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H,in C,out H,out C,in (6.9) (T −T ) LMTD = In Eq. (6.6), which describes the energy balance in the each sub-section of the gas cooler unit, the subscript i refers to the inside of the CO2 tube whereas LMTD is the logarithmic mean temperature difference between the supercritical CO2 and the water. The overall heat transfer coefficient Ui [W/(m2K)] for each sub-section is expressed as follows when referring to the inner heat transfer surface Ai: 6 – Modelling (T −T )−(T −T ) ln H,in C,out (T −T ) H,out C,in Ui = 1 (6.10) ⎛1⎞ ⎛A⋅ln(d/d)⎞ ⎛1 A⎞ ⎜⎟+⎜i oi⎟+⎜⋅i⎟ ⎜h⎟ 2⋅π⋅k⋅L ⎜h A ⎟ ⎝i⎠⎝ ⎠⎝o o⎠ where L is the length of the sub-section, h is the convective heat transfer coefficient, and k is the thermal conductivity of the CO2 tube. The subscripts i and o refer to the inside and outside surface of the CO2 tube, respectively. Since the modelled tube-in-tube heat exchanger was made of smooth cylindrical tubes, the overall heat transfer coefficient per unit length of the tube U* [W/(mK)] was expressed as (Kreith, 1980): (6.11) (6.12) U* = 1 ⎛ 1 ⎞⎛ln(d/d)⎞⎛ 1 ⎞ ⎜ ⎟+⎜ o i ⎟+⎜ ⎟ ⎝hi ⋅π⋅di ⎠ ⎝ 2⋅π⋅k ⎠ ⎝ho ⋅π⋅do ⎠ Consequently, an alternative form of Eq. (6.10) was used: &* Q=U ⋅L⋅LMTD With reference to Eqs. (6.4) through (6.6), the energy balance for each sub-section was expressed as: &&& QH = QC = Qtot (6.13) 175PDF 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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