Numerical Dimensioning of a Pre-Cooler for sCO2 Power Cycles to Utilize Industrial Waste Heat

The annual waste heat available from industry in the European Union is more than 2700 PJ. Consequently, the utilization of the unexploited thermal energy will decisively contribute to a reduced overall power consumption and lower greenhouse gas emissions. In the present investigation, a cycle layout, based on supercritical carbon dioxide (sCO2), was applied for a certain waste heat source, a gas compressor station. The boundary conditions determined by the cycle were used by the numerical code ANSYS CFX to design a pre-cooler. Subsequently, this printed circuit heat exchanger was examined for sCO2 mass fluxes between 100 kg/m²s and 900 kg/m²s. The heat transfer and pressure drop increase as the flow channel diameter is reduced. As the pressure drop of the coolant channel is more sensitive to the diameter, a larger coolant channel diameter is selected to maintain a reasonably low pressure drop. The optimum pre-cooler design consists of a 0.5 mm and 0.8 mm channel diameter for the sCO2 and coolant channel. Based on these results, internal fins were applied and optimized, to improve the heat transfer performance. An internal fin height of 4 mm was found to achieve the optimum thermal-flow performance for the pre-cooler.

Flow analysis in seamless hot-extruded pipes with helical inner ribbing surface

The article is devoted to numerical simulation of heat transfer processes occurring during the flow of a coolant in seamless hot-extrusion pipes with a spiral inner fin surface (TMK-IRS). A description of the numerical modeling technique is given along with the interface of the program used to create different types of internal fins. Thermohydraulic analysis of finned pipes for transient, turbulent and laminar flow regimes has been carried out. An estimate of the critical Reynolds number characterizing the transition to a turbulent regime, the nature of the transient flow regime in comparison with other classical cases is given.