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6 – Modelling The following Gnielinski correlations for laminar and turbulent flow as well as for flow in the transition zone, conforms with a deviation of ±15% with experimental data (VDI, 1993): Laminar flow (i.e. Re ≤ Recrit): ⎛ ⎡ ⎛d ⎞0.9⎤ ⎞ ⎛Pr ⎞0.14 Nu =⎜3.66+0.08⋅⎢1+0.8⋅⎜ h ⎟ ⎥⋅Rem⋅Pr1/3 ⎟⋅⎜ b ⎟ (6.21) where: 0.3164 ⎛ d ⎞0.5 f= 0.25 +0.03⋅⎜ h⎟ L⎜ ⎢⎝D⎠⎥ ⎟⎝Prw⎠ ⎝⎣⎦⎠ where: ⎛d ⎞0.194 m=0.5+0.2903⋅⎜ h ⎟ The subscript h refers to the hydraulic diameter of the tube or annulus, whereas w and b refer to the properties of the fluid at wall and bulk temperature, respectively. Turbulent flow (i.e. Re ≥ 22 000): ⎛f⎞ ⎝D⎠ (6.22) ⎜ 8⋅Re⋅Pr ⎟ ⎛Prb ⎞0.14 NuT =⎜ 0.5 ⎟⋅⎜Pr ⎟ (6.23) ⎜⎛f⎞2/3⎟⎝w⎠ ⎜1+12.7⋅⎜8⎟ ⋅(Pr −1)⎟ ⎝⎝⎠⎠ Re ⎝D⎠ Transition zone (i.e. Recrit < Re < 22 000) – linear interpolation: (6.24) NuTR =γ⋅NuL(atRe=Recrit)+(1−γ)⋅NuT(atRe=22000) (6.25) where: (6.26) The subscripts L and T refer to laminar and turbulent flow, respectively. γ=⎛⎜ 22000−Re ⎞⎟ ⎝22000−Recrit ⎠ 178PDF Image | Residential CO2 Heat Pump System for Combined
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CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
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