RU2143791C1 - Flexible heating element - Google Patents

Abstract

FIELD: electrothermics, manufacture of flexible polymer electric heaters of domestic and industrial assignment. SUBSTANCE: warp of current-conducting fabric in given flexible heating element is made from mass of insulation filaments placed between electrodes and weft is manufactured from complex current-conducting filaments arranged perpendicular to electrodes. Description gives mathematical relationships ensuring electric safety of resistive layer that are employed to calculate number n of current-conducting filaments per unit of length of resistive layer, number K of electrodes and number m of metallized filaments making them. Multicomponent filament of " sheath-core " structure is used in the capacity of complex current-conducting heat-liberating filament. "Sheath" of structure includes fluoride-carrying polyolefin based on carbon black-filled copolymer of tetrafluorideethylene with vinylidenfluoride and "core" has polykaproamode or glass fibers. EFFECT: increased electric safety and reliability of flexible heating element and of article with its usage as whole. 3 cl, 3 dwg, 1 tbl

Description

 The invention relates to electrothermics, in particular to flexible heating elements, the resistive layer of which is made in the form of fabric from complex electrically conductive threads, and can be used in everyday life, medicine, agricultural facilities, as well as devices for heating liquid and gaseous media used in various industries .

A woven electric heater is known in which the warp and weft are made of electrically conductive and non-conductive threads laid alternately in one of the fabric directions, and the electrodes are located along the warp (US patent N 3349359, CL H 05 B 3/34, 1967)
A woven heater is also known, the non-conductive threads of which are made of complex cotton fibers, the volume ratio of the non-conductive threads to the conductive warp threads is 1: 1 to 1: 1.5, and the volume ratio of the conductive warp and weft is 1: 1.5 to 1:10 (RF patent N 2046552, CL H 05 B 3/36, 1995)
In these inventions, the problem is solved to reduce the shrinkage of the resistive layer during the manufacturing and operation of heating elements.

 A similar problem is solved in a flexible heating element (USSR patent N 1794284 A3, class H 05 B 3/38, 1993, Bull. N 5) containing a resistive layer in the form of a conductive fabric, weft and the base of which is made of complex electrically conductive filaments, insulating filaments and metallized filaments, combined into electrodes, which are placed along the edges of the resistive element and surround complex electrically conductive polymer filaments.

 The main disadvantage of the known heating elements is that they do not regulate the ratio between the required technical characteristics of the heating element and the textile structure of the resistive layer necessary for their practical implementation. This circumstance may lead to a decrease in the reliability and durability of the flexible heating element.

 The closest analogue selected as a prototype is the invention according to USSR patent N 1794284.

 The main objective of the development is the creation of such a flexible heating element in which the listed disadvantages would be eliminated, and the textile structure of its resistive layer in the form of a conductive fabric would regulate the required technical parameters of the heating element for various operating conditions of products based on it.

 The technical result that can be obtained from the use of the invention is to increase the electrical safety and reliability of a flexible heating element and, as a consequence, the product as a whole.

где P - номинальная мощность нагревательного элемента, Вт;
γ_э - предельно допустимое тепловыделение на единицу длины электропроводящей нити, Вт/м;
A - длина резистивного слоя, м;
B - ширина резистивного слоя, м;
U - заданное напряжение питания, В;
R_n - линейное электрическое сопротивление электропроводящей нити, Ом/м,
а количество металлизированных нитей в электроде для четного m₁ и нечетного m₂ количества электродов должно соответствовать соотношениям

где P - номинальная мощность нагревательного элемента, Вт;
K^* - количество электродов на единицу ширины резистивного слоя, шт;
U - заданное напряжение питания, В;
γ_m - предельное тепловыделение с единицы длины металлизированной нити, Вт/м;
R_m - удельное электросопротивление металлизированной нити, Ом/м;
при этом комплексная электропроводящая тепловыделяющая полимерная нить имеет структуру "оболочка-ядро" и содержит в "ядре" поликапроамидные или стеклянные волокна, а в "оболочке" саженаполненный фторсодержащий полиолефин на основе сополимера тетрафторэтилена с винилиденфторидом при следующем соотношении ингредиентов, мас.%:
а) для "ядра" из поликапроамидных волокон:
поликапроамидные волокна - 62 - 56
сополимер тетрафторэтилена с винилиденфторидом - 23 - 25
печная сажа - 15 - 19
б) для "ядра" из стеклянных волокон:
стеклянные волокна - 69 - 54
сополимер тетрафторэтилена с винилиденфторидом - 19 - 20
печная сажа - 12 - 16
Отличительные признаки являются существенными, поскольку каждый из них в отдельности и совместно направлен на решение поставленной задачи и достижение нового технического результата.The main problem is solved and the technical result is achieved due to the fact that in a flexible heating element containing a resistive layer in the form of a conductive fabric, the weft and the base of which are made of complex electrically conductive heat-generating polymer threads, insulating threads and electrodes made in the form of metallized threads enveloping complex electrically conductive heat-generating polymer threads, according to the invention, the basis of the conductive fabric is made of an array of insulating threads placed between du electrodes, and the weft is made of complex electrically conductive heat-generating polymer filaments perpendicular to the electrodes, wherein n is the number of electrically conductive threads per unit length of the resistive layer and K ^* is the number of electrodes per unit width of the resistive layer should correspond to

where P is the rated power of the heating element, W;
γ _e - the maximum allowable heat per unit length of the conductive thread, W / m;
A is the length of the resistive layer, m;
B is the width of the resistive layer, m;
U is the specified supply voltage, V;
R _n - linear electrical resistance of the conductive filament, Ohm / m,
and the number of metallized threads in the electrode for an even m ₁ and an odd m ₂ number of electrodes should correspond to the ratios

where P is the rated power of the heating element, W;
K ^* is the number of electrodes per unit width of the resistive layer, pcs;
U is the specified supply voltage, V;
γ _m - ultimate heat release per unit length of the metallized yarn, W / m;
R _m - specific electrical resistance of a metallized thread, Ohm / m;
the complex electrically conductive fuel polymer thread has a shell-core structure and contains polycaproamide or glass fibers in the core, and a fluorinated polyolefin based on a tetrafluoroethylene-vinylidene fluoride copolymer is embedded in the shell in the following ratio of ingredients, wt.%:
a) for the "core" of polycaproamide fibers:
polycaproamide fibers - 62 - 56
copolymer of tetrafluoroethylene with vinylidene fluoride - 23 - 25
furnace soot - 15 - 19
b) for the "core" of glass fibers:
glass fibers - 69 - 54
copolymer of tetrafluoroethylene with vinylidene fluoride - 19 - 20
furnace soot - 12 - 16
Distinctive features are significant, since each of them individually and jointly aimed at solving the problem and achieving a new technical result.

As you know, the main technical parameter of any electric heating device is its electrical power. To ensure a specified value of this parameter, the resistive layer of the flexible heating element must contain complex electrically conductive heat-generating filaments oriented perpendicular to the electrodes, i.e. placed on the weft of conductive tissue, and their number should not be less than the value determined by the ratio n ≥ P / γ _e • A • B (I). With a smaller number of conductive heat-generating threads in the resistive layer, they will overheat and destroy and, as a result, the heating layer will fail. A similar result will be if some of the conductive threads are placed on the basis of the conductive fabric, i.e. oriented parallel to the electrodes. This circumstance is explained by the fact that when a conductive filament placed between the electrodes along the weft of the conductive fabric is broken, the electric current will be redistributed between the adjacent conductive threads, i.e. along an electrically conductive filament located perpendicular to the electrodes, the electric current at the breakage point is redistributed to neighboring electrically conductive filaments, overloads them through the weft with the formation of new breaks for some time, but not on adjacent filaments. The described process will be irreversible, involving more and more electrically conductive threads, up to the failure of the entire heating element.

При меньшем количестве электродов потребляемая электрическая мощность будет меньше заданной величины и, как следствие, температура поверхности нагревательного элемента будет ниже желаемой. При большом количестве электродов потребляемая мощность будет больше заданной величины, что неизбежно приведет к перегреву токопроводящих нитей и, как следствие, к выходу нагревательного элемента из строя.The distribution of the power supplied to the heating element between the electrically conductive heat-generating threads is carried out by means of electrodes of metallized threads. The number of such electrodes in the resistive layer, depending on the specified electrical and geometric parameters of the heating element, must correspond to the expression

With a smaller number of electrodes, the consumed electric power will be less than a predetermined value and, as a result, the surface temperature of the heating element will be lower than desired. With a large number of electrodes, the power consumption will be more than a predetermined value, which will inevitably lead to overheating of the conductive threads and, as a result, to the failure of the heating element.

При меньшем количестве металлизированные нити (при прохождении через них электрического тока) будут перегреваться и разрушать токопроводящие нити, огибающие их, что обязательно приведет к выходу нагревательного элемента из строя.The number of metallized strands in the electrode must correspond to the expressions

With a smaller number of metallized filaments (when an electric current passes through them) they will overheat and destroy the conductive filaments that envelope them, which will necessarily lead to the failure of the heating element.

 The use of complex electrically conductive shell-core filaments containing polycaproamide or glass fibers in the core and tetrafluoroethylene-vinylidene fluoride copolymer filled with furnace black in the shell will improve the processability and quality of the heating element during its manufacture and operation.

 These distinctive essential features are new, since their use in the prior art, analogues and prototype was not found, which allows us to characterize the proposed technical solution in accordance with the criterion of "novelty."

 A single set of new essential features with common known essential features allows us to solve the problem and achieve a new technical result, which allows us to characterize the new technical solution by significant differences compared with the prior art, analogues and prototype. The new technical solution is the result of research and development and creative contribution, obtained without the use of standard design solutions or any recommendations, in its originality and substantiveness of execution meets the criterion of "inventive step".

 In FIG. 1 shows a fragment of a conductive fabric for a resistive layer of a heating element: in FIG. 2 shows a resistive layer with an even (a) and an odd (b) number of electrodes in an embodiment; in FIG. Figure 3 shows the structure of a complex electrically conductive fuel thread containing polycaproamide or glass fibers in the “core”, and a filled polymer of tetrafluoroethylene with vinylidene fluoride in the “sheath”.

 A fragment of the conductive fabric for the resistive element contains an array of insulating threads 1 located between the electrodes 2, and complex electrically conductive heat-generating threads 3, oriented perpendicular to the electrodes. The number of complex electrically conductive fuel fibers is determined based on the specified technical parameters of the heating element and the structural parameters of the conductive fabric.

The technical parameters of the heating element include power (R, W), supply voltage (U, B) and the overall dimensions of the resistive layer - length (A, m) and width (B, m). Based on the above parameters, it is necessary to determine the structural parameters of the resistive layer, namely: the number of complex electrically conductive heat-generating threads per unit length of the resistive layer (n / A, pcs / m); the number of electrodes (K ^* , pieces) and the number of metallized threads in the electrode (m, pcs). The calculations of these parameters are presented below.

II. Расчет системы распределения электропитания. На фиг. 2 представлены вариантные исполнения резистивного слоя с различным количеством электродов, скоммутированных между собой при помощи тоководов 4. Как видно из эскизов резистивного слоя, представленных на фиг. 2, A и B -соответственно длина и ширина резистивного слоя, L - расстояние между электродами, а количество электродов равно K^* = K + 1, где K - количество полос из массива электроизоляционных нитей. Исходя их этого
K = B/L или L = B/K.I. Definition n. As is known, the limiting heat release of the i-th filament (before failure) is determined by the coefficient γ _e (W / m). Hence, the total heat release of the nth number of threads corresponding to the power of the heating element is determined from the ratio
P ≤ n • γ _e • A • B or n • γ _e • A • B ≥ P,
from here

II. Calculation of the power distribution system. In FIG. 2 shows variant versions of the resistive layer with a different number of electrodes connected to each other by means of current leads 4. As can be seen from the sketches of the resistive layer shown in FIG. 2, A and B, respectively, the length and width of the resistive layer, L is the distance between the electrodes, and the number of electrodes is K ^* = K + 1, where K is the number of strips from an array of electrical insulating threads. Proceeding from this
K = B / L or L = B / K.

The calculation of the power distribution system in the heating element is determined from the fact that the number of complex electrically conductive threads per unit length of the resistive layer (n) is known; dimensions of the resistive layer A and B (length and width, respectively) (m); linear electrical resistance of a complex conductive filament (R _n , Ohm / m).

В соответствии с вышеизложенным количество электродов в резистивном слое в зависимости от задаваемых электрических и геометрических параметров нагревательного элемента определяется соотношением

III. Определение количества металлизированных нитей в электроде. Определение количества металлизированных нитей в электроде производим с учетом того, что ток, поступающий от источника питания на электроды, не должен приводить к разрушению металлизированных нитей, составляющих эти электроды. Суммарный ток, текущий по резистивному слою, равен
I = P/U,
где P - мощность нагревательного элемента, Вт;
U - заданное напряжение питания, В.We determine the electrical resistance of a fragment of the resistive layer (R ₁ ) located between adjacent electrodes, and the resistive layer (R) as a whole:
R ₁ = R _n • L / A • n, R = R ₁ / K = 1 / K • R _n • L / A • n;
based on the fact that L = B / K, we obtain R = 1 / K • R _n B / A • n • K;
it is known that P = U ² / R, then R = U ² / P
or K ² = P • B • R _n / U ² • A • n, whence

In accordance with the foregoing, the number of electrodes in the resistive layer, depending on the specified electrical and geometric parameters of the heating element, is determined by the ratio

III. Determination of the number of metallized threads in the electrode. We determine the number of metallized threads in the electrode, taking into account the fact that the current supplied from the power source to the electrodes should not lead to the destruction of the metallized threads that make up these electrodes. The total current flowing through the resistive layer is
I = P / U,
where P is the power of the heating element, W;
U is the set supply voltage, V.

This current is distributed between the electrodes. If the electrodes are K, then a current flows through each of them:
a) for an even number of electrodes
I _k = 21 / K ^* = 2P / K ^* • U,
b) for an odd number of electrodes
I _k = 21 / K ^* -1 = 2P / (K ^* -1) • U.

The current flowing through the electrodes, in turn, is distributed between its metallized filaments. If these threads are m, then a current I flows through each of them, equal to:
a) for an even number of electrodes
I ₁ = 2P / K ^* • U • m,
b) for an odd number of electrodes
I ₁ = 2P / (K ^* -1) • U • m.

In this case, the current passing through the metallized thread should not destroy it, i.e., the heat release caused by the passage of current should not exceed the maximum heat release for this type of metallized thread. If we denote the limiting heat release per unit length of a metallized thread by m (W / m), then, according to Ohm's law
I $\genfrac{}{}{0ex}{}{\text{2}}{\text{i}}$ • R _m ≤ γ _m ,
where R _m is the electrical resistivity of the metallized yarn, Ohm / m.

или

б) для нечетного количества электродов

или

Не менее важной задачей являлась разработка комплексных электропроводящих тепловыделяющих нитей резистивного слоя, которые обеспечивали бы работоспособность гибкого нагревательного элемента.Then the number of metallized threads (m) in the electrode is:
a) for an even number of electrodes

or

b) for an odd number of electrodes

or

An equally important task was the development of complex electrically conductive heat-generating threads of the resistive layer, which would ensure the operability of a flexible heating element.

 The structure of the developed complex electrically conductive fuel yarns shown in FIG. 3 consists of a “core” based on polycaproamide 5 and glass 6 fibers, around which a conductive composition 7 of a carbon black tetrafluoroethylene-vinylidene fluoride copolymer is localized.

 The choice of a copolymer of tetrafluoroethylene with vinylidene fluoride (hereinafter referred to as the "copolymer") is due to the fact that the copolymer of the known fluorine-containing polyolefins in combination with furnace black has the lowest electrical resistivity. This is due to the fact that highly structured furnace black is hydrophobic and combines well with fluorine-containing polyolefins. In addition, oxygen-containing complexes are practically absent on the surface of elementary particles of furnace soot, which is important for obtaining a composition with a high proportion of the use of conductive material.

However, the yarn from the composition "copolymer + carbon black" can be subjected to significant plasticization hoods, reaching 500%. This circumstance required the introduction of a reinforcing element, the “core,” into the structure of the thread. The main requirements for the reinforcing element of the multifilament yarn were as follows: high mechanical strength and chemoresistance. In view of the above, of all types of fibers, polycaproamide ones are most acceptable, but to create heating elements operating in the range 130-180 ^o C, it is necessary to use glass fibers as the "core" of the complex filament.

 The manufacturing technology of complex electrically conductive polymer filaments by the "dry" molding method is a process whose main operations are given in the examples below.

Example 1. A solvent — acetone and a copolymer — comes from a measuring device to a desolver. A predetermined amount of soot is charged through a nozzle and a spinning solution is prepared. Next, carbon black particles are dispersed in a rotary pulsation mixer and, after evacuation, the resulting solution is fed into a spinneret kit, where a fibrous filler is simultaneously fed. The die ends with a hole of 0.9 - 1.1 mm, which regulates the thickness of the applied layer. Upon exiting the spinneret, the fibrous filler enters the mine, where countercurrent hot air is supplied, heated to a temperature of 120 - 135 ^o C. At the same time, acetone is removed from the mine for regeneration, and the complex electrically conductive thread is taken for packaging for further processing into a fabric filler with specified technical and textile characteristics. In the process of manufacturing a complex electrically conductive thread according to example 1, the ingredients were taken in the following proportions, wt.%:
copolymer of tetrafluoroethylene with vinylidene fluoride - 24
furnace soot - 10
polycaproamide fibers - 66
Example 2. Carried out analogously to example 1 in the following ratio of ingredients of the multifilament yarn, wt.%:
copolymer of tetrafluoroethylene with vinylidene fluoride - 23
furnace soot - 13
polycaproamide fibers - 64
Example 3. Carried out analogously to example 1 in the following ratio of ingredients of the multifilament yarn, wt.%:
copolymer of tetrafluoroethylene with vinylidene fluoride - 23
furnace soot - 15
polycaproamide fibers - 62
Example 4. Carried out analogously to example 1 in the following ratio of ingredients of the multifilament yarn, wt.%:
copolymer of tetrafluoroethylene with vinylidene fluoride - 25
furnace soot - 19
polycaproamide fibers - 56
Example 5. Carried out analogously to example 1 in the following ratio of ingredients of the multifilament yarn, wt.%:
copolymer of tetrafluoroethylene with vinylidene fluoride - 26
furnace soot - 22
polycaproamide fibers - 52
Example 6. Carried out analogously to example 1 in the following ratio of ingredients of the multifilament yarn, wt.%:
tetrafluoroethylene-vinylidene fluoride copolymer - 16
furnace soot - 09
glass fibers - 75
Example 7. Carried out analogously to example 1 in the following ratio of ingredients of the multifilament yarn, wt.%:
copolymer of tetrafluoroethylene with vinylidene fluoride - 17
furnace soot - 10
glass fibers - 73
Example 8. Carry out analogously to example 1 in the following ratio of ingredients of the multifilament yarn, wt.%:
copolymer of tetrafluoroethylene with vinylidene fluoride - 19
furnace soot - 12
glass fibers - 69
Example 9. Carried out analogously to example 1 in the following ratio of ingredients of the multifilament yarn, wt.%:
copolymer of tetrafluoroethylene with vinylidene fluoride - 20
furnace soot - 16
glass fibers - 64
Example 10. Carried out analogously to example 1 in the following ratio of ingredients of the multifilament yarn, wt.%:
copolymer of tetrafluoroethylene with vinylidene fluoride - 22
furnace soot - 18
glass fibers - 60
The test results for determining the physico-mechanical and electrophysical characteristics of complex electrically conductive threads in examples 1-10 are presented in the table.

 Analysis of the data presented in the table shows that the most acceptable are the complex electrically conductive threads according to examples 3, 4 (the "core" is made of polycaproamide fibers) and 8, 9 (the "core" is made of glass fibers), since the threads from these compositions have the smallest linear electrical resistance (1400-1500 Ohm / m for threads based on kapron and 1250-1300 Ohm / m for threads based on glass) and have minimal elongation at break. In addition, these threads have a high-quality shell that is not damaged in the process of processing it into fabric.

 Examples of calculating the resistive layer of a heating element using the developed complex shell-core filaments containing a carbon black filled tetrafluoroethylene-vinylidene fluoride copolymer in the shell and a filler based on polycaproamide (option I) or glass fibers (option II) are presented in the “core” below.

 An example of calculating the structure of a resistive layer (option I).

 Set: nominal power of the heating element P = 2000 W; supply voltage U = 220 V; length A = 5 m; width B = 1 m.

 It is required to determine the structure of the resistive layer that provides the specified technical parameters.

или
n = 2000/0,5•5•1 = 800 нитей/метр.Decision. As a heat-generating complex electrically conductive thread, we select the thread according to example 3 (see table), the linear electrical resistance of which R _n = 150,000 Ohm / m with a maximum allowable heat release per unit length of the thread γ _e = 0.5 W / m. Using the expression I, we determine the number of complex threads per unit length of the resistive layer:

or
n = 2000 / 0.5 • 5 • 1 = 800 threads / meter.

или

Округлим полученное выражение до целых чисел (без учета дробной части) и путем повторного использования выражения II определим количество тепловыделяющих нитей на единицу длины резистивного слоя:
n = R•B•R_n/U²•A(K^*-1)² или
n = 2000•150000•1/48400•5(2-1)² = 1239 нитей/метр.Using expression II, we will calculate to determine the required number of electrodes in the resistive layer:

or

Round the resulting expression to integers (excluding the fractional part) and by reusing expression II, we determine the number of heat-generating threads per unit length of the resistive layer:
n = R • B • R _n / U ² • A (K ^* -1) ² or
n = 2000 • 150000 • 1/48400 • 5 (2-1) ² = 1239 threads / meter.

 Thus, the desired resistive layer should contain n = 1239 complex filaments per unit length of the resistive layer and two electrodes of metallized filaments located at the edges of the resistive layer and enveloping complex electrically conductive filaments.

или

.Using expression III, we determine the number of metallized strands in the electrode, taking into account the fact that we used a M8K2 filament based on copper with a specific electrical resistance R _m = 1 Ohm / m and maximum heat emission per unit length γ _m = 0.5 W / m.

or

.

 Thus, to ensure the reliability of the heating element with the specified parameters, the resistive layer should contain 1239 filaments per 1 m of its length, which is placed between two electrodes of 13 metallized filaments of type M8K2 each.

 An example of the calculation of the resistive layer (option II).

 Set: nominal power of the heating element P = 3000 W; supply voltage U = 36 V; length A = 1 m; width B = 1 m.

Decision. Set the type and number of heat-generating threads. Suppose that we (as in the example of option I) use a multifilament yarn containing polycaproamide fibers in the “core” (see table, example 3), whose linear electrical resistance is R _n = 150,000 Ohm / m with a maximum heat release of γ _e = 0.5 W / m. The linear density is 55 tex and provides a maximum textile density of 2000 yarns / meter length of conductive fabric.

Полученное значение выше максимально реализуемой величины при ткачестве текстильной плотности (2000 нитей/метр) комплексной тепловыделяющей нити с "ядром" из поликапроамидных волокон. Следовательно, необходимо использовать комплексную электропроводящую нить с большим предельно допустимым тепловыделением.To ensure the operability of the heating element, the number of heat-generating filaments per 1 m of the length of the resistive layer according to expression I should be

The obtained value is higher than the maximum realized value when weaving textile density (2000 threads / meter) of a complex heat-generating thread with a “core” of polycaproamide fibers. Therefore, it is necessary to use a complex electrically conductive thread with a large maximum allowable heat generation.

The table shows that the most acceptable is a complex electrically conductive thread with a "core" of glass fibers, the linear electrical resistance of which R _n = 120,000 Ohm / m with a maximum allowable heat emission γ _e = 1.5 W / m (table, example 9) . The linear density is 100 tex and provides a maximum textile density of 1,600 yarns / meter of length of conductive fabric.

или
n = 3000/1,5•1•2 = 1000 нитей/метр;
т. е. указанная нить обеспечит работоспособность нагревательного элемента, соответствующую заданным характеристикам.According to the expression I, in this case, the number of electrically conductive fuel fibers per 1 m of the length of the resistive layer will be

or
n = 3000 / 1.5 • 1 • 2 = 1000 threads / meter;
i.e., the specified thread will ensure the operability of the heating element corresponding to the specified characteristics.

или

Округлив полученное значение до целых чисел (без учета дробной части) и путем повторного использования выражения II уточним количество тепловыделяющих нитей на единицу длины резистивного слоя:
n = R_n•P•B/U²•A(K^*-1)² или
n = 120000•3000•2/362•1(24-1)² = 1050 нитей/метр.Using expression II, we carry out a preliminary assessment of the required number of electrodes in the resistive layer:

or

Rounding the resulting value to integers (excluding the fractional part) and by reusing expression II, we clarify the number of heat-generating threads per unit length of the resistive layer:
n = R _n • P • B / U ² • A (K ^* -1) ² or
n = 120000 • 3000 • 2/362 • 1 (24-1) ² = 1050 threads / meter.

 Thus, a resistive layer with overall dimensions S = A • B = 1 m • 2 m = 2 m should contain 1050 complex electrically conductive filaments with a “core” of glass fibers and 24 electrodes of metallized filaments arranged uniformly across the width of the resistive layer.

или

.Using expression III, we determine the number of metallized filaments in each electrode, taking into account the fact that a metallized copper filament of grade M8K2 with a specific electrical resistance of R _m = 1 Ohm / m and a maximum heat release of γ _m = 0.5 W / m was used.

or

.

 Thus, to ensure the operability and reliability of the heating element with the specified parameters, the resistive layer must contain 1050 complex electrically conductive threads with a “core” of glass fibers and 24 electrodes of 10 metallized threads of the M8K2 brand each, placed uniformly across the width B of the resistive layer (2- and along the edges and 22 in between).

 Testing of the developed flexible heating element on the basis of the resistive layer calculated in accordance with I-IV ratios, created on the basis of complex heat-conducting electrically conductive threads of the shell-core type from a black-filled copolymer and fibrous fillers, showed high reliability and performance during the operation of various products.

 Thus, the proposed new technical solution in the specified set of essential features meets the criterion of "industrial applicability", i.e. level of invention.

Claims (3)

1. A flexible heating element containing a resistive layer in the form of a conductive fabric, ducks and the base of which are made of complex electrically conductive heat-generating polymer filaments, insulating filaments and electrodes made in the form of metallized filaments, enveloping complex electrically conductive heat-producing polymer filaments, characterized in that the base is conductive the fabric is made of an array of insulating threads placed between the electrodes, and the weft is made of complex electrically conductive heat-generating polymer s yarns arranged perpendicular to the electrodes, wherein the n - number of conductive filaments per unit length of the resistive layer and K * - number of electrodes per unit width of the resistive layer should correspond to relations:

where P is the rated power of the heating element, W;
γ _e - the maximum allowable heat per unit length of the conductive thread, W / m;
A and B, respectively, the length and width of the resistive layer, m;
U is the specified supply voltage, V;
R _n - linear electrical resistance of the conductive filament, Ohm / m 2. The flexible heating element according to claim 1, characterized in that the number of metallized threads in the electrode for an even m ₁ and an odd m ₂ number of electrodes should correspond to the ratios:

where P is the rated power of the heating element, W;
K * is the number of electrodes per unit width of the resistive layer, pcs .;
U is the specified supply voltage, V;
γ _m - ultimate heat release per unit length of the metallized yarn, W / m;
R _m is the electrical resistivity of the metallized yarn, Ohm / m. 3. A flexible heating element according to any one of claims 1 and 2, characterized in that the complex electrically conductive heat-generating thread has a shell-core structure and contains polycaproamide fibers in the core, and a fused fluorinated polyolefin based on a copolymer in the shell tetrafluoroethylene with vinylidene fluoride in the following ratio of ingredients, wt.%:
Polycaproamide fibers - 62 - 56
Tetrafluoroethylene copolymer with vinylidene fluoride - 23 - 25
Chimney soot - 15 - 19
4. The flexible heating element according to any one of claims 1 and 2, characterized in that the complex electrically conductive fuel thread has a shell-core and core structure of the complex electrically conductive fuel thread contains glass fibers in the following ratio of ingredients, wt.%:
Glass fibers - 69 - 64
Tetrafluoroethylene copolymer with vinylidene fluoride - 19 - 20
Stove soot - 12 - 16

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