RU2707981C1 - Calorimeter - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention relates to measurement of combustion heat of combustible substances in bomb calorimeters of variable temperature with calorimetric liquid. Calorimeter includes calorimetric shell (CS), equipped with cover (6) CS, calorimeter vessel (CV), fixedly installed in CS and equipped with cover (19) CV, calorimetric bomb (21) (CB) installed in CV, at least one element (25) of heating-cooling and magnetic drive installed on outer side of lower part of CS. In lower part of CS there is magnetic mixer (5) CS, and in lower part CV – magnetic mixer (17) CV, synchronously driven into rotation by magnetic drive (24). Cover (6) of the CS can be made with the possibility of providing liquid communication with the CS or contain at least one heating and cooling element (45). Calorimeter can additionally include dosing device for CV, containing dosing vessel (33), supply tank (28) and at least one element (36) of heating-cooling. Heating and cooling elements 25, 36, 45 are preferably Peltier thermoelectric modules.

EFFECT: efficient and fast alignment of CS and CV temperatures, minimization of evaporation of calorimetric fluid from CV, minimization of uncontrolled heat leaks from CV, efficient operation in isoperibolic and adiabatic modes regardless of ambient temperature with high accuracy of CS temperature control, potential dosing and cooling of liquid for CV, high measurement accuracy, shorter time between experiments (measurements), as well as lower requirements for laboratory space and no need to use external cooling devices.

10 cl, 3 dwg

Description

FIELD OF THE INVENTION

The invention relates to the field of measuring the calorific value of combustible substances in variable temperature bomb calorimeters with a calorimetric liquid. In such calorimeters, the amount of heat released is estimated by the change in the temperature of the calorimeter during the combustion of the sample in the calorimetric bomb.

State of the art

Known types of variable temperature liquid calorimeters are composed of four main parts: a calorimetric bomb, a calorimetric vessel, a calorimetric shell, and a calorimetric shell cap.

The calorimetric bomb is made in the form of a collapsible metal vessel into which a test sample of known mass is placed. The bomb contains a sample ignition device, usually a piece of wire heated by electric current. To completely burn a sample, a bomb is usually filled with pure oxygen to a pressure of 1-3 MPa. The bomb is placed in a calorimetric vessel.

A calorimetric vessel with a calorimetric bomb placed in it is filled with a liquid, for example, distilled water. The liquid in the vessel is usually mixed with a stirrer to quickly equalize the temperature in its volume. On top of the vessel is closed by a lid. In addition, a thermometer can be installed in the vessel to measure temperature, and a current source is connected to the ignition contact of the bomb to ignite the sample.

The calorimetric vessel together with the calorimetric bomb is installed in the calorimetric shell. A calorimetric shell surrounds the vessel, but a certain air gap remains between them. From above, the shell remains open for the installation of a vessel and a bomb in it. The shell either completely eliminates the heat exchange of the vessel with the environment, or creates constant heat transfer conditions that do not change from experience to experience (i.e., from measurement to measurement). In addition, a thermometer and one or more devices for regulating its temperature can be installed in the shell.

The cover of the calorimetric shell is designed to close the shell after installing a vessel and a bomb in it. The cover may also have a device for controlling its temperature at the temperature of the shell. Thus, after closing the lid, the calorimetric vessel is completely surrounded by the shell.

To perform its main function - measuring the calorific value of a test sample placed in a calorimetric bomb, calorimeters usually have a number of auxiliary devices, in particular:

- a device for measuring and recording the temperature of a calorimetric vessel and a calorimetric shell;

- a device that allows you to either change the temperature of the calorimetric shell, or to maintain it constant with a sufficient degree of accuracy;

- a device for generating an electrical impulse used to heat a specified length of wire in a calorimetric bomb;

- an electric drive to ensure rotation of the agitator of the calorimetric vessel;

- in automatic calorimeters, an analytical unit may additionally be present, which automatically calculates the calorific value of the sample using the measured curves of the temperature of the vessel, and sometimes the shell, over time, and also performs other functions for controlling the calorimeter units. Often, the role of the analytical unit is a personal computer with specialized software.

In variable temperature liquid calorimeters, various shell temperature control modes are used.

Currently, the isoperibolic regimen is mainly used. In this mode, the temperature of the shell is maintained constant with high accuracy, which ensures the constant heat transfer of the vessel with the environment from experiment to experiment. Usually this temperature is higher than the initial temperature of the vessel.

In simpler calorimeter models, a quasi-isoperibolic regime with uncontrolled shell temperature is used. The change in the shell temperature, and hence the inconstancy of heat transfer from experiment to experiment, is taken into account by calculation methods. In these methods, in addition to changes in vessel temperature, changes in the temperature of the shell during the experiment are additionally taken into account.

Adiabatic mode is less commonly used. In this mode, also known as tracking mode, the sheath temperature is maintained equal to the temperature of the vessel. This regime virtually eliminates the heat exchange of the vessel with the environment, since the difference between the temperature of the shell and the vessel is negligible throughout the experiment.

The calorimetric procedure usually consists of the following main steps.

Calorimetric bomb preparation. At this stage, the burned (tested) sample is weighed, the sample is inserted into the bomb, the ignition device is mounted, and the bomb is filled with oxygen.

Calorimetric vessel preparation. The vessel is refilled with a liquid of a certain temperature, usually room temperature, the vessel is weighed, the vessel is placed in a calorimetric shell, and the bomb is placed in the vessel. In some types of calorimeters, the vessel is not removed from the shell, but is refilled with a strictly defined amount of liquid of a given temperature manually or automatically.

Shell preparation. At this stage, the shell is cooled or heated to a temperature determined by the operating mode.

Pause. Expect stabilization of the temperature of the vessel and shell in the adiabatic mode or the establishment of a constant rate of change of temperature of the vessel in isoperibolic mode.

Measurement. Measure the initial rate of temperature change, ignite the sample, measure the actual rise in temperature of the vessel, measure the final rate of change of temperature of the vessel. Use manual or automatic calculation of the calorific value on the basis of data on changes in temperature and initial data (mass of sample, vessel, excipients, etc.)

One of the problems inherent in known variable temperature calorimeters is the fact that after burning the test sample and completing the experiment, the energy released in the combustion process remains stored in the calorimetric system. Before the next experiment, this energy must be diverted, i.e. cool all nodes of the calorimeter to initial temperatures. This takes a certain amount of time, which increases the total duration of a series of consecutive measurements.

A calorimetric bomb is usually cooled naturally during disassembly and analysis of the combustion products.

The calorimetric shell is integrated into the device and cannot be removed, therefore, additional means of cooling the shell must be provided. So, the PARR 6400 calorimeter uses an integrated cooler. Calorimeters PARR 6200, LECO AC500 and several others use an external source of cold water or a cryostat, while chilled water circulates in the shell, cooling it to the required temperature. The BIK-100 calorimeter uses a built-in cooler based on a refrigeration compressor. The ABK-1 calorimeter has a built-in fan that blows air into the enclosure from the room. The ABK-1V calorimeter has an uncontrolled shell; therefore, cooling can only be carried out naturally.

A calorimetric vessel filled with liquid has a higher heat capacity than the shell, while vessel temperature control devices are rarely used in calorimeters. For this reason, almost all calorimeters are cooled by draining the calorimetric fluid and replacing it with a new one with the required temperature. If the vessel is removable, as in the calorimeters PARR 6200, LECO AC500 and others, replacement is not difficult. If the vessel is non-removable, the cooled liquid is poured automatically, for example, from an external cryostat in LECO AC600, IKA C6000, IKA C200 calorimeters, or the built-in thermoelectric cooler is used as in the PARR 6400 calorimeter. The exception is the ABK-1 calorimeter, in which the vessel is non-removable, and drain liquid from it is not provided, and the vessel is cooled by installing a cooled aluminum cylinder in the vessel instead of a bomb.

An important condition for performing accurate calorimetric measurements is the constancy of the heat equivalent (absolute heat capacity) of the calorimetric system "calorimetric bomb - calorimetric vessel - calorimetric fluid". The thermal equivalent of a calorimeter is determined when it is calibrated by burning a reference substance with a known calorific value. The measured value is then used to determine the calorific value of an unknown substance in operational experiments. Variations in the equivalent value are determined by variations in the heat capacity of the nodes that make up the calorimetric system, and the absolute values of these heat capacities. The main factor that changes the absolute heat capacity of a node is its mass. If the masses of the vessel and the bomb itself are practically unchanged, then the mass of the calorimetric fluid is variable, since the fluid is drained from the vessel after each experiment and replaced with a new one. In addition, the absolute value of the heat capacity of water, which is usually used as a calorimetric fluid, is much higher than the heat capacity of the remaining nodes of the system. For example, at a typical thermal equivalent value of 5000 J / ° C, a 1 g change in the mass of water in the vessel results in a 0.08% change in the heat equivalent value. Such values are already at the error level of modern calorimeters, which is approximately 0.1%, since the measurement result is directly proportional to the value of the thermal equivalent. Therefore, the exact dosage of the liquid in the vessel is the determining factor affecting the invariability of the thermal equivalent of the calorimeter and the overall measurement error. An additional factor affecting the thermal equivalent of the calorimeter is that the heat capacity of the nodes of the calorimeter is a function of temperature, although this effect is much less than the influence of the mass of liquid in the vessel. Nevertheless, the constancy of the average temperature of the vessel from experiment to experiment allows us to somewhat reduce the overall measurement error.

The problem of accurate dosing of liquid in a vessel is solved by manufacturers using various methods. A simple method is the use of a removable vessel, which is filled with liquid at room temperature, then weighed on a balance with high accuracy, and the required mass can be precisely matched. This method is implemented in the calorimeters PARR 6200, LECO AC500, BIK-100, ABK-1V. This is the classic and most accurate method, which, however, requires a removable vessel and its weighing before each experiment.

In the calorimeters PARR 6200, LECO AC500, an external pipette of constant known volume is used for dispensing, from which a removable vessel is filled. This method is also quite accurate and does not require weighing the vessel.

With a fixed vessel, a more complicated method is used in implementation, namely, dosing of liquid by volume overflow. This method is implemented in the calorimeters PARR 6400, LECO AC600, IKA C6000, IKA C200. The calorimetric vessel is filled to the overflow hole, while the excess liquid flows into the supply tank. However, with this filling method, many, sometimes uncontrollable factors, for example, a change in the tilt of the device in the horizontal plane and even the effect of the surface tension of the liquid at the overflow site, begin to influence the metering accuracy. Therefore, all the advantages of a fixed vessel with automatic filling by the overflow method overlap with one drawback - the inability to dispense the liquid with the necessary accuracy.

Separately, the ABK-1 calorimeter can be noted. There is no need to dispense liquid in it, since the vessel is sealed, and draining the liquid from it is impossible, however, this solution has its own known significant disadvantages.

For heating during the experiment, all controlled-shell calorimeters usually use an integrated, adjustable heating element that heats the shell directly or the fluid circulating through the shell. An important condition for correct temperature control is that the temperature of the shell should be several degrees higher than room temperature. An increase in room temperature causes a deterioration in the accuracy of temperature control, and if the temperature exceeds the temperature of the shell, regulation becomes impossible. To ensure that the calorimeter can operate independently of room temperature, it is necessary to be able to both heat and cool the shell not only during the preparation of the calorimeter, but also during the experiment. Many calorimeter models have this capability, but this requires the connection of an external source of coolant, such as water.

The lid of the calorimetric vessel is necessary to reduce the evaporation of the vessel liquid into the space between the vessel and the shell, since part of the energy released during the combustion of the sample is expended on evaporation, which reduces the actual rise in temperature of the vessel. This is partially compensated by the fact that during evaporation the mass of liquid in the vessel decreases, which means that the heat capacity of the system decreases and the temperature rises. But these processes are unequal and uncontrollable, and therefore the use of a vessel lid is mandatory. Such caps are available on all known calorimeters.

The lid of the calorimetric shell is necessary to reduce heat loss from the vessel into the environment. The temperature of the lid can be unregulated, both in the calorimeters ABK-1, ABK-1V, and adjustable, as in the calorimeters PARR 6400, PARR 6200, LECO AC500, LECO AC600, IKA C6000, IKA C200, BIK-100. The temperature of the lid should be as close as possible to the temperature of the shell, as under this condition, the vessel will be completely surrounded by a shell of controlled temperature. Traditionally, this is realized by manufacturers pumping liquid from the shell through the lid and returning it back to the shell. Moreover, there are unavoidable heat losses during fluid transport through pipelines from the shell to the cover, and its temperature becomes slightly lower than the temperature of the shell. However, in the case of uncontrolled temperature of the lid of the shell, the heat loss is much greater, and in addition, they become uncontrolled and dependent on external conditions.

An important condition for a successful calorimetric measurement is to minimize the temperature non-uniformity of the heat exchange surfaces of the calorimeter - the outer surface of the vessel and the inner surface of the shell. Traditionally, for these purposes, mixers are used in the calorimetric vessel, which intensively mix the liquid and eliminate the unevenness of the temperature field, even with a sharp release of heat in the calorimetric bomb during ignition of the test sample. During its operation, the mixer generates a certain amount of heat due to friction in the bearing and friction of the body of the mixer against the liquid. The indicated amount of heat should be constant when calibrating the calorimeter and in serial tests to compensate for the effects of this stray heat. For this, the rotation speed of the mixer must be kept strictly constant. Equally important is the quality of mixing, for which some manufacturers use special guiding devices.

Two types of agitator drive are mainly used. In the first type of mixers there is a rotating shaft, which passes through the covers of the shell and the vessel and is immersed in the liquid of the vessel. A stirrer impeller is installed at the end of the shaft. Such mixers are used in all models of calorimeters from PARR, LECO, IKA.

Another drive option is a magnetic stirrer, which is used, for example, in ABK-1, ABK-1V, BIK-100 calorimeters. The stirrer itself with magnets rotates on the bearing, at the bottom of the calorimetric vessel. The counterpart - a disk with magnets - is located under the shell and is driven by the engine. The main advantage of magnetic mixers is the absence of heat leakage on the drive shaft and spurious heat generation from the shaft seal.

The way to equalize the unevenness of the shell temperature depends on the design of the temperature control device. In the case of an electric heater, as in the ABK-1 calorimeter, the heater in the form of a nichrome tape is evenly distributed over the outer surface of the shell. In the case of a liquid jacket, as in the calorimeters PARR 6400, PARR 6200, a liquid is pumped through the tube evenly distributed on the outer surface of the shell, the temperature of which is regulated outside the shell using various devices.

Thus, to meet all the requirements for calorimeters in order to increase the accuracy and speed of measurements, it is necessary to solve many problems, sometimes mutually exclusive.

As a prototype of the present invention, the calorimeter described in the patent of the Russian Federation No. 2529664, priority date 07/11/2013. Said calorimeter comprises a hollow calorimetric shell provided with a lid, a calorimetric vessel mounted in a calorimetric shell and provided with a lid, a calorimetric bomb mounted in a calorimetric vessel, and an agitator located in the calorimetric vessel and having a magnetic drive. The magnetic drive is mounted in a calorimetric shell.

A significant disadvantage of the known calorimeter is that in the calorimetric shell there is no possibility of mixing the liquid to equalize its temperature. A vessel stirrer is installed in the calorimeter, but it provides only partial mixing of the liquid in its lower part. No means are provided for mixing the liquid throughout the volume of both the vessel and the shell, which makes it impossible to quickly equalize their temperatures. Another disadvantage of this design is that the shell has a cover, the temperature of which is not regulated in any way and, moreover, depends on the ambient temperature. This leads to spurious heat leakage from the vessel into the environment. The above disadvantages lead to a decrease in the accuracy of calorimetric measurements. In addition, in the known calorimeter there is no possibility of heat removal from the calorimetric vessel released during the previous experiment. Therefore, to prepare for a new experiment, it is necessary to use external cooling devices and increase the time between experiments.

The objective of the invention is the creation of a bomb calorimeter of variable temperature, which would maximize the advantages of the currently known designs of calorimeters and devoid of their shortcomings.

Another objective of the present invention is to improve the accuracy of calorimetric measurements.

Another objective of the present invention is to provide a calorimeter capable of quickly equalizing the temperature of the calorimetric shell and the calorimetric vessel.

Another objective of the present invention is to create a calorimeter that operates both in isoperibolic and adiabatic modes, while the accuracy of controlling the temperature of the shell does not depend on the ambient temperature.

Another objective of the present invention is to create a calorimeter, the shell of which has the ability to both heat and cool all internal surfaces, including the bottom and cover, both during preparation and during measurement.

Finally, another objective of the present invention is to realize the possibility of dispensing and cooling the liquid for the vessel automatically inside the device with the necessary accuracy and without the use of external devices, so that the preparation of the calorimeter for the next experiment can take place during the current experiment, and the time between experiments is minimal.

The technical result consists in increasing the accuracy of measurements by effectively equalizing the temperatures of the calorimetric shell and the calorimetric vessel, reducing the evaporation of the calorimetric liquid and uncontrolled heat leakage from the calorimetric vessel. Also, the technical result is to reduce the time between experiments (measurements) by dosing and cooling the liquid for the vessel automatically inside the device during the current experiment. Also, the technical result is to reduce the requirements for laboratory premises by increasing the efficiency of temperature control of the calorimetric shell in isoperibolic and adiabatic modes, regardless of the ambient temperature and the absence of the need for external cooling devices.

Disclosure of the invention

To solve the tasks and achieve the claimed technical result, a calorimeter is proposed that includes a calorimetric shell (KO) equipped with a KO cap, a calorimetric vessel (KS) fixedly installed in the KO and equipped with a KS cover, a calorimetric bomb (KB) installed in the KS, according to at least one heating-cooling element and a magnetic drive mounted on the outer side of the lower part of the KO, preferably on the bottom. A magnetic stirrer KO is mounted in the lower part of the KO, driven by a magnetic drive. A magnetic stirrer KS is mounted in the lower part of the KS, driven into rotation by a KO magnetic stirrer.

The use of a magnetic drive for KO and KS mixers eliminates the possibility of heat leakage along the drive shaft and stray heat from the shaft seal, which improves the accuracy of calorimetric measurements. In addition, the design is greatly simplified and the reliability of the mixers is increased. The rotation of the KS mixer due to magnetic coupling with the KO mixer allows you to do without using a separate drive for the KS mixer.

According to one of the variants of the invention, KO contains an outer glass, a middle glass and an inner glass. The space between the outer and inner cups is filled with liquid, with the middle cup having a slightly lower height, and openings for the passage of fluid are made in its bottom. A magnetic stirrer KO is located between the bottoms of the middle and inner glasses. During its rotation, the KO mixer provides intensive liquid circulation in the annular gaps formed by the bodies of the three KO glasses, which allows for rapid temperature equalization both in volume and on the external surfaces of the KO.

According to another embodiment of the invention, a radiator is installed between the bottoms of the outer and middle KO glasses. The radiator allows you to accelerate the heat transfer between the heating and cooling elements and the liquid washing the radiator, and this, in turn, allows the calorimeter to work not only in isoperibolic but also in adiabatic mode (with a rapid change in the temperature of the KO).

According to another embodiment of the invention, the CS contains an outer cup and an inner cup filled with liquid, the inner cup having a slightly lower height, and openings for the passage of fluid are made in its bottom. Between the bottoms of the outer and inner glasses have a magnetic stirrer KS. During its rotation, the KS mixer provides an intensive circulation of liquid in the annular gaps formed by the bodies of two glasses and a design bureau. With this design, even a sharp heat release during the burning of a sample in a design bureau leads to a rapid temperature equalization both in terms of the volume of the composite material and on its external surfaces. In this case, the temperature non-uniformity on the heat exchange surfaces of the CS remains minimal.

According to another embodiment of the invention, the lid of the COP is made in the form of a glass of small depth, and when it is installed in the COP, the lower part of the cover is partially immersed in the liquid of the COP. With this design of the lid KS, evaporation of the liquid KS is minimized, since the surface of evaporation of the liquid is sharply reduced.

According to another embodiment of the invention, the cover of the TO is hollow with the possibility of providing fluid communication with the TO. This design allows you to completely surround the COP with a liquid jacket, which means that heat exchange of the COP with the environment is eliminated.

According to an alternative embodiment of the invention, the cover KO is made integral, but at the same time contains at least one heating-cooling element. The temperature of the lid is maintained equal to the temperature of the KO. This design allows you to simplify the design of the lid KO, while maintaining the insulation of the COP from the environment.

According to another embodiment of the invention, the calorimeter further comprises a dosing device for KS. The presence of a dosing device allows dosing and cooling of the liquid for KS automatically inside the device with the necessary accuracy and without the use of external devices. Moreover, the cooling of a portion of the liquid for the next experiment can take place during the current experiment, which significantly reduces the time between experiments. The dosing device may comprise a dosing vessel, a supply container and at least one heating-cooling element.

Preferably, at least one of the above heating-cooling elements is a Peltier thermoelectric module. The use of Peltier thermoelectric modules makes it possible to provide both heating and cooling of KOs and other elements of the calorimeter without the use of external devices. In this case, the accuracy of temperature control, in particular the temperature of the KO, does not depend on changes in ambient temperature. Such regulation can be carried out both during the experiment and for the removal of residual heat from KO and other elements of the calorimeter between experiments.

Brief Description of the Drawings

In FIG. 1 schematically shows the internal structure of a calorimeter according to one embodiment of the invention.

In FIG. 2 schematically shows a hydraulic diagram of a calorimeter according to one embodiment of the invention.

In FIG. Figure 3 schematically shows the lid of a calorimetric shell (KO) according to one embodiment of the invention.

The implementation of the invention

Next, with reference to the accompanying drawings, some preferred embodiments of the invention are described in more detail.

In FIG. 1 shows the internal structure of a calorimeter.

The calorimeter contains a calorimetric shell (KO), which in the general case can be performed similarly to the calorimetric shell of the closest analogue described in RF patent No. 2529664, i.e. consist of two glasses coaxially arranged in one another, between the walls of which a space is formed filled with a liquid, for example water. Since such a performance of KO is known in the prior art, it is not reflected in the figures.

KO according to another embodiment of the present invention is not two, but three coaxially arranged glasses: the outer glass (1), the middle glass (2) and the inner glass (3). As in the case of KO consisting of two glasses, glasses (1, 2, 3) KO are preferably, but not necessarily, made of a material with high thermal conductivity and low specific heat capacity, for example, of copper. Glasses can be chemically coated with nickel to protect against oxidation. To reduce radiative heat transfer between KS and KO, the inner surface of the inner glass (3) KO can be additionally polished.

In the case of the execution of KO in the form of the three indicated coaxially arranged glasses (1, 2, 3), a liquid KO shirt is formed between the outer glass (1) and the inner glass (3). The middle glass (2) is used to organize the circulation of fluid in the CO. The height of the middle glass (2) is preferably somewhat less than the height of the outer (1) and inner (3) glasses. All three glasses can be connected to each other by any known method, in particular, a pipe (4) with a bearing mounted on it (not shown in the figures) passing through the central holes in their bottoms. On both sides of the pipe (4) is equipped with o-rings, for example rubber, which prevent leakage of liquid from the CO. A magnetic stirrer (5) KO is mounted on the bearing of the nozzle (4). In the bottom of the middle glass (2) holes are made for the passage of fluid to the suction cavity of the magnetic stirrer (5) KO. Magnetic mixer (5) KO actually represents the rotor of a centrifugal pump, and the bottoms of the inner (3) and middle (2) glasses of KO form in this case the pump casing. From the injection cavity of the mixer (5) KO, the liquid rises up the KO along the annular gap between the inner (3) and middle (2) glasses. Then the liquid overflows over the edge of the middle glass (2) and follows down the annular gap between the middle (2) and external (1) glasses. Then the liquid washes the bottom of the outer cup (1) and, through the holes in the bottom of the middle cup (2), enters the suction cavity of the mixer (5) of the KO, thereby closing the circulation circuit. The described fluid movement in the CO is shown for convenience by the arrows in FIG. 1. In addition, the mixer (5) KO gives rotation relative to the center of the entire thickness of the liquid in the KO. The combination of the vertical and rotational motion of the liquid makes it move in a spiral, further enhancing the mixing effect, thereby minimizing the uneven temperature of the heat transfer surfaces of the CO. Additionally, the outer surface of the CO can be covered with a layer of heat-insulating material (not shown in Fig. 1) to reduce environmental losses.

QO from above is closed by a cover (6) Qo. As mentioned above, the temperature of the lid (6) of KO should be as close as possible to the temperature of KO.

In one of the embodiments of the present invention, the cover (6) KO can be made hollow. A suction tube (7) and a drain pipe (8) are installed on the cover (6) of the KO so that when the cover (6) of the KO is closed, the ends of the tubes are immersed in the KO liquid.

Inside the cavity of the lid (6) KO provided the possibility of circulation of the fluid as follows. Through the intake pipe (7), the liquid from the KO through the fitting (9) enters the inlet of the circulation pump (10). From the output of the circulation pump (10), the fluid enters the nozzle (11) mounted on the upper part of the cover (6) of the CO, and merges through it into the cavity of the cover (6) of the CO. As the lid (6) is filled, the liquid flows to the upper edge of the drain tube (8) and then flows back into the liquid pipe through it. Preferably, if the circulation pump (10) is installed directly above the cover (6) KO, since the length of the connecting tubes is minimal. This arrangement of the circulation pump (10) eliminates the main drawback inherent to one degree or another with all known calorimeters with fluid circulation in the cap, namely, heat loss during fluid transport through long tubes from the shell to the cap. The direction of fluid flow in the cap (6) of the KO is shown for convenience by the arrows in FIG. 1. In addition, a penetration (12) is installed in the cover (6) of the KO, which serves to electrically isolate the ignition electrode (13) from the calorimeter body.

A calorimetric vessel (KS) is located inside the KO, which, preferably, consists of two coaxially arranged cylindrical cups - an outer cup (14) KS and an inner cup (15) KS, preferably made of a material with high thermal conductivity and low specific heat, for example, copper. Glasses can be chemically coated with nickel to protect against oxidation. To reduce radiative heat transfer between the CS and KO, the outer surface of the outer cup (14) of the CS can be additionally polished. A hollow shaft (16) with a bearing (not shown in the figures) is installed on the bottom of the outer cup (14) KS. A magnetic stirrer (17) KS is mounted on the bearing of the hollow shaft (16). A fitting (18) is screwed into the hollow shaft (16) through the hole in the bottom of the outer cup (14) KS, which serves to fill and drain the liquid. The fitting (18) communicates with the internal volume of the compressor through additional holes in the hollow shaft (16).

The inner cup (15) KS through the Central hole in its bottom is fixed to the hollow shaft (16). It has in the bottom a series of holes concentrically located above the suction cavity of the mixer (17) KS, providing intensive circulation of fluid in the KS.

A magnetic stirrer (17) KS, by analogy with a magnetic stirrer (5) KO, is essentially also a centrifugal pump. The housing of the specified pump is formed by the space between the bottoms of the inner (15) and outer (14) glasses of the COP. During its rotation, the mixer (17) KS discards the liquid to the walls of the outer cup (14) of the KS, where excess pressure is created, so that the liquid rises up the annular gap formed by the outer (14) and internal (15) cups of the KS, and evenly washes the walls CS, transferring to them the heat released in the calorimetric bomb (KB) (21). Having reached the top of the inner cup (15) KS, the liquid overflows into its inner cavity. Since the mixer (17) of the CS creates a vacuum in its suction cavity, the liquid raised to the top of the CS begins to move down. In this case, it washes the walls of design bureau (21), taking away the released heat of reaction from them. Having reached the bottom of the inner cup (15) KS, the liquid through the holes enters the suction cavity of the mixer (17) KS, thereby closing the circulation circuit. The direction of movement of the liquid in the vessel for convenience is shown by the arrows in FIG. 1. At the same time, by analogy with KO, a spiral fluid movement is also formed in the CS, enhancing the mixing effect.

With such a design of the SC, even a sharp heat release during the combustion of the sample in the design bureau (21) leads to a rapid temperature equalization both in the volume of the composite and on its external surfaces. In this case, the temperature non-uniformity on the heat exchange surfaces of the CS remains minimal.

From above, the CS is closed by the cover (19) of the CS. Cover (19) KS is made in the form of a glass of small depth. A penetration (20) is installed in the central hole of the cover (19) KS, which can simultaneously be the handle of the cover (19) KS. Through the penetration (20), without touching its walls, a spring-loaded ignition electrode (13) is introduced, which abuts against the ignition contact of the design bureau (21).

The COP, together with the KB installed in it (21), is filled with a certain amount of liquid, for example water. Preferably, the liquid is filled with a slight excess, so that the cap (19) KS becomes a little immersed in the liquid, for example 3-5 mm. Excess liquid is squeezed out into the annular gap between the cap (19) of the KS and the outer cup (14) of the KS, as well as into the cavity between the ignition electrode (13) and the inner surface of the penetration (20). With such a combination of the design of the cap (19) of the KS and the amount of liquid in the KS, a sharp reduction in the surface of the liquid occurs (evaporation mirrors). This, in turn, leads to minimizing the evaporation of the calorimetric fluid into the space between the CS and KO and, as a consequence, to increasing the accuracy of measurements.

To measure the temperature of the outer surface of the outer cup (14) KS and the inner surface of the inner cup (3) KO, they can be placed respectively flat overhead resistance thermometers (22) and (23), made, in particular, of platinum or copper.

A fixing triangular stand made of a material with low thermal conductivity, such as plastic (not shown in Fig. 1), can be installed at the bottom of the KO. In this case, the contact of the CS with the stand is carried out at several points, for example, six, where three points are the supports of the CS, and the other three points prevent the lower part of the CS from shifting in the horizontal plane and center the CS along the axis of the shell. To eliminate the displacement of the upper part of the COP in the horizontal plane, additional expansion screws (not shown in Fig. 1) can be added. Thus, the CS is located inside the KO with the same air gap between all heat exchange surfaces. Additional polishing of the heat exchange surfaces of KS and KO leads to a decrease in the radiative heat exchange between them and positively affects the overall accuracy of the measurements.

The wires from the resistance thermometers (22) and (23), as well as the tube connected to the fitting (18) for draining the liquid from the compressor, go outside the KO through the hole in the pipe (4).

To rotate the mixer (5) KO and the mixer (17) KS, a magnetic drive is used, made, for example, in the form of a disk (24) with magnets, which is driven by a motor with a constant speed of rotation (not shown in Fig. 1), for example stepper motor. Due to the magnetic coupling between the disc magnets (24) and the magnets of the KO mixer (5) and the KS mixer (17), the rotation of the disk (24) leads to the synchronous rotation of both mixers (5, 17). At the same time, it is not necessary to provide a tight seal of the axes of the mixers (5, 17), which leads to additional uncontrolled heat generation inside the calorimeter, as well as to stray heat exchange through the body of the axes themselves into the environment, since these axes simply do not exist. In addition, the use of an engine with a constant speed of rotation allows you to stabilize the heat from friction in the bearing of the mixer (17) KS and the friction of the body of the mixer (17) KS on the liquid from measurement to measurement. The same heat generation in the calibration measurement and subsequent working measurements allows us to compensate for the negative effect of heat generation (17) of the KS mixer on the measurement accuracy.

On the outside of the bottom of the outer cup (1) of the KO, heating-cooling elements (25) are placed, for example, Peltier thermoelectric modules, although it will be clear to a specialist that other heating-cooling devices can be used. Each element (25) can be pressed with a certain force to the outer glass (1) of the KO using radiators (26). Through the radiators (26) with the help of fans (not shown in Fig. 1), the air flow from the room is intensively pumped.

The execution of elements (25) in the form of Peltier modules has the advantage that when an electric current flows through a thermoelectric converter using the Peltier effect, one side is heated and the other is cooled. When the polarity of the applied voltage changes, the heated and cooled sides change places. This allows, among other things, to quickly and simply switch the operation mode of the elements (25) from heating to cooling and vice versa.

Using the example of the use of Peltier modules as elements (25) of heating and cooling, the KO temperature control system works as follows.

With the flow of electric current of the required polarity, the side of the elements (25) in contact with the outer cup (1) of the CO is cooled. Moreover, since the outer cup (1) of the KO is made of a material with high thermal conductivity (for example, copper), the liquid inside it also begins to cool. And since intensive circulation of fluid is organized in the KO using a magnetic stirrer (5) KO, this change in the temperature of the liquid quickly spreads throughout the KO, including the heat exchange surface - the inner surface and the bottom of the KO, as well as the cover (6) of the KO, using a circulation pump ( 10). The reverse side of the elements (25) in contact with the radiators (26) is heated and transfers its heat to them. If the radiators (26) are continuously blown by fans, they give this heat to the circulating air, and the heat is removed outside the calorimeter. When changing the polarity of the voltage on the elements (25) (Peltier modules), the calorimeter enters the mode of heating the liquid in the CO.

In addition, when assembling the KO between the outer (1) and middle (2) glasses KO can be installed radiator (27) with many radially vertical ribs. The radiator (27) is designed to increase the heat exchange surface between the elements (25) and the liquid circulating in the CO and washing the radiator (27). The radiator is made of a material with high thermal conductivity, such as copper. To protect against oxidation, it can be optionally coated with nickel.

In the process of measurement in isoperibolic mode, the KO temperature stabilizes at a certain level. As shown earlier, problems arise if the room temperature becomes close to or even higher than the temperature of the KO. In this case, the inability to cool KO leads to the impossibility of the calorimeter. The use of Peltier modules as heating-cooling elements (25) eliminates this problem, since the heating / cooling power to maintain the temperature of the KO in this mode requires a small amount. Cooling of KO between measurements in the isoperibolic mode is usually not required, since the temperature of KO in a series of consecutive measurements does not change.

In adiabatic mode, the temperature of the KO should be essentially equal to the temperature of the KS. The main problem of the adiabatic regime is that upon ignition of the test sample, the temperature of the CS in a short time of tens of seconds increases sharply. To comply with the adiabatic regime, it is necessary that the temperature of KO grow as fast. Usually, especially when burning high-energy fuels, the temperature of the KO lags behind the temperature of the KS at the initial time after ignition of the sample. This introduces an additional measurement error. To eliminate this lag, it is necessary to increase the power of the KO heater and reduce the reaction time of the system to such large disturbances. And this, in turn, leads to overshoot and overheating of the CO at times when the rate of temperature change becomes low, especially if the control system does not have the ability to cool, which, again, leads to an increase in the measurement error. This limits the possibility of using the adiabatic regime in calorimeters by burning only low-calorie or slowly burning samples.

It should be noted that the Peltier module used as the heating-cooling element (25) is actually a heat pump and, as is known, has one drawback - low efficiency. In other words, it allows heat transfer from a less warmed body to a warmer body, and at the same time, due to its low efficiency, much more heat is generated on its hot side than it was transferred from cold. This "spurious" heat is released when a substantial current (units of amperes) flows from the power source through the Peltier module.

The low efficiency of the Peltier module, which is a drawback in refrigeration technology, in the proposed embodiment of the calorimeter, on the contrary, is an advantage when the calorimeter operates in adiabatic mode, where high speed is required, and hence the heating power. The low efficiency of the Peltier module allows it to be used mainly as a heater due to the flowing substantial current from the power source. In the heating mode, radiators (26) are cooled below the temperature of the air blowing them and can take heat from the room. This “added” energy is supplied (pumped) due to the Peltier effect on the hot side of the Peltier module and further increases the heating of the CO. And the possibility of providing not only heating, but also cooling eliminates the overshoot of the system both at high and low heating rates of KO.

In adiabatic mode, there is also a need to cool QoS between measurements. At the end of each measurement, the KO temperature is equal to the KS temperature, and it must be reduced in order to bring about the initial conditions before the next measurement. Peltier modules cooling the shell also successfully cope with this task.

The use of Peltier modules in the calorimeter makes it possible to both heat and cool KO directly during measurements without the use of external devices and regardless of the ambient temperature. Moreover, the location of the Peltier modules directly below the bottom of the outer cup (1) of the KO, the use of low-potential ambient heat and the use of a radiator (26) allow for the fastest possible change in the temperature of the liquid in the KO in comparison with the well-known scheme that includes a separate heater (heat exchanger) and providing pumping fluid through the pump. Transport time, and hence the reaction time to temperature disturbances is minimized, which is especially important in the adiabatic mode of operation.

In the proposed version of the calorimeter, a fixed KS is used, which allows to simplify the measurement procedure and minimize possible operator errors. As shown above, the accuracy of dosing of liquid in the COP is the main factor determining the invariance of the thermal equivalent of the device.

In order to dispense the liquid inside the calorimeter, a dosing vessel can additionally be installed. The hydraulic circuit of such a calorimeter embodiment is shown in FIG. 2.

The calorimeter liquid stock is stored in a supply tank (28). Before starting the experiment (measurement), the liquid from the supply tank through the valve (29) enters the pump inlet (30). From the outlet of the pump (30), through the valve (31) and the heat exchanger (32), the liquid fills the dosing vessel (33). After filling the dosing vessel (33), excess liquid is drained back into the supply tank (28) along line (34). The upper and lower parts of the dosing vessel (33) can be made conical, which makes it possible to accurately dose the volume of liquid accumulated in the dosing vessel (33). Upon completion of filling the dosing vessel (33), the valve (29) closes and the valve (35) opens. In this case, a circulation loop is organized for the dosing vessel (33) - pump (30) - heat exchanger (32).

A fluid circulates inside the heat exchanger (32). Between the radiator (37) and the working surface of the heat exchanger (32), a heating-cooling element (36), for example, a Peltier module, is clamped with a certain force. The radiator (37) is intensively blown by a stream of air using a fan (38). By changing the strength and direction of the current through the element (36), taking into account the organized circulation loop, it becomes possible to stabilize the temperature of the liquid in the dosing vessel (33). The temperature of the liquid in the dosing vessel (33) is measured using a resistance thermometer (39).

After reaching the required temperature of the liquid in the dosing vessel (33), the valve (31) closes and the valve (40) opens. In this case, the liquid from the dosing vessel (33) begins to fill the CS (in FIG. 2, the CS is marked as the outer (14) and internal (15) glasses of the CS). After overflow of all the liquid from the dosing vessel (33) into the KS, the valve (40) closes, thereby isolating the KS from the other pipelines of the device. The calorimeter operator then starts the calorimetric measurement.

During the calorimetric measurement, the dosing vessel (33) is again filled with liquid and its temperature stabilizes. It is essential that there is no need to interrupt the current experience (current measurement). At the end of the experiment, the heated liquid from the compressor station is pumped through open valves (41, 42) through an open valve (41, 42) to a supply tank (28) along line (43). Then, by switching the necessary valves, the dose of prepared liquid from the dosing vessel (33) again fills the CS. After this, the operator can immediately proceed to the next measurement, and the preparation system proceeds to cool a new dose of liquid in the dosing vessel (33).

As mentioned above, in one embodiment of the present invention, the cover (6) of the CO can be hollow. In FIG. 3, an alternative embodiment of the cover design (6) of the CO is further proposed. According to this embodiment, the cover (6) of the CO is disk-shaped (44) made of a material with high thermal conductivity and relatively low specific heat, such as copper, preferably additionally coated with nickel and / or polished. On top of the disk (44), low-power heating-cooling elements (45) are concentrically mounted, for example, Peltier modules. Elements (45) are pressed against the disk (44) by a radiator (46) with a radial arrangement of ribs. The radiator (46) can be blown by a stream of air from the fan (not shown in Fig. 3). The temperature of the disk (44) is measured by a miniature resistance thermometer (47). A hole is made in the center of the disk (44), in which an insulating penetration (48) is fixed with the ignition electrode.

The automatic control system, measuring the temperature of the disk (44) with a thermometer (47), regulates the temperature of the heating-cooling elements (45), changing the magnitude and direction of the current through the indicated Peltier modules used as elements (45), and thereby maintains the temperature of the lid ( 6) CO at the required level. The required temperature value comes from the KO temperature control system, which was described earlier. Since the disk (44) of the cover (6) KO is made of a material with high thermal conductivity and a relatively small specific heat, the temperature unevenness of the cover (6) KO remains minimal even with sharp changes in the temperature controller setting.

The proposed alternative design of the cover (6) KO allows to simplify its design and eliminate the need to use a circulation pump (10) and all supply tubes to control the temperature (heat transfer surface) of the cover (6) KO. Since the cover (6) KO has a negligible heat capacity, it is possible to use Peltier modules of small power as elements of the heating-cooling (45).

Thus, the proposed options for the calorimeter and some of its nodes can eliminate many of the significant disadvantages of the known calorimeters; to increase the accuracy of calorimetric measurements due to the effective equalization of the temperature of KO and KS, minimizing the evaporation of the calorimetric fluid from the KS and the use of the KO cap with the possibility of temperature control; ensure the effective operation of the calorimeter in isoperibolic and adiabatic modes, regardless of the ambient temperature and without the use of external cooling devices, in particular, through the use of Peltier thermoelectric modules as heating and cooling elements of KO; reduce the preparation time of the calorimeter for the next measurement by dosing and cooling the liquid for the COP automatically inside the device with the necessary accuracy and without the use of external devices.

Claims (16)

1.Calorimeter, including: calorimetric shell (KO) equipped with a cover (6) KO, a calorimetric vessel (KS), fixedly installed in the KO and equipped with a cap (19) KS, calorimetric bomb (KB) (21) installed in the COP, and at least one heating-cooling element (25) mounted on the outside of the lower part of the KO, at the same time, a magnetic stirrer (5) is installed in the lower part of the KO, and a magnetic stirrer (17) of the KS, driven by a magnetic drive, is installed in the lower part of the KS, characterized in that the magnetic stirrer (17) KS is driven into rotation by the magnetic stirrer (5) KO due to the magnetic coupling between them. 2. The calorimeter according to claim 1, in which the KO contains a coaxially located outer cup (1) KO, the middle cup (2) KO, the inner cup (3) KO and the mixer (5) KO, the middle cup (2) has a lower height than the outer (1) and inner (3) glasses and in the lower part of the middle glass (2) holes are made for supplying liquid to the suction cavity of the mixer (5) KO. 3. The calorimeter according to claim 2, in which a radiator (27) is installed between the bottoms of the outer (1) and middle (2) KO glasses. 4. The calorimeter according to claim 1, in which the CS contains a coaxially located outer cup (14) KS and an inner cup (15) KS, a calorimetric bomb (21) (KB) and an agitator (17) KS, and the inner cup (15) KS has a lower height than the outer cup (14), and in the lower part of the inner cup (15) KS holes are made for supplying fluid to the suction cavity of the mixer (17) KS. 5. The calorimeter according to claim 1, in which the cover (6) of the TO is made with the possibility of providing fluid communication with the TO. 6. The calorimeter according to claim 1, in which the cover (6) KO contains at least one element (45) heating-cooling. 7. The calorimeter according to claim 1, in which the cap (19) KS partially immersed in the liquid KS. 8. The calorimeter according to claim 1, further comprising a dosing device for KS. 9. The calorimeter according to claim 8, in which the dosing device comprises a dosing vessel (33), a supply tank (28) and at least one heating-cooling element (36). 10. Calorimeter according to any one of paragraphs. 1, 6, 9, in which at least one of these heating-cooling elements (25, 36, 45) is a Peltier thermoelectric module.

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