Heat pipe flat plate solar collectors operating with nanofluids

The aim of this work is to characterize numerically the performance of a heat pipe flat plate solar collector operating with nanofluids. A mathematical formulation under a 1-dimensional transient heat transfer model was introduced for this purpose. Spatio-temporal temperature variation of each collector subelement was predicted for a typical sunny day in the Moroccan city, Fez. CuO, Al2O3 and TiO2-based nanofluids were compared energetically and exergetically under various operating modes. The nanoparticle loading and mass flow rate of the working fluid were varied in the range of 0-3% and 0.018-0.036 kg/s, respectively. For the flow regime under focus, the decreased specific heat of nanofluids is the main thermal property responsible for the perfor-mance enhancement when nanofluids are used. CuO-based nanofluid was found to engender the highest relative enhancements in the energetic and exergetic efficiencies which were estimated at 2.7% and 11.1%, respectively compared to the base fluid (water). Using nanofluids for this collector class can ensure up to 2.95% surplus daily thermal energy generation compared to the base fluid. Moreover, the use of CuO-based nanofluid caused the largest increase in the pressure drop across the collector with a maximum value of 13.26% predicted for 3% nanoparticle loading.

Automated summary

This study aims to characterize the performance of a heat pipe flat plate solar collector using different nanofluids, with CuO-based nanofluid showing the highest enhancements in energetic and exergetic efficiencies. The decrease in specific heat of nanofluids is identified as the main thermal property responsible for performance improvement.