Datasheet

80 Kanthal Appliance Alloys Handbook
Examples
Tubular Element for a Flat Iron
Rating, P 1000 W
Voltage. U 220 V
Final tube diameter: 8 mm (0.315 in)
Final tube length: 300 mm (11.8 in)
If the terminal length inside the tube is 2 x
25 mm (2 x 1 in) the coil length (L
e
) will be
L
e
= 300 mm – (2 x 25 mm) = 250 mm
(9.8 in). Combining equation [9] and [10]
gives as hot resistance
Coils in grooved metal plates.
Metal sheathed tubular element.
P
R =
U
2
=
=
220
2
1000
48.4 Ω
According to equation [6] tubes surface load
becomes
If we aim at three times higher wire surface
load:
p
tube
=
P
=
=
π · d
tube
· L
e
· 0.01
W
cm
2
A
tube
P
=
π · 8 · 250 · 0.01
1000
= 15.91
= (103 W/in
2
)
According to equation [6] the wire surface
can be calculated to
p
wire
= 3 · p
tube
= 3 · 15.91 = 47.74 ≈ 48
W
cm
2
(309 W/in
2
)
KANTHAL D is a sensible choice and an
average wire temperature of 700 °C
(1290 °F) likely. Due to temperature factor
of resistance (C
t
for Kanthal D, table
chapter 2, = 1.05 ) the resistance at room
temperature is based on [2] calculated to:
R
T
= C
t
· R
20
➔ R
20
=
R
T
C
t
=
48.4
1.05
= 46.09 ≈
≈ 46.1 Ω
p =
P
A
c
=
48
A
c
1000
=
P
p
= 20.83 ≈
21 cm
2
(3.3 in
2
)
The ratio wire surface to resistance is
=
A
C
R
20
corresponding to a wire size of about
0.3 mm (0.012 in), based on the table for
KANTHAL D in chapter 9.
cm
2
Ω
= 0.455
21
46.1
,