Performance of TiO₂ Nanolubricants on Air Infiltration Induced by Door Openings in a Domestic Refrigerator

¹ PhD Scholar, Faculty of Engineering & the Built Environment, University of Johannesburg, South Africa
² The Energy and Environment Research Group (TEERG), Mechanical Engineering Department, Covenant University, Ogun State, Nigeria
³ Faculty of Engineering & the Built Environment, University of Johannesburg, South Africa
⁴ Institute for Intelligent Systems, University of Johannesburg, South Africa

^* Corresponding Author: damola.adelekan@covenantuniversity.edu.ng: +2347035249346

Abstract

This study examines the performance of TiO₂ nanolubricant at concentrations of 0, 0.2, and 0.4 g/L in a slightly modified refrigeration system, tested with door openings of 30, 60, 120, 180, 240, and 300 seconds. The system was charged with 30 g of either LPG or R600a refrigerant, combined with the specified TiO₂ concentrations. Monitoring involved a digital pressure gauge, K-type thermocouples, and a wattmeter to assess energy behaviour under closed and open-door conditions. Key performance metrics included closed-door pull-down time, open-door air infiltration heat rate and load, power consumption, compressor power, and recovery rate. All tests complied with ISO 8187, achieving a minimum evaporator air temperature of -3°C within one hour of continuous operation. For both R600a and LPG refrigerants, air infiltration heat rate and load decreased from 0.02162 m³/s and 2.4365 kW at 30 seconds to 0.02085 m³/s and 0.602 kW for door openings of 60 to 300 seconds. Conversely, recovery rate, energy consumption, and compressor power increased with longer door openings. Adding TiO₂ nanolubricant reduced recovery rate by 1.08%65.8% for R600a and 2.12% - 85% for LPG, compressor power by 4.14%43.01% for R600a and 5.92% -30.92% for LPG, and energy consumption by 13.33% - 66.67% for R600a and 5.88% - 80% for LPG. Overall, TiO₂ nanolubricants substantially mitigated the impact of air infiltration into the evaporator cabinet.