Table 1 The influence of nanofluid on different solar thermal applications

Luo et al. [8]

DAC solar collector

use of nanofluid in the solar collector can improve the outlet temperature and the efficiency

Rahman et al. [9]

triangular shape solar collector

Results showed 24.28% improvement for Gr=10⁶ at 10% volume fraction of copper particles. the convective heat transfer performance is better when the solid volume fraction is kept at 0.05 or 0.08.

Faizal et al. [10]

solar collector

results confirmed that higher density and lower specific heat of nanofluids offers higher thermal efficiency than water and therefore can reduce the solar collector area about 25.6%, 21.6%, 22.1% and 21.5% for CuO, SiO2, TiO2 and Al2O3 nanofluids. Environmental damage cost is also lower with the nanofluid based solar collector

Parvin et al. [11]

solar collector

Increasing the particles concentration raises the fluid viscosity and decreases the Reynolds number and consequently decreases heat transfer. There is a need to find the optimum volume fraction for each application

Ladjevardi et al. [12]

solar collector

Their numerical results showed that nanofluid collector thermal efficiency increases about 88% compared with the pure water collector with the inlet temperature of 313 K. It also can be increased to 227% with the inlet temperature of 333 K.

Said et al. [15]

flat plate solar collector

It was observed that SWCNTs nanofluids could reduce the entropy generation by 4.34% and enhance the heat transfer coefficient by 15.33%

Saidur et al. [17]

direct absorption solar collector

Their results revealed that Aluminum/water nanofluid with 1% volume fraction improves the solar absorption considerably. They found that the effect of particle size on the optical properties of nanofluid is minimal, but in order to have Rayleigh scattering the size of nanoparticles should be less than 20 nm. They also found that the extinction coefficient is linearly proportionate to volume fraction

Sokhansefat et al. [18]

parabolic trough collector tube

Nanofluid enhanced convective heat transfer coefficient.

Hordy et al. [21]

solar collector

quantitative demonstration of the high temperature and long-term stability of ethylene glycol and propylene glycol-based MWCNT nanofluids for solar thermal collectors

Said et al. [22]

Solar collector

Their results showed that nanofluids pressure drop at a low concentration flowing in a solar collector is slightly higher than the base fluid.

Liu et al. [23]

solar collectors

They observed 15.2%-22.9% enhancement in thermal conductivity using 0.06% volume graphene in the temperature range from 25 to 200°C. Their results showed that GE is a better nanoadditive for nanofluids than other carbon materials and metal nanoparticles

Ho et al. [24]

concentrating solar power systems

The addition of less than 2% Al₂O₃ nanoparticles significantly increases the specific heat of Hitec metal at low temperatures

Singh et al. [25]

They stated that surfactant selection has an important role in preparing stable nanofluids. Choosing the right surfactant is mainly dependent on the properties of the base fluids and particles

Yousefi et al. [29]

flat plate solar collector

They found that increasing or decreasing the pH with respect to the pH of the isoelectric point (IEP) would enhance the positive effect of nanofluids on the efficiency of the solar collector

Sardarabadi et al. [30]

PV/T

Thermal efficiency of the PV/T collector for the two cases of 1 and 3 wt% of silica/water nanofluid increased 7.6% and 12.8%, respectively.

Kabeel et al. [32]

water desalination unit

the water cost can be decreased from 16.43 to 11.68 $/m³ at ϕ=5%

Kabeel et al. [33]

solar still

using nanofluids improves the solar still water productivity by about 116% and 76% with and without operating the vacuum fan

Al-Nimr et al. [34]

shallow solar pond

energy stored in the nanofluid pond is about 216% more than the energy stored in the brine pond

Liu et al. [35]

maximum and mean values of the collecting efficiency of the collector with open thermosyphon using nanofluids increased 6.6% and 12.4%, respectively.