Mixed convective heat transfer of Titania-Water nanofluid in a circular heat exchanger with rotational hot and cold pipes

The mixed convective heat transfer of Titania-Water nanofluid in a circular heat exchanger containing internal rotational hot and cold cylinders is investigated numerically using two phase mixture model. Hot and cold cylinders inside the heat exchanger which is filled with Titania-Water nanofluid, is maintained at constant temperature of Th and Tc , respectively, while other parts are thermally insulated. Two dimensional equations of Navier-Stokes,energy and volume fraction are solved using finite volume method and SIMPLE algorithm. The effects of various parameters such as Richardson number, volume fraction of nanoparticle and rotation direction of heater and cooler on the fluid flow and heat transfer rate are evaluated. Results illustrate that under the condition that internal cylinders rotate in the same direction, heat transfer rate increases as compared to those that they rotate in anopposite direction. Hence rotation direction of cylinders can be used as a desire parameter for controlling heat transfer rate. Moreover, the good agreement of present achievements with previously reported results demonstrates that the developed model can be used with great confidence to study the flow and heat transfer of nanofluid in various problems. Besides, the thermal characteristics of present nanofluid are found to be too higher in comparison to the base fluid

Keywords:

Heat Exchanger , Two Phase Mixture Model , Rotational Circular Cooler/Heater , Volume Fraction of Nanoparticle