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hi = Q=Ui ⋅Ai ⋅LMTD Ui & ⎛U⋅A⋅ln(d/d)⎞ ⎛U⋅A⎞ 1−⎜ i i o i ⎟−⎜ i i ⎟ ⎝ 2⋅π⋅k⋅L ⎠ ⎝Ao ⋅ho ⎠ (5.1) (5.2) 5 – Experimental Results Eqs. 6.21 through 6.26 in Section 6.1.3.3, Heat Transfer Correlations, the mean convective heat transfer coefficient for the brine-side ho was esti- mated using the Gnielinski correlation for single-phase flow (VDI, 1993). Hence, by rearranging Eq. 6.10 in Section 6.1.3.2, Energy Equations, the mean heat transfer coefficient hi for the CO2 was calculated as follows: Figure 5.45 displays the estimated mean heat transfer coefficient for the flow boiling CO2 as a function of the inlet vapour fraction at varying heat flux. The evaporation temperature was -5oC ±0.1oC, the CO2 mass flux was 470 kg/(m2s) ±2% whereas the calculated mean overall heat transfer coefficient ranged from about 1600 to 2100 W/(m2K). 4000 3000 2000 1000 0.0 0.1 0.2 0.3 0.4 0.5 Inlet Vapour Fraction [-] 13- 11- 11- 10- 15 kW/m2 15 kW/m2 13 kW/m2 12 kW/m2 Figure 5.45 The estimated mean heat transfer coefficient (U-value) for the flow boiling CO2 at -5°C evaporation temperature and varying inlet vapour fraction and heat flux. The estimated mean heat transfer coefficient for the CO2 ranged from about 2500 to 4000 W/(m2K) at inlet vapour fractions between 0.01 and 0.44. Bredesen et al. (1997) measured local heat transfer coefficients and pressure drop for flow boiling pure CO2 in an ID 7 mm round tube at varying evaporation temperature, mass flux and heat flux (ref. Appendix 151 hCO2 [W/m2K]PDF 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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