Thermal performance improvement in the solar air collector system using reduced graphene oxide nanoparticles

Abstract

This study experimentally demonstrates that enhancing solar absorptance and heat transfer in a single-pass solar air collector can be achieved through a coating of reduced graphene oxide-doped black paint. The introduction of carbon-based nanoparticles results in an augmented thermal conductivity in a turpentine-oil nanofluid. Subsequently, a homogeneous blend of the thermally modified turpentine oil with the black paint is coated onto the absorber plate, resulting in a consequent increase in absorptance across the incident solar spectrum. In this regard, two different solar air collectors were fabricated, namely (i) a single-pass flat plate SAC with BP coating and (ii) a single-pass flat plate SAC with rGO-doped BP coating as surface coating. The thermal performance of both solar air collectors was evaluated across a range of airflow rates. Data obtained during the experiments demonstrated that the collector with the surface coating exhibited superior thermal response: specifically, higher absorber temperatures, increased exit air temperatures, and an improved temperature difference between the exit and inlet air streams. However, the increase in the flow rate of air through the rectangular channel decreases the absorber, exit air temperature, and temperature difference between the exit and inlet of the rectangular channel. Furthermore, the results also showed that at the higher flow rate of air through the channel, the Nusselt number and the heat transfer coefficient increase from coated and uncoated absorber plates. From the experimental results, the average daily efficiency of the single-pass SAC with BP coating ranged from 30.12 to 67.2% for a flow rate of 0.01 to 0.03 kg s−1. However, with surface coating and improved surface roughness, the daily efficiency increased to 34.6 to 79.5%. Furthermore, in this study, a response surface methodology is employed to optimize the exit, absorber temperature, and the change in temperature between exit and inlet, considering the impact of solar radiation, ambient temperature, and concentration of nanoparticles. Moreover, the correlations are expressed in the form of a quadratic function.