Energy efficiency becomes one of the most attracting study areas in the world because of the rising environmental issues. It is widely known that a plenty of energy efficiency applications are performed in heat transfer devices. In this regard, it is aimed to improve the thermal performance of recuperator, an air-air heat exchanger, including heat pipe bundle by utilizing a nanofluid, which is the mixture of nanoparticles of a metal oxide and deionized water, by this experimental study. The tests were conducted by filling the heat pipe at the rate of 1/3 of heat pipe volume both deionized water and alumina nanofluid, respectively. Coolant air was used to determine how much heat could be extracted from the condenser section. The findings obtained from the tests show that thermal performance of a heat pipe bundle-including recuperator was remarkably enhanced when nanoparticles containing working fluid was used as the working fluid in place of deionized water. The maximum improvement was achieved as 37.04% during the tests conducted at 6 kW heater power.