Abstract
The effects of lubricant oil on flow boiling heat transfer of low GWP refrigerant R 1234yf in small-diameter tubes with inner diameter of 2 and 4 mm were experimentally investigated. Local heat transfer coefficient measurement, flow pattern observation and pressure drop measurement were conducted to clarify the change in heat transfer performance and flow pattern at different vapor quality, mass flux, heat flux and oil mass fraction conditions. Experimental results showed that with increasing oil mass fraction, the local heat transfer coefficient increased at lower vapor quality due to intensified foaming phenomena. However, the heat transfer coefficient decreases monotonically with oil mass fraction in high quality region. The forming phenomena at different mass flux and heat flux were illustrated by the visual observation.
