Numerical simulation of flow boiling heat transfer of ammonia in a horizontal stainless-steel tube

A three-dimensional multiphase CFD model has been developed based on the VOF method to analyze flow boiling heat transfer characteristics of ammonia in a smooth horizontal tube of 3.0 mm internal diameter and 200.0 mm length. The simulations have been performed for the following margins of commonly used operating parameters: saturation temperature (-10 to 10 °C), wall heat flux (10–40 kW/m²) and mass flux (50–200 kg/m²s). The numerical outcomes have been successfully validated with the experimental measurements of Zhang et al. (2022) [1]. Results show that the heat transfer coefficient increases as the vapor quality is raised until a maximum, then sharply drops. It is also observed that the heat transfer coefficient is more sensitive to the mass flux than the wall heat flux.