An experimental system for Vertical Tube Evaporator(VTE) was designed and manufactured to study the heat and mass transfer with flash evaporation phenomenon inside the tube.
Experiments were performed with the several flow patterns inside the tube and at these conditions temperature distribution and evaporation rate inside the tube, and condensation rate outside the tube were measured and compared. Average heat transfer coefficients (overall, inside and outside the tube) were calculated and compared.
It was observed that the flow pattern inside the tube changed from single phase flow to the two phase flow according to the decrease of pressure inside the tube. Nonequilibrium effect condition inside the tube on the heat transfer appeared to be dominant compared with heating the tube by condensing the steam condensation. When the tube inside pressure increases, overall and tube inside heat transfer coefficients decrease. Whereas, tube outside heat transfer coefficient increases. A brief calculation using Chen's boiling heat transfer correlation appears to be useful for predicting the two phase flow heat transfer coefficient inside the tube with allowable accuracy.