Simulation of Induction Heating of Slabnsgsoft.com/pres/Induction Heating of Slab.pdf · 5.5 plus...
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Simulation of Induction Heating of Slab Elta 6.0 B1101 1D and 2D Options November 2, 2013
Transcript of Simulation of Induction Heating of Slabnsgsoft.com/pres/Induction Heating of Slab.pdf · 5.5 plus...
Simulation of Induction Heating of Slab
Elta 6.0 B1101 1D and 2D Options
November 2, 2013
Induction System Description Slab: • Material – low carbon steel • Dimensions: L x B x D = 200 x 120 x 20 cm • Temperatures: initial 20 C, final before transportation 1150 + 75 C • Weight of slab – 3.75 t • Production rate – 33 t/hr
Frequency selection: • Optimal frequency may be found using two major criteria: uniform heating in width and good electrical efficiency. Both criteria correspond to ratio D/δ = 3 (exact ratio must be π). If we use frequency 50 Hz, for hot conditions δ = 7 cm and D/δ = 2.86. Frequency 150 Hz was selected for the third inductor (D/δ = 5) in order to compensate slightly lower than optimal frequency of the first two inductors and thermal losses from the slab surface.
Simulation strategy
• 1D option was used for preliminary simulation, i.e. heating time, number of coils and their design, etc. This method isn’t actually 1D; special algorithm was developed in order to take into account heating of end zones. However this algorithm does not provide accurate results and does not give temperature distribution in the whole slab cross-section.
• 2D option was used for final adjustment of installation, calculation of the inductor parameters and temperature distribution in the slab cross-section.
• Both 1D and 2D options allow us to count for a final length of the system, including difference in lengths of the coil and work-piece
Single – Stage Heating; 1D Simulation
Temperature variations in time and in slab thickness are shown in figures on the right.
Temperature at the end of heating is in the range of 1100 – 1180 C.
After 10 sec of slab transportation the surface temperature drops to 1150 C.
To provide required production rate it is necessary to use 9 parallel lines.
Specific energy is 308 kWh/t.
With several iterations using 1D simulation it was found that one-stage heating requires power 1.45 MW and heating time 3600 sec.
Accelerated Heating; 1D Simulation 1D simulation was used for optimization of heating. Heating line contains three inductors with different turn numbers and thermal insulation. Transportation time from one inductor to another was selected 10 sec.
It was found that total heating time may be reduced to 3 x 120 + 2 x 10 = 1220 sec when using accelerated heating.
Mean power of inductors must be 8.6, 3.0 and 1.3 MW to achieve approximately the same temperature distribution as at one-stage heating (see pictures).
It was found that it is reasonable to use slightly higher frequency (150 Hz) for the 3rd inductor in order to compensate surface temperature reduction during the transportation.
Accelerated Heating; 1D Simulation
Elta 6.0 2D Option In addition to standard 1D calculations, 2D option allows the user to calculate and visualize the following items:
• Color maps of temperature, heat sources (power density) and magnetic field strength in the whole slab cross-section for any instant of heating - T,w,H = f(x,y @ any t).
• Color maps of temperature variation - T = f(x,t @ any y) or T = f(y,t @ any x)
• All color maps have a possibility to change scale range of presented values (use Scale button); it make possible to visualize gradients of presented values
• Curves of temperature, heat sources and field strength along horizontal or vertical centerlines for any instants T,w,H = f(x @y = 0 or y @ x = 0 for any t)
Because different items must be visualized and represented in the report it is recommended to create different templates for the same task when using 1D or 2D calculation options.
Report Pages with Some Input Data
Processing Stages:
1. "Heating/Power", duration: 400 s. 2. "Cooling", duration: 10 s.
f= 50 Hz, P= 8.6•10006
W. Media temperature:
Used inductor: 1 Text.surf= 20 °C.
Media temperature: aoutside= "Natural".
Text.surf= 20 °C.
aoutside= "Natural".
3. "Heating/Power", duration: 400 s. 4. "Cooling", duration: 10 s.
f= 50 Hz, P= 2.8•10006
W. Media temperature:
Used inductor: 2 Text.surf= 20 °C.
Media temperature: aoutside= "Natural".
Text.surf= 20 °C.
aoutside= "Natural".
5. "Heating/Power", duration: 400 s. 6. "Cooling", duration: 10 s.
f= 150 Hz, P= 1•10006
W. Media temperature:
Used inductor: 3 Text.surf= 20 °C.
Media temperature: aoutside= "Natural".
Text.surf= 20 °C.
aoutside= "Natural".
Integral parameters:
Stage N1 Coil Voltage = 1394.2 V Generator Voltage = 1394.2 VCoil Current = 12965 A Generator Current = 6837.2 A
Coil Impedance = 0.11029 W Generator Impedance = 0.20417 W Coil Power Factor = 0.48589 Generator Power Factor = 0.91309Workpiece Power = 6.9671E6 W Coil Power = 8.6E6 WGenerator Power = 8.6E6 W Electrical Efficiency = 0.81013Thermal Efficiency = 0.97772 Total Efficiency = 0.79251Field Strength = 1908.2 A/cm Magnetic Flux Density = 0 T
Coil Cooling Parameters Input Temperature= 20 °C; Output Temperature= 40 °C. Water Flow Rate= 1296.1 lt/min; Sections Number= 7 ; Pressure Drop= 0.21066 MPa.
Version: 6.0
Date: 11/17/2013 5:58:03 PM Page 4 of 9
Project: Slab heating
Project Information.Task type: Heating of a big magnetic steel slab (B x H x L = 150 x 20 x 200 cm) in three different inductors
Input Data.
Workpiece:
Shape: "Plate". Length (Z): 200 cm, Width (Y): 150 cm, Finite system length.
Layers:
1. "0.4 % C Steel anneal", Xint= 0 cm, Xext= 10 cm, width= 150 cm, T= 20 °C.
Inductors:
No 1: X: 17 cm, Z: 230 cm. Y: 164 cm. Number of turns: 36.
Z
X1
Tube profile: rectangle; A= 5 cm; T= 3 cm; d= 0.5 cm; Resistivity: 2•10-006
W • cm.
T
dA
Insulation:Layer 1: "Portland-cem. concr.", thickness: 4 cm.
Version: 6.0
Date: 11/2/2013 11:35:20 PM Page 1 of 9
Project: Slab heating
Heat Sources in 2D Simulation
Heat Source distribution along vertical centerline for different instances of the
first heating stage
Heat Source color map for a right corner of slab at the end of the first heating
stage, demonstrating power edge effect
Temperature Curves
Temperature dynamics: T(x = 0 and x = D/2 = 10), mean value and temperature
difference in thickness
Temperature distribution along the vertical centerline at different t
C
B
D
A
A B C D A
Temperature Distribution along Perimeter
Temperature curves are presented for the middle and end points of each heating stage
Map of Temperature along the Slab Thickness vs. Processing Time
Map is similar to that for 1D simulation
Power Density at the End of the First Heating Stage, W/cm3
Frequency 50 Hz
Power Density at the End of the Third Heating Stage, W/cm3
Frequency 150 Hz
Temperature Map after the First Heating Stage
Temperature Map at the End of Processing
Map of Temperature Difference after the Third Heating Stage
Numbers on the curves show real temperatures; colors correspond to temperature difference relative to the slab center
Dynamics of the Installation Parameters
Variation of temperatures in a plane Y = 0
Examples of Report Pages
Heat Sources Density vs. X and Y (at t = 292.857142857143 s.)
Y, cm
X, cm
0
5
10
15
20
25
2.385 4.77
4.77
7.155
7.155
7.155
9.54
9.54
9.54
11.93
11.93
11.93
14.31
14.31
14.31
16.7
16.7
19.08
21.47 23.85
01
2
3
4
5
6
7
8
9
0 10 20 30 40 50 60 70
Temperature vs. X and Y (at t = 1220 s.)
Y, cm
X, cm
1140
1160
1180
1200
1137 1147
1158
1168
1178
1178
1189 1189
1199
1199
1199
1199
1209
1209
0
1
2
3
4
5
6
7
8
9
0 10 20 30 40 50 60 70
Version: 6.0
Date: 11/2/2013 11:43:57 PM Page 7 of 9
Project: Slab heating
Temperature vs. X and Y (at t = 400 s.)
Y, cm
X, cm
200
400
600
800
1000
1200
627.8
772.2
916.7
1061
1061
1061
1206
0
2
4
6
8
0 10 20 30 40 50 60 70
Temperature vs. X and Y (at t = 1220 s.)
Y, cm
X, cm
1165
1175
1200
1250
1250
1250
1225
1225 1225
0
1
2
3
4
5
6
7
8
9
0 10 20 30 40 50 60 70
Version: 6.0
Date: 11/17/2013 10:56:47 PM Page 8 of 9
Project: Slab heating
Comparison of Powers
Case
Description
Coil Power , kW Total Power,
kW
Specific Energy kWh/t Coil 1 Coil 2 Coil 3
1 1D one step 1.45 x 9 13050 308
2 1D accelerated 8600 3000 1300 12900 300
3 2D accelerated 8600 2800 1000 12400 292
• 1D and 2D simulations (cases 2 and 3) give close results in integral power parameters • Accelerated heating allows to use one line with three inductors instead of 9 inductors for a single-stage heating providing the same production rate • Due to faster heating and optimized coil design used in accelerated version, specific energy was reduced for 5.2%
Conclusions • Elta 6 has all the options of previous versions of Elta including Elta 5.5 plus an option of 2D simulation of rectangular body heating
• Integral parameters of induction heater calculated using 1D and 2D options are rather close and 1D may be used for preliminary design of induction process (frequency selection, power stages, time)
• 2D simulation may be used for final design and accurate calculation of temperature in the whole cross-section of slab
• Elta 6 simulates 2D tasks in several minutes and may be effectively used for system and process optimization including multistage processes
Example of temperature distribution in the whole slab cross-section
