|Researchers||Refrigerant||Nanoparticle||Lubricant||Particle size (nm)||Main finding|
|Bobbo et al. (2010) ||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) ||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) ||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) ||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) ||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) ||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) ||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) ||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) ||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) ||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) ||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) ||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) ||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.