Pressure Drop Calculation at Flow Boiling in a Minichannel for a Wide Range of Reduced Pressures

Abstract

This paper studies the validity of prediction tools for two-phase flow pressure drops in wide range of reduced pressures based on the comparison between new experimental results and theoretical results predicted with the commonly used methods. The original dataset was obtained in a vertical uniformly heated minichannel 1.1 mm inner diameter with R125 and RC318 as working fluids. Uniform heating was carried out by electric current, simulating real flow conditions in heat exchangers, which is a distinctive feature of this work from most similar studies. The mass velocity varied in the range from 200 to 1400 kg/(m²s), the reduced pressure varied from 0.132 to 0.70, the heat flux density range was from 4 to 322 kW/m², the inlet vapor quality was set from −0.2 to −0.06 and outlet vapor quality reached 1 at minimum flow rates. The database is composed of 115 data points of two-phase flow boiling and was compared against well-known two-phase pressure drop prediction methods. The effect of the reduced pressure on the ability of the methods to predict the pressure drop was pointed out.