Datasheet

Kanthal Appliance Alloys Handbook 77
10
5. Design Calculations for Heating Elements
In this section an element is defined as the
combination of heating wire and any
supporting and connecting materials.
Electrical appliances equipped with a heating
element are being used in domestic as well as
industrial applications. Domestic applica-
tions are e.g. cooking, heating of
fluids, drying, ironing, space heating and
special purposes such as heating of beds,
aquariums, saunas, soldering irons and paint
strippers. Industrial applications are such as
heat treatment, hardening and drying of
inks, paints and lacquers. In vehicles, seats,
motors and rear view mirrors are frequently
electrically heated.
The appliance and the element must meet
requirements regarding performance, cost of
raw material and manufacture, life and
safety. The requirements may be opposed to
each other. A long life and a high degree of
safety means a low wire temperature, which
results in a long heating up time and often
also high raw material costs.
Domestic heating appliances must not
cause harm to individuals or damage to
property. Safety specifications for each
market may influence the design of the
appliance and the element and limit their
temperature.
The life of a well designed element de-
pends upon the make and the type of wire
used. Our FeCrAl and NiCr(Fe) wires have
excellent properties at high temperature and
provide the best possible life. It should be
kept in mind that the life of a wire increases
with wire diameter and decreasing wire tem-
perature.
Life test of elements.
Wire Temperature
For embedded and supported element types
the wire temperature depends upon both the
wire and the element surface load. For the
suspended element types the element surface
load in most cases cannot be defined. In
addition to the surface load, ambient tem-
perature, heating dissipating conditions and
presence and location of other elements will
influence the wire temperature and therefore
also the choice of wire surface load and ele-
ment surface load.