x-OnN Nux' 100 10 3 0.01 Nux Nuo-x Uniform wall heat flux Uniform wall Nux temperature Nuo-x 0.1 1/2 x/Dn Reph Pr 8.23 7.54 Figure 3.14 Heat transfer in the thermal entrance region of a parallel-plate duct with Hagen-Poiseuille flow. (Based on data from Ref. 10.) Nux = 7.55 + 0.024x-1.14 1.14 (0.0179P0.17-0.64 (1+0.0358P0.17 7x=0.64)2 0.17-0.64- Nuo-x = 7.55 + 0.024x-1.14 1+0.0358P0.17-0.64 - 0.14) (3.102) (3.103) The pressure drop over the hydrodynamically developing length x, or AP = P(0) P(x), can be calculated with [10] - ΔΡ PU₂ = 13.74(x+)1/2+ 1.25 +64xx-13.74(x+)1/2 1+0.00021(x+)-2 (3.104)