Flow boiling performance in smooth and internally-grooved tube U-bend cold plates

This paper outlines evaporative flow boiling results in custom smooth and internally-grooved tube cold plates with U-bends. Heat transfer data, captured with an infrared camera, is analyzed for liquid-vapor HFE-7100 flow in horizontal 9mm channel diameter cold plates, with mass fluxes from 75-250 kg/m
²
s, heat fluxes from 0-18 kW/m
²
, and vapor qualities approaching unity. This data is compared to a recently developed internally-grooved tube diabatic flow regime map and associated heat transfer coefficient correlation by Sharar and Bar-Cohen. The internally-grooved tube model is shown to predict the current data set satisfactorily, however, the traditional Wojtan et al. smooth tube model has limited applicability at low mass flux due to flow regime transition after the U-bends.