Rheological and heat transfer characterizations of non-Newtonian fluid falling film in evaporation process

Abstract

A set of experimental equipment was established for falling film evaporation. The aqueous CMC (carboxymethylcellulo) solution was used to simulate the non-Newtonian fluid that obeys the power law model. Effects of rheology of the non-Newtonian fluid on heat transfer were investigated experimentally. A theoretical model was developed and coupling characteristics between rheology and heat transfer were described in non-Newtonian environmental fluid falling film in evaporation process. The different theoretical models were established for the developing region and the fully developed region in this evaporation process, respectively. Using finite difference method and shooting method, the simulated calculations were obtained. Furthermore, by introducing the generalized Reynolds number and the Prandtl number, which includes the necessary physical properties of the non-Newtonian fluid, a correlation about the Nusselt number was proposed for non-Newtonian fluid falling film in evaporation process.

Keywords

non-Newtonian fluid / rheology / heat transfer / falling film evaporation

References

[1] KohJ. C. Y., SparrowE. M., HartnettJ. P.. The two-phase boundary layer in laminar film condensation[J]. Int J Heat Mass Transfer, 1961, 2(1/2): 69-82

[2] IncroperaF. P., DeWittD. P.Fundamentals of heat and mass transfer[M], 1996, New York, John Wiley & Sons: 556-560

[3] AssadM. E. H., LampinenM. J.. Mathematical modeling of falling liquid film evaporation process[J]. International Journal of Refrigeration, 2002, 25(7): 985-991

[4] KimH. B., TadiniC. C., SinghR. K.. Heat transfer in a plate exchanger during pasteurization of orange juice[J]. Journal of Food Engineering, 1999, 42(2): 79-84

[5] PachecoC. R. F., FrioniL. S. M.. Experimental results for evaporation of sucrose solution using a climbing/falling film plate evaporator[J]. Journal of Food Engineering, 2004, 64(4): 471-480

[6] DelplaceF., LeulietJ. C.. Modelling fouling of a plate heat exchanger with different flow arrangements by whey protein solutions[J]. Food and Bioproducts Processing, 1995, 73: 112-120

[7] CebeciT., BradshawP.Momentum transfer in boundary layer[M], 1977, Washington D C, Hemisphere: 62-69