Parameter Optimization and Prediction Model of Induction Heating for Large-Diameter Pipe

Table 4

Variance analysis results of the orthogonal test of temperatures for pipe’s outer wall.

Sources of Variance	Degree of Freedom	Sum of Squares	Mean Square	F	Contribution Rate (%)	Significance
Current Frequency	4	0.996	0.25	31.63	21.28
Current Density	4	1.49	0.372	47.32	31.84
Air Gap	4	2.1	0.525	66.68	44.86
Error	12	0.095	0.008	--	2.02
Total	24	4.671	1.155	--	100

Note: indicates that the difference is significant; indicates that the difference is extremely significant.