A study on optimising heat pipe geometrical parameters for sustainable passive cooling within the built environment

The way in which heat pipes are arranged plays an important role on the overall effectiveness of this sustainable thermal system. A numerical and experimental analysis into determining the optimum heat pipe streamwise distance for providing passive airside cooling in ventilation airstreams was carried out. The airflow and temperature profiles were numerically predicted using Computational Fluid Dynamics (CFD), the findings of which were quantitatively validated using wind tunnel experimentation. Using the heat pipe diameter (D) of 20 mm, the spanwise thicknesses were varied from 44 mm (St/D ratio of 2.2) to 52 mm (St/D ratio of 2.6). In order to ensure sustainable operation of the system, water was used as the heat pipe working fluid. Keeping the boundary conditions constant for all modes (inlet velocity of 2.3 m/s and inlet temperature of 314K), the rate of heat transfer was found to be directly proportional to the temperature difference between inlet and outlet interface. The findings determined that the spanwise thickness of 50 mm (St/D ratio of 2.5) provided the highest heat transfer in comparison to the other analysed models at 768 W. The overall effectiveness of the system was found to decrease from 5.6% to 4.7% when the spanwise thickness reduced from 50 mm to 44 mm. A good agreement was obtained between the numerical and experimental findings with a maximum error of 1.6% for temperature and 14.6% for velocity parameters. The investigation successfully evaluated the performance of heat pipes under varying geometrical arrangement, when utilised for the purpose of pre-cooling ventilation airstreams for a sustainable built environment.