Effect of Polyolester Oil-based Multiwalled Carbon-Nanotube Lubricant on the Coefficient of Performance of Refrigeration Systems

Abstract This paper presents experimental and theoretical findings on the effect of polyolester oil-based multiwalled carbon nanotube nanolubricant on both the heat dissipation in the evaporator and the power consumption of the compressor of a refrigerator. The nanolubricant containing multiwalled carbon nanotube with 0.1 weight % Triton X-100 surfactant was manufactured using a two-step method. The pressure in the test cell containing R134a and the nanolubricant was measured for different exposure times to observe the behavior of the suction pressure in the compressor chamber containing the nanolubricant. Based on the results, a model for predicting the suction pressure behavior was established. The developed model was applied, and it was found that the power consumption of the compressor containing the nanolubricant could be reduced by up to 17%. In addition, the modified flow boiling heat transfer coefficient of the evaporator considering the nanolubricant was theoretically derived using a property model of the nanolubricant. The modified model showed that the flow boiling heat transfer coefficient of the evaporator containing the nanolubricant could be improved by approximately 5.8%. Finally, the enhancement in the coefficient of performance of the refrigerator containing R134a and the nanolubricant was analyzed using the results for the power consumption of the compressor and the flow boiling heat transfer coefficient of the nanolubricant in the evaporator.