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