Effect of Gravity during Condensation of R134a in a Rectangular Minichannel

In order to study the effect of gravity on the condensation of R134a in a horizontal single square minichannel with 1mm side length, a Volume of Fluid (VOF) method is adopted to simulate the condensation process. The influence of gravity, surface tension and gas-liquid interfacial shear stress are taken into account. The Continuum Surface Force model is chosen for surface tension. Results denote that the lowest velocity and temperature appears at the corner of channel, where condensation occurs first. The distribution shape of the steam in the cross section of the channel is approximately circular and the condensation increases along the flow direction. In square minichannel, the effect of gravity on condensation can be neglected and the condensation is dominated by surface tension and gas-liquid interfacial shear stress at low and high inlet mass velocity respectively. The influence of gravity in condensation film is unobvious when the minichannel is short. In long minichannel, the condensation accumulates in the bottom of channel because of gravity which is not benefit for condensation heat transfer.