Experimental evaluation of split air conditioning performance using nanodiamonds particles in compressor polyester lubricant oil

Rationing energy consumption in air conditioning (AC) systems has become increasingly necessary due to the continuous global increase in energy demand and the prevailing sustainability vision worldwide. Therefore, an AC system utilizing nanodiamond/Polyester (ND/POE) lubricant oil, which shows potential to improve the performance and reduce energy consumption, was investigated. Consequently, a 5-ton refrigeration split AC unit was modified with an oil separator to assess the ND/POE nanolubricant in the compressor's loop, in particularly. The AC unit was examined under various operating conditions up to an extreme high ambient temperature of 52C, with an optimal nanolubricant concentration of 0.1% as recommended from the literature, using a fully automated psychrometric testing facility. The results showed that using ND/POE instead of pure POE resulted in a 4.7% and 3% reduction in compressor discharge temperature and pressure, respectively. Furthermore, the overall system's coefficient of performance (COP) improved by up to 8% due to a reduction in power consumption of up to 3% and an increase in cooling capacity of up to 6%. Therefore, it is anticipated that the use of ND/POE will result in improved compressor durability, reliability, and longevity, as well as a significant improvement in the performance of AC systems operating for prolonged periods, such as those operating in extreme high ambient temperature applications.