A comprehensive numerical study of energy efficiency analysis of a double pipe gas cooler based on second law analysis

A numerical simulation of energy efficiency in commercially available double pipe heat exchangers in the market was investigated based on the Second law of thermodynamics in this paper. The effects of CO2 mass-flow rate, water mass-flow rate, pressure, CO2 inlet temperature, and water inlet temperature of the double pipe heat exchanger were considered to evaluate the energy efficiency by analyzing entropy generation, exergy destruction, and entransy dissipation. The changes of the entropy generation, the changes of exergy destruction, and entransy dissipation are similar regardless of the operating conditions. Pressure has the most significant effect on the energy efficiency of the double pipe gas cooler compared to other operating conditions but negligible on the exergy destruction. The pressure, flow rate, and inlet temperature have completely different effects on energy efficiency depending on the region. The entropy generation and entransy dissipation at y = 0 m to y = 0.05 m (y-axis is the radial direction) decrease with increasing pressure and the opposite after that. The increase of CO2 inlet temperature at y < 0.5 m is accompanied by an increase of entropy generation, exergy destruction, and entransy dissipation but this situation disappears after y - 0.5 m. Entropy generation, exergy destruction, and CO2 and water mass-flow rate are first negatively and then positively correlated with the cut-off point at y = 0.1 m.