Heat transfer coefficients 238: fractionator problems

Heat transfer coefficients (HTCs) between melt and water fields are provided via a boiling curve, which describes nucleate, transition, and film boiling. (In the present problem, only the film boiling regime occurs.) At high vapor volume fractions, a transition is made between film boiling heat transfer to water and convective heat transfer to vapor from the melt. 

We now consider the quantitative treatment of this problem. For simplicity we will consider the case of a plane channel in which the feed temperature Ti is greater than the ambient temperature Ta, and we will neglect viscous dissipation. The starting point is then Equation 4.11 without the qdp/dx term. We write the wall heat transfer rate from the melt to ambient as U Tcm - Ta), this definition of the heat transfer coefficient suffices to illustrate the point that we wish to make, and the results would be essentially the same if we followed the procedure used for the extruder and set the wall temperature to a fixed fraction of Tcm- There are two walls in the channel, so Equation 4.10 then becomes... 

Fractionation efficiency, 6,11,195-196, 209, 365 fractionator problems, 195-196, 209 Fractionator problems (FCCU product fractionation), 18f3-200 flooding, 188-189 load observation, 189-191 liquid loading sensitivity, 189 capacity comparison, 189,192-193 heattransfer coefficients, 193-194 structured packing heat transfer, 193 height equivalent to theoretical stage,... 

The heat power PE will only partially be transferred to the machined substrate (i.e., P0 = ePE)- The fraction of the heat flux transmitted to the substrate will depend on, besides the geometry of the problem, the ratio of the coefficients of thermal conductivity of the electrolyte (typically around 0.6 W m 1 K1 for NaOH) and the substrate. Another important parameter is the heat conductivity of the tool-electrode. As the tool-electrode has the highest heat conductivity, most part of the heat is evacuated through it. 

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