This document presents an experimental investigation of a pipe-in-pipe tube heat exchanger using silica (SiO2) nanofluid. The heat exchanger consists of an outer steel pipe and inner aluminum pipe. SiO2 nanofluid with 2% volume concentration and 100nm nanoparticle size is used and compared to water as the base fluid. Test results show that the nanofluid improves heat transfer characteristics and heat transfer coefficient compared to water. Specifically, the effectiveness of the heat exchanger increased by 23.1% when using nanofluid versus water. Varying the mass flow rate was also found to impact the heat transfer rate and effectiveness.