This paper investigates NH3 condensation in a plate heat exchanger by visualizing the flow patterns and measuring heat transfer coefficients and frictional pressure drop. Visualization experiments were conducted between 20 and 100 kgm−2s−1. Full film flow takes place at large mass fluxes and intermediate mass fluxes of low vapor qualities, while partial film flow occurs at small mass fluxes and intermediate mass fluxes at high vapor qualities. The heat transfer and frictional pressure drop experiments cover the mass fluxes of 21~78 kgm−2s−1, the averaged vapor qualities of 0.05~0.65 and the saturated pressure of 630 to 930 kPa. Vapor qualities have significant influences on heat transfer and frictional pressure drop. In the tested ranges, the effect of mass fluxes is noticeable on frictional pressure drop, but is moderate on heat transfer. The impact of saturated pressure is small. The heat transfer reflects the change of flow patterns. The frictional pressure drop shows the characteristics of separated flow.@en

The heat transfer coefficients (HTCs) of NH3 are higher than of HFCs and hydrocarbons during the condensation within plate heat exchangers (PHEs) mainly due to its favorable transport properties. NH3/H2O has a large temperature glide, and its heat transfer is dependent on mass transfer. Few models have been specifically developed for NH3 and NH3/H2O condensation in PHEs. This paper presents heat transfer and pressure drop experiments for partial condensation. The calculation method for condensation HTCs and frictional pressure drop is introduced. The working fluids are pure NH3 and NH3/H2O with a weight concentration of 96%. For a mass flux of 62 kgm-2s-1, the HTCs of NH3 increase from 10 to 20 kWm-2K-1 with vapor quality. The apparent HTCs of NH3/H2O are significantly lower than NH3 at high vapor qualities because of mass transfer resistance. Condensation pressure level has a slight influence on HTCs and frictional pressure drop.@en