Air-to-air heat pipe heat exchangers are passive heat transfer units specifically employed in heating, ventilation, and air-conditioning systems for heat recovery. Nanofluids have extensively been favored in recent years to improve the thermal performance of fluid-driven heat transfer devices because of their contribution to thermophysical properties. The binary or more hybrid combination of nanoparticles also becomes the focus of interest of the researchers to obtain more improvement rates. In this study, aluminate-based spinets of Fe, Mg, and Zn elements with the binary combinations of Fe:Mg, Fe:Zn, and Zn:Mg were used and aqueous hybrid nanofluids were prepared considering a combination ratio of 50:50. These were then used as the working fluid in the heat pipes of the air-to-air heat exchanger that operates between hot and cold air passages. The efficiency and thermal resistance of the heat pipes were investigated under varying Reynolds number combinations of hot and cold air passages. The increments up to 85.8% in efficiency, and decrements up to 67.6% in thermal resistance of the heat pipe were recorded with the usage of aluminate spinel-based nanofluid in place of distilled water. As far as cold air velocities were considered, the experimental results demonstrated that (FeAl2O4 + MgAl2O4)/distilled water binary hybrid nanofluid had the lowest improvement rates which fluctuated between 6.3% and 10.4%, though the maximum enhancement ratios which changed between 45.3% and 63.1%were reported for (FeAl2O4 + ZnAl2O4)/distilled water binary hybrid nanofluid.