Implementing Roughness Profiles to Control the Temperature Profile Within a Gas-Cooler

Gas coolers and heat exchangers are essential components in many modern systems, directly influencing overall efficiency by transferring thermal energy between fluids. Recently, supercritical carbon dioxide (sCO2) has gained significant attention as a working fluid due to its enhanced heat-transfer capabilities, compactness, and economic advantages, all rooted in its distinct thermodynamic property variations. Near the pseudocritical temperature, however, these systems can experience a “pinching” effect, where the temperature difference between the hot and cold fluids decreases, limiting heat transfer and often necessitating larger heat exchangers that diminish system performance. Surface roughness is another key factor affecting operation: although it can enhance heat transfer, it also increases pressure drop and alters the system’s thermal behavior. While increased relative roughness is known to promote turbulence and improve convective heat transfer in subcritical flows, its influence on supercritical fluids remains uncertain due to their dramatic property variations. This work investigates how different roughness profiles can modify heat transfer within an sCO2 gas cooler and reshape the temperature distribution with the goal of maintaining a more uniform temperature difference between the sCO2 and water along the heat-exchanger length. The results show that varying roughness profiles can influence the Nusselt number and alter the thermal behavior of the system; however, the adjustments are not sufficient to achieve a constant temperature difference throughout the exchanger. These findings highlight the complexity of roughness effects in supercritical flows and suggest that additional design strategies are necessary to achieve a constant temperature difference between sCO2 and water.