DE3030799A1 - ARRANGEMENT WITH COLD-CONDUCTING RADIATOR - Google Patents

Description

DR.-ING. WALTER ABITZ DR. DIETER F. MORF DIPL.-PHYS. M. GRITSCHNEDER Patent attorneys

Munich.

August 14, 1980

Postal address / F ⁵ OsIaI Address Postfach 800 109. BOOO Munich Hfl

l'ienzenauerslraöe 28

Telephone 98 3222

Telegrams: Chemindus Munich Telex: (0) 5 23992

MPO300

RAYCHEM CORPORATION

Menlo Park, Calif. 94025, V.St.A.

Arrangement with cold conductive radiator

130013/1128

The invention relates to self-regulating heating elements with an elongated strip made of a thermoconductive polymer, at least two parallel electrodes in electrical (and optionally also in physical) contact with the strip and an electrically insulating Sheathing. Such radiators are known and are, for example, in US Pat. Nos. 3,793,716, 3,823,217, 3,861,029; 4,177,376; and 4,188,276; and in the Thermal Design Guide from the Chemelex division of Raychem Corporation (H 5O19O 5O5 B5 1/78).

When describing such radiators, one often speaks of their "passive power output" and their "active power output". The "passive power output" of a radiator is the value of the expression V ² / R _Q , where R _{Q is} the resistance of the unit length (generally 1 foot or 1 meter) of the radiator at 21 ° C and V is the voltage of the power source to which the radiator is connected, usually 120 or 240 VAC. The "active power output" of a radiator is the measured power output of one unit of length of the radiator (generally 1 foot or 1 meter) when connected to a power source and a major surface of the radiator is in contact with a metal substrate that is at a temperature in the range of its intended use temperature of the radiator is kept, e.g. between 7 and 65 ° C, about 10 ° C for radiators that are to prevent the freezing of pipes, conventional heating tapes contain at least two electrodes in the form of wires that are embedded in a cold-conducting polymer element, and have at the intended operating voltage has a passive power output of well below 65 W / m (50 W / ft);

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MPO 300

the use of such radiators with a higher passive power output has not yet been considered, because there was at most a small usable increase in active power output and a considerable one Disadvantages, in particular a shorter useful life, were associated with it.

It has now been shown that if a radiator with cold-conductive polymer with a sheath made of metal or another material with good thermal conductivity is surrounded by the radiator with voltages at which the passive power output is above 165 W / m without the disadvantages that would otherwise be expected occurring, and that so that a valuable increase in active power output can be achieved. For example, it is surprisingly possible by adding such a cover to a voltage of 240 V a thermoconductive radiator to let work whose passive power output at 120 V is less than 165 W / m and at 240 V more than 165 W / m, and although such a radiator without such a cover at 240 V only has a very inadequate service life would exhibit.

The invention thus represents, in one respect, a method of heating in which the current is self-regulating Radiator assembly is sent, which is composed the end

(a) a thermoconductive radiator that is composed the end

(I) an elongated strip of an electrically conductive polymer approach that exhibits the behavior of a PTC resistor shows

(II) two elongated, parallel electrodes that make electrical contact with said strip have and

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(III) an electrically insulating jacket which surrounds said strip and said electrodes, and

(B) an envelope which surrounds the said cold conductive heating element and which is made from a material is whose thermal conductivity is at least 0.1 Cal / cm ° C see, preferably at least 0.3 Cal / cm ° C see; the supplied current comes from a current source with a voltage V, and the passive power output of the radiator at the stated voltage V is at least 165 W / m (50 W / ft), preferably at least 230 W / m (70 W / ft).

The radiator assembly can be used to heat a solid body, the envelope preferably being so shaped is that it can be applied to the solid body; you can also use the arrangement for space heating, in which If the arrangement is preferably in the form of a coil, air or a liquid in the space between the windings can circulate.

In another aspect, the invention provides a self-regulating radiator assembly with a thermally conductive radiator and an enclosure of the type specified above, wherein the radiator at 120 V has a passive power output of at least 165 W / m.

The cold-conductive heating element preferably comprises at least two electrodes in the form of wires, which are in the cold-conductive Strips are embedded and have physical contact with it. However, the invention also encompasses other types of cold-conducting radiators, for example radiators, in which at least one of the electrodes of the cold-conducting Strip is separated by a layer of another conductive material, for example a conductive one

130013/1 128

Polymer approach with ZTC behavior, or radiators, at which are provided with a sheet-like cold-conducting element and at least two sheet-like electrodes.

The passive power output of a radiator naturally depends on the specific resistance of the cold-conducting approach and the size and shape of the electrodes and the PTC element. In the case of a conventional heating tape, such as this, for example In the example below, the passive power output is preferably 165 to 655 W / m (50 to 200 W / ft), preferably 230 to 655 W / m (70 to 200 W / ft). For the most part under this Invention to be considered radiator, the preferred range of passive power output values can be better passed through Express a term that includes the width of the thermoconductive element in which the heat is generated. The passive one The power output of the radiators considered in the context of this invention is then preferably 217 d to 862 d, in particular 302 d to 862 d W / m, where d is the largest cross-sectional dimension (in centimeters) of the cold-conducting strip between the electrodes.

The active power output of the thermoconductive radiator is significantly increased by attaching the cover, and preferred radiator assemblies have an active power output at 10 ° C that is at least 1.5 times that of the active one Power output of the cold conductive radiator without such a cover, also at 10 ° C, corresponds.

The envelope preferably consists of two elongated thin plates, between which the heating element is layered, the thin plates touching each other on both sides of the radiator. The thin plates are preferably between 0.025 and 1.3 mm, e.g. 0.075 to 0.2 mm thick and consist of a material with thermal conductivity

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4 * 3030798

of at least 0.3, for example aluminum. You can be connected to each other and / or to the radiator by means of an adhesive, e.g. an epoxy adhesive.

It is important that the casing and the thermoconductive radiator are in intimate thermal contact with one another, and that the Sheath preferably touches (directly or through the use of an adhesive) at least the areas of the insulating sheath next to those parts of the radiator in which heat is generated. Preferably there are none free spaces between the casing and the radiator. The sheath preferably extends from the thermoconductive one Radiators from outwards in the form of baffles, so that the exposed area size of the envelope at least 1.5 times, e.g. at least 2 times the surface area of the insulating jacket of the cold conductive radiator, is best at least twice as much. The envelope can also act as protection against the ingress of oxygen the PTC thermistor connection serve as in US patent application Ser. No. 965,345.

The radiator arrangements can contain two or more than two thermoconductive radiators. The radiators can Be spaced from each other and can be connected by an envelope surrounding each one, e.g. a number parallel running heating tapes, which are layered between two thin metal plates.

The invention is illustrated in the accompanying drawings, which show:

Fig. 1 is an isometric view of a radiator assembly, partially in section;

Fig. 2 is a diagram of the relationship between the electrical

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tric current and the substrate temperature in the experiments described in the example.

Fig. 1 shows a thermoconductive radiator-again, the Has electrodes 1 and 2, which are embedded in a strip 3 made of a thermoconductive polymer, which in turn an insulating sheath 4 surrounds. The radiator is sandwiched between two thin aluminum plates 5 and 6, which are glued to each other and to the radiator by an adhesive (not shown).

The invention is further illustrated by the following example.

EXAMPLE

The cold conductive heating element used consisted of a 61 cm long cold conductive heating tape according to FIG. 1. As electrodes copper wires with a diameter of 1.3 mm and a center-to-center spacing of 7.6 mm were used. The cold conductive element was 10 mm wide and 1.8 mm thick and was composed of a dispersion of carbon black in a mixture of polyethylene and an ethylene / ethyl acrylate copolymer. The insulating jacket consisted of about 0.25 mm thick polyurethane. The radiator had a passive power output of about 250 to 275 W / m. The active power output of this radiator on its own or as part of a radiator arrangement was measured by placing the radiator or radiator assembly on an aluminum plate 1.25 15.25 χ 61 cm attached / connected to a 120 VAC source and awaited equilibrium of the system while maintaining the plate at a desired temperature. During the tests, the radiator was used alone (case A) or the radiator was placed between two similar aluminum sheets 61 cm long and 0.003 cm

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Layered thickness, the widths being 11.4, 6.3, 3.8 and 1.9 cm (cases B and C and D and E). Fig. 2 shows the relationships between the plate temperature and the current flowing through the radiator. The one below The table shows the calculated active power output (product of current and applied voltage) of the radiator at a plate temperature of 50 ° F (10 ° C).

Tabel

case Width of
Metal cladding (cm) Active performance
at 10 ° C (W / m) A. no 70 B. 11.4 140 '" C. 6.3 145 D. 3.8 150 E. 1.9 140

End of description.

130013/1128

Claims (1)

1.) Method of heating in which electricity is self-regulating Radiator assembly is conducted, which has a thermoconductive radiator, which is composed the end (I) an elongated strip of an electrically conductive polymer approach that exhibits the behavior of a PTC resistor shows (II) two elongated, parallel electrodes that are in electrical contact with the strip, and (III) an electrically insulating jacket which said strip and said electrodes surrounds characterized in that the heating element (a) is surrounded by a casing (3) made of a material exists, the thermal conductivity of which is at least 0.1 Cal / cm ° C see, and (b) with operating voltage a passive Has a power output of at least 165 W / m. 2. The method according to claim 1, characterized in that said cold-conducting radiator has a passive line 1 30q 13/1 1 28 MPO 300 D, power output from 217 d to 862 d W / m, where d is the largest cross-sectional dimension (in centimeters) of the cold conductive strip between the electrodes. 3. The method according to claim 1 or 2, characterized in that said cold-conducting radiator between two elongated thin plates (5, 6) are layered, which touch each other on both sides of the radiator and which consist of a material whose thermal conductivity is at least 0.3 Cal / cm ° C see. 4. The method according to claim 3, characterized in that the exposed surface of said thin plates (5, 6) is at least 1.5 times the area of the insulating jacket (4) of the thermoconductive radiator. 5. The method according to any one of the preceding claims, characterized in that the radiator at 10 ° C has active power output that is at least 1.5 times the active power output be body without the envelope 1.5 times the active power output at 10 ° C of a heating 6. The method according to any one of the preceding claims, characterized in that 'the supply voltage .120 or 240 VAC. 7. Self-regulating radiator arrangement with a thermoconductive radiator, which is composed of - 2 - '· ■ I 130013/1128 ORIGINAL INSPECTED MPO 300 (I) an elongated strip of an electrically conductive polymer approach that exhibits the behavior of a PTC resistor shows (II) two elongated, parallel electrodes that make electrical contact with the strip have and (III) an electrically insulating sheath covering said strip and said electrodes surrounds characterized in that said thermally conductive radiator (a) has a passive power output of at least 165 W / m at 120 V, and (b) is surrounded by a covering made of a material whose thermal conductivity is at least 0.1 Cal / cm ° C see. Radiator arrangement according to claim 7, characterized in that said cold-conducting radiator is between two elongated thin plates (5, 6) are layered, which touch each other on one of the two sides of the heater and which consist of a material whose thermal conductivity is at least 0.3 Cal / cm ° C see. 9. radiator assembly according to claim 8, characterized in that the exposed surface of said thin Plates (5, 6) make up at least 1.5 times the area of the insulating jacket (4) of the thermoconductive radiator. 10. radiator arrangement according to one of claims 7 to 9, 13 0 0 13/1128 MPO 300 characterized in that the radiator has an active power output at 10 ° C, which is at least corresponds to 1.5 times the active power output that is present on the cold-conducting radiator without the casing sets at 10 ° C. -A- 130013/1128