Electrical heating device
OwnerIrina Loktev, Igor Papirovinventors
Life of this patent
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Abstract
An electric heating device includes a flexible resistor ribbon of alloy with high specific impedance, disposed in fiberglass or plastics net, forming insert, which is .
Claims44
An electrical heating device, for use in the air and/or for heating a structure, which device comprises:
- a insulating rigid or flexible shell, a flexible electric heating element including a flat continuous heating resistance ribbon, disposed inside the shell, wherein total area of the resistance ribbon meets the equation:
- A ribbon>P/{[(k1+k2)*t ribbon max/k saf]−(k1*t1+k2*t2)}, (1)
- where:
- A ribbon—the total area of the resistance ribbon;
- P—electrical power of the heating element;
- 4 k1 = 1 / [ ( A ribbon / A ) * ( 1 / ( α 1 + α 2 ) + ∑ i = 1 m1 δ i / λ i ) + δ / λ ] , ( 2 )
- 5 k2 = 1 / [ ( A ribbon / A ) * ( 1 / ( α 3 + α 4 ) + ∑ j = 1 m2 δ j / λ j ) + δ / λ ] , ( 3 )
- (for heating devices disposed with air on two sides) or
- 6 k2 = 1 / [ ( A ribbon / A ) * ( ∑ j = 1 m2 δ j / λ j ) + δ / λ ] ( 4 )
- (for heating devices having a heated structure at least on one side),
- t ribbon max—a maximal temperature of the resistance ribbon, which is admissible for said shell;
- k saf—safety factor determined considering possible rising of voltage, deterioration of conditions of thermo-dissipation, fuzzy operating of thermostats system;
- t1, t2—temperatures of environment on respective sides of the heating device, or the structure to be heated;
- A—total area of the shell;
- α1, α3—coefficients of heat transfer by convection from two different sides of the heating device or the structure to be heated, which border with air;
- α2, α4—coefficients of heat transfer by heat radiation from two different sides of the heating device or the structure to be heated, which border with air;
- λ, δ—respectively, coefficient of heat conductivity and thickness of the shell material or, if the shell has more than one layer, of the material of the layer directly contacting with the resistance ribbon;
- i, j—order number of a layer from of the structure to be heated, on a respective side of the heating device,
- m1, m2—total number of the layers of the heated structure from, respectively, first and second side of the heating device.
A high electrical resistance alloy suitable for processing into micro-dimensioned foils, consisting essentially of, by weight:
- 13.5-15.5% chromium;
- 4.5-6.5% aluminum;
- 0.3-1.1% silicon;
- 0.2-0.6% titanium;
- 0.01-0.1% cerium;
- and
- a balance of said alloy comprising iron with natural admixtures;
- wherein said chromium and said aluminum are of amounts which together satisfy the following relation:
- 17<X<21, wherein X=% Cr+% Al
The alloy of claim, 4, which contains additionally to 0.01% zirconium.
12 The electric heating device of claim 10, wherein said flexible electrical heating resistance ribbon is capable of being bent at any angle with radius of ribbon bending, less than triple thickness of the ribbon.
The electrical heating device of claim, 37,
- wherein the plastics sheath comprises two extruded layers, rendering said strip double-insulated.
Dependencies are inferred from the claim text.