Lead the rod terminal pin diameter and the size of the electric heating tube of the power of the size of the matching value
Lead the rod terminal pin diameter and the size of the electric heating tube of the power of the size of the matching value
As the electric heating tube heating element tubular heater processing is completed, the general
sealing material for the RTV silica gel, the temperature is about 250 ℃, so the choice of the
rod in the work of the maximum working temperature must be ≤ 250 ℃ (RTV silicone maximum
temperature) then how to ensure that Kind of requirements?
Through the application examples to illustrate: the design of an electric heating tube
, specifications for the 220V4000W, the use of lead rod material for the stainless steel material
, the lead rod diameter diameter of φ2.6 × 75mm, this size selection is correct and reasonable?
We only through the calculation to see if it is correct and reasonable.
Solution: take φ2.6 lead rod, the length of 75 mm is equal to 0.075 meters
① in the lead out of the current flowing through:
I = P / U = 4000/220 ≈ 18.18 amps
② calculate the length of 75 mm, diameter φ2.6 mm resistance value
Since R = ρ.L / S = 0.7 × 0.075 / 3.142 × 1.32 ≈ 0.01 ohms
③ the power P produced when the rod is passed through 18.18 amps on a 75 mm lead rod
P = I2R = 18.182 × 0.01 ≈ 3.31 watts (ie, the lead rod is 75 mm long and the resulting power
is 3.31 watts)
④ at 75 mm, lead the rod φ2.6 corresponding to the tube surface load q bar
Q rod = P / S = 3.31 / 3.142 x 0.26 x 7.5 ≈ 0.54 g / cm 2
⑤ The stainless steel lead rod with a diameter of φ2.6 produces a total of 3.13 watts when
flowing through 18.18 amps and the corresponding surface load of the rod is 0.54 W / cm 2,
depending on the temperature of the tube surface load corresponding to the surface of the tube The
surface temperature of this stainless steel lead is about 200 ~ 220 ℃.
Conclusion: When the diameter of the heating rod of heated heating tube is φ2.6, and the
current flowing is 18.18 amps, the temperature of the rod is about 200 ~ 220 ℃, which is lower
than the normal temperature of 250 ℃, So meet the design requirements. If the temperature is
higher than the normal temperature of 250 ℃, the silica gel easily in the lead-out temperature
gradually crack occurs, resulting in insulation and electrical properties. May also be more than
the normal temperature caused by the carbonation of silica gel, resulting in the insulation of
the electric tube down even due to the carbonization of silica gel lead rod and tube shell
breakdown.
For the above situation, if more than 250 ℃ above can be improved as follows:
① According to the outer diameter of the electric heating tube, such as φ ≥ 10 mm, the
outer diameter of the lead rod can be increased or the length of the rod can be increased,
so the change can reduce the resistance value per unit length and reduce the load on the surface
of the rod, Although the current is still flowing through 18.18 amps, but the temperature of the
lead surface will drop to the temperature at which silicone can withstand even lower temperatures
.
② If the diameter such as φ ≤ 10 mm, it is still 18.18 amps current, may be appropriate to
lengthen or replace the lead out of the material, such as pure nickel lead rod and so on. It
should be noted that although the resistivity of the iron rod is lower than that of the stainless
steel, it is not recommended because the surface of the rod is easy to oxidize, the strength is
small and the contact resistance is not good.
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Eric Xie
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SKYPE: ericxie123@outlook.com
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