ASSESSMENT OF HIGH TEMPERATURE HEAT PUMP LAYOUTS EQUIPPED WITH A BLADELESS TURBOEXPANDER

Efficient and resilient reverse cycles at MW-scale are needed in industry and energy communities for pursuing the ambitious targets of electrification of industrial processes and thermal generation via renewable power. This work evaluates the optimal thermodynamic performance features of heat pump cycles comparing conventional layouts with those adopting a Tesla turboexpander, for recovering pressure drop in high temperature applications. The paper focuses on n-pentane (R601), a natural refrigerant, being a favorable substitute of synthetic refrigerants thanks to its low global warming potential (GWP) and adequate thermophysical properties that could allow to reach high temperature thermal outputs (>150°C), thus, being suitable for some specific industrial processes. Tesla or bladeless turboexpanders are a promising technology for small volumetric flows and two-phase fluids, featuring low sensitivity to downscaling effects, while retaining high rotor efficiency, which is being investigated for energy-harvesting solutions. The benefit of introducing such expansion device in place of a conventional lamination valve is assessed, in different layout configurations. Simulations were conducted using an improved version of WTEMP-EVO modeling tool, proprietary to University of Genoa. Results show that the use of Tesla expander improves significantly the overall thermal efficiency in terms of coefficient of performance (COP), thanks to power recovered, depending on the cycle layout.