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Table 2 Summary of related studies on TiO2 nanoparticle-based nano-refrigerants

From: Toward TiO2 Nanofluids—Part 2: Applications and Challenges

Researchers Refrigerant Nanoparticle Lubricant Particle size (nm) Main finding
Bobbo et al. (2010) [94] R134a TiO2 (0.5 g/L) POE (SW32) 21 (a) Adding TiO2 nanoparticles in SW32 oil showed the best performance as compared with the pure SW32 and single-wall carbon nano-horns/SW32 oil mixtures.
Mahbubul et al. (2011) [101] R123 TiO2 (0.5 to 2 vol.%) 21 (a) The pressure drop increased with the increase of the particle volume fractions and vapor quality as well as the decrease of temperature.
Trisaksri and Wongwises (2009) [99] R141b TiO2 (0.01 to 0.05 vol.%) 21 (a) Nucleate pool boiling heat transfer performance was deteriorated with the increase of particle loading, especially at high heat fluxes.
Bi et al. (2007) [95] R134a TiO2 (10 mg/L) Mineral oil 50 (a) Using nano-refrigerant could reduce the energy consumption of the system by 7.43%.
Bi et al. (2008) [96] R134a TiO2 (0.1 wt.%) Mineral oil 50 (a) Adding 0.1 wt.% TiO2 nanoparticles can reduce 26.1% less energy consumption and particle type has little effect.
Bi et al. (2011) [97] R600a TiO2 (0.5 g/L) 50 (a) TiO2-R600a nano-refrigerant could work in the refrigerator normally and safely.
(b) The refrigerator performance was better and 9.6% energy saved with 0.5 g/L TiO2-R600a nano-refrigerant.
Sabareesh et al. (2012) [100] R12 TiO2 (0.01 vol.%) Mineral oil 30/40 (a) An optimum volume fraction of 0.01% was found, at which the average heat transfer rate was increased by 3.6%, average compressor work was reduced by 11%, and COP was increased by 17%.
Padmanabhan and Palanisamy (2012) [98] R134a, R436A, R436B TiO2 (0.1 g/L) Mineral oil (a) TiO2 nanoparticles worked normally and safely with the three kinds of refrigerants/lubricant.
(b) TiO2 nanoparticles can reduce the irreversibility of VCRS. Refrigerant R436A and R436B with MO + TiO2 as a lubricant obtained the best performance.
Javadi and Saidur (2015) [103] R134a TiO2 (0.1 wt.%) Mineral oil (a) Adding 0.1% of TiO2 nanoparticles to mineral oil-R134a resulted in the maximum energy savings of 25%.
(b) An emission reduction of more than 7 million tons of Coz= by year of 2030 can be obtained in Malaysia.
Li et al. (2015) [102] R22 TiO2 (5 wt.%) (a) Adding TiO2 nanoparticle decreased COP of the cooling cycle slightly but increased COP of the heating cycle significantly due to the power consumptions of compression.
Chang and Wang (2016) [13] R141b TiO2 (0.0001% to 0.01 vol.%) 50–70 (a) The lowest concentration (0.0001%) TiO2 nano-refrigerant achieved the best performance (increased by 30%) with ultrasonic vibration.
Tazarv et al. (2016) [14] R141b TiO2 (0.01 and 0.03%) 30 (a) Convective heat transfer coefficient was greatly improved by adding TiO2 nanoparticles.
(b) Low mass flux leads to a significant enhancement in heat transfer coefficient of TiO2 nano-refrigerant owing to the nanoparticle deposition.
Lin et al. (2017) [15] R141b   NM56 60 (a) The suspending ratio of nanolubricant–refrigerant declined with the running time.
(b) Lower particle loading, lower heating, or cooling temperature can reduce the degradation speed.