Experimental research on degradation of nanolubricant–refrigerant mixture during continuous alternation processes of condensation and evaporation

Nanolubricant–refrigerant mixture used in vapor-compressor refrigeration system undergoes continuous alternation processes of condensation and evaporation, during which it degrades gradually as a result of the nanoparticle deposition. This paper quantitatively evaluates the degradation of nanolubricant–refrigerant mixture during continuous alternation processes of condensation and evaporation, and investigates the effects of lubricant mass fraction, nanoparticle mass fraction, heating condition, and cooling condition on degradation. TiO 2 /NM56/R141b is chosen as the nanolubricant–refrigerant mixture for experiments. The experimental conditions cover lubricant mass fraction of 5–20%, nanoparticle mass fraction of 0.2–1.0%, heating temperature of 50–80 o C, and cooling temperature of 5–15 o C. The experimental results show that nanolubricant–refrigerant mixture degrades by 28–77% after 20 alternation times under present experimental conditions; besides, the degradation in long-term period can be reduced at conditions of higher lubricant mass fraction, lower nanoparticle mass fraction, lower heating temperature, or lower cooling temperature.