Feasibility of pressure drop reduction and heat transfer augmentation with pseudo-plastic fluids in an isosceles triangular pipe

Abstract.

Prediction of heat transfer and pressure drops in flow passages is very essential to heat exchanger and commercial conduit design. It is necessary to know the relation between viscous properties of the fluid and wall shear rate in the conduit. This is done by assuming a constitutive equation which relates local apparent viscosity of fluid to the local shear rate. This research deals with the limits of validity of the power law equation. The useful methodology of the present research involves a consideration of a more general equation which has power law and Newtonian behavior as asymptotes. Use of the power law equation outside of its applicability range can lead to serious errors in predicting the heat transfer and pressure drops. Present computational results of the Nusselt numbers and the friction factors times Reynolds number for pseudo-plastic fluid flows in an isosceles triangular conduit are compared with previous published results, showing agreement with 1.59% in the Newtonian region and 2.85% in the power law region. These pseudo-plastic fluid results also showed the 12% increase of convective heat transfer and 65% reduction of pressure drop at the power law region compared with pressure drop and heat transfer with Newtonian fluid, respectively.