Effect of mono/hybrid nanofluids and passive techniques on thermal performance of parabolic trough solar collector: A review

ABSTRACT

Solar energy is one of the most effective and environmentally beneficial forms. Numerous advancements, like solar collectors, have been created to harness sun-powered energy; however, the parabolic trough solar collector (PTSC) is the best collector because of its wide variety of commercial uses and thermal necessities at moderate and high temperatures. However, extracting the maximum thermal energy from PTSC remains one of the most challenging tasks. Thus, various methodologies such as using nanofluids (NFs) as working fluids (WFs), receiver tube material, and turbulent promotors in receiver tubes of PTSC are being investigated to boost its proficiency. This article’s goal is to analyze the role of mono and hybrid NF flowing with different turbulent promotors in rising PTSC performance and compares the Nusselt number (Nu) and thermal efficiency (${\eta }_{\mathrm{t}\mathrm{h}}$) of various PTSC with varying performance parameters like Reynolds number ($Re$), mass flow rate, and inlet temperature (${\mathrm{T}}_{\mathrm{i}\mathrm{n}}$) of working fluid that has significant consequences on the outcome of PTSC. Among different NFs and turbulence promotors, the $\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3$/MWCNT hybrid NF and converging-diverging receiver tube inside PTSC provide the best thermal improvement of 69% and 79%, respectively. Among the various receiver tube materials, Pyrex glass has the highest, ${\eta }_{\mathrm{t}\mathrm{h}}$ of 197.1%. Similarly, the combination of inserts and NFs provides the best thermal performance in terms of their use.

KEYWORDS:

• Solar energy
• thermal performance
• nanofluids
• turbulence promoters
• heat transfer
• PTSC

Nomenclature

Symbols	=
$ff$	=	Friction factor
$\text{dotm}$	=	Mass flow rate, (Kg/s)
Nu	=	Nusselt number
$Re$	=	Reynolds number
SWCNT	=	Silver-walled carbon nanotube
${\mathrm{T}}_{\mathrm{i}\mathrm{n}}$	=	Inlet temp+ erature, (K)
Greek symbols	=
$\varphi$	=	Concentration, (%)
${\eta }_{en}$	=	Energy efficiency, (%)
$\epsilon$	=	Epsilon
${\eta }_{\mathrm{e}\mathrm{x}}$	=	Exergy efficiency, (%)
$\omega$	=	Omega
${\eta }_{\mathrm{t}\mathrm{h}}$	=	Thermal efficiency, (%)
Abbreviations	=
BF	=	Base fluid
CFD	=	Computational fluid dynamics
HTC	=	Heat transfer coefficient
NF	=	Nanofluid
NP	=	Nanoparticle
PTSC	=	Parabolic trough solar collector
WF	=	Working fluid

Disclosure statement

No potential conflict of interest was reported by the authors.