Design of heating wire for high temperature furnace-Academic Document-高温炉生产厂家

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Design of heating wire for high temperature furnace

Release time：2020-05-23 Number of views：2104

Main design parameters of ferrochrome aluminum electrothermal alloy wire

wire diameter (mm)	sectional area (mm2)	cm2/m	0Cr25AL5		0Cr21AL6Nb		0Cr27AL7Mo2
wire diameter (mm)	sectional area (mm2)	cm2/m	weight kg/m	Ω/m,20℃	weight kg/m	Ω/m,20℃	weight kg/m	Ω/m,20℃
0.10	0.007854	3.142	0.00005576	180.8	0.00005576	184.6	0.00005576	194.8
0.12	0.01131	3.770	0.00008030	125.6	0.00008030	128.2	0.00008030	135.3
0.15	0.01767	4.712	0.0001255	80.36	0.0001255	82.05	0.0001255	86.58
0.17	0.02270	5.341	0.0001612	62.56	0.0001612	63.88	0.0001612	67.41
0.19	0.02835	5.969	0.0002013	50.08	0.0002013	51.14	0.0002013	53.96
0.21	0.03464	6.597	0.0002459	41.00	0.0002459	41.86	0.0002459	44.17
0.25	0.04909	7.854	0.0003485	28.93	0.0003485	29.54	0.0003485	31.17
0.27	0.05726	8.482	0.0004065	24.80	0.0004065	25.33	0.0004065	26.72
0.29	0.06605	9.111	0.0004690	21.50	0.0004690	21.95	0.0004690	23.16
0.31	0.07548	9.739	0.0005359	18.81	0.0005359	19.21	0.0005359	20.27
0.35	0.09621	11.00	0.0006830	14.76	0.0006830	15.07	0.0006830	15.90
0.40	0.1257	12.57	0.0008922	11.30	0.0008922	11.54	0.0008922	12.18
0.45	0.1590	14.14	0.001129	8.928	0.001129	9.117	0.001129	9.620
0.50	0.1963	15.71	0.001394	7.232	0.001394	7.385	0.001394	7.792
0.60	0.2827	18.85	0.002007	5.022	0.002007	5.128	0.002007	5.411
0.70	0.3848	21.99	0.002732	3.690	0.002732	3.768	0.002732	3.976
0.80	0.5027	25.13	0.003569	2.825	0.003569	2.885	0.003569	3.044
0.90	0.6362	28.28	0.004517	2.232	0.004517	2.279	0.004517	2.405
1.00	0.7854	31.42	0.005576	1.808	0.005576	1.846	0.005576	1.948
1.20	1.131	37.70	0.008030	1.256	0.008030	1.282	0.008030	1.353
1.40	1.539	43.98	0.01093	0.9224	0.01093	0.9419	0.01093	0.9939
1.60	2.011	50.27	0.01428	0.7063	0.01428	0.7212	0.01428	0.7610
1.80	2.545	56.55	0.01807	0.5580	0.01807	0.5698	0.01807	0.6013
2.00	3.142	62.83	0.02231	0.4520	0.02231	0.4615	0.02231	0.4870
2.20	3.801	69.12	0.02699	0.3736	0.02699	0.3814	0.02699	0.4025
2.50	4.909	78.54	0.03485	0.2893	0.03485	0.2954	0.03485	0.3117
2.80	6.158	87.96	0.04372	0.2306	0.04372	0.2355	0.04372	0.2485
3.00	7.069	94.25	0.05019	0.2009	0.05019	0.2051	0.05019	0.2165
3.50	9.621	110.0	0.06831	0.1476	0.06831	0.1507	0.06831	0.1590
4.00	12.57	125.7	0.08922	0.1130	0.08922	0.1154	0.08922	0.1218
4.50	15.90	141.1	0.1129	0.08928	0.1129	0.09117	0.1129	0.09620
5.00	19.63	157.1	0.1394	0.07232	0.1394	0.07385	0.1394	0.07792
5.50	23.76	172.8	0.1687	0.05977	0.1687	0.06103	0.1687	0.06440
6.00	28.27	188.5	0.2007	0.05022	0.2007	0.05128	0.2007	0.05411
6.50	33.18	204.2	0.2356	0.04279	0.2356	0.04370	0.2356	0.04611
7.00	38.48	219.9	0.2732	0.03690	0.2732	0.03768	0.2732	0.03976

At the beginning of the design of high temperature furnace, the selection of heating elements is particularly important, in the study of relevant thermal knowledge of technology, we are familiar with the design choice of electric heating wire.

1. Classification of electric heating wire:

Electric heating wire is divided into two categories: iron chromium aluminum heating wire and nickel chromium aluminum heating wire, of which iron chromium aluminum heating wire can be divided into the following grades according to the difference in temperature: 1Cr13Al4, 0Cr25Al5, 0Cr21Al6Nb, 0Cr27Al7Mo2, the latter two are high temperature electric heating wires, often used for industrial electric furnace heating, the temperature is 1000~1250 degrees (furnace temperature), the diameter of the furnace wire needs to reach more than 3mm. This parameter can be appropriately changed in the case of temperature change.

2, surface load calculation:

The surface load of the heating wire refers to the electric power that the heating wire can withstand per unit area, and the unit is: W/㎝2.

The surface load of the heating wire should be less than 1.5, and the normal value is between 1.0 and 1.5. If it is less than 1.0, the heating time will be extended and the efficiency of the work will be affected.

3, about the wiring method of electric heating wire:

Resistance wire wiring: single-phase, two-phase power supply using series or parallel, three-phase power supply using Y type or Δ type. No matter what the wiring method is, the total power is always the sum of the power of all single electric furnace bars, and there will only be changes in voltage and current.

Y-type wiring, also known as star-type wiring, refers to the industrial three-phase four-wire electrical access, so that the voltage of a single electric heating wire is 220V, the calculation formula is: R=U2/P, calculate the resistance is how much, according to the data provided on the meter resistance of various materials can be obtained a single electric furnace rod required length of electric heating wire L1. Next, it is necessary to calculate the surface load of the electric furnace wire, the formula is: P (power)/(3.14* wire diameter *L1) Note: The unit is cm. If the surface load is less than 1.5, it can be used, if it is greater than 1.5, it is necessary to increase the wire diameter and recalculate according to the above steps until it is less than 1.5.

Final length of electric heating wire: L=L1/ (3.14* spiral diameter) * spiral spacing, spiral spacing is usually 2 times the diameter of the furnace wire.

4. Calculation examples:

1. Material grade: 0Cr21Al6Nb

2. Resistivity: 1.45

3. Wire diameter: 2.4mm

4. Meter resistance = resistivity/cross-sectional area of the wire: 1.45/ (3.14*1.2*1.2mm) =0.32 ohms/meter

5. Finished resistance = (voltage * voltage)/power

6. Length of raw material = finished resistance/meter resistance

7. Weight per meter = specific gravity of material * cross-sectional area of silk: 7.1* (3.14*1.2*1.2) /1000=0.032kg/ meter

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