for example a plastic deformation, of the pressure vessel is detected by means of the at least one strain gauge, the pressure vessel is checked and, if appropriate, replaced.
In this case, for example, the shut-off device and/or the control unit of the aforementioned calorimeter can prevent the further operation of the calorimeter in the event of an inadmissible or permanent deformation of the pressure vessel.
In a particularly advantageous embodiment, at least one strain gauge for determining the pressure can be arranged on the outside of the pressure vessel facing away from the digestion vessel. In this way, the strain gauge does not directly touch the liquid filled in the pressure vessel during operation of the calorimeter, and therefore it is not necessary to protect it from the liquid by special measures.
At least one strain gauge for determining the deformation of the pressure vessel and at least for indirectly determining the pressure may preferably be arranged directly on the pressure vessel. This makes it possible to transmit the pressure-induced deformation of the pressure vessel to the at least one strain gauge particularly easily and reliably. However, it is also possible for the strain gauges not to be arranged directly on the pressure vessel, but on a holding means which is connected to the pressure vessel, so that mechanical loads on the holding means, which are caused by the pressure vessel being subjected to mechanical and pressure-induced loads, can also be transmitted to the at least one strain gauge for determining the pressure. Such a holding mechanism may be, for example, a holding plate.
It may be advantageous that the at least one strain gauge is arranged at a location on the pressure vessel that is preferentially subjected to a pressure-induced load and/or deformation. The arrangement of the at least one strain gauge on the outer underside of the pressure vessel can be particularly well protected. In this case it can be arranged as close as possible to, for example, the control unit and/or the shut-off device of the calorimeter. Furthermore, it is also possible for the at least one strain gauge to be arranged on the underside of the pressure vessel in a housing of the calorimeter, which housing can also enclose the underside of the pressure vessel. This provides a good protection of the at least one strain gauge from external influences, so that the risk of damage is minimized.
The calorimeter may also have a measurement circuit configured to compensate for temperature errors of at least one strain gauge used to determine the deformation of the pressure vessel and indirectly determine the pressure. Due to the warming that may occur during calorimetric measurements, the at least one strain gauge may experience temperature errors that may tamper with the proper determination of the deformation of the pressure vessel and/or the pressure within the pressure vessel. Such a measuring circuit for temperature compensation can be designed as a wheatstone bridge circuit. In addition to the at least one strain gauge for determining the deformation of the pressure vessel and at least indirectly the pressure, the measuring circuit may also have at least one further strain gauge. The at least one further strain gauge may be referred to as a temperature compensated strain gauge.
In this case, the at least one temperature compensating strain gauge is preferably connected to the pressure vessel such that heat is transferred from the pressure vessel to the at least one temperature compensating strain gauge without the at least one temperature compensating strain gauge experiencing a pressure induced load and/or length change due to its contact with the pressure vessel.
The measuring circuit can be designed such that it outputs, as a measurement result, a value which is representative of the pressure inside the pressure vessel and/or the deformation of the pressure vessel associated with this pressure only, on the basis of at least two strain gauges arranged in total in the measuring circuit.
The measuring circuit described above can be implemented particularly easily if at least one strain gauge for determining the deformation of the pressure vessel and/or for determining the pressure and at least one second strain gauge or temperature-compensating strain gauge are the same strain gauge.
In addition to the mechanical loading due to pressure changes inside the pressure vessel acting on the at least one strain gauge provided for determining the deformation of the pressure vessel and/or determining the pressure, this first strain gauge is also subject to temperature errors due to the warming that it must have occurred, which may also be referred to as a temperature drift of the strain gauge. The cause of this temperature error may be temperature dependent changes in resistance and/or strain gauge length. This is particularly true if the strain gauges are electrical or electronic strain gauges. In principle, it is also conceivable to use optical strain gauges as the at least one strain gauge for determining the deformation of the pressure vessel and/or for determining the pressure.
Temperature errors of the measured values determined by the first strain gauges can be compensated for by at least one second strain gauge for temperature compensation, which is preferably identical, which is held in heat-transferring contact with the pressure vessel but is not arranged on the pressure vessel, so that when the pressure in the pressure vessel rises, a mechanical load is also transferred to the second strain gauge. This is particularly easy if at least two strain gauges in total are the same strain gauge.
The measurement circuit may be configured as a bridge circuit integrating two strain gauges. The measuring circuit is preferably configured to automatically perform a temperature error compensation of at least one strain gauge provided for determining the pressure, and the measurement values output by the measuring circuit allow direct conclusions to be drawn about the mechanical load on the pressure vessel and the pressure in the pressure vessel.
In order to ensure that heat is transferred to the at least one second strain gauge or temperature-compensating strain gauge, it may be particularly advantageous if the pressure vessel is made of a material which has a particularly good thermal conductivity, for example aluminium.
The calorimeter may have at least one temperature sensor inside the pressure vessel to determine the amount of heat emitted by the sample during its combustion.
The calorimeter may also have a control unit. The control unit may be connected to the aforementioned shut-off device on the basis of signal technology and/or comprise such a shut-off device. The control unit may be configured to prevent operation of the heat meter when an impermissible deformation of the pressure vessel (e.g. plastic deformation) is detected using the at least one strain gauge and/or using the measurement circuit.
The pressure vessel may have an inlet to fill the pressure vessel with a liquid, in particular water. It may be particularly advantageous if the pressure vessel also has an overflow, in which a liquid sensor is arranged. In this way, the pressure vessel can be filled with liquid via the inlet opening. This continues at least until the liquid sensor in the overflow of the pressure vessel is in contact with the liquid. Once the liquid sensor in the overflow of the pressure vessel detects liquid, it can be assumed that the pressure vessel is full of liquid.
The complete filling of the pressure vessel with liquid is both advantageous for accurate calorimetric measurements and for safety reasons. If there is a surplus of air or gas inside the pressure vessel, the liquid in the pressure vessel is less than when the pressure vessel is completely filled. A smaller amount of liquid in the pressure vessel that is only partially filled has a lower total heat capacity. If this is not taken into account in the calorimetric measurement, the calorific value of the combustion sample in the digestion vessel cannot be determined accurately.
Pressure fluctuations may also occur when the pressure vessel is emptied, as a result of which the interior of the pressure vessel may rise in pressure during calorimetric measurements and the air in the pressure vessel may compress. This can both affect comfortable operation of the calorimeter and can also present a safety hazard.
Advantageously, the calorimeter has an information output device, in particular a display device, by means of which information about the calorimetric measurements and/or the state of the calorimeter, in particular of its pressure vessel, can be output. By means of the information output device, it is possible, for example, to display audible and/or visual information about the pressure value determined using the at least one strain gauge and/or using the measuring circuit, the temperature value of the liquid in the pressure vessel, the deformation of the pressure vessel, the appropriate filling of the pressure vessel of the calorimeter and/or the measured calorific value of the sample.
It can be seen that a particular aspect of using strain gauges as indirect pressure sensors on a pressure vessel is that when the pressure vessel is plastically deformed, i.e. there is still deformation after pressure relief, the strain gauges further output a corresponding signal due to the mechanical load caused by their plastic deformation.
In this connection, it is not necessary to determine the pressure limit value at which a pressure vessel needs to be replaced or at least checked if exceeded. Rather, temporary pressure maxima may also be tolerated if necessary, which exceed the potential limit values, but which do not yet lead to plastic deformation of the pressure vessel. In this connection, in contrast to the calorimeters known from the prior art and from practice, the calorimeter according to the invention can be checked as required, and if necessary, the pressure vessel can also be replaced as required, in the event of an overload of the pressure vessel due to a pressure rise during the calorimetric measurement.
It is further advantageous if at least one strain gauge for determining the pressure is provided on the pressure vessel in cooperation with a temperature sensor of the calorimeter. The sample is ignited within the digestion vessel and the sample is combusted, resulting in a pressure rise within the pressure vessel. In the case of a normal operation of the calorimeter, in particular a normal operation of the stirrer drive of the calorimeter, shortly after the pressure has increased, the liquid inside the pressure vessel increases in temperature therewith. In any case, the pressure rise and thus the ignition of the sample can be detected by means of at least one strain gauge provided on the pressure vessel for determining the pressure. If the interior of the pressure vessel does not rise in temperature after a certain period of time, it may indicate a malfunction or operational error in the calorimeter, in particular in the circulation device of the calorimeter, which may comprise a stirring drive or a magnetic stirrer with stirring magnets.
If the liquid inside the pressure vessel fails to circulate properly, the temperature sensor will only delay or not indicate the temperature rise at all, although it can undoubtedly be verified that ignition has occurred by means of at least one strain gauge for determining the pressure.
The calorimeter according to the invention has the following further advantages: typically, the digestion vessels are only loosely closed, for example by means of sleeve-like shrouds placed on the base plates of the digestion vessels. If the digestion vessel is not properly closed, an oxygen-containing atmosphere introduced into the digestion vessel prior to igniting the sample may pass from the digestion vessel into the pressure vessel. This may result in a pressure rise. Prior to combustion of the sample, the digestion vessel may be filled with an oxygen-containing atmosphere at an overpressure, for example a pressure of 30 x 105 Pa. If a portion of the oxygen-containing atmosphere now escapes from the digestion vessel into the pressure vessel, this escape can be determined at least indirectly by means of the strain gauge. After completion of the calorimetric measurements, the residual pressure still present in the digestion vessel is released to ambient pressure by venting the atmosphere contained in the digestion vessel. If, by means of a strain gauge on the pressure vessel, the pressure is still discontinued above ambient pressure after the residual pressure has been released from the digestion vessel, it may be doubted that a part of the oxygen-containing atmosphere from the digestion vessel has previously entered the pressure vessel. Depending on the measured overpressure, the pressure vessel of the calorimeter should not be opened by the operator himself, but only by a third party service.
The core aspects of the calorimeter according to the invention can be summarized as follows: the invention relates to the technical field of improved calorimetry. The calorimeter proposed by the invention has a pressure vessel which is provided with at least one strain gauge. The aim is to determine the deformation of the pressure vessel during the calorimetric measurement. This allows the load on the pressure vessel to be monitored and the internal pressure within the pressure vessel to be inferred, at least indirectly.
Drawings
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
Fig. 1 shows a highly schematic cross-sectional view of a calorimeter having a two-part pressure vessel and a digestion vessel arranged therein, in which a sample can be burned under an oxygen-containing atmosphere.
Detailed Description
Figure 1 shows a calorimeter (designated as a whole by 1) for determining the calorific value of a
To burn the
The calorimeter 1 has a
The figure shows explicitly that the
On the underside of the
The calorimeter 1 has a measuring
The measuring
The
In order to ensure that the temperature is transmitted from the
In addition, the calorimeter 1 has a
The measuring
The
A
The calorimeter 1 further has an
The
The calorimeter 1 is equipped with stirring means in order to distribute the heat of the
By means of the measuring
If, after evacuation of the atmosphere from the
The invention relates to the technical field of improved calorimetry. The invention proposes, in particular, a calorimeter 1 having a
List of reference numerals
1 calorimeter
1a calorimeter 1 casing
2 pressure vessel
2a lower part of the
2b flange
2c upper part of the
3 digestion container
4 samples
5 ignition device
6 oxygen-containing atmosphere in
7 Water bath in
8 first strain gauge
9 outside the
10 measurement circuit/pressure measurement system
11 temperature compensation strain gauge
12 inlet
12a liquid sensor in the
13 overflow outlet
Liquid sensor in
14 temperature sensor in
15 oxygenating device
16 stirring element
17 stirring driver
18 control unit
18a cutting device
19 information output device
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