Optimal analysis of gas cooler and intercooler for two-stage CO2 trans-critical refrigeration system

• Simplified model for tube-fin gas cooler for CO2 refrigeration system was presented and validated.
• Several parameters were investigated using 1st law and 2nd law in component and system level.
• Practical guidelines of optimum for tube-fin gas cooler and intercooler were proposed.

Energy-based 1st law and exergy-based 2nd law are both employed in the paper to assess the optimal design of gas cooler and intercooler for two-stage CO2 refrigeration system. A simplified mathematical model of the air-cooled coil is presented and validated against experimental data with good accuracy. The optimum circuit length under the influence of frontal air velocity and deep rows is investigated first. Thereafter, designed coil with optimum circuit length is further evaluated within the two-stage refrigeration system. It is found out the optimum point using 1st law does not coincide with the point using 2nd law in isolated component and the simulation results from isolated component by 2nd law are closer to system analysis. Results show optimum circuit length is much bigger for gas cooler than intercooler and the influence on the length from variation of frontal air velocity and deep rows may be neglected. There does exist optimum frontal air velocity which will decrease with more number of deep rows.