Optimizing the performance of solar collectors and photovoltaic thermal systems that are used for heating/cooling of building as well as electricity generation will efficiently help to approach zero-energy buildings. For this purpose, improving the efficiency of heat exchangers as the main part of solar collectors and photovoltaic thermal systems is necessary. In this paper, two passive methods are employed to ameliorate the efficiency of heat exchangers. To do this, the effect of using Al2O3/water nanofluid in a heat exchanger tube with a swirling flow turbulator was studied. A numerical simulation was carried out to obtain thermal–hydraulic performance in the tube with eccentric helical screw-tape turbulators. The influences of different parameters including nanoparticles volume fraction and eccentricity of tube insert on the performance of heat exchanger are investigated. The results reveal that the coefficient of heat transfer enhances approximately 4.5 times by using nanofluid at nanoparticles volume fraction of 4% with helical turbulator compared to the plain tube at nanoparticles volume fraction of 0%. It was also found that the value of Performance Evaluation Criterion ameliorates as the nanoparticle loading increases. The maximum value of Performance Evaluation Criterion reached 2.2 at nanoparticles volume fraction of 4%, Reynolds number of 4000 and eccentricity of 3. The results of this study reveal the potential of the suggested technique to enhance various thermal systems including solar collectors.

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