Numerical investigation of nanofluid flow and heat transfer in a pillow plate heat exchanger using a two-phase model: Effects of the shape of the welding points used in the pillow plate

In this study, a numerical investigation of fluid flow and heat transfer of Al(2)O(3-)water nanofluids in a pillow plate heat exchanger with a two-phase model is investigated. The flow regime studied in this study is in the laminar flow regime such that the Reynolds numbers are 250, 500, 750, and 1000 and the volume fraction of the nanoparticles remained so that the fluid stayed in Newtonian. The volume fraction of nanoparticles is phi= 0, 1, 2, and 3 %. In this study, the effect of the shape of the welding points used in the pillow plate has also been investigated in such a way that three modes of circular welding point, large-diameter elliptic welding point along with the flow and large-diameter elliptic welding point perpendicular to the stream have been investigated. Numerical simulation results show that using nanofluid and increasing Reynolds number improves heat transfer, as well as circular welding point, shows the best heat transfer rate. The shape of the welding points has a direct relationship with the pressure drop and heat transfer, as well as the wake created behind the welding points, which have the highest wake and pressure drop respectively for the elliptic welding points perpendicular to the flow, circular and elliptical parallel to the flow. On the other hand, the addition of nanoparticles increases the friction factor and, on the contrary, increases the Reynolds number, which reduces the friction factor. Finally, the highest Reynolds number, the highest volume fraction of nanoparticles, and the circular welding point state show the highest PEC.