What would be the best way to handle cases where apparent viscosities as a function of shear rate may need to be given in the input. How would the shear rates be estimated for the liquid film at the top of the tube and the bottom of the tube? If this can be done, a linear interpolation for the apparent viscosity in each zone could be done. Is there software suitable for the evaporation of Non-Newtonian (pseudoplastic or shear thinning) fluids in the tube side of falling film heat exchangers?
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Jim Grant Forum Moderator 118 Posts
Re: Shear rates for liquid film16 January 2007 at 1:29pmI would recommend approaching this in an incremental fashion if the shear rate varies substantially along the length of the tube. At each increment of tube length, calculate the shear rate to provide a viscosity value and perform the heat transfer calculations for that increment. If the shear rate is fairly constant, then using the apparent viscosity as input to a program like HTRI Xchanger Suite would be recommended this must be known as a function of temperature, but should be adequate.