Performance of nanofluid-cooled shell and tube gas cooler in transcritical CO2 refrigeration systems

The theoretical performance analyses of the nanofluid cooled shell-and-tube gas cooler in transcritical CO2 refrigeration cycle have been done to study the performance improvement of gas cooler as well as CO2 cycle using Al2O3, TiO2, CuO and Cu nanofluids and effects of various design and operating parameters. Use of nanofluid as coolant in shell-and-tube gas cooler of CO2 cycle improves the gas cooler effectiveness, cooling capacity and COP without penalty of pumping power. The CO2 cycle yields best performance using Al2O3–H2O as coolant in shell-and-tube gas cooler followed by TiO2–H2O, CuO–H2O and Cu–H2O. The maximum cooling COP improvement of transcritical CO2 cycle for Al2O3–H2O is 26.0%, whereas that for TiO2–H2O is 24.4%, for CuO–H2O is 20.7% and for Cu–H2O is 16.5% for the given ranges of study. Study shows that the nanofluid may effectively use as coolant in shell-and-tube gas cooler to improve the performance of transcritical CO2 refrigeration cycle.