This study investigates the thermal performance of a heat pipe heat recovery system in air-to-air heat recovery systems using a nanofluid of Al2O3 (aluminum oxide) particles and distilled water. The experimental setup used 15 wickless vacuumed copper pipes with a length of 1000 mm, a 10.5 mm inner diameter and a 12 mm outer diameter. The evaporator section consists of 450 mm of heat pipes, the condenser section is 400 mm, and the adiabatic section is 150 mm. In experimental studies, 33% of the evaporator volume of the heat pipes was filled with working fluids. Experiments were carried out at temperatures between 25 degrees C and 90 degrees C by using five different cooling air flows (40 g/s, 42 g/s, 45 g/s, 61 g/s and 84 g/s), and two different heating powers (3 kW and 6 kW) for the evaporation section, to determine the heat removed from the condensation section. Experiments were performed for distilled water and Al2O3 nanofluid, respectively, and the results were compared with each other. As a result of the experiments, it was observed that using a nanofluid as the working fluid increased the efficiency of the heat pipe. The highest efficiency (eta = 59%) was obtained in the experiments carried out using an Al2O3 nanofluid at a heating power of 3 kW and an air flow of 112 g/s.