Dependence Θwallmax = f (γ) for the core channel with the maximum Θwallimax : 1 – the maximum wall temperature of identical channels with ϕ = 15.88 mm, of the central core area, when shaped under the condition that ΔTi = idem; 2 – the maximum wall temperature for any channel when shaped under the condition that Θwallimax = idem; 3, 4 – efficient shaping condition boundaries.