Most fluids used in the chemical, pharmaceutical, food, and biomedical industries can be classified as non-Newtonian, ie, the viscosity varies with shear rate at a given temperature. In contrast, Newtonian fluids such as water, air, and glycerin have constant viscosities at a given temperature. Examples of non-Newtonian fluids include molten polymer, aqueous polymer solutions, scurries, coal-water mixture, tomato ketchup, soup, mayonnaise, purees, suspension of small particles, blood, etc. Because non-Newtonian fluids are nonlinear in nature, these are seldom amenable to analysis by classical mathematical techniques. The optimum design of process equipment which handles non-Newtonian fluids could be significantly improved once predictive capability were increased. However, the basic understanding of the fluid mechanical and heat-transfer behavior of non-Newtonian, ie, viscous and viscoelastic, fluids is limited (22).
A better understanding of pressure drop and heat-transfer behavior of non-Newtonian flows applicable to typical heat-exchanger geometries should lead to the design and development of more energy-efficient processes and to better quality control of the final products. In general, the viscosity of a non-Newtonian fluid can be significantly larger than that of water. Therefore, the selection of a pump size to provide enough flow rate and subsequently to ensure adequate heat removal or supply is necessary. A significant heat-transfer enhancement can be obtained when a noncircular tube is used together with a non-Newtonian fluid.
newspaper measuring cups 1 cup of dry cornstarch large bowl or pan food coloring (if you want) 1/2 cup of water Put newspaper down on your counter or tabletop. Put the cornstarch into the bowl. Add a drop or two of food coloring. (Use whatever colors you like. ) Add water slowly, mixing the cornstarch and water with your fingers until all the ...
This heat-transfer enhancement is attributed to both the secondary flow at the corner of the noncircular tube (23, 24) and to the temperature-dependent non-Newtonian viscosity (25).
Using an aqueous solution of polyacrylamide the laminar heat transfer can be increased by about 300% in a rectangular duct over the value of water (23).
A knowledge of the viscous and thermal properties of non-Newtonian fluids is essential before the results of the analyses can be used for practical design purposes. Because of the nonlinear nature, the prediction of these properties from kinetic theories is as of this writing in its infancy. For the purpose of design and performance calculations, physical properties of non-Newtonian fluids must be measured. 5.
7. Micro-Heat Exchangers A better understanding of transport phenomena in micro channel heat exchangers appears to be vital to the development of some advanced microelectronic devices. In future designs, heat-exchanger passages are expected to be incorporated into silicon substrates for the purpose of cooling substrate-mounted microelectronic chips. The passage dimensions could be made as small (.