Numerical Investigation on Heat Transfer and Performance Number of Nanofluid Flow inside a Double Pipe Heat Exchanger Filled with Porous Media

Two common methods to augment heat transfer are the application of nanofluids and porous inserts. In the present work, heat transfer inside a double tube heat exchanger filled with porous media is analyzed numerically using two phase mixture model for the nanofluid flow and the Darcy-Brinkman-Forchheimer model for the flow inside porous media. Basically, porous media improve heat transfer at the expense of increasing pressure drop. A new PN (Performance number) -defined as the ratio of heat transfer to pressure drop on the base state (without porous media and nanoparticles)- is introduced to better judge the first law’s performance of configurations. Results indicated that by keeping Dai=Dao=0.1 and increasing Reynolds number from 500 to 2000, an increase of 56.09% was observed in the performance number. Furthermore, maintaining Reynolds number at Re=500 and changing Dai=Dao from 0.0001 to 0.1, results in an increase of 138%. For pressure drop, by keeping Dai=Dao=0.1 and increasing Reynolds number from 500 to 2000, it is 40 times. Furthermore, maintaining Reynolds number at Re=500 and changing Dai=Dao from 0. 1 to 0.0001, the pressure drop is 250 times. Besides, adding 3% nano particles to the base fluid enhances the performance number by about 50% and increase pressure drop by about 20%.