RU209777U1 - thermoelectric sensor - Google Patents

Abstract

The proposed utility model relates to signaling and control means and can be used to remotely detect icing and determine environmental conditions similar to the conditions for the formation or predisposition to the formation of icing on various surfaces. The utility model includes a first thermoelectric element (1a), a first thermoelectric heat flow sensor (2a) and a temperature sensor (3), and additionally includes a second thermoelectric element (1b), a second thermoelectric heat flow sensor (2b), a heat-conducting plate (4), protective shell (5) and base (6). The first thermoelectric element (1a) and the first thermoelectric heat flow sensor (2a) are mounted one on top of the other, forming the first thermoelectric block, and the second thermoelectric element (1b) and the second thermoelectric heat flow sensor (2b) are mounted one on top of the other, forming the second thermoelectric block , which are mounted on the base (6) from the side of thermoelectric elements, spaced apart from each other. A heat-conducting plate (4) is installed over the first and second thermoelectric blocks, and on the inner side of the heat-conducting plate (4) in the gap between the heat flow sensors (2a) and (2b), a temperature sensor (3) is placed separately. The first (2a) and second (2b) thermoelectric heat flow sensors are electrically connected in series, and the first (1a) and second (1b) thermoelectric elements are electrically connected to each other. The first and second thermoelectric blocks, the temperature sensor (3) and the heat-conducting plate (4) are enclosed in a protective sheath (5), open in the region of the outer surface of the heat-conducting plate with the formation of a cuvette (7), the bottom of which is the outer surface of the heat-conducting plate (4), and the walls - a protective shell (5). The utility model makes it possible to increase the sensitivity to ice formation or a predisposition to it, while at the same time increasing the accuracy of determining ice formation or a predisposition to its occurrence. 5 z.p. f-ly, 4 ill.

Description

The proposed utility model relates to signaling and control means and can be used to remotely detect icing and determine environmental conditions similar to the conditions for the formation or predisposition to the formation of icing on various surfaces, for example, road surfaces, runways, aircraft surfaces, wind turbines, power lines, etc.

The formation of ice or the appearance of conditions for the formation of an ice cover directly affects the safety of equipment operation.

Ice formation on the surface of aircraft complicates their operation and increases the risk of accidents.

Ice on power lines increases the accident rate and is the cause of frequent failure due to wire breaks.

A variety of icing sensors are currently in use, the operation of which is based on various direct or indirect methods for determining the presence of icing or a predisposition to icing.

Ice alarms are mainly used, which, based on various physical principles, determine the presence of ice or the likelihood of ice formation.

Among the icing sensors, sensors capable of detecting the fact of the water-ice phase transformation and vice versa ice-water have a noticeable advantage.

In such sensors, a built-in Peltier element (thermoelectric cooler) implements a heating-cooling cycle in the measuring cuvette. And with the help of the built-in temperature sensor, the fact of the water-ice phase transformation occurring with the release or absorption of a significant amount of heat at a fixed temperature of this phase transition is recorded.

The characteristics of icing to be detected by such sensors are the fact of icing or the predisposition to it, the temperature of the icing and the intensity of the icing.

The disadvantage of many icing sensors is that they do not reliably detect all of these signs of icing at the same time. This is especially true of quantitative characteristics - ice formation temperature and intensity (amount of ice).

The reason for such shortcomings is both indirect methods for determining the onset of a phase transition event and estimated methods for determining the intensity.

For example, a method and system for detecting the probability of ice formation on the surface of a vehicle is known from the prior art (see US 4570881, IPC B64D 15/20, publ. 18.02.1986). The method involves placing the diaphragm on the vehicle surface, alternately cooling and heating said diaphragm with a Peltier element to temperatures below and above the ambient temperature in accordance with a certain cycle that creates and then melts ice if the ambient air temperature is near or below the point freezing. In the mentioned cycle, the diaphragm is alternately and repeatedly cooled and heated, and any change in the resonant frequency of the diaphragm vibration is recorded. A change in the resonant frequency indicates a water-ice phase transition. Thus, ice formation is determined qualitatively, without quantitative interpretation.

A thermoelectric icing sensor is known from the prior art (see RU 2534493, IPC B64D 15/20, publ. 27.11.2014). Known thermoelectric icing sensor contains a thermoelectric module made in the form of a Peltier element that performs the function of a heat pump, and a temperature sensor mounted on the outer sensitive surface.

The Peltier element, according to a given algorithm, depending on the ambient temperature and its proximity to the freezing point, heats or cools the sensitive surface. The temperature sensor monitors temperature changes. If there is ice on the surface and there are conditions for ice formation, the temperature of the sensitive surface stabilizes for the period of the water-ice phase transition and the latent heat of ice formation is released or absorbed. A well-known thermoelectric sensor captures the indicated phase transition temperature, thereby determining the presence of ice formation, and the intensity of ice formation is estimated from the power supply of the heat pump (Peltier element) during this period, since this directly correlates with the phase transition heat released or absorbed.

Also, an indirect determination of the intensity, moreover, is fraught with large errors, since the power supply of the element of a working Peltier element strongly depends on the variable operating conditions (in particular, ambient temperature, heat exchange with the environment).

As the closest analogue (prototype) of the proposed thermoelectric sensor, a thermoelectric icing sensor was chosen, disclosed in the utility model patent RU 162213, published on May 27, 2016, IPC B64D 15/20. The known thermoelectric icing sensor contains a thermoelectric module made in the form of a Peltier element, which is connected to the thermoelectric heat flow sensor by its lower part, and its opposite upper part forms an external surface sensitive to ice formation and is equipped with a temperature sensor.

The thermoelectric module, made in the form of a Peltier element, provides a mode of cyclic heating-cooling of the sensitive outer surface of the upper part of the heat flow sensor in the temperature range of ice cover formation.

The thermoelectric heat flow sensor, in case of the presence of ice or a predisposition to ice formation on the sensitive surface of the upper part, detects the release or absorption of the latent heat of ice formation by the appearance of a signal corresponding to the heat flow through it, and the temperature sensor at the same time records the temperature of ice formation.

The well-known thermoelectric icing sensor makes it possible to determine the intensity of ice formation by integrating the heat that has passed through the built-in heat flow sensor during the period of ice formation. This amount of heat, with a known specific heat of ice formation, makes it possible to determine the amount of ice or water (or the thickness of the layer in the measuring cell).

The disadvantage of such an icing sensor is significant errors in determining the temperature of ice formation. This is due to the fact that the temperature sensor located directly on the surface of the heat flow sensor above the cooling (or heating) surface of the Peltier element (Fig. 1) fixes the temperature of the phase transition inaccurately. Its intermediate location between the temperature zones, the ambient temperature zone and the temperature zone created by the Peltier element leads to the fixation of the intermediate temperature at the moment of ice formation. Water and aqueous solutions are characterized by a noticeable overcooling before spontaneous crystallization, which means that at the moment crystallization begins, the temperature of the sensor structure elements near the crystallization zone is noticeably lower than the crystallization temperature.

Thus, due to the intermediate location, between the environment and the Peltier element, the temperature sensor detects a temperature below the true ice crystallization temperature. In particular, this error increases with decreasing ice-water sample on the sensitive surface.

To increase the measurement accuracy of such sensors, noticeable empirical corrections are made that take into account the parasitic effects of the ambient temperature, which reduces the accuracy and reliability of the results obtained.

The technical problem to be solved by the present utility model is to increase the accuracy of measuring the quantitative characteristics of determining ice formation by a thermoelectric sensor.

The technical result achieved when solving a technical problem is to increase the sensitivity to ice formation or predisposition to it while increasing the accuracy of determining ice formation or a predisposition to its occurrence.

The technical problem is solved, and the technical result is achieved due to the fact that the thermoelectric icing sensor includes the first thermoelectric block, the temperature sensor, the second thermoelectric block, the heat-conducting plate, the protective shell and the base. The first thermoelectric block contains the first thermoelectric element and the first thermoelectric heat flow sensor mounted on it, and the second thermoelectric block contains the second thermoelectric element and the second thermoelectric heat flow sensor mounted on it. The first and second thermoelectric blocks are mounted on the base spaced from each other. A heat-conducting plate is installed over the first and second thermoelectric blocks, and a temperature sensor is placed separately in the gap between the first and second thermoelectric blocks on the inner side of the heat-conducting plate. The first and second thermoelectric elements are electrically connected to each other, and the first and second thermoelectric heat flow sensors are electrically connected in series to each other. The first and second thermoelectric blocks, the temperature sensor and the heat-conducting plate are enclosed in a protective shell, open in the area of the heat-conducting plate to form a cuvette, the bottom of which is the outer side of the heat-conducting plate, and the protective shell is the walls.

The technical problem is solved, and the technical result is also achieved in the following particular embodiments of the thermoelectric sensor.

The heat-conducting plate can be made of metal or heat-conducting ceramics.

The thermoelectric elements may be Peltier elements.

The containment can be made from a material with low thermal conductivity, in particular from a polymeric material with low thermal conductivity.

The heat-conducting plate mounted on the first and second thermoelectric heat flux sensors is made of a material having a high thermal conductivity, such as metal or heat-conducting ceramics. This design of the heat-conducting plate allows you to quickly measure the minimum temperature change in the cuvette, and, therefore, increase the sensitivity to ice formation or a predisposition to it and the accuracy of determining ice formation or a predisposition to its occurrence.

Placement of the temperature sensor on the inner side of the heat-conducting plate ensures its direct thermal contact with the measured sample. And its isolation from thermoelectric blocks and location in the gap between them leads to the fact that the temperature effect of these elements on the temperature sensor is minimized, which in turn has a positive effect on the sensitivity to ice formation or predisposition to it and the accuracy of their determination.

The electrical connection of thermoelectric elements, both parallel and series, ensures their control as a single combined thermoelectric element. The electrical serial connection of thermoelectric heat flow sensors allows summing up their sensitivity and registering the heat flow signal as from a single heat flow sensor. Both ensure the coordinated operation of both blocks, and, therefore, increase the overall accuracy of determining ice formation or a predisposition to its occurrence.

The presence of two thermoelectric blocks, united by a heat-conducting plate and a temperature sensor located separately between them, allows more uniform absorption/transfer of thermal energy to the sample located on the heat-conducting plate, as a result of which the same temperature is ensured along the entire length of the heat-conducting plate. Thus, the temperature sensor, located separately and at the same time between the blocks, measures the temperature more closely corresponding to the temperature of the sample.

The conclusion of all structural elements located on the base, in a protective shell and its execution of a material with low thermal conductivity, allows you to protect the structure from mechanical and thermal influences from the outside. And the simultaneous formation of a cuvette from a diaphragm and a protective shell allows for targeted measurement of the sample temperature with minimization of external parasitic temperature effects. In other words, this minimizes the influence of any changes in ambient temperature outside the cuvette, and, therefore, provides an increase in sensitivity to ice formation or a predisposition to it and an increase in the accuracy of their determination.

Further, the present utility model is illustrated by the following drawings.

In FIG. 1 shows the design of a thermoelectric sensor.

In FIG. 2 shows a diagram of a cyclic change in the temperature of a thermoelectric icing sensor using a thermoelectric element (a - cooling phase, b - heating phase).

In FIG. 3 shows a graph of characteristic changes in temperature and heat flow in the operating ice sensor in the presence of water in the cuvette (cooling phase).

In FIG. 4 shows a graph of characteristic changes in temperature and the magnitude of the heat flux in a working icing sensor according to the prototype in the presence of water in the cuvette (cooling phase).

In accordance with the present utility model, the thermoelectric sensor is designed to be installed on any surface where ice formation is possible.

In FIG. 1 schematically shows the design of a thermoelectric sensor, which includes a first (1a) thermoelectric element and a second (1b) thermoelectric element, each of which is a thermoelectric module including n- and p-type semiconductor thermoelements.

On the outer sides of the first (1a) and second (1b) thermoelectric elements, the first (2a) and second (2b) thermoelectric heat flow sensors are located, also including n- and p-type semiconductor thermoelements with the formation of two thermoelectric blocks - "thermoelectric element - sensor heat flow" (1a-2a and 1b-2b). The first (1a) and second (1b) thermoelectric elements are interconnected to form an electrical circuit, and the first (2a) and second (2b) thermoelectric heat flow sensors are connected in series to form an electrical circuit. Between each other, each block "heat flow sensor - thermoelectric element" ("1a-2a" and "1b-2b") can be connected by any means known to a person skilled in the art, for example, by soldering metallized surfaces. On the outer sides of the first (2a) and second (2b) thermoelectric heat flow sensors there is a heat-conducting plate (4) connecting them.

To increase the sensitivity to ice formation, both thermoelectric blocks are mounted on the base (6) at a distance from each other with the formation of a gap. A heat-conducting plate (4) is installed over the first and second thermoelectric blocks. On the inner side of the heat-conducting plate (4) in the gap between the first and second thermoelectric blocks, a temperature sensor (3) is placed separately. Such mutual arrangement of structural elements eliminates the temperature influence of both thermoelectric blocks on the temperature sensor (3) during temperature measurement. To minimize external mechanical effects and the effect of changes in ambient temperature, the first (1a) and second (1b) thermoelectric elements, the first (2a) and second (2b) thermoelectric heat flow sensors, temperature sensor (3) and heat-conducting plate (4) are located on the base (6) are enclosed in a protective sheath (5) made of a material with low thermal conductivity, preferably a polymer. The use of such materials for the containment makes it possible to minimize the effect of ambient temperature changes due to the difficulty of heat exchange between the external environment and the structural elements of the thermoelectric sensor. The protective sheath (5) is open in the region of the diaphragm (4) to form a cuvette (7), the bottom of which is a heat-conducting plate (4), and the walls are the protective sheath (5). This cuvette (7), in combination with the thermal insulation of the remaining structural elements by means of a shell (5), allows accurate and timely local measurement of temperature changes. In other words, a change in the ambient temperature has a targeted effect exactly in the area where the thermoelectric sensor can measure it as accurately as possible.

Thermoelectric sensor works as follows.

In the case when the ambient temperature (Ta) is above the temperature range of ice formation, at the bottom of the cuvette there is water (A) with a temperature on the water surface (T1) and a temperature on the surface of the diaphragm (T2), then thermoelectric elements (1a and 1b) operate as coolers and cool thermoelectric heat flow sensors (2a and 2b). The arrows show the heat absorption Q by thermoelectric heat flow sensors (Fig. 2a). Thus, the outer surface of the heat-conducting plate (bottom of the cuvette), on which there may be a layer of water, is cooled.

Since the liquid is prone to supercooling, at the beginning of the process the temperature in the cuvette (7) on the outer sensitive surface of the diaphragm (4) drops below the ice formation temperature, a characteristic supercooling of the liquid sample occurs. Further, at the extreme supercooling of the sample, a spontaneous phase transition of the liquid into ice occurs with the release of a significant amount of heat, while the temperature of the sample rises to the phase transition temperature (for pure water - about 0°C). The moment of phase transition (ice formation) is recorded by both the temperature sensor (3) and thermoelectric heat flow sensors (2a and 2b) by the jump of their output signals (T) and (Flow), respectively (Fig. 3). In this case, the temperature sensor (3) shows the temperature of the phase transition at the maximum of the jump, and the integral of the heat flux emission measured by thermoelectric heat flux sensors during the phase transition is the heat of crystallization of the liquid.

In the case when the ambient temperature is below the temperature range of ice formation, at the bottom of the cuvette (7) there is ice (B) with a temperature on the surface of the ice layer (T1) and with a temperature on the surface of the diaphragm (T2), then thermoelectric elements (1a and 1b) work as heaters and heat thermoelectric heat flow sensors (2a and 2b). Arrows show heat Q released by thermoelectric heat flow sensors (Fig. 2b). Accordingly, the bottom of the cuvette (7), which may have a layer of ice, is heated.

As the sample is heated by thermoelectric elements (1a and 1b), the temperature increases and when the phase transition temperature is reached, for example, for water T _pl =0°C, the ice begins to melt. In this case, the temperature change in this layer stops and the heat of ice melting is absorbed. The specified heat flows through thermoelectric heat flow sensors (2a and 2b), while the temperature curve undergoes a characteristic inflection (see Fig. 3, right side). It is due to the fact that while the sample is completely melted, a significant amount of heat is absorbed, however, at the end of the melting process, the amount of heat Q changes sharply (the direction of the heat flow changes) and this is reflected in the course of the temperature curve. This effect can be used to determine the phase transition (melting) temperature by finding the inflection point by calculating the mathematical time derivative of the temperature curve.

Continuous icing monitoring includes successive heating and cooling cycles with accurate determination of icing or surface icing propensity in both phases (liquid crystallization and ice melting).

In FIG. Figure 3 shows typical readings of the temperature sensor (3) (T) and thermoelectric heat flow sensors (2a and 2b) (Flow) with uniform cooling by thermoelectric elements (1a and 1b) (U - supply voltage).

For comparison, in Fig. 4 shows a similar measurement cycle and typical readings of a temperature sensor (T) and a thermoelectric heat flow sensor (Flow) in an icing sensor manufactured according to a well-known utility model according to patent RU 162213 (prototype).

Comparing the graphs shows that in Fig. 3 shows a higher crystallization temperature measurement accuracy than FIG. 4. The measurement accuracy of the liquid-ice phase transition temperature obtained by measuring with the present utility model is within 0.5°C, which satisfies the requirements of practical applications. Moreover, the measurement of the phase transition temperature is possible both in the cooling phase (liquid-ice crystallization) and in the heating phase (ice-liquid melting).

The main disadvantage of the prototype is a large measurement error of the phase transition temperature (crystallization of water), which is noted in Fig. 4 as dT and is 5–10°C, which noticeably distorts the results obtained. In addition, there is no pronounced inflection in the temperature curve in the heating phase. This inaccuracy is due to the fact that the temperature sensor in the known sensor is located on the sensitive surface of the heat flow sensor, directly above the cold surface of the Peltier element. For this reason, the surface temperature of the Peltier element strongly influences the readings of the temperature sensor. In this case, due to the supercooling preceding the phase transition, all closely spaced structural elements around the temperature sensor (Peltier element surface) will be supercooled relative to the temperature of the crystallizing water in the cooling phase and overheated in the heating phase. Therefore, the temperature sensor in the prototype shows, in essence, an intermediate temperature between the phase transition temperature in the cuvette and the temperature of supercooled or superheated structural elements (Peltier element and thermoelectric heat flux sensor).

In the proposed utility model, this disadvantage is eliminated by moving the supercooled surfaces of thermoelectric blocks away from the phase transition temperature measurement zone. Placement of the heat-conducting plate (4) on thermoelectric blocks, which simultaneously functions as the bottom of the cuvette (7), allows more uniform absorption/transfer of thermal energy to the sample located on the heat-conducting plate (4), thereby ensuring the same temperature throughout the heat-conducting plate. In this case, the temperature sensor (3) located on the inner side of the heat-conducting plate (4) measures the temperature of the bottom of the measuring cuvette (7) in direct thermal contact with the liquid (ice) sample.

The proposed thermoelectric sensor for detecting icing or prone to icing of a surface can be widely used in the field of remote detection of icing or prone to icing of various surfaces.

Claims (6)

1. Thermoelectric sensor, including the first thermoelectric unit, containing the first thermoelectric element (1a) and the first thermoelectric heat flow sensor (2a) mounted on it, and the temperature sensor (3), characterized in that it includes the second thermoelectric unit, containing the second thermoelectric element (1b) and the second thermoelectric heat flow sensor (2b) installed on it, the base (6), on which the first and second thermoelectric blocks are mounted spaced from each other, the heat-conducting plate (4) installed over the first and second thermoelectric blocks, and the protective shell (5), and on the inside of the heat-conducting plate (4) in the gap between the first and second thermoelectric blocks, a temperature sensor (3) is separately placed, while the first (2a) and second (2b) thermoelectric heat flow sensors are electrically connected in series , and the first (1a) and second (1b) thermoelectric elements are ri- cally connected to each other, while the first and second thermoelectric units, the temperature sensor (3) and the heat-conducting plate (4) are enclosed in a protective sheath (5), open in the region of the outer surface of the heat-conducting plate with the formation of a cuvette (7), the bottom of which is the outer the surface of the heat-conducting plate (4), and the walls - the protective shell (5). 2. Thermoelectric sensor according to claim 1, in which the heat-conducting plate (4) is made of metal. 3. Thermoelectric sensor according to claim 1, in which the heat-conducting plate (4) is made of heat-conducting ceramics. 4. The thermoelectric sensor according to claim 1, wherein the thermoelectric elements (1a) and (1b) are Peltier elements. 5. Thermoelectric sensor according to claim 1, in which the protective sheath (5) is made of a material with low thermal conductivity. 6. Thermoelectric sensor according to claim 5, in which the protective sheath (5) is made of a polymeric material.

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