Laminar Flow Heat Transfer of a Pseudoplastic Fluid through a Double Pipe Heat Exchanger
Volume 3, Issue 2, Spring 2006, Pages 13-19
M. Moradi, S. Gh. Etemad, A. Moheb
Abstract An experimental study was carried out to obtain the mean convective heat transfer coefficient of aqueous carboximethyl cellulose (CMC) solutions in double-pipe heat exchangers. Co-current and counter- flows were considered in the investigation. From the experimental data a Nusselt number was calculated for a wide range of Graetz number, Reynolds number, and CMC concentrations. Increasing the Graetz and Reynolds numbers promote the heat transfer and variation of CMC concentration has a noticeable effect on the Nusselt number.
A New Model for Prediction of Heat Eddy Diffusivity in Pipe Expansion Turbulent Flows
Volume 2, Issue 1, Winter 2005, Pages 24-33
A.R. Mohammadi, G. Heidarinejad, K. Mazaheri
Abstract A new model to calculate heat eddy diffusivity in separating and reattaching flows based on modification of constant Prt is proposed. This modification is made using an empirical correlation between maximum Nusselt number and entrance Reynolds number. The model includes both the simplicity of Prt=0.9 assumption and the accuracy of two-equation heat-transfer models. Furthermore, an appropriate low Reynolds number k — e model is adopted for calculation of eddy viscosity. The model is used for prediction of Nusselt number distribution at various ranges of Reynolds number and expansion ratio. The numerical results are compared with available experimental data in the literature and have shown good agreement. The CPU time for the present model is about 33% less than that of two-equation heat-transfer model.