Evaporation Heat Transfer and Pressure Drop Characteristics of R32 Inside a Multiport Tube with Microfins

Abstract

This study investigated the evaporation heat transfer and pressure drop characteristics of R32 in a horizontal multiport tube consisting of rectangular minichannels with straight microfins. The heat transfer coefficient and pressure drop were measured for a mass velocity range of 50–400[Formula: see text]kgm[Formula: see text]s[Formula: see text] and heat flux range of 5–20[Formula: see text]kWm[Formula: see text] at a saturation temperature of 15[Formula: see text]C. The frictional pressure drop during an adiabatic two-phase flow was also measured for a mass velocity range of 50–400[Formula: see text]kgm[Formula: see text]s[Formula: see text] and quality range of 0.1–0.9 at the same saturation temperature. The heat transfer coefficient increased with an increasing quality owing to the increase in forced convection. The dryout inception quality increased with the increase in mass velocity. The effects of heat flux on the heat transfer coefficient were small, except in a high-quality region. The heat transfer coefficient in a multiport tube with microfins was higher than that in a multiport tube without microfins in a high-quality region at a mass velocity of 200[Formula: see text]kgm[Formula: see text]s[Formula: see text] and in a low-quality region at a mass velocity of 400[Formula: see text]kgm[Formula: see text]s[Formula: see text]. The effects of mass velocity and microfins on the frictional pressure drop were clarified. It is suspected that the effects of a microfin on the frictional pressured drop can be considered using the hydraulic diameter. The frictional pressure drop was shown to be in good agreement with previous correlations.