Abstract
Emerging nanotechnology with solar collector technology has attracted the attention of researchers to enhance the performance of solar systems in order to develop efficient solar thermal systems for future sustainability. This paper chronologically reviews the various research works carried out on the performance enhancement of nanofluid-filled flat-plate solar collectors (FPCs). Gaps in the radiation exergy models and maximum exergy of FPCs, the importance of pressure drops in collector manifolds in exergy analysis, and the economics of nanofluid-laden FPCs have been addressed. The necessity of replacing currently used chemically derived glycol products with a renewable-based glycol has not been reported in the current literature thoroughly, but it is pondered in the current paper. Moreover, the thermophysical properties of all common metal and metal oxide nanoparticles utilized in various studies are collected in this paper for the first time and can be referred to quickly as a data source for future studies. The different classical empirical correlations for the estimation of specific heat, density, conductivity, and viscosity of reported nanofluids and base liquids, i.e., water and its mixture with glycols, are also tabulated as a quick reference. Brief insights on different performance criteria and the utilized models of heat transfer, energy efficiency, exergy efficiency, and economic calculation of nanofluid-based FPCs are extracted. Most importantly, a summary of the current progress in the field of nanofluid-charged FPCs is presented appropriately within two tables. The tables contain the status of the main parameters in different research works. Finally, gaps in the literature are addressed and mitigation approaches are suggested for the future sustainability of nanofluid-laden FPCs.
Highlights
Flat-plate solar collectors (FPCs) are regarded as a good alternative to meet the thermal energy demand from the domestic and industrial sectors
Solar thermal collectors convert the radiation coming from the sun into thermal energy for heating an heat transfer fluid (HTF), which is an effective solution for conservation of energy
A detailed literature review on nanofluid application in solar FPCs is presented above. Different nanomaterials and their thermophysical properties, the existing classical and empirical models for evaluation of thermophysical properties and heat transfer coefficient, various used base liquids and nanofluids at different sizes and concentrations, and the main achievements of almost all investigations for nanofluid-based FPCs are included in this review
Summary
Flat-plate solar collectors (FPCs) are regarded as a good alternative to meet the thermal energy demand from the domestic and industrial sectors. Thermal performance enhancement of solar FPCs is progressing either by advancing the absorber plate or improving the heat transfer fluid (HTF) effectiveness. Both methods deal with energy and exergy efficiency of the collector. As the second method of efficiency improvement, the addition of nanomaterials to the HTF is a result of relatively recent progress This approach enhances the conductivity of the collector’s HTF and boosts the heat transfer coefficient and thermal efficiency. The Carnot and Petela–Landsberg–Press (PLP) models are well-known equations that have long been used to calculate the exergy of solar radiation Their application is rigorously restricted to cases where the conversion of radiation energy into work is performed by using blackbody collectors, not selective absorbers. Future research directions are drawn from the existing gaps
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