Performance evaluation of evacuated tube solar collector using boron nitride nanofluid

Abstract

Nanofluids are the most fascinating and efficient approach to strengthen the thermal performance of a heat exchanger device. Herein, this contemporary experimental investigation exhibited the impact of water based hexagonal Boron Nitride nanofluid (hBN/water) on the thermal performance of a U-tube evacuated tube solar collector. The hBN nanoparticles of 50 nm size are dispersed and ultrasonicated in distilled water to obtain hBN/water nanofluid of varying volumetric concentrations (0.25, 0.50, 0.75, 1, 1.25, 1.50, 1.75, and 2 vol%). For stability improvement of nanofluid, six different surfactants (i.e. TWEEN20, SPAN20, SDS, SDBS, CTAB, and TTAB) are mixed with nanofluid at a different mixture ratio (i.e. 4:2, 3:2, 2:3, and 1:4) and zeta potential test was performed to inspect the stability of the mixture. The thermophysical properties (i.e. thermal conductivity, viscosity, and specific heat) of hBN/water nanofluid were analyzed at above volumetric concentration and varying temperature ranges (i.e. 25, 30, 35, 40, 45, and 50 °C). The collector’s thermal performance is analysed at varying mass flow rates (0.0085, 0.01667, 0.0255, 0.034, 0.0425 and 0.051 kg/s) and obtained the maximum energy efficiency (72.14 % at 1.5 vol% and 0.051 kg/s), which is approximately 84 % higher than water at the same flow conditions.